JPH0815625A - Method of adjusting plural light beams scan device - Google Patents

Abstract

PURPOSE:To easily adjust a light beam interval on a photosensitive body and to hold a light beam size on the photosensitive body also excellently. CONSTITUTION:A cylinder lens holder 63 is moved on the cylinder lens holder 64 to be fixed so that the light beam interval on the photosensitive body becomes the interval between cylinder lenses 62A, 62B obtained from a focal distance of a cylinder lens system 62 becoming a target interval based on an empirical formula. Further, the cylinder lens holder 64 is moved to be fixed so that the light beam interval on the photosensitive body becomes a distance from the 62B to a light deflector 35 obtained from the focal distance of the cylinder lens system 62 becoming the target interval based on the empirical formula. Thus, the light beam interval on the photosensitive body is made the target interval, and the light beam size on the photosensitive body is made a target light beam size.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of adjusting a plurality of light beam scanning devices, and more particularly, to a method of adjusting a plurality of light beam scanning devices for simultaneously two-dimensionally scanning a photosensitive member with a plurality of irradiated light beams. Regarding

[0002]

2. Description of the Related Art In a plural light beam scanning device such as a copying machine or a printer, the following device has been proposed in order to achieve high speed or high resolution (JP-A-51-1).
Japanese Patent Laid-Open No. 00742, Japanese Patent Laid-Open No. 54-66131).
That is, a plurality of semiconductor lasers are arranged, and a light beam emitted from a plurality of arranged light sources is made to enter a deflector such as a rotating polygon mirror as parallel rays by a focusing lens. The light beam incident on the deflector is deflected by the deflector, and the deflected light beam main-scans the photosensitive member moving in the sub-scanning direction to form an image.

In such an apparatus, in order to form an image of a proper image quality on the photoconductor, it is necessary to make the intervals of a plurality of light beams for main scanning the photoconductor equal.

Therefore, the following devices have been proposed as devices for adjusting the intervals between a plurality of light beams (JP-A-57-54914 and JP-A-62-569).
No. 19, JP-A-4-101112, etc.).

That is, in the apparatus disclosed in Japanese Patent Laid-Open No. 57-54914, an afocal lens capable of changing the imaging magnification only in a plane perpendicular to the deflection plane of the light beam deflected by the optical deflector. I am using a light beam expander. This afocal light beam expander is composed of three lens groups, one lens group of the three lens systems is fixed, and the other two lens groups are movable and movable. By moving the two lens groups, the angle formed by each of the two light beams emitted from the afocal light beam expander is set to a desired angle, and the distance between the two light beams on the photosensitive medium is adjusted.

In the device disclosed in Japanese Patent Laid-Open No. 62-56919, light beams emitted from a plurality of semiconductor lasers arranged close to each other enter a cylinder lens through an imaging lens, After passing through the lens, it is reflected by a polygon mirror and focused on the photoconductor through the fθ lens and the cylinder lens. In this apparatus, the scanning magnification in the sub-scanning direction is set to a desired magnification by changing the imaging magnification of the imaging lens, and the interval between the light beams on the photoconductor is set to a desired value. That is, the distance from the semiconductor laser to the imaging lens and the distance from the imaging lens to the polygonal mirror are obtained from the imaging formula of the imaging lens and the imaging magnification formula,
The light source and the imaging lens, and the imaging lens and the cylinder lens are moved relative to each other so that the distance is obtained.

Further, in Japanese Patent Laid-Open No. 4-10112,
In the optical path between the light emitting section composed of a plurality of semiconductor lasers arranged in a row in the sub-scanning direction and the rotary polygon mirror for deflecting the semiconductor laser light beam emitted from the light emitting section, two groups of front group and rear group are provided. An adjusting member composed of two lens groups is provided, and the focusing magnification is changed by changing the focal length by relatively changing the distance between the two lens groups of the front group and the rear group. Is being adjusted.

[0008]

The distance between the two light beams can be adjusted by these methods. However, when the positions of a plurality of lenses are adjusted independently, the same lens may be used depending on the error at the time of adjustment. However, there is a drawback in that it takes a lot of time to adjust because it is necessary to move a plurality of times.

Further, there is a possibility that the position of the beam waist of the laser beam may be displaced from the surface of the photoconductor and the diameter of the light beam on the photoconductor may be changed.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to easily adjust the light beam interval on the photoconductor and keep the light beam diameter on the photoconductor good. It is an object of the present invention to provide a method of adjusting a multiple light beam scanning device that can be performed.

[0011]

In order to achieve the above object, the invention according to claim 1 is a light source for irradiating a plurality of light beams, and each of the plurality of light beams emitted from the light source is a parallel light beam. Light beam collimating means, main scanning means for deflecting the plurality of light beams from the light beam collimating means to perform main scanning on the photoconductor, and at least one of the plurality of light beams and the photoconductor relative to each other. The sub-scanning means for moving and sub-scanning, and the plurality of incident light beams arranged between the light source and the main scanning means are focused on the main scanning means, and the lens power is only in the sub-scanning direction. And a first lens system and a second lens system, the distance between the first lens system and the second lens system is adjustable, and the first lens system and the second lens system are integrated. Can be moved in the optical axis direction A first imaging means, and the second imaging means for imaging the main scanning light beam on the photoreceptor,
In adjusting the multiple light beam scanning device with
The distance between the first lens system and the second lens system is changed, and the first lens system and the second lens system are integrally moved in the optical axis direction to move the first lens system and the second lens system.
By changing the distance from the lens system close to the main scanning means to the main scanning means in the lens system, the distance between the light beams on the photoconductor is adjusted to the target distance and The light beam diameter of is adjusted so as to be the target light beam diameter.

According to a second aspect of the invention, in the first aspect of the invention, the distance I between the first lens system and the second lens system is

[0013]

## EQU00003 ## The distance L from the lens system close to the main scanning means to the main scanning means of the first lens system and the second lens system is changed based on I = a.f ² + b.f + c. Is

[0014]

## EQU4 ## Changes are made based on L = d.f + e.

However, a, b, c, d and e are constants, and f is the focal length of the first image forming means.

[0016]

According to the first aspect of the invention, in the plural light beam scanning device, each of the plural light beams emitted from the light source by the light beam collimating means is made into a parallel light beam, and the main scanning means scans the light beam from the light beam collimating means. A plurality of light beams are deflected to main-scan the photoconductor, and at least one of the light beam and the photoconductor is relatively moved by sub-scanning means to perform sub-scanning. It should be noted that the sub-scanning mode includes the case where two light beams are moved with respect to the photoconductor, the case where the photoconductor is moved with respect to the two light beams, and the case where both the two light beams and the photoconductor are relatively moved. May be moved to. Then, the plural light beam scanning device forms an image of the light beam, which is mainly scanned by the second image forming means, on the photoconductor.

According to the present invention, the following first image forming means is arranged between the light source and the main scanning means.

That is, the first image forming means includes the first lens system and the second lens system each having a lens power only in the sub-scanning direction.
And a first lens system and a second lens system.
The distance between the lens systems can be adjusted, and the first lens system and the second lens system can be integrally moved in the optical axis direction, and the incident light beam is imaged on the main scanning means.

Further, according to the present invention, by adjusting the distance between the light beams on the photoconductor and the diameter of the light beam on the photoconductor using the first image forming means, the adjustment of the plural light beam scanning devices is performed as follows. I am doing so.

First, the light beam interval of the plural light beam scanning device will be described. The image forming magnification of the light emitting point of the light source, that is, the object point and the light beam incident point of the photoconductor, that is, the image point is expressed by the following equation (5).

[0021]

(F _col / f _cyl ) × M (5) where f _col is the focal length of the light beam collimating means, f _cyl is the focal length of the first image forming means, and M is the second. It is the imaging magnification in the direction orthogonal to the light deflection direction of the imaging means.

Here, for example, the light emitting point distance S0 between the two light sources and the distance S1 between the two light beams on the photoconductor are expressed by the following equation (6).

[0023]

[Equation 6] S1 = (f _col / f _cyl ) × M × S0 (6) Even if the optical system of the multiple light beam scanning device is set to satisfy the equation (6), the component tolerance and The light beam interval on the photoconductor may deviate from the target interval due to temperature fluctuations. In order to correct the deviation, the focal length f _cyl of the first image forming means of the parameters on the right side of the expression (6) is used.
Should be changed.

By the way, from the equation (6), the change amount of the interval of the light beam on the photosensitive member when the focal length f _cyl of the first image forming means is changed by a constant distance can be obtained. Therefore,
Considering the deviation of the light beam on the photoconductor from the target interval, the focal length of the first image forming unit that makes the light beam interval on the photoconductor approximately the target interval can be obtained.

Here, in order to change the focal length of the first image forming means, the distance between the first lens system and the second lens system forming the first image forming means may be changed. .

Therefore, according to the present invention, the distance between the first lens system and the second lens system is changed so that the distance between the light beams on the photoconductor is adjusted to a substantially target distance.

By the way, the focal length f of the first image forming means is
_From a number of experimental results, _cyl and the distance I between the first lens system and the second lens system can be approximated to a quadratic relationship represented by the following expression (7).

[0028]

## _EQU00007 ## I = _{a.f cyl} ² + _{b.f cyl} + c (7) where a, b and c are constants of the first lens system and the second lens system.

Therefore, in the invention of claim 2, the distance I between the first lens system and the second lens system is changed based on the equation (7). That is, when the focal length of the first image forming unit for making the distance between the light beams on the photoconductor obtained based on the equation (1) substantially equal to the target distance is f, the first value obtained from the expression (7) is obtained. The distance between the first lens system and the second lens system is changed so that the distance I becomes 1 between the first lens system and the second lens system.

Next, the light beam diameter of the plural light beam scanning device will be described. As described above, even if the focal length of the first image forming unit is adjusted, if the position of the first image forming unit with respect to the main scanning unit is kept at the same position, the diameter of the light beam on the photoconductor is reduced. Is larger than the target light beam diameter.
Therefore, it is necessary to set the distance between the light beams on the photoconductor to the target distance and the diameter of the light beam on the photoconductor to the target light beam diameter.

Here, in order to make the diameter of the light beam on the photoconductor substantially equal to the diameter of the target light beam, it is necessary to position the focal point of the first image forming means at the position of the main scanning means.

Therefore, according to the first aspect of the present invention, the first lens system and the second lens system are integrally moved in the optical axis direction, and the main scanning means of the first lens system and the second lens system is used. The distance from the lens system close to the main scanning means to the main scanning means is changed.

By the way, the focus position of the first image forming means from any one of the first lens system and the second lens system near the main scanning means, that is, the distance L to the main scanning means, and the position on the photosensitive member. The relationship with the focal length f _cyl of the first image forming unit that sets the light beam interval to the target interval can be expressed by the following expression (8) from the results of many experiments.

[0034]

(8) L = d · f _cyl + e (8) where d and e are constants of the first lens system and the second lens system.

Therefore, according to the second aspect of the present invention, the distance L from the lens system of the first lens system and the second lens system close to the main scanning means to the main scanning means is calculated based on the equation (8). Have changed. That is, the first lens system and the second lens system, whichever is closer to the main scanning unit and the main scanning unit, have the distance L obtained from the equation (8), the first
The lens system and the second lens system are moved together on the optical axis.

In the invention described in claim 1 and the invention described in claim 2 described above, the first lens system and the second lens are changed after the distance between the first lens system and the second lens system is changed. The distance from any one close to the main scanning means of the system may be changed, and the distance from any one close to the main scanning means of the first lens system and the second lens system to the main scanning means may be changed. After the change, the distance between the first lens system and the second lens system may be changed.

Thus, the distance between the first lens system and the second lens system is changed, and the first lens system and the second lens system are changed.
The lens system is moved as a unit in the optical axis direction to change the distance from any one of the first lens system and the second lens system close to the main scanning unit to the main scanning unit to set the light beam interval as a target. Since the distance and the light beam diameter are set to the target light beam diameter, it is easy to adjust the light beam distance on the photoconductor to the target distance and the light beam diameter on the photoconductor to the target light beam diameter. be able to.

Here, the distance between the first lens system and the second lens system, and the distance from the lens system near the main scanning means to the main scanning means of the first lens system and the second lens system are changed. To achieve this, for example, a first lens system fixing means for fixing the first lens system at an arbitrary location and a second lens system fixing means for fixing the second lens system at an arbitrary location, The second lens system fixing means may be moved along with the movement of the first lens system fixing means, and the second lens system fixing means may be independently movable. That is,
The distance between the first lens system and the second lens system is changed by moving the second lens system fixing means that is movable independently of the first lens system fixing means. Further, when changing the distance from the lens system of the first lens system and the second lens system which is closer to the main scanning unit to the main scanning unit, the first lens system fixing unit is moved and the second lens system is moved accordingly. This is done by moving the lens system fixing means of.

[0039]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an outline of a multiple light beam scanning device of this embodiment.

As shown in FIG. 1, the plural light beam scanning device comprises a laser scanning unit 12 and a developing / transferring section 40. The laser scanning unit 12 includes a semiconductor laser array 60 and a lens system 3 in a unit case 30.
3 (see also FIG. 2). The lens system 33 forms a collimator lens 61 as a light beam collimating means for collimating the light beams A and B and a light beam from the collimator lens 61 into a linear shape in the main scanning direction to an optical deflector 35 as a main scanning means. A cylinder lens system 62 for forming an image is provided.
The cylinder lens system 62 includes a cylinder lens 62A as a first lens system and a cylinder lens 62B as a second lens system. The cylinder lens 62A is
The cylinder lens 62 is mounted and fixed on a cylinder lens holder 63 as a first lens system fixing means.
B is mounted and fixed on a cylinder lens holder 64 as a second lens system fixing means. The cylinder lens holder 64 is movably installed on the rail 30 parallel to the optical axis of the light beam. The cylinder lens holder 63 is movably installed on a rail (not shown) parallel to the optical axis of the light beam on the cylinder lens holder 64.

Further, the laser scanning unit 12 is a polygon mirror for deflecting the light beams A and B from the semiconductor laser array 60 in a direction corresponding to the main scanning direction at a constant angular velocity,
That is, the optical deflector 35 is provided. Further, the laser scanning unit 12 includes the light beams A and B deflected by the light deflector 35 at a constant angular velocity in a direction corresponding to the main scanning direction.
To form an image on the photoconductor 10 and main-scan the photoconductor 10 at a constant speed.
It has.

Further, in the optical paths of the light beams A and B that have passed through the fθ lens 36, a reflecting mirror arranged in a predetermined positional relationship to reflect the light beams A and B toward the scanning line position of the photoconductor 10. 37 and 38 are provided. The reflection mirror 38 is a cylindrical mirror. Further, a sealing optical window 41 is attached to the unit case 30 as a light outlet.

The developing and transferring section 40 includes a charging corotron 11 for precharging the photoconductor 10, a developing device 13 for developing a latent image written on the photoconductor 10 to form a toner image, and a toner image on the photoconductor 10. The transfer pretreatment corotron 15 for aligning the polarities of the electric charges of the above and removing the electric charges on the photoconductor 10 is provided. Further, the development transfer section 40 is a transfer corotron 1 that transfers the toner image on the photoconductor 10 to the recording paper 17.
6. After the transfer process, the electrostatic charge of the recording paper 17 is removed, and the charge-removing corotron 18 that removes the recording paper 17 electrostatically attracted to the photoconductor 10, the cleaner 19 that slowly discharges the residual toner on the photoconductor 10, and the photoconductor 10. A static elimination lamp 20 for removing the residual charge is provided. The photoconductor 10 is rotationally moved (sub-scanned) in a direction orthogonal to the main scanning direction of the light beams A and B by a driving unit (not shown). It should be noted that the light deflection surface 35 and the photoconductor 10 are the light deflection surface 3
It has a conjugate relationship for the correction of the surface tilt of item 5.

Next, the operation of developing and transferring an image by the plural light beam scanning device thus constructed will be described.

First, the surface of the photoconductor 10 is uniformly charged to a predetermined potential V0 by the charger 11 (FIG. 3a). next,
The photoconductor 10 is main-scanned by the light beams A and B from the laser scanning unit 12. The main scan of the photoconductor 10 is
This is done as follows. First, the light beams A and B emitted from the semiconductor laser array 60 so as to correspond to the image to be recorded are made into parallel light beams by the collimator lens 33. The light beams A and B converted into parallel light beams are
By passing through the cylinder lens system 62, a linear image in the main scanning direction is formed on the deflection surface of the optical deflector 35. The light beams A and B formed on the deflecting surface are deflected by the optical deflector 35 at a constant angular velocity in the direction corresponding to the main scanning direction. After that, the light beams A and B that have passed through the fθ lens 36
Is reflected toward the scanning line position of the photoconductor 10 by the reflection mirrors 37 and 38, and the optical window 4 for sealing.
1 to form an image on the photoconductor 10 and main-scan the photoconductor 10 at a constant speed.

Here, the charge on the area on the photoconductor 10 irradiated with the light beams A and B is neutralized, and the charge on the area on the photoconductor 10 not irradiated with the light beam A or the light beam B remains as it is. become. As a result, a latent image Z having a potential difference H between the potential V0 in the region where the charge remains and the potential V1 in the region where the charge is neutralized is formed on the photoconductor 10.

The developing device 13 reverses the electric charge of the latent image Z while the developing bias V _B is applied, and the charged toner is sprayed onto the photoconductor 10. As a result, a toner image T corresponding to the latent image Z is formed (FIG. 3b).

After the transfer pretreatment corotron 15 aligns the polarities of the toner images T (FIG. 3c), the transfer corotron 16 collectively transfers the toner images T to the recording paper 17 side.

Next, a method of adjusting the distance between the light beams on the photoconductor of the plural light beam scanning apparatus thus configured to be a substantially target distance will be described.

First, the imaging magnification of the light emitting point of the semiconductor laser array 60, that is, the object point and the light beam incident point of the photoconductor 10, that is, the image point, is expressed by the following equation (9).

[0051]

[ _Formula 9] (f _col / f _cyl ) × M (9) where f _col is the focal length of the collimating optical system 61 and f
_cyl is the focal length of the cylinder lens system 62, and M is the imaging magnification in the direction orthogonal to the light deflection direction of the fθ optical system 36.

The interval S0 between the two light emitting points of the semiconductor laser array 60 and the interval S between the two light beams A and B on the photosensitive member 10.
1 is represented by the following equation (10).

[0053]

[ _Equation 10] S1 = (f _col / f _cyl ) × M × S0 (10) Here, for example, a 600 dot / inch light beam is obtained by using the semiconductor laser array 60 having a light emitting point interval S0 of 30 μm. In order to achieve the spacing, if an optical system of f _col = 10 [mm] f _cyl = 40 [mm] M = 0.529 is set, the relationship between the light beam spacing S1 on the photoconductor 10 and the light emitting point spacing S0 is set. Is as follows.

[0054]

[Equation 11] 63.5 [μm] = (40/10) × 0.529 × 30 [μm] (11) Even if the basic design of the optical system is set to satisfy the equation (11). , The light beam interval on the photoconductor is different from the target interval (here, 63.5 [μ
m]). To correct the deviation, it is sufficient to change any of the parameters on the right side of the equation (10), but it is difficult to change the light emitting point interval of the semiconductor laser array 60, and if f _col or M is changed. It also affects the light deflection direction. Therefore, in this embodiment, by changing f _cyl , the deviation of the light beam interval on the photoconductor 10 is corrected.

That is, in the equation (11), f _cyl is 1
When [mm] is changed, the distance between the light beams A and B on the photoconductor 10 changes by 1.587 [μm]. For example, the above formula (3)
Although the system is set as described above and the distance between the light beams A and B on the photoconductor 10 is set to 63.5 [μm], it is actually 60
When it is [μm], f _cyl is 3.5 / 1.587
It can be seen that it may be changed by 2.2 [mm].

Here, the focal length of the cylinder lens system 62 can be changed by changing the distance between the cylinder lenses 62A and 62B forming the cylinder lens system 62.

Table 1 shows a pair of negative and positive cylinder lenses 62.
Examples of A and 62B are shown. The focal length is 40 [mm]
In this case, the distance between the two lenses is 95.286 [mm].

[0058]

[Table 1]

The cylinder lens system 6 is changed by changing the distance between the cylinder lens 62A and the cylinder lens 62B.
Data of the focal length f _cyl of the cylinder lens system 62, the distance I between the cylinder lenses 62A and 62B, and the distance from the cylinder lens 62B to the optical deflector 35 when the focal length of 2 is varied from 35 to 45 [mm]. Are shown in Table 2 and FIG.

[0060]

[Table 2]

From these data, the cylinder lens system 6
The focal length f _{cyl of} 2 and the distance I between the cylinder lenses 62A and 62B can be approximated to a quadratic relationship represented by the following expression (12).

[0062]

I = 7.29196 × 10 ⁻² × f _cyl ² −8.73723 × f _cyl +328.1 002 (12) Therefore, first, it is obtained from the formulas (10) and (11). When the focal length of the cylinder lens system 62 is f _cyl = F so that the distance between the light beams on the photoconductor becomes the target distance, the distance I = between the cylinder lens 62A and the cylinder lens 62B obtained from the equation (12). The distance between the cylinder lenses 62A and 62B is changed so that it becomes I0.

From the above, first, the basic design of the optical system of the multiple light beam scanning device is set so as to satisfy the expression (11). That is, the distance L between the cylinder lens 62A and the cylinder lens 62B is set to 95.286 [mm] (that is, the focal length is 40 [mm]). The distance between the cylinder lens 62B and the optical deflector 35 is set to 8 so that an image is formed on the photoconductor.
It is set to 5.39 [mm].

If the distance between the light beams A and B on the photoconductor 10 deviates from the target distance in this state, the deviation of the distance between the light beams A and B on the photoconductor 10 from the target distance is considered. A change in the focal length of the cylinder lens system 62 to be increased or decreased is obtained. From the focal length f _cyl = F of the cylinder lens system 62 in consideration of the change amount, based on the equation (12), the cylinder lens 6 for _achieving this focal length F is obtained.
An interval I = I0 of 2A and 62B is obtained. The distance between the cylinder lens 62A and the cylinder lens 62B is
The cylinder lens holder 64 is positioned at the same position, and the cylinder lens holder 63 is changed by moving it so that the distance I0 between the cylinder lens 62A and the cylinder lens 62B obtained from the equation (12) is obtained.

However, if the focal length of the cylinder lens 62 is adjusted in this way and the position of the cylinder lens 62 with respect to the optical deflector 35 is kept at the same position, the diameter of the light beam on the photoconductor 10 becomes the target. It is larger than the light beam diameter. Therefore, it is necessary to adjust the light beam diameter on the photoconductor to the target light beam diameter.

Here, in order to make the light beam diameter on the photosensitive member the target light beam diameter, it is necessary to position the focal position of the cylinder lens 62 at the position of the light deflector 35. In this case, the relationship between the focal length f _cyl of the cylinder lens 62 and the focal position, ie, the optical deflector 35, and the focal length f _cyl of the cylinder lens 62 is shown in Table 2 and FIG. From the result, it can be expressed by the following equation (13).

[0067]

L = 5.539 + 0.75 × f _cyl (13) Therefore, based on the focal length f _cyl = F of the cylinder lens system 62 for making the interval of the light beams on the photoconductor the target interval. Therefore, from the above equation (13), the distance L = L0 from the cylinder lens 62B close to the optical deflector 35 to the optical deflector 35 can be obtained. Therefore, the distance between the cylinder lens 62A and the cylinder lens 62B obtained from the equation (12) remains unchanged, and the cylinder lens 62 obtained from the equation (13) is obtained.
The cylinder lens holder 64 is moved and fixed so that the distance L0 from B to the optical deflector 35 becomes.

As described above, the distance between the light beams on the photoconductor 10 can be set to the target distance, and the light beam diameter on the photoconductor 10 can be set to the target light beam diameter.

In this embodiment described above, one of the two cylinder lenses is moved to change the distance between the two cylinder lenses, and the light from the cylinder lens near the optical deflector of the two cylinder lenses is changed. Since the distance to the deflector is changed to adjust the light beam interval on the photoconductor and the light beam diameter, the two light beam intervals on the photoconductor can be easily adjusted and The light beam diameter can also be kept good.

In the embodiment described above, the cylinder lens holder 63 moves on the cylinder lens holder 64, but conversely, the cylinder lens holder 64 may move on the cylinder lens holder 63. . Also, after adjusting the distance between the two cylinder lenses,
Although the two cylinder lenses are moved together, the two cylinder lenses may be moved together, and then the cylinder lens on the photoconductor side may be fixed to adjust the distance between the two cylinder lenses.

Further, in the above-described embodiment, the two example cylinder lenses are a combination of negative and positive, but even if the combination of positive and positive or positive and negative is approximated by equations (12) and (13). Since the formula can be derived, a similar effect can be achieved.

That is, the positive cylinder lens 72A,
The 72B combination will be described with reference to Tables 3 and 4 and FIG. Table 3 shows an example of a pair of positive and positive cylinder lenses. When the focal length is 40 [mm], the distance between the two lenses is 39.812 [mm].

[0073]

[Table 3]

Data of the focal length f _cyl of the cylinder lens system, the distance I between the cylinder lenses 72A and 72B, and the distance L from the cylinder lens 72B to the light deflector 35 are shown in Table 4 below.

[0075]

[Table 4]

From these, these two cylinder lenses 7
2A and 72B, when the focal length is changed to 35 to 45 [mm], the cylinder lens 72A and the cylinder lens 72B
Distance I between the cylinder lens 72A and the cylinder lens 7
The relationship with the focal length f _cyl of the cylinder lens system combined with 2B can be approximated to the quadratic relationship represented by the following expression (14).

[0077]

I = −0.11424 × f _cyl ² + 13.68832 × f _cyl −324.931 3 (14) Further, the distance between the cylinder lens 72B close to the optical deflector 35 and the optical deflector 35. L and the focal length f of the cylinder lens system
The relationship with _cyl can be expressed by the following equation (15).

[0078]

L = −0.213 · f _cyl +35.824 (15) Further, the negative / positive combination can increase the optical path length when the focal length is short, and the positive / negative combination has the long focus. Since the optical path length can be shortened in the case of the distance, it is possible to adapt to the layout in the laser scanning unit 12 by selecting any one of the above combinations.

In the above-described embodiment, the relational expression between the focal length of the cylinder lens system and the distance between the cylinder lenses and the relational expression between the focal length of the cylinder lens system and the distance from the cylinder lens to the optical deflector are derived. In the experiment,
Although the experiment is conducted with the focal length of the cylinder lens system in the range of 35 to 45 [mm], the present invention is not limited to this.
It is also valid in a range other than 45 mm.

In the above-described embodiment, the cylinder lenses 62A and 62B shown in FIG. 1 are a set of one lens, but if the same effect is achieved, the number of lenses is two. Any number of sheets, such as three sheets, four sheets, ...

Further, in the above-described embodiment, an example in which the cylinder lens holder for mounting and fixing the cylinder lens is used as the first and second lens system fixing means has been described, but the present invention is not limited to this. Instead, the cylinder lens may be supported and fixed from the vertical upper side, the cylinder lens may be supported and fixed from the edge side, or the cylinder lens may be supported and fixed on the entire edge side.

Further, in the above-mentioned embodiment, the example in which the photosensitive member is moved to perform the sub-scan is described, but the present invention is not limited to this, and two light beams are moved or two light beams are combined. The sub-scan may be performed by moving the photoconductor.

Further, in the above-described embodiment, the semiconductor laser array has been described as an example of the light source for generating the two light beams, but the present invention is not limited to this, and two semiconductors for generating the light beams are used. A laser may be used.

Further, although the polygon mirror and the fθ lens are used in the above-mentioned embodiments, the present invention is not limited to this, and for example, a galvanometer mirror that vibrates sinusoidally may be used. In this case, the fθ lens is used instead. To use a lens having arc sine distortion.

[0085]

As described above, according to the present invention, the distance between the first lens system and the second lens system is changed, and the first lens system and the second lens system are integrally moved in the optical axis direction. By changing the distance from any one of the first lens system and the second lens system close to the main scanning means to the main scanning means,
Since the light beam interval is set to the target interval and the light beam diameter is set to the target light beam diameter, adjustment is performed to set the light beam interval on the photoconductor to the target interval and the light beam diameter on the photoconductor to the target light beam diameter. This has the effect that the adjustment can be easily performed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a multiple light beam scanning device according to an embodiment.

FIG. 2 is a cross-sectional view showing an arrangement of a collimator lens, two cylinder lenses, and two cylinder lens holders of the two cylinder lenses provided in the optical path from the semiconductor laser array to the deflector in the multiple light beam scanning device. Is.

FIG. 3 is an explanatory diagram showing the functions of development and transfer for image formation in the multiple light beam scanning device.

FIG. 4 is a diagram showing a relationship among a focal length of a cylinder lens system, a distance between cylinder lenses, and a distance from a cylinder lens to an optical deflector when a combination of negative and positive cylinder lenses is used.

FIG. 5 is a diagram showing a relationship among a focal length of a cylinder lens system, a distance between cylinder lenses, and a distance from a cylinder lens to an optical deflector when a combination of positive and positive cylinder lenses is used.

[Explanation of symbols]

 10 Photoconductor 11 Charging Corotron 12 Laser Scanning Unit 13 Developing Device 17 Recording Paper 35 Deflector 60 Semiconductor Laser 61 Collimator Lens 62A, 62B Cylinder Lens 63, 64 Cylinder Lens Holder

Claims (2)

[Claims] 1. A light source for irradiating a plurality of light beams, a light beam collimating means for collimating each of the plurality of light beams emitted from the light source, and a plurality of light beams from the light beam collimating means. Main scanning means for deflecting the light beam to main-scan the photosensitive member, sub-scanning means for relatively moving at least one of the plurality of light beams and the photosensitive member, and sub-scanning, the light source and the main scanning means. And a plurality of incident light beams arranged between and to form an image on the main scanning means,
It is composed of a first lens system and a second lens system each having a lens power only in the sub-scanning direction, the distance between the first lens system and the second lens system is adjustable, and the first lens system is also provided. And a first image forming means in which the second lens system is integrally movable in the optical axis direction, and a second image forming means for forming an image of the main-scanned light beam on the photoconductor.
When adjusting a plurality of light beam scanning devices provided with the image forming means, the distance between the first lens system and the second lens system is changed, and the first lens system and the second lens system are By moving the first lens system and the second lens system together in the optical axis direction.
By changing the distance from the lens system close to the main scanning means to the main scanning means in the lens system, the distance between the light beams on the photoconductor is adjusted to the target distance and A method for adjusting a plurality of light beam scanning devices, in which the light beam diameter is adjusted to a target light beam diameter. 2. The distance I between the first lens system and the second lens system is changed on the basis of I = af ² + bf + c, Of the two lens systems, the distance L from the lens system close to the main scanning means to the main scanning means
The method for adjusting a multiple light beam scanning device according to claim 1, wherein is changed based on L = d · f + e. However, a, b, c, d and e are constants, and f is the first
Is the focal length of the image forming means.