JP2004138649A - Scanning optical system and image forming apparatus using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a scanning optical system, which can print with high quality at a high speed while reducing an eclipse and image plane curvature due to influence of eccentricity of a stop and a collimation optical means of the scanning optical system, and an image forming apparatus using the same. <P>SOLUTION: The scanning optical system, which has a 1st optical means 2 for imaging luminous flux projected by a light source means 1, a luminous flux limiting means 3 for limiting the luminous flux, a 2nd optical means 5 for converging the luminous flux into a desired converged state, a deflecting means 7 including a deflection surface deflecting the luminous flux, and a 3rd optical means 8 for guiding the luminous flux onto a scanned surface so that the luminous flux limiting means and the deflecting surface of the deflecting means are conjugate or nearly conjugate across the 2nd optical means, has an adjusting means 4 for adjusting the position relation of at least a portion of a member provided in an optical path from the light source means to the scanned surface. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a scanning optical system and an image forming apparatus using the same, and in particular, deflects and reflects a light beam (laser light) emitted from a light source means by a polygon mirror as an optical deflector, and scans the light beam on a surface to be scanned via the scanning optical means. This is suitable for an image forming apparatus such as a laser beam printer having an electrophotographic process, a digital copying machine, a multi-function printer (multi-function printer), or the like, in which image information is recorded by optical scanning.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a scanning optical system used in an image forming apparatus guides a light flux emitted from a light source (light emitting unit) as a light source means to a deflecting means via an incident optical means having a collimator lens, a cylindrical lens (cylinder lens) and the like. The light beam deflected and reflected by the deflecting means is focused on the surface to be scanned through a scanning optical means and is optically scanned.
[0003]
In recent years, as the performance and function of the image forming apparatus have been improved, the demand for a higher-speed scanning optical system has been increased. Therefore, it is conceivable to use a plurality of light sources in order to respond to the demand for high speed. For example, a multi-beam laser chip that emits a plurality of light beams aligned in a straight line from one chip is used as the light source (for example, see Patent Reference 1).
[0004]
Regardless of whether the above-described multi-beam laser chip is used as a light source or a case where a plurality of independent light sources are used, when scanning the surface to be scanned using a common deflecting unit and scanning optical unit regardless of the light emitting unit, each light emission If the luminous flux emitted from the unit is shifted in the main scanning direction on the deflecting surface of the deflecting unit, the position of the dot corresponding to each light emitting unit may be shifted.
[0005]
FIG. 24 is an optical path diagram showing an optical path of a light beam emitted from each of the light emitting units (light sources) 91a and 91b, and shows a principal ray of the light beam at a timing of forming an image at the center of an image on the surface to be scanned 99.
[0006]
As can be seen from the figure, the positions at which the scanning optical means 98 transmits and refracts (reflects when a mirror is used) are different from each other. Although not shown in the figure to avoid complicating the figure, the actual angle of the deflecting surface 97a is slightly different for each light beam.
[0007]
For this reason, the scanned surface 99 is decentered in the optical axis direction, or the refractive power of the scanning optical unit 98 is not as designed, and the image forming position is relatively shifted from the scanned surface 99 in the optical axis direction. If the position is shifted, the position where the surface to be scanned 99 is irradiated is shifted in the main scanning direction from the original position.
[0008]
FIG. 25 is an explanatory diagram of the dot position shift, in which each light beam (light beam indicated by a broken line in the figure) formed on the surface to be scanned is out of focus (right side in the figure) on the surface to be scanned. (A luminous flux shown by a solid line).
[0009]
As described above, since the position at which the light is transmitted and refracted through the scanning optical means is different for each light beam, the angle of incidence of each light beam on the surface to be scanned is different. For this reason, when the focus position is relatively shifted with respect to the surface to be scanned, the irradiation position of each light beam is separated by an amount shown as a dot position shift in the figure.
[0010]
Regarding the interval between scanning lines, in a scanning optical system in which the light beam emitted from each light emitting unit is shifted on the deflection surface in the main scanning direction, the optical elements constituting the scanning optical system are deviated from their original positions. If they are in mind, the intervals may be different from the original scanning line intervals (hereinafter, referred to as “pitch interval errors”).
[0011]
As an example, FIG. 26 is an explanatory diagram of a pitch interval error, showing a state before and after the scanning optical unit (lens) is decentered in the sub-scanning direction. A light beam before decentering is indicated by a dotted line, and a light beam after decentering is indicated by a solid line. I'm drawing.
[0012]
When the radius of curvature of the sagittal wire differs depending on the location, the influence of the eccentricity differs, so that a pitch interval error occurs as shown in FIG. Even when the curvature radius of the sagittal wire is constant regardless of the location and the magnification is not constant, a pitch interval error similarly occurs.
[0013]
As one method of reducing these phenomena, there is a method in which the conjugate point of the stop (light beam limiting means) is present on the deflection surface, and the light beam is not shifted in the main scanning direction on the deflection surface. is there.
[0014]
However, when a conjugate point with the deflecting surface with respect to the main scanning section is obtained via the collimating optical means (second optical means), the conjugate point is located behind the light source (in a direction away from the deflecting surface). In the case of using the light source, it is necessary to rearrange the light source after the stop, and to form an image of the light beam emitted from the light source at the original position of the light source by using the relay optical means (first optical means).
[0015]
The scanning optical system thus configured can make the positions of the light beams from the respective light emitting units coincide with each other in the main scanning direction on the deflection surface regardless of the position of the light emitting unit. For this reason, even if the number of light-emitting portions increases and the distance between the ends of the light-emitting portions increases, the deterioration of the print quality due to the deviation of the light beam on the deflection surface is negligible.
[Patent Document 1]
JP-A-9-54263
[0016]
[Problems to be solved by the invention]
By the way, in the scanning optical system having the relay optical means as described above, if the positions of the diaphragm and the collimating optical means are shifted, the position of the deflecting point of the light beam emitted from the collimating optical means on the deflecting means is shifted from the original position. Shift.
[0017]
FIG. 27 is an explanatory view of the deviation of the deflection point position. FIG. 27 schematically shows a state in which a light beam emitted from the light source 91 is incident on the deflection surface 97a. 3 shows a light beam when decentered.
[0018]
In the figure, the luminous flux passes through the outside of the lens because the diaphragm 93 is extremely decentered. This is because an extreme state is shown in order to make the figure easier to understand. When decentered, the light beam is kicked by a lens or the like. In the scanning optical system under consideration, the stop 93 and the deflecting surface 97a are in a substantially conjugate relationship via the collimating optical means 92 as described above, so that the stop 93 is indicated by a two-dot broken line in FIG. There is a deflection point on a straight line connecting the light and the collimating optical means 95. Therefore, the position of the deflecting point, which is the conjugate point of the stop 93, is also eccentric according to the eccentricity of the stop 93 and the collimating optical means 95.
[0019]
In such a case, the light beam deflected and reflected by the deflecting means is shifted from its original position. Therefore, when each light beam deflected and reflected by the deflecting unit is transmitted and refracted through the optical element constituting the scanning optical unit, each light beam enters a position different from the original position, and thus field curvature may occur.
[0020]
In addition, a rotating polygon mirror (optical deflector) that is as small as possible is often used for the deflecting means in consideration of the rotational speed, cost, and the like. Therefore, even when the light beam is incident on only a part of the deflecting surface when scanning a certain portion of the effective scanning area (printing area), after the entire effective scanning area is scanned, the light beam is incident on the deflecting surface. Generally covers almost the entire area. Therefore, if the position of the deflecting point deviates from the original position, not only does the curvature of field occur as described above, but also a part of the light beam cannot enter the deflecting surface, which may cause uneven density in the printing result. is there.
[0021]
In order to reduce these phenomena, there is a method of adjusting the position of the collimating optical means and the stop in the direction perpendicular to the optical axis. A method for adjusting the position of the collimating optical means is conventionally known in a scanning optical system having no relay optical means. However, the conventional adjusting method mainly adjusts the emission direction of a light beam emitted from the collimating optical means. The position of the luminous flux after the emission was not particularly considered. This is because the position of the emitted light beam after the adjustment appears to be almost the same as the eccentricity of the stop, and is only about 50 μm at most even considering the mounting accuracy of the light beam emitting unit (relay unit) that integrates the unit from the light source to the collimating optical means. It does not slip. At this time, depending on the scanning optical means, the curvature of field occurs only about ± 0.4 mm.
[0022]
On the other hand, in the scanning optical system having the relay optical means, when the stop is decentered, there is a problem that the position of the deflecting point cannot be displaced by several times the stop because of the configuration.
[0023]
The present invention reduces the curvature of field and vignetting on the deflecting surface (a phenomenon that a part of the light beam cannot be transmitted or reflected) due to the incident position of the light beam on the deflecting device deviating from a predetermined incident position, and achieves high speed. It is an object of the present invention to provide a scanning optical system capable of performing high-quality printing at high speed and an image forming apparatus using the same.
[0024]
[Means for Solving the Problems]
(1-1) The scanning optical system of the present invention includes:
Light source means, first optical means for forming an image of the light beam emitted from the light source means, light beam limiting means for restricting the light beam from the first optical means, and the light beam formed by the first optical means. A second optical unit for bringing the light beam passing through the restricting unit into a desired condensed state, a deflecting unit including a deflecting surface for deflecting the light beam guided from the second optical unit, and a light beam deflected by the deflecting unit A third optical means for guiding the light onto the surface to be scanned, and the light beam restricting means and the deflecting surface of the deflecting means are in a conjugate or substantially conjugate relationship via the second optical means. In a scanning optical system that optically scans the surface to be scanned by rotating the deflecting means,
It is characterized by having adjusting means for adjusting a positional relationship of at least a part of a member provided in an optical path from the light source means to the surface to be scanned.
[0025]
In addition,
(1-1-1) When the distance from the light beam restricting unit to the second optical unit is L1, and the distance from the second optical unit to the deflecting surface is L2.
L2 / L1 ≦ 4
It is characterized by satisfying certain conditions.
[0026]
(1-1-2) The adjusting unit is configured to adjust a position of a member provided in an optical path from the light source unit to the deflecting unit such that an incident position of the light beam on the deflecting unit substantially coincides with a predetermined incident position. The feature is that the relationship is adjusted.
[0027]
(1-1-3) The adjusting unit is configured to control the light source unit so that a part or all of the light flux does not protrude from the deflecting surface of the deflecting unit during optical scanning of the effective scanning range of the surface to be scanned. It is characterized in that the positional relationship of the members provided in the optical path from to the deflecting means is adjusted.
[0028]
(1-1-4) The adjustment means adjusts the positional relationship of at least some of the optical elements so as to reduce the curvature of field on the surface to be scanned.
[0029]
(1-1-5) The adjusting unit is configured to determine a light amount of a light beam outside the effective scanning area on the surface to be scanned and a light amount of the light beam existing across a light beam group that scans the effective scanning region when viewed from the light beam. It is characterized in that the incident position of the light beam on the deflecting means is adjusted so that the light amount of the light beam outside the effective scanning area, which should be the same light amount, is equal.
[0030]
(1-1-6) The adjusting means has a structure capable of adjusting a relative positional relationship between the second optical means and the light beam restricting means in a direction perpendicular to the optical axis of the first optical means. It is characterized by having.
[0031]
(1-1-7) It is characterized by having a holding means which holds the second optical means and is formed integrally with the light beam limiting means.
[0032]
(1-1-8) The adjustment means has a structure in which one or both of the position and the orientation of the second optical means can be adjusted.
[0033]
(1-1-9) Each member from the light source means to the second optical means is housed in one unit member, and the unit member is detachably attached to a housing member on which the deflecting means and the like are mounted. It is characterized by being worn.
[0034]
(1-1-10) The adjustment means has a structure in which one or both of the position and the orientation of the unit member can be adjusted.
[0035]
(1-1-11) The adjustment means has a mirror, and adjusts the angle of the mirror.
[0036]
(1-2) a light source means, a first optical means for forming an image of a light beam emitted from the light source means, a light beam restricting means for restricting a light beam from the first optical means, A second optical unit for forming a light beam which is imaged and passed through the light beam restricting unit into a desired condensing state, a deflecting unit including a deflecting surface for deflecting the light beam guided from the second optical unit, and the deflecting unit And a third optical means for guiding the light beam deflected by the light beam onto the surface to be scanned. The light beam restricting means and the deflecting surface of the deflecting means are conjugated or substantially conjugated via the second optical means. In a scanning optical system that optically scans the surface to be scanned by rotation of the deflecting means,
When the distance from the light beam limiting means to the second optical means is L1, and the distance from the second optical means to the deflection surface is L2,
L2 / L1 ≦ 4
It is characterized by satisfying certain conditions.
[0037]
(1-2-1) The adjusting means has a structure capable of adjusting a relative positional relationship between the second optical means and the light beam restricting means in a direction perpendicular to the optical axis of the first optical means. It is characterized by having.
[0038]
(1-2-2) The adjustment means is characterized in that one or both of the position and the orientation of the second optical means can be adjusted.
[0039]
(1-2-3) The deflecting unit is mounted on a housing member, and the housing member has an optical path secured so that the light amount of a light beam incident outside the effective scanning area on the surface to be scanned can be measured. It is characterized by:
[0040]
(1-2-4) A plurality of optical paths for measuring the light amount of the light beam are provided.
[0041]
(1-2-5) It is characterized in that two or more light paths for the light quantity measurement are secured with a light beam group for scanning the effective scanning area of the scanned surface separated.
[0042]
(1-2-6) It is characterized by having a light amount measuring means for measuring the light amount of the light beam outside the effective scanning area of the surface to be scanned.
[0043]
(1-2-7) The light quantity measuring means also serves as a synchronization detecting means for measuring a writing start timing on the surface to be scanned.
[0044]
(1-2-8) It is characterized by having a plurality of the light quantity measuring means.
[0045]
(1-2-9) The apparatus is characterized in that two light quantity measuring means are provided so as to separate a light flux group for scanning an effective scanning area of the scanned surface.
[0046]
(1-2-10) The light source unit has a plurality of light emitting units.
[0047]
The image forming apparatus of the present invention includes:
(2-1) The scanning optical system of the constitution (1-1) or (1-2), the photosensitive member arranged on the surface to be scanned, and the photosensitive member on the photosensitive member by a light beam scanned by the scanning optical system. A developing device that develops the electrostatic latent image formed on the toner image as a toner image, a transfer device that transfers the developed toner image to a transfer material, and a fixing device that fixes the transferred toner image to the transfer material. It is characterized by having.
[0048]
(2-2) A scanning optical system having the configuration (1-1) or (1-2), and a printer controller for converting code data input from an external device into an image signal and inputting the image signal to the scanning optical system. It is characterized by having.
[0049]
The color image forming apparatus of the present invention includes:
(3-1) A plurality of image carriers each of which is arranged on the surface to be scanned of the scanning optical system of the configuration (1-1) or (1-2) and forms images of different colors. Features.
[0050]
In addition,
(3-1-1) It is characterized by having a printer controller that converts color signals input from an external device into image data of different colors and inputs the image data to each scanning optical system.
[0051]
BEST MODE FOR CARRYING OUT THE INVENTION
First, technical means for achieving the object of the present invention will be described.
[0052]
Now, the distance from the stop (light flux limiting means) to the front principal plane of the collimating optical means (second optical means) is L1, the air conversion distance from the rear principal plane of the collimating optical means to the deflection surface is L2, Assuming that the amount of eccentricity is X, the stop position and the deflection point on the deflection surface are in a conjugate relationship, so the displacement amount P at the deflection point is
P = (L2 / L1) · X
Only displace. If the displacement amount P of the deflection point is large, a large curvature of field occurs on the surface to be scanned. Therefore, the displacement amount P of the deflection point is preferably as small as possible.
[0053]
In order to reduce the displacement amount P of the deflection point, the distance L1 from the stop to the front main plane of the collimating optical means with respect to the air-equivalent distance L2 from the rear principal plane of the collimating optical means to the deflecting surface is increased or the diaphragm is stopped. May be reduced as much as possible.
[0054]
However, there is a limit in reducing the amount of eccentricity X of the stop with respect to the collimating optical means, and at present, the eccentric amount can be reduced to only 25 μm at most. Even when adjusting the relative position between the stop and the collimating optical means, it is considered that there is an adjustment error of about 25 μm. In addition, since the distance from the light source to the deflection point is desired to be as small as possible due to the space of the scanning optical system, L1 cannot be increased without limit to L2.
[0055]
Considering dimensional accuracy, assembly errors, and changes in the environment, it is preferable that the curvature of field due to the eccentricity of the stop be at most ± 1 mm. At this time, the positional deviation of the deflection point on the deflection surface is allowed only up to about 125 μm, depending on the scanning optical means.
[0056]
Further, if the position of the deflection point is displaced by about 25 μm due to an error in assembling the unit, the deviation of the deflection point due to the eccentricity of the diaphragm is allowed only 100 μm. As mentioned earlier, it is not easy to reduce the eccentricity of the aperture to 25 μm or less.
L2 / L1 ≦ 4
Need to be
[0057]
In addition, this is an adjustment method for adjusting the position of the deflection point.If the position of the deflection point can be directly observed, if the relative positional relationship between the diaphragm and the collimating optical means is adjusted based on the amount of deviation of the position of the deflection point, Good. However, actually, it is not easy to observe a displacement of several tens μm of a light beam having a length of several mm. Therefore, a method for determining the deviation amount of the deflection point from the light amount of an appropriate light beam will be described below.
[0058]
As the deflecting means (optical deflector) is rotated, the deflecting surface has only a finite size, so that the light flux will be kicked off eventually (a part of the luminous flux cannot enter the deflecting surface). For this reason, the luminous flux, which has maintained a substantially constant light amount while scanning the effective scanning area (printing area), rapidly decreases from a certain position outside the effective scanning area. The same can be said for the writing side.
[0059]
Since the change in the light beam width due to the rotation of the deflecting means is substantially proportional to the rotation angle of the deflecting means, it is possible to know how much the deflecting means has reduced the light beam width by measuring the amount of light beam. Therefore, by measuring the amount of light with respect to the light flux whose degree of light is known by vignetting in design, it is possible to know how much the position of the deflection point deviates from the original position.
[0060]
In order to know the displacement of the deflection point more accurately, the light quantity of each light beam before and after printing may be measured. When the light amount of the light beam is 1 in a state where there is no vignetting in the design, the measured light amount of the light beam having the designed light amount a on the writing side is A, and the measured light amount of the light beam having the designed light amount b on the writing end side is Assuming B, the actual light amount W of the light beam without vignetting can be estimated as W = (A + B) / (a + b).
[0061]
Therefore, the light beam on the writing side has an increased light amount by the ratio of (A / W-a) = (bA-aB) / (A + B), while the light beam on the writing end side has (B / W-b) =- It can be seen that the light amount is increased by the ratio of (bA-aB) / (A + B) (actually, one of them is reduced). As a result, it is found that the deflection point is shifted by (bA-aB) / (A + B) w with respect to the light beam width W, and the position of the collimating optical unit can be adjusted.
[0062]
The advantage of this method is that even if the light amount of the light beam in a state without vignetting is different from the design value, there is no problem in the adjustment, and the difference can be used to make the adjustment relatively accurately.
[0063]
Next, Embodiments 1 to 9 of the present invention will be sequentially described.
[0064]
[Embodiment 1]
FIG. 1 is a sectional view of a main part in the main scanning direction (main scanning sectional view) of the first embodiment of the present invention, and FIG. 2 is a light beam emission unitized from the light source unit 1 to the collimating optical unit 5 of the first embodiment of the present invention. FIG. 2 is a sectional view of a main part showing the unit 10.
[0065]
Here, the main scanning direction indicates a direction perpendicular to the rotation axis of the deflecting unit and the optical axis of the scanning optical element (the direction in which the light beam is deflected and reflected (deflection scanning) by the deflecting unit), and the sub-scanning direction is the deflecting unit. 3 shows a direction parallel to the rotation axis. The main scanning section indicates a plane parallel to the main scanning direction and including the optical axis of the scanning optical system. The sub-scanning section indicates a section perpendicular to the main scanning section.
[0066]
1 and 2, reference numeral 1 denotes a light source unit as light source means, and has a plurality of light emitting units 1a to 1d made of, for example, a semiconductor laser as shown in FIG. Note that the number of light emitting units need not be four. As shown in FIG. 3, the four light emitting portions 1a to 1d are arranged apart from each other in the main scanning direction and the sub scanning direction. As shown in FIG. 3, the distance between the light emitting units is longer in the main scanning direction than in the sub scanning direction. This is because the light source unit 1 having four light emitting units 1a to 1d is rotated in the direction of the arrow shown in FIG. 3 in which the distance between the light emitting units is longer than the actually required distance between the light emitting units in the sub-scanning direction. Thereby, the distance between the light emitting units in the sub-scanning direction is set to a desired value.
[0067]
Reference numeral 2 denotes a relay optical unit as a first optical unit, which has first and second two relay lenses 2a and 2b, and emits divergent light beams emitted from the light emitting units 1a to 1d, respectively, as described later. An image is formed at the deflection point of the deflector.
[0068]
Reference numeral 3 denotes an aperture stop (aperture) as a light beam limiting unit, which shapes the light beam emitted from the relay optical unit 2 into a desired optimum beam shape. In the present embodiment, the principal ray of each of the light emitting units 1a to 1d is disposed at a position separated from the rear principal point of the relay optical unit 2 by the focal length of the relay optical unit 2 toward the collimating optical unit 5 described later. Are parallel to the designed optical axis, so that the center of the emission direction of the light beam emitted from each of the light emitting portions 1a to 1d and the direction of the principal ray substantially coincide, and the stop 3 The light amount distribution is symmetrical with respect to the light beam emitted from.
[0069]
Reference numeral 5 denotes a collimating optical unit serving as a second optical unit. The collimating optical unit 5 includes first and second two condensing lenses (collimator lenses) 5a and 5b. It is converted to a weakly convergent light beam. In the present embodiment, the light beam is converted into a weakly convergent light beam. However, the present invention is not limited to this. For example, even if the light beam is converted into a weakly divergent light beam or a substantially parallel light beam, the effects of the present invention can be obtained. In this embodiment, the spherical aberration and the field curvature generated by the relay optical unit 2 are canceled by the collimating optical unit 5.
[0070]
Reference numeral 6 denotes a lens system (cylindrical lens) which has a predetermined refractive power only in the sub-scanning direction, and converts a light beam emitted from the collimator optical means 5 to a position near a deflection surface 7a of an optical deflector 7 which will be described later. (In the main scanning section, a long line image). In addition, in order to make it possible to adjust the light condensing state in the sub-scanning direction on the photosensitive drum surface 9 as a surface to be scanned, which will be described later, it is made movable in the optical axis direction at the time of assembly, and fixed after adjustment. .
[0071]
Reference numeral 7 denotes an optical deflector as a deflecting means, which is formed of, for example, a rotating polygon mirror, and is rotated at a constant speed in a direction indicated by an arrow A in the figure by a driving means (not shown) such as a motor.
[0072]
In the present embodiment, the stop 3 and the deflecting surface 7a of the optical deflector 7 have a conjugate or substantially conjugate relationship via the collimator optical means 5.
[0073]
Reference numeral 8 denotes a scanning optical unit having a fθ characteristic as a third optical unit. The scanning optical unit 8 includes first and second two optical elements (fθ lenses) 8a and 8b, and is deflected by the optical deflector 7. The two light fluxes form a spot on the surface 9 to be scanned, thereby forming four scanning lines. The scanning optical means 8 in this embodiment has a tilt correction function by making the vicinity of the deflecting surface 7a of the optical deflector 7 and the vicinity of the scanned surface 9 conjugate in the sub-scanning cross section. The sagittal radius of curvature of the optical surfaces of the first and second optical elements 8a and 8b continuously changes as the distance from the optical axis in the main scanning direction changes, and the magnification in the sub-scanning direction is kept constant regardless of the location. .
[0074]
Reference numeral 9 denotes a photosensitive drum surface as a surface to be scanned.
[0075]
Reference numeral 53 denotes a folding mirror (hereinafter, referred to as a “BD mirror”) for synchronization detection, and a plurality of synchronization detection light beams (hereinafter, “BD mirror”) for adjusting the timing of the scanning start position on the photosensitive drum surface 9. (Referred to as “light flux”) toward the BD sensor 52 described later.
[0076]
Reference numeral 50 denotes a slit for detecting synchronization (hereinafter, referred to as a “BD slit”), which is disposed at or near the light-converging point of the light beam converged by the scanning optical means 8 and determines a writing position of an image. I have.
[0077]
Reference numeral 51 denotes a synchronization detection lens (hereinafter, referred to as a “BD conjugate lens”) for establishing a conjugate relationship between the BD mirror 53 and a BD sensor 52 described later, and corrects the tilt of the BD mirror 53.
[0078]
Reference numeral 52 denotes an optical sensor (hereinafter, referred to as a “BD sensor”) as a synchronization detection element. In the present embodiment, a synchronization signal (BD signal) obtained by detecting an output signal from the BD sensor 52 is used. Thus, the timing of the scanning start position of the image recording on the photosensitive drum surface 9 is adjusted for each BD light beam. Further, the amount of displacement of the deflection point on the deflection surface is measured by measuring the light amount of the light beam incident on the BD sensor 52.
[0079]
Note that the above-described components such as the BD mirror 53, the BD slit 50, the BD conjugate lens 51, and the BD sensor 52 constitute one element of a synchronization detection unit (BD optical system) 54. The synchronization detecting means 54 also serves as a light quantity measuring means for measuring the displacement of the deflection point of the optical deflector 7 as described above.
[0080]
In the present embodiment, the four divergent light beams that are light-modulated and emitted from the light source unit 1 according to the image information are once imaged by the relay optical unit 2. At this time, the beam is shaped into a desired shape by the stop 3. Thereafter, the imaged light beam diverges again, but is converted into a weakly convergent light beam by the collimating optical means 5 and enters the cylindrical lens 6. The light beam forms an image near the deflection surface 7 a of the optical deflector 7 in the sub-scanning direction. (Long line image in main scanning section).
[0081]
The four light beams deflected and reflected by the deflecting surface 7a of the optical deflector 7 are spot-formed on the photosensitive drum surface 9 by the scanning optical means 8, and the optical deflector 7 is rotated in the direction of arrow A by Optical scanning is performed on the scanned surface 9 in the direction of arrow B (main scanning direction) at a constant speed. Thus, an image is recorded on the photosensitive drum surface 9 as a recording medium.
[0082]
At this time, in order to adjust the timing of the scanning start position on the photosensitive drum surface 9 before optically scanning the photosensitive drum surface 9, a part of the four light beams deflected and reflected by the optical deflector 7 is reflected by a BD mirror 53. The light is condensed on the surface of the BD slit 50 through the lens, and then guided to the BD sensor 52 through the BD conjugate lens 51. The timing of the scanning start position of image recording on the photosensitive drum surface 9 is adjusted for each BD light beam using a synchronization signal (BD signal) obtained by detecting an output signal from the BD sensor 52.
[0083]
In the multi-beam scanning optical system having the relay optical unit 2 as in the present embodiment, since the deflection points of the light beams are aligned, particularly when the number of light emitting units is large and the distance between the light emitting units is large, deflection of each light beam is performed. As described in the above related art, the present invention exerts an effect of reducing “dot position deviation” and “pitch interval error” with respect to other optical systems in which the positions of points are not aligned. In the present embodiment, the light source unit 1 having four light emitting units is used in order to increase the speed of the relay scanning optical system, and the above effects are utilized.
[0084]
In this embodiment, the distance from the stop 3 to the front main plane of the collimating optical unit 5 is L1, and the air-equivalent distance from the rear main plane of the collimating optical unit 5 to the deflection surface 7a of the optical deflector 7 (the cylindrical lens 6 is When L2 is the distance obtained by dividing the thickness by the refractive index,
L2 / L1 ≦ 4 ‥‥‥ (1)
Satisfies certain conditions.
[0085]
Conditional expression (1) is a condition for enabling the adjustment of the deflection point position of the optical deflector 7, and if conditional expression (1) is not satisfied, the adjustment sensitivity becomes too high, and the adjustment error becomes too large. Not good because of concern.
[0086]
In this embodiment,
L1 = 23.6 mm,
L2 = 93.8 mm
L2 / L1 = 3.97
As a result, the conditional expression (1) is satisfied, whereby the deflection point position can be adjusted.
[0087]
As shown in FIG. 2, a light beam emitting unit (unit member) 10 in the present embodiment includes a light source unit 1, a relay optical unit 2, a collimating optical unit 5, a second holding unit 12 for holding the collimating optical unit 5, and a function of a diaphragm. And a first holding means 11 for holding the light source unit 1, the relay optical means 2, and the second holding means 12, and a housing member (not shown) on which the light deflector 7 and the like are mounted. It is attached detachably.
[0088]
In the present embodiment, the deviation of the deflection point position of the optical deflector 7 is calculated by measuring the light quantity of the light beam incident on the BD sensor 52 with the BD sensor 52. Then, based on the calculation result, the position of the second holding means 12 holding the collimating optical means 5 is adjusted in a direction perpendicular to the optical axis S of the relay optical means 2 by an adjusting jig, so that the light is emitted from the collimating optical means 5. The position of the deflecting point of the luminous flux is substantially matched with the original position.
[0089]
It should be noted that the above substantially coincidence means within ± 50 μm from the original position.
[0090]
In the present embodiment, a gap of about 0.3 mm is provided in the fitting portion between the first holding means 11 and the second holding means 12 to realize the above adjustment. Then, after adjusting the positional relationship between the first holding means 11 and the second holding means 12 to a desired positional relationship using an adjusting jig, an adhesive or the like is applied, and after fixing, the scanning optical system is adjusted from the adjusting jig. Removed.
[0091]
Further, in the present embodiment, at the time of the adjustment, the position of the second holding means 12 is adjusted in the direction of the optical axis S, so that the light-collecting state of the light emitted from the collimating optical means 5 is set to a desired weakly converged light.
[0092]
If the incident position of the light beam on the light deflector 7 is not adjusted, there are the following problems as described above.
[0093]
1. The position at which the light beam enters the scanning optical unit 8 is deviated from the original position, causing a curvature of field, deteriorating the print quality,
2. A part of the light beam is not deflected and reflected by the light deflector 7, causing density unevenness in a printing result or deteriorating printing quality.
[0094]
In this embodiment, in order to solve this problem, each element is set so as to satisfy the conditional expression (1) as described above, and the position of the collimating optical unit 5 is adjusted by the adjusting unit 4, so that the scanning optical system is adjusted. Vignetting and curvature of field due to the eccentricity of the stop 3 and the collimating optical means 5 in the system are reduced to obtain high quality printing.
[0095]
Further, in the present embodiment, as described above, the synchronization detecting means 54 also serves as a light quantity measuring means for measuring the displacement of the deflection point, so that the deflection point position can be adjusted without increasing the number of new optical elements and optical components. I have to.
[0096]
In the present embodiment, the collimating optical unit 5 is fixed at the time of assembly. However, the position of the second holding unit 12 may be actively adjusted by measuring the light amount of the light beam by the synchronization detecting unit 54 even during scanning.
[0097]
As described above, in the present embodiment, as described above, the incident position of the light beam on the light deflector 7 substantially coincides with the predetermined incident position (set within ± 50 μm from the predetermined incident position), or the scanning surface 9 is scanned. At least a part of the effective scanning range so that part or all of the light flux does not protrude from the deflecting surface 7a of the optical deflector 7 during optical scanning, or to reduce field curvature on the surface 9 to be scanned. The positional relationship of the optical elements (members) is adjusted by the adjusting means 4 and the light amount of the light beam outside the effective scanning area on the surface to be scanned 9 and the light beam group that scans the effective scanning area viewed from the light beam are present. The incident position of the light beam on the light deflector 7 is adjusted by the adjusting means 4 so that the light amount of the light beam outside the effective scanning area, which should be the same light amount as the light beam, is adjusted. By satisfying the scanning A scanning optical system capable of reducing vignetting and field curvature due to the eccentricity of the stop 3 and the collimating optical means 5 in the optical system and capable of high-speed printing with high quality is obtained.
[0098]
[Embodiment 2]
FIG. 4 is a sectional view of a main part in the main scanning direction (main scanning sectional view) of the second embodiment of the present invention, and FIG. 5 is a light beam emission unitized from the light source unit 1 to the collimating optical unit 5 of the second embodiment of the present invention. FIG. 2 is a sectional view of a main part showing a unit 14. 4 and 5, the same elements as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.
[0099]
This embodiment is different from the first embodiment in that
(1) the holding relationship between the first holding means 15 and the second holding means 16 is different;
(2) Two light quantity measuring means 18 and 19 are used separately from the synchronization detecting means 54 for measuring the light quantity of the light beam;
{Circle around (3)} A housing member (not shown) on which the light deflector 7 and the like are mounted is provided with two light paths for a light beam for measuring the amount of light across the effective scanning area;
And so on. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.
[0100]
In the present embodiment, the distance L1 from the stop 3 to the front principal plane of the collimating optical means 5 and the air-equivalent distance L2 from the rear principal plane of the collimating optical means 5 to the deflection point are respectively defined.
L1 = 30.8 mm,
L2 = 93.8 mm
L2 / L1 = 3.0
As a result, the conditional expression (1) is satisfied, whereby the deflection point position can be adjusted.
[0101]
As shown in FIG. 5, the light beam emitting unit 14 has a light source unit 1, a relay optical unit 2, a collimating optical unit 5, a stop function, and a first holding unit 15, which holds the light source unit 1 and the relay optical unit 2, a collimating unit. It has a second holding means 16 for holding the optical means 5 and the first holding means 15. In the light beam emitting unit 14, the holding relationship of the first and second holding means 15, 16 is opposite to that of the light beam emitting unit 10 shown in FIG. In the present embodiment, temperature compensation is made possible by using materials having different expansion coefficients for the first and second holding units 15 and 16.
[0102]
In the present embodiment, by installing the light amount measuring means 18 and 19 shown in FIG. 6 at two hatched portions shown in FIG. 4, the light amounts of two light beams outside the effective scanning area (outside the printing area) are measured. The deviation amount of the deflection point is calculated from the measured value. In FIG. 6, reference numeral 18a denotes an imaging lens, and 18b denotes a measuring element (sensor).
[0103]
Based on the calculation result, the position of the collimating optical means 5 is adjusted in the direction perpendicular to the optical axis S of the relay optical means 2 by an adjusting jig, so that the position of the deflection point of the light beam emitted from the collimating optical means 5 is adjusted. Is substantially matched with the original position.
[0104]
In the present embodiment, a gap of about 0.3 mm is provided in the fitting portion between the collimating optical means 5 and the second holding means 16 as shown in FIG. Then, after adjusting the positional relationship between the collimating optical means 5 and the second holding means 16 to a desired positional relationship using an adjusting jig, an adhesive or the like is applied, and after fixing, the scanning optical system is removed from the adjusting jig. I have.
[0105]
Further, in the present embodiment, at the time of the adjustment, the position of the collimating optical unit 5 is adjusted in the direction of the optical axis S, so that the condensing state of the light beam emitted from the collimating optical unit 5 is set to a desired weakly converging light beam. The light quantity measuring means 18 and 19 are removed after fixing the collimating optical means 5 and used for assembling another scanning optical system.
[0106]
As in the present embodiment, the amount of vignetting can be detected more accurately by measuring the light amount of the light beam at two places across the effective scanning area, and the position of the collimating optical means 5 can be corrected with high accuracy. . In the present embodiment, the calculation of the deviation amount of the deflection point is facilitated by installing the two light amount measuring means 18 and 19 at the positions where the designed light amounts are equal.
Further, in the present embodiment, the two light quantity measuring means 18 and 19 are removed after the adjustment as described above, but the two light quantity measuring means 18 and 19 may be left attached so as to enable active adjustment.
[0107]
[Embodiment 3]
FIG. 7 is a cross-sectional view (main scanning cross-sectional view) of a main portion in the main scanning direction according to the third embodiment of the present invention. FIG. 8 is a light beam emission unitized from the light source unit 1 to the collimating optical unit 5 according to the third embodiment of the present invention. FIG. 3 is a sectional view of a main part showing a unit 20. 7 and 8, the same elements as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.
[0108]
This embodiment is different from the first embodiment in that
(1) The presence of the third holding member 23 for holding the first holding means 21 and the second holding means 22;
(2) In addition to the synchronization detecting means 54, one light quantity measuring means 18 is used for measuring the light quantity of the light beam;
(3) A housing member (not shown) on which the light deflector 7 and the like are mounted has one optical path of a light beam for measuring the amount of light provided on the opposite side of the synchronization detecting means 54 across the effective scanning area;
(4) having an adjusting member as adjusting means for adjusting the position of the collimating optical means 5;
And so on. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.
[0109]
In this embodiment, the distance L1 from the stop 3 to the front principal plane of the collimating optical means 5 and the air-equivalent distance L2 from the rear principal plane of the collimating optical means 5 to the deflection point are respectively set in the same manner as in the second embodiment.
L1 = 30.8 mm,
L2 = 93.8 mm
L2 / L1 = 3.0
As a result, the conditional expression (1) is satisfied, whereby the deflection point position can be adjusted.
[0110]
As shown in FIG. 8, the light beam emitting unit 20 has a light source unit 1, a relay optical unit 2, a collimating optical unit 5, a stop function, and a first holding unit 21 that holds the light source unit 1 and the relay optical unit 2. The second holding means 22 for holding the optical means 5, the third holding means 23 for holding the first and second holding means 21 and 22, and the adjustment for adjusting the position of the collimating optical means 5 via the third holding means 23. Means.
[0111]
In the present embodiment, the adjusting means has a piezoelectric element 24, a spring 25, and the like, and applies a voltage to the piezoelectric element 24 fixed to the third holding means 23 based on the amount of displacement of the deflection point. The position of the second holding means 22 for holding the collimating optical means 5 with respect to 23 is displaced in the direction perpendicular to the optical axis S.
[0112]
As in the second embodiment, the first and third holding means 21 and 23 are made of materials having different expansion coefficients to enable temperature compensation.
[0113]
Further, in the present embodiment, by adjusting the position of the light source unit 1 in the direction of the optical axis S, the focusing state of the light beam emitted from the collimating optical unit 5 is set to a desired weakly convergent light beam.
[0114]
In this embodiment, when measuring the light quantity of the light beam, the light quantity measuring means 18 shown in FIG. 6 is arranged at the hatched portion shown in FIG. Is measured, and the deviation amount of the deflection point is calculated from each measured value. Based on the calculation result, the position of the second holding unit 22 holding the collimating optical unit 5 is adjusted by the adjusting unit in the direction perpendicular to the optical axis S of the relay optical unit 2 so that the light is emitted from the collimating optical unit 5. The position of the deflecting point of the luminous flux is substantially matched with the original position. After the adjustment, the light quantity measuring means 18 is removed and used for assembling another scanning optical system. However, the synchronization detecting means 54 measures the light quantity even during scanning, and actively adjusts the position of the collimating optical means 5 by the adjusting means. ing.
[0115]
As in the present embodiment, the amount of vignetting can be detected more accurately by measuring the light amount of the light beam at two places across the effective scanning area, and the position of the collimating optical means 5 can be corrected with high accuracy. . In addition, since the synchronization detecting means 54 continuously adjusts the position based on the information at the time of the initial configuration, it is possible to continuously adjust the deviation of the position of the deflection point due to a change in the time system with high accuracy.
[0116]
[Embodiment 4]
FIG. 9 is a cross-sectional view (main scanning cross-sectional view) of a main portion of the fourth embodiment of the present invention in the main scanning direction. FIG. 10 is a light beam emission unitized from the light source unit 1 to the collimating optical unit 5 of the fourth embodiment of the present invention. FIG. 3 is a sectional view of a main part showing a unit 26. 9 and 10, the same elements as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.
[0117]
This embodiment is different from the first embodiment in that
(1) The second holding means 28, not the first holding means 27, has the function of the diaphragm 3.
(2) having a light detecting means 55 outside the effective scanning area on the writing end side in order to adjust the overall magnification in the main scanning direction;
(3) measuring the overall magnification in the main scanning direction with the light detection means 55 and the synchronization detection means 54 of (2);
(4) The light detection means 55 and the synchronization detection means 54 of (2) also serve as light quantity measurement means for adjusting the deflection point position;
(5) having an adjusting member as an adjusting means for adjusting the position of the diaphragm 3;
And so on. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.
[0118]
In the present embodiment, similarly to the first embodiment, the distance L1 from the stop 3 to the front main plane of the collimating optical unit 5 and the air-equivalent distance L2 from the rear main plane of the collimating optical unit 5 to the deflection point are each set.
L1 = 23.6 mm,
L2 = 93.8 mm
L2 / L1 = 3.97
As a result, the conditional expression (1) is satisfied, whereby the deflection point position can be adjusted.
[0119]
As shown in FIG. 10, the light beam emitting unit 26 has a light source unit 1, a relay optical unit 2, a collimating optical unit 5, a diaphragm, and a second holding unit 28 that holds the collimating optical unit 5, a light source unit 1, and a relay. It has a first holding means 27 for holding the optical means 2 and the second holding means 28, and an adjusting means comprising a piezoelectric element 24 and a spring 25. A member (holding means) having a diaphragm function is different from the light beam emitting unit 10 of the first embodiment shown in FIG.
[0120]
In the present embodiment, the second holding means 28 is fixed to the first holding means 27 near the collimating optical means 5, and further, the piezoelectric element 24 and the spring 25 are fixed to the first holding means 27 near the stop 3 and the second holding means. A pressure is applied to the piezoelectric element 24 in accordance with the position of the deflection point, and the position of the diaphragm 3 is adjusted with respect to the collimating optical means 5.
[0121]
In the present embodiment, the measurement of the light amount of the light beam is performed at the time of assembling at two positions of the light detection unit 55 and the synchronization detection unit 54 arranged outside the effective scanning area on the writing end side at a position where the designed light amount becomes equal. Is measured, and the deviation amount of the deflection point is calculated from each measured value. Based on the calculation result, the position of the diaphragm 3 is adjusted with respect to the collimating optical unit 5 by the adjusting unit, so that the position of the deflection point of the light beam emitted from the collimating optical unit 5 substantially matches the original position. .
[0122]
Note that the light detecting means 55 in the present embodiment has an aperture, an imaging lens, a measuring element (sensor), and the like.
[0123]
In the present embodiment, since the light quantity is measured at two locations with the scanning effective area interposed therebetween, the deflection point position can be adjusted with high accuracy. This allows
1. It is possible to suppress the occurrence of the field curvature caused by the deviation of the deflection point position from the original position,
2. The light beam can be prevented from being kicked by the light deflector.
[0124]
In the present embodiment, by continuously measuring the light amount of the light beam on both sides of the scanning effective area even during scanning, it is possible to continuously and actively adjust the light quantity.
[0125]
[Embodiment 5]
FIG. 11 is a cross-sectional view (main scanning cross-sectional view) of a main part in a main scanning direction according to a fifth embodiment of the present invention. FIG. 12 is a light beam emission unitized from the light source unit 1 to the collimating optical unit 5 according to the fifth embodiment of the present invention. FIG. 4 is a sectional view of a main part showing a unit 29. 11 and 12, the same elements as those shown in FIGS. 4 and 5 are denoted by the same reference numerals.
[0126]
This embodiment is different from the second embodiment in that
{Circle around (1)} that the second holding member 31, not the first holding member 30, has the function of a diaphragm;
(2) having an adjusting member as adjusting means for adjusting the deflection point position;
(3) that the synchronization detecting means 54 also serves as a light quantity measuring means for adjusting the position of the deflection point;
And so on. Other configurations and optical functions are substantially the same as those of the second embodiment, and the same effects are obtained.
[0127]
In the present embodiment, the distance L1 from the stop 3 to the front principal plane of the collimating optical means 5 and the air-equivalent distance L2 from the rear principal plane of the collimating optical means 5 to the deflection point are each set as in the second embodiment.
L1 = 30.8 mm,
L2 = 93.8 mm
L2 / L1 = 3.0
As a result, the conditional expression (1) is satisfied, whereby the deflection point position can be adjusted.
[0128]
As shown in FIG. 12, the light beam emitting unit 29 has a light source unit 1, a relay optical unit 2, a collimating optical unit 5, a first holding unit 30 for holding the light source unit 1 and the relay optical unit 2, a stop function, and collimating optics. A second holding means 31 for holding the means 5 and the first holding means 30 is provided. A member (holding means) having a diaphragm function is different from the light beam emitting unit 14 of the second embodiment shown in FIG.
[0129]
In the present embodiment, the holding member for holding the stop 3 and the collimating optical means 5 is the same member, so that the accuracy of the coaxiality of the two during the assembly is improved. Further, the slight deviation in the position of the deflection point is adjusted by inclining the light beam emitting unit 29 with respect to the housing member 33 holding the light beam emitting unit 29.
[0130]
The adjustment method will be described below. As shown in FIG. 12, a protrusion is provided on either the second holding means 31 or the housing member 33 (in FIG. 12, on the side of the housing member 33), and two springs 25 are arranged so as to sandwich the protrusion. As the two springs 25, springs that attract the light beam emitting unit 29 and the housing member 33 are used. Further, the adjusting screw 32 is cut into a member on the head side of the adjusting screw 32 so that the distance between the second holding means 31 and the housing member 33 around the adjusting screw 32 can be adjusted using the adjusting screw 32. . With the above-described configuration, for example, when the adjustment screw 32 is turned so that the distance around the adjustment screw 32 becomes closer, the opposite side of the protrusion is separated, and conversely, the periphery of the adjustment screw 32 is separated. When the adjustment screw 32 is turned, the opposite side across the projection approaches, so that the direction of the second holding means 31 with respect to the housing member 33 can be easily adjusted, and the position of the deflection point can be adjusted.
[0131]
The spring 25 and the adjusting screw 32 constitute one element of the adjusting means, and the adjusting means can adjust one or both of the position and the orientation of the light emitting unit (unit member) 29. Made of structure.
[0132]
In the present embodiment, similarly to the first embodiment, the amount of displacement of the deflection point is calculated by measuring the amount of the light beam incident on the BD sensor 52, and the direction of the light beam emitting unit 29 is adjusted by the adjusting means as described above. This adjusts the position shift of the deflection point. Further, in the present embodiment, separately from the adjustment, the position of the first holding means 30 with respect to the second holding means 31 is adjusted in the direction of the optical axis S, so that the light-collecting state of the light beam emitted from the collimating optical means 5 can be adjusted to a desired state. A weakly convergent light beam is used.
[0133]
By adjusting the position of the deflection point as described above,
1. It is possible to suppress the occurrence of the field curvature caused by the deviation of the deflection point position from the original position,
2. The light beam can be prevented from being kicked by the light deflector 7.
[0134]
Further, in the present embodiment, since the synchronization detecting means 54 also functions as a light quantity measuring means for measuring the vignetting amount of the light flux, it becomes possible to measure the light quantity of the light flux outside the scanning effective area without increasing new optical elements and optical components. ing.
[0135]
[Embodiment 6]
FIG. 13 is a sectional view (main scanning sectional view) of a main scanning direction according to a sixth embodiment of the present invention, and FIG. 14 is a light beam emission unitized from the light source unit 1 to the collimating optical unit 5 according to the sixth embodiment of the present invention. FIG. 4 is a sectional view of a main part showing a unit 33. 13 and 14, the same elements as those shown in FIGS. 7 and 8 are denoted by the same reference numerals.
[0136]
This embodiment is different from the third embodiment in that
(1) that the second holding means 35, not the first holding means 34, has an aperture function;
(2) Two light quantity measuring means 18 and 19 are used separately from the synchronization detecting means 54 for measuring the light quantity of the light beam;
(3) After measuring the light amount of the light beam, remove the light amount measuring means 18 and 19;
And so on. Other configurations and optical functions are substantially the same as those of the third embodiment, and thus, similar effects are obtained.
[0137]
In the present embodiment, similarly to the third embodiment, the distance L1 from the stop 3 to the front main plane of the collimating optical unit 5 and the air-equivalent distance L2 from the rear main plane of the collimating optical unit 5 to the deflection point are each set.
L1 = 30.8 mm,
L2 = 93.8 mm
L2 / L1 = 3.0
As a result, the conditional expression (1) is satisfied, whereby the deflection point position can be adjusted.
[0138]
The light beam emitting unit 33 has a light source unit 1, a relay optical unit 2, a collimating optical unit 5, a first holding unit 34 for holding the light source unit 1 and the relay optical unit 2 as shown in FIG. The second holding means 35 for holding the optical means 5, the third holding means 36 for holding the first and second holding means 34, 35, and the adjustment for adjusting the position of the collimating optical means 5 with respect to the third holding means 36. Means.
[0139]
In this embodiment, the position of the deflection point of the light beam is adjusted by adjusting the position of the collimating optical unit 5 using the adjusting screw 32 and the spring 25 as the adjusting unit. Specifically, by making the outer diameter of the second holding means 35 near the stop 3 substantially equal to the inner diameter of the third holding means 36, the stop 3 is restrained so as not to move in the direction perpendicular to the optical axis S. Then, the adjusting screw 32 is screwed in the direction perpendicular to the optical axis S from the third holding means 36 near the collimating optical means 5. The spring 25 is arranged on the side opposite to the adjustment screw 32. When adjusting the position of the deflection point, the position of the collimating optical unit 5 is adjusted by adjusting the amount by which the adjusting screw 32 projects from the third holding unit 36.
[0140]
Further, as in the third embodiment, the first and third holding means 34 and 36 are made of materials having different expansion coefficients to enable temperature compensation.
[0141]
Further, in the present embodiment, by adjusting the position of the first holding unit 34 in the direction of the optical axis S, the light-collecting state of the light beam emitted from the collimating optical unit 5 is set to a desired weakly convergent light beam.
[0142]
In the present embodiment, the light quantity measurement of the light flux is performed at the time of assembly by disposing the light quantity measuring means 18 and 19 shown in FIG. 6 at two hatched locations shown in FIG. The amount of light is measured, and the deviation amount of the deflection point is calculated from each measured value. Based on the calculation result, the position of the collimating optical unit 5 is adjusted by the adjusting unit, so that the position of the deflection point of the light beam emitted from the collimating optical unit 5 substantially matches the original position. After the adjustment, the light amount measuring units 18 and 19 are removed and used for assembling another scanning optical system.
[0143]
As in the present embodiment, the amount of vignetting can be detected more accurately by measuring the light amount of the light beam at two places across the effective scanning area, and the position of the collimating optical means 5 can be corrected with high accuracy. .
[0144]
[Embodiment 7]
FIG. 15 is a sectional view (main scanning sectional view) of a main portion in the main scanning direction according to the seventh embodiment of the present invention, and FIG. 16 is a light beam emission unitized from the light source unit 1 to the collimating optical unit 5 according to the seventh embodiment of the present invention. FIG. 4 is a sectional view of a main part showing a unit 37. 15 and 16, the same elements as those shown in FIGS. 1 and 2 are denoted by the same reference numerals.
[0145]
This embodiment is different from the first embodiment in that:
(1) The first holding member 38 holds all of the light source unit 1, the relay optical unit 2, and the collimating optical unit 5,
(2) the collimating optical means 5 is made of a resin lens;
And so on. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.
[0146]
In the present embodiment, the distance L1 from the stop 3 to the front principal plane of the collimating optical means 5 and the air-equivalent distance L2 from the rear principal plane of the collimating optical means 5 to the deflection point are respectively defined.
L1 = 44.1 mm,
L2 = 93.8 mm
L2 / L1 = 2.1
As a result, the conditional expression (1) is satisfied, whereby the deflection point position can be adjusted.
[0147]
As shown in FIG. 16, the light beam emitting unit 37 has a light source unit 1, a relay optical unit 2, a collimating optical unit 5, and a stop function, and holds a light source unit 1, a relay optical unit 2, and a collimating optical unit 5. Holding means 38 is provided.
[0148]
In the present embodiment, the deviation of the deflection point position of the optical deflector 7 is calculated by measuring the amount of the light beam incident on the BD sensor 52 with the BD sensor 52 as in the first embodiment. Based on the calculation result, the position of the first holding means 38 is adjusted in the direction perpendicular to the optical axis S of the relay optical means 2 by adjusting means having a housing member 39 and the like, so that the light flux emitted from the collimating optical means 5 The position of the deflection point is substantially matched with the original position.
[0149]
In this embodiment, a fitting portion of about 0.3 mm is provided at a fitting portion between the housing member 39 for holding the optical deflector 7 and the first holding means 38, and an image plane on the surface 9 to be scanned 9 is provided. The position of the first holding means 38 is displaced in the direction perpendicular to the optical axis S so as to minimize the bending, and is fixed after being adjusted.
[0150]
Further, in the present embodiment, the use of the resin lens for the collimating optical unit 5 reduces the influence of expansion and contraction of the first holding unit 38 due to a change in the environment, and enables temperature compensation.
[0151]
[Embodiment 8]
FIG. 17 is a cross-sectional view of main parts in the main scanning direction (main scanning cross-sectional view) of the eighth embodiment of the present invention, and FIG. 18 is a light beam emission unitized from the light source unit 1 to the collimating optical unit 5 of the eighth embodiment of the present invention. FIG. 4 is a sectional view of a main part showing a unit 39. 17 and 18, the same elements as those shown in FIGS. 15 and 16 are denoted by the same reference numerals.
[0152]
In this embodiment, the structure of the holding means is almost the same as that of the above-described embodiment 7, but the distance from the stop 3 to the collimating optical means 5 is made as long as possible to reduce the displacement of the deflection point, and the collimation with respect to the stop 3 By setting the displacement of the optical means 5 to 25 μm or less, the field curvature caused by the displacement of the deflection point is reduced to 0.7 mm or less.
[0153]
In the present embodiment, the distance L1 from the stop 3 to the front principal plane of the collimating optical means 5 and the air-equivalent distance L2 from the rear principal plane of the collimating optical means 5 to the deflection point are respectively defined.
L1 = 53.3 mm,
L2 = 93.8 mm
L2 / L1 = 1.76
By satisfying the above condition (1), the conditional expression (1) can be sufficiently satisfied, thereby making it possible to adjust the deflection point without adjustment.
[0154]
By the way, in the optical system in which the deflection of the deflection point is 1 μm and the deflection of the deflection point is Mmm, the deflection of the deflection point is suppressed to 1 mm or less. Then, the deviation of the position of the deflection point needs to be 1 / M (μm) or less. If the relative displacement between the stop and the collimating optical unit is assumed to be X μm, L1> MXXL2 may be satisfied. If M = 0.008 mm, X = 50 μm, and L2 = 93.8 mm, L1> 37.5 (mm).
[0155]
As shown in FIG. 18, the light beam emitting unit 39 has a light source unit 1, a relay optical unit 2, a collimating optical unit 5, a function of a stop, and a first holding unit that holds the light source unit 1, the relay optical unit 2, and the collimating optical unit 5. It has means 40.
[0156]
[Embodiment 9]
FIG. 19 is a cross-sectional view (main scanning cross-sectional view) of a main part in the main scanning direction according to the ninth embodiment of the present invention. FIG. FIG. 4 is a sectional view of a main part showing a unit 41. 19 and 20, the same elements as those shown in FIGS. 15 and 16 are denoted by the same reference numerals.
[0157]
In this embodiment, the structure of the holding means is almost the same as that of the above-described seventh embodiment, but an adjusting mirror 43 shown in FIG. 21 is provided as an adjusting means in the optical path from the light beam emitting unit 41 to the deflecting means 5. By adjusting the angle of 43, the position of the deflection point on the deflection surface 7a can be adjusted.
[0158]
Specifically, the light beam emitted from the light beam emitting unit 41 is made to enter substantially the center of the adjustment mirror 43, and is configured to be rotatable around a rotation axis passing through the center of the adjustment mirror 43. Further, the adjusting screw 32 and the like are abutted against a portion extending from the rotation axis of the adjusting mirror 43 to the member in the radial direction, and the amount of the adjusting screw 32 is adjusted to adjust the angle of the adjusting mirror 43.
[0159]
The position of the deflection point on the optical deflector 7 may be actively adjusted by using a piezoelectric element instead of the adjustment screw 32.
[0160]
As shown in FIG. 20, the light beam emitting unit 41 has a light source unit 1, a relay optical unit 2, a collimating optical unit 5, a function of a stop, and a first holding unit that holds the light source unit 1, the relay optical unit 2, and the collimating optical unit 5. Means 42 are provided.
[0161]
In the present embodiment, the deviation of the deflection point position of the optical deflector 7 is calculated by measuring the amount of the light beam incident on the BD sensor 52 with the BD sensor 52 as in the first embodiment. Then, by adjusting the angle of the adjustment mirror 43 based on the calculation result, the position of the deflection point of the light beam emitted from the collimating optical unit 5 is made substantially coincident with the original position.
[0162]
In the present embodiment, the use of the resin lens for the collimating optical unit 5 reduces the influence of expansion and contraction of the first holding unit 42 due to a change in environment, and enables temperature compensation.
[0163]
[Image forming apparatus]
FIG. 22 is a cross-sectional view of a main part in the sub-scanning direction showing an embodiment of the image forming apparatus of the present invention. In the figure, reference numeral 104 denotes an image forming apparatus. Code data Dc is input to the image forming apparatus 104 from an external device 117 such as a personal computer. The code data Dc is converted into image data (dot data) Di by the printer controller 111 in the apparatus. This image data Di is input to the optical scanning unit (scanning optical system) 100 having the configuration shown in the first to ninth embodiments. Then, a light beam 103 modulated according to the image data Di is emitted from the optical scanning unit 100, and the photosensitive surface of the photosensitive drum 101 is scanned in the main scanning direction by the light beam 103.
[0164]
The photosensitive drum 101 serving as an electrostatic latent image carrier (photoconductor) is rotated clockwise by a motor 115. With this rotation, the photosensitive surface of the photosensitive drum 101 moves in the sub-scanning direction perpendicular to the main scanning direction with respect to the light beam 103. Above the photosensitive drum 101, a charging roller 102 for uniformly charging the surface of the photosensitive drum 101 is provided so as to contact the surface. The surface of the photosensitive drum 101 charged by the charging roller 102 is irradiated with a light beam 103 scanned by the optical scanning unit 100.
[0165]
As described above, the light beam 103 is modulated based on the image data Di, and by irradiating the light beam 103, an electrostatic latent image is formed on the surface of the photosensitive drum 101. This electrostatic latent image is developed as a toner image by a developing device 107 disposed so as to contact the photosensitive drum 101 on the downstream side in the rotation direction of the photosensitive drum 101 from the irradiation position of the light beam 103.
[0166]
The toner image developed by the developing device 107 is transferred onto a sheet 112 as a transfer material by a transfer roller 108 disposed below the photosensitive drum 101 so as to face the photosensitive drum 101. The sheet 112 is stored in a sheet cassette 109 in front of the photosensitive drum 101 (right side in FIG. 15), but can be fed manually. A paper feed roller 110 is provided at an end of the paper cassette 109, and feeds the paper 112 in the paper cassette 109 to a transport path.
[0167]
As described above, the sheet 112 onto which the unfixed toner image has been transferred is further conveyed to the fixing device behind the photosensitive drum 101 (left side in FIG. 22). The fixing device includes a fixing roller 113 having a fixing heater (not shown) therein and a pressure roller 114 disposed so as to be in pressure contact with the fixing roller 113, and the paper conveyed from the transfer unit. The unfixed toner image on the sheet 112 is fixed by heating the sheet 112 while pressing it at a pressure contact portion between the fixing roller 113 and the pressure roller 114. Further, a paper discharge roller 116 is disposed behind the fixing roller 113, and discharges the fixed paper 112 to the outside of the image forming apparatus.
[0168]
Although not shown in FIG. 22, the print controller 111 controls not only the above-described data conversion but also control of various parts in the image forming apparatus including the motor 115 and a polygon motor in the optical scanning unit described later. I do.
[0169]
[Color image forming apparatus]
FIG. 23 is a schematic view of a main part of a color image forming apparatus according to an embodiment of the present invention. This embodiment is a tandem-type color image forming apparatus in which four scanning optical systems (optical scanning devices) are arranged and image information is recorded in parallel on a photosensitive drum surface as an image carrier. In FIG. 23, reference numeral 260 denotes a color image forming apparatus, 211, 212, 213, and 214 each denote an optical scanning device having any of the configurations shown in the first to ninth embodiments, and 211, 212, 213, and 214 denote image carriers, respectively. , 231, 232, 233, and 234 are developing devices, and 51 is a transport belt.
[0170]
In FIG. 23, R (red), G (green), and B (blue) color signals are input to the color image forming apparatus 260 from an external device 252 such as a personal computer. These color signals are converted into respective image data (dot data) of C (cyan), M (magenta), Y (yellow), and B (black) by the printer controller 253 in the apparatus. These image data are input to the optical scanning devices 211, 212, 213, and 214, respectively. Then, light beams 241, 242, 243, and 244 modulated in accordance with each image data are emitted from these optical scanning devices, and the photosensitive surfaces of the photosensitive drums 221, 222, 223, and 224 are emitted by these light beams. Scanning is performed in the main scanning direction.
[0171]
In the color image forming apparatus according to the present embodiment, four optical scanning devices (211, 212, 213, 214) are arranged, each of which is for C (cyan), M (magenta), Y (yellow), and B (black). Correspondingly, image signals (image information) are recorded on the photosensitive drums 221, 222, 223, and 224 in parallel, and a color image is printed at high speed.
[0172]
As described above, the color image forming apparatus according to the present embodiment uses the four light scanning devices 211, 212, 213, and 214 to use the light beams based on the respective image data to convert the latent images of each color into the corresponding photosensitive drums 221 and 222, respectively. , 223, 224. Thereafter, multiple transfer to a recording material is performed to form one full color image.
[0173]
As the external device 252, for example, a color image reading device provided with a CCD sensor may be used. In this case, the color image reading apparatus and the color image forming apparatus 260 constitute a color digital copying machine.
[0174]
【The invention's effect】
According to the present invention, the position of at least a part of the plurality of optical elements (members) constituting the scanning optical system is adjusted by the adjusting unit and / or the conditional expression (1) is satisfied as described above. Accordingly, it is possible to reduce the vignetting and the field curvature caused by the eccentricity of the stop and the collimating optical means in the scanning optical system, and to achieve a scanning optical system capable of high-speed printing at high speed and an image forming apparatus using the same. .
[Brief description of the drawings]
FIG. 1 is a main scanning sectional view of a first embodiment of the present invention.
FIG. 2 is a sectional view of a main part of a light beam emitting unit according to the first embodiment of the present invention.
FIG. 3 is an explanatory diagram showing an arrangement of each light emitting unit.
FIG. 4 is a main scanning sectional view according to a second embodiment of the present invention.
FIG. 5 is a sectional view of a main part of a light beam emitting unit according to a second embodiment of the present invention.
FIG. 6 is a schematic diagram of a main part of a light amount measuring unit.
FIG. 7 is a main scanning cross-sectional view according to a third embodiment of the present invention.
FIG. 8 is a sectional view of a main part of a light beam emitting unit according to a third embodiment of the present invention.
FIG. 9 is a main scanning sectional view of a fourth embodiment of the present invention.
FIG. 10 is a sectional view of a main part of a light beam emitting unit according to a fourth embodiment of the present invention.
FIG. 11 is a main scanning sectional view according to a fifth embodiment of the present invention.
FIG. 12 is a sectional view of a main part of a light beam emitting unit according to a fifth embodiment of the present invention.
FIG. 13 is a main scanning cross-sectional view according to a sixth embodiment of the present invention.
FIG. 14 is a sectional view of a main part of a light beam emitting unit according to a sixth embodiment of the present invention.
FIG. 15 is a main scanning cross-sectional view according to a seventh embodiment of the present invention.
FIG. 16 is a sectional view of a main part of a light beam emitting unit according to a seventh embodiment of the present invention.
FIG. 17 is a main scanning cross-sectional view according to the eighth embodiment of the present invention.
FIG. 18 is a sectional view of a main part of a light beam emitting unit according to an eighth embodiment of the present invention.
FIG. 19 is a main scanning sectional view of a ninth embodiment of the present invention.
FIG. 20 is a sectional view of a main part of a light beam emitting unit according to a ninth embodiment of the present invention;
FIG. 21 is a schematic view of a main part of an adjustment mirror.
FIG. 22 is a schematic diagram of a main part of the image forming apparatus of the present invention.
FIG. 23 is a schematic diagram of a main part of the color image forming apparatus of the present invention.
FIG. 24 is an optical path diagram of a light beam emitted from each light emitting unit.
FIG. 25 is an explanatory diagram of a dot position shift.
FIG. 26 is an explanatory diagram of a pitch interval error.
FIG. 27 is an explanatory diagram of a deflection point position shift.
[Explanation of symbols]
1a, 1b, 1c, 1d Light emitting unit (semiconductor laser)
1 light source means (light source unit)
2a, 2b relay lens
2 First optical means (relay optical means)
3 Aperture stop
5a, 5b Condenser lens (collimator lens)
5. Second optical means (collimating optical means)
6 lens system (cylindrical lens)
7. Deflection means (optical deflector)
7a Deflection surface
8 Third optical means (scanning optical means)
8a First optical element
8b Second optical element
9 Scanned surface (photosensitive drum surface)
10, 14, 20, 26, 29, 33, 37, 39, 41 Light beam emitting unit
11, 15, 21, 27, 30, 34, 38, 40, 42 First holding means
12, 16, 22, 28, 31, 35, second holding means
17, 19, 33, 39 Housing member
18, 19 Light intensity measuring means
23, 36 Third holding means
24 Piezoelectric element
25 spring
32 Adjustment screw
43 Adjustment mirror
50 BD slit
51 BD conjugate lens
52 BD sensor
53 BD mirror
100 scanning optical system
101 Photosensitive drum
102 Charging roller
103 light beam
104 Image forming apparatus
107 Developing device
108 transfer roller
109 Paper cassette
110 Paper feed roller
111 Printer Controller
112 Transfer material (paper)
113 Fixing roller
114 pressure roller
115 motor
116 Paper ejection roller
117 External device
211, 212, 213, 214 Scanning optical system
221, 222, 223, 224 Image carrier (photosensitive drum)
231, 232, 233, 234 Developer
241 Conveyor belt
251 multi-beam laser
252 External device
253 Printer Controller
260 Color Image Forming Apparatus

Claims (27)

Light source means, first optical means for forming an image of the light beam emitted from the light source means, light beam limiting means for restricting the light beam from the first optical means, and the light beam formed by the first optical means. A second optical unit for bringing the light beam passing through the restricting unit into a desired condensed state, a deflecting unit including a deflecting surface for deflecting the light beam guided from the second optical unit, and a light beam deflected by the deflecting unit A third optical means for guiding the light onto the surface to be scanned, and the light beam restricting means and the deflecting surface of the deflecting means are in a conjugate or substantially conjugate relationship via the second optical means. In a scanning optical system that optically scans the surface to be scanned by rotating the deflecting means,
A scanning optical system comprising adjusting means for adjusting a positional relationship of at least a part of a member provided in an optical path from the light source means to the surface to be scanned. When a distance from the light beam restricting means to the second optical means is L1, and a distance from the second optical means to the deflection surface is L2, L2 / L1 ≦ 4.
2. The scanning optical system according to claim 1, wherein the following condition is satisfied. The adjusting means adjusts a positional relationship of members provided in an optical path from the light source means to the deflecting means such that an incident position of the light beam on the deflecting means substantially coincides with a predetermined incident position. The scanning optical system according to claim 1, wherein: The optical path extending from the light source to the deflecting unit so that part or all of the light flux does not protrude from the deflecting surface of the deflecting unit during the optical scanning of the effective scanning range of the surface to be scanned. 3. The scanning optical system according to claim 1, wherein a positional relationship between members provided therein is adjusted. The scanning optical system according to claim 1, wherein the adjustment unit adjusts a positional relationship of at least a part of the optical elements so as to reduce curvature of field on the surface to be scanned. The adjusting unit is configured to set the effective light amount to be essentially equal to the light amount of the light beam outside the effective scanning region on the surface to be scanned and the light amount of the light beam existing across the light beam group scanning the effective scanning region when viewed from the light beam. 3. The scanning optical system according to claim 1, wherein an incident position of the light beam on the deflecting means is adjusted so that the light amount of the light beam outside the scanning area becomes equal. The said adjustment means has a structure which can adjust the relative positional relationship of the said 2nd optical means and the said light beam restriction means in the direction perpendicular to the optical axis of the said 1st optical means. Item 3. The scanning optical system according to item 1 or 2. The scanning optical system according to claim 1, further comprising a holding unit that holds the second optical unit and is formed integrally with the light beam limiting unit. 9. The scanning optical system according to claim 7, wherein the adjusting unit has a structure in which either or both of the position and the orientation of the second optical unit can be adjusted. 10. Each member from the light source unit to the second optical unit is housed in one unit member, and the unit member is detachably attached to a housing member on which the deflection unit and the like are mounted. The scanning optical system according to claim 1, wherein: The scanning optical system according to claim 10, wherein the adjusting unit has a structure in which one or both of the position and the orientation of the unit member can be adjusted. The scanning optical system according to claim 1, wherein the adjusting unit has a mirror, and adjusts an angle of the mirror. Light source means, first optical means for forming an image of the light beam emitted from the light source means, light beam limiting means for restricting the light beam from the first optical means, and the light beam formed by the first optical means. A second optical unit for bringing the light beam passing through the restricting unit into a desired condensed state, a deflecting unit including a deflecting surface for deflecting the light beam guided from the second optical unit, and a light beam deflected by the deflecting unit A third optical means for guiding the light onto the surface to be scanned, and the light beam restricting means and the deflecting surface of the deflecting means are in a conjugate or substantially conjugate relationship via the second optical means. In a scanning optical system that optically scans the surface to be scanned by rotating the deflecting means,
When the distance from the light beam limiting means to the second optical means is L1, and the distance from the second optical means to the deflection surface is L2,
L2 / L1 ≦ 4
A scanning optical system characterized by satisfying the following conditions. The said adjustment means has a structure which can adjust the relative positional relationship of the said 2nd optical means and the said light beam restriction means in the direction perpendicular to the optical axis of the said 1st optical means. Item 14. The scanning optical system according to item 13. 15. The scanning optical system according to claim 13, wherein the adjusting unit has a structure in which either or both of the position and the orientation of the second optical unit can be adjusted. The apparatus according to claim 1, wherein the deflecting unit is mounted on a housing member, and the housing member has an optical path secured to measure a light amount of a light beam incident outside the effective scanning area of the surface to be scanned. 16. The scanning optical system according to any one of 1 to 15. 17. The scanning optical system according to claim 16, wherein a plurality of optical paths for measuring the light amount of the light beam are provided. 18. The scanning optical system according to claim 17, wherein two or more light paths for measuring the amount of light are provided with a light beam group for scanning an effective scanning area on the surface to be scanned separated. 19. The scanning optical system according to claim 1, further comprising a light amount measuring unit that measures a light amount of a light beam outside the effective scanning area of the surface to be scanned. 20. The scanning optical system according to claim 19, wherein the light amount measuring unit also functions as a synchronization detecting unit that measures a writing start timing on the surface to be scanned. 20. The scanning optical system according to claim 19, comprising a plurality of said light quantity measuring means. 22. The scanning optical system according to claim 21, further comprising: two light amount measuring units separated by a light beam group that scans an effective scanning area of the scanned surface. The scanning optical system according to claim 1, wherein the light source unit has a plurality of light emitting units. A scanning optical system according to any one of claims 1 to 23, a photosensitive member disposed on the surface to be scanned, and a photosensitive member formed on the photosensitive member by a light beam scanned by the scanning optical system. It has a developing device for developing an electrostatic latent image as a toner image, a transfer device for transferring the developed toner image to a transfer material, and a fixing device for fixing the transferred toner image to the transfer material. Image forming apparatus. 24. A scanning optical system according to claim 1, further comprising: a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the scanning optical system. Image forming apparatus. 24. A color image, comprising: a plurality of image carriers each arranged on a surface to be scanned of the scanning optical system according to claim 1 and forming images of different colors. Forming equipment. 27. The color image forming apparatus according to claim 26, further comprising a printer controller for converting a color signal input from an external device into image data of a different color and inputting the data to each scanning optical system.

Images