JP4788286B2 - Optical scanning device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to an optical scanning device used in an image forming apparatus such as a copying machine or a printer, and in particular, deflects and scans a light beam emitted from a light source as an exposure light source for forming a latent image by an electrophotographic method. The present invention relates to an optical scanning device and an image forming apparatus using the same.

In general, in an electrophotographic image forming apparatus, a method of forming a desired electrostatic latent image by deflecting and scanning a light beam from a light source using a semiconductor laser onto a charged photoreceptor is known. In such a system, since the beam diameter of the light beam directly greatly influences the image quality of the latent image, it has been practiced to reduce the beam diameter with the recent demand for higher image quality.
On the other hand, when the beam diameter of the light beam is reduced, the depth of focus (DOF) tends to become shallower. Since the beam diameter and the DOF are in a contradictory characteristic, the beam diameter is reduced. It is important to simultaneously secure the necessary depth of the DOF for obtaining good image quality over the entire image forming area.

  For such a problem, an optical scanning device using a very deep Bessel beam whose DOF is equal to or longer than the optical path length is known (see, for example, Patent Document 1). Here, it is assumed that by using a Bessel beam, an optical system that does not require the limitation of aberration by the polygon mirror can be realized. In addition, the size of the aperture in the sub-scanning direction is set to be different in the main scanning direction, and the periphery is wider than the center, so that the amount of light reflected by the polygon mirror is uniform in the overfield scanning optical system (OFS). A proposal has been made to make the beam uniform on the imaging plane (see, for example, Patent Document 2).

JP-A-8-179231 (Example, FIG. 1) JP 2001-125033 (first embodiment, FIG. 1)

However, since a device that emits a light beam having a Bessel distribution as in Patent Document 1 requires a complicated configuration, there is a drawback that it tends to be expensive. Further, in the method of Patent Document 2, it is difficult to accurately produce a diaphragm having an accurate aperture shape with different dimensions in the center and the periphery in the main scanning direction, which tends to be expensive.
The present invention has been made to solve the above technical problem, and an optical scanning device capable of realizing a light beam having a small beam diameter and a DOF having a required depth with a simple configuration, and An image forming apparatus using the same is provided.

In order to solve the above-mentioned problem, the inventors previously changed the transmittance of the aperture in the main scanning direction in Japanese Patent Application No. 2005-087207 to lower the transmittance at the center of the aperture from the periphery. In addition, an optical scanning device capable of reducing the beam diameter while maintaining the DOF of the light beam applied to the imaging surface has been proposed.
However, even in this method, there is a concern that the configuration of the diaphragm becomes complicated in order to have a transmittance variation at the aperture. Therefore, the inventors of the present invention have further studied the simplification of the configuration and have come up with the present invention.

That is, the first aspect of the present invention, as shown in FIG. 1, a light source 1 for emitting a light beam, a focusing means 2 to the light flux converging the light beam emitted from the light source 1 , a light beam deflecting means (3) for deflecting and scanning a focused light beam, focused to image the and light beam scanningly deflected by the beam deflecting means 3 has at least one or more concave mirror 4a on the image plane 5 optical and it means 4, the condensing means 2 is restricted shape of a light beam that passes through is and comprises a beam restricting member 2a having a flat opening 2b in the sub-scanning direction, the light beam restriction member 2a, the formation The center of the opening 2b is arranged so as to be displaced from the center of the optical axis in a direction in which the influence of the coma aberration of the concave mirror 4a of the image optical means 4 is reduced.

In such technical means, the light source 1 may be any light source capable of emitting a light beam, and a typical embodiment includes a semiconductor laser. The semiconductor laser may be an edge emitting type or a surface emitting type. Further, the condensing means 2 may be anything that condenses the light beam emitted from the light source 1, and a typical mode includes a collimator lens that collimates the light beam from the light source 1. Further, the light beam deflecting unit 3 may be any mode that can deflect and scan an incident light beam, and typically includes a rotating polygon mirror.
The imaging optical means 4 in the present invention is only required to image the light beam deflected and scanned by the light beam deflecting means 3 on the imaging surface 5, and includes at least one concave mirror 4a and a toric lens. And so on. As described above, in the present invention, the concave mirror 4a is used as a part of the imaging optical means 4, so that both the beam diameter of the light beam on the imaging surface 5 and the DOF are kept good, and the size and the size are reduced. It becomes possible to realize an optical scanning device capable of reducing the cost.

  Normally, in a mode in which the parallel light from the light source 1 is regulated by the light flux regulating member 2a, and the light flux that has passed through the light flux regulating member 2a is deflected by the light flux deflecting means 3 and imaged on the image plane 5, The regulating member 2a is regulated so as to obtain a predetermined beam diameter. On the other hand, the DOF is determined by the narrowing angle of the light beam entering the imaging plane 5, and the smaller the angle, the deeper the DOF. This angle is determined by the outermost part of the opening 2b of the light flux regulating member 2a, and the DOF can be deepened as the opening 2b is made smaller. On the other hand, as a first approximation determined by the diffraction limit, the beam diameter shows a characteristic opposite to that of DOF, and the beam diameter can be reduced as the narrowing angle of the light beam is increased.

However, in such an optical scanning device, the beam diameter is further affected by aberrations and assembly errors in the imaging optical means 4. In particular, when the concave mirror 4a such as a cylindrical mirror is used, in order to irradiate the image plane 5 with the light beam, the light beam is inclined with respect to the normal direction (optical axis) of the concave mirror 4a. The influence of coma appears strongly, and field curvature (image forming position varies depending on the deflection direction) also appears.
In the present invention, the coma aberration can be reduced by reducing the light flux on the side of the concave mirror 4a where the coma aberration is large, that is, the side away from the optical axis of the concave mirror 4a.

FIG. 2 shows such a state, and when the opening 2b of the light flux regulating member 2a is a solid line, among the light rays that have passed through the opening 2b (light rays indicated by a, b, and c in the figure) In particular, the light beam a is reflected by the concave mirror 4a and becomes a light beam having a large coma aberration. Therefore, for example, assuming that the light flux regulating member 2a is moved upward (one side in the sub-scanning direction) in the figure and the opening 2b is as shown by a two-dot chain line in the figure, a of the initial rays is blocked. The light beam d is newly transmitted through the opening 2b of the light flux regulating member 2a. Since the light ray d becomes a light ray close to the center of the concave mirror 4a (close to the optical axis), the light ray d reflected by the concave mirror 4a becomes a light ray with small coma aberration. Therefore, by moving the light beam restricting member 2a in the sub-scanning direction, a light beam having a large coma aberration (shown by a in the figure) is shielded, and a light beam having a low coma aberration (shown by a two-dot chain line in the figure) is substituted. It becomes transparent. Therefore, the coma aberration of the light beam reflected by the concave mirror 4a can be reduced by moving the light beam restricting member 2a, and a preferable beam diameter and DOF for the light beam irradiated on the imaging surface 5 are realized. Will be able to.
In the drawing, the concave mirror 4a is shown as one example. However, when a plurality of concave mirrors 4a are provided, the light flux regulating member 2a may be moved in a direction to reduce the coma due to the mutual influence.

  As described above, the light flux regulating member 2a in the present invention only needs to have only the opening 2b, and the shape of the opening 2b can be easily realized, so that the cost can be reduced. The shape of the opening 2b is not particularly limited, such as a rectangle or an ellipse, but is flat in the sub-scanning direction from the viewpoint of reducing the beam diameter of the light beam applied to the imaging surface 5 and deepening the DOF. A rectangular shape (extending in the scanning direction) is preferable.

Further, as the second aspect of the present invention, as shown in FIG. 1, a light source 1 for emitting a light beam, a focusing means 2 to the light flux converging the light beam emitted from the light source 1 , a light beam deflecting means (3) for deflecting and scanning a focused light beam, focused to image the and light beam scanningly deflected by the beam deflecting means 3 has at least one or more concave mirror 4a on the image plane 5 optical and means 4, the condensing means 2, a beam restricting member 2a the shape of the light flux having a flat opening 2b to be regulated and the sub-scanning direction, which is transmitted, the frame of the concave mirror 4a of the imaging optical means 4 influence of aberration, characterized in that the center of the opening 2b of the light flux regulating member 2a so as to be reduced; and a moving adjustment unit 6 to be displaced from the center of the optical axis of the light source 1. That is, it is assumed that the light beam restriction member 2a in the first embodiment is provided with the moving adjusting means 6 can be displaced in the sub-scanning direction.

  Thus, by providing the movement adjusting means 6, it becomes easier to adjust the coma aberration in the actual machine against the assembly error of the optical scanning device, and the beam diameter of the light beam irradiated onto the imaging plane 5 is set to a desired size. It becomes possible to be.

In the present invention, in any embodiment, the light beam restriction member 2a sub-scanning direction more than 30% of center light source 1 of the optical axis center from the sub-scanning direction opening length of the opening 2b In this case, it is preferable that the effect of clearly reducing the influence of coma aberration on the imaging optical means 4 is confirmed. Although so reduce the coma aberration is made also in principle is less than 30%, specific effects considering the on the image if more than 30% displacement at the image plane 5 is preferred.

Then, the condensing unit 2 in the present invention includes a collimator lens for collimating light beams a light beam emitted from the light source 1, and a cylindrical lens for converging the collimated light beam in the sub-scanning direction, the light beam restriction member it is preferred that the one provided between the 2a and the collimator lens and the cylindrical lens, according to this, the light beam emitted from the light source 1 becomes a parallel light flux by the collimator lens, the light beam restriction member by light flux restricted by 2a is condensed by the cylindrical lens, after passing through the beam deflecting means 3 and the image-forming optical means 4, reducing the beam diameter of the light beam irradiated to the image plane 5 Will be able to.

  Furthermore, the present invention is not limited to an optical scanning device, and is also intended for an image forming apparatus. In this case, an image carrier on which an electrostatic latent image is carried and an image can be formed on the image carrier. What is necessary is just to make it provide the above-mentioned optical scanning device as an optical scanning device.

According to the present invention, the light source includes a light source, a condensing unit, a light beam deflecting unit, and an imaging optical unit, and the condensing unit regulates the shape of the transmitted light beam and has a flat opening in the sub-scanning direction. And the light beam restricting member is disposed so that the center of the opening is displaced from the center of the optical axis in a direction in which the influence of the coma aberration of the concave mirror of the imaging optical means is reduced. An optical scanning device that can reduce the influence of coma aberration by the light beam applied to the lens and has both a reduced beam diameter and a required DOF depth can be easily realized with a simple configuration. Also, good image quality can be maintained over the entire image area.
Furthermore, by using such an optical scanning device, it is possible to realize an image forming apparatus that has a simple configuration and ensures good image quality over the entire image area.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 3 shows an embodiment of an image forming apparatus to which the present invention is applied.
In the figure, the image forming apparatus according to the present embodiment includes a photoconductor drum 20 and an intermediate transfer disposed opposite to the photoconductor drum 20 in order to transfer a toner image from the photoconductor drum 20 in the apparatus main body 50. This is a so-called four-cycle type intermediate transfer type color image forming apparatus that includes a belt 30 and performs four times of multiple transfers on the intermediate transfer belt 30 to obtain four color images.
In the present embodiment, the photosensitive drum 20 includes a photosensitive layer whose resistance value is reduced by light irradiation. Around the photosensitive drum 20, a charging device 21 for charging the photosensitive drum 20 and a charging device 21 are provided. An optical scanning device (exposure device) for writing an electrostatic latent image of each color component (in this example, black (K), yellow (Y), magenta (M), cyan (C)) on the charged photosensitive drum 20. ) 60, a rotary developing device 23 that visualizes each color component latent image formed on the photosensitive drum 20 with each color component toner, an intermediate transfer belt 30, and residual toner on the photosensitive drum 20. A cleaning device 27 for cleaning is disposed.

  Here, as the charging device 21, for example, a charging roll is used, but a charging device such as a corotron may be used. Further, the rotary developing device 23 is rotatably mounted with developing units 23a to 23d containing respective color component toners. For example, the respective color component toners are attached to a portion of the photosensitive drum 20 where the potential is lowered by exposure. The toner to be used is not particularly limited in shape and particle size, and any toner may be used as long as it is accurately placed on the electrostatic latent image on the photosensitive drum 20. In this example, the rotary developing device 23 is used, but four developing devices may be used. Furthermore, as long as the cleaning device 27 cleans the residual toner on the photosensitive drum 20, a cleaning device employing a blade cleaning method may be appropriately selected. However, there may be a mode in which the cleaning device 27 is not used when toner having a high transfer rate is used.

Further, the intermediate transfer belt 30 is stretched around three stretching rolls 31 to 33, and circulates and moves, for example, using the stretching roll 31 as a driving roll.
Here, the intermediate transfer belt 30 may be appropriately selected from a resin material such as polyimide resin. However, in order to effectively suppress image quality defects such as a holocharacter, the contact surface pressure with the photosensitive drum 20 may be lowered. In consideration of the viewpoint of walkless and tensionerless, it is preferable to use a rubber belt material such as urethane rubber having an elastic rubber as a base (elastic layer).

Further, in the present embodiment, a primary transfer roll 25 as a primary transfer member is disposed in contact with the back side of the intermediate transfer belt 30 at a portion of the intermediate transfer belt 30 facing the photosensitive drum 20, and a predetermined primary A transfer bias is applied.
Furthermore, a secondary transfer roll 35 as a secondary transfer member is disposed opposite to the tension roll 32 of the intermediate transfer belt 30 with the tension roll 32 as a backup roll. For example, the secondary transfer roll A predetermined secondary transfer bias is applied to 35, and a stretching roll 32 that also serves as a backup roll is grounded.
Note that a belt cleaning device 36 is disposed at a portion of the intermediate transfer belt 30 facing the stretching roll 31 so as to clean the residual toner on the intermediate transfer belt 30.
Further, the recording material 40 such as paper is accommodated in a supply tray (not shown), and is supplied by a feed roll 41 and then guided to a secondary transfer portion through a resist roll 42 and a secondary transfer roll 35. As a result, the toner images that have been multiple-transferred onto the intermediate transfer belt 30 are collectively transferred onto the recording material. The recording material on which the toner images are collectively transferred is conveyed to the fixing device 45 via the conveyance belt 43, and then accommodated in the discharge tray 48 formed on the upper portion of the apparatus main body 50 via the conveyance roll 46 and the discharge roll 47. It has become so.

  In particular, as shown in FIG. 4, the optical scanning device 60 in the present embodiment includes a semiconductor laser 61 that emits a light beam, a condensing device 70 that condenses the light beam emitted from the semiconductor laser 61, and a condensing device. A polygon mirror 80 that deflects and scans the light beam collected by 70, and an imaging optical device 90 that forms an image on the photosensitive drum 20 of the light beam deflected and scanned by the polygon mirror 80.

  The condensing device 70 collimates the light beam emitted from the semiconductor laser 61 to make a parallel light beam, and a diaphragm 72 as a light beam regulating member that shapes the cross-sectional shape of the parallel light beam by the collimator lens 71. The cylindrical lens 73 collects the shaped light beam along the sub-scanning direction.

  The polygon mirror 80 has a regular polygonal shape (for example, regular hexagonal shape) provided with a plurality of reflecting surfaces on its side surface, and is pivotally attached to a polygon motor (not shown). It rotates at a predetermined rotational speed in the direction of arrow R. Therefore, the light beam incident on the reflecting surface is deflected and scanned in the main scanning direction, that is, the axial direction of the photosensitive drum 20 in the imaging optical device 90 as the polygon mirror 80 rotates.

The imaging optical device 90 is, for example, a cylindrical lens 91, a toric lens 92, and an imaging lens as an imaging lens system for keeping the scanning speed of the light beam deflected and scanned by the polygon mirror 80 on the surface of the photosensitive drum 20 constant. 93. In the present embodiment, such a configuration is shown as the imaging lens system. However, the present invention is not limited to this, and any other imaging lens system may be used as long as the scanning speed on the surface of the photosensitive drum 20 is constant. There is no problem depending on the configuration.
In the imaging optical device 90 according to the present embodiment, the light beam transmitted through the imaging lens system is condensed and reflected by a cylindrical mirror 94 as a concave mirror, and then reflected on the surface of the photosensitive drum 20 via the reflection mirror 95. Irradiated.
Further, the imaging optical device 90 includes a mirror 96 that reflects a part of the light beam transmitted through the imaging lens system (light beam corresponding to the scanning start position by each reflection surface of the polygon mirror 80), and a mirror 96 An SOS (Start of Scan) light receiving unit 97 including a photo detector for detecting reflected light is provided. For this reason, the SOS light receiving unit 97 detects the scanning start timing for each line (main scanning direction) to the photosensitive drum 20. Needless to say, the SOS light receiving unit 97 is provided outside the region of the light beam deflected and scanned by the polygon mirror 80.

  Further, as shown in FIG. 5A, the diaphragm 72 installed in the light condensing device 70 in the present embodiment has a rectangular aperture 72a that is flat in the sub-scanning direction (for example, the side dimension in the main scanning direction is 4 mm). , A rectangular shape having a side dimension in the sub-scanning direction of 0.5 mm) at the substantially central portion. Then, as shown in (b), the diaphragm 72 is arranged such that the central axis in the sub-scanning direction of the aperture 72a is displaced by D from the optical axis. Further, the dimension D is 30% or more of the side dimension L in the sub-scanning direction of the aperture 72a.

  Next, the operation of the image forming apparatus according to the present embodiment will be described focusing on the optical scanning device 60. In FIG. 4, the light beam emitted from the semiconductor laser 61 becomes a collimated light beam by the collimator lens 71, a part of the parallel beam is shielded by the aperture 72 a of the stop 72, and only the shaped light beam is transmitted. The light beam transmitted through the stop 72 is imaged by the cylindrical lens 73 on the reflection surface of the polygon mirror 80 in the sub-scanning direction of the light beam. Therefore, the light flux on the reflecting surface of the polygon mirror 80 is imaged in the sub-scanning direction, and the main scanning direction has a width similar to the width of the aperture 72a (see FIG. 4) (side dimension in the main scanning direction). Imaged. The light beam reflected by the polygon mirror 80 is imaged on the photosensitive drum 20 so as to have a desired beam diameter via the imaging optical device 90.

Here, coma aberration in the present embodiment will be described with reference to FIG. When the light beam A away from the optical axis and the light beam B close to the optical axis O are irradiated to the optical axis O of the cylindrical mirror 94, the light beam reflected by the boundary surface (reflection surface) of the cylindrical mirror 94 is ideal. Specifically, it becomes a dotted line passing through the focal point F, but as shown by a solid line, it becomes a light beam A ′ and a light beam B ′ that are deviated from the focal point. When the cylindrical mirror 94 is used, a coma aberration occurs because the light beam from the normal direction cannot be applied to the reflecting surface of the cylindrical mirror 94. At this time, since the light beam A is in a direction shifted from the optical axis O of the cylindrical mirror 94, the coma aberration of the light beam A ′ is larger than that of the light beam B ′. Therefore, it is necessary to adjust the position of the diaphragm 72 in consideration of such coma aberration.
When two cylindrical mirrors are provided, the light beam reflected by the above-described cylindrical mirror 94 is reflected by another cylindrical mirror, so that the coma aberration increases. Therefore, in such a case, the optimum position is obtained by comprehensively determining the mutual positional relationship between the cylindrical mirrors and the coma aberration of both.

Next, the position adjustment of the diaphragm 72 will be described with reference to FIGS.
As a first approximation, the DOF is determined by the narrowing angle of the light beam incident on the surface of the photosensitive drum 20, so that the deeper DOF is obtained as the angle is reduced. This angle is determined by the aperture 72a, and the smaller the shape of the aperture 72a, the deeper the DOF. On the other hand, the beam diameter has an inverse relationship with DOF, and the smaller the beam narrowing angle, the smaller the beam diameter can be realized.
However, in the imaging optical device 90, there are assembly errors and various aberrations, and the DOF and beam diameter obtained by the first approximation described above do not coincide with the light flux actually irradiated on the surface of the photosensitive drum 20. In particular, in the present embodiment, a cylindrical mirror 94 is used in the imaging optical device 90, and the light flux is incident on the reflecting surface from a direction oblique to the normal direction of the reflecting surface. Will appear greatly.

Therefore, a measurement surface is prepared at a position conjugated with the surface of the photosensitive drum 20, the beam diameter is measured there, and the beam diameter is measured by moving the measurement surface back and forth from the conjugate position. The degree of DOF of the beam can be determined by moving the measurement surface back and forth in this way. Then, such a measurement is repeated by changing the deflection direction of the polygon mirror 80. Further, the position of the stop 72 is displaced in the sub-scanning direction and the measurement of the beam diameter is repeated in the same manner.
In this way, the diaphragm 72 is fixed at a position where the beam diameter is small and a light beam having a deep DOF can be secured. In the present embodiment, the center of the aperture 72a of the stop 72 in the sub-scanning direction is displaced from the optical axis by 30% or more of the side dimension in the sub-scanning direction, so that the influence of the coma aberration due to the cylindrical mirror 94 can be removed. In addition, a desired beam diameter and DOF can be realized with respect to the light beam irradiated on the surface of the photosensitive drum 20.
As described above, in the optical scanning device 60 according to the present embodiment, the position of the stop 72 in the sub-scanning direction is shifted from the optical axis, and the influence of aberration generated in the imaging optical device 90 including the cylindrical mirror 94 is minimized. Thus, since the position of the diaphragm 72 is fixed, the optical scanning device 60 in which the beam diameter of the light beam applied to the photosensitive drum 20 is reduced and the required depth of DOF can be realized with a simple configuration. In addition, it is possible to obtain good image quality over the entire surface of the image on the photosensitive drum 20.
Furthermore, since the aperture 72a has a simple rectangular shape, the diaphragm 72 can be easily manufactured, and the low-cost optical scanning device 60 can be realized. In the present embodiment, a rectangular shape is shown as the shape of the aperture 72a, but it is not particularly limited. For example, an elliptical shape having the major axis in the main scanning direction and the minor axis in the sub scanning direction may be used. Further, for example, an oval shape may be used.

  In the present embodiment, the semiconductor laser 61 is used as the light source. However, the semiconductor laser 61 is not limited to a semiconductor. Further, in the case of the semiconductor laser 61, an edge emission type or a surface emission type may be used.

FIG. 7 shows a modification of the present embodiment. A movement adjustment mechanism 100 that can displace the diaphragm 72 in the sub-scanning direction is provided below the diaphragm 72.
In the figure, the movement adjusting mechanism 100 in this example is provided with a table 102 that is movable in the vertical direction (sub-scanning direction) above the pedestal 101 fixed in the optical scanning device 60. Between 102, the support shaft 103 fixed to the table 102 can slide in the sub-scanning direction with respect to the pedestal 101. Further, a fixed base 104 for fixing the diaphragm 72 is integrally mounted on the table 102 so that the diaphragm 72 can move as the table 102 moves.

By providing such a movement adjusting mechanism 100, the position of the diaphragm 72 is set so that the influence of the aberration generated in the imaging optical device 90 including the cylindrical mirror 94 is minimized as in the above-described embodiment. Can be adjusted within.
The movement adjusting mechanism 100 is not limited to such a configuration, and the diaphragm 72 may be moved up and down using members such as screws and springs, for example. In this case, the spring may be biased in one direction and moved from the opposite direction with a screw.

It is explanatory drawing which shows the outline | summary of the optical scanning device based on this invention. It is explanatory drawing which shows the effect | action of this invention. 1 is an explanatory diagram illustrating an image forming apparatus according to an embodiment to which the present invention is applied. It is explanatory drawing which shows the outline | summary of the optical scanning device of embodiment. (A) shows the outline | summary of the aperture_diaphragm | restriction used by embodiment, (b) is explanatory drawing which shows the layout of an aperture_diaphragm | restriction. It is explanatory drawing which shows the coma aberration in a cylindrical mirror. It is explanatory drawing which shows the movement adjustment mechanism of a diaphragm as a modification of embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... Condensing means, 2a ... Light beam control member, 2b ... Opening part, 3 ... Light beam deflection means, 4 ... Imaging optical means, 4a ... Concave mirror, 5 ... Imaging surface, 6 ... Movement adjustment means

Claims (5)

A light source that emits a light beam;
And focusing means for the light beam converging the light beam emitted from said light source,
Luminous flux deflecting means for deflecting and scanning the condensed luminous flux;
And an imaging optical means for focusing onto the image plane at least 1 or more has a concave mirror and the light beam deflected and scanned by the light beam deflecting means,
The condensing means includes a light flux regulating member in which the shape of the transmitted light flux is regulated and has a flat opening in the sub-scanning direction,
The light beam regulating member is disposed so that the center of the opening is displaced from the center of the optical axis in a direction in which the influence of coma aberration of the concave mirror of the imaging optical means is reduced. apparatus. A light source that emits a light beam;
And focusing means for the light beam converging the light beam emitted from said light source,
Luminous flux deflecting means for deflecting and scanning the condensed luminous flux;
And an imaging optical means for focusing onto the image plane at least 1 or more has a concave mirror and the light beam deflected and scanned by the light beam deflecting means,
The condensing means includes a light flux regulating member in which the shape of the transmitted light flux is regulated and has an opening that is flat in the sub-scanning direction;
; And a movement adjustment means for the center of the opening of the light beam restriction member such that the effect of the coma aberration of the concave mirror of the imaging optical means is reduced to be displaced from the center of the optical axis of the light source An optical scanning device. The optical scanning device according to claim 1 or 2,
The light beam restriction member includes an optical scanning, wherein a center of the opening is arranged to be displaced in the sub-scanning direction of 30% or more sub-scanning direction of the opening length from the center of the optical axis of the light source apparatus. The optical scanning device according to claim 1 or 2,
Said condensing means, said collimator lens for collimating light beams a light beam emitted from said light source, a cylindrical lens for converging the collimated light beam in the sub-scanning direction, the light flux regulating member and the collimator lens cylindrical An optical scanning device provided between a lens and a lens. An image carrier on which an electrostatic latent image is carried;
An image forming apparatus comprising: the optical scanning device according to claim 1, which is capable of forming an image on the image carrier.

Images