JPH11237568A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aligner for reducing the deviation of respective beams from each other, accurately superposing one on another images and preventing the occurrence of color slippage or blurring and blotting of lines by keeping in a prescribed range the deviation of fluctuations in the light intensity on the image surfaces irradiated with respective plural light sources. SOLUTION: The deviation of fluctuations in the light intensity on the image surfaces irradiated with respective plural light sources is kept in a prescribed range. This exposure device 1 is provided with only one deflection device 5 as a means for deflecting at a prescribed linear velocity the laser beams emitted from 2×4=8 of the laser elements as light sources on the image surfaces arranged at prescribed positions of respective photosensitive body drums 58Y, 58M, 58C and 58B of first-forth image formation parts 50Y, 50M, 50C and 50B. Then, in the device, fluctuations in the light intensity on the image surfaces of the respective beams are within 2%--2% against a design value. Also, fluctuations of the beam diameters of the respective beams on the image surfaces are within 10%--10% against a design value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-drum type color printer or color copier, a multicolor color printer or color copier, and a single-color high-speed laser printer or high-speed digital copier using a plurality of exposure beams. The present invention relates to an exposure apparatus that is used and collectively exposes and scans a plurality of light beams.

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as a color printer or a color copying apparatus using an image forming unit including a plurality of photosensitive drums, a plurality of image data corresponding to color components separated, that is, at least an image. Exposure devices that provide a plurality of light beams equal to the number of forming units are used.

An exposure apparatus of this type includes a plurality of semiconductor laser elements that emit a predetermined number of light beams corresponding to image data of each color component separated by color, and a cross section of each light beam emitted from each semiconductor laser element. A first lens group for narrowing the beam diameter to a predetermined size and shape, and a light beam group narrowed to a predetermined size and shape by the first lens group continuously in a direction orthogonal to the direction in which the recording medium is conveyed. Device for deflecting by optically reflecting light, and a second device for forming an image of a light beam deflected by the deflecting device at a predetermined position on a recording medium
Lens group and the like.

The above-described exposure apparatus uses a plurality of exposure apparatuses corresponding to each image forming unit in accordance with the image forming apparatus to be applied, and a multi-exposure apparatus in which each light beam can be provided by one exposure apparatus. It is classified into an example using a beam exposure apparatus. In order to increase the image forming speed and improve the resolution, a high-speed printer capable of forming an image at a high speed by exposing image data of the same color in parallel has been proposed.

[0005]

In the above-described exposure apparatus, a plurality of light beams are used.
It is necessary to make the cross-sectional beam diameter of each light beam and the wavelength and light intensity of the light beam emitted from each laser element uniform.

However, the cross-sectional beam diameter of each light beam may vary due to the variation (deviation) in the characteristics of the optical elements of the first and second lens groups located between each laser element and the recording medium and the radiation of the laser element. It is known that the variation (deviation) of the radiation (divergence) angle of a light beam is different for each laser element.

It is also known that the wavelength and light intensity of a light beam emitted from each laser element is different for each laser element. It is also known that the wavelength of a light beam (laser beam) emitted from a laser element changes according to the temperature of the environment in which the laser element is installed, and that the amount of change (mode hopping) with respect to a temperature change differs for each laser element. ing.

[0008] This causes phenomena such as color misregistration and inability to reproduce a predetermined color in a color printer device. In a high-speed printer device, this causes a decrease in resolution and jitter, and a thin line. This causes problems such as uneven spacing.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multi-beam exposure apparatus for exposing a plurality of beams, the effects of the deviation of the cross-sectional beam diameter of the light beams and the fluctuation of the light intensity and wavelength of the light beam emitted from each laser element. It is an object of the present invention to provide an exposure apparatus which is less susceptible to color shifts, does not cause color shift, lowering of resolution and non-uniform spacing of fine lines.

[0010]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned problems, and has a plurality of light sources; a pre-deflection optical means for giving predetermined characteristics to light from the plurality of light sources; An exposure apparatus comprising: a deflecting unit that deflects light from the front optical unit in a first direction; and a lens that forms light deflected by the deflecting unit on a predetermined image plane at a constant speed. It is an object of the present invention to provide an exposure apparatus characterized in that the deviation of the light intensity variation on the image plane of the light emitted from each of the light sources is within a predetermined range.

Further, the present invention provides a plurality of light sources, pre-deflection optical means for giving predetermined characteristics to light from the plurality of light sources, and a deflection device for deflecting light from the pre-deflection optical means in a first direction. Means, and a lens for imaging the light deflected by the deflecting means on a predetermined image plane at a constant speed, wherein the deviation of the divergence angle variation of the light emitted by each of the plurality of light sources is determined. An exposure apparatus is provided which has a predetermined range.

Further, the present invention provides a plurality of light sources, pre-deflection optical means for giving predetermined characteristics to the light from the plurality of light sources, and a deflection unit for deflecting the light from the pre-deflection optical means in a first direction. A lens provided for each of said plurality of light sources of said pre-deflection optical means in an exposure apparatus comprising: means for forming an image of light deflected by said deflecting means on a predetermined image plane at a constant speed. An exposure apparatus characterized in that the deviation of the focal length variation is within a predetermined range.

[0013] Still further, the invention provides a plurality of light sources,
Pre-deflection optical means for imparting predetermined characteristics to the light from the plurality of light sources; deflection means for deflecting the light from the pre-deflection optical means in a first direction; A lens that forms an image on the image plane at a constant speed, wherein the upper limit of the deviation of the light intensity variation of the light emitted by each of the plurality of light sources on the image plane is 2%;
An exposure apparatus characterized in that the lower limit is set to -2%.

Still further, the present invention provides a plurality of light sources,
Pre-deflection optical means for imparting predetermined characteristics to the light from the plurality of light sources; deflection means for deflecting the light from the pre-deflection optical means in a first direction; In an exposure apparatus having a lens that forms an image on an image plane at a constant speed, an upper limit value of a deviation of a variation of a divergence angle of light emitted by each of the plurality of light sources is set to 10%, and a lower limit value is set to −10%. An exposure apparatus is provided.

Still further, the present invention provides a plurality of light sources,
Pre-deflection optical means for imparting predetermined characteristics to the light from the plurality of light sources; deflection means for deflecting the light from the pre-deflection optical means in a first direction; An exposure apparatus having a lens that forms an image on an image plane at a constant speed, wherein an upper limit value of a deviation of a variation of a focal length of a lens provided for each of the plurality of light sources of the pre-deflection optical unit is 10%; It is an object of the present invention to provide an exposure apparatus wherein the lower limit is set to -10%.

Further, the present invention provides a plurality of light sources,
Pre-deflection optical means for imparting predetermined characteristics to the light from the plurality of light sources; deflection means for deflecting the light from the pre-deflection optical means in a first direction; A lens that forms an image on an image plane at a constant speed, wherein a deviation of a beam diameter variation at an image plane position of light emitted by each of the plurality of light sources is set to a predetermined range. An exposure apparatus is provided.

Still further, the present invention provides a plurality of light sources,
Pre-deflection optical means for imparting predetermined characteristics to the light from the plurality of light sources; deflection means for deflecting the light from the pre-deflection optical means in a first direction; An exposure apparatus having a lens that forms an image on an image plane at a constant speed, wherein an upper limit value of a deviation of a variation of a beam diameter at an image plane position of light emitted by each of the plurality of light sources is 10%, and a lower limit value is −. An exposure apparatus characterized in that it is set to 10%.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a color image forming apparatus using an exposure apparatus according to an embodiment of the present invention. In this type of color image forming apparatus, color separation is usually performed for each color component of Y, ie, yellow, M, ie, magenta, C, ie, cyan, and B, ie, black (black) (black is for inking). Since four types of image data and four sets of various devices for forming an image for each color component corresponding to each of Y, M, C and B are used, four reference codes are used.
By adding Y, M, C, and B, the image data for each color component and the corresponding device are identified.

As shown in FIG. 1, an image forming apparatus 10
0 is a color component separated by color separation, that is, Y = yellow, M =
First to fourth image forming units 50Y and 5 that form images for each of magenta, C = cyan, and B = black (black)
0M, 50C and 50B.

Each image forming section 50 (Y, M, C and B)
Is an exposure apparatus 1 described later with reference to FIGS. 2 and 5.
The light is emitted from the exposure apparatus 1 to the outside by a first mirror 33B used for exposing a black image in the inside, and third mirrors 37Y, 37M and 37C used for exposing respective images of yellow, magenta and cyan. Sets of laser beams L (Y, M, C and B) as image light
At positions corresponding to each of 50Y, 50M, 50C
And 50B in series.

Each image forming section 50 (Y, M, C and B)
Below, is a transport belt 52 that transports a transfer target such as a recording sheet as a transfer material onto which an image formed by each image forming unit 50 (Y, M, C, and B) is transferred.
Is arranged.

The transport belt 52 is wound around a belt driving roller 56 and a tension roller 54 rotated in the direction of the arrow by a motor (not shown), and is rotated at a predetermined speed in the direction in which the belt driving roller 56 is rotated. .

Each image forming section 50 (Y, M, C and B)
Have photoreceptor drums 58Y, 58M, 58C and 58B formed in a cylindrical shape rotatable in the direction of the arrow and on which an electrostatic latent image corresponding to the image exposed by the exposure device 1 is formed.

Around the photosensitive drums 58 (Y, M, C and B), charging devices 60Y and 6 for providing a predetermined potential to the surfaces of the photosensitive drums 58 (Y, M, C and B).
0M, 60C and 60B, and each photosensitive drum 58 (Y,
M, C, and B) developing devices 62Y, 62M, 62C, and 62B for developing by supplying toner having a color corresponding to the electrostatic latent image formed on the surface of each of the photosensitive drums 58 (Y , M, C, and B), each of which is opposed to each of the photosensitive drums 58 (Y, M, C, and B) from the back surface of the transport belt 52 with the transport belt 52 interposed therebetween.
Each of the photosensitive drums 58 (Y, M, C, and B) is applied to a recording medium, that is, a recording sheet P conveyed by the conveyance belt 52.
Transfer devices 64Y, 64M, 64C for transferring toner images
And 64B, each transfer device 64 (Y, M, C and B)
66 (Y, M, C, and B) for removing the residual toner on the photosensitive drum 58 (Y, M, C, and B) that is not transferred when the toner image is transferred to the sheet P by the printer and each transfer A static eliminator 68 for removing the residual potential remaining on the photosensitive drum 58 (Y, M, C and B) after the transfer of the toner image by the device 64 (Y, M, C and B).
(Y, M, C and B) correspond to the respective photosensitive drums 58 (Y, M, C).
M, C and B) are arranged in order along the direction in which they are rotated.

The mirrors 37Y and 37Y of the exposure apparatus 1
The laser beams LY, LM, LC and LB guided to the respective photosensitive drums 58 by M, 37C and 33B
Are the mirrors 37Y, 37M, 37C and 3
Each of the photosensitive drums 58 (Y,
M, C, and B), in the sub-scanning direction, N _i lines, in this example, each of the two laser beams LY, LM, LC, and LB (N ₁ = N ₂ = N ₃ = N ₄ = 2) ), And is irradiated between each charging device 60 (Y, M, C and B) and each developing device 62 (Y, M, C and B).

Below the transport belt 52, a paper cassette 70 containing recording paper P on which an image formed by each of the image forming units 50 (Y, M, C, and B) is transferred is disposed. .

On one end of the paper cassette 70 and on the side close to the tension roller 54, a delivery roller 72 which is formed in a substantially half-moon shape and takes out the paper P stored in the paper cassette 70 one by one from the top. Is arranged.

Delivery roller 72 and tension roller 5
4, an aligning roller 74 for aligning the leading end of one sheet P taken out of the cassette 70 with the leading end of the toner image formed on the photosensitive drum 58B of the black image forming unit 50B is arranged. ing.

In the vicinity of the tension roller 54 between the aligning roller 74 and the first image forming portion 50Y,
At a position facing the outer periphery of the transport belt 52 corresponding to a position where the tension roller 54 and the transport belt 52 are in contact with each other, a predetermined electrostatic attraction is applied to one sheet of paper P transported at a predetermined timing by the aligning roller 72. A suction roller 76 for providing a force is arranged.

Near one end of the conveyor belt 52 and in the vicinity of the belt driving roller 56, substantially the belt driving roller 5
6 is provided on the outer periphery of the transport belt 52 in contact with the transport belt 5.
Registration sensors 78 and 80 for detecting the position of the image formed on the sheet 2 or the image transferred on the sheet P,
The belt driving roller 56 is disposed at a predetermined distance in the axial direction (since FIG. 1 is a front sectional view, the first sensor 78 positioned in front of the paper in FIG. 1 is not visible).

At a position on the outer periphery of the transport belt 52 in contact with the belt driving roller 56 and not in contact with the sheet P transported by the transport belt 52, the transport belt 52
A transport belt cleaner 82 for removing the toner adhered thereon or the paper P of the paper P is disposed.

In the direction in which the sheet P conveyed by the conveying belt 52 is separated from the tension roller 56 (conveying belt 52) and further conveyed, a fixing device 84 for fixing the toner image transferred on the sheet P to the sheet P is provided. Is arranged.

Next, the exposure apparatus used in the image forming apparatus shown in FIG. 1 will be described in detail. FIG. 2 shows a schematic view of the optical path of the exposure apparatus shown in FIG. 1 developed from a plane direction, and FIG. 3 shows a section between the deflecting device 5 of the exposure apparatus 1 and each photosensitive drum 58, that is, the image plane. With respect to the optical members to be arranged, a state where the deflection angle of the deflecting device 5 is 0 ° and viewed from the sub-scanning direction is shown.

As shown in FIG. 2, the exposure apparatus 1 applies a laser beam emitted from a 2 × 4 = 8 laser element as a light source to an image plane arranged at a predetermined position, that is, FIG.
, The first to fourth image forming units 50Y, 50M,
Each of the photoconductor drums 58Y of 50C and 50B,
58M, 58C, and 58B (in FIG. 2, the first to third mirrors for guiding each laser beam to each photoconductor are omitted, and are representatively shown as photoconductor drums corresponding to arbitrary colors). It has only one deflecting device 5 as deflecting means for deflecting at a predetermined linear velocity toward the position. Hereinafter, the direction in which the laser beam is deflected by the deflecting device 5 is referred to as a main scanning direction. A direction perpendicular to the main scanning direction and parallel to each reflecting surface of the polygon mirror 5a of the deflecting device 5 is referred to as a sub-scanning direction.

The deflecting device 5 has a polygonal mirror body 5 in which a plurality of, for example, eight plane reflecting mirrors (surfaces) are arranged in a regular polygonal shape.
a and a motor 5b for rotating the polygon mirror body 5a at a predetermined speed in the main scanning direction. Polyhedral mirror body 5a
Is formed of, for example, aluminum. Also,
Each of the reflection surfaces of the polygon mirror 5a has a plane including a direction in which the polygon mirror body 5a is rotated, that is, a plane orthogonal to the main scanning direction, that is, a plane that is cut out along the sub-scanning direction.
For example, a surface protective layer such as silicon dioxide (SiO ₂ ) is provided by being deposited.

A deflecting device 5 is provided between the deflecting device 5 and the image plane.
A post-deflection optical system 21 that gives predetermined optical characteristics to the laser beam L (Y, M, C, and B) deflected in a predetermined direction by each reflection surface is disposed.

The post-deflection optical system 21 adjusts each laser beam L (Y, M, C and B) deflected by the deflecting device 5 in order to adjust the horizontal synchronization.
, A horizontal synchronization mirror 25 that folds each laser beam L toward the horizontal synchronization photodetector 23, and first and second imaging lenses 30a and 30b.
To optimize the shape and position of the laser beam L (Y, M, C, and B) deflected by each reflecting surface of the polygon mirror 5a on the image plane (the photosensitive drum 58 in FIG. 1). It has a combined imaging lens 30.

As shown in FIG. 3, an image is formed between the second imaging lens 30b of the two-piece imaging lens 30 and each of the photosensitive drums 58 (Y, M, C and B). Image lens 3
The laser beams L (Y, M, C, and B) emitted from the plurality of mirrors 33Y (the first yellow color) guide the photosensitive drums 58 (Y, M, C, and B) corresponding to the respective laser beams. ), 35Y (second yellow), 3
7Y (yellow third), 33M (magenta first), 35
M (magenta second), 37M (magenta third), 33C
(Cyan first), 35C (Cyan second), 37C (Cyan third), 33B (for black) and dustproof glass 39 (Y,
M, C and M) are provided.

More specifically, between the second imaging lens 30b of the post-deflection optical system 21 and the image plane, 2 + 2 + 2 + 2 = 8 laser beams L (Y, Y,
A first mirror 33 (Y, M, C and B) for bending M, C and B) toward the image plane, and a first mirror 33
The second and third mirrors 35Y, 35M, 35C, and 37 further fold the laser beams LY, LM, and LC bent by Y, 33M, and 33C.
Y, 37M and 37C are arranged. The laser beam LB corresponding to the black image B is guided by the first mirror 33B to the image plane without passing through another mirror.

The first and second imaging lenses 30a and 30b, the first mirror 33 (Y, M, C and B), and the second mirrors 35Y, 35M and 35C are respectively It is fixed to the intermediate base 1a by, for example, bonding to a plurality of fixing members (not shown) formed by integral molding. Also, the third mirror 37Y,
37M and 37C are movably arranged in at least one direction related to a direction perpendicular to the mirror surface by a fixing rib and an inclination adjusting mechanism described later with reference to FIG.

Next, the pre-deflection optical system provided between the light source (ie, the laser element) and the deflection device will be described in detail with reference to FIG. As already described, the exposure apparatus 1 includes the first and second two (N ₁ = N ₂ = N ₃ = N ₄ = 2) satisfying N _i (i is a positive integer) for yellow and magenta. M sets (M is a positive integer, M = 4) that generate laser beams corresponding to image data that has been color-separated into color components. Light sources 3Y, 3M, 3C and 3B.

The first to fourth light sources 3Y, 3M, 3C and 3B are respectively a yellow first laser 3Ya for emitting a laser beam corresponding to Y, that is, a yellow image.
And magenta first laser 3Ma and magenta second laser 3Mb, C, which emit a laser beam for a magenta image, that is, a cyan first laser that emits a laser beam for a cyan image.
Laser 3Ca and cyan second laser 3Cb, and B
That is, the first black laser 3Ba and the second black laser 3Ba for emitting a laser beam corresponding to a black (black) image (for inking).
It has a laser 3Bb. In addition, from each laser element, two laser beams LYa and LYb, LMa and LMb, LCa and LCb
And LBa and LBb are emitted.

Each of the laser elements 3Ya, 3Ma, 3
Between Ca and 3Ba and 3Yb, 3Mb, 3Cb and 3Bb and the deflecting device 5, laser beams LYa, LMa and LCa from the respective laser elements 3Ya, 3Ma, 3Ca and 3Ba and LBa and laser beams LYb, LMb, A pre-deflection optical system 7 for adjusting the cross-sectional beam spot shapes of LCb and LBb to a predetermined shape is arranged.

Hereinafter, the pre-deflection optical system 7B will be used as a representative example, and a laser beam LBa guided from the first black laser 3Ba to the deflection device 5 and a laser beam LBb guided from the second black laser 3Bb to the deflection device 5 will be described. The relationship between the laser beam and the cylinder lens 12B and the half mirror 11B will be described.

The divergent laser beam LBa emitted from the first black laser 3Ba is given a predetermined convergence by the finite focus lens 9Ba. The laser beam LBa is guided to the half mirror 11B after the cross-sectional beam shape is shaped into a predetermined shape by the stop 10Ba. This laser beam LBa passes through the half mirror 11B and enters the cylinder lens 12B. This cylinder lens 12
The laser beam LBa incident on B is further converged only in the sub-scanning direction by the lens 12B and guided to the deflecting device 5.

Similarly, the divergent laser beam LBb emitted from the black second laser 3Bb is
b gives a predetermined convergence. Laser beam LB
b is guided toward the half mirror 11B after the cross-sectional beam shape is shaped into a predetermined shape by the stop 10Bb.
The laser beam LBb is provided on the surface of the half mirror 11B opposite to the surface on which the laser beam LBa from the first black laser 3Ba is incident, in the sub-scanning direction with respect to the laser beam LBa from the first black laser 3Ba. The light is incident so as to have a beam interval, is further reflected by the half mirror 11B, and is incident on the cylinder lens 12B.

The laser beam LBb incident on the cylinder lens 12B is transmitted to the lens 1 similarly to the laser beam LBa.
The light is further converged only in the sub-scanning direction by 2B, and guided to the deflecting device 5.

As the finite focus lenses 9Ba and 9Bb, as shown in FIG. 4, an aspherical glass lens or a single lens obtained by bonding a plastic aspherical lens (not shown) to a spherical glass lens is used. As the plastic aspherical lens, a UV-curable plastic lens that is cured by being irradiated with ultraviolet rays is preferably used. Each of the finite focus lenses 9Ba and 9Bb is given substantially the same characteristics as described later with reference to Tables 1 to 3. The finite focus lens provided for each laser element has a size of 9B.
a and 9Bb, 9Ya and 9Yb, 9Ma and 9
Mb and 9Ca and 9Cb in total, and Table 2
The upper limit (+) 10 is set to the basic characteristic (design value) of the focal length so as to satisfy the condition described later using
%, And the lower limit (-) is set to be within 10%.

The half mirror 11B has a transmittance and a reflectance controlled to a predetermined ratio by depositing a metal film on one surface of a parallel plate glass having the same thickness and the same material. tm is formed to 5 mm.

The cylinder lens 12B is made of, for example, PMMA
A plastic cylinder lens 17B made of (polymethyl methacrylate) and having a section in the sub-scanning direction formed on a part of the cylindrical surface so that a surface (light source side surface) in contact with air has power in the sub-scanning direction; Glass cylinder lens 19B formed of (low dispersion optical glass)
Is a hybrid lens integrally formed by bonding or pressing from a predetermined direction toward a positioning member (not shown). For this reason, the curvature in the sub-scanning direction of the surface where the plastic cylinder lens 17B and the glass cylinder lens 19B are in contact is set to be equal. Note that the plastic cylinder lens 17B may be integrally formed with the glass cylinder lens 19B.

The laser beams LBa and LBb incident on the cylinder lens 12B are decentered and inclined in the sub-scanning direction with respect to the optical axis of the cylinder lens 12B, and are incident on the cylinder lens 12B. In other words, the cylinder lens 12B emits laser beams LBa and LBb from the half mirror 11B to the deflecting device 5.
First and second of the two-piece imaging lens 30 of the post-deflection optical system 21
Are arranged so that the coma aberration component generated when the light passes through the imaging lenses 30a and 30b can be canceled. The laser beam LBb is asymmetrically incident on the laser beam LBa with respect to the optical axis of the cylinder lens.

Each of the laser beams LBa and LBb, which are given a predetermined beam interval in the sub-scanning direction by the half mirror 11B and are substantially combined into one laser beam, are transmitted to the deflecting device 5 of the laser combining mirror 13 most. The light is reflected by the adjacent reflecting surface 13 </ b> B and guided to the deflection device 5.

The yellow laser beams LYa and LYb of each laser beam pass through the non-reflection area 13Y of the combining mirror 13 described later with reference to FIG. Also, magenta laser beams LMa and LMb of each laser beam
Is reflected by a reflecting surface 13M provided at a position farthest from the deflecting device 5 of the combining mirror 13 described later with reference to FIG. On the other hand, the cyan laser beams LCa and LCb are reflected by the reflecting surface 13C provided between the reflecting surface 13M and the reflecting surface 13B and guided to the deflecting device 5. Hereinafter, Table 1 shows optical numerical data of the pre-deflection optical system 7.

[0054]

[Table 1]

As is apparent from Table 1, the finite focal length lens 9 and the cylinder lens 12 corresponding to each color component use the same lens for each color component by itself.

FIG. 5 shows a laser beam L (Y, M, C and B) passing through the pre-deflection optical system 7 (Y, M, C and B).
6 is a schematic diagram illustrating a positional relationship in the sub-scanning direction on each reflecting surface of the deflecting device 5. FIG.

As is apparent from FIG. 5, the respective laser beams LY, LM, LC and LB are arranged at mutually different intervals in a direction parallel to the rotation axis of the reflecting surface of the deflecting device 5.
It is guided to the deflection device 5. The distance between the laser beams LY, LM, LC and LB on each reflecting surface of the deflecting device 5 is 3.20 mm between LY and LM, 2.70 mm between LM and LC, and 2 between LC and LB. .30 mm. This is also consistent with the results shown in Tables 1 to 3.

Next, the post-deflection optical system 21 will be described. The laser beams LBa and LBb guided to the deflecting device 5 are deflected substantially linearly by the rotation of each reflecting surface of the polygon mirror 5 a of the deflecting device 5, and are deflected in a substantially linear manner.
The light is incident on the incident surface of the first imaging lens 30a of the sheet imaging lens 30 at a predetermined angle.

Hereinafter, the laser beams LBa and LBb
The second imaging lens 30b gives predetermined convergence and direction so that the shape and size of the beam spot on the surface of the photosensitive drum 58B become a predetermined shape and size. Is reflected at a predetermined angle, passes through the dustproof glass 39B, and passes through the photosensitive drum 58.
B is irradiated.

Next, the optical characteristics between the cylinder lens 12 and the post-deflection optical system will be described in detail. The post-deflection optical system 21, that is, the first and second imaging lenses 30a and 30b of the doublet lens 30 are made of plastic, for example, PMM.
A, the ambient temperature is, for example, 0 °
By changing between C and 50 ° C., the refractive index n becomes
It is known to vary from 1.4876 to 1.4789. In this case, the first and second lenses 30a, 30
The image plane on which the laser beam passed through b is actually focused, that is, the image position in the sub-scanning direction is ± 12
mm.

On the other hand, a lens made of the same material as that of the lens used for the post-deflection optical system 21 is incorporated in the pre-deflection optical system 7 shown in FIG. 4 with the curvature being optimized. In addition, it is possible to suppress the fluctuation of the imaging plane caused by the fluctuation of the refractive index n due to the temperature change to about ± 0.5 mm. That is, the cylinder lens 12 of the pre-deflection optical system 7
Is a glass lens, and the post-deflection optical system 21 is a sub-scanning direction caused by a change in the refractive index due to a change in the temperature of the lens of the post-deflection optical system 21 as compared with a conventional optical system formed of a plastic lens. Can be corrected.

However, the amount of chromatic aberration that can be corrected is proportional to the power of the plastic cylinder lens 17. That is, the amount of chromatic aberration that can be corrected is determined according to the difference between the curvature of the entrance surface and the curvature of the exit surface of the plastic cylinder lens 17.
If the entrance surface of 7 is a flat surface, this specifies the curvature of the glass cylinder lens 19. Therefore, when the material used for the glass cylinder lens 19 is specified, the focal length of the cylinder lens 12 is determined.

From this, when the optical characteristics of the post-deflection optical system are specified, the minimum beam diameter in the sub-scanning direction is:
The setting can be made only by the focal length of the cylinder lens 12. In this case, the degree of freedom in design cannot be secured, and there is a possibility that obtaining a target beam diameter and achromatism may not be compatible.

It is to be noted that there is a method of setting the focal length of the cylinder lens 12 by adjusting the focal length of the glass cylinder lens 19 by changing the refractive index by changing the glass material, but depending on the glass material, , Not always beneficial for grinding, storage or transport,
It is inevitable that the degree of freedom decreases.

It is also possible to provide a curvature to each of the entrance surface and the exit surface of the glass cylinder lens 19 so that the power of the plastic cylinder lens 17 and the power of the cylinder lens 12 are independent functions.

However, a curvature is given to both sides of the plastic cylinder lens 17 formed by molding, and the power of the plastic cylinder lens 17 and the cylinder lens 1
The cost can be reduced most by the above method in which the power of 2 is an independent function. Further, according to the above method, processing accuracy and shape accuracy can be easily ensured.

FIG. 6 shows first to fourth combined laser beams L (Y, Y, L) passing between the deflecting device 5 and the image plane.
M, C and B) and the optical axis of the system in the sub-scanning direction of the exposure apparatus 1 are shown.

As shown in FIG. 6, the first to fourth combined laser beams L (Y, M, C, and B) reflected by the reflecting surface of the deflecting device 5 respectively have the first combination. Between the image lens 30a and the second image forming lens 30b, in the sub-scanning direction, the light is guided to the image plane, crossing the optical axis of the system.

FIG. 7 shows a laser combining mirror 13 for guiding the first to fourth combined laser beams LY, LM, LC, and LB as one bundle of laser beams to each reflecting surface of the deflecting device 5. It is shown.

The first to third mirrors 13M, 13M, which are arranged by a number smaller by "1" than the number of color components capable of forming an image (the number of color-separated colors).
13C and 13B and respective mirrors 13M and 13
It comprises first to third mirror holding portions 13α, 13β and 13γ for holding C and 13B and a base 13a for supporting the respective holding portions 13α, 13β and 13γ. The base 13a and the holding portions 13α, 13β, and 13γ are integrally formed of, for example, an aluminum alloy having a low coefficient of thermal expansion.

At this time, the light source 3Y, that is, the yellow first light
The laser beams LY from the laser 3Ya and the second yellow laser 3Yb are guided directly to the respective reflecting surfaces of the deflecting device 5 as described above. In this case, the laser beam L
Y passes through a passage area 13Y between the mirror 13M fixed to the first holding portion 13α and the base 13a with respect to the base 13a with respect to the optical axis of the system of the exposure apparatus 1.

Next, each laser beam L (M, C and B) reflected by each of the mirrors 13M, 13C and 13B of the combining mirror 13 and guided to the deflecting device 5, and the laser beam directly guided to the deflecting device 5 Consider the light intensity (light amount) of the beam LY.

According to the combining mirror 13, the respective laser beams LM, LC and LB are incident on the respective reflecting surfaces of the deflecting device 5, and the respective laser beams LM, LC and L
In the area where B is separated in the sub-scanning direction, it is folded back by normal mirrors (13M, 13C and 13B). Therefore, each reflecting surface (13M, 13C and 13B)
The amount of each of the laser beams L (M, C, and B) supplied to the polygon mirror main body 5a after being reflected by the polygon mirror 5 can be maintained at about 90% or more of the amount of light emitted from each of the cylinder lenses 12. Not only can the output of each laser element be reduced, but also the aberration of the light reaching the image plane can be corrected uniformly because no aberration occurs due to the inclined parallel plate. As a result, the beam diameter of each laser beam can be reduced to a small value, and as a result, it is possible to cope with higher definition. The laser element 3 corresponding to Y (yellow)
Since Y is guided directly to each reflecting surface of the deflecting device 5 without being involved in any of the combining mirrors 13, not only can the output capacity of the laser be reduced,
Mirrors (13M, 13C and 13B) (possible to occur in other laser beams reflected by the combining mirror)
The error of the angle of incidence on each reflecting surface due to the reflection by the light is eliminated.

Next, the laser beam L (Y, M, C and B) reflected on each reflecting surface of the deflecting device and the post-deflection optical system 2
Of the laser beams L (Y, M, C and B) emitted from the exposure apparatus 1 to the outside through the mirror 1 and mirrors 33B and 33
The relationship with 7Y, 37M and 37C will be described.

As described above, each of the laser beams LY, LM, LC, and the laser beam reflected by the polygon mirror 5a of the deflecting device 5 and given a predetermined aberration characteristic by the first and second imaging lenses 30a and 30b. LB is the first
Are turned in a predetermined direction by the mirrors 33Y, 33M, 33C and 33B.

At this time, the laser beam LB is reflected by the first mirror 33B, and then is directly reflected by the dustproof glass 39.
B is guided to the photosensitive drum 58b. On the other hand, the remaining laser beams LY, LM, and LC are guided to the second mirrors 35Y, 35M, and 35C, respectively, and the third mirrors 37Y, 37M, and 37C are guided by the second mirrors 35Y, 35M, and 35C. , And after being reflected by the third mirrors 37Y, 37M and 37C, respectively,
By Y, 39M and 39C, an image is formed on each photosensitive drum at substantially equal intervals. In this case, the laser beam LB emitted from the first mirror 33B and the laser beam LC adjacent to the laser beam LB are also formed on the photosensitive drums 58B and 58C at substantially equal intervals.

Incidentally, the laser beam LB is applied to the polygon mirror 5.
After being deflected by each of the reflection surfaces a, the light is only reflected by the mirror 33B and emitted from the exposure device 1 toward the photosensitive drum 58.

When a plurality of mirrors are present in the optical path, the laser beam LB changes (varies) various aberration characteristics of an image on an image forming surface or bends a main scanning line according to the number of mirrors. Is useful as a reference beam when the remaining laser beams L (Y, M, and C) are relatively corrected.

When a plurality of mirrors exist in the optical path, it is preferable that the number of mirrors used for each of the laser beams LY, LM, LC, and LB is equal to an odd number or an even number. That is, as is apparent from FIG. 3, the post-deflection optical system 21 involved in the laser beam LB
The number of mirrors is 1 except for the polygon mirror 5a of the deflecting device 5.
The number of mirrors of the post-deflection optical system 21 related to the laser beams LC, LM, and LY (odd number) is respectively
There are three (odd numbers) except for the polygon mirror 5a. Here, regarding any one of the laser beams LC, LM and LY,
Assuming that the second mirror 35 is omitted, the direction of the main scanning line bending due to the inclination of the lens of the laser beam passing through the optical path (the number of mirrors is an even number) where the second mirror 35 is omitted is different. When the laser beam, that is, the number of mirrors is odd, the direction of the main scanning line bends due to the inclination or the like of the lens or the like, which is opposite to that of the main scanning line, causing a color shift which is a harmful problem when reproducing a predetermined color.

Therefore, when a predetermined color is reproduced by superimposing 2 + 2 + 2 + 2 = 8 laser beams LY, LM, LC and LB, the optical path of the polarized optical system 21 of each laser beam LY, LM, LC and LB. The number of mirrors disposed therein is substantially unified to odd or even.

FIG. 8 shows the mirror for horizontal synchronization in detail. According to FIG. 8, the horizontal synchronization mirror 25 reflects the combined laser beams LY, LM, LC and LB to the horizontal synchronization detector 23 at different timings in the main scanning direction and at the same time in the sub scanning direction. The first to fourth mirror surfaces 25Y, 25M, 2 formed at different angles in both the main scanning direction and the sub-scanning direction so that substantially the same height can be provided on the horizontal synchronization detector 23.
5C and 25B and respective mirrors 25 (Y,
Mirror block 25 for holding M, C and B) together
a.

The mirror block 25a is formed by, for example, glass-containing PC (polycarbonate). Further, each mirror 25 (Y, M, C and B) is formed by depositing a metal with high reflectivity such as aluminum at a position corresponding to the block 25a molded at a predetermined angle.

In this way, the laser beams LY, LM, LC and LB deflected by the deflecting device 5 can not only be made incident on the same detection position of one detector 23, but also, for example, In addition, it is possible to eliminate a shift of the horizontal synchronization signal due to a sensitivity or a position shift of each detector, which is a problem when a plurality of detectors are arranged. Incidentally, the laser beam groups LY, LM, LC and LB are incident on the horizontal synchronization detector 23 a total of four times per one line in the main scanning direction by the horizontal synchronization mirror 25, and Ni is emitted per one beam.
Needless to say, a horizontal synchronization signal is obtained each time (two times). The mirror block 25a is designed so that a single mirror surface of the mold can be formed from the block by cutting, and is devised so that it can be removed from the mold without the need for undercutting.

FIG. 9 is a schematic perspective view showing a mechanism for supporting the third mirrors 37Y, 37M and 37C. According to FIG. 9, the third mirror 37 (Y, M, and C) is provided at a predetermined position of the intermediate base 1a of the exposure apparatus 1 with a fixed portion 41 (Y) formed integrally with the intermediate base 1a. , M and C) and the fixed portion 41 (Y, M and C) are held by mirror pressing leaf springs 43 (Y, M and C) opposed to each other with the corresponding mirror interposed therebetween.

A pair of fixed portions 41 (Y, M and C) are formed at both ends (main scanning direction) of each mirror 37 (Y, M and C). Two protrusions 45 (Y, M, and C) for holding the mirror 37 (Y, M, and C) at two points are formed on one fixing portion 41 (Y, M, and C), respectively. . Also, the other one of the fixing portions 41
(Y, M and C) have projections 45 (Y, M and C)
A set screw 47 (Y, M and C) for movably supporting the mirror held in the vertical direction or along the optical axis is disposed.

As shown in FIG. 9, each of the mirrors 37 (Y, M, and C) has a projection 45 by moving the set screw 47 (Y, M, and C) in a predetermined direction.
Since it is moved in the direction perpendicular to the mirror surface or in the optical axis direction with (Y, M and C) as a fulcrum, the inclination in the main scanning direction, that is, the bending of the main scanning line is corrected.

FIG. 10 is a diagram for explaining the relationship between the wavelength and emission angle of the laser beam emitted by the semiconductor laser element, and the relationship between the focal length of the finite focus lens 9 and the beam stop diameter (cross-sectional beam diameter) at the image plane. It is a schematic diagram. In addition, FIG.
The description regarding the main scanning direction and the sub-scanning direction is substantially the same, and therefore, the description thereof will be omitted.

As shown in FIG. 10, the laser beam emitted from each laser element enters the finite focal lens 9 at an emission angle θ. At this time, the distance between the front principal plane of the finite focus lens 9 and the light emitting point of the laser element is S ′. On the other hand, the laser beam emitted from the rear principal plane of the finite focus lens 9 is converged at an angle α and a distance S from the image plane.

Hereinafter, assuming that the wavelength of the laser beam emitted from the laser element is λ and the focal length of the finite focus lens 9 is f, the beam stop diameter ωo on the image plane is It is expressed as

In this case, if S 'is sufficiently larger than f in equation (1), then f / (S'-f) <1, and tan ^-1 (f / (S'-f) .times.tan .theta.) ) = F / (S '
−f) × tan θ, so that ωo is almost inversely proportional to θ.

The design value of the emission angle θ (main scanning direction) of each laser element is 51 °, and the emission wavelength at the reference temperature is 680.
Although it is nm (nanometer), it differs for each laser element due to a manufacturing error or the like. The focal length f of the finite focus lens is 16.719 mm.

This also differs for each finite focus lens due to manufacturing errors and the like. Therefore, the beam diameter on the image plane varies due to variations in the wavelength of the laser beam (emission wavelength of the laser element), the emission angle, and the focal length of the finite focus lens.

Due to the variation of the beam diameter, the size of one dot of the latent image formed on the photosensitive drum changes, and as a result, the image quality deteriorates. As will be described later, it is known that if the fluctuation of the beam diameter on the image plane is within the range of the upper limit of 10% and the lower limit of −10% with respect to the design value, the deterioration of the image quality falls within the allowable range. If the variation of the wavelength of the laser beam, the variation of the emission angle, and the variation of the finite focus lens are managed so as to fall within the range, the deterioration of the image quality can be prevented.

In a multi-beam exposure apparatus using a plurality of semiconductor laser elements, a pre-deflection optical system (that is, a finite focal length lens, a half mirror, a cylinder lens, a composite mirror), a deflecting apparatus shown in FIGS. (Each reflection surface of the polygon mirror) and the fluctuation (mainly decrease) of the light intensity of the laser beam caused by each of the post-deflection optical system (that is, the doublet lens, the first to third mirrors, and the dust-proof glass). For each latent image formed on the photosensitive drum,
It is known that the image potential at the position where the developing device and the photosensitive drum face each other is different. That is, a variation (deviation) in the density of one latent image dot occurs, and as a result, the image quality deteriorates.

As will be described later, it is known that if the light intensity of the laser beam on the image plane is within the upper limit of 2% and the lower limit of −2% with respect to the design value, the deterioration of the image quality falls within the allowable range. Therefore, if the drive current of the laser drive circuit is adjusted so that the light intensity of the laser beam on the image plane falls within the above-mentioned range with respect to the design value, it is possible to prevent the image quality from deteriorating.

The reference value of the light intensity is, for example, 300 μW (micrometer) in order to achieve illuminance (brightness capable of attenuating a predetermined surface potential to a target image potential) on the outer periphery of the photosensitive drum. Watts).

Table 2 shows the results of the above-described confirmation test on the variation (deviation) of the beam stop diameter ωo on the outer peripheral surface of the photosensitive drum and the fluctuation of the light intensity of the laser beam and the effect of the image quality. For each of the beam diameter, beam intensity, and beam emission angle of the laser beam, the image when the focal length of the finite focus lens is changed is visually evaluated.

[0098]

[Table 2]

As shown in Table 2, the sectional beam diameter of the laser beam emitted from each laser element is 10% (upper limit) at the maximum and -1 at the minimum with respect to the design value on the photosensitive drum.
When the value falls within the range of 0% (lower limit), it is recognized that the deterioration of the image quality, that is, the reduction of the resolution and the fluctuation of the interval between the thin lines are within the allowable range.

FIG. 11 is a graph showing an example of the relationship (mode hopping) between the wavelength of the laser beam emitted from each laser element and the temperature at the position where the laser element is provided.
As shown in FIG. 11, every time the ambient temperature (in this case, the temperature of the case surrounding the light emitting chip of the laser element) rises by 10 ° C., the laser element becomes approximately 2 nm.
It is recognized that it becomes longer (the oscillation frequency decreases).

However, as shown in part A or part B of FIG. 11, the change in temperature and the wavelength are locally
It is non-linear, and as described above, the wavelength may fluctuate by 1 nm or more even when the temperature change is extremely small. It should be noted that the temperature at which this local wavelength variation occurs differs for each laser element and has not been specified at present.

A large change in the light emission output (light intensity) of each laser element, that is, the magnitude of the drive current changes the wavelength of the laser beam emitted from each laser element due to factors such as temperature rise (see the above-described mode). (Hopping is induced). Therefore, the design value (reference value) of the magnitude of the driving current supplied to each laser element is set to be constant, and for example, the variation in the reflectance of the half mirror of the pre-deflection optical system and the reflectivity of each mirror of the post-deflection optical system. The drive current is corrected (adjusted).

As shown in Table 2, when the wavelength of the laser beam emitted from each laser element and the focal length of each finite focus lens are not varied, the variation in the emission angle of each laser is the designed value. It can be recognized that the image quality is degraded within an allowable range when it falls within a range of 10% at a maximum and -10% at a minimum. Accordingly, when there is no variation in the wavelength of the laser beam emitted by each laser element and the focal length of each finite focus lens, the variation in the emission angle when each laser element emits a laser beam is the design value (51).
By setting the maximum value within 10% and the minimum value within -10% with respect to (°), it is possible to prevent the image quality from deteriorating due to the fluctuation of the beam diameter.

Further, as shown in Table 2, when there is no variation in the wavelength and emission angle of the laser beam emitted from each laser element, the variation in the focal length of each finite focal length lens is the design value (16. 719mm) at most 1
It is recognized that the degradation of the image quality is within an allowable range when it falls within the range of 0% and at least -10%. Therefore, if the variation in the focal length of each finite focus lens falls within the range of 10% at the maximum and -10% at the minimum with respect to the design value, it is possible to prevent the deterioration of the image quality due to the fluctuation of the beam diameter.

[0105]

As described above, the exposure apparatus of the present invention can suppress variations in the size and density of one dot of a latent image, and generate a light beam generated when an image is exposed using a plurality of light beams. Degradation of the image quality due to the deviation of the cross-sectional beam diameter and the deviation of the light intensity between each other, that is, the occurrence of a phenomenon such as a decrease in resolution and a non-uniform spacing of fine lines,
Can be prevented. Therefore, it is possible to provide a color image forming apparatus capable of providing a color image without color shift and a high-speed image forming apparatus without blurring or blurring of the outline of a line drawing.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus in which an exposure apparatus according to an embodiment of the present invention is incorporated.

FIG. 2 is a schematic plan view of an exposure device of the image forming apparatus shown in FIG.

FIG. 3 is a schematic sectional view of the exposure apparatus shown in FIG. 2 cut along a sub-scanning section including a reflection point of a deflecting device.

FIG. 4 is a schematic diagram illustrating a main part of a pre-deflection optical system in the exposure apparatus shown in FIG. 2;

5 is a schematic diagram showing intervals in the sub-scanning direction of a light beam incident on a deflection device of the exposure apparatus shown in FIG.

FIG. 6 is a schematic diagram illustrating the relationship between light beams in the sub-scanning direction in the post-deflection optical system in the exposure apparatus shown in FIG.

FIG. 7 is a schematic diagram illustrating an example of a combining mirror of the exposure apparatus shown in FIG.

8 is a schematic diagram illustrating an example of a reflection mirror for a horizontal synchronization detector of the exposure apparatus shown in FIG.

9 is a schematic diagram illustrating a mechanism for holding a mirror in the exposure apparatus shown in FIG.

10 shows the wavelength of a laser beam emitted from a semiconductor laser element incorporated in the exposure apparatus shown in FIG. 2 and the emission angle in the main scanning direction, as well as the focal length of a finite focus lens and the beam stop diameter at the image plane (cross section) FIG.

FIG. 11 is a graph showing how the emission wavelength changes when the ambient temperature changes due to mode hopping of the semiconductor laser device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exposure apparatus, 3 ... Light source, 5 ... Deflection apparatus, 7 ... Pre-deflection optical system, 9 ... Finite focus lens, 10 ... Stop, 11 ... Cylinder lens, 12: half mirror, 13: composite mirror, 21: post-deflection optical system, 23: beam position detector (light detector for horizontal synchronization), 25: mirror for horizontal synchronization detection, 30a 1st imaging lens 30b 2nd imaging lens 33 ... 1st mirror, 35 ... 2nd mirror, 37 ... 3rd mirror, 39 ... Dustproof glass 40 Parallelism adjusting mechanism 100 Image forming apparatus.

Claims (8)

[Claims] A plurality of light sources; pre-deflection optical means for giving predetermined characteristics to light from the plurality of light sources; deflection means for deflecting light from the pre-deflection optical means in a first direction; A lens that forms an image of light deflected by the deflecting means at a predetermined image plane at a constant speed, and wherein the deviation of light intensity variation on the image plane of light emitted by each of the plurality of light sources is determined. An exposure apparatus having a predetermined range. A plurality of light sources; a pre-deflection optical means for giving predetermined characteristics to light from the plurality of light sources; a deflection means for deflecting light from the pre-deflection optical means in a first direction; A lens for imaging the light deflected by the deflecting means at a predetermined speed on a predetermined image plane, wherein the deviation of the variation of the divergence angle of the light emitted by each of the plurality of light sources is within a predetermined range. An exposure apparatus characterized in that: A plurality of light sources; a pre-deflection optical means for giving predetermined characteristics to light from the plurality of light sources; a deflection means for deflecting light from the pre-deflection optical means in a first direction; A lens that forms an image of light deflected by the deflecting unit at a constant speed on a predetermined image plane, wherein the focal length of a lens provided for each of the plurality of light sources of the pre-deflection optical unit is An exposure apparatus, wherein a deviation of the fluctuation is within a predetermined range. 4. A plurality of light sources; pre-deflection optical means for giving predetermined characteristics to light from the plurality of light sources; deflection means for deflecting light from the pre-deflection optical means in a first direction; A lens that forms an image of light deflected by the deflecting unit at a constant speed on a predetermined image plane; and an exposure apparatus having: a deviation of light intensity variation in an image plane of light emitted by each of the plurality of light sources. An exposure apparatus having an upper limit of 2% and a lower limit of -2%. 5. A plurality of light sources, pre-deflection optical means for giving predetermined characteristics to light from the plurality of light sources, deflection means for deflecting light from the pre-deflection optical means in a first direction, A lens for imaging the light deflected by the deflecting means on a predetermined image plane at a constant speed, wherein the upper limit of the deviation of the variation of the divergence angle of the light emitted by each of the plurality of light sources is 10 %, And the lower limit value is -10%. 6. A plurality of light sources, pre-deflection optical means for imparting predetermined characteristics to light from the plurality of light sources, deflection means for deflecting light from the pre-deflection optical means in a first direction, A lens that forms an image of light deflected by the deflecting unit at a constant speed on a predetermined image plane, wherein the focal length of a lens provided for each of the plurality of light sources of the pre-deflection optical unit is An exposure apparatus, wherein the upper limit of the variation deviation is set to 10% and the lower limit is set to -10%. 7. A plurality of light sources, pre-deflection optical means for imparting predetermined characteristics to light from the plurality of light sources, deflecting means for deflecting light from the pre-deflection optical means in a first direction, A lens for forming an image of light deflected by the deflecting means on a predetermined image plane at a constant speed, and wherein the deviation of the beam diameter variation at the image plane position of the light emitted by each of the plurality of light sources is determined. An exposure apparatus having a predetermined range. 8. A plurality of light sources, pre-deflection optical means for imparting predetermined characteristics to light from the plurality of light sources, deflecting means for deflecting light from the pre-deflection optical means in a first direction, A lens that forms an image of light deflected by the deflecting means on a predetermined image plane at a constant speed, and an exposure apparatus having: a deviation of a variation in beam diameter at an image plane position of light emitted by each of the plurality of light sources. An exposure apparatus having an upper limit of 10% and a lower limit of -10%.