JP4495983B2 - Optical apparatus, optical scanning apparatus, image forming apparatus, and digital laboratory - Google Patents

Description

  The present invention relates to an optical device, an optical scanning device, an image forming apparatus, and a digital laboratory.

FIG. 7 is a diagram for explaining a scanning optical system of an optical scanning device having light sources of three colors.
In the figure, reference numeral 11 denotes a light source, 12 denotes a light modulator, 13 denotes a modulated light beam, 15 denotes a deflector, 17 denotes a surface tilt correction optical system, 18 denotes a polygon mirror, 19 denotes an fθ lens system, and 20 denotes an image. Each face is shown. Subscripts a, b, and c correspond to output light of the first color, the second color, and the third color, respectively. For example, the first color may be blue, the second color may be green, and the third color may be red.
For convenience of explanation, the operation will be described by focusing on the first color.
The parallel light beam emitted from the laser light source 11a and incident on the light modulation device 12a or the light beam close to parallel is modulated by the image information of the corresponding color to become a modulated light beam 13a, which is used for folding to reduce the size of the device. The light is reflected and deflected by the deflector 15a to be bent at an acute angle to become a light beam 13a ′, which is incident on one point of the polygon mirror 18 via the surface tilt correction optical system 17a.
The polygon mirror 18 rotates around the central axis at high speed. Strictly speaking, the incident point constantly fluctuates slightly. The light beam 13 a ′ reflected by the polygon mirror 18 reaches the image plane 20 via the fθ lens system 19. The reflection direction of the light beam 13a ′ constantly moves from one end of the imaging surface 20 to the other end by the rotation of the polygon mirror, and scans on the imaging surface. When a photosensitive object is placed on the imaging surface and moved at a predetermined speed in a direction perpendicular to the paper surface, an image corresponding to the first color or a latent image of the image is formed on the photosensitive object surface. The light beam scanning by the polygon mirror is called main scanning, and the movement of the photosensitive object is called sub scanning.
Image formation is similarly performed for the second color and the third color. However, since the light beams 13a ′, 13b ′, and 13c ′ of the respective colors have slightly different incident angles with respect to the polygon mirror 18, the timing of starting modulation by the light modulation device 12 is shifted in accordance with the difference in the angles. . Thus, a full-color image or latent image is formed on the photosensitive object.

When the light beam is modulated by the light modulation device 12, an unnecessary light beam, that is, 0th-order light, −1st-order light, or ± secondary light is emitted in the vicinity of the light beam 13 as + 1st-order light. There is. Since these light fluxes are not desired light fluxes, they cause image deterioration and are usually shielded by some method. These light beams are called off-axis light or unnecessary light.
A method has been proposed in which a lens system having positive or negative power is placed immediately after the light modulator to increase the angle (separation angle) in the traveling direction of unnecessary light, and only unnecessary light is blocked by a light shielding plate having an opening. (For example, refer to Patent Document 1).

Although omitted in the figure, normally, an opening (aperture) for regulating the beam diameter (light beam diameter) is provided somewhere between the light modulation device 12 and the surface tilt correction optical system 17. The reason why the aperture is provided is that a light beam with good coherence such as laser light is originally kept parallel for a relatively long distance when shaped into parallel light, but is always slightly diffused. Ambient light is blocked by the aperture to obtain a desired beam diameter. In order to ensure light shielding, a plurality of stages of light shielding may be performed.
In general, an opening is provided for each light beam. However, the light beams are often arranged close to each other in a narrow range, and there are cases where there is not enough space to provide individual openings.

Japanese Patent Laying-Open No. 2003-228034 (5th page, FIGS. 1 to 3)

The present invention eliminates unnecessary light from the three light beams and realizes a novel optical device for obtaining a desired beam system, and an optical scanning device, an image forming apparatus, and a digital laboratory using the optical device. The realization of

The optical device according to the present invention has the following: “Three light beams modulated as diffracted light of a predetermined order by image information are reflected and deflected by a deflector toward a common polygon mirror, scanned by the polygon mirror, and fθ lens In an optical scanning device that performs optical scanning by forming an image on a photosensitive object surface by a system, the optical device restricts the three light beams, and has the following characteristics (claim 1).
  That is, the optical device has first and second light shielding means.
  The “first light shielding means” is disposed on the optical path of the three modulated light beams toward the deflector that reflects and deflects these light beams toward the polygon mirror.
  The “second light shielding means” is disposed on the optical path of the three light beams that are reflected and deflected by the deflector toward the polygon mirror.
  The “first light shielding means” removes diffracted light other than a predetermined order associated with the three light beams as unnecessary light, and has a first light shielding member and a second light shielding member.
  The “first light shielding member” has an excessive opening (41) and an excessive opening (42), and the “second light shielding member” has an excessive opening (41 ′) and an excessive opening (42 ′).
  The excessive aperture (41) allows one light beam to pass to the deflector side.
  The excessive aperture (42) allows two light beams to pass to the deflector side and allows the light beam deflected by the deflector through the excessive aperture (41).
  The excessive openings (41 ', 42') allow the two light fluxes that have passed through the excessive opening (42) to the deflector side to individually pass to the deflector side.
  The three light beams pass through each of the above-described excessive apertures, so that unnecessary light (diffracted light other than a predetermined order, for example, if the modulated light beam used for optical scanning is + 1st order light, 0th order light and −1 Secondary light, ± secondary light, etc.) are removed.
  The “second light shielding means” regulates the light beam diameters of the three light beams reflected and deflected by the deflector, and includes a third light shielding member and a fourth light shielding member.
  The “third light shielding member” has an opening (61) and an excessive opening (62) with required dimensions, and the fourth light shielding member has an opening (61 ′) and an excessive opening (62 ′) with required dimensions. And
  These third and fourth light shielding members are positioned relative to each other so that the excessive opening (62) and the excessive opening (62 ') overlap in the vicinity of the light beam passing direction.
  One of the light beams reflected and deflected by the deflector passes through the opening (61) and the diameter of the light beam is regulated, and the other light beam reflected and deflected by the deflector passes through the opening (61 ') and passes through the light beam. The remaining one light beam whose diameter is restricted and reflected and deflected by the deflector passes through the excessive opening (62) and the excessive opening (62 ′), and “common” in the overlap of these excessive openings (62, 62 ′). The diameter of the light beam is regulated by the “opening”.

The optical device according to claim 1 is characterized in that the third and fourth light-shielding members are centered in the vicinity of the opening (61, 61 ') even after the position of the opening (61, 61') having a required dimension is determined. The position of the excessive opening (62, 62 ′) can be adjusted by the rotation of (2) .

The optical device according to claim 1 or 2, wherein the first light shielding member and the second light shielding member are “substantially identical to each other”, and the third light shielding member and the fourth light shielding member are “substantially identical to each other”. (Claim 3) .
Preferably, all of the three light beams in the optical device according to any one of claims 1 to 3 are laser light beams (claim 4).

The optical scanning device according to the present invention reads: “Three light beams modulated as diffracted light of a predetermined order by image information are reflected and deflected by a deflector toward a common polygon mirror, and scanned by the polygon mirror. 5. An optical scanning device that performs optical scanning by forming an image on a photosensitive object surface by an fθ lens system, and is an optical device that regulates three light beams, according to any one of claims 1 to 4. (Claim 5) .
The image forming apparatus of the present invention uses the optical scanning device according to claim 5 (claim 6) .
The digital laboratory of the present invention uses the optical scanning device according to claim 5 (claim 7) .

As described above, according to the present invention, it is possible to realize a novel optical device for removing unnecessary light and obtaining a desired beam system for three light beams, and a novel optical scanning device using this optical device. An image forming apparatus and a digital laboratory can be realized.

1 and 2 are diagrams for explaining an embodiment of the present invention. 1 is a perspective view, and FIG. 2 is a plan view.
In both figures, reference numeral 1 denotes a light source such as an LED or a laser, 2 denotes a light modulation device that gives color-by-color information to a light beam, 3 denotes a light beam modulated by the color information, 4 denotes a first light shielding means of the present invention, Reference numeral 5 denotes a deflecting element, 6 denotes a second light shielding unit of the present invention, 7 denotes a surface tilt correction optical system, 8 denotes a polygon mirror, 9 denotes an fθ optical system, and 10 denotes an imaging surface such as a photoreceptor.
Since the basic operation of this embodiment is the same as that of the prior art described with reference to FIG.
Each light beam 3 is in the form of a thin beam, and at first glance appears to be a parallel light beam, but is usually convergent light that converges toward the image plane. However, since the convergence angle is very small, it can be regarded as a parallel light beam as long as it is viewed in a short section in the traveling direction of the light beam. Although a plurality of light beams are configured to gather toward the polygon mirror 8, the convergence angle is considerably large, so that the light beams cannot be regarded as parallel light beams.

First, the first light shielding means will be described.
The light shielding member 4 is made of a thin plate material, and is composed of a light shielding portion 40 having two oblong long holes 41 and 42 and a leg portion 43 that is bent at right angles to the light shielding portion 40 and has one stop hole. Yes. The long holes 41 and 42 only have to be larger in at least one direction than the diameter of the light beam used, that is, the so-called beam diameter. Therefore, a circular opening larger than the beam diameter can be used. In the present invention, an opening satisfying such a condition is named an excessive opening.
Since the two long holes 41 and 42 are used as openings, the width is equal to the desired beam diameter, and the length is formed to be about 1.5 to 2 times the length. The stop hole is a hole for stopping the light shielding member 4 on a substrate (not shown), and is formed to be slightly larger than the diameter of the set screw, and a certain degree of freedom is given to the stop position with respect to the substrate.

Since two light shielding members 4 having a similar shape or the same shape are used, they are referred to as a first light shielding member 4 and a second light shielding member 4 ′ for convenience. Similar shapes and the same shape are collectively referred to as substantially the same shape.
A light beam 3a that exits from the light modulation device 2a and travels toward the deflector 5a passes through the long hole 41 of the first light shielding member 4. Light beams 3b and 3c from the light modulation device 2 to the deflectors 5b and 5c pass through the long hole 42 of the same light shielding member, and a total of three light beams 3a ′ from the deflector 5a to the surface tilt correction optical system 7a. Pass through. Therefore, the long hole 42 may be formed longer than the long hole 41.
A light beam 3c that passes through the elongated hole 42 of the first light shielding member 4 and travels toward the deflector 5c made of a reflecting mirror passes through the elongated hole 41 ′ of the second light shielding member 4 ′. Similarly, the second light shielding member The light flux 3b that passes through the long hole 42 of the first light shielding member 4 and travels toward the deflector 5b passes through the 4 'long hole 42'.

In FIG. 2, a light beam spreading around the light beam 3 emitted from the light modulation device 2 is indicated by a two-dot chain line. These light beams mean unnecessary light such as the above-described 0th-order light or −1st-order light.
The separation angle of unnecessary light is not so large, but if it is at a position sufficiently away from the light modulation device, unnecessary light can be blocked by allowing only a desired light beam to pass through the light shielding plate having an opening.
For example, regarding the light beam 3a, the light beam 3a itself passes through the long hole 41 of the light blocking member 4, but the light beam and unnecessary light having a certain separation angle cannot pass through the same long hole. The light beam 3 a that has passed through the long hole 41 is reflected by the deflector 5 a toward the polygon mirror 8, but unnecessary light is basically blocked by the light blocking member 4. Even if there is unnecessary light that passes through the long hole 42 of the light shielding member 4, the light beam does not enter the deflector 5a and, of course, does not enter the other deflectors 5b and 5c. There is no worry of being reflected.
The same applies to the other light beams 3b and 3c, and only the desired light beams 3b and 3c can pass through the opening of the light shielding member 4, and each unnecessary light is shielded by the light shielding member 4 or not. However, reflection by the deflector 5 does not occur, and therefore there is no fear of reflection toward the polygon mirror 8.

Next, the second light shielding means will be described. The second light shielding means is provided between the deflector 5 and the surface tilt correction optical system 7.
The light shielding member 6 is made of a thin plate material like the light shielding member 4, and includes a light shielding portion 60 </ b> A having a circular opening 61 and a first leg portion that is bent substantially at a right angle below the light shielding portion 60 </ b> A and has one stop hole 66. 63 and a connecting portion 60B extends in a direction substantially perpendicular to the surface of the light shielding portion 60A via a narrow flexible portion 65 that continues to the light shielding portion 60A, and further bends at a right angle to form a movable light shielding portion 60C. An elongated hole 62 that forms an excessive opening is provided at the center. A second leg portion 64 bent at a substantially right angle with respect to the connection portion 60B is provided at a lower portion of the connection portion 60B, and a stop hole 67 is provided at one location of the second leg portion 64. The stop hole 67 may be a hole having a sufficient size, or may be a long hole.
Since two light shielding members 6 having the same shape are used, they are referred to as a third light shielding member 6 and a fourth light shielding member 6 ′ for convenience.
The light beam 3 a passes through the circular opening 61 of the third light shielding member 6. The diameter of the circular opening is set to the required dimension. The light beam 3c ′ passes through the circular opening of the fourth light shielding member 6 ′. The elongated holes 62 and 62 'of the third and fourth light shielding members are arranged very close to each other, and the light beam 3b' passes therethrough.

FIG. 3 is a diagram for explaining the details of the second light shielding means. FIG. 4A is a plan view, FIG. 4B is a schematic view showing the relative movement of the elongated holes in perspective view, and FIG. 4C is a front view of the elongated holes.
It is assumed that the light shielding means shown in FIG. Since the stop hole 66 is formed so as to be larger than the screw diameter, the light shielding member 6 can be stopped on the substrate by easily matching the circular opening 61 of the light shielding part 60A with the light beam 3c ′. A set screw (not shown) is inserted into the stop hole 66 and fixed to the substrate. At this time, the position is fixed after adjusting the approximate position so that the light beam 3b ′ passes through the elongated hole of the movable light shielding portion 60C. However, the retaining hole 67 is not yet fixed with screws. The fourth light shielding member 6 ′ is fixed in the same manner. As a result, the long holes 62 and 62 ′ as the openings of the light shielding members 6 and 6 ′ face each other at positions close to each other, and the light beam 3b ′ passes through both the long holes.

  Since the light shielding member 6 is configured to bend slightly at the position of the flexible portion 65 provided relatively close to the circular opening 61, as shown in an exaggerated manner in FIG. As an approximate center, the movable light-shielding portion 60C can be moved in the direction of arrow A. Therefore, the elongated holes 62 and 62 ′ of the third and fourth light shielding members 6 and 6 ′ are moved in the lateral direction as shown in FIG. 5B, and the light beam 3b ′ is shown in FIG. In addition, it is positioned so that it becomes a circular opening when viewed from the traveling direction of the light beam so as to have a desired beam diameter, and the leg portions of the connecting portions 60B and 60B ′ are fixed to the substrate using the stop holes 67 and 67 ′. To do.

There is also a method in which the light shielding member 6 is not provided with the flexible portion 65. A stepped screw (not shown) is inserted into a stop hole 66 provided in the vicinity of the circular opening to stop the light shielding portion 60A. The height of the stepped portion of the stepped screw is set slightly larger than the thickness of the light shielding member 6. Therefore, the light shielding member 6 can be rotated around the stepped screw even after the stepped screw is stopped. Since the actual amount of rotation is very small, the light beam does not deviate from the circular opening 61. If the two light shielding members 6 and 6 ′ are both configured in this manner, the same effect as that obtained by providing the flexible portion 65 can be obtained. However, in this case, it is necessary to increase the position of the stop hole and the accuracy of the parts to some extent so that the circular openings 61 and 61 ′ can accurately shape a desired light beam.
As described above, the light beams 3a ′, 3b ′, and 3c ′ are shaped to a desired beam diameter by the second light shielding unit. Therefore, the first light shielding means can block off-axis light, and the second light shielding means can give a desired beam diameter to the light flux.

FIG. 4 is a diagram for explaining a reference example in which the light shielding member is moved in a direction perpendicular to the substrate and finely adjusted. FIG. 4A is an exploded perspective view, FIG. 4B is a plan view, and FIG. 4C is a front view in which a set screw is omitted.
In the figure, reference numerals 101 and 101 ′ denote light shielding member holding portions protruding from the substrate, 102 and 102 ′ denote light shielding members, and 103 and 103 ′ denote set screws.
Two light-shielding member holding portions 101 and 101 ′ protrude from each other with a light flux passage region therebetween. Since both have basically the same configuration, only one of them will be described below for simplification.
The light shielding member holding portion 101 has a projection 101a toward the light beam passage region side, and has a fulcrum portion 101b to be a rotation center portion of the light shielding member at the tip. A screw hole 101d is formed in a predetermined position on one surface 101c of the light shielding member holding portion 101. The fulcrum portion 101b protrudes to the side of the surface 101c having the screw hole 101d.

The light shielding members 102 and 102 'are substantially the same shape, and are both plate-like objects having three holes. Hereinafter, the light shielding member 102 will be described in detail.
The central hole 102a has a diameter approximately equal to the diameter of the light beam and allows the light beam 3a to pass therethrough, and one of the holes at both ends is an excessive opening 102b for allowing the light beam 3b to pass therethrough. The other of the holes at both ends forms a mounting screw hole 102c. A notch 102d is provided immediately below the central hole 102a. This portion is placed on the fulcrum 101b, and the screw hole 102c and the screw hole 101d are aligned and lightly screwed with the screw 103. The diameter of the screw hole 102c is formed larger than the screw diameter, and the light shielding member 102 can swing in the direction of arrow A with the contact point between the notch 102d and the fulcrum portion 101b as the rotation center. Due to this swing, the excessive opening 102b moves up and down relatively large, but the central hole 102a does not move much because it is near the center of rotation. Therefore, the position of the excessive opening can be slightly adjusted up and down depending on how the screw hole 102c is fixed to the set screw. When the adjustment is completed, the light shielding plate 102 is fixed by tightening the screw 103.
The light shielding member holding portion 101 ′ and the light shielding member 102 ′ have the same configuration as described above. The central hole 102′a allows the light beam 3c to pass therethrough, and the excessive opening 102′b allows the light beam 3b to pass therethrough. That is, the excessive apertures 102b and 102b ′ are arranged at positions that allow the same light beam 3b to pass therethrough, and the light beam 3b passes through both apertures to block off-axis light or perform beam shaping.

FIG. 5 is a reference diagram showing an example of the arrangement of the light shielding members for the four light beams. FIG. 4A is a perspective view, and FIG. 4B is a plan view.
In the figure, reference numerals 201 and 201 ′ denote light shielding members.
Photosensitive materials used in digital laboratories have been conventionally only compatible with three primary colors, but in recent years, those corresponding to four colors including certain intermediate colors have begun to be used. As an apparatus corresponding to such a photosensitive material, an apparatus using four independent light beams is required.
Since the light shielding members 201 and 201 ′ have substantially the same shape, the light shielding member 201 will be described.
The light shielding member 201 includes a light shielding portion 201a having three holes and a base portion 201b having mounting screw holes to be attached to the substrate. Of the three holes of the light shielding portion 201a, one end hole forms an opening 201c having a required diameter, and the center hole 201d and the other end hole 201e both form an excessive opening. Although not shown, the hole 201e may be formed in a so-called notch hole having a release portion with respect to the lateral end of the light shielding portion 201a.
The light shielding member has a mounting screw hole 201f having a hole diameter slightly larger than the diameter of the mounting screw so that the orientation and position of the surface of the light shielding portion 201a can be slightly adjusted as indicated by arrows A and B. It has become.

It is assumed that the four light beams 3a to 3d are not parallel to each other.
The opening 201c of the light shielding member 201 allows the light beam 3a to pass, the central excessive opening 201d allows the light beam 3b, and the other excessive opening 201e allows the light beam 3c to pass therethrough. The opening 201′c of the light shielding member 201 ′ allows the light beam 3d to pass therethrough, the central excessive opening 201′d allows the light beam 3c to pass, and the other excessive opening 201′e allows the light beam 3b to pass therethrough. That is, the light beams 3b and 3c pass through the excessive openings of both the light shielding members 201 and 201 ′.
The surface of the light shielding part 201a of the light shielding member 201 is arranged so as to be substantially perpendicular to the light beam 3a, and the surface of the light shielding part 201'a of the light shielding member 201 'is arranged so as to be substantially perpendicular to the light beam 3d. Since the outer light beams 3a and 3d are not parallel, the light shielding portions 201a and 201′a of both light shielding members are not parallel and are arranged with a slight crossing angle.
This configuration can be used to block off-axis light, or to some degree of beam shaping. In the case of shielding off-axis light, it is sufficient that the light beams 3a to 3d surely pass through a predetermined hole. In adjusting the beam shaping, care is taken to ensure that the light shielding member 201 allows the light beam 3a and the light shielding member 201 'to pass the light beam 3d, and the direction and position of the surface of the light shielding portion are slightly changed so that the light beams 3b and 3c are desired. Try to be close to the diameter.

FIG. 6 is a perspective view showing an example of an optical scanning device to which the present invention is applied.
In the figure, reference numeral 12 denotes a cover glass of the polygon mirror, 13, 14 and 15 denote lens elements constituting the fθ optical system, and 17, 18 and 19 denote scanning timing detection optical systems, respectively.
Since the basic operation of the optical scanning device has already been described with reference to FIG. 7, overlapping will be avoided, but the portions not touched in FIG. 7 will be described briefly.
In FIG. 6, the polygon mirror 8 rotates in the arrow B direction. The unmodulated light beam deflected by the reflecting surface of the polygon mirror 8 is first deflected by the reflecting mirror 17 and detected by the color-specific sensor 19 through the imaging lens 18. Since the light beam reaches a predetermined scanning region of the imaging surface 10 after a predetermined time from this detection signal, a modulation signal corresponding to the image is given to the light modulation element 2 in accordance with the timing. The modulated light beam 3 is scanned on the image plane 10 in the direction of arrow C.
A photosensitive object placed in alignment with the image plane 10 is moved in a direction perpendicular to the arrow C by a device (not shown), and so-called sub-scanning is performed. As the photosensitive object, for example, silver salt color photographic paper can be used.

It is a figure for demonstrating embodiment of this invention. It is a figure for demonstrating embodiment of this invention. It is a figure for demonstrating the detail of a 2nd light-shielding means. It is a figure for demonstrating the example which moves a light shielding member to the direction perpendicular | vertical to a board | substrate, and performs fine adjustment. It is a figure which shows the example of arrangement | positioning of the light shielding member with respect to four light beams. It is a perspective view which shows an example of the optical scanning device to which this invention is applied. It is a figure for demonstrating the scanning optical system which has a light source of three colors.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Light modulation apparatus 3 Modulated light beam 4 1st light shielding means 6 2nd light shielding means 8 Polygon mirror 9 f (theta) optical system 10 Imaging surface

Claims (7)

Three light beams modulated as diffracted light of a predetermined order by image information are reflected and deflected by a deflector toward a common polygon mirror, scanned by the polygon mirror, and a photosensitive object by an fθ lens system. In an optical scanning device that forms an image on a surface and performs optical scanning, the optical device regulates the three light beams,
  A first light-shielding means arranged on an optical path toward the deflector for three modulated light beams to reflect and deflect these light beams toward the polygon mirror;
  A second light shielding means disposed on the optical path of the three light beams reflected and deflected by the deflector and directed to the polygon mirror,
  The first light shielding means removes diffracted light other than a predetermined order accompanying the three light beams as unnecessary light, and includes a first light shielding member and a second light shielding member,
  The first light shielding member has an excessive opening (41) and an excessive opening (42), and the second light shielding member has an excessive opening (41 ') and an excessive opening (42'),
  The excessive aperture (41) allows one light beam to pass to the deflector side,
  The excessive aperture (42) allows two light beams to pass to the deflector, and allows the light beam deflected by the deflector through the excessive aperture (41) to pass through.
  The excessive apertures (41 ', 42') allow the two light beams that have passed through the excessive aperture (42) to the deflector side to individually pass to the deflector side,
  The second light shielding means regulates the beam diameter of the three light beams reflected and deflected by the deflector, and includes a third light shielding member and a fourth light shielding member,
  The third light shielding member has an opening (61) and an excessive opening (62) with required dimensions, and the fourth light shielding member has an opening (61 ') and an excessive opening (62') with required dimensions. And
  The third and fourth light shielding members are positioned with respect to each other such that the excessive opening (62) and the excessive opening (62 ') overlap in the vicinity of the light beam passage direction,
  One of the light beams reflected and deflected by the deflector passes through the opening (61) and the diameter of the light beam is regulated, and the other light beam reflected and deflected by the deflector passes through the opening (61 '). The remaining one light beam whose diameter is regulated and reflected and deflected by the deflector passes through the excessive opening (62) and the excessive opening (62 '), and the excessive openings (62, 62') overlap. The optical device is characterized in that the diameter of the light beam is regulated by a common opening in the optical device. The optical device according to claim 1.
Even after the positions of the openings (61, 61 ′) having the required dimensions are determined, the third and fourth light shielding members are excessively opened (by the rotation around the openings (61, 61 ′)). 62, 62 ') is configured to be adjustable . The optical device according to claim 1 or 2,
The first light shielding member and the second light shielding member are substantially identical to each other;
An optical device, wherein the third light-shielding member and the fourth light-shielding member are substantially identical to each other . The optical device according to any one of claims 1 to 3,
  An optical device characterized in that all three light beams are laser light beams. Three light beams modulated as diffracted light of a predetermined order by image information are reflected and deflected by a deflector toward a common polygon mirror, scanned by the polygon mirror, and a photosensitive object by an fθ lens system. An optical scanning device that forms an image on a surface and performs optical scanning,
An optical scanning device using the optical device according to any one of claims 1 to 4 as an optical device for regulating three light beams . An image forming apparatus using the optical scanning device according to claim 5 . A digital laboratory using the optical scanning device according to claim 5 .

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