JPH10177143A - Optical scanning device - Google Patents

Abstract

(57) [Summary] The present invention provides a mechanical and electrical connection by using a common optical housing even when the print speed and resolution change, and by not having a movable part or an adjustment / change means. It is an object to realize an advantageous and low-cost optical scanning device. According to the present invention, a light source unit and first optical systems for guiding a light beam from the light source unit to an optical deflector are provided.
11c, an optical deflector 12 for scanning the light beam,
A second optical system 13 for condensing the scanned light beam as a light spot on the surface 14 to be scanned; a light detecting unit 17 for generating a synchronization signal for determining a writing start position; In the optical scanning device including the third optical system 15 leading to the detection unit, the holding mechanisms 18a, 18b, and 18c of the first optical system, the second optical system, and at least one optical element 11b that constitutes the third optical system are provided. A plurality of optical elements are arranged in accordance with the mounting position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device used as an image writing means in an image forming apparatus such as a laser printer, a digital copying machine, a laser facsimile and the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a laser printer, a digital copying machine, and a laser facsimile, a laser beam is converted into a minute light spot on a surface to be scanned such as a photosensitive member as a means for writing an image on the photosensitive member. An optical scanning device that writes an image (electrostatic latent image) by modulating the intensity according to the image signal while scanning the light spot in the main scanning direction is used as the optical scanning device.
For example, a substantially parallel light beam from a laser light source such as a semiconductor laser is guided to an optical deflector composed of a rotating polygon mirror or the like via an optical system such as a cylindrical lens, and the light deflector deflects the light beam to form a deflected light beam. There is a configuration in which an image is formed on a surface to be scanned by an image optical system.

In such an optical scanning device, the density of the writing laser light at the image forming position can be changed without changing the light use efficiency of the laser light source, and the setting of the writing time and the like are included. There has been proposed a device provided with a means capable of adjusting a writing operation to a condition set by a user (see Japanese Patent Application Laid-Open No. 4-194813). And, in the technology described in the above publication, as means for selecting the density of the writing laser light,
As shown in the following 1 to 4, means for switching the spot diameter of the light spot in the sub-scanning direction are provided. 1. The means for switching the spot diameter in the sub-scanning direction has a structure in which a cylindrical lens is replaced. 2. The means for switching the spot diameter in the sub-scanning direction has a structure in which the size of the aperture stop is changed to change the spot diameter in the main scanning direction. The emission output of the laser light source is adjusted in accordance with the change in the aperture stop. Switch. 3. The means for switching the spot diameter in the sub-scanning direction has a structure in which the size of the aperture stop is changed to vary the spot diameter in the sub-scanning direction. Switch. 4. The means for switching the spot diameter in the sub-scanning direction has a structure in which the size of the aperture stop is changed so that the spot diameters in the main and sub-scanning directions are made different. Switch the light emission output.

Further, an optical element such as a cylindrical lens can be attached to a case with a simple structure with high accuracy, and the cylindrical portion of the cylindrical lens is rotatable as an optical scanning device that can easily adjust the bus and adjust the focal position. In addition, a device having a holding portion for slidably holding in the optical axis direction has been proposed (see Japanese Patent Application Laid-Open No. 4-178668).

[0005]

The printing speed and resolution of laser printers and the like tend to increase year by year, and it is necessary to change the amount of light and the diameter of a light spot according to the printing speed and resolution. Conventionally, the arrangement of the optical elements differs depending on the printing speed and the resolution, so that the optical housing has to be designed each time.
Alternatively, a method of mechanically and electrically switching the arrangement of the optical elements and the like by using a slide mechanism or the like is used.

The above-mentioned Japanese Patent Application Laid-Open No. 4-194,813 proposes a means in which a plurality of cylindrical lenses are arranged in advance and a slide mechanism is provided for selection in order to switch the light spot diameter. In addition, a method has been proposed in which the aperture stop is changed, and the emission output of the laser light source is changed accordingly. On the other hand, when a cylindrical lens or the like is attached, there is a method of adjusting by attaching a rotation or slide mechanism as disclosed in Japanese Patent Application Laid-Open No. 4-178668. However, in the optical scanning device,
Providing a movable part such as a slide mechanism and adjustment / change means increases the number of parts and the difficulty of assembling, leading to a cost increase.

The present invention has been made in view of the above circumstances. In the present invention, the optical system of the optical scanning device is provided with a plurality of holding mechanisms in advance, so that even if the printing speed or the resolution changes, the optical scanning device has a common function. It is an object of the present invention to realize a low-cost optical scanning device that is mechanically and electrically advantageous by using no optical housing and having no movable part or adjustment / change means.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a light source unit, a first optical system for guiding a light beam from the light source unit to an optical deflector, and a scanning unit for scanning the light beam An optical deflector for performing scanning, a second optical system for condensing the scanned light beam as a light spot on the surface to be scanned, a light detecting unit for generating a synchronization signal for determining a writing start position, and And a holding mechanism for holding at least one optical element constituting the first optical system, the second optical system, and the third optical system. A plurality of elements are arranged according to the mounting positions of the elements.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the plurality of holding mechanisms are all configured to have the same structure.

In a third aspect of the present invention, in addition to the configuration of the first aspect, the plurality of holding mechanisms are configured such that at least one of the holding mechanisms has a different configuration.

According to the fourth aspect of the present invention, in addition to the configuration of the second or third aspect, a plurality of holding mechanisms are provided.
The configuration is such that the optical systems are arranged in parallel in the optical axis direction.

According to a fifth aspect of the present invention, in addition to the configuration of the fourth aspect, the plurality of holding mechanisms are configured to be holding mechanisms of an optical element constituting the first optical system.

According to a sixth aspect of the present invention, in addition to the configuration of the fifth aspect, the first optical system has an aperture function, and the aperture diameter is determined according to the mounting position of the optical element.

According to a seventh aspect of the present invention, in addition to the structure of the fifth or sixth aspect, the plurality of holding mechanisms are provided.
The light beam coupled from the light source unit is restricted by the aperture function, and the structure is a holding mechanism of a cylindrical lens of the first optical system for forming an elongated linear image near the deflection reflecting surface of the optical deflector.

According to an eighth aspect of the present invention, in addition to the configuration of the sixth or seventh aspect, the aperture diameter is determined so as to change the amount of light while keeping the light spot diameter on the surface to be scanned constant. did.

According to a ninth aspect of the present invention, in addition to the configuration of the sixth or seventh aspect, the aperture diameter is determined so as to change the light spot diameter while keeping the amount of light on the surface to be scanned constant. did.

According to the tenth aspect of the invention, in addition to the configuration of the sixth or seventh aspect, the aperture diameter is determined so as to change the light quantity and the light spot diameter on the surface to be scanned.

According to the eleventh aspect of the present invention, in addition to the configuration of the seventh aspect, the plurality of holding mechanisms are composed of three, and the first holding mechanism is different in order from the light source side,
The second holding mechanism and the third holding mechanism are configured to be equal.

According to a twelfth aspect of the present invention, in addition to the configuration of the seventh aspect, the plurality of holding mechanisms are three in number, and the first holding mechanism and the second holding mechanism are equal in order from the light source side. The third holding mechanism has a different configuration.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 4 is a schematic configuration diagram showing an example of an optical scanning device according to the present invention, and includes a light source 10, an optical deflector 12, first to third optical systems 11a, 11b, 13, 1.
5 shows an example of arrangement of components such as the light detection unit 17 on a scanning plane. The scanning plane is a plane parallel to the optical axis of the optical system and the scanning direction (main scanning direction) of the light beam by the optical deflector 12.

In FIG. 4, "semiconductor laser (LD)"
The divergent luminous flux emitted from the light source 10 is coupled by the coupling lens 11a and converged only by the cylindrical lens 11b in a scanning vertical direction (a direction perpendicular to the scanning plane, also referred to as a sub-scanning direction). Is formed as a “line image long in the scanning direction” in the vicinity of the deflecting reflection surface 12 a of the optical deflector 12. The coupling lens 11a and the cylindrical lens 11b constitute a "first optical system".

The light emitted from the first optical system may be a "parallel light", a "weakly divergent light" or a "weakly convergent light" in the scanning direction. The light deflector 12 rotates at a constant speed in the direction of the arrow in the figure, and the light beam reflected by the deflecting / reflecting surface 12a becomes a deflected light beam and is deflected clockwise in FIG. This deflected light beam enters a second optical system 13 constituted by a scanning image forming lens such as an fθ lens, and is formed as a minute light spot on a scanned surface 14 such as a photoconductor by the image forming action of the second optical system 13. Collect light. The light spot is deflected by the deflected light beam,
The scanned surface 14 is optically scanned by moving on the scanned surface 14 in the scanning direction. The second optical system 13 has a function of making the movement of the light spot on the scanned surface 14 uniform. The line image formed by the cylindrical lens 11b of the first optical system is formed near the deflecting and reflecting surface 12a of the optical deflector 12, and
Since the optical system 13 focuses the deflected light beam on the surface to be scanned 14 as a light spot, the optical scanning device of FIG.
It has a function to correct "trouble" in. Although the second optical system 13 has a single lens configuration in the embodiment of FIG. 4, it may be composed of two or more lenses.

The light beam deflected by the light deflector 12 is incident on a third optical system 15 prior to optical scanning of the surface 14 to be scanned, and is acted on by the third optical system 15 to form a light detector 17 using a “light receiving element”. Is collected. The light detection unit 17 emits a detection signal when detecting the deflected light beam, and based on the detection signal, issues a synchronization signal for determining the “writing start position A” by optical scanning.

In the following, a case where a plurality of cylindrical lens holding mechanisms constituting the first optical system are arranged will be described as an example.

As a method for improving the print speed and resolution without changing the light output intensity (hereinafter, referred to as LD power) of the semiconductor laser and the sensitivity of the photosensitive member, the following means are possible. In general, when the print speed is improved (the resolution is constant, that is, the light spot diameter is also constant), the rotation speed of the optical deflector 12 increases, and the required light amount on the surface to be scanned 14 (on the photoconductor) increases. That is, it is necessary to increase the LD power. But,
In order to secure the required light amount without changing the LD power, move the cylindrical lens closer to the light source,
The aperture diameter is increased so that the numerical aperture (NA) of the light beam incident on the optical deflector is kept constant (the light spot diameter is kept constant). That is, FIG. 5 is a sectional view of a main part of the optical scanning device in the sub-scanning direction. As shown in FIG. 5A, an aperture (aperture) 11 is provided in front of the cylindrical lens 11b.
In order to improve the printing speed by providing c, the position of the cylindrical lens 11b is made closer to the light source side as shown in FIG. 4B, and the numerical aperture (N) of the light beam entering the deflecting / reflecting surface 12a of the optical deflector is set. .A.) Is kept constant (the light spot diameter is kept constant) by increasing the opening diameter of the opening 11c (θ is equal, d <d '), so that the required light amount is secured without changing the LD power. can do.

On the other hand, in general, when the resolution is to be improved (the printing speed is constant), it is necessary to reduce the diameter of the light spot, and for that purpose, the numerical aperture (NA) of the light beam incident on the optical deflector must be increased. I just need. As a means,
Keeping the aperture diameter constant (the amount of light on the surface to be scanned is constant)
Then, the cylindrical lens is brought closer to the optical deflector. That is, FIG. 6 shows a cross-sectional view of a main part of the optical scanning device in the sub-scanning direction. In the case where an opening 11c is provided in front of the cylindrical lens 11b as shown in FIG. The opening diameter d of the opening 11c as shown in FIG.
By keeping the position of the cylindrical lens 11b close to the deflecting / reflecting surface 12a of the optical deflector while keeping
The light spot diameter can be reduced while the light amount on the surface to be scanned is constant (d is equal, and θ <θ ′).

Further, the LD power and the sensitivity of the photosensitive member may be changed according to the print speed and the resolution. In that case, it is necessary to change the required light amount and light spot diameter on the photoconductor (scanned surface), and it is necessary to set the opening diameter of the opening and the position of the cylindrical lens to be optimal.

When the position of the cylindrical lens is changed, in order to form a "long line image in the scanning direction" in the vicinity of the deflecting and reflecting surface of the optical deflector, the radius of curvature of the cylindrical lens changes according to the position. In other words, the cylindrical lenses in each arrangement are different. At this time, when the cylindrical lenses are made of the same material, it is needless to say that it is optimal to make the same external shape, and it is desirable that the holding mechanism has the same configuration (shape, constituent member, material, etc.). Further, when the cylindrical lenses are made of different materials, that is, made of glass and plastic, the external shape of the cylindrical lens may be different. Therefore, it is desirable that the holding mechanism has a configuration (shape, constituent member, material, etc.) suitable for each.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the optical scanning device according to the present invention will be described. FIG. 1 is a schematic configuration diagram of an optical scanning device showing an embodiment of the present invention. The basic configuration and operation are the same as those of the optical scanning device shown in FIG. It is a member. In the optical scanning device shown in FIG. 1, the first optical system includes a coupling lens 11a, a cylindrical lens 11b, and an aperture (aperture) 11c. Mechanisms 18a, 18
b, 18c are arranged. These three holding mechanisms 18
a, 18b, 18c all have the same configuration (shape, constituent members,
The first holding mechanism 18a is arranged in parallel in the optical axis direction of the first optical system from the light source 10 side.
The second holding mechanism 18b and the third holding mechanism 18c are arranged in this order. Therefore, the cylindrical lens 11b is held by any of the three holding mechanisms 18a, 18b, 18c in the optical axis direction according to the print speed, resolution, and the like.

The diameter of the opening 11c of the first optical system is determined in accordance with the mounting position of the cylindrical lens 11b. For example, at a normal printing speed and resolution, the cylindrical lens 11b is located at the center of the first lens. Although it is attached to the second holding mechanism 18b, when the printing speed is to be improved (the resolution is constant, that is, the light spot diameter is also constant), the cylindrical lens 11b is attached to the first holding mechanism 18a on the light source side, and the scanning surface The aperture diameter of the opening 11c is determined so as to change the amount of light while keeping the diameter of the light spot on the aperture 14 constant. That is, when increasing the light amount, the aperture diameter is increased. When the resolution is to be improved (the print speed is constant), the cylindrical lens 11b is attached to the third holding mechanism 18c on the optical deflector 12 side, and the light spot on the scanned surface 14 is kept constant while the light spot is kept constant. The opening diameter of the opening 11c is determined so as to change the diameter. In this case, since the light amount is constant, the aperture diameter is also constant. Further, one of the three holding mechanisms 18a, 18b, 18c is selected so that the position of the cylindrical lens 11b is optimized according to the printing speed and the resolution, and the light amount and the light amount on the surface 14 to be scanned are selected accordingly. The diameter of the opening 11c is determined so as to change the light spot diameter.

As described above, the cylindrical lens 11b
Is changed, the deflection reflection surface 1 of the optical deflector 12 is changed.
In order to form a “long line image in the scanning direction” near 2a, the radius of curvature of the cylindrical lens 11b changes according to the position, and the cylindrical lens 11b in each arrangement is different. In this case, when the cylindrical lens 11b is made of the same material, it is optimal to make the cylindrical lens 11b with the same outer shape.
The configuration (shape, constituent member, material, etc.) of 18b, 18c can be the same. However, when made of different materials, that is, made of glass and plastic, the outer shape may be different. Therefore, it is preferable to use a holding mechanism suitable for each of them. At least one of the plurality of holding mechanisms has a different configuration. Of the holding mechanism.

FIGS. 2 and 3 show a plurality of holding mechanisms arranged for the cylindrical lens of the first optical system.
An embodiment having at least one holding mechanism having a different configuration is shown.

The optical scanning device shown in FIG. 2 is arranged in the order of the first holding mechanism 18a, the second holding mechanism 18b, and the third holding mechanism 18c from the light source 10 side by side in the optical axis direction of the first optical system. Of the two holding mechanisms, the configuration of the first holding mechanism 18a is different from the others, for example, is a configuration corresponding to a glass cylindrical lens, and the second and third holding mechanisms 18b, 1
This is an example of a case where the configuration of FIG. 8c is the same and the configuration corresponds to a plastic cylindrical lens. Contrary to the above, the first holding mechanism 18a has a configuration corresponding to a plastic cylindrical lens, and the second and third holding mechanisms 1
8b and 18c may have a configuration corresponding to a glass cylindrical lens.

The optical scanning device shown in FIG. 3 has a first holding mechanism 18a, a second holding mechanism 18b, and a third holding mechanism 18c arranged in this order from the light source 10 side by side in the optical axis direction of the first optical system. Of the two holding mechanisms, the first and second holding mechanisms 18
a and 18b have the same configuration, for example, a configuration corresponding to a glass cylindrical lens.
This is an example of a case where the configuration of c is different from the others and is a configuration corresponding to a plastic cylindrical lens. Also,
Contrary to the above, the first holding mechanism 18a and the second holding mechanism 1
8b may be a configuration corresponding to a plastic cylindrical lens, and the third holding mechanisms 18b and 18c may be a configuration corresponding to a glass cylindrical lens.

In the above embodiment, the holding mechanism of the cylindrical lens of the first optical system has been described as an example. However, the scanning image forming the second optical system 13 by the optical scanning device shown in FIGS. A plurality of holding mechanisms for holding the lens may be arranged in parallel in the optical axis direction of the second optical system. In this case, the mounting position of the scanning imaging lens can be changed by selecting the holding mechanism, It is possible to change the image formation state on the scanned surface 14, that is, the diameter of the light spot.

Further, in the optical scanning device shown in FIG. 1, the holding mechanism 16 for holding the optical element constituting the third optical system 15 is connected to the third optical system 15 by the third mechanism.
A plurality of optical elements are arranged in parallel in the optical axis direction of the optical system, and according to a change in the mounting position of the optical element 11b constituting the first optical system,
A configuration in which the mounting position of the optical element that forms the third optical system 15 may be changed.

[0037]

As described above, in the optical scanning device according to the first aspect, the holding mechanism for at least one optical element constituting the first optical system, the second optical system, and the third optical system includes the optical mechanism. Since a plurality of elements are arranged according to the mounting positions of the elements, the optical housing can be shared even if the printing speed or the resolution changes, and the cost can be reduced.

In the optical scanning device according to the second aspect, the first aspect is as follows.
In addition to the configuration and the effect of the above, the plurality of holding mechanisms are configured to have the same configuration (shape, constituent member, material, etc.), so that when the optical elements have the same shape, When the holding mechanism has the same configuration as described above, the design of the optical housing is easy and simplified.

In the optical scanning device according to the third aspect, the first aspect is as follows.
In addition to the configuration and effect of the above, since the plurality of holding mechanisms are configured to include at least one holding mechanism having a different configuration, when the optical element has a different shape, at least one holding mechanism is provided as described above. By using a different mechanism, the mechanism can be optimized according to the optical element using the holding mechanism.

In the optical scanning device according to the fourth aspect, in the second aspect,
In addition to the configuration and effect of the third aspect, the plurality of holding mechanisms are arranged in parallel in the optical axis direction of each optical system, so that the layout of the holding mechanisms is facilitated. Can be.

According to the optical scanning device of the fifth aspect, in the fourth aspect,
In addition to the structure and effect of the first embodiment, since the plurality of holding mechanisms are configured to be holding mechanisms for the optical elements constituting the first optical system, means for effectively changing the light amount and the light spot diameter are provided. Can be obtained.

In the optical scanning device according to the sixth aspect, in the fifth aspect,
In addition to the configuration and the effect of the first embodiment, the first optical system has an aperture function, and the aperture diameter is determined according to the mounting position of the optical element. , An optimal opening diameter can be obtained.

In the optical scanning device according to the seventh aspect, the fifth aspect
In addition to the configuration and effect of the sixth aspect, the plurality of holding mechanisms limit the light flux coupled from the light source unit by the opening function, and form an elongated linear image near the deflection reflection surface of the optical deflector. Since the first optical system is configured to be a holding mechanism of the cylindrical lens of the first optical system, it is possible to obtain a means for changing the light amount and the light spot diameter most effectively.

In the optical scanning device according to the eighth aspect, the sixth aspect of the present invention provides the optical scanning device.
Or, in addition to the configuration and effect of 7, in addition to the configuration in which the aperture diameter is determined so as to change the light amount while keeping the light spot diameter on the surface to be scanned constant, when the resolution is fixed, printing is performed. Means for improving the speed can be obtained.

In the optical scanning device according to the ninth aspect, the sixth aspect of the present invention provides the optical scanning device.
Or, in addition to the configuration and effect of 7, since the aperture diameter is determined so as to change the light spot diameter while keeping the light amount on the surface to be scanned constant, when the print speed is fixed, Means for improving the resolution can be obtained.

According to a tenth aspect of the present invention, in addition to the configuration and effect of the sixth or seventh aspect, the aperture diameter is determined so as to change the light amount and the light spot diameter on the surface to be scanned. Therefore, means for optimizing the light amount and the light spot diameter with respect to the printing speed and the resolution can be obtained.

In the optical scanning device according to the eleventh aspect, in addition to the configuration and effect of the seventh aspect, the plurality of holding mechanisms are composed of three, and the first holding mechanism is different in order from the light source side. , The second holding mechanism and the third holding mechanism have the same configuration, so that the first holding mechanism is a glass cylindrical lens (or a plastic cylindrical lens).
Means for making the holding mechanism, and the second and third holding mechanisms a holding mechanism for a plastic cylindrical lens (or a glass cylindrical lens) can be obtained.

According to a twelfth aspect of the present invention, in addition to the configuration of the seventh aspect, the plurality of holding mechanisms are composed of three, and the first holding mechanism and the second holding mechanism are arranged in order from the light source side. Are equal and the third holding mechanism is different, so that the first and second holding mechanisms are holding mechanisms for glass cylindrical lenses (or plastic cylindrical lenses), and the third holding mechanism is for plastic cylindrical lenses (or It is possible to obtain means for holding a glass cylindrical lens).

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical scanning device showing one embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a main part of an optical scanning device according to another embodiment of the present invention.

FIG. 3 is a schematic structural view of a principal part of an optical scanning device showing still another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram illustrating an example of an optical scanning device according to the present invention.

FIG. 5 is a diagram showing a cross section of a main portion of the optical scanning device according to the present invention in the sub-scanning direction, and is an explanatory diagram of a cylindrical lens position and an aperture diameter when changing the light amount while keeping the light spot diameter constant. is there.

FIG. 6 is a diagram illustrating a cross section of a main part of the optical scanning device according to the present invention in the sub-scanning direction, and is an explanatory diagram of a cylindrical lens position and an aperture diameter in a case where a light spot diameter is changed while a light amount is kept constant. is there.

[Explanation of symbols]

10: Light source (semiconductor laser) 11a: Coupling lens (optical element of first optical system) 11b: Cylindrical lens (optical element of first optical system) 11c: Opening (optical element of first optical system) 12: Light deflection Device 12a: Deflection / reflection surface 13: Second optical system 14: Surface to be scanned 15: Third optical system 16: Holding mechanism of third optical system 17: Photodetector 18a: First holding mechanism of cylindrical lens 18b: Cylindrical lens Second holding mechanism 18c: Third holding mechanism of the cylindrical lens

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Iwao Matsumae 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd.

Claims (12)

[Claims] 1. A light source unit, a first optical system for guiding a light beam from the light source unit to an optical deflector, an optical deflector for scanning the light beam, and a light beam for scanning the scanned light beam on a surface to be scanned. In an optical scanning device including a second optical system that condenses light as a spot, a light detection unit that generates a synchronization signal for determining a writing start position, and a third optical system that guides a scanned light beam to the light detection unit A light, characterized in that a plurality of holding mechanisms for at least one optical element constituting the first, second and third optical systems are arranged in accordance with the mounting position of the optical element. Scanning device. 2. The holding mechanism according to claim 1, wherein the plurality of holding mechanisms are all formed of the same holding mechanism.
The optical scanning device according to claim 1. 3. The optical scanning device according to claim 1, wherein at least one of the plurality of holding mechanisms comprises a holding mechanism having a different configuration. 4. The optical scanning device according to claim 2, wherein the plurality of holding mechanisms are arranged in parallel in the optical axis direction of each optical system. 5. The optical scanning device according to claim 4, wherein the plurality of holding mechanisms are holding mechanisms for optical elements constituting the first optical system. 6. The optical scanning device according to claim 5, wherein the first optical system has an aperture function, and the aperture diameter is determined according to a mounting position of the optical element. 7. A plurality of holding mechanisms for restricting a light beam coupled from a light source unit by an opening function,
7. The optical scanning device according to claim 5, wherein the optical scanning device is a holding mechanism for holding a cylindrical lens of the first optical system for forming an elongated line image near a deflection reflecting surface of the optical deflector. 8. The optical scanning device according to claim 6, wherein the aperture diameter is determined so as to change the light amount while keeping the light spot diameter on the surface to be scanned constant. 9. The optical scanning device according to claim 6, wherein the aperture diameter is determined so as to change the light spot diameter while keeping the light amount on the surface to be scanned constant. 10. The optical scanning device according to claim 6, wherein the aperture diameter is determined so as to change the light amount and the light spot diameter on the surface to be scanned. 11. A structure in which a plurality of holding mechanisms are provided, wherein the first holding mechanism is different in order from the light source side, and the second holding mechanism and the third holding mechanism are equal. The optical scanning device according to claim 7. 12. A holding mechanism comprising a plurality of holding mechanisms, wherein the first holding mechanism and the second holding mechanism are equal in order from the light source side, and the third holding mechanism is different. The optical scanning device according to claim 7.