JP2003207734A - Scanning optical device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning optical device and an image forming apparatus which improves the accuracy of scanning exposure by improving the positioning accuracy of lenses. <P>SOLUTION: Projecting parts 4c and 4d individually functioning as positioning parts to an optical box 10 are provided at the center parts of a first lens 4a and a second lens 4b constituting an fθ lens 4 in a scanning direction so that the projecting parts face each other. On the other hand, the optical box 10 is provided with a pair of positioning ribs 10a and 10b so as to hold both projected parts 4c and 4d in-between. The inside surface of the positioning rib 10a is made a reference surface to position the first lens 4a and second lens 4b. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device that performs exposure scanning and an image forming apparatus including the same.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus such as a laser beam printer is provided with a scanning optical device for performing exposure scanning for forming an electrostatic latent image on an image bearing member such as a photosensitive drum.

An exposure scanning apparatus according to the prior art will be described with reference to FIG. FIG. 13 is a sample configuration of an optical system of a typical scanning optical device.

In FIG. 13, description will be given along the traveling direction of light. Reference numeral 101 is a semiconductor laser as a light source. The laser light is emitted from a single point light source while diverging, but the divergent light flux is converted into a parallel state by passing through the collimator lens 102a. By passing through the cylindrical lens 102c, this light beam is converged linearly on the polygon mirror 103 by being converged in only one direction.

An aperture stop 102b is arranged between the collimator lens 102a and the polygon mirror 103, and the beam shape is determined according to the stop shape. The polygon mirror 103 is fixed to the scanner motor 103a and rotates at high speed in the arrow direction. The light beam reflected by the mirror surface of the polygon mirror 103 is deflected and scanned at high speed as the scanner motor 103a rotates.

Further, the light beam is a spherical lens 104a.
By passing through the fθ lens 104 composed of the toric lens 104b and the toric lens 104b, an image is formed in a minute spot on the photosensitive drum 105.

After passing through the fθ lens 104, the light beam deflected and scanned by the polygon mirror 103 at a constant angular velocity is converted so that a light spot is scanned on the photosensitive drum 105 at a constant velocity.

The light spot is repeatedly scanned on the photosensitive drum 105. However, if there is a division error in the reflecting surface of the polygon mirror 103, the timing for writing the scanning information is repeatedly shifted, so that the light spot is deflected. The light beam at the scanned top is detected. The light beam of the image non-effective portion is reflected by the fixed mirror 106, and the condenser lens 10
It is guided to the timing detection sensor 107 via 6a.

In such a scanning optical device, the two lenses (the spherical lens 104) that compose the fθ lens 104 are used.
The a and the toric lens 104b) are positioned and fixed by a positioning rib provided in an optical box that houses each optical member.

Here, two lenses (spherical lens 104
If the positioning portions for positioning in the deflection scanning direction of a and the toric lens 104b) are set at separate positions, it is difficult to accurately provide positioning ribs for positioning both lenses when molding the optical box. There is a drawback that.

Further, when the optical box thermally expands due to the temperature change caused by the heat generated by the scanner motor, the displacement amounts of the members (ribs and the like) constituting the positioning portions of both lenses are different from each other. There is a defect that the axis is displaced and the optical performance is deteriorated. In particular, a “one-sided magnification difference” occurs in which the magnifications of the left and right images differ from the center of the image.

[0012]

As described above, in the case of the prior art, there is a problem that the positioning accuracy of the lens for performing exposure scanning is low.

It is an object of the present invention to provide a scanning optical device and an image forming apparatus which improve the positioning accuracy of a lens and the scanning exposure accuracy.

[0014]

To achieve the above object, in the present invention, the optical box is provided with a positioning rib for positioning both the first lens and the second lens.
In this case, by arranging the positioning parts with respect to the optical box provided in each lens so as to face each other, it is possible to position the pair of lenses by the same positioning rib provided in the optical box. did. The positioning portion of each lens can be formed in, for example, a convex shape or a concave shape.

According to the configuration of the present invention, since the first lens and the second lens are positioned by the same positioning rib, deformation of the optical box (deformation such as mechanical warp, warpage or contraction during molding) is caused. The effect of deformation, deformation due to heat shrinkage, etc.) is reduced.

The positioning rib provided on the optical box is provided with a reference surface with which any of the contacting surfaces for positioning provided on each lens comes into contact, and the reference surface allows the first lens and the first lens to come into contact. By positioning both of the two lenses, positioning can be performed with a simple configuration.

The contacting surface provided on each lens for positioning has, for example, a convex portion provided on each lens,
The side surface can be a contact surface for contacting the reference surface of the positioning rib.

Here, a pair of the above-mentioned positioning ribs are provided so as to face each other, and on the other hand, a positioning convex portion is provided on each of the first lens and the second lens, and this convex portion is provided between the pair of positioning ribs. The first lens and the second lens can be easily positioned by sandwiching the first lens and the second lens.
In this case, by making at least one of the positioning ribs elastically deformable, if the convex portions are elastically sandwiched, the positioning can be performed without causing any looseness.

Further, if a pressing means for pressing the abutting surfaces for positioning provided on each of the first lens and the second lens against the reference surface of the positioning rib is provided, rattling will occur. It can be prevented.

Here, as the pressing means, a spring or a rib which exerts a pressing action by its own elastic restoring force can be used. When the ribs are used, if the ribs are provided independently corresponding to each lens, the pressing operation is independently performed without being affected by the error generated for each lens.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions of the components described in this embodiment,
Unless otherwise specified, the material, the shape, the relative arrangement, and the like are not intended to limit the scope of the present invention thereto.

(First Embodiment) A scanning optical device according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a plan view for explaining the structure of a scanning optical device according to the first embodiment of the present invention, which is used in a laser beam printer and scans a photosensitive member with a light beam. It is a figure for demonstrating the function of each structural member contained in an apparatus. FIG. 2 shows a plan view with the lid removed.

The scanning optical device is generally an optical box 10 containing various optical members, and a semiconductor laser device 1 as a light source.
And a collimator lens 1a for collimating the collimated light beam generated from the semiconductor laser device 1 and a cylindrical lens 2 for linearly condensing the collimated light beam from the collimator lens 1a.
And a rotary polygon mirror 3 having a deflecting / reflecting surface in the vicinity of a line image of a light beam formed by the cylindrical lens 2.
And a scanner motor 3b which is means for rotating the same.
And the fθ lens 4 and the like.

The light beam deflected and reflected by the rotary polygon mirror 3 enters the folding mirror 5 through the fθ lens 4,
The light is reflected by the folding mirror 5 and illuminates a photoconductor (not shown) as an image carrier.

The fθ lens 4 is designed so that the light beam reflected by the rotary polygon mirror 3 is condensed so as to form a spot on the photosensitive member, and the scanning speed of the spot is kept constant. There is.

The rotation of the rotary polygon mirror 3 causes main scanning by the light beam on the photosensitive member, and sub-scanning by rotationally driving the photosensitive member around the axis of the cylinder. In this way, an electrostatic latent image is formed on the surface of the photoconductor.

An image forming technique using a photoconductor is well known as an electrophotographic recording technique, and therefore a detailed description thereof will be omitted and simply described.

Around the photoconductor, a corona discharger for uniformly charging the surface of the photoconductor, and a visualizing device for visualizing an electrostatic latent image formed on the surface of the photoconductor into a toner image. (Developing device), a transfer corona discharger (not shown) as a transfer means for transferring the toner image to the recording paper, and the like are arranged, and these functions correspond to the luminous flux generated by the semiconductor laser device 1. The record information is printed on the recording paper.

In the portion surrounded by a circle in FIG. 1, details around the positioning portion of the fθ lens 4 in the present embodiment are shown.

The fθ lens 4 is composed of two lenses, a first lens 4a and a second lens 4b. First lens 4
A convex portion 4c, 4d that functions as a positioning portion for the optical box 10 is provided in the central portion (the central portion of the scanning region) of the a and the second lens 4b in the scanning direction (longitudinal direction).

These convex shapes 4c and 4d are provided at positions facing each other. On the other hand, the optical box 10 is provided with a pair of positioning ribs 10a and 10b so as to sandwich both the convex shapes 4c and 4d.

The positioning rib 10a has an inner surface (center side in the longitudinal direction of the lens) whose surface is the first lens 4a and the second lens 4a.
It serves as a reference surface for positioning the lens 4b.
That is, when the side surface (contact surface) of the convex shape 4c provided on the first lens 4a contacts the reference surface,
The first lens 4a is positioned. Then, the side surface (contact surface) of the convex shape 4d provided on the second lens 4b also contacts the reference surface, whereby the second lens 4b is positioned.

As described above, the positioning rib 10a has the first rib.
The function of positioning both the lens 4a and the second lens 4b is exhibited.

In the present embodiment, the positioning rib 10b provided so as to face the positioning rib 10a.
Also has the same function as the positioning rib 10a. That is, the inner surface of the positioning rib 10b is the first lens 4a.
And a reference surface for positioning the second lens 4b.

The convex shape 4c provided on the first lens 4a and the convex shape 4d provided on the second lens 4b are provided between the pair of positioning ribs 10a and 10b.
The first lens 4a and the second lens 4a
This is a configuration for positioning the lens 4b.

With the above structure, one positioning rib includes the positioning portions (reference surfaces) for the two lenses (the first lens 4a and the second lens 4b). The positional accuracy of the lens is less affected by the warp and contraction of the optical box. Therefore, the optical box 1
When producing a mold for molding 0, the rib position can be accurately molded.

Further, when the scanner motor 3b rotates at a high speed, the optical box is thermally expanded and deformed due to heat generation, but as described above, one positioning rib includes the positioning portions of two lenses. If so, the thermal deformations of the positioning portions of the two lenses become almost equal, so
It is possible to make the relative positional deviations of the lenses in the scanning direction substantially equal.

In this way, it was possible to improve the positioning accuracy of the lens. Further, since the positioning accuracy of the lens is improved, the scanning exposure accuracy can be improved.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention. In the first embodiment, two positioning ribs are provided and two lenses are positioned by both positioning ribs. However, in the present embodiment, only one positioning rib is provided and two positioning ribs are provided. By pressing the abutting surfaces for positioning provided on the two lenses against the reference surface of the single positioning rib, 2
The structure which positions two lenses is shown.

Since other configurations and operations are the same as those of the first embodiment, the same reference numerals are given to the same components and the description thereof will be omitted.

FIG. 3 is an enlarged view of the vicinity of the lens positioning portion in the scanning optical device according to the second embodiment of the present invention.

In the first embodiment, the convex shape 4c of the first lens 4a constituting the fθ lens 4 and the second
The convex shape 4d of the lens 4b has two positioning ribs 10
It was arranged to be positioned by each of a and 10b. However, each convex shape is replaced by two positioning ribs 10.
It is difficult to surely position with respect to both the reference surfaces a and 10b.

Actually, the convex shape 4c and the convex shape 4d are
Since it is fitted between the pair of positioning ribs 10a and 10b, there is a fitting play (a play corresponding to the clearance provided for fitting).

Therefore, the positional deviation will occur by the amount of the fitting backlash.

Therefore, in this embodiment, only one positioning rib 10a for positioning the two lenses (the first lens 4a and the second lens 4b) is provided.

A spring 11 as a pressing means is provided at a position facing the positioning rib 10a, and the spring 1
By urging the convex shape 4c and the convex shape 4d toward the positioning rib 10a by 1, the side surfaces (contact surfaces for positioning) of the convex shape 4c and the convex shape 4d become the reference surface of the positioning rib 10a. It was pressed against.

With the above structure, the side surfaces (contact surfaces) of the convex shapes 4c and 4d are surely brought into contact with a single reference surface for positioning, so that the first lens 4a and the second lens 4a are positioned. 4b is positioned more accurately than in the first embodiment.

(Third Embodiment) FIG. 4 shows a third embodiment of the present invention. In the first embodiment, the two positioning ribs are provided, and the two positioning ribs position the two lenses. However, in the present embodiment, these two positioning ribs can be elastically deformed. With the configuration, the case where the convex shape provided on the two lenses is sandwiched between the two positioning ribs by the elastic restoring force of the self is shown.

Since other configurations and operations are the same as those of the first embodiment, the same reference numerals are given to the same components and the description thereof will be omitted.

FIG. 4 is an enlarged view of the vicinity of the lens positioning portion in the scanning optical device according to the third embodiment of the present invention.

As described above, in the first embodiment, fθ
The convex shape 4c of the first lens 4a and the convex shape 4d of the second lens 4b, which form the lens 4, are formed by the two positioning ribs 10.
Although it was fitted between a and 10b, in the case of a configuration where they are fitted, a positional deviation corresponding to the fitting play occurs.

Therefore, in this embodiment, the positioning ribs 10a and 10b are configured to be elastically deformable, and
The widths of the convex shapes 4c and 4d are set to the positioning ribs 10a and 10b.
It was set slightly larger than the interval.

By inserting the convex shapes 4c and 4d between the positioning ribs 10a and 10b, the positioning rib 10
By elastically deforming a and 10b and sandwiching the convex shapes 4c and 4d, the first lens 4a and the second lens 4b are positioned.

With the configuration of this embodiment, the fitting play that occurs in the first embodiment is eliminated, and the displacement of the lens is eliminated.

Here, when a resin containing 30% glass is used for the optical box 10, if the spacing between the positioning ribs 10a and 10b is made smaller than the width of the convex shapes 4c and 4d by about 5 to 50 μm, the assembling property and the lens are Less likely to affect deformation.

The positioning rib 10b is more easily elastically deformed than the positioning rib 10a (see, for example, FIG. 4).
The width of the positioning rib 10 is made smaller by
It is possible to elastically deform only the positioning rib 10b without substantially deforming a.

By doing so, the positioning rib 10b is formed.
Since it has a pressing function rather than a positioning function, the same effect as in the case of the second embodiment can be obtained.

That is, the convex shape 4c and the convex shape 4d are biased toward the positioning rib 10a by utilizing the elastic restoring force of the positioning rib 10b.
c and side surface of convex shape 4d (contact surface for positioning)
Can be pressed against the reference surface of the positioning rib 10a.

As a result, the side surfaces (contact surfaces) of the convex shape 4c and the convex shape 4d are surely brought into contact with the single reference surface for positioning, so that the first lens 4a and the first lens 4a The two lenses 4b are positioned more accurately than in the first embodiment.

(Fourth Embodiment) FIG. 5 shows a fourth embodiment of the present invention. In the third embodiment, the pair of ribs are elastically deformable so that the pair of ribs can sandwich the convex shape provided on the two lenses by utilizing the elastic restoring force of the pair of ribs. In the present embodiment, one of the pair of ribs is composed of two ribs, and each rib independently sandwiches the convex shape provided on each lens. Indicate the case.

Since other configurations and operations are the same as those of the first embodiment, the same reference numerals are given to the same components and the description thereof will be omitted.

FIG. 5 is an enlarged view of the vicinity of the lens positioning portion in the scanning optical device according to the fourth embodiment of the present invention.

In the third embodiment, the fθ lens 4
The convex shape 4c of the first lens 4a and the convex shape 4d of the second lens 4b, which are included in the above, are inserted between the positioning ribs 10a and 10b. If one convex shape can be made larger than the other convex shape, the widths of the positioning ribs 10a and 10b follow the larger width of the convex shape. Therefore, for the smaller convex shape, the positioning ribs 10a and 10b. There may be a case where a gap is generated between and.

Therefore, in the present embodiment, instead of the positioning rib 10b, the first rib 12a and the second rib 12b which are elastically deformed with respect to the convex shapes 4c and 4d are provided independently.

That is, the convex shape 4 is formed in the gap between the facing ribs.
When the c and 4d are inserted, the first rib 12a has a convex shape 4
The second rib 12b and the second rib 12b independently press the convex shape 4d against the positioning rib 10a.

With this configuration, the fθ lens 4 can be accurately positioned regardless of the dimensional variation of the convex shapes 4c and 4d.

Also in this case, the positioning rib 10a
Is configured so that it hardly deforms, and the first rib 12a
If the second rib 12b is elastically deformed, the first rib 12a and the second rib 12b function as pressing means, and the same effect as that of the second embodiment can be obtained.

Although not shown in the drawings, when the scanning optical apparatus according to the various embodiments described above is applied to an image forming apparatus such as a printer, a facsimile or a copying machine, the image carrier is exposed and scanned. Since the exposure scanning accuracy is improved, the quality of the formed image is also improved. Particularly, in the case of an apparatus that forms a color image by superposing a plurality of images, the effect is particularly large.

(Fifth Embodiment) An image forming apparatus (color image forming apparatus) according to a fifth embodiment will be described with reference to FIGS.

FIG. 6 is a schematic sectional view of an image forming apparatus (color image forming apparatus) according to the fifth embodiment of the present invention.

As shown in the figure, in the color image forming apparatus according to the present embodiment, four scanning optical devices having the same structure are arranged, each of which is cyan (C), magenta (M), yellow (Y). ), Black (BK), and image signals are recorded on the surface of the photoconductor in parallel to form a color image.

In the figure, 51, 52, 53 and 54 are scanning optical devices, 101C, 101M, 101Y and 101.
BK is a photosensitive drum as an image bearing member.

In the present embodiment, the light fluxes (laser light) LC, LM, L each light-modulated based on the image information.
Y and LBK are emitted from the respective optical devices RC, RM, RY and RBK, and the diffractive optical elements 110C, 110M and 110 are output.
After passing through Y and 110BK, the corresponding photosensitive drums 101C, 101M, 101Y and 101BK are irradiated with the respective surfaces to form latent images.

This latent image is formed by the primary chargers 102C and 102C.
Photosensitive drums 101C, 101M, 101Y, 101BK uniformly charged by M, 102Y, 102BK
Formed on the surface.

These latent images are transferred to the developing devices 104C and 104C.
Cyan (C) by M, 104Y, and 104BK,
Transfer rollers 105C, 105M, 105 are formed on the transfer material P that is visualized as images of magenta (M), yellow (Y), and black (BK) and is conveyed on the transfer belt 107.
A color image is formed by sequentially electrostatically transferring Y, 105BK.

The transfer materials P are stacked on the paper feed tray 21, are sequentially fed one by one by the paper feed roller 22, and are registered on the transfer belt 107 by the registration roller 23 in synchronization with the image writing timing. Sent out.

The photosensitive drums 101C, 101M, 101Y, 101BK while being conveyed on the transfer belt 107.
The cyan (C), magenta (M), yellow (Y), and black (BK) images formed on the surface are sequentially transferred onto the transfer material P.
The color image is formed by being transferred on top.

After this, the photosensitive drums 101C, 101M,
The residual toner remaining on the surfaces 101Y and 101BK is removed by the cleaners 106C, 106M, 106Y and 106BK, and the primary chargers 102C, 102M, 102Y and 102BK are again used to form the next color image.
Are uniformly charged by.

The drive roller 24 feeds the transfer belt 107, and a drive motor (not shown) having a small rotational unevenness.
Connected with. The color image formed on the transfer material P is thermally fixed by the fixing device 25, then conveyed by the paper discharge rollers 26 and output to the outside of the apparatus.

FIG. 7 is a diagram for explaining the scanning optical device according to the present embodiment, and is a schematic configuration diagram of the scanning optical device.

As shown in FIG. 7, when the laser light L is deflected and scanned, when the first lens 4a and the second lens 4b, which are scanning lenses, are deformed or the mounting state is biased. Causes a "bend" in the scan line,
A "one-sided magnification difference" occurs in which the left and right magnifications do not match.

When forming a monochrome image, there is no problem unless they are extremely large (for example, 300 μm or more), but when forming a color image, a problem occurs because a plurality of scanning lines are overlapped. That is, in order to form a color image with high definition, it is necessary to sufficiently reduce the "bend" of the scanning lines and the "one-sided magnification difference" to reduce the scanning line deviation between colors.

In particular, when a color image is formed at a high speed by combining a plurality of optical scanning devices and a plurality of image carriers, if the optical parts are simply assembled, the mounting condition may cause a "bend" of the scanning line of each color. The "one-sided magnification difference" varies and cannot be sufficiently overlapped, and it becomes extremely difficult to form a high-definition color image.

This is shown in FIG. FIG. 8 shows a state of "normal scanning line", a state of "bent", and a state of "one-sided magnification difference" in order from the top. It can be seen that the light spots do not exactly overlap in either case.

On the other hand, a technique relating to a scanning optical device for dealing with such a problem is disclosed in Japanese Patent Laid-Open No. 2001-19460.
9 publications.

As an example thereof, as shown in FIGS. 9 and 10, holding surfaces 111 provided on the left and right sides hold the curved surface portion formed on the lower surface of the fθ lens 4 which is a scanning lens.
Further, an adhesive base 112 for adhesively fixing the fθ lens 4 is provided at an intermediate position between these holding bases 111.

There is a gap 113 between the fθ lens 4 and the bonding base 112. First, this gap 113 is filled with an ultraviolet curable adhesive 114.

Then, as shown in FIG. 11, the position and orientation of the diffractive optical element 108 are adjusted. That is, arrows C and D
By moving the fθ lens 4 in the direction of, the "bending" and "one-sided magnification difference" of the scanning line are sufficiently corrected, and then the adhesive 11
4 is cured. This makes it possible to adjust the mounting state of the optical component with high accuracy.

However, when the position of the fθ lens 4 is moved by several tens of μm in the arrow direction due to impact or thermal expansion after the adjustment, a one-sided magnification difference occurs.

In the present embodiment, in order to avoid this, the configuration of the scanning optical device according to the third and fourth embodiments is adopted, and the first lens 4a constituting the fθ lens 4 is adopted.
The convex shape 4c is fitted to the positioning rib 10a without a gap.

With the above-described structure, the first lens 4a constituting the fθ lens 4 is prevented from moving after the adjustment due to impact or thermal expansion, and the occurrence of the one-sided magnification difference is suppressed.

FIG. 12 is a graph showing the effect of suppressing the one-sided magnification difference when the present embodiment is used. FIG. 12 shows the variation of the one-sided magnification difference with respect to the temperature change.

Graph A shows that the convex shape 4c of the first lens 4a constituting the fθ lens 4 is provided in the center of the lens and the rib 1 is formed.
It shows the change in one-sided magnification when fitting to 0a without a gap.

The graph B shows the change in half magnification when the convex shape 4c of the first lens 4a constituting the fθ lens is provided in the center of the lens and the convex shape 4c is fitted in the rib 10a with a gap.

Graph C represents a change in one-side magnification when the convex shape 4c of the first lens 4a constituting the fθ lens is provided at the lens end and the convex shape 4c is fitted in the rib 10a with a gap. .

From FIG. 12, it is understood that when the convex shape 4c of the first lens 4a constituting the fθ lens is fitted to the rib 10a without a gap, the variation of the one-sided magnification difference is suppressed. Also,
It can be understood that the provision of the convex shape 4c at the center of the fθ lens 4 in the deflection scanning direction (the center of the scanning region) can suppress the fluctuation of the one-sided magnification difference more than that at the end portion in the deflection scanning direction.

[0098]

As described above, according to the present invention, the positioning accuracy of the lens can be improved and the scanning exposure accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a scanning optical device according to a first embodiment of the present invention.

FIG. 2 is a view with a lid removed in FIG.

FIG. 3 is an enlarged view of the vicinity of a lens positioning portion in the scanning optical device according to the second embodiment of the present invention.

FIG. 4 is an enlarged view of the vicinity of a lens positioning portion in a scanning optical device according to a third embodiment of the present invention.

FIG. 5 is an enlarged view of the vicinity of a lens positioning portion in a scanning optical device according to a fourth embodiment of the present invention.

FIG. 6 is a schematic sectional view of an image forming apparatus (color image forming apparatus) according to a fifth embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a scanning optical device according to the present embodiment.

FIG. 8 is a diagram showing a state of a light spot in various states.

FIG. 9 is a configuration diagram of a lens holding unit in a scanning optical device according to a conventional technique.

FIG. 10 is a configuration diagram of a lens holding unit in a scanning optical device according to a conventional technique.

FIG. 11 is a diagram illustrating lens holding adjustment in a scanning optical device according to a conventional technique.

FIG. 12 is a diagram showing a change in one-sided magnification difference with respect to a temperature change.

FIG. 13 is a schematic diagram of an optical system in an exposure scanning device according to a conventional technique.

[Explanation of symbols]

1 Semiconductor Laser Device 1a Collimator Lens 2 Cylindrical Lens 3 Rotating Polygonal Mirror 3b Scanner Motor 4 fθ Lens 4 4a First Lens 4b Second Lens 4c, 4d Convex Shape 5 Folding Mirrors 10a, 10b Positioning Rib 10 Optical Box 11 Spring 12a 1st Rib 12b Second rib 21 Paper feed tray 22 Paper feed roller 23 Registration roller 24 Drive roller 25 Fixer 26 Paper ejection roller 101C, 101M, 101Y, 101BK Photosensitive drum 102a Collimator lens 102c Cylindrical lens 102C, 102M, 102Y, 102BK Primary Charger 103 Polygon mirror 103a Scanner motor 104 fθ lens 104a Spherical lens 104b Toric lens 104C, 104M, 104Y, 104BK Developer

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Claims (14)

[Claims] 1. A scanning optical system comprising: a pair of first and second lenses for scanning a deflected and scanned light beam onto a surface to be scanned; and an optical box for housing the first and second lenses. In the apparatus, a positioning portion for the optical box provided on the first lens and a positioning portion for the optical box provided on the second lens are provided so as to face each other, and A scanning optical device, wherein a positioning rib for positioning both the first lens and the second lens is provided in the optical box. 2. The positioning rib has a reference surface with which a positioning contact surface provided on the first lens contacts, and a positioning surface provided with the second lens that contacts the reference surface. The scanning optical device according to claim 1, wherein the reference surface and the reference surface are provided on the same surface. 3. The optical box is provided with a pair of the positioning ribs so as to face each other, and the first lens and the second lens are each provided with a positioning convex portion. Since the convex portion is sandwiched between the pair of positioning ribs, the first lens and the second lens
The lens is positioned so that the lens can be positioned.
The scanning optical device according to item 1. 4. At least one of the pair of positioning ribs is elastically deformable, and the positioning convex portion is sandwiched by its elastic restoring force.
The scanning optical device according to item 1. 5. A pressing means for pressing the abutting surfaces for positioning provided on each of the first lens and the second lens against a reference surface of the positioning rib. 2. The scanning optical device according to item 2. 6. The scanning optical device according to claim 5, wherein the pressing means is a spring. 7. The scanning optical device according to claim 5, wherein the pressing means is a rib that exerts a pressing action by its elastic restoring force. 8. The ribs exhibiting the pressing action are provided on the second lens and a first rib for pressing an abutting surface provided on the first lens against a reference surface of the positioning rib. The scanning optical device according to claim 7, further comprising: a second rib that presses the contact surface against the reference surface of the positioning rib. 9. The positioning unit for the optical box, which is provided in each of the first lens and the second lens, is provided near the center of the scanning area. The scanning optical device according to one. 10. A scanning optical device according to claim 1, an image carrier on which an electrostatic latent image is formed by exposure scanning by the scanning optical device, and on the image carrier. A developing unit for developing the electrostatic latent image formed on the sheet; a transferring unit for transferring the image developed by the developing unit onto a sheet; and an image transferred on the sheet by the transferring unit for transferring the image onto the sheet. An image forming apparatus comprising: a fixing unit configured to fix the image on the image forming apparatus. 11. The image forming apparatus according to claim 10, wherein a plurality of the scanning optical devices are provided for each color so that a color image can be formed. 12. A pair of a first lens and a second lens for scanning a deflected and scanned light beam, and the first lens and the second lens.
A scanning optical device having an optical box containing a lens, an image carrier on which an electrostatic latent image is formed by exposure scanning by the scanning optical device, and an electrostatic latent image formed on the image carrier. Developing means for developing the image, a transfer means for transferring the image developed by the developing means onto a sheet, and a fixing means for fixing the image transferred on the sheet by the transfer means onto the sheet, In the image forming apparatus including: the at least one of the first lens and the second lens is provided with a convex portion for positioning with respect to the optical box, and the optical box has the convex portion. An image forming apparatus, characterized in that a holding portion for elastically holding is provided. 13. The image forming apparatus according to claim 12, wherein the holding portion is composed of a pair of ribs, and at least one of the ribs holds the convex portion by its elastic restoring force. . 14. The image forming apparatus according to claim 12, wherein the convex portion is provided near the center of the scanning area.