JP2001201705A - Multi-beam exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner enabling to provide a color image without color slippage at a low cast. SOLUTION: In the optical scanner 1, Mj pieces of beam groups each consisting of Ni pieces of beams are made incident on each reflective surface of a light deflector 5 so that the spacing between the beam groups may increase monotonically from one end, and the beam group of one end with the smallest spacing between beam groups is made incident so as to intersect a beam deflected by a light deflector. Thereby, in image-formation characteristics of the beam of M group, that is, differences in the variation of the spherical aberration or the beam diameter, and the difference in the curvature of the scanning line between beam groups are reduced. Therefore, the degradation of an image quality can be prevented. In addition, the size of the optical scanner is also reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam optical scanning apparatus used in an image forming apparatus such as a high-speed laser printer, a multi-drum type color copier or a digital color copier.

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as a multi-drum type color printer or a multi-drum type color copying machine, a plurality of image forming units corresponding to color components separated by color, and A laser exposure apparatus, that is, an optical scanning apparatus that provides image data corresponding to components, that is, a plurality of laser beams, is used.

The optical scanning device includes a first lens group for narrowing a cross-sectional beam diameter of a laser beam emitted from a semiconductor laser element to a predetermined size, and a recording medium conveying the laser beam narrowed by the first lens group. And a second lens group that forms a laser beam deflected by the optical deflecting device at a predetermined position on the recording medium. In many cases, the direction in which the laser beam is deflected by the optical deflecting device is referred to as the main scanning direction, and the direction in which the recording medium is conveyed, that is, the direction orthogonal to the main scanning direction is referred to as the sub-scanning direction.

As this type of optical scanning device, there are provided an example in which a plurality of optical scanning devices are arranged corresponding to each image forming section, and a plurality of laser beams, in accordance with an image forming apparatus to which the present invention is applied. There is known an example in which a multi-beam optical scanning device formed so as to be arranged is arranged.

By the way, for a recording medium, for example,
If image information can be recorded by N laser beams, the number of rotations of the rotating mirror and the image frequency are each reduced to 1 / N.

A compact optical scanning device for an image forming apparatus capable of forming a color image is provided by arranging M groups of light sources including N laser beams in accordance with the number of color components separated by color. Provided.

[0007]

However, in order to guide the M group of laser beams to the optical deflecting device in a state where the laser beams can be regarded as substantially one laser beam, the light source side of the light deflecting device must be closer to the light source than the optical deflecting device. It becomes necessary to combine the M groups of laser beams. In this case, the distance between the light deflecting device and the light source is sufficiently ensured, or the laser beam incident on the reflecting surface of the light deflecting device is placed in a direction perpendicular to the direction in which the reflecting surface is rotated, that is, in the sub-scanning direction. Need to be incident.

[0008] In order to secure the distance between the light source and the light deflecting device, the distance between the light deflecting device and the light source is increased. Therefore, there is a problem that the size of the optical scanning device is increased. on the other hand,
Providing an interval in the sub-scanning direction with respect to the laser beam incident on the reflecting surface may degrade the imaging characteristics, a difference in the amount of bending in the scanning direction for each of the M groups of laser beams, and each of the M groups of laser beams. However, there is a problem that the variation in the cross-sectional beam diameter on the image plane due to the change in the refractive index of the lens material caused by the environmental change increases.

When the distance between the final lens surface and the image surface is increased for the purpose of reducing the size of the optical scanning device, the difference in the amount of bending in the scanning direction for each of the M groups of laser beams. There is a problem of growing. In this case, the amount of bending can be reduced by increasing the distance between the reflecting surface of the light deflecting device and the final lens surface, but there is a problem that the optical scanning device becomes large. Also, if the distance between the reflecting surface and the final lens surface is increased, the effective swing angle becomes smaller,
The driving frequency for driving the laser element of each light source, that is, the image frequency must be increased, and there is a problem that the cost is increased in terms of measures against noise and frequency characteristics of the driving device.

Further, the position where each laser beam passes through each lens of the optical scanning device is optimized in order to equalize the optical characteristics given to each of the M groups of laser beams spaced apart in the sub-scanning direction. In this case, there is a problem that a laser beam passing through a position distant from the optical axis of the system of the optical scanning device in the sub-scanning direction has different coma aberration as compared with the remaining laser beams.

Further, each of the M groups of laser beams is N
When a plurality of laser beams are included, half mirrors, which are a plurality of semi-transparent mirrors, are used to combine the N laser beams so that the N laser beams can be regarded as substantially one laser beam. If the difference in the number of passes through the half mirror is large, there is a problem that a difference in the light amount between the laser beams, a difference in spherical aberration or coma aberration, and a difference in beam diameter occurs.

Further, when the laser beams of the M group include N laser beams, the laser beams of each group include N laser beams.
Given the width in the sub-scanning direction for the number of beams,
There is a problem that the inclination in the main scanning direction between the exposure start position and the exposure end position of the laser beam scanned by one scan is increased to a level that can be viewed.

Further, since the M group laser beams include N laser beams, the phase difference between the laser beams or the phase difference between the laser beams at the time when all the light intensities of the laser beams reaching the image plane are combined. There is a problem that the light energy on the image plane fluctuates due to the fluctuation of the wavelength. In addition, when the fluctuation of the light energy due to the fluctuation of the phase difference or the wavelength exceeds a predetermined magnitude, when incorporated in the image forming apparatus, an image defect or a defect of toner supply to an unexposed portion occurs. There's a problem.

An object of the present invention is to provide an optical scanning device capable of forming a color image with less color shift.

[0015]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned problems, and has a structure of ΔN _i (N ₁ + N ₂ +...)
+ N _M ) (M is an integer of 2 or more, and N _i is each an integer of 1 or more), and a plurality of light sources that convert the light emitted from the ΣN _i light sources into convergent light or parallel light. And the light converted into convergent light or parallel light by one of the plurality of finite focus lenses and the collimator lenses is positive only in the sub-scanning direction to further converge in the sub-scanning direction. M optical members to which the power of (i) is given, and (M−1) reflecting mirrors for combining that reflect M beams from the M optical members so as to substantially overlap in the first direction. a first optical means includes a rotatable formed reflecting surface, and a deflecting means for deflecting the light in a predetermined direction, a constant velocity the Shigumanyu _i of beams deflected by the deflecting means on a predetermined image surface Image as if scanning with And a second optical unit including a lens having a function of correcting a surface tilt of the deflecting unit, wherein the M beam groups are arranged on the reflecting surface of the deflecting unit, and the distance between the beam groups from one end is monotonic. And a beam group at one end where the interval between the beam groups is the smallest is incident so as to intersect with the beam deflected by the deflecting device. It is.

Further, the present invention provides a method of calculating ΔN _i (N ₁ + N ₂ +
··· + N _{M) (M} is an integer of 2 or more, and the integer of 1 or more) of light sources each of N _i, the light emitted from the .SIGMA.N _i pieces of the respective light sources to convergent light or collimated light Any of a plurality of finite focus lenses and collimator lenses to be converted, and light converted into convergent light or parallel light by any of the plurality of finite focus lenses and collimator lenses, in the sub-scanning direction to further converge in the sub-scanning direction. M optical members with positive power applied only to
(M-1) combining reflecting mirrors for reflecting the M beam groups from the set of optical members so as to substantially overlap in the first direction;
A deflecting means having a rotatable reflecting surface for deflecting light in a predetermined direction, and ΣΝ _i beams deflected by the deflecting means on a predetermined image plane. A second optical unit including a lens that forms an image so as to scan at a constant speed and has a function of correcting a surface tilt of the deflecting unit; and M beam groups on M image carriers. the optical scanning unit that irradiates the distance between the scanning line of the optical axis and the end of the system of the second optical means L _1, the optical axis and the other of the system of the second optical means L _m , And ΔL _max is the distance in the direction parallel to the optical axis of the system between the scanning lines at both ends, the distance Lo between the final lens surface and the image surface
Is (ΔL _max + L _m + L ₁ ) / l. 8> Lo Lo> (ΔL _max + L _m + L ₁ ) / 2. An optical scanning device is provided.

Further, the present invention relates to a method of forming a ΣNi (N1 + N2
+ ... + NM) (M is an integer of 1 or more, and Ni is an integer of 1 or more, and at least one of M or Ni is an integer of 2 or more) and the ΣNi light sources Any one of a plurality of finite focus lenses and collimator lenses that convert light emitted from to a convergent light or a parallel light, and light converted to convergent light or parallel light by any of the plurality of finite focus lenses and a collimator lens, M sets of optical members to which positive power is given only in the sub-scanning direction to further converge in the sub-scanning direction;
(M-1) combining reflecting mirrors for reflecting the M beam groups from the set of optical members so as to substantially overlap in the first direction;
A deflecting means having a reflecting surface rotatably formed and deflecting light in a predetermined direction, and ΣΝi beams deflected by the deflecting means on a predetermined image plane. Second optical means including a lens having a function of forming an image so as to scan at a high speed and correcting the surface tilt of the deflecting means, and Lt between the reflection point on the deflecting means and the image plane. distance,
And W is an effective image area width including an area for detecting a horizontal synchronization signal, wherein the effective field angle φ of the beam deflected by the deflecting means satisfies φ> W / Lt. An apparatus is provided.

Still further, the present invention provides a method using ΔN _i (N ₁ +
N ₂ + ... + N _M ) (M is an integer of 2 or more and N _i
Each of which is an integer of 1 or more), any one of a plurality of finite focus lenses and collimator lenses that convert light emitted from each of the ΣN _i light sources into convergent light or parallel light, M sets of optical members provided with a positive power only in the sub-scanning direction to further converge the light converted into convergent light or parallel light by one of the focusing lens and the collimator lens in the sub-scanning direction; A first optical unit including: M-1 combining reflecting mirrors for reflecting the M beams from the optical member so as to substantially overlap in the first direction; and a rotatable reflecting surface. Deflecting means for deflecting light in a predetermined direction,
A second optical unit including a lens having a function of forming an image of the _{ｉ i} beams deflected by the deflecting unit so as to scan at a constant speed on a predetermined image plane and correcting a surface tilt of the deflecting unit; Having a positive power only in the sub-scanning direction, the incident angle and the position of the beam to the M sets of optical members,
An optical scanning device is characterized in that the light passes through the optical member eccentrically with respect to the optical axis of the optical member.

Still further, the present invention provides a method using ΔN _i (N ₁ +
N _i + ... + N _M ) (M is an integer of 1 or more and N _i
Is an integer of 1 or more and at least one of N _i is an integer of 3 or more), and a plurality of finite focus lenses that convert light emitted from each of the ΣN _i light sources into convergent light or parallel light; and either a collimator lens, the light converted into convergent light or collimated light by any of the plurality of finite focal lenses and the collimator lens, reflected or not transmit so as to substantially overlap the N _i number of beams in a first direction, respectively Into M beam groups by (N _i −
1) A number of translucent mirrors, M sets of optical members provided with positive power only in the sub-scanning direction to further converge the M groups of beams in the sub-scanning direction, and M sets of optical members A first optical unit including: M-1 synthesis reflecting mirrors for reflecting the M light beam groups so as to substantially overlap in the first direction; and a rotatable reflecting surface; and deflecting means for deflecting the light in a predetermined direction, imaged to scan the Shigumanyu _i of beams deflected by the deflecting means at a constant speed in a predetermined image surface, to correct the tilt of the deflecting means functions And a second optical means including a lens having the following: and wherein the number of times that each beam passes through the M-1 translucent mirrors is 1 or 0 times. It is.

Still further, the present invention provides a method using ΔN _i (N ₁ +
N ₂ + ... + N _M ) (M is an integer of 1 or more and N _i
At least one is an integer of 2 or more);
_Any one of a plurality of finite focus lenses and collimator lenses for converting light emitted from each of the _i light sources into convergent light or parallel light, and convergent light or parallel light depending on any of the plurality of finite focus lenses and collimator lenses In order to further converge the converted light in the sub-scanning direction, M sets of optical members to which positive power is given only in the sub-scanning direction, and M beam groups from the M sets of optical members,
A first optical means including (M-1) reflecting mirrors for combination that reflect the light so as to be substantially overlapped in a direction, and a deflection surface that is rotatably formed and deflects light in a predetermined direction. means and the beam of Shigumanyu _i present deflected by the deflecting means is imaged to scan at a constant speed in a predetermined image plane, a second optical including a lens having a function of correcting the surface tilt of the deflecting means Means, wherein p is a scanning pitch in the sub-scanning direction, and
When k is the number of rotating polygon mirrors, the scanning line is δ = tan ⁻¹ (N _i × p × k × φ / (4 × π × W)) from the direction perpendicular to the traveling direction of the image carrier. An optical scanning device characterized by being tilted is provided.

Furthermore, the present invention provides a method for generating ΔN _i (N ₁ +
N ₂ + ... + N _M ) (M is an integer of 1 or more and N _i
At least one is an integer of 2 or more);
_Any one of a plurality of finite focus lenses and collimator lenses for converting light emitted from each of the _i light sources into convergent light or parallel light, and convergent light or parallel light depending on any of the plurality of finite focus lenses and collimator lenses In order to further converge the converted light in the sub-scanning direction, M sets of optical members to which positive power is given only in the sub-scanning direction, and M beam groups from the M sets of optical members,
A first optical means including (M-1) reflecting mirrors for combination that reflect the light so as to be substantially overlapped in a direction, and a deflection surface that is rotatably formed and deflects light in a predetermined direction. means and the beam of Shigumanyu _i present deflected by the deflecting means is imaged to scan at a constant speed in a predetermined image plane, a second optical including a lens having a function of correcting the surface tilt of the deflecting means And p is a beam pitch in the sub-scanning direction, β
A beam in the main scanning direction of the e ^-2 diameter / p, the sub-scanning direction of the e ^-2 diameter / p of the α-beam, half decay exposure / average exposure energy of ζ photoreceptor, and, eta and meet two neighboring When the relative intensity with respect to the peak intensity of one beam at the midpoint of the line connecting the centers of the beams,

(Equation 2)

An object of the present invention is to provide an optical scanning device characterized by satisfying the following.

Still further, the present invention provides a method using ΔN _i (N ₁ +
N ₂ + ... + N _M ) (M is an integer of 1 or more and N _i
At least one is an integer of 2 or more);
_Any one of a plurality of finite focus lenses and collimator lenses for converting light emitted from each of the _i light sources into convergent light or parallel light, and convergent light or parallel light depending on any of the plurality of finite focus lenses and collimator lenses In order to further converge the converted light in the sub-scanning direction, M sets of optical members to which positive power is given only in the sub-scanning direction, and M beam groups from the M sets of optical members,
A first optical means including (M-1) reflecting mirrors for combination that reflect the light so as to be substantially overlapped in a direction, and a deflection surface that is rotatably formed and deflects light in a predetermined direction. means and the beam of Shigumanyu _i present deflected by the deflecting means is imaged to scan at a constant speed in a predetermined image plane, a second optical including a lens having a function of correcting the surface tilt of the deflecting means Means, wherein the M sets of optical members to which positive power is given only in the sub-scanning direction are a single-sided cylinder lens made of a glass material and a double-sided cylinder substantially equivalent to the material of the post-deflection optical system lens. An optical scanning device comprising a lens is provided.

Still further, the present invention provides a method for producing ΔNi (N1 +
N2 + ... + NM) (M is an integer of 1 or more and Ni
At least one is an integer of 3 or more);
Any one of a plurality of finite focus lenses and collimator lenses for converting light emitted from each of the i light sources into convergent light or parallel light, and convergent light or parallel light depending on any of the plurality of finite focus lenses and collimator lenses The converted light is reflected or transmitted so that each of the Ni beams substantially overlaps in the first direction, and is combined into M beam groups. (Ni-1) semi-transparent mirrors and the M group In order to further converge the beam in the sub-scanning direction, M sets of optical members to which positive power is given only in the sub-scanning direction, and M beams from the M sets of optical members are substantially moved in the first direction. A first optical unit including M-1 reflecting mirrors for combining so as to overlap each other, a deflecting unit having a rotatable reflecting surface, and deflecting light in a predetermined direction; By deflection means A second optical unit including a lens having a function of forming an image of the deflected ΣΝi beams so as to scan at a constant speed on a predetermined image plane and correcting a surface tilt of the deflecting unit. It is an object of the present invention to provide an optical scanning device, wherein the outputs of the Ni light sources in the group are substantially equal.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a front sectional view of a four-drum color image forming apparatus in which a multi-color optical scanning device to which the embodiment of the present invention is applied is incorporated.

As shown in FIG. 1, the 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, 50M, each forming an image for magenta, C = cyan and B = black
It has 50C and 50B.

Each image forming section 50 (Y, M, C and B)
Are the third folding mirrors 37Y and 37Y of the optical scanning device 1.
50Y below the optical scanning device 1 corresponding to the position where the laser beams L (Y, M, C and B) corresponding to the respective color component images are emitted via the M and 37C and the first folding mirror 33B. , 50M, 50C and 50B in this order.

Below each image forming section 50 (Y, M, C, and B), a transport belt 5 for transporting an image formed by each image forming section 50 (Y, M, C, and B) is provided.
2 are arranged.

The transport belt 52 is wound around a belt driving roller 56 and a tension roller 54 which are rotated in the directions indicated by arrows by a motor (not shown), and is rotated at a predetermined speed in a 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, each of which is formed in a cylindrical drum shape and rotatable in the direction of an arrow, and on which an electrostatic latent image corresponding to image information to be printed is formed. .

Each photosensitive drum 58 (Y, M, C)
And B) are located at predetermined positions around each photosensitive drum 58.
The charging devices 60Y, 60M, 60C and 60B for providing a predetermined surface potential to the surface of (Y, M, C and B), and the static electricity formed on the surface of each photosensitive drum 58 (Y, M, C and B) Developing devices 62Y, 62M, 62C and 62 for developing the electrostatic latent image with toner having a corresponding color
B, with the conveyor belt 52 interposed between the photosensitive drums 58 (Y, M, C and B);
(Y, M, C, and B), and the conveyance belt 52 or the recording paper P conveyed via the conveyance belt 52,
Transfer devices 64Y, 64M, 64C and 6 for transferring toner images on the respective photosensitive drums 58 (Y, M, C and B)
4B, after the toner image is transferred via the transfer device 64 (Y, M, C and B), the photosensitive drum 58 (Y, M, C)
C and B) The cleaners 66Y, 66M, 66C and 66B for removing the residual toner remaining on the surface, and the respective photosensitive members after the toner image is transferred via the transfer device 64 (Y, M, C and B). Body drum 58 (Y, M, C
And B) a static eliminator 68 for removing the residual potential remaining on the
Y, 68M, 68C and 68B are the respective photosensitive drums 5
8 (Y, M, C and B) in order.

The mirrors 37Y and 37Y of the optical scanning device 1
The laser beams LY, LM, LC and LB guided to the photosensitive drum 58 by 7M, 37C and 33B
As will be described later with reference to FIGS. 2 and 6, each of the photosensitive members is separated into Ni pieces in the sub-scanning direction, and each of the charging devices 60 (Y, M, C, and B) and each of the developing devices 62 (Y ,
M, C and B). In this example, two laser beams LY, LM, and LC (N1 =
N2 = N3 = 2) and four laser beams LB
(N4 = 4).

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

At one end of the paper cassette 70 and near the tension roller 54, a half-moon roller (delivery roller) 72 for taking out the paper P stored in the paper cassette 70 one by one (from the top) is arranged. Have been. Between the delivery roller 72 and the tension roller 54,
The leading end of one sheet P taken out of the cassette 70 and each image forming section 50 (Y, M, C and B), especially 50B
Accordingly, a registration roller 74 for aligning each photosensitive drum 58 (Y, M, C, and B), particularly, the tip of the toner image formed on 58B is disposed.

The registration roller 74 and the first image forming unit 5
0Y, in the vicinity of the tension roller 54, substantially with the tension roller 54
A suction roller 76 that provides a predetermined electrostatic attraction force to one sheet of paper P conveyed at a predetermined timing via a registration roller 72 is disposed on the outer periphery of the sheet. The axis of the suction roller 76 and the tension roller 54 are arranged in parallel.

At one end of the transport belt 52, near the belt drive roller 56, substantially on the outer periphery of the belt drive roller 56 with the transport belt 52 interposed, the transport belt 52
Alternatively, registration sensors 78 and 80 for detecting the position of an image formed on the sheet P conveyed by the conveyance belt are arranged at a predetermined distance in the axial direction of the belt driving roller 56 (FIG. 1). Is a front sectional view, so only the rear sensor 80 is shown.)

On the conveyor belt 52 corresponding to the outer periphery of the belt drive roller 56, a conveyor belt cleaner 82 for removing toner adhered on the conveyor belt 52 or paper chips of the paper P is arranged.

The sheet P conveyed via the conveyor belt 52
A fixing device 84 that fixes the toner image transferred to the sheet P to the sheet P is disposed in a direction in which the toner image is separated from the tension roller 56 and further conveyed.

FIG. 2 shows a multi-beam optical scanning device used in the color image forming apparatus shown in FIG. In the color image forming apparatus shown in FIG. 1, four types of image data, which are color-separated for each of Y, yellow, M, magenta, C, cyan and B, black (black) color components, are usually used. , M, C
Since four sets of various devices for forming an image for each color component corresponding to each of the color components B and B are used, similarly, by adding Y, M, C, and B to each reference code, Image data for each device and the corresponding device are identified.

As shown in FIG. 2, the multi-beam optical scanning device 1 converts a laser beam emitted from a laser element as a light source into an image plane arranged at a predetermined position, that is, a first to a first plane shown in FIG. Fourth image forming units 50Y, 50
M, 50C and 50B photosensitive drums 58Y and 58
It has only one light deflecting device 5 as deflecting means for deflecting at a predetermined linear velocity toward respective predetermined positions of M, 58C and 58B. Hereinafter, the direction in which the laser beam is deflected by the light deflector 5 is referred to as a main scanning direction. Further, a direction orthogonal to the main scanning direction and parallel to each reflecting surface of the polygon mirror 5a of the light deflector 5 is referred to as a sub-scanning direction.

The light deflecting device 5 includes a polygonal mirror main body 5a having a plurality of, for example, eight plane reflecting mirrors (surfaces) arranged in a regular polygonal shape, and a polygonal mirror main body 5a at a predetermined speed in the main scanning direction. And a motor (not shown) for rotating. The polygon mirror body 5a is formed of, for example, aluminum.
Further, each reflecting surface of the polygon mirror 5a is a surface including a direction in which the polygon mirror body 5a is rotated, that is, a surface orthogonal to the main scanning direction,
That is, after being cut out along the sub-scanning direction, the surface is provided by depositing a surface protective layer such as silicon dioxide on the cut surface.

The first and second imaging lenses 30a for providing predetermined optical characteristics to the laser beam deflected in a predetermined direction by the reflection surface of the light deflection device 5 are provided between the light deflection device 5 and the image plane. And 30b, the combined laser beam L (Y, Y, which is emitted from the second imaging lens 30b of the post-deflection optical system 30 and the post-deflection optical system 30.
M, C and B) only one horizontal synchronization detector 23 for detecting that the individual beams have reached a predetermined position before the area where the image is to be written; 2 + 2 + 2 + 4 combined laser beams L disposed between the synchronous detector 23 and passed through at least one lens of the optical system 21 after deflection, which will be described later.
(Y, M, C, and B) are converted to a horizontal synchronization detector 23.
, A single set of horizontal synchronization folding mirrors 25 and the like that reflect light in different directions in both the main scanning direction and the sub-scanning direction are arranged.

Next, the pre-deflection optical system between the laser element as the light source and the light deflector 5 will be described in detail.

The optical scanning device 1 has a first and a second two (N ₁ = N ₂ = N ₃ = 2) satisfying N _i (i is a positive integer).
And light sources 3Y, 3M, and 3C for yellow, magenta, and cyan including the first to fourth (N ₄ = 4) laser elements satisfying N _i (i is a positive integer). 4 light sources 3B. The number M of beam group light sources (M is a positive integer) is indicated by 4.

The first light source 3Y has a yellow first laser 3Ya and a yellow second laser 3Yb for emitting a laser beam corresponding to Y, that is, a yellow image. The respective lasers 3Ya and 3Yb are arranged on the respective reflecting surfaces of the polygon mirror 5a of the optical deflecting device 5 so as to provide a predetermined distance in the sub-scanning direction to the laser beams LYa and LYb emitted therefrom. .

The second light source 3M has a magenta first laser 3Ma and a magenta second laser 3Mb for emitting a laser beam corresponding to M, that is, a magenta image. The respective lasers 3Ma and 3Mb are also arranged on the respective reflecting surfaces of the polygon mirror 5a of the optical deflecting device 5 so as to provide the laser beams LMa and LMb emitted therefrom with a predetermined distance in the sub-scanning direction. ing.

The third light source 3C is a cyan first laser 3 for emitting a laser beam corresponding to C, that is, a cyan image.
It has a Ca and cyan second laser 3Cb. This light source 3C is also arranged on each reflecting surface of the polygon mirror 5a of the light deflecting device 5 so as to be able to provide a predetermined distance in the sub-scanning direction to the laser beams LCa and LCb emitted therefrom.

The fourth light source 3B is B, ie, black.
(Black) Black first laser 3Ba, black second laser 3Bb, and black third laser 3Bc for emitting a laser beam corresponding to an image
And a fourth black laser 3Bd. The light source 3
B denotes a laser beam emitted from each of the polygonal mirrors 5a of the light deflector 5 on the respective reflecting surfaces, similarly to the above-described first to third light sources 3Y, 3M and 3C, including four lasers. LBa, LYb, LYc and LYd
Are arranged so as to provide a predetermined distance in the sub-scanning direction.

Thus, on each reflecting surface of the polygon mirror 5a of the light deflecting device 5, Ni and M sets (M = 4) of laser beams LYa, LY spaced apart in the sub-scanning direction on each reflecting surface are provided.
b, LMa, LMb, LCa, LCb, LBa, LB
b, LBc and LBd are emitted.

Each of the laser elements 3Ya and 3Y
b, 3Ma and 3Mb, 3Ca and 3Cb, and 3Ba, 3Bb, 3Bc and 3Bd, that is, between the four groups of light sources 3Y, 3M, 3C and 3B and the light deflecting device 5, 2 Book +2 book +2
+4 laser beams LYa, LYb,
LMa, LMb, LCa, LCb, LBa, LBb, L
4 (M) sets of pre-deflection optical systems 7 (Y, M, C) for adjusting the cross-sectional beam spot shapes of Bc and LBd to a predetermined shape
And B) are arranged.

Between each of the first yellow laser 3Ya and second yellow laser 3Yb and the light deflecting device 5, a finite focal lens 9Ya for giving a predetermined convergence to the lasers 3Ya and 3Yb and a corresponding finite lens are passed. An aperture 10Ya for adjusting the beam cross-sectional shape of the obtained laser beam into a predetermined shape, and the lenses 9Yb and 10Yb are arranged. In addition, each finite lens 9Y
a and 9Yb need to have optical characteristics complementary to the optical characteristics given to the imaging lens group used in the post-deflection optical system described later, and depend on the optical characteristics of the imaging lens group. Thus, for example, a collimating lens that converts each laser beam into parallel light may be used.

At the position where the laser beams LYa and LYb passing through the respective apertures 10Ya and 10Yb intersect, each laser beam LYb and LYa is substantially one laser when viewed from the sub-scanning direction. Beam LY
A half mirror 12 </ b> Y, which is a translucent mirror to be superimposed, is disposed. That is, on the surface of the half mirror 12Y opposite to the surface on which the laser beam LYa is incident, the laser beam LYb arranged so as to provide a predetermined beam interval in the sub-scanning direction with respect to the laser beam LYa is applied to the laser beam LYa. On the other hand, it is incident at a predetermined beam interval in the sub-scanning direction. The half mirror 12
Y is substantially one laser beam LY when each of the laser beams LYa and LYb is viewed from the sub-scanning direction.
The light deflecting device 5 is disposed at a predetermined angle that allows the light to be incident on the polygon mirror 5a in a superimposed state.

A hybrid cylinder lens 11Y for further converging the laser beam LY superimposed by the half mirror 12Y only in the sub-scanning direction between the half mirror 12Y and the light deflecting device 5, and FIG. As will be described later, a laser combining mirror unit 13 having a plurality of reflecting surfaces for guiding the laser beam LY passed through the hybrid cylinder lens 11Y to the light deflecting device 5 as a substantially unitary light beam is disposed. ing.

The laser combining mirror unit 13 guides the following other laser beams to the light deflecting device 5 substantially as a bundle of light beams. As apparent from FIG. 2, the first and second yellow laser beams 3Ya and 3Yb emitted from the first light source 3Y pass through the laser combining mirror unit 13 shown in FIG. Will be guided to.

Further, between each of the first and second magenta lasers 3Ma and 3Mb and the laser synthesizing mirror unit 13, a finite focal lens 9Ma and an aperture 10Ma and a 9Mb corresponding to the lasers 3Ma and 3Mb are provided. 10Mb, a half mirror 12M, and a hybrid cylinder lens 11M are arranged.

Hereinafter, similarly, the respective lasers 3Ca and 3Cb are provided between the cyan first laser 3Ca and the cyan second laser 3Cb and the laser combining mirror unit 13, respectively.
Focus lens 9Ca and apertures 10Ca and 9Cb and 10Cb corresponding to 3Cb and 3Cb, half mirror 12C, and hybrid cylinder lens 11C
Is arranged.

Further, the first black laser 3Ba, the second black laser 3Bb, the third black laser 3Bc, and the fourth black laser 3B
d, and the first to fourth finite focus lenses 9Ba, 9Bb, and 9B, which can provide optical characteristics similar to those of the other light sources described above between the laser combining mirror unit 13 and each of the laser beams.
9Bc and 9Bd, first to fourth diaphragms 10Ba,
10Bb, 10Bc and 10Bd, half mirror 12
B ₁ , 12B ₂ and 12B ₃ , and a hybrid cylinder lens 11B are arranged.

The light sources 3 (Y, M, C, and B), the pre-deflection optical system 7 (Y, M, C, and B), and the laser combining mirror unit 13 are made of, for example, an aluminum alloy. Are integrally held by a holding member (not shown).

Next, the optical characteristics of each lens and half mirror used in the pre-deflection optical system will be described in detail.

Finite focus lens 9 (Y, M, C and B)
a, 9 (Y, M, C and B) b, 9Bc and 9Bd
In this method, a single lens is used in which an ultraviolet-curable plastic aspheric lens (not shown) is attached to the surface of an aspherical or spherical glass lens.

The half mirrors 12 (Y, M and C) and the half mirrors 12B are used in order to make the outputs of the laser elements in each beam group all the same and have the same light intensity on the surface.
The ratio of reflectance and transmittance of _1, respectively, is set to 1: 1. On the other hand, the half mirrors 12B ₂ and 12B
The ratio of reflectance and transmittance of the B _3, respectively, 2: 1 and 3: is set to 1.

More specifically, the first to third light sources 3Y and 3Y
In each of M and 3C, the number N of lasers is Ν ₁ = Ν
_{Since 2} = Ν ₃ = 2, the total number of required half mirrors 12 (Y, M and C) is governed by N _i -1 and is substantially the same as that of the laser beam from the two light sources. It is necessary to combine the light amounts by 50%. Therefore, the ratio between the reflectance and the transmittance is set to 1: 1. When the lasers 3Ya and 3Yb, 3Ma and 3Mb, and 3Ca are passed through the half mirror 12 (Y, M and C), respectively. And LYa, LYb, LMa, LMb, LC emitted from 3Cb
The light intensities of a and LCb are defined substantially equal.

On the other hand, a laser beam LBa from the black first laser 3Ba and a laser beam LBa from the black second laser 3Bb
Half mirror 12B ₁ for synthesizing Bb also the light amount of the laser beam from the two light sources in terms of synthesis by 50%, with a half-mirror 12 and (Y, M and C) with the same reflectance and transmittance. On the other hand, the half mirror 12B
_2, since it is intended to synthesize a laser beam LBc from the black third laser 3Bc the laser beam LBa and the laser beam LBb, which has already been synthesized by the half mirror 12B _1, the ratio of the reflectance and transmittance 2 : 1, the light intensity of the laser beams LBa, LBb and LBc can be made equal. Similarly, half mirror 1
2B _3, since against the laser beam LBc and laser beams LBa and the laser beam LBb, which has already been synthesized by the half mirror 12B ₂ is to synthesize the laser beam LBd from the black fourth laser 3Bd, transmittance and reflectance By setting the ratio to the ratio to 3: 1, the half mirror 1
At the point of time when the laser beams 3Ba and 2B ₃ have passed,
The light intensities of the laser beams LBa, LBb, LBc and LBd emitted from 3Bb, 3Bc and 3Bd can be made substantially equal.

By the way, the light intensity of each of the laser beams LBa, LBb, LBc and LBb incident on the hybrid lens 11B is equal to the respective lasers 3Ba, 3Bb,
Compared to the time when 3Bc and a3Bd are emitted, it is reduced to about 25%.

On the other hand, the half mirror 12 (Y, M
And C) and passed through the hybrid lens 11 (Y,
M and C) each laser beam LYa, LY
b, LMa, LMb, LCa and the light intensity of LCb are
The respective lasers 3Ya, 3Yb, 3Ma, 3Mb, 3
Ca and 3Cb are kept at about 50% as compared with the time when they are emitted.

From this, in the example shown in FIG. 2, each of the lasers 3Ya, 3Yb, 3Ma, 3Mb, 3Ca and 3Ca
The rated output of Cb is 10 milliwatts (hereinafter referred to as mW)
Rated output 2 of 3Ba, 3Bb, 3Bc and 3Bd
By setting them to 0 mW, laser beams for different numbers of beams and different colors can be set to have substantially the same light intensity at the imaging position.

Incidentally, individual errors in the characteristics of the toner used in each developing device 62 (Y, M, C and B) and the photosensitive drum used in each image forming section 50 (Y, M, C and B) It is known that the optimum light intensity of the laser beam on the image plane fluctuates in relation to the individual error of the characteristic of 58 (Y, M, C and B). Further, the toner corresponding to each color component may be required to have different light intensity and beam diameter due to the characteristics of the colorant or the like or the transfer method. However, the light intensity and the beam diameter in the image forming unit 50 corresponding to the same color component need to be substantially uniform.

That is, the light intensities of the laser beam groups LY, LM, LC, and LB between the image forming units 50 (Y, M, C, and B) do not need to be uniform. The light intensity and the beam diameter on the image plane of each of the _i beams are required to be uniform.

For example, if the light intensities of the yellow laser beams LYa and LYb are the same and the beam diameter of LYa is LYb
If it is smaller, the width of the latent image written on the photosensitive drum 58Y by the yellow laser beam LYa is smaller than the width of the latent image written on the photosensitive drum 58Y by the laser beam LYb. As an example, when lines are written every two lines in the main scanning direction, the thickness of the lines varies, resulting in an uneven image.

Therefore, the yellow laser beams LYa and LYb, the magenta laser beams LMa and LMb,
The cyan laser beams LCa and LCb and the black (black) laser beams LBa, LBb, LBc and LBd are required to have the same light intensity on the image plane and uniform beam diameter.

In general, the higher the output, that is, the higher the power of a laser element, the smaller the beam emission angle. Therefore, when the same finite lens and the same diaphragm are used, the beam diameter on the image plane becomes large. Would. Therefore,
It is necessary that the rated outputs of the laser elements for the respective laser beams combined in the main scanning direction by the half mirror 12Y are equal to each other.

Thus, in the embodiment of the present invention, the rated outputs of the laser elements 3Ya and 3Yb that emit LYa and LYb combined in the main scanning direction by the half mirror 12Y are each set to 10 mW. Further, a laser element 3 that emits LMa and LMb combined in the main scanning direction by the half mirror 12M
The rated outputs of Ma and 3Mb are respectively 10 mW, and similarly, the rated outputs of the laser elements 3Ca and 3Cb that emit LCa and LCb combined in the main scanning direction by the half mirror 12C are 10 mW, respectively. The laser beams LBa, LBb, and LBc combined by the half mirrors 12B ₁ , 12B ₂ and 12B ₃
And laser elements 3Ba, 3Bb, 3 emitting LBd
The rated outputs of Bc and 3Bd are each set to 20 mW.

Thus, the respective beam groups, ie, LYa and LYb, LMa and LMb, LCa
And LCb and LBa, LBb, LBc and L
The beam diameter of the image plane in each beam group of Bd can be easily made uniform by using the same finite lens and diaphragm.

Here, suppose that the half mirrors 12B ₁ , 12B ₂ and 12B _{3 in} the optical device shown in FIG.
Assuming that the ratio of the transmittance to the reflectance is 1: 1, the laser elements 3Ba, 3Ba, 3Ba,
The rated outputs of 3Bb, 3Bc and 3Bd are respectively
It must be set to 40mW, 40mW, 20mW and 10mW. In this case, the beam diameter on the image plane varies due to the difference in the emission angle of the laser beam described above.

Here, each of the laser elements 3Ba, 3Bb, 3
The same rated output as Bc and 3Bd, ie, 40m
Using the laser element of W, the output when actually used,
40mW, 40mW, 20mW and 10m respectively
Although a method of controlling to W can be easily conceived, it is clear that the laser elements 3Bc and 3Bd are overspecified, and the cost is increased.

The number of half mirrors 12 prepared for each of the laser beams LY, LM, LC and LB is Ν _{i of the} number N of beams constituting each of the M sets of light sources.
Although there is one (one for yellow, magenta, and cyan, and three for black), the number of times that any laser beam is transmitted through the half mirror 12 is limited to one at a maximum.

In other words, the laser beams LYb, LM
a, LCb, and LBa are only reflected by the half mirror 12 (the number of transmissions = 0), and the remaining laser beams pass through the half mirror 12 only once.

As described above, by minimizing the difference between the number of times that each laser beam passes through the half mirror 12 and the number of times that the beams pass through each other, a problem that occurs when light other than parallel light passes through a parallel flat plate is achieved. And the influence of spherical aberration can be reduced. The laser beams LYb and LM that do not pass through the half mirror 12
a, LCb and LBa are each connected to a half mirror 1
By passing through a parallel flat plate having a refractive index equal to 2, it is possible to reduce fluctuations in optical characteristics due to the difference in the number of passes between beams.

Tables 1 to 3 show the pre-deflection optical system 7
2 shows the optical numerical data of FIG.

[0081]

[Table 1]

[0082]

[Table 2]

[0083]

[Table 3]

As is clear from Tables 1 to 3, the finite focal length lens 9 and the hybrid cylinder lens 11 corresponding to each color component use the same lens for any color component by itself. Note that, with respect to the direction in which the transport belt 52, which is the transfer belt, is rotated, the Ys located at the most upstream side in the rotational direction and the most downstream side in the rotational direction.
(Yellow) The pre-deflection optical system 7Y corresponding to the image forming unit 58Y and the B (black) pre-deflection optical system 7B corresponding to the image forming unit 58B have substantially the same lens arrangement. Axis is symmetric). The pre-deflection optical system 7M corresponding to M (magenta) and the pre-deflection optical system 7C corresponding to C (cyan) have a finite focal length lens 9 compared to the pre-deflection optical systems 7Y and 7B.
The distance between the lens and the hybrid cylinder lens 11 is widened.

On the other hand, the distance between the hybrid cylinder lens 11 and the reflecting surface of the light deflecting device 5 is determined to be maximum with respect to the laser beams at both ends, that is, the laser beam LY and the laser beam LB. As is apparent from FIG. 2, when each of the plurality of light sources is constituted by a plurality of lasers, each of the lasers 3 (Y, M, C and B) a, 3 (Y, M, C and B) b) Black third laser 3
Bc and the fourth black laser 3Bd, and the corresponding finite focus lenses 9 (Y, M, C and B) a, 9 (Y,
M, C and B) b, black third laser finite focus lens 9
Restrictions (mounting surface) on the arrangement of Bc and the black fourth laser finite focus lens 9Bd can be reduced.

Next, the function of the pre-deflection optical system that acts on the laser beam from each light source toward the light deflector will be described with reference to FIG. Since the functions of the lenses and the half mirror disposed between each light source and the light deflector are substantially the same, the laser beam LYa from the first yellow laser 3Ya to the polygon mirror 5a of the light deflector 5 is used. Will be described as a representative.

As shown in FIG. 3, the laser beam LYa emitted from the first yellow laser 3Ya is given a predetermined convergence by the finite focus lens 9Ya, passes through the stop 10Ya, and has a sectional beam shape. It is arranged in a predetermined shape.

A laser beam LYb from a second yellow laser 3Yb to be described later (FIG.
(Not shown), a laser beam LY (LYa + LYb) combined into a substantially single laser beam at a predetermined distance in the sub-scanning direction is provided by a laser combining mirror described later with reference to FIG. After passing through the non-reflection area of the unit 13, the laser beam is substantially united with the other three groups of laser beams LM, LC, and LB in a state viewed in the sub-scanning direction and guided to the optical deflector 5.

The hybrid cylinder lens 11Y has a first cylinder lens 17Y and a second cylinder lens 17Y whose surfaces in contact with air, that is, entrance surfaces are formed substantially cylindrical, and have substantially the same curvature in the sub-scanning direction. Is integrally formed by bonding between the exit surface of the cylinder lens 17Y and the entrance surface of the cylinder lens 17Y or by being pressed from a predetermined direction toward a positioning member (not shown). You. The first cylinder lens 17Y is formed of plastic, for example, PMMA (polymethyl methacryl). The second cylinder lens 19Y is formed of glass, for example, TaSF21. The cylinder lenses 17Y and 19Y are fixed to the finite focus lens 9Ya or 9Yb at an accurate interval via a positioning mechanism (not shown) formed integrally with the holding member 15.

By the way, the laser beam LYa cancels the coma generated when passing through the first and second imaging lenses 30a and 30b (see FIG.
(The dashed line extends from the entrance surface of the cylinder lens indicated by a.) The light is incident on the optical axis of the hybrid cylinder lens 11Y with eccentricity and inclination.

The laser beam LYb (not shown) is
The laser beam LYa is asymmetrically incident on the optical axis of the hybrid cylinder lens 11Y. When the laser beam LYb is displayed under the same conditions as in FIG. 3, the laser beam LYb is incident on the hybrid cylinder lens 11Y so as to substantially overlap with the laser beam LYb.

Tables 4 and 5 show optical numerical data of the post-deflection optical system used in combination with the pre-deflection optical system shown in Tables 1 to 3.

[0093]

[Table 4]

[0094]

[Table 5]

When the post-deflection optical systems shown in Tables 4 and 5 are used, even if the maximum value of the surface tilt of each reflecting surface of the optical deflector 5 is 1 minute, the beam on the image plane Is suppressed to 4 μm.

That is, the post-deflection optical system shown in Table 4
The light deflecting device 5 has a surface tilt correction function of 1/48 times the surface tilt of each reflecting surface. If the post-deflection optical system does not have the surface tilt correction function, if it is attempted to reduce the surface tilt between the reflecting surfaces of the optical deflector 5 to such an extent that the jitter is not visually perceived, 2 face falls
Since it must be reduced to about seconds, the polygon mirror body 5a becomes very expensive.

The effective field angle φ of the beam deflected by the light deflector 5 is 1.01237 radians (hereinafter, r
The effective image area width W including the horizontal synchronization signal detection area is 320 millimeters (hereinafter, referred to as mm), and the distance between the reflection point of each reflection surface of the light deflector 5 and the image plane. LT is 329.7797 mm. Here, by optimizing the effective field angle φ of the beam, the effective image area width W, and the distance LT between the reflection point and the image plane, 1.01237 = φ> W / LT = 0.97. In addition, while it is possible to reduce the deterioration of the imaging characteristics and scanning line bending required for the multi-beam due to environmental changes, it is possible to lower the laser drive frequency for driving the laser element used as the light source. Thus, the size of the optical scanning device can be reduced. Further, even if a plastic lens is used for the post-deflection optical system, an optical unit with less color shift with respect to changes in temperature and humidity can be provided.

Note that φ> W / LT is the effective angle of view φ,
W / LT (effective image area width / distance between reflection point and image plane), that is, a result obtained by simulation as a variable for optimization design. Here, φ <W /
It has been confirmed that in the LT region, the scanning line bending and the deterioration of the imaging characteristics become large with respect to the change in temperature and humidity.
It was also confirmed that manufacturing tolerances became stricter. On the other hand, in the region where φ> 1.2 (W / LT), it has been confirmed that the scanning line curve becomes large with respect to the change in temperature and humidity.

Therefore, the effective angle of view φ of the beam is preferably selected from the range of 1.2 (W / LT)>φ> W / LT. When evaluating the effective angle of view φ of the beam, an evaluation function shown in FIG. 4 is used. Here, referring to FIG. 4, it can be confirmed that the evaluation function becomes smaller as a whole when φ is around 1, but also becomes smaller when φ is around 1.1 (W / LT).

FIG. 5 shows that each of the pre-deflection optical systems 7 (Y, M, C and B) shown in FIG. 3 and Tables 1 to 3 is orthogonal to the rotation axis of the reflecting surface of the light deflector 5. Reflection surface 13 of each laser combining mirror in each direction (sub-scanning direction)
The laser beams LY, LM, and LC traveling from Y, 13M, and 13C to the light deflector 5 are shown (LY is LYa and LYb, LM is LMa and LMb, and LC is LCa
And LCb).

As is clear from FIG. 5, each of the laser beams LY, LM, LC and LB is applied to the light deflecting device 5.
Are guided to the light deflecting device 5 at mutually different intervals in a direction parallel to the rotation axis of the reflection surface. The laser beam L
M and LC are orthogonal to the rotation axis of the reflecting surface of the optical deflecting device 5 and asymmetrical across the surface including the center of the reflecting surface in the sub-scanning direction, that is, the surface including the optical axis of the optical scanning device 1. Are guided to each reflecting surface of the light deflecting device 5. Note that the laser beams LY, LM, L on the respective reflecting surfaces of the light deflecting device 5
The distance between C and LB is 2.26 m between LY and LM.
m, 1.71 mm between LM-LC and 1.45 mm between LC-LB.

FIG. 6 shows an optical member arranged between the light deflecting device 5 of the optical scanning device 1 and each photosensitive drum 58, that is, the image plane, when the deflection angle of the light deflecting device 5 is 0 °. The state as viewed from the sub-scanning direction is shown.

As shown in FIG. 6, the post-deflection optical system 30
The lens 3 is located between the second imaging lens 30b and the image plane.
A first folding mirror 33 (Y, M, C, and B) for bending 2 + 2 + 2 + 4 = 10 laser beams L (Y, M, C, and B) passed through Ob toward the image plane;
Laser beams LY, LM and LC bent by first folding mirrors 33Y, 33M and 33C
And third folding mirror 3 for further folding
5Y, 35M and 35C and 37Y, 37M and 37C are arranged. As is clear from FIG. 6, the laser beam LB corresponding to the B (black) image
Is returned by the first return mirror 33B, and then guided to the image plane without passing through another mirror.

The first and second imaging lenses 30a and 30b, the first folding mirror 33 (Y, M, C and B), and the second folding mirrors 35Y, 35M and 35C are respectively optically scanned. Intermediate base 1a of device 1
Then, for example, it is fixed to a plurality of fixing members (not shown) formed by integral molding by bonding or the like.

The third folding mirrors 37Y and 37Y
M and 37C are movably disposed in at least one direction related to a direction perpendicular to the mirror surface via a fixing rib and an inclination adjusting mechanism described later with reference to FIG.

The third folding mirrors 37Y, 37M, 3
7 + 2 + 2 + 4 = 10 laser beams L (Y, M, C, and B) between the mirror 7C and the first folding mirror 33B and the image plane and reflected through the respective mirrors 33B, 37Y, 37M, and 37C. ) Is the optical scanning device 1
In the position where light is emitted from the optical scanning device 1, dust-proof glass 39 (Y, M, C and B) for dust-proofing the inside of the optical scanning device 1 is further provided.
Is arranged.

Next, the optical characteristics between the hybrid cylinder lens and the post-deflection optical system will be described in detail.

The post-deflection optical system 30, that is, the first set of two
Since the second imaging lenses 30a and 30b are formed of plastic, for example, PMMA, when the ambient temperature changes between, for example, 0 ° C. and 50 ° C., the refractive index n becomes 1.4876 to 1.4
It is known to change to 789. In this case, the imaging plane on which the laser beams passed through the first and second imaging lenses 30a and 30b are actually focused, that is, the imaging position in the sub-scanning direction fluctuates by about ± 4 mm. .

On the other hand, a lens made of the same material as that of the lens used for the post-deflection optical system 30 is incorporated into the pre-deflection optical system 7 shown in FIG. 3 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, as compared with a conventional optical system in which the pre-deflection optical system 7 is a glass lens and the post-deflection optical system 30 is a plastic lens, the post-deflection optical system 30 is caused by a change in the refractive index due to a temperature change of the lens. Chromatic aberration in the sub-scanning direction, which is generated as a result, can be corrected.

However, the amount of chromatic aberration that can be corrected is proportional to the power of the plastic cylinder lens.
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. Is specified. Therefore, when the material used for the glass cylinder lens is specified, the focal length of the hybrid cylinder lens 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:
Only by the focal length of the hybrid cylinder lens,
It can be set. 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.

There is a method of setting the focal length of the hybrid cylinder lens by changing the refractive index by changing the glass material to adjust the focal length of the glass cylinder lens. However, depending on the glass material,
It is not always beneficial in terms of grindability, storage or transportation, and inevitably lower degrees of freedom.

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

However, the cost can be reduced most by giving a curvature to both sides of the plastic cylinder lens formed by molding and making the power of the plastic cylinder lens and the power of the hybrid cylinder lens independent functions. Further, according to the above method, processing accuracy and shape accuracy can be easily ensured.

FIG. 7 shows the first to fourth combined laser beams L (Y, M, C and B) passing between the light deflector 5 and the image plane shown in FIG. FIG. 3 is an optical path diagram illustrating a relationship between the apparatus 1 and an optical axis of a system in a sub-scanning direction.

As shown in FIG. 7, the first to fourth combined laser beams L (Y, M, C, and B) reflected by the reflecting surface of the optical deflector 5 are respectively applied to the first Between the imaging lens 30a and the second imaging lens 30b, in the sub-scanning direction, the light is guided to the image plane while intersecting with the optical axis of the system.

FIG. 8 shows a laser combining mirror unit 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 optical deflecting device 5. 13 is shown.

The laser combining mirror unit 13 is provided with first to third mirrors 13M, 13C and 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). 13B and first to third holding mirrors 13M, 13C and 13B.
And the base 13a which supports the respective holding portions 13α, 13β and 13γ. Note that the base 13a and the respective holding portions 13α, 13β, and 13γ
Is 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
As described above, the laser beam LY from the laser 3Ya and the yellow second laser 3Yb
Are guided directly to each reflecting surface. In this case, the laser beam LY is applied to the mirror 13M fixed to the base 13a side, that is, the first holding unit 13α with respect to the optical axis of the system of the optical scanning device 1.
And the base 13a.

Next, the laser beams LM, L reflected by the respective mirrors 13M, 13C and 13B of the combining mirror 13 shown in FIG.
The light intensity (light quantity) of the laser beam LY guided directly to C and LB and the light deflection device 5 will be considered.

According to the laser combining mirror unit 13,
Each of the laser beams LM, LC and LB is applied to each of the preceding laser beams L
In an area where M, LC, and LB are separated in the sub-scanning direction, they are turned back by ordinary mirrors (13M, 13C, and 13B). Therefore, each reflection surface (13M, 13C
And 13B), the amount of each laser beam L (M, C and B) supplied toward the polygon mirror body 5a after being reflected can be maintained at about 90% or more of the amount of light emitted from each hybrid cylinder lens 11. . 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 3Y corresponding to Y (yellow) is guided directly to each reflecting surface of the optical deflecting device 5 without being involved in any of the mirrors of the combining mirror 13, so that the output capacity of the laser is Mirrors (which can occur in other laser beams reflected by the composite mirror)
The error of the angle of incidence on each reflecting surface due to reflection at (13M, 13C and 13B) is removed.

Next, referring to FIGS. 2 and 6, the laser beam L (Y, M,
C and B) and the optical scanning device 1 through the post-deflection optical system 30.
Laser beams LY, LM, LC emitted from outside
And LB inclination and folding mirrors 33B, 37Y, 3
The relationship with 7M and 37C will be described.

As described above, the light is reflected by the polygon mirror 5a of the light deflecting device 5, and is reflected by the first and second imaging lenses 30a.
The laser beams LY, LM, LC, and LB having the predetermined aberration characteristics provided by the first and second mirrors 33Y, 33M, 33C, and 33B, respectively.
It is folded back in a predetermined direction via B.

At this time, the laser beam LB is reflected by the first folding mirror 33B, and then guided to the photosensitive drum 58b through the dustproof glass 39B.
On the other hand, the remaining laser beams LY, LM and LC
Are guided by the second folding mirrors 35Y, 35M and 35C, respectively, and
35M and 35C, the third folding mirror 3
7Y, 37M, and 37C, and further reflected by third folding mirrors 37Y, 37M, and 37C.
After being reflected by the dustproof glass 39Y, 39, respectively.
By M and 39C, an image is formed on each photosensitive drum at substantially equal intervals. In this case, the laser beam LB emitted by the first folding 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 return mirror 33B
From the optical scanning device 1 to the photosensitive drum 5
The light is emitted toward 8.

When a plurality of mirrors are present in the optical path, the laser beam LB changes various aberration characteristics of the image on the image forming surface which is increased (multiplied) according to the number of mirrors, or bends the main scanning line. Is useful as a reference ray 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 shown in FIG. 5, the number of mirrors in the post-deflection optical system related to the laser beam LB is one except for the polygon mirror 5a of the light deflector 5.
The number of mirrors in the post-deflection optical system related to the laser beams LC, LM, and LY (odd number) is three (odd number) except for the polygon mirror 5a. Here, with respect to any one of the laser beams LC, LM, and LY, the second
Assuming that the mirror 35 is omitted, the main scanning line bends 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. The beam, that is, the number of mirrors, becomes odd with the main scanning line bending direction due to the inclination of an odd-numbered lens or the like, which causes a color shift which is a harmful problem when reproducing a predetermined color.

Therefore, when a predetermined color is reproduced by superposing 2 + 2 + 2 + 4 = 10 laser beams LY, LM, LC and LB, the optical path of the polarized optical system 30 of each laser beam LY, LM, LC and LB. The number of mirrors disposed therein is substantially unified to odd or even.

FIG. 9 shows the distance L ₁ between the optical axis of the post-deflection optical system and the scanning line at one end, and the distance L ₁ between the optical axis of the post-deflection optical system and the scanning line at the other end. The relationship between the distance L _m and the distance ΔL _{max in} the direction parallel to the optical axis of the system between the scanning lines at both ends is shown.

These values (L ₁ , L _m and Δ
_Lmax ) is the distance Lo between the final lens surface and the image surface.
And the interval between beams indicated by M = 4 groups, the maximum value is set. However, if priority is given to the distance Lo between the final lens surface and the image surface, the demands on the optical system become severe, and the imaging characteristics, the bending of the scanning line,
There is a problem that variations in various characteristics due to environmental changes reach a level that cannot be ignored.

Therefore, as a result of designing many optical scanning devices and repeating mounting of optical members, the optical performance of the optical scanning devices can be maintained, and the distance between the photosensitive drums and the optical scanning device and each photosensitive member can be maintained. The condition which can secure the distance with a body drum was able to be found.

[0132] That is, between each distance _L 1, _{L m} and [Delta] L _max and Lo as described _{above, (ΔL max + L m +} L 1) /1.8> Lo Lo> (ΔL max + L m + L 1) / It has been confirmed that the optical performance of the optical scanning device can be maintained and the distance between the photosensitive drums and the distance between the optical scanning device and each photosensitive drum can be ensured on condition that 2 is satisfied. .

More specifically, the beam that has passed through the final lens (second imaging lens 30b) ignores the inclination,
As shown in FIG. 10, it can be approximated that the light is emitted in parallel with the line connecting the optical axes of the two lenses 30 a and 30 b of the post-deflection optical system 30.

Further, the reflection of the beam separated at the position closest to the lens side by the first and second mirrors is approximated by l times of reflection, and this reflection point is represented by (x, y) = (0, 0). ) And the photoconductor drum is considered to be above the optical axis (above the plane of the paper) (the coordinate system here is different from the coordinate system of other drawings). Further, the point of reflection by the third mirror is (x ₁ , y ₁ ), the coordinates of the image plane are (x ₂ , y ₂ ), and the coordinates of the image plane of the beam passing through only one folding mirror are (x ₃ , Y ₃ ).

At this time, in order to maximize the volume in which the process-related components can be mounted, if y1 is positive, FIG.
As shown in (a), (x ₃ , y ₃ ), (x ₂ , y
_2), may be to maximize the area _{S 1} surrounded by _(x 1, _{y 1)} and _(x 3, _{y 1).} Further, if _{y 1} is negative, by _{(x 3, y 3),} (x 2, y 2), the maximum _(x 1, 0) and _(x 3, 0) area _{S 2} surrounded by I just need.

Hereinafter, in order to maximize the area S ₁ or the area S ₂ , the angle between the beam reflected by the second mirror and the optical axis of the post-deflection optical system is set to Ψ, and the reflection at the second mirror is performed. placing a point distance between the reflection point of the third mirror and _{L 1,} y _{1, x 1,} respectively,

(Equation 3)

[0137]

(Equation 4)

Is shown by

[0139] The optical path length from the reflection point by the second mirror to the image plane placed and L _2, beam after reflection on the third mirror is perpendicular to the optical axis of the post-deflection optical system (if such and _{S 1} or _{S 2} is approximated to the maximum) placing the coordinates of the image plane and _(x 2, _{y 2) to, x 2 = x 1 (a} -3) y 2 = y 1 + L 2 -L ₁ (a-4).

[0140] On the other hand, a beam separated at a position closest to the lens side, and finally the distance of the beam reflected by the first mirror putting a _{y 4, x 3 = - (} L 2 -y 4 -y _{2) (a-5) y} 3 = y 2 (a-6) is satisfied.

Accordingly, S ₁ and S ₂ are respectively S ₁ = (y ₂ −y ₁ ) (x ₂ −x ₃ ) (a−7) S ₂ = y ₂ (x ₂ −x ₃ ) (a -8).

[0142] Incidentally, y ₄ is at least, from being set to a distance that can separate the three beams at a position where the beam does not overlap, as positioned at regular intervals on the image plane of the respective beams, respectively from the image plane The optical path length up to the separation point is represented by L ₂ , (L ₂ − (x ₂ −x ₃ ) / 3/2) and 2 (L ₂ − (x ₂ −x ₃ ) / 3/2). You.

On the other hand, assuming that the beam radius on the image plane is ωo, the divergence angle is represented by λ / (πω). Therefore, ζ is a coefficient including the effect of diffraction by the stop of the optical system before deflection. Then, _{y 4} is,

(Equation 5)

Are shown.

Note that ζ indicates that the beam diameter at the image plane is ωo
In general, l. 4 is set. Also, ζ
Is specified to be about 2.8, especially for the first mirror (separation mirror), in order to eliminate the influence of diffraction of an adjacent beam.

[0146] The (a-9) expression, and solving for _{y 4,}

(Equation 6)

Is obtained.

Here, the equations (a-10) and (a-1) to (a-6) are substituted into the equations (a-7) and (a-8), and the smaller of S1 and S2 is obtained. Is plotted on the vertical axis, and FIG. 11 is obtained. Note that in FIG.
= 1.4, L2 = 175, λ = 0.00068 and ω
under the conditions of o = 0.025, the horizontal axis Ψ from -π to [pi, the depth direction axis _{L 1,} is from 0 to 175.

As is clear from FIG. 11, S ₁ and S
_The condition that the smaller value of ₂ becomes the maximum is Ψ = 0 (a−11).

In the following, a solution that can obtain 0 by differentiating S ₁ with L ₁ is obtained as follows.

(Equation 7)

Is obtained.

[0152] Here, in practice, L _2, when the numerical value obtained by adding the final lens surface and the distance of the first folding mirror is a Lo, approximated to L 2 ₌ Lo,

(Equation 8)

This is transformed into

Therefore, by substituting equation (a-11) into equation (a-13),

(Equation 9)

Is derived.

Hereinafter, for λ = 0.0063, which is a combination of ranges that are currently considered to be practicable, ζ is from 1.4142 to 2.8 on the horizontal axis, ωo is 0 on the axis in the depth direction. .02 = to 0.06 (a-1
4) The values of the equation are shown in FIG. Similarly, λ = 0.0008
On the horizontal axis, 軸 is changed from 1.4142 to 2.8,
On the axis in the depth direction, FIG. 13 shows values of the expression (a-14) in which ωo is set to 0.02 to 0.06.

Referring to FIG. 12 and FIG. 13, optical scanning is performed under the condition that (ΔL _max + L _m + L ₁ ) /1.8> Lo Lo> (ΔL _max + L _m + L ₁ ) / 2. a possible maintain the optical performance of the device, i.e. the component to be implemented volume of process relationships that the distance can be secured between the photosensitive drum mutual spacing and the optical scanning device and the photosensitive drum with respect to S ₁ It is acknowledged that it will be maximum.

[0158] In the above description,
The photoconductor drum interval was assumed to be constant.
The photosensitive drum on which the beam is guided only once
If the diameter is larger than the other photosensitive drums by ΔD, L
_mIs reduced by ΔD, and ΔL _maxIs increased by ΔD
This makes it possible to maintain the height of the transfer position constant. this child
From (ΔL_max+ L_m+ L₁) Is the photoconductor
The same is true even if the ram diameter is not uniform. Therefore,
The equation (a-15) shows the distance between the photosensitive drums and the photosensitive drum.
An image forming apparatus with one of the drum diameters set unevenly
It is also effective for the position.

When the above conditions are applied to the optical scanning devices shown in FIGS. 2 to 9 and FIGS. 14 to 16 in order to confirm this condition, (ΔL _max + L _m + L ₁ ) /1.8= 187.25
Since mm Lo = 175 mm (ΔL _max + L _m + L ₁ ) /2=168.527, it is recognized that the above condition is satisfied.

Thus, the entire post-deflection optical system and the size of the lens can be appropriately set, and the difference in the amount of bending caused by the environmental change of the M beam groups can be suppressed. At the same time, undesirably increasing the size of the optical scanning device is suppressed. Further, since the angle of view can be increased as compared with an optical scanning device having substantially the same size, the image frequency can be set lower.

FIG. 14 is a schematic diagram showing the positional relationship of the laser beam guided to the image plane.

FIG. 14 (a) shows laser beams LM and LC in which two laser beams are put together, and FIG. 14 (b) shows four laser beams which are put together. 3 shows an example of the laser beam LB.

In FIGS. 14A and 14B, the hatched portion indicates that the light intensity of the laser beam is 1 / e ²
This corresponds to the area described above. The cross-sectional shape of the beam is such that the 1 / e ² diameter in the main scanning direction is 0.8 to 1.2 times the distance (pitch) between adjacent beams, and 1 / e ² in the sub-scanning direction.
/ ^{E 2} diameter, pitch 1.2~l. It is set to be about six times. In addition, each adjacent beam is set so as to scan adjacent scanning lines on the image plane mutually (each of four beams for LB), and 1 / e ²
It is shifted by 1 / e ² diameter or more in the scanning direction so that the diameters do not overlap.

That is, when an image is exposed using a laser beam in which two or more laser beams are combined, the light intensity of each laser beam is 1 / e ²
When the 1 / e ² diameters described above overlap each other between laser beams, there is a problem that a beam shape is generated due to interference between the beams. However, as shown in FIGS. 14 (a) and 14 (b), By slightly shifting the beam interval and the scanning direction position, it is possible to prevent a change in beam shape due to interference between beams.

FIG. 15 shows the folding mirror for horizontal synchronization in detail.

According to FIG. 15, the folding mirror 25 for horizontal synchronization receives the combined laser beams LY and L
The M, LC, and LB are reflected at different timings to the horizontal synchronization detector 23 in the main scanning direction, and are provided with substantially the same height on the horizontal synchronization detector 23 in the sub-scanning direction. The first to fourth folding mirror surfaces 25Y, 25M, 25C and 25B formed at different angles in both the scanning direction and the sub-scanning direction, and the respective mirrors 25 (Y, M, C and B) are integrally held. It has a mirror block 25a.

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

Thus, not only can each laser beam LY, LM, LC and LB deflected by the optical deflector 5 be made incident on the same detection position of one detector 23, but also For example, it is possible to remove a shift of the horizontal synchronizing signal due to a sensitivity or a position shift of each detector, which is a problem when a plurality of detectors are arranged. It should be noted that the horizontal synchronization detector 23 is provided with a laser beam group LY, L
M, _{N i} times by one per LC and LB are incident total of four times one beam (LY, the LM and LC 2
It is needless to say that the horizontal synchronization signal is obtained four times (for LB, four times). Also, the mirror block 25a
The mirror surface of the mold is designed so that it can be formed from a single block by cutting, and is devised so that it can be removed from the mold without the need for undercut.

FIG. 16 shows the third folding mirror 37Y,
It is a schematic perspective view which shows the support mechanism of 37M and 37C.

According to FIG. 16, the third folding mirror 3
7 (Y, M, and C) are fixed portions 41 (Y, M, and C) integrally formed with the intermediate base 1a at predetermined positions of the intermediate base 1a of the optical scanning device 1, respectively. The portion 41 (Y, M, and C) is held by a mirror pressing leaf spring 43 (Y, M, and C) opposed to the corresponding mirror with the corresponding mirror interposed therebetween.

The fixed portions 41 (Y, M and C) are formed as a pair at both ends (main scanning direction) of each mirror 37 (Y, M and C).

On one fixing portion 41 (Y, M and C), two projections 45 (Y, M and C) for holding the mirror 37 (Y, M and C) at two points are formed. Have been. The other fixing portion 41 (Y, M, and C) has a set screw for supporting the mirror held by the projection 45 (Y, M, and C) movably in the vertical direction or along the optical axis. 47 (Y, M and C) are arranged.

As shown in FIG. 16, each of the mirrors 37 (Y, M, and C) is provided with a projection 45 by moving a 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. 17 is a schematic diagram showing the state of exposing a laser beam to the image plane, that is, forming a latent image on the photosensitive drum. In FIG. 17, a black laser beam, that is, four laser beams emitted from the light source 3B will be described as an example.

According to FIG. 17, the area described by the solid line is the area where the image is formed (the laser beam for image formation is deflected) on the reflection surface having the polygon mirror 5a of the optical deflector 5.
The central area corresponds to the effective image area. The other portion is a region where a laser beam that does not contribute to image formation is deflected as an invalid region. The dashed-dotted line indicates an area formed on the reflection surface next to the polygon mirror 5a.

FIG. 17A shows the polygon mirror 5 of the light deflecting device 5.
In the case where Ν = 4 laser beams deflected by a certain reflecting surface are formed so as to scan at a constant speed on a predetermined image plane, p is a distance between beams in the sub-scanning direction (beam pitch) and k is a multi-plane. When the number of reflection surfaces of the mirror 5a is used, the angle between the scanning line and the direction in which the photosensitive drum is rotated, that is, the amount δ at which the scanning line is inclined with respect to the sub-scanning direction.

Here, the slope δ is obtained by δ = tan ⁻¹ [(N × p × k × φ) / (4 × π × W)]. N indicates the number of laser beams, φ indicates an effective angle of view, and W indicates an effective image area width. Also, the slope δ
Is delayed (-) with respect to the rotation direction of the photosensitive drum.

FIG. 17B shows an example of correcting the inclination δ obtained from FIG. 17A, in which the inclination δ is set between the scanning line and the rotation direction of the photosensitive drum, that is, the sub-scanning direction. Indicates that the scanning line is parallel to the rotation direction of the photosensitive drum (the scanning line and the axis of the photosensitive drum are parallel). In this case, the inclination δ matches the angle shown in FIG. Needless to say, the inclination δ is set to advance (+) in the rotation direction of the photosensitive drum. The inclination δ is given to the entire unit of the optical scanning device 1 or at least to all of the optical members involved while the laser beam reflected by the optical deflecting device is guided toward the photosensitive drum (optical scanning device 1). Is arranged in the image forming apparatus 100, the axis connecting the light deflecting device 5 and each of the photosensitive drums 58 (Y, M, C and B) is inclined by δ with respect to the axis of each of the photosensitive drums 58. Placed). In order to optimally set the inclination angle δi for each beam group, the folding mirrors 35 and 37 must be
What is necessary is just to incline by δi−δ in the main scanning direction.

FIG. 17 (c) shows the write start position by four beams of the scanning line corrected in parallel with the rotation direction of the photosensitive drum by the method shown in FIG. 17 (b). As shown in FIG. 13C, the reference position for horizontal synchronization of the four laser beams is inclined by an angle δ with respect to the scanning line, so that the writing start position is improved so as to be orthogonal to the rotation direction of the photosensitive drum. it can.

By the way, the process speed is set to v (mm /
s), the rotation speed of the rotating polygon mirror 5a of the light deflector 5 is set to Np
(rpm), the distance by which the surface of the photosensitive drum is moved with respect to the time when the laser beam is exposed by one reflecting surface of the rotary polygon mirror 5a is 60 v / (NpN) = Q (m)
m). That is, Q is a function of the process speed, and the inclination δ of the scanning line is δ = tan ⁻¹ [(N _i × p × k × φ) / (4 × π × W)] = tan ⁻¹ (N _{i × 60vφ / (4πWNp))} = tan -1 (15N i v (φ / πWNp)) becomes a function of the process speed.

[0181] As described above, when the laser beam of the M groups comprise a N beams, in the direction opposite to the tilt generated when the beam of the N _i present are guided to the respective photosensitive drums, the entire optical scanning device Alternatively, the inclination of the scanning line can be corrected by tilting all of the optical members involved while the laser beam reflected by the light deflecting device is guided toward the photosensitive drum. Thereby, even when the number N of beams per group is increased, it is possible to prevent the horizontal line of the output image from being inclined.

Next, referring to FIGS. 18 to 22, N _i
The phase difference between each of the laser beams will be described. Here, a case where there are two beams will be described as an example, but the same applies to a case where there are three or more beams.

FIG. 18A shows the intensity distribution when the phase difference between adjacent beams is 0 degree, and FIG. 18B shows the intensity distribution when the phase difference is 180 degrees. . Hereinafter, βp is the e- ² diameter of the beam in the main scanning direction (p is the beam pitch), and αp is e in the sub-scanning direction.
^-2 diameter, ζ represents half-exposure amount of each photosensitive drum / average exposure energy, η represents the relative intensity of one beam to the peak intensity of the other beam at the midpoint of the line connecting the centers of two adjacent beams. Strength. Hereinafter, α = 1.
2, β = 0.8, ζ = 0.25, η = 0.211, and p = 0.042 mm. The above condition indicates that the beam center position is shifted by 0.042 mm in the sub-scanning direction and 0.0096 mm in the main scanning direction.

[0184] Figure 18 (a) and FIG. 18 (b) As is clear from, applying a laser beam of N _i present simultaneously by N _i number of laser elements of the source beam per group is Ni It can be seen that the intensity distribution of the laser beam reaching each photosensitive drum changes as a result of being affected by the interference due to the phase difference. That is, FIG.
If the phase difference is 0 degree as shown in FIG. 8 (a), the intensity distribution between the two beams is increased to reinforce the exposure amount, and if the phase difference is 180 degrees (see FIG. ))
It is noted that a valley of the intensity distribution occurs between the two beams.

FIGS. 19 (a) and 19 (b) show the intensity distribution on the photosensitive drum shown in FIGS. 18 (a) and 18 (b) normalized by the average exposure energy, respectively.
That is, the result obtained by integrating in the y direction is 1
It is a graph obtained by dividing the result obtained by integrating the intensity distribution in the case of only one beam in the y direction by p. 18 (a) and 18 (b),
FIG. 19A corresponds to a phase difference of 0 degree, and FIG. 19B corresponds to a phase difference of 180 degrees.

Referring to FIG. 19 (a), even in the middle of two beams, half-exposure amount (in this graph, since the average exposure energy is 1, half-exposure amount =
(Half exposure / average exposure energy × average exposure energy = × average exposure energy) 0.2
It is recognized that a light intensity greater than 5 is ensured.

On the other hand, in FIG. 19B, it can be confirmed that light intensity satisfying the half-exposure amount cannot be obtained in the valley of the intensity distribution.

This means that the phase difference between the two beams is 18
The valley of the intensity distribution that occurs when the angle is 0 degrees indicates that, in the case of regular development, the image is developed as a latent image in spite of the unexposed area, contrary to the center of each beam.
Further, in the case of reversal development, the image is not developed, that is, an image defect occurs, even though it is an exposed portion. If the wavelengths of the laser beams emitted from the laser elements are not exactly the same, the phase difference between the two beams is
It will fluctuate over time.

FIGS. 20 (a) and 20 (b) correspond to FIG.
In addition, a group of laser beams (two beams) having an optical scanning device in which the embodiment of the present invention shown in FIG. 12 is incorporated is applied in the same manner as shown in FIGS. 18 (a) and 18 (b). The result of obtaining the distribution is shown. Where α,
Let β, ζ, η and p be α = 1.2, β =
0.8, ζ = 0.25, η = 0.135 and p = 0.
042 mm. Note that the above conditions are such that the beam center position is 0.042 mm in the sub-scanning direction,
0.0187 mm, respectively, indicating that they are shifted.
The phase differences are 0 degree and 180 degrees.

As is clear from FIGS. 20 (a) and 20 (b), the intensity distribution of the laser beam due to the two laser beams reaching each photosensitive drum is not affected by the phase difference of 0 degree. If (FIG. 20 (a)), the intensity distribution between the two beams is increased in the direction of constructive exposure, while if the phase difference is 180 degrees (FIG. 20 (b)),
It is noted that a trough of the intensity distribution occurs between the two beams.

FIGS. 21 (a) and 21 (b) show the intensity distribution on the photosensitive drum shown in FIGS. 20 (a) and 20 (b), respectively, and FIGS. 18 (a) and 18 (b).
As in (b), the result normalized by the average exposure energy is shown. 18 (a) and 18 (b).
Similarly, FIG. 21A shows that the phase difference is 0 degree, and FIG.
1 (b) corresponds to a phase difference of 180 degrees.

As is clear from FIGS. 21 (a) and 21 (b), in the optical scanning device incorporating the embodiment of the present invention shown in FIGS. It is recognized that a light intensity larger than the normalized half-life exposure amount of 0.25 is ensured regardless of whether the angle is 0 degree or 180 degrees.

Next, a description will be given of conditions under which a light intensity larger than the half-exposure amount of the photosensitive drum can be provided even when the phase difference between the two beams is 180 degrees.

As described above, the beam interval in the sub-scanning direction, ie, the beam pitch is p, the e- ² diameter of the beam in the main scanning direction is βp, the e- ² diameter in the sub-scanning direction is αp, and the photoreceptor is half-exposure. When the amount / average exposure energy is Δ, the relative intensity to the peak intensity of one beam at the midpoint of the line connecting the centers of two adjacent beams is denoted by η, the sub-scanning direction is z, and the main scanning direction is z Let y be one beam at coordinates (y, z) = (0,0) and the other beam at coordinates
It is assumed that (y, z) = (δy, p).

At this time, the relative intensity η at the midpoint of the line connecting the centers of two adjacent beams is. η = exp (−2χ) (c−1).

At this time, χ is

(Equation 10)

Is represented by

On the other hand, δy giving the relative intensity η at the midpoint of the line connecting the centers of two adjacent beams is
By solving the equations (c-1) and (c-2) for δy,

[Equation 11]

Here, χ = −0.5 ln (η);
Required by

Therefore, the coordinates (y, z) = (0, 0) where the e- ² diameter of the beam in the main scanning direction is βp and the e- ² diameter in the sub-scanning direction is αp, and the coordinates (y, z) = (Δ
The electric field distribution of the beam having the peak intensity at (y, p) is

(Equation 12)

And

(Equation 13)

Are represented by

Note that rz and ry in the equations (c-4) and (c-5) are respectively expressed as rz = αp / 2 (c-6) ry = βp / 2 (c-7).

Next, the average intensity required to normalize the intensity distribution is calculated.

First, when the equation (c-5) is integrated in the main scanning direction, that is, in the y direction,

[Equation 14]

Is obtained. * In the equation (c-8) represents a complex conjugate number.

Next, when the equation (c-8) is integrated in the sub-scanning direction, that is, the z direction, and this is divided by the beam pitch p,

(Equation 15)

The average intensity is obtained from the above.

Here, when both the first laser and the second laser are turned on, the energy received at a certain place is not changed in intensity in the main scanning direction, that is, in the y direction because the beam is scanned in the main scanning direction. It is proportional to the integrated value.

At this time, at a specific place where the energy becomes the smallest, an energy larger than the half-exposure amount of the photosensitive drum is given, so that the phase difference between the laser beams from the two lasers is 180 degrees. In addition, it is possible to prevent the occurrence of image defects and supply of toner to unexposed portions. Since the position of the place where the energy becomes the smallest is the z-direction coordinate of the midpoint of the line connecting the centers of two adjacent beams, it can be obtained by z = p / 2 (c-10).

At this time, the electric field at the location determined by the equation (c-10) is represented by e ₁ -e ₂ . The value obtained by normalizing the value obtained by integrating the light intensity in the main scanning direction, that is, the y direction, with the average exposure energy is as follows:

(Equation 16)

Are indicated by In addition, in the expression (c-11), since e ₁ -e ₂ is a real number from the expressions (c-4) and (c-5), (e ₁ -e ₂ ) ^* × (e _1-
e ₂ ) = (e ₁ −e ₂ ) ² ).

The fact that the numerical value shown in the expression (c-11) becomes larger than the half-exposure exposure amount / average exposure energy of the photosensitive drum is represented by i ₂ ≧ ζ (c-12).

By substituting equation (c-11) into equation (c-12) obtained in this way,

[Equation 17]

Is derived.

Therefore,

(Equation 18)

By setting η so that is satisfied,
When using a group of laser beams in which two or more laser beams are grouped together, it is not necessary to consider the phase difference between adjacent laser beams.

In the optical scanning device incorporating the embodiment of the present invention shown in FIGS. 2 to 12,
(c-13), η <0.155354 is derived.

Here, in the examples shown in FIGS. 20 and 21, η = 0.135, and in the examples shown in FIGS. 18 and 19, η = 0.111. Therefore, it is recognized that the expression (c-13) is useful.

FIG. 22 shows a graph of α which is generally used.
6 is a graph showing the possible values of η, which is the limit, for ζ and ζ. That is, by setting each element of the optical scanning device so that η falls below the hatched area in FIG. 22, it is not necessary to consider the phase difference between adjacent laser beams.

Next, the operation of the image forming apparatus 100 will be described with reference to FIGS.

When an image formation start signal is supplied from an operation panel (not shown) or a host computer, each image forming section 50 (Y,
M, C and B) are warmed up, and the polygon mirror 5a of the light deflecting device 5 of the optical scanning device 1 is rotated at a predetermined rotation speed under the control of the image control CPU 111.

Subsequently, under the control of main controller 101,
Image data to be printed is taken into the RAM 102 from an external storage device, a host computer, or a scanner (image reading device). Part (or all) of the image data taken into the RAM 102 is stored in each image memory 114 (Y, M, C and B) under the control of the image control CPU 111 of the image control unit 110.

Under the control of main controller 101, feed roller 72 is controlled based on a predetermined timing, for example, a vertical synchronizing signal from timing control section 113 or the like.
, And one sheet P is taken out of the sheet cassette 70. The picked-up paper P is provided by the registration rollers 72 to Y, M, C and B provided by the image forming operation of each image forming unit 50 (Y, M, C and B).
The timing is matched with each toner image of the suction roller 74.
As a result, the sheet is guided toward each image forming unit 50 as the conveyor belt 52 rotates.

On the other hand, in parallel with or at the same time as the feeding and conveying operation of the paper P, each of the laser driving units 116 (Y, M, C, and) is controlled based on the clock signal CLK output from the timing setting device (clock circuit) 118. B) is activated, and each data control unit 115 (Y, M, C
And B), the image data DAT held in the RAM 102 is stored in each of the light sources 3 (Y, M, C, and B).
Supplied to As a result, the laser beam for one line is sequentially applied to each photosensitive drum 5 of each image forming unit 50 (Y, M, C, and B) from a predetermined position of the effective printing width in the main scanning direction.
8 (Y, M, C and B).

Thus, each data control unit 115
(Y, M, C and B) controls each laser drive unit 1
16 (Y, M, C, and B), image data is transferred to change the intensity of each laser beam L (Y, M, C, and B) emitted from each light source 3, and each image forming unit 50 (Y, M, C and B) of photosensitive drums 58 (Y, M
M, C, and B), an image without deviation is formed by an image clock having a constant clock length in one scan of the laser beam.

The first to fourth image forming units 50 (Y,
M, C and B) of the respective photosensitive drums 58 (Y,
Each of the first to fourth laser beams L (Y, M, C and B) formed on the respective photoconductor drums 58 (Y, M) is charged to a predetermined potential. , C and B), the electrostatic latent image corresponding to the image data is formed on each photoconductor drum 58 (Y, M, C and B) by changing the potential based on the image data.

This electrostatic latent image is stored in each developing device 62 (Y,
M, C and B), the image is developed with a toner having a corresponding color, and is converted into a toner image.

Each toner image is transferred to each photosensitive drum 5
8 (Y, M, C, and B), the paper P is moved toward the paper P being transported by the transport belt 52, and is transferred by the transfer device 64 at a predetermined timing. Is transferred at a predetermined timing.

As a result, four color toner images that are accurately overlapped on the paper P are formed on the paper P. In addition,
After the toner image is transferred to the sheet P, the remaining toner remaining on each of the photosensitive drums 58 (Y, M, C, and B) is removed by the cleaner 66 (Y, M, C, and B). The remaining potential remaining on each photoconductor drum 58 (Y, M, C and B) is equal to the static elimination lamp 68 (Y, M, C and B).
And is used for the subsequent image formation.

Paper P electrostatically holding toner images of four colors
Is further transported with the rotation of the transport belt 52, is separated from the transport belt 52 by a difference between the curvature of the belt drive roller 56 and the straightness of the sheet P, and is fixed by the fixing device 8.
You will be guided to 4. After the respective toners of the sheet P guided to the fixing device 84 are melted by the fixing device 84, the toner image as a color image is fixed.
The sheet is discharged to a discharge tray (not shown).

On the other hand, while the transport belt 52 after supplying the paper P to the fixing device 84 is further rotated, undesired toner remaining on the surface is removed by the belt cleaner 82, and is again supplied from the cassette 70. Is used to transport the paper P.

[0233]

As described above, according to the optical scanning device of the present invention, M beams are provided on the reflecting surface of the deflecting means.
The beam is incident from one end such that the interval between the beam groups monotonically increases, and the beam group at one end having the smallest interval between the beam groups is incident so as to intersect with the beam deflected by the deflecting device. This reduces the variation in the imaging characteristics of the beam groups and the bending of the scanning lines between the beam groups. Therefore, deterioration of image quality can be prevented. Note that the size of the optical scanning device is also reduced.

According to the optical scanning device of the present invention, L
The distance between _one of the second system of optical means and the optical axis of the end of the scan line, the distance between the system and the optical axis of the other end of the scanning lines of the second optical means L _m and ΔL _{When max} is the distance in the direction parallel to the optical axis of the system between the scanning lines at both ends, the final distance Lo between the lens surface and the image surface is (ΔL _max + L _m + L ₁ ) /
l. _{8>Lo> (ΔL max +} L m + L 1) /
2 is set. Thereby, the bending of the scanning line between the beam groups is reduced. The size of the lens and the size of the optical scanning device can be prevented from being undesirably increased.

Further, according to the optical scanning device of the present invention,
When Lt is the distance between the reflection point on the deflecting means and the image plane, and W is the effective image area width including the area for detecting the horizontal synchronization signal, the effective angle of view φ of the beam deflected by the deflecting means.
Is set to satisfy φ> W / Lt. As a result, it is possible to prevent the bending of the scanning line, the deterioration of the imaging characteristics due to the change in the environment, and the increase in the degree of the bending of the scanning line. Therefore, a low-cost plastic lens can be used as a single lens, and the cost of the optical scanning device can be reduced.

Further, according to the optical scanning device of the present invention, the angle of incidence and the position on the M sets of optical members to which positive power is given only in the sub-scanning direction are set with respect to the optical axis of the optical members. Since it is set to be asymmetric, it is possible to reduce the influence of coma aberration generated on a laser beam passing through a position spaced apart from the optical axis of the system in the sub-scanning direction. Thus, it is possible to prevent the resolution of the image from being reduced.

Furthermore, according to the optical scanning device of the present invention, since the number of times each beam passes through the translucent mirror is 1 or 0, when the convergent laser beam is incident on the parallel plate, Variations of the resulting aberrations among the beam groups are less likely to occur, and image quality can be prevented from deteriorating.

Further, according to the optical scanning device of the present invention, when p is the scanning pitch in the sub-scanning direction and k is the number of rotating polygon mirrors, the scanning line is δ with respect to the traveling direction of the image carrier. = Tan ^-1 (N _i × p × k × φ / (4 × π ×
W)), the scanning line can be prevented from being inclined with respect to the axis of the photosensitive drum, that is, the sub-scanning direction.

Furthermore, according to the optical scanning device of the present invention, p is the pitch of the beam in the sub-scanning direction, β is e− ² diameter / p in the main scanning direction of the beam, and α is e in the sub-scanning direction of the beam. ^{- second} diameter / p, half decay exposure / average exposure energy of ζ photoreceptor, and the relative intensity to the peak intensity of l one of the beam at the middle point of the line connecting the two adjacent beam center of the η When

[Equation 19]

Is satisfied. Thus, the influence of interference caused by adjacent laser beams N _i the irradiated on the image plane, images or missing, it is possible to prevent the toner in the unexposed portion is attached. Further, since there is no need to consider the influence of the phase difference between the laser beam of the laser beam of the N _i present, the cost of the apparatus can be reduced.

Further, according to the optical scanning device of the present invention, the M sets of optical members to which the positive power is given only in the sub-scanning direction are made of a glass single-sided cylinder lens and a post-deflection optical system lens. Therefore, the degree of freedom of the material usable for the glass lens is increased. Therefore, the cost of the optical scanning device is reduced.

Furthermore, according to the optical scanning device of the present invention, M light beams, which are arranged as M = 1 to M = j, are arranged, and each of the light beams transmitted through the lens located on the side closer to the light source is M light beams. The output of each light source for each M can be made substantially equal by optimizing the number of combining means and the reflectivity for combining the light sources. As a result, the costs of the laser element, the laser driving device, and the synthesizing unit are reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus using a multi-beam optical scanning device according to an embodiment of the present invention.

FIG. 2 is a schematic plan view showing an arrangement of optical members of an optical scanning device incorporated in the image forming apparatus shown in FIG.

FIG. 3 is a partial cross-sectional view of the optical scanning device shown in FIG. 2 cut along an optical axis of a system between a first light source and a light deflecting device.

FIG. 4 is a graph showing an evaluation function for evaluating an effective angle of view of a beam in the optical scanning device shown in FIG. 2;

5 is a partial sectional view of the optical scanning device shown in FIG. 2 in a sub-scanning direction, and is a schematic diagram showing states of first to fourth laser beams directed to the optical deflecting device.

6 is a schematic cross-sectional view of the optical scanning device shown in FIG. 2 cut at a position where the deflection angle of the optical deflection device is 0 °.

FIG. 7 is a schematic plan view showing a state where optical members of the post-deflection optical system of the optical scanning device shown in FIG. 2 are arranged.

FIG. 8 is a plan view and a side view showing a laser combining mirror unit of the optical scanning device shown in FIG. 2;

FIG. 9 is a schematic diagram showing a region where a photosensitive drum incorporated in the image forming apparatus can be arranged when the optical scanning device shown in FIG. 2 is used.

FIG. 10 is a schematic diagram showing a method for defining a volume in which process-related components used in the optical scanning device shown in FIG. 2 can be mounted.

FIG. 11 is a graph showing an area in which the process-related components shown in FIG. 10 can be mounted.

FIG. 12 shows a coefficient 含 む including the effect of diffraction due to the aperture of the pre-deflection optical system for λ = 0.0063, which is considered to be practicable, and one beam at the midpoint of a line connecting the centers of two adjacent beams. 5 is a graph showing the range of relative intensity η with respect to the peak intensity of FIG.

FIG. 13 shows a coefficient 含 む including the influence of diffraction by the aperture of the pre-deflection optical system with respect to λ = 0.0008 which is considered to be practicable.
And a graph showing the range of the relative intensity η to the peak intensity of one beam at the midpoint of the line connecting the centers of two adjacent beams.

14 is a schematic diagram showing a positional relationship between a plurality of laser beams on an image plane when the optical scanning device shown in FIG. 2 is used.

FIG. 15 is a schematic perspective view of a folding mirror for detecting horizontal synchronization in the optical scanning device shown in FIG. 2;

FIG. 16 is a schematic perspective view showing an adjustment mechanism of an emission mirror of the optical scanning device shown in FIG.

FIGS. 2 to 9 and FIGS. 14 to 16
FIG. 2 is a schematic diagram showing a beam position of a laser beam applied to a photosensitive drum by the optical scanning device shown in FIG.

FIG. 18 is a graph illustrating a relationship between a phase difference and an intensity distribution of a laser beam applied to a photosensitive drum.

FIG. 19 is a graph obtained by normalizing the intensity distribution shown in FIG. 18 with an average exposure energy.

FIGS. 2 to 9 and FIGS. 14 to 16
19 is a graph showing the relationship between the phase difference and the intensity distribution of the laser beam applied to the photosensitive drum by the optical scanning device shown in FIG.

21 is a graph showing the intensity distribution shown in FIG. 18 under the same conditions as in FIG.

FIG. 22 illustrates an example of setting elements of an optical scanning device that can remove the influence of a phase difference between adjacent laser beams when using a group of laser beams in which two or more laser beams are collectively collected. Graph.

FIG. 23 is a block diagram of an image control unit of the image forming apparatus shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Multi-beam optical scanning device 3 (Y, M, C, B) ... Light source 3Ya ... Yellow 1st laser 3Yb ... Yellow 2nd laser 3Ma ... Magenta 1st laser 3Mb ... Magenta 2nd laser 3Ca ... Cyan first laser, 3Cb ... Cyan second laser, 3Ba ... Black first laser, 3Bb ... Black second laser, 3Bc ... Black third laser, 3Bd ... Black fourth laser, 5 ... Optical deflection device, 7 (Y , M, C, B) ... Pre-deflection optical system 9 (Y, M, C, B) ... Finite focus lens 11 (Y, M, C, B) ... Hybrid cylinder lens, 12 (Y, M, C, B) ) ... half mirror (semi-transparent mirror) 13 laser combination mirror unit 15 holding member 17 (Y, M, C, B) plastic cylinder lens 19 (Y, M, C, B) glass cylinder Lens, 23 ... horizontal synchronization detector 25: mirror for horizontal synchronization, 30: optical system after deflection, 30a: first imaging lens, 30b: second imaging lens, 33 (Y, M, C, B): first folding mirror, 35 (Y, M, C) ... second folding mirror, 37 (Y, M, C) ... third folding mirror, 39 (Y, M, C, B) ... dustproof glass, 41 (Y, M, C) C) Mirror fixing part 43 (Y, M, C) Mirror holding plate spring 45 (Y, M, C) Projection 47 (Y, M, C) Set screw 50 (Y, M, C) C, B) ... image forming section, 52 ... conveyor belt, 54 ... belt drive roller, 56 ... tension roller, 58 (Y, M, C, B) ... photosensitive drum, 60 (Y, M, C, B) ... Charging device, 62 (Y, M, C, B) ... Developing device, 64 (Y, M, C, B) ... Transfer device, 66 (Y, M, C, B) ... Clear , 68 (Y, M, C, B) ... static eliminator, 70 ... paper cassette, 72 ... delivery roller, 74 ... registration roller, 76 ... suction roller, 78 ... registration sensor, 80 ... registration sensor, 82 ... conveyor belt Cleaner, 84: Fixing device, 100: Image forming device, 101: Main control device, 102: RAM, 103: Non-volatile memory, 110: Image control unit, 111: Image control CPU, 112: Bus line, 113: Timing control Section, 114 (Y, M, C, B) ... image memory, 115 (Y, M, C, B) ... data control section, 116 (Y, M, C, B) ... laser drive section, 118 (Y, M, C, B) M, C, B) ... timing setting device, 121 ... horizontal synchronization signal generation circuit, P ... paper.

[Procedure amendment]

[Submission date] December 11, 2000 (200.12.
11)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

(Equation 1) An optical scanning device characterized by satisfying the following .

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

[0015]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned problems, and has a structure of ΔN _i (N ₁ + N ₂ +...)
+ N _M) (M is an integer of 2 or more and, and an integer of 1 or more) of light sources each of N _i, the light emitted from the plurality of light sources, the sub-scanning direction in order to converge in the sub scanning direction M optical members having a positive power applied thereto, M-1 reflecting mirrors for reflecting M light groups from the M optical members so as to substantially overlap in the first direction, And a deflecting means having a rotatable reflecting surface for deflecting light in a predetermined direction, and を_i lights deflected by the deflecting means on a predetermined image plane. A second optical means including a lens having a function of forming an image so as to scan at a constant speed and correcting a surface tilt of the deflecting means, wherein M light carriers are provided on M image carriers. the optical scanning unit that irradiates the
The second optical means and the image carrier are arranged in the optical path, and
Separating mirrors arranged to separate each light group
Having a separating mirror disposed closest to the second optical means.
Is located near the last lens surface of the second optical means.
Is the distance between the optical axis and the end of the scan line of the system of the second optical means L _1, the system of the optical axis and the other end of the scanning lines of said second optical means L _m When the distance between L and L _max is the distance in the direction parallel to the optical axis of the system between the scanning lines at both ends,
The optical path length L ₀ between the final lens surface and the image plane is (ΔL _max + L _m + L ₁ ) / l. 8> L ₀ L _0> is to provide an optical scanning device, characterized in that in the _{(ΔL max + L m + L} 1) / 2 in the range.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

Further, the present invention provides a method of calculating ΔN _i (N ₁ + N ₂ +
··· + N _{M) (M} is an integer of 2 or more, and the integer of 1 or more) of light sources each of N _i, the light emitted from the plurality of light sources, in order to converge in the sub scanning direction M sets of optical members to which positive power is given in the sub-scanning direction, and M-1 combining reflections that reflect M light groups from the M sets of optical members so as to substantially overlap in the first direction. A first optical means including a mirror, and a reflective surface rotatably formed;
A deflecting means for deflecting light in a predetermined direction, and a function of forming an image of the _i light beams deflected by the deflecting means so as to scan at a constant speed on a predetermined image plane, and correcting a surface tilt of the deflecting means. a second optical means including a lens having a having a said first
Incident angle of light on the lens in the second optical means and
The position is tilted with respect to the optical axis of the lens and decentered
M sets that have passed and given a positive power in the sub-scanning direction
The optical axis of the optical member is relative to the optical axis of the second optical means.
Eccentric and inclined with respect to the sub-scanning direction;
Of light to M sets of optical members given positive power in the
The incident angle and position are tilted with respect to the optical axis of the optical
The optical scanning device is characterized in that the light passes through the optical scanning device with eccentricity .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

Furthermore, the present invention includes a light source, the light emitted from the front Symbol light source, a light Faculty member positive power is applied to the sub-scanning direction in order to converge in the sub-scanning direction, the First optical means, and a rotatable reflecting surface,
A deflecting means for deflecting the light in a predetermined direction, and a lens having a function of forming an image of the light deflected by the deflecting means so that the light is scanned on a predetermined image plane at a constant speed, and correcting the tilt of the deflecting means. And second optical means, the second optical means comprising:
The angle of incidence and the position of the light on the lens
Incline with respect to the optical axis of the lens of
Optical axis of optical member to which positive power is given in the sub-scanning direction
Is in the sub-scanning direction with respect to the optical axis of the second optical means.
Eccentric and inclined, with positive power in the sub-scanning direction.
Angle and position of light on M sets of optical members given by
Is tilted with respect to the optical axis of the optical member, and
There is provided an optical scanning apparatus characterized by excessive to.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

Still further, the present invention provides a method using ΔN _i (N ₁ +
N ₂ + ... + N _M ) (M is an integer of 1 or more and N _i
Is an integer of 1 or more , at least one of which is an integer of 3 or more )
And a plurality of finite focus lenses and collimator lenses that convert light emitted from the respective ΣN _i light sources into convergent light or parallel light, and any one of the plurality of finite focus lenses and collimator lenses was converted into convergent light or collimated light, respectively N _i
Light is reflected or transmitted so as to substantially overlap in the first direction
And combine them into M light groups. (N _i -1) translucent
A mirror, M sets of optical members provided with positive power only in the sub-scanning direction to further converge the M groups of light in the sub-scanning direction, and M light groups from the M sets of optical members And a first optical unit including M-1 combining reflecting mirrors for reflecting the light so as to substantially overlap in the first direction, and a rotatable reflecting surface, so that light is reflected in a predetermined direction. A deflecting means for deflecting, and a lens having a function of forming an image of the _{ｉ i} light beams deflected by the deflecting means so as to scan at a constant speed on a predetermined image plane, and correcting a surface tilt of the deflecting means. And the number of times each light passes through each of the translucent mirrors.
It is an object to provide an optical scanning device characterized by being performed once or less .

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

Still further, the present invention provides a method using ΔN _i (N ₁ +
N ₂ + ... + N _M ) (M is an integer of 1 or more and N _i
Even without least one light source for an integer of 2 or more) of the light emitted from the plurality <br/> of light sources, positive power is applied to the sub-scanning direction in order to converge in the sub scanning direction A first optical means including: M sets of optical members; and M-1 combining reflecting mirrors for reflecting the M light groups from the M sets of optical members so as to substantially overlap in the first direction. A deflecting means having a reflecting surface rotatably formed, and deflecting light in a predetermined direction; and ΣΝ _i lights deflected by the deflecting means are scanned at a constant speed on a predetermined image plane. imaged, the second optical means including a lens having a function of correcting the surface tilt of the deflecting means, before
Horizontal sync detection for defining write position by light recording
And rotate p in the sub-scanning direction scanning pitch and k
When the number of polygon mirrors is
The scanning line is inclined from a right angle direction by δ = tan ⁻¹ (Ni × p × k × φ / (4 × π × W)) , and the horizontal synchronization detector
Connected a place to emit a signal that serves as a reference for horizontal synchronization of
Reference position defined by a straight line or horizontal synchronization detection
Where the signal that provides the reference for horizontal synchronization of the
The straight line at an angle δ with respect to the direction of travel of the image carrier.
It is intended to provide an optical scanning apparatus according to claim is.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

Still further, the present invention provides a method using ΔN _i (N ₁ +
N ₂ + ... + N _M ) (M is an integer of 1 or more and N _i
A light source at least one is an integer of 2 or more), the light emitted from the plurality <br/> of light sources, the positive power in the sub scanning direction in order to converge in the sub scanning direction is given M of A first optical unit including: a set of optical members; and M-1 combining reflecting mirrors that reflect the M light groups from the M sets of optical members so as to substantially overlap in the first direction; rotatably have formed reflecting surface, and a deflecting means for deflecting the light in a predetermined direction, the imaging to scan the Shigumanyu _i book of the light deflected by the deflecting means at a constant speed in a predetermined image plane And second optical means including a lens having a function of correcting surface tilt of the deflecting means, wherein p is an optical pitch in a sub-scanning direction, and α is a sub-scanning direction of light.
E− ² diameter / p, ζ denotes half-life exposure amount of photoconductor / average exposure
Energy and η connect the centers of two adjacent lights
Relative to the peak intensity of one light at the midpoint of the line and
and when,

(Equation 2)

[Procedure amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

An optical scanning device characterized by satisfying
To offer.

[Procedure amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0022

[Correction method] Deleted

[Procedure amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0023

[Correction method] Change

[Correction contents]

Still further, the present invention provides a method using ΔN _i (N ₁ +
N ₂ + ... + N _M ) (M is an integer of 1 or more and N _i
A light source at least one is an integer of 1 or more), the light emitted from the plurality <br/> of light sources, the positive power in the sub scanning direction in order to converge in the sub scanning direction is given M of A first optical unit including: a set of optical members; and M-1 combining reflecting mirrors that reflect the M light groups from the M sets of optical members so as to substantially overlap in the first direction; rotatably have formed reflecting surface, and a deflecting means for deflecting the light in a predetermined direction, the imaging to scan the Shigumanyu _i book of the light deflected by the deflecting means at a constant speed in a predetermined image plane And a second optical unit including a lens having a function of correcting a surface tilt of the deflecting unit, and M sets of positive power given in the sub-scanning direction.
The optical member consists of a single-sided cylinder lens made of glass
When made of a material substantially equivalent to the material of the rear optical system lens
Both face the single-sided cylinder lens of the glass material
Surfaces in the main scanning direction and sub-scanning direction
Consists of a double-sided cylinder lens with equal curvature
There is provided an optical scanning apparatus characterized by that.

[Procedure amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

Still further, the present invention provides a method using ΔN _i (N ₁ +
N ₂ + ... + N _M ) (M is an integer of 2 or more and N _i
And an integer of 1 or more) of light sources each, the light emitted from the plurality of light sources, and M sets of optical members positive power in the sub scanning direction in order to converge in the sub scanning direction is given,
A first optical unit including: M-1 synthesis reflecting mirrors for reflecting M light groups from M sets of optical members so as to substantially overlap in a first direction; and a rotatable member. A deflecting means having a reflecting surface, for deflecting light in a predetermined direction, and ΣΝ _i light beams deflected by the deflecting means for forming an image on a predetermined image plane so as to scan at a constant speed; Second optical means including a lens having a function of correcting surface tilt,
In an optical scanning device that irradiates an image carrier with M light groups, the optical scanning device is disposed in an optical path between the second optical unit and the image carrier.
And the light sources arranged to separate the M light groups, respectively.
Having a separating mirror, which is located closest to the second optical means side
The separation mirror is located near the last lens surface of the second optical unit.
Disposed, and a system of optical axis of the second optical means L ₁ one
The distance between the scanning lines at one end, L _m, to the second optical means
Distance between the optical axis of the system and the scanning line at the other end, and ΔL
_max is the distance in the direction parallel to the optical axis of the system between the scanning lines at both ends.
When the optical path length L ₀ between the final lens surface and the image surface is (ΔL _max + L _m + L ₁ ) / l. 8> L ₀ L _0> is to provide an optical scanning device, characterized in that in the _{(ΔL max + L m + L} 1) / 2 in the range.

[Procedure amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0100

[Correction method] Change

[Correction contents]

FIG. 5 shows that each of the pre-deflection optical systems 7 (Y, M, C and B) shown in FIG. 3 and Tables 1 to 3 is orthogonal to the rotation axis of the reflecting surface of the light deflector 5. Reflection surface 13 of each laser combining mirror in each direction (sub-scanning direction)
The laser beams LY, LM, and LC traveling from Y, 13M, and 13C to the light deflector 5 are shown (LY is LYa and LYb, LM is LMa and LMb, and LC is LCa
And LCb). Here, each beam in FIG.
Dashed lines indicated in LB, LC, LM, LY
Represents the principal ray of each beam. Also,
Dot-dash line between the chief rays of the beam LM and LC
Represents the optical axis of the entire optical system of the four beams of the present application.
are doing.

[Procedure amendment 13]

[Document name to be amended] Statement

[Correction target item name] 0101

[Correction method] Change

[Correction contents]

As is clear from FIG. 5, each of the laser beams LY, LM, LC and LB is applied to the light deflecting device 5.
Are guided to the light deflecting device 5 at mutually different intervals in a direction parallel to the rotation axis of the reflection surface. Here, FIG. 1 and FIG.
As shown in FIG. 5, the laser beam LB is applied to the light deflecting device 5.
The mirror 13B for reflecting the laser beam LC
Mirror 13C and laser for reflecting light to deflection device 5
A mirror 13 for reflecting the beam LM to the light deflecting device 5
It is arranged at a position closer to the light deflecting device 5 than M. Ma
For reflecting the laser beam LC to the light deflector 5
The mirror 13C reflects the laser beam LM to the light deflector 5
Closer to the light deflecting device 5 than the mirror 13M for emitting light
Placed In addition, laser beams LM and LC
Is a plane orthogonal to the rotation axis of the reflecting surface of the light deflecting device 5 and including the center of the reflecting surface in the sub-scanning direction, that is, asymmetrically with respect to the surface including the optical axis of the optical scanning device 1. It is guided to each reflecting surface of the device 5. The laser beams LY, LM, LC and LB on the respective reflecting surfaces of the light deflecting device 5
The distance between the chief rays is 2.26 mm between LY and LM, 1.71 mm between LM and LC, and L
1.45 mm between C and LB. Thus, the laser
The beams LY, LM, LC, and LB are respectively deflected by an optical deflecting device 5.
Of the mirrors reflecting to the side, the position closest to the light deflecting device 5
Reflected by the mirror 13B
The principal ray of the light LB and the mirror 13 adjacent to the mirror 13B
The distance of the beam LC reflected by C to the principal ray (1.
45 mm) is applied to the principal ray of the beam LC and the mirror 13C.
A mirror adjacent to the light deflecting device 5 in a direction away from the light deflecting device 5
Distance from the principal ray of beam LM reflected by 13M
(1.7 mm). That is,
The more the beam is reflected by the mirror farther from the light deflecting device 5,
Arrange so that the distance between adjacent beams becomes wider
Have been. This is the beam diameter of multiple beams at the image plane.
In order to adjust the size to the same size, the light deflector 5
The beam diameter of the beam reflected by the
The beam convergence characteristics
In the same case, the closer to the deflection surface, the more
The beam diameter is based on the fact that it becomes smaller.
The mirror used to reflect the smaller beam is
By making the surface smaller, the beam spacing is narrowed,
In turn, the width occupied by the entire beam (all four beams) is reduced.
It is like that.

[Procedure amendment 14]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

The reflection of the beam separated at the position closest to the lens side by the first and second mirrors is approximated by one reflection, and this reflection point is represented by (x, y) = (0, 0). ) And the photoconductor drum is considered to be above the optical axis (above the plane of the paper) (the coordinate system here is different from the coordinate system of other drawings). Further, the point of reflection by the third mirror is (x ₁ , y ₁ ), the coordinates of the image plane are (x ₂ , y ₂ ), and the coordinates of the image plane of the beam passing through only one folding mirror are (x ₃ , Y ₃ ).

[Procedure amendment 15]

[Document name to be amended] Statement

[Correction target item name] 0136

[Correction method] Change

[Correction contents]

Hereinafter, in order to maximize the area S ₁ or the area S ₂ , the angle between the beam reflected by the second mirror and the optical axis of the post-deflection optical system is set to Ψ, and the reflection at the second mirror is performed. Assuming that the distance between the point and the reflection point at the third mirror is l ₁ , y ₁ and x ₁ are, respectively,

(Equation 3)

[Procedure amendment 16]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

[0137]

(Equation 4)

[Procedure amendment 17]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

[0139] The optical path length from the reflection point by the second mirror to the image plane placed and l _2, beam after reflection on the third mirror is perpendicular to the optical axis of the post-deflection optical system (if such and _{S 1} or _{S 2} is approximated to the maximum) placing the coordinates of the image plane and _(x 2, _{y 2) to, x 2 = x 1 (a} -3) y 2 = y 1 + l 2 - It is represented as l ₁ (a-4).

[Procedure amendment 18]

[Document name to be amended] Statement

[Correction target item name] 0140

[Correction method] Change

[Correction contents]

[0140] On the other hand, a beam separated at a position closest to the lens side, when placed between the last the distance of the beam reflected by the first mirror _{y4, x 3 = - (l} 2 -y 4 -y 2 _{) (a-5) y 3} = y 2 (a-6) is satisfied.

[Procedure amendment 19]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

[0142] Incidentally, y ₄ is at least, from being set to a distance that can separate the three beams at a position where the beam does not overlap, as positioned at regular intervals on the image plane of the respective beams, respectively from the image plane optical path length to the separation _{point, l 2, (l 2 -} ((x 2 -x 3) / 3) / 2) _{and, (l 2 - 2 ((} x 2 -x 3) / 3) / 2 ).

[Procedure amendment 20]

[Document name to be amended] Statement

[Correction target item name] 0143

[Correction method] Change

[Correction contents]

On the other hand, assuming that the beam radius on the image plane is ω ₀ , the divergence angle is represented by ξλ / (π ω ₀ ) . This
Here, ξ is a coefficient including the effect of diffraction by the stop of the optical system before deflection . In this case, the spread angle ξλ / π / ω in the ₀
If there is something that blocks the propagation of light, the beam diameter on the image plane will be large.
I'll be nervous. The distance from the image plane to the separation point
Multiplied by the divergence angle gives the beam radius at the separation point
Therefore, at the separation point, the principal ray is
Is the folding mirror side at least for the beam radius.
For those not folded by the return mirror, the main light
Line wraps at least for beam radius at separation location
It must be away from the mirror end. That is, the spread angle
ξλ / π / ω ₀ multiplied by the distance from the image plane to the separation point
The position of the chief ray at that point must be shifted by twice
There is a point. Each separation point has a distance from the image plane
As described above, l ₂ , (l ₂ − ((x ₂ −x ₃ ) / 3))
/ 2) _{and, l 2 - 2 ((x} 2 -x 3) / 3) / 2) der
Therefore, approximate that each chief ray is almost parallel,
Therefore, the distance multiplied by 2ξλ / π / ω ₀ is
It is necessary to secure the chief ray interval at the separation point of 1. this
Therefore, the ray that is separated first and the last
The chief rays of the beam must be separated by the sum of these
There will be. Consider the coordinates of the first separation point as the origin.
Because and e, _{y 4 are, y 4 = ξ2λ / π /} ω 0 (l 2 + (l 2 - ((x 2 -x 3) / 3) / 2) + l 2 - 2 ((x 2 -x 3 ) / 3) / 2) ... (a-9)

[Procedure amendment 21]

[Document name to be amended] Statement

[Correction target item name] 0146

[Correction method] Change

[Correction contents]

The equation (a-9) is expressed by the following equations (a-1) and (a-
2), (a-3), (a-4), (a-5) and (a
−6) Eliminating x ₂ and x ₃ using the equation and solving for x ₄ ,

(Equation 5)

[Procedure amendment 22]

[Document name to be amended] Statement

[Correction target item name] 0148

[Correction method] Change

[Correction contents]

[0148] Here, substituting the (a-10) expression and to (a-1) with no expression (a-6) formula (a-7) expression and (a-8) wherein the _{S 1} and _{S 2} When the smaller value is plotted on the vertical axis, FIG. 11 is obtained. In FIG. 11, １１ =
1.4, l ₂ = 175, λ = 0.0068 and ωo
= 0.025, the horizontal axis represents 横 from -π to π,
The l ₁ to the depth direction axis, and from 0 to 175.

[Procedure amendment 23]

[Document name to be amended] Statement

[Correction target item name] 0150

[Correction method] Change

[Correction contents]

In the following, a solution that gives 0 by differentiating S ₁ with l ₁ is obtained as follows.

(Equation 6)

[Procedure amendment 24]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

[0152] Here, in practice, _{l 2,} the numerical values obtained by adding the final lens surface and the distance of the first folding mirror is a _Lo, approximated to _{l 2 = Lo, (ΔL max} + L M + L ₁ ) / L ₀ ≒ ((2y ₂ + x ₁ −x ₃ ) / l ₂ ) (a-13)

[Procedure amendment 25]

[Document name to be amended] Statement

[Correction target item name] 0154

[Correction method] Change

[Correction contents]

Therefore, the expression (a-13) is not changed to the expression (a-1).
Substituting equations (a-6), (a-10) and (a-11)
Therefore, if x ₁ −x ₃ is eliminated and simplified ,

(Equation 7)

[Procedure amendment 26]

[Document name to be amended] Statement

[Correction target item name] 0156

[Correction method] Change

[Correction contents]

Hereinafter, for λ = 0.0063, which is a combination of ranges that are currently considered to be practicable, ζ is from 1.4142 to 2.8 on the horizontal axis, ωo is 0 on the axis in the depth direction. .02 = to 0.06 (a-1
4) The values of the equation are shown in FIG. Similarly, λ = 0.0008
On the horizontal axis, 軸 is changed from 1.4142 to 2.8,
On the axis in the depth direction, FIG. 13 shows values of the expression (a-14) in which ωo is set to 0.02 to 0.06. These vertical axes
The value is in the range of the value of the expression (a-14), and the expression (a-14)
It can be seen that the value takes a value between 1.8 and 2.

[Procedure amendment 27]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

[0157]From the above, 1.8 <(ΔL
_max + L _M + L ₁ ) / L ₀ ) <2 and L
₀ Is a positive value, given that ₀ Directly to the formula for
Then (ΔL_max+ L_m+ L₁) /1.8> Lo Lo> (ΔL_max+ L_m+ L₁) / 2, the optical performance of the optical scanning device should be maintained.
The distance between photosensitive drums and optical scanning
That the distance between the device and each photoconductor drum can be secured.
In other words, the volume for mounting process-related parts is S₁To
It is acknowledged that it will be maximum.

[Procedure amendment 28]

[Document name to be amended] Statement

[Correction target item name] 0176

[Correction method] Change

[Correction contents]

FIG. 17A shows the polygon mirror 5 of the light deflecting device 5.
In the case where Ν = 4 laser beams deflected by a certain reflecting surface are formed so as to scan at a constant speed on a predetermined image plane, p is a distance between beams in the sub-scanning direction (beam pitch) and k is a multi-plane. When the number of reflection surfaces of the mirror 5a is used, the angle between the scanning line and the direction in which the photosensitive drum is rotated, that is, the amount δ at which the scanning line is inclined with respect to the sub-scanning direction. In addition,
Between the locations where the signal that serves as the reference for horizontal synchronization is output.
The straight line is defined as the reference position.

[Procedure amendment 29]

[Document name to be amended] Statement

[Correction target item name] 0235

[Correction method] Deleted

[Procedure amendment 30]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

Further, according to the optical scanning device of the present invention, p is the pitch of the beam in the sub-scanning direction , α is e- ² diameter / p in the sub-scanning direction of the beam, and ζ is the half-exposure amount /
When the average exposure energy and η are relative intensities to the peak intensity of one beam at the midpoint of the line connecting the centers of two adjacent beams,

(Equation 8)

[Procedure amendment 31]

[Document name to be amended] Statement

[Correction target item name] 0241

[Correction method] Deleted

[Procedure amendment 32]

[Document name to be amended] Statement

[Correction target item name] 0242

[Correction method] Deleted

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/113 H04N 1/04 104A (72) Inventor Masao Yamaguchi 70 Yanagicho, Saiwai-ku, Kawasaki-shi, Kanagawa Pref. In the Toshiba Yanagicho Plant (72) Inventor Yasuyuki Fukudome 70, Yanagicho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture In the Toshiba Yanagimachi Plant

Claims (9)

[Claims] [Claim 1] _{ΣN i (N 1 + N 2} + ··· + N M) (M
And an integer of 2 or more, has a an integer of 1 or more) of light sources each of N _i, the .SIGMA.N _i number of the plurality of finite focal lenses for converting the emitted light into convergent light or collimated light from the respective light sources and Any of the collimator lenses, positive power is given only in the sub-scanning direction to further converge the light converted into convergent light or parallel light by any of the plurality of finite focus lenses and the collimator lens in the sub-scanning direction. A first mirror including: M sets of optical members; and M-1 combining reflecting mirrors for reflecting the M beams from the M sets of optical members so as to substantially overlap in the first direction.
Optical means; a deflecting means having a rotatable reflecting surface for deflecting light in a predetermined direction;
A second optical unit including a lens having a function of forming an image of the _i beams so as to scan at a constant speed on a predetermined image plane and correcting a surface tilt of the deflecting unit; A beam group is incident on the reflecting surface of the deflecting means from one end so that the interval between the beam groups monotonically increases, and the beam group at one end having the smallest interval between the beam groups is the beam deflected by the deflecting device. An optical scanning device, which is incident so as to intersect. (2) ΔN _i (N ₁ + N ₂ +... + N _M ) (M
And an integer of 2 or more, has a an integer of 1 or more) of light sources each of N _i, the .SIGMA.N _i number of the plurality of finite focal lenses for converting the emitted light into convergent light or collimated light from the respective light sources and Any of the collimator lenses, positive power is given only in the sub-scanning direction to further converge the light converted into convergent light or parallel light by any of the plurality of finite focus lenses and the collimator lens in the sub-scanning direction. A first mirror including: M sets of optical members; and M-1 combining reflecting mirrors for reflecting the M beams from the M sets of optical members so as to substantially overlap in the first direction.
And optical means, having a rotatably formed reflecting surface, and a deflecting means for deflecting the light in a predetermined direction, scanning Shigumanyu _i of beams deflected by the deflecting means at a constant speed in a predetermined image plane And a second optical unit including a lens having a function of correcting surface tilt of the deflecting unit, and irradiating the M image carriers with M beam groups. in the scanning device, the distance between the optical axis and the end of the scan line of the system of the second optical means L _1, scan the optical axis and the other end of the system of the second optical means L _m When the distance between the lines and ΔL _max are distances in the direction parallel to the optical axis of the system between the scanning lines at both ends, the final distance Lo between the lens surface and the image surface is (ΔL _max + L _m + L ₁ ) / L. 8> Lo Lo> (ΔL _max + L _m + L ₁ ) / 2. 3. Ni (N1 + N2 +... + NM) (M
Is an integer of 1 or more, and Ni is an integer of 1 or more, and at least one of M or Ni is an integer of 2 or more), and the light emitted from each of the ΣNi light sources is a convergent light. Or any of a plurality of finite focus lenses and collimator lenses that convert to parallel light, and light that has been converted to convergent light or parallel light by any of the plurality of finite focus lenses and collimator lenses, to further converge in the sub-scanning direction. A combination of M sets of optical members to which positive power is given only in the sub-scanning direction and M-1 pieces of M beams from the M sets of optical members are reflected so as to substantially overlap in the first direction. Reflecting mirror for
Optical means; a deflecting means having a rotatable reflecting surface for deflecting light in a predetermined direction; and scanning the 所 定 i beams deflected by the deflecting means at a constant speed on a predetermined image plane. And a second optical unit including a lens having a function of correcting a surface tilt of the deflecting unit. Lt is a distance between a reflection point on the deflecting unit and an image plane, and When W is an effective image area width including an area for detecting a horizontal synchronization signal, an effective field angle φ of a beam deflected by the deflecting means satisfies φ> W / Lt. (4) ΔN _i (N ₁ + N ₂ +... + N _M ) (M
And an integer of 2 or more, has a an integer of 1 or more) of light sources each of N _i, the .SIGMA.N _i number of the plurality of finite focal lenses for converting the emitted light into convergent light or collimated light from the respective light sources and Any of the collimator lenses, positive power is given only in the sub-scanning direction to further converge the light converted into convergent light or parallel light by any of the plurality of finite focus lenses and the collimator lens in the sub-scanning direction. A first mirror including: M sets of optical members; and M-1 combining reflecting mirrors for reflecting the M beams from the M sets of optical members so as to substantially overlap in the first direction.
And optical means, having a rotatably formed reflecting surface, and a deflecting means for deflecting the light in a predetermined direction, scanning Shigumanyu _i of beams deflected by the deflecting means at a constant speed in a predetermined image plane And a second optical unit including a lens having a function of correcting surface tilt of the deflecting unit, and M sets of optical units provided with a positive power only in the sub-scanning direction. An optical scanning device wherein an incident angle and a position of a beam on a member pass eccentrically with respect to an optical axis of the optical member. (5) ΔN _i (N ₁ + N _i +... + N _M ) (M
Is an integer of 1 or more and,, N _i is 1 or more and the light source of at least one is an integer of 3 or more) of the N _i an integer, convergent light or collimated light emitted from the .SIGMA.N _i pieces of each light source and any of the plurality of finite focal lenses and a collimator lens for converting the light, the light converted into convergent light or collimated light by any of the plurality of finite focal lenses and the collimator lens, the N _i pieces each beam first Are reflected or transmitted so as to be substantially overlapped in the direction and are grouped into M beam groups.
_i -1) translucent mirrors, M sets of optical members to which positive power is applied only in the sub-scanning direction to further converge the M groups of beams in the sub-scanning direction, and M sets of optics A first optical unit including: M-1 combining reflecting mirrors for reflecting the M beam groups from the member so as to substantially overlap in the first direction; and a rotatable reflecting surface. and, a deflection means for deflecting the light in a predetermined direction, the beam of Shigumanyu _i present deflected by the deflecting means is imaged to scan at a constant speed in a predetermined image surface, tilt compensation of the deflecting means And a second optical means including a lens having a function of performing the above operation, wherein the number of times each beam passes through the M-1 translucent mirrors is 1 or 0 times. 6. The method of claim 6, wherein ΔN _i (N ₁ + N ₂ +... + N _M ) (M
Is an integer of 1 or more, and at least one of N _i is an integer of 2 or more), and a plurality of finite focal points for converting the light emitted from each of the ΣN _i light sources into convergent light or parallel light. Positive power only in the sub-scanning direction to further converge the light converted into convergent light or parallel light by one of the lens and the collimator lens in any of the plurality of finite focus lenses and the collimator lens in the sub-scanning direction. A first including: a given M sets of optical members; and M-1 combining reflecting mirrors that reflect the M beams from the M sets of optical members so as to substantially overlap in the first direction.
And optical means, having a rotatably formed reflecting surface, and a deflecting means for deflecting the light in a predetermined direction, scanning Shigumanyu _i of beams deflected by the deflecting means at a constant speed in a predetermined image plane And a second optical unit including a lens having a function of correcting the surface tilt of the deflecting unit, where p is the scanning pitch in the sub-scanning direction, and k is the number of rotating polygon mirrors. In this case, the scanning line is inclined from the direction perpendicular to the traveling direction of the image carrier by δ = tan ⁻¹ (N _i × p × k × φ / (4 × π × W)). Optical scanning device. 7. The method according to claim 7, wherein ΔN _i (N ₁ + N ₂ +... + N _M ) (M
Is an integer of 1 or more, and at least one of N _i is an integer of 2 or more), and a plurality of finite focal points for converting the light emitted from each of the ΣN _i light sources into convergent light or parallel light. Positive power only in the sub-scanning direction to further converge the light converted into convergent light or parallel light by one of the lens and the collimator lens in any of the plurality of finite focus lenses and the collimator lens in the sub-scanning direction. A first including: a given M sets of optical members; and M-1 combining reflecting mirrors that reflect the M beams from the M sets of optical members so as to substantially overlap in the first direction.
Optical means; a deflecting means having a rotatable reflecting surface for deflecting light in a predetermined direction;
光学 a second optical means including a lens having a function of forming an image of the _i beams so as to scan the predetermined image plane at a constant speed, and correcting a surface tilt of the deflecting means; scanning direction of the beam pitch, e ^-2 diameter / p in the main scanning direction of the β-beam, the sub-scanning direction of the e ^-2 diameter / p of the α-beam, half decay exposure / average exposure energy of ζ photoreceptor, and Η at the midpoint of the line connecting the centers of two adjacent beams
When the relative intensity with respect to the peak intensity of one beam is: An optical scanning device characterized by satisfying the following. 8. N _i (N ₁ + N ₂ +... + N _M ) (M
Is an integer of 1 or more, and at least one of N _i is an integer of 2 or more), and a plurality of finite focal points for converting the light emitted from each of the ΣN _i light sources into convergent light or parallel light. Positive power only in the sub-scanning direction to further converge the light converted into convergent light or parallel light by one of the lens and the collimator lens in any of the plurality of finite focus lenses and the collimator lens in the sub-scanning direction. A first including: a given M sets of optical members; and M-1 combining reflecting mirrors that reflect the M beams from the M sets of optical members so as to substantially overlap in the first direction.
Optical means; a deflecting means having a rotatable reflecting surface for deflecting light in a predetermined direction;
結 a second optical unit including a lens having a function of forming an image of the _i beams on a predetermined image plane so as to scan at a constant speed and correcting a surface tilt of the deflecting unit; M sets of optical members to which positive power is given only in the direction are constituted by a single-sided cylinder lens made of glass material and a double-sided cylinder lens substantially equivalent to the material of the post-deflection optical system lens. Optical scanning device. 9. Ni (N1 + N2 +... + NM) (M
Is an integer of 1 or more, and at least one of Ni is an integer of 3 or more), a plurality of finite focal lenses that convert light emitted from each of the ΣNi light sources into convergent light or parallel light, and Any one of the collimator lenses, and the light converted into convergent light or parallel light by any one of the plurality of finite focus lenses and the collimator lenses is reflected or transmitted so that Ni beams substantially overlap each other in the first direction. Combine into M beam groups. (N
i-1) translucent mirrors, M sets of optical members provided with positive power only in the sub-scanning direction to further converge the M groups of beams in the sub-scanning direction, and M sets of optical members A first optical unit including: M-1 combining reflecting mirrors for reflecting the M beam groups from the member so as to substantially overlap in the first direction; and a rotatable reflecting surface. A deflecting means for deflecting light in a predetermined direction; and forming an image of the ΣΝi beams deflected by the deflecting means so as to scan at a constant speed on a predetermined image plane, thereby correcting the tilt of the deflecting means. A second optical means including a lens having a function, wherein the outputs of the Ni light sources of the M group are defined substantially equally.