JPH09184993A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device which can obtain a color image without any color slurring and is reducible in device cost. SOLUTION: This image formation device removes a shift in image formation position due to variance in the external diameter of a photosensitive drum 58 within the common difference by flexible couplings 66a and 66b. Therefore, all of 2×4 laser beams which are used for a single scan can be outputted with the same clock only by making the image formation characteristics of all the laser beams match with each other. Consequently, the cost of a laser driving system built in the image formation device is reduced. Further, color images can be obtained without any color slurring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a plurality of laser beams such as a high speed laser printer or a multi-drum type color copying machine.

[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 copier, a plurality of image forming sections corresponding to color separated color components and a color image forming section A laser exposure device or optical scanning device is used which provides image data corresponding to the component, that is, a plurality of laser beams.

Generally, an optical scanning device includes a semiconductor laser element as a light source, a first lens group for narrowing the beam diameter of a laser beam emitted from the laser element to a predetermined size,
An optical deflecting device that continuously reflects the laser beam narrowed down by the first lens group in the main scanning direction orthogonal to the direction in which the recording medium is conveyed, and a laser beam deflected by the optical deflecting device is set to a predetermined value on the recording medium. It has a second lens group for forming an image at a position. The direction in which the recording medium is conveyed is generally called the sub-scanning direction in contrast to the main scanning direction.

As this type of optical scanning device, an example in which a plurality of optical scanning devices are arranged corresponding to each of the image forming sections and a plurality of laser scanning devices by a number less than the required number of laser beams are used. It is known that a multi-beam optical scanning device formed so as to provide a beam is arranged.

[0005]

However, an error in the position in the main scanning direction of the laser beam scanned from the optical scanning device onto the image surface (photoreceptor surface) causes the error of the beam reflected by the reflecting surface of the optical deflecting device. When it varies depending on the position in the sub-scanning direction, the eccentricity of the photosensitive drum, the outer shape error of the surface, or the like, there is a problem that the image clock length must be changed during one scanning in the main scanning direction by the optical deflector. .

Further, when the multi-beam optical scanning device is used, the image clock lengths corresponding to the plurality of laser beams output by one scanning do not necessarily match, so that Clock variable mechanism that can change the image clock length for each
There is a problem that (oscillation circuit) must be prepared.

This not only increases the cost of the image forming apparatus as a whole, but also complicates the apparatus.

An object of the present invention is to provide an image forming apparatus capable of obtaining a color image without color shift and reducing the cost of the apparatus.

[0009]

The present invention has been made on the basis of the above-mentioned problems, and converts the cross-sectional shape of each light emitted from each of the N light emitting members into a predetermined shape. A first lens, and M combining means for combining the respective lights that have passed through the first lens into M pieces,
The respective lights combined into M pieces by the combining means are
In the state where M sets of second lenses that converge in the direction of and the respective lights that have passed through the second lens are viewed from a third direction orthogonal to the first direction and the second direction.
Aggregating means for aggregating so that it can be regarded as a book;
And a deflection means for deflecting the light emitted from the pre-deflection optical system along the first direction, and a light deflected by the deflection means. The power of the M deflected by the deflecting means has a power defined in accordance with the rotating angle of the reflecting surface so that images are formed at equal intervals regardless of the rotating angle of the reflecting surface of the deflecting means. An optical scanning device having an imaging lens for imaging each light at a predetermined position, and giving substantially the same imaging characteristics to each light, and M sets of light emitted from the optical scanning device. M image carriers, which are arranged corresponding to the respective light beams and hold M sets of images, and the image carriers, respectively, at positions where the M sets of light beams from the optical scanning device are imaged. Also provided is an image forming apparatus characterized by having positioning means for positioning. It is.

Further, according to the present invention, the N first lenses for converting the cross-sectional shape of each light emitted from each of the N light emitting members into a predetermined shape, and the light passing through the first lens. M pieces of combining means for combining the respective lights into M pieces, M sets of second lenses for converging the respective lights combined into the M pieces by the combining means in a first direction, and a second An aggregating unit that aggregates the respective lights that have passed through the lens so that they can be regarded as one when viewed from a third direction orthogonal to the first direction and the second direction, and a first direction. Deflecting means for deflecting the light emitted from the pre-deflection optical system along the first direction, and a deflecting means for deflecting the light deflected by the deflecting means. Images are formed at equal intervals regardless of the rotation angle of the reflecting surface of the deflecting means. As described above, there is power defined according to the rotation angle of the reflecting surface and an imaging characteristic for removing the influence of the reflecting surface of the light reflected by the reflecting surface of the deflecting means, and M deflected by the deflecting means. An optical scanning device having an image forming lens for forming an image of each of the light beams at a predetermined position and giving substantially the same image forming characteristics to the respective light beams, and M emitted from the optical scanning device. M image carriers that are arranged corresponding to the respective sets of light and hold M sets of images, and M sets of light from the optical scanning device are imaged on the respective image carriers. An image forming apparatus, comprising: a positioning unit that positions the position.

Further, according to the present invention, the N first lenses for converting the cross-sectional shape of each light emitted from each of the N light emitting members into a predetermined shape, and the light passing through the first lens. M pieces of combining means for combining the respective lights into M pieces, M sets of second lenses for converging the respective lights combined into the M pieces by the combining means in a first direction, and a second An aggregating unit that aggregates the respective lights that have passed through the lens so that they can be regarded as one when viewed from a third direction orthogonal to the first direction and the second direction, and a first direction. Deflecting means for deflecting the light emitted from the pre-deflection optical system along the first direction, and a deflecting means for deflecting the light deflected by the deflecting means. Images are formed at equal intervals regardless of the rotation angle of the reflecting surface of the deflecting means. Has a power defined according to the rotation angle of the reflecting surface and an imaging characteristic for removing the influence of the reflecting surface of the light reflected by the reflecting surface of the deflecting means, and is deflected by the deflecting means. An optical scanning device having an image forming lens for forming an image of each of the M lights at a predetermined position, and giving substantially the same image forming characteristics to the respective lights, and the light scanning device emitting the light. M image carriers, which are arranged corresponding to the respective M sets of light and hold the M sets of images, and the M sets of light from the optical scanning device are formed on the respective image carriers. Positioning means for positioning at a predetermined position, and N pieces of light emitted from the optical scanning device at predetermined positions on the outer peripheral surfaces of the M image carriers positioned at predetermined positions by the positioning means. Hold the optical scanning device so that it can be accurately imaged. There is provided an image forming apparatus, comprising: the means.

Further, according to the present invention, the cross-sectional shape of each light emitted from each of the N light-emitting members is
N number of first lenses for converting into a predetermined shape, M number of combining means for combining each light passed through the first lens into M pieces, and each of the M pieces combined by the combining means. In a state where M sets of cylindrical lenses that converge the light in the first direction and the respective lights that have passed through the cylindrical lenses are viewed from a third direction orthogonal to the first direction and the second direction. It has an aggregating means for aggregating so as to be regarded as one line, and a reflecting surface rotated along the first direction, and deflects the light emitted from the pre-deflection optical system along the first direction. The deflecting means and the reflecting surface capable of forming images at predetermined image forming positions at equal intervals regardless of the rotation angle of the reflecting surface of the deflecting means when the light deflected by the deflecting means is deflected. Has the power specified according to the rotation angle An optical scanning device having an image forming lens for forming an image of each of the M light beams deflected by the deflecting means at a predetermined position, and giving substantially the same image forming characteristics to the respective light beams. M emitted from the optical scanning device
M image holding members arranged corresponding to each of the sets of light and holding M sets of images, and each of the image holding members,
An image forming apparatus comprising: a positioning unit that positions M sets of light from the optical scanning device to be imaged.

Furthermore, according to the present invention, the cross-sectional shape of each light emitted from each of the N light emitting members is
N number of first lenses for converting into a predetermined shape, M number of combining means for combining each light passed through the first lens into M pieces, and each of the M pieces combined by the combining means. In a state where M sets of cylindrical lenses that converge the light in the first direction and the respective lights that have passed through the cylindrical lenses are viewed from a third direction orthogonal to the first direction and the second direction. It has an aggregating means for aggregating so as to be regarded as one line, and a reflecting surface rotated along the first direction, and deflects the light emitted from the pre-deflection optical system along the first direction. The deflecting means and the reflecting surface capable of forming images at predetermined image forming positions at equal intervals regardless of the rotation angle of the reflecting surface of the deflecting means when the light deflected by the deflecting means is deflected. The power specified according to the rotation angle and the above An image forming lens having an image forming characteristic for removing the influence of the reflecting surface of the light reflected by the reflecting surface of the directing means, and forming an image of each of the M lights deflected by the deflecting means at a predetermined position. And an optical scanning device that gives substantially the same image forming characteristics to the respective lights, and M optical sets that are respectively arranged corresponding to the M sets of light emitted from the optical scanning device. Image holding members for holding the image holding members and positioning means for positioning each of the image holding members at a position where the M sets of light from the optical scanning device are imaged. A forming apparatus is provided.

Further, according to the present invention, the cross-sectional shape of each light emitted from each of the N light emitting members is
N number of first lenses for converting into a predetermined shape, M number of combining means for combining each light passed through the first lens into M pieces, and each of the M pieces combined by the combining means. In a state where M sets of cylindrical lenses that converge the light in the first direction and the respective lights that have passed through the cylindrical lenses are viewed from a third direction orthogonal to the first direction and the second direction. It has an aggregating means for aggregating so as to be regarded as one line, and a reflecting surface rotated along the first direction, and deflects the light emitted from the pre-deflection optical system along the first direction. The deflecting means and the reflecting surface capable of forming images at predetermined image forming positions at equal intervals regardless of the rotation angle of the reflecting surface of the deflecting means when the light deflected by the deflecting means is deflected. The power specified according to the rotation angle and the above An image forming lens having an image forming characteristic for removing the influence of the reflecting surface of the light reflected by the reflecting surface of the directing means, and forming an image of each of the M lights deflected by the deflecting means at a predetermined position. And an optical scanning device that gives substantially the same image forming characteristics to the respective lights, and M optical sets that are respectively arranged corresponding to the M sets of light emitted from the optical scanning device. Of M image holding members for holding the image holding members, and positioning means for positioning each of the image carrying members at a position where the M sets of light from the optical scanning device are imaged, and by this positioning means a predetermined position is set. Holding means for holding the optical scanning device so that each of the N light beams emitted from the optical scanning device can be accurately imaged at a predetermined position on the outer peripheral surface of the M image carriers to be positioned. And an image forming apparatus including: It is intended.

Furthermore, the present invention provides N = 1 to N.
A light source including N laser elements represented by = i, and N finite lenses or collimating lenses that convert each laser beam emitted from each laser element of the light source into convergent light or parallel light. 1 lens group,
The M number of M = 1 to M = j are arranged, and
A combining unit that combines the respective lights that have passed through the respective lenses of the lens group into M lines, and the respective lights from the light sources that are combined into the M lines by this combining unit are converged in the first direction M. A second lens group composed of a pair of cylindrical lenses, and 1 when viewed from a third direction orthogonal to each of the first direction and the second direction of each light that has passed through each of the cylindrical lenses. And a reflecting surface that is rotated about a rotation axis parallel to the third direction,
Dependent on the deflection means for deflecting the light aggregated by the aggregating means along the first direction, and the size of the rotation angle of the reflecting surface of the deflecting means when the light deflected by the deflecting means is deflected. Rather than removing the influence of the reflection surface of the light reflected by the reflection surface of the deflecting means and the power defined corresponding to the rotation angle of the reflection surface, which can form images at predetermined image forming positions at equal intervals. An optical scanning device having an image characteristic, and a third lens group including a lens for forming each of the M light beams deflected by the deflecting means at a predetermined position, and The M image carriers that are arranged corresponding to the M sets of light emitted from the optical scanning device and that hold the M sets of images, and the image carriers are respectively provided by the M image carriers from the optical scanning device. Positioning means for positioning at a position where a set of light is imaged , There is provided an image forming apparatus characterized by having a.

Still further, according to the present invention, N = 1 to N
A light source including N laser elements represented by = i, and N finite lenses or collimating lenses that convert each laser beam emitted from each laser element of the light source into convergent light or parallel light. 1 lens group,
The M number of M = 1 to M = j are arranged, and
A combining unit that combines the respective lights that have passed through the respective lenses of the lens group into M lines, and the respective lights from the light sources that are combined into the M lines by this combining unit are converged in the first direction M. A second lens group composed of a pair of cylindrical lenses, and 1 when viewed from a third direction orthogonal to each of the first direction and the second direction of each light that has passed through each of the cylindrical lenses. And a reflecting surface that is rotated about a rotation axis parallel to the third direction,
Dependent on the deflection means for deflecting the light aggregated by the aggregating means along the first direction, and the size of the rotation angle of the reflecting surface of the deflecting means when the light deflected by the deflecting means is deflected. Rather than removing the influence of the reflection surface of the light reflected by the reflection surface of the deflecting means and the power defined corresponding to the rotation angle of the reflection surface, which can form images at predetermined image forming positions at equal intervals. An optical scanning device having an image characteristic, and a third lens group including a lens for forming each of the M light beams deflected by the deflecting means at a predetermined position, and The M image carriers that are arranged corresponding to the M sets of light emitted from the optical scanning device and that hold the M sets of images, and the image carriers are respectively provided by the M image carriers from the optical scanning device. Positioning means for positioning at a position where a set of light is imaged The N × M lights emitted from the optical scanning device are accurately imaged at predetermined positions on the outer peripheral surfaces of the M image carriers positioned at predetermined positions by the positioning means. As described above, the present invention provides an image forming apparatus characterized by having a holding means for holding the optical scanning device.

[0017]

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 type color image forming apparatus incorporating a multi-color optical scanning device to which the embodiment of the present invention is applied.

In the image forming apparatus 100, color-separated color components supplied by an optical scanning device 1 described later with reference to FIGS. 2 to X, that is, Y = yellow, M = magenta, C =
First to fourth image forming units 50Y, 50M, 5 for forming four images based on four laser beams LY, LM, LC and LB corresponding to cyan and B = black.
It has 0C and 50B.

Each image forming section 50 (Y, M, C and B)
Is accurately fixed to the imaging positions of the four laser beams output from the optical scanning device 1 by frames 40a and 40b (not visible because FIG. 1 is a front sectional view) described later with reference to FIG. To be done.

At a predetermined position of the frames 40a and 40b, an optical scanning device which will be described later with reference to FIGS.
Holding members 42a and 42b for holding a plurality of laser beams emitted from a laser included in the optical scanning device so as to form an image at a predetermined imaging position provided by the optical scanning device.

Each image forming section 50 (Y, M, C and B)
Is the third folding mirror 37Y, 37 of the optical scanning device 1.
50Y below the optical scanning device 1 corresponding to the position where the laser beam L (Y, M, C and B) corresponding to each color component image is emitted via M, 37C and the first folding mirror 33B. , 50M, 50C and 50B are arranged in series in this order.

Below the respective image forming sections 50 (Y, M, C and B), a conveyor belt 5 for conveying the images formed by the respective image forming sections 50 (Y, M, C and B).
2 are arranged.

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

Each image forming section 50 (Y, M, C and B)
Are photosensitive drums 58Y, 58M, 58C and 58B, each of which is formed in a cylindrical drum shape and is rotatable in the direction of the arrow and on which an electrostatic latent image corresponding to image information to be printed is formed. .

The photoconductor drums 58 (Y, M, C and B) are provided at predetermined positions in the non-image forming portion on the outer peripheral surface (surface) of the photoconductor drums 58 (Y, M, C and B). , Laser beams LY, LM, L emitted from the optical scanning device 1
Positions where C and LB are focused and each photosensitive drum 58
Positioning rollers 60 (Y, M, C and B) for aligning with the surface of (Y, M, C and B) are arranged.

Each positioning roller 60 (Y, M, C and B) has a corresponding laser beam LY, L in the circumferential direction of the surface of the corresponding photosensitive drum 58 (Y, M, C and B).
2 across the exposure position where M, LC and LB are irradiated
A total of four drums 58 (Y, M, C and B) are arranged at both ends in the axial direction.

Each positioning roller 60 (Y, M,
C and B) are formed in a substantially hollow cylindrical shape.
In addition, fixed shafts 62a and 62b are penetrated inside the respective positioning rollers 60 arranged at both ends of each photoconductor drum 58 (Y, M, C and B). The fixed shafts 62a and 62b correspond to the frame 4 shown in FIG.
It is bound in place on 0a and 40b.

As a result, the holding member 42 shown in FIG.
By setting the optical scanning device 1 on a and 42b, the outer peripheral surface (front surface) of each photosensitive drum 58 (Y, M, C, and B) and the optical scanning device described later with reference to FIGS. The position where the 2 × 4 laser beams emitted from the optical scanner are imaged by the optical scanning device is exactly matched.

As shown in FIG. 2, the central axes of the respective photosensitive drums 58 (Y, M, C and B) are aligned with the housings (not shown) of the corresponding image forming portions 50 (Y, M, C and B). The fixed bearings 64a and 64b are connected via known flexible couplings 66a and 66b formed to be able to transmit the driving force even when the two shafts do not exist in the same axis.

Further, as is apparent from FIG. 2, the central axis of each photosensitive drum 58 (Y, M, C and B) has a spring 6
8a and 68b allow corresponding positioning roller 60
Is pressed against. As a result, the surface (outer peripheral surface) of each photosensitive drum 58 (Y, M, C and B) is
It is pressed against the corresponding positioning roller 60. Therefore, the surfaces of the photoconductor drums 58 (Y, M, C and B) and the laser beams LY, LM, LC and LB output from the optical scanning device 1 described later with reference to FIGS. 3 to 6 are focused. Position is exactly matched.

Referring again to FIG. 1, each photosensitive drum 5
8 (Y, M, C and B) at predetermined positions, charging devices 70Y, 70M and 70C for providing a predetermined surface potential to the surface of each photosensitive drum 58 (Y, M, C and B).
And 70B, developing devices 72Y, 72M, 7 for developing the electrostatic latent image formed on the surface of each photoconductor drum 58 (Y, M, C and B) with toner given a corresponding color.
2C and 72B, conveying belt 52 to photosensitive drum 58
A recording sheet which is opposed to the photoconductor drum 58 (Y, M, C and B) in a state of being interposed between (Y, M, C and B) and is conveyed by the conveyance belt 52 or the conveyance belt 52. The transfer devices 74Y, 74M, which transfer the toner images on the respective photosensitive drums 58 (Y, M, C, and B) to P,
A cleaner for removing the residual toner remaining on the surface of the photoconductor drum 58 (Y, M, C and B) after the toner image is transferred via the 74C and 74B and the transfer device 74 (Y, M, C and B). 76Y, 76M, 76C and 76
B and residual potentials remaining on the respective photosensitive drums 58 (Y, M, C and B) after the toner image is transferred via the transfer device 74 (Y, M, C and B) are removed. The static eliminators 78Y, 78M, 78C and 78B
The photoconductor drums 58 (Y, M, C and B) are arranged in order along the rotating direction. Each of the developing devices 72 (Y, M, C and B) has a corresponding photoconductor drum 58 (Y, M, C, B) via a pressure contact mechanism (not shown).
The outer peripheral surfaces of M, C and B) are opposed to each other at a predetermined interval.
Further, each mirror 37Y, 37M, 37C of the optical scanning device 1
And laser beams LY, L guided by 33B
M, LC and LB are each charging devices 70
(Y, M, C and B) and each developing device 72 (Y, M, C)
And B). That is, each mirror 3
The laser beams LY, LM, LC, and LB guided to the photoconductor drums 58 (Y, M, C, and B) by the 7Y, 37M, 37C, and 33B are as viewed from the sectional direction shown in FIG. Thus, an image is formed between the two positioning rollers 60 arranged in the circumferential direction of each photosensitive drum.

Below the conveyor belt 52, a paper cassette 80 for accommodating a recording medium, that is, a paper P for transferring an image formed by each image forming section 50 (Y, M, C and B) is arranged. ing.

At one end of the paper cassette 80 and in the vicinity of the tension roller 54, a half-moon roller (feeding roller) 82 for taking out the paper P stored in the paper cassette 80 one by one (from the top) is arranged. Has been done. Between the delivery roller 82 and the tension roller 54,
The leading edge of one sheet of paper P taken out from the cassette 80 and each image forming section 50 (Y, M, C and B), especially 50B
Thus, a registration roller 84 for aligning each of the photoconductor drums 58 (Y, M, C and B), particularly, the tip of the toner image formed on 58B is arranged.

Registration roller 84 and first image forming section 5
0Y, in the vicinity of the tension roller 54, substantially with the conveyor belt 52 interposed therebetween.
A suction roller 86 that provides a predetermined electrostatic suction force to one sheet of paper P conveyed at a predetermined timing via the registration roller 82 is arranged on the outer periphery of the sheet. The axis of the suction roller 86 and the tension roller 54 are arranged in parallel.

At one end of the conveyor belt 52, in the vicinity of the belt drive roller 56, and substantially on the outer periphery of the belt drive roller 56 with the conveyor belt 52 interposed therebetween, the conveyor belt 52 is provided.
Alternatively, registration sensors 88 and 90 for detecting the position of the image formed on the sheet P conveyed by the conveyor belt are arranged at a predetermined distance in the axial direction of the belt drive roller 56 (FIG. 1). Is a front sectional view, so only the rear sensor 90 is shown).

On the conveyor belt 52 corresponding to the outer circumference of the belt drive roller 56, a conveyor belt cleaner 92 for removing toner adhering to the conveyor belt 52 or paper dust of the paper P is arranged.

Paper P conveyed through the conveyor belt 52
A fixing device 94 that fixes the toner image transferred onto the sheet P to the sheet P is disposed in the direction in which the sheet is separated from the tension roller 56 and further conveyed.

FIG. 3 shows a multi-beam optical scanning device used in the image forming apparatus shown in FIGS. 1 and 2. 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 that form an image for each color component corresponding to B and B are used, similarly, by adding Y, M, C, and B to each reference symbol, The image data for each and the corresponding device are identified.

As shown in FIG. 3, in the multi-beam optical scanning device 1, a laser beam emitted from a laser element as a light source is arranged on an image plane arranged at a predetermined position, that is, the first to the third shown in FIG. Fourth image forming unit 50Y, 50
M, 50C and 50B photoconductor drums 58Y and 58
It has a single optical deflecting device 5 as a deflecting means for deflecting each of M, 58C and 58B toward a predetermined position at a predetermined linear velocity. Note that, hereinafter, the direction in which the laser beam is deflected by the optical deflector 5 is referred to as the main scanning direction. In addition, the direction orthogonal to the main scanning direction, in which the respective photosensitive drums 58 of the image forming apparatus 100 are rotated, that is, the direction in which the sheet fed from the sheet cassette 80 of the image forming apparatus 100 is conveyed, Compared to the main scanning direction, it is called the sub scanning direction.

The optical scanning device 1 includes Ni (i is a positive integer)
_{First to fourth} laser beams including two laser elements (N ₁ = N ₂ = N ₃ = N ₄ = 2) satisfying the above conditions and generating four laser beams corresponding to the image data color-separated into color components. Light sources 3Y, 3M, 3C and 3B (M and M are positive integers, here 4).

Each of the first to fourth light sources 3Y, 3M, 3C and 3B emits a laser beam corresponding to Y, that is, a yellow image, and a first yellow laser 3Ya.
And the second yellow laser 3Yb, M, ie, the first magenta laser 3Ma and the second magenta laser 3Mb, C, which emit a laser beam corresponding to a magenta image, ie, the first cyan laser 3Ca and cyan which emit a laser beam corresponding to a cyan image. It has a second laser 3Cb, a black first laser 3Ba and a black second laser 3Bb for emitting a laser beam corresponding to B, ie, a black (black) image. Note that each of the laser elements emits a first to fourth laser beam L
Ya and LYb, LMa and LMb, LCa and LCb, and LBa and LBb are emitted and guided toward the optical deflector 5 at the subsequent stage.

The optical deflector 5 comprises a polygon mirror body 5a having a plurality of, for example, eight plane reflecting mirrors (planes) arranged in a regular polygonal shape, and a polygon mirror body 5a at a predetermined speed in the main scanning direction. It has a motor (not shown) for rotating. The polygon mirror body 5a is made 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, on the cut surface cut out along the sub-scanning direction,
For example, it is provided by depositing a surface protective layer such as silicon dioxide.

Each laser element 3Ya, 3Ma, 3
Between Ca and 3Ba and the light deflecting device 5, four sets of deflections for adjusting the sectional beam spot shapes of the laser beams LYa, LMa, LCa and LBa from the respective light sources 3Ya, 3Ma, 3Ca and 3Ba into predetermined shapes. A front optical system 7 (Y, M, C and B) is arranged.

Here, the laser beam LYa traveling from the yellow first laser 3Ya toward the optical deflector 5 is represented as
The pre-deflection optical system 7 will be described.

The divergent laser beam emitted from the first yellow laser 3Ya is given a predetermined convergence by the finite focus lens 9Ya, and then the stop 10Ya
The cross-sectional beam shape is adjusted to a predetermined shape. Aperture 10Y
The laser beam LYa that has passed through a is given a predetermined converging property only in the sub-scanning direction via the hybrid cylinder lens 11Y, and the optical deflecting device 5
Will be guided to.

A half mirror 12Y is provided between the finite focus lens 9Ya and the hybrid cylinder lens 11Y.
Finite focus lens 9Ya and hybrid cylinder lens 1
It is inserted at a predetermined angle with respect to the optical axis between 1Y.

On the surface of the half mirror 12Y opposite to the surface on which the laser beam LYa from the first yellow laser 3Ya is incident, a predetermined beam in the sub-scanning direction with respect to the laser beam LYa from the first yellow laser 3Ya. The laser beam LYb from the yellow second laser 3Yb arranged so as to be able to provide the space is
The laser beam LYa is incident on the laser beam LYa at predetermined beam intervals in the sub-scanning direction.

The respective laser beams LYa and L are combined into a substantially single laser beam having a predetermined beam interval in the sub-scanning direction via the half mirror 12Y.
As shown in FIG. 9, Yb passes through the laser synthesizing mirror unit 13 and is guided to the optical deflecting device 5.

Similarly, in relation to M, that is, magenta, a finite focus lens 9Ma and a diaphragm 1 are provided between the magenta first laser 3Ma and the laser synthesizing mirror unit 13.
0 Ma, the hybrid cylinder lens 11M, the half mirror 12M, the magenta second laser 3Mb, the finite focus lens 9Mb and the diaphragm 10Mb, that is, C, ie, cyan, between the cyan first laser 3Ca and the laser synthesizing mirror unit 13, Finite focus lens 9Ca, diaphragm 10
Ca, hybrid cylinder lens 11C, half mirror 12C, cyan second laser 3Cb, finite focus lens 9
Cb and diaphragm 10Cb, and in relation to B, that is, black, a finite focus lens 9Ba and diaphragm 10B are provided between the black first laser 3Ba and the laser combining mirror unit 13.
a, the hybrid cylinder lens 11B, the half mirror 12B, the second black laser 3Bb, the finite focus lens 9Bb, and the diaphragm 10Bb are respectively arranged at predetermined positions. 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, for example, held by an aluminum alloy or the like. The member 15 is integrally held.

Between the optical deflector 5 and the image plane, the first and second image forming lenses 30a for imparting predetermined optical characteristics to the laser beam deflected in the predetermined direction by the reflecting surface of the optical deflector 5 are provided. And a pair of post-deflection optical systems 30 composed of 30b and the combined laser beams L (Y, Y, emitted from the second imaging lens 30b of the post-deflection optical system 30).
M, C and B) individual beams to reach a predetermined position before the area in which the image is written, and only one horizontal sync detector 23 and post-deflection optics 21 and horizontal 2 × 4 combined laser beams L (Y, M, which are arranged between the synchronous detector 23 and passed through at least one lens described later in the post-deflection optical system 21).
Only one set of mirrors 25 for horizontal synchronization for reflecting a part of C and B) toward the horizontal synchronization detector 23 in different directions in the main and sub scanning directions is disposed.

FIG. 4 shows the half mirror 1 of the pre-deflection optical system 7.
FIG. 4 is a partial cross-sectional view of an optical path between a light source 2 and a reflection surface of a light deflecting device 5 viewed from a sub-scanning direction with a folding mirror and the like omitted. In FIG. 4, one laser beam L
Only the optical component for Y (LYa) is shown as a representative.

Finite focus lens 9 (Y, M, C and B)
a and 9 (Y, M, C and B) b have
A single lens in which a UV-curing plastic aspherical lens (not shown) is bonded to the aspherical glass lens or the spherical glass lens is used.

The hybrid cylinder lens 11Y includes a PMMA cylinder lens 17Y and a glass cylinder lens 19Y which have substantially the same curvature in the sub-scanning direction.
And is formed by. A surface of the PMMA cylinder lens 17Y that contacts air is formed to be substantially flat.

Further, the hybrid cylinder lens 11Y
Are the cylinder lens 17Y and the cylinder lens 19Y, and the exit surface of the cylinder lens 17Y and the cylinder lens 1
It is integrally formed by adhesion with the incident surface of 9Y or by being pressed against a positioning member (not shown) from a predetermined direction. In the hybrid cylinder lens 11Y, the cylinder lens 17Y may be integrally formed on the entrance surface of the cylinder lens 19Y.

The plastic cylinder lens 17Y is made of, for example, PMMA (polymethylmethacryl). The glass cylinder lens 19Y is, for example,
It is formed of a material such as TaSF21. Further, each of the cylinder lenses 17Y and 19Y is fixed to the finite focus lens 9 at an accurate interval by the positioning portion integrally formed with the holding member 15.

Tables 1 to 3 below show the pre-deflection optical system 7.
The optical numerical data of is shown.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3] As is clear from Tables 1 to 3, the finite focus lens 9 and the hybrid cylinder lens 11 corresponding to the respective color components are independent of each other with respect to any color component.
The same lens is used. The pre-deflection optical system 7Y corresponding to Y (yellow) and the pre-deflection optical system 7B corresponding to B (black) have substantially the same lens arrangement. The pre-deflection optical system 7M corresponding to M (magenta) and the pre-deflection optical system 7C corresponding to C (cyan) have a finite focus lens 9 and a hybrid cylinder compared to the pre-deflection optical systems 7Y and 7B. The distance from the lens 11 is widened.

FIG. 5 shows each of the pre-deflection optical systems 7 (Y, M, C and B) shown in FIG. 4 and Table 1 in a direction orthogonal to the rotation axis of the reflection surface of the optical deflector 5 (sub-optical axis). (Scanning direction)
Reflecting surfaces 13Y and 13M of the respective laser synthesizing mirrors
And the laser beam L from 13C to the optical deflector 5
Y, LM and LC are shown (LY is LYa and LYb as shown in FIG. 7, and similarly LM is LMa and L
Mb and LC consist of LCa and LCb).

As is apparent from FIG. 5, the respective laser beams LY, LM, LC and LB are transmitted by the optical deflector 5.
Are guided to the optical deflecting device 5 at mutually different intervals in a direction parallel to the rotation axis of the reflecting surface of. The laser beam L
M and LC are asymmetrical with respect to a surface that is orthogonal to the rotation axis of the reflection surface of the optical deflector 5 and that includes the center of the reflection surface in the sub-scanning direction, that is, a surface that includes the optical axis of the system of the optical scanning device 1. , Is guided to each reflecting surface of the light deflecting device 5. The laser beams LY, LM, L on the reflecting surfaces of the optical deflector 5 are
The distance between C and LB is 3.20 m between LY and LM.
m, 2.70 mm between LM and LC, and 2.30 mm between LC and LB. Further, the cross-sectional shapes of the respective laser beams LY, LM, LC and LB are converged in the sub-scanning direction for the purpose of reducing the influence of surface tilt of each reflecting surface of the optical deflector 5.

By the way, as shown in FIG. 5, the distance between the laser beams LC and LB is set to 2.30 mm, which is very narrow on each reflecting surface of the optical deflector 5. Therefore, a laser synthesizing mirror unit 1 described later with reference to FIG.
3 mirror 3B shape error or mirror holding unit 13
The shape error of γ or the mirror 13
When the mirror 13B is slightly shifted toward the laser beam LC and fixed due to an attachment error when fixing B, a part of the laser beam LC may be blocked by the mirror 13B.

When a part of the laser beam LC is blocked,
It is obvious that the intensity of the laser beam guided to the image forming unit 58 is reduced as compared with the intensity of other laser beams, and the color reproducibility of the color obtained by superposing the toners of the respective colors is deteriorated. Needless to say, again, mirror 1
When a part of the laser beam LC is irregularly reflected by the one end of 3B, undesired ghost light is generated.

Therefore, the base 13a of the laser synthesizing mirror unit 13, which will be described later with reference to FIG. 9, and the holding portions 13α, 13β and 13γ are integrally formed of a material having a small coefficient of thermal expansion such as an aluminum alloy.

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

As shown in FIG. 6, the post-deflection optical system 30
Between the second image-forming lens 30b of FIG.
2 × 4 laser beams L (Y, M,
C and B) are folded toward the image plane by first folding mirrors 33 (Y, M, C and B), and laser beams LY, LM and LC folded by the first folding mirrors 33Y, 33M and 33C are Further, second and third folding mirrors 35Y, 35M and 35C and 37Y, 37M and 37C to be folded are arranged. As is clear from FIG. 6, the laser beam LB corresponding to the B (black) image is guided by the first folding mirror 33B to the image plane without passing through other mirrors. .

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 respectively scan the light. Intermediate base 1a of device 1
For example, it is fixed to a plurality of fixing members (not shown) formed by integral molding by adhesion or the like.

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

Third folding mirrors 37Y, 37M, 3
7C and the first folding mirror 33B and the image plane, and 2 × 4 = 8 laser beams L (Y, M, C) reflected via the respective mirrors 33B, 37Y, 37M and 37C. Further, dust-proof glass 39 (Y, M, C and B) for dust-proofing the inside of the optical scanning device 1 is further arranged at a position where the optical scanning device 1 emits B and B).

FIG. 7 shows the first to fourth combined laser beams L (Y, M, C and B) passing between the optical deflector 5 shown in FIG. 6 and the image plane and the optical scanning. FIG. 6 is an optical path diagram showing a relationship with the optical axis of the system in the sub-scanning direction of the apparatus 1.

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 light deflecting device 5 are respectively reflected by the first Between the imaging lens 30a and the second imaging lens 30b, in the sub-scanning direction, the optical axis of the system is intersected and guided to the image plane.

FIG. 8 shows in detail the arrangement of laser elements used in the pre-deflection optical system shown in FIG.

As already described with reference to FIG. 3, each of the first to fourth light sources 3 (Y, M, C and B) has a set of two yellow first lasers 3Ya and two yellow second lasers. 3Yb, a magenta first laser 3Ma and a magenta second laser 3Mb, a cyan first laser 3Ca and a cyan second laser 3Cb, and a black first laser 3Ba and a black second laser 3Bb. In addition,
The respective lasers forming a pair are arranged at a distance in the sub-scanning direction by a predetermined distance corresponding to the beam distance on the image plane described later. Further, a pair corresponding to each pair, that is, a color component is a sub-scanning direction distance defined in advance corresponding to each reflection area of the laser synthesizing mirror block 13 described below with reference to FIG. They are arranged in four layers when viewed from above.

In FIG. 9, the first through fourth, which are 2 × 4, are shown.
The laser synthesizing mirror unit 13 that guides the laser beams LY, LM, LC and LB of 1 to each reflecting surface of the optical deflecting device 5 as one bundle of laser beams is shown.

The laser synthesizing mirror unit 13 is provided with the first to third mirrors 13M and 13C, which are arranged by a number smaller by “1” than the number of image-formable color components (the number of color-separated colors) M. And 13B and the first to third holding mirrors 13M, 13C and 13B, respectively.
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.

By the way, the light source 3Y, that is, the yellow first
The laser beam LY emitted from the laser 3Ya and the yellow second laser 3Yb is directly guided to each reflecting surface of the light deflecting device 5, as already described. In this case, the laser beam LY emits light from the base 13 rather than the optical axis of the system of the optical scanning device 1.
The mirror 1 fixed to the a side, that is, the first holding portion 13α
It is passed between 3M and the base 13a.

Next, the laser beams LM, LC and LB reflected by the respective mirrors 13M, 13C and 13B of the composite mirror unit 13 and guided to the light deflecting device 5 and the lasers directly guided to the light deflecting device 5. The intensity (light amount) of the beam LY will be described.

According to the laser synthesizing mirror unit 13 shown in FIG. 9, the respective laser beams LM and LC are
And LB are reflected by ordinary mirrors (13M, 13C and 13B) in a region where the laser beams LM, LC and LB at the preceding stage incident on the respective reflecting surfaces of the light deflector 5 are separated in the sub-scanning direction. . Therefore, each reflective surface
Each laser beam L (M, M, which is reflected by (13M, 13C and 13B) and then supplied toward the polygon mirror body 5a.
The amount of light of C and B) can be maintained at approximately 90% or more of the amount of light emitted from the finite focus lens 9. Not only can the output of each laser element be reduced, but aberration due to the inclined parallel plate does not occur, so that the aberration of the light reaching the image plane can be uniformly corrected. As a result, each laser beam can be narrowed down, and as a result, high definition can be dealt with. The laser element 3Y corresponding to Y (yellow) is directly guided to each reflecting surface of the optical deflecting device 5 without being involved in any one of the combining mirrors 13, so that the output capacitance of the laser is reduced. Not only can be reduced, but also the mirror (13M, 13M) that may occur in other laser beams reflected by the synthetic mirror
The error of the incident angle on each reflecting surface due to the reflection at C and 13B) is removed.

FIG. 10 shows the folding mirror for horizontal synchronization in detail.

According to FIG. 10, the folding mirror 25 for horizontal synchronization has the respective combined laser beams LY and L.
In order to reflect M, LC and LB to the horizontal sync detector 23 at different timings in the main scanning direction and to provide substantially the same height on the horizontal sync detector 23 in the sub scanning direction, First to fourth folding mirror surfaces 25Y, 25M, 25C and 25B formed at different angles in the scanning direction and the sub-scanning direction, and respective mirrors 25 (Y, M, C and B) are integrally held. It has a mirror block 25a.

The mirror block 25a is made of, for example, glass-filled 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.

In this way, not only can the respective laser beams LY, LM, LC and LB deflected by the optical deflector 5 be made incident on the same detection position of one detector 23, For example, it is possible to eliminate the shift of the horizontal synchronizing signal due to the sensitivity or position shift of each detector, which is a problem when a plurality of detectors are arranged. Note that the horizontal synchronization detector 23 uses the horizontal synchronization folding mirror 25 to control the laser beams LY and L per line in the main scanning direction.
Needless to say, M, LC and LB are incident four times in total, and two horizontal synchronization signals are obtained for one beam. Further, the mirror block 25a is designed so that one mirror surface of the mold can be created by cutting from the block, and is devised so that it can be removed from the mold without requiring an undercut.

FIG. 11 shows the third folding mirror 37Y,
It is a schematic perspective view which shows the support mechanism of 37M and 37C.

According to FIG. 11, 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 and fixed portions at predetermined positions of the intermediate base 1a of the optical scanning device 1, respectively. It is held by the mirror pressing leaf spring 43 (Y, M and C) which is opposed to the portion 41 (Y, M and C) with the corresponding mirror interposed therebetween.

A pair of fixed portions 41 (Y, M and C) are formed at both ends (main scanning direction) of each mirror 37 (Y, M and C). Two protrusions 45 (Y, M, and C) for holding the mirror 37 (Y, M, and C) at two points are formed on one fixed portion 41 (Y, M, and C), respectively. . The two projections 45 (Y, M
And C) are ribs 46, as shown by the dotted lines in FIG.
(Y, M and C). The remaining fixing portion 41 (Y, M and C) supports a mirror held by a projection 45 (Y, M and C) so as to be movable in a direction perpendicular to the mirror surface or along the optical axis. Set screw 47
(Y, M and C).

As shown in FIG. 11, each mirror 37 (Y, M and C) has a projection 45 when the set screw 47 (Y, M and C) is moved in a predetermined direction.
With (Y, M and C) as fulcrums, the mirror is moved in the direction perpendicular to the mirror surface or in the optical axis direction.

Next, the optical characteristics between the hybrid cylinder lens 11 and the post-deflection optical system 30 will be described in detail.

Post-deflection optical system 30 ie the first of the two-sheet set
Since the second imaging lenses 30a and 30b are formed of plastic, for example, PMMA, the ambient temperature changes, for example, between 0 ° C and 50 ° C, so that the refractive index n becomes 1.4876 to 1.4
It is known to change up to 789. In this case, the imaging plane on which the laser beams that have 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 ± 12 mm. .

Therefore, as already described with reference to FIG. 4 and Tables 1 to 3, the pre-deflection optical system 7 is made of the same material as the lens used in the post-deflection optical system 30. By incorporating the lens with the curvature of the lens optimized, the variation of the image plane caused by the variation of the refractive index n due to the temperature change is ± 0.5 mm (hereinafter referred to as [mm]). It can be suppressed to a certain degree.

As a result, the temperature of the lens included in the post-deflection optical system is higher than that of a general conventional optical system using a plastic lens in the post-deflection optical system and a glass lens in the pre-deflection optical system. It is possible to reduce the chromatic aberration in the sub-scanning direction that occurs due to the change in the refractive index due to the change.

By the way, as shown in FIG. 3, the image surface, that is, the surface of the photoconductor drum 58 (Y, M, C, and B) may be displaced due to the positional deviation of the photoconductor drum itself or the variation in the tolerance of the outer diameter. When the position is different from the predetermined (design) position, the distance between the laser beam output from the optical scanning device 1 and the photosensitive drum located at a position different from the design position varies in the optical axis direction. Will be done. in this case,
The position of the laser beam output in one scan changes in the main scanning direction. This is visually recognized as a positional deviation in the main scanning direction with respect to the image formed on the remaining photosensitive drums, that is, a color deviation. In general, the limit point where the color shift cannot be visually confirmed is 1.5 times the laser beam interval.

Here, the deviation of the image plane is δ, the interval of the laser beam is P, the axis line (optical axis) obtained by connecting the reflection point of the reflection surface of the optical deflector 5 and the image plane, and the optical deflection. If the angle (angle of view / 2) between the position where the laser beam deflected through the device reaches the farthest position in the image area is θ, then within the range of δtan θ <1.5P / 2 That is, substantially no color shift can be visually confirmed.

From this, each photosensitive drum 58 (Y,
M, C and B) outer diameter variation tolerance is δ tan θ
By setting so as to satisfy <1.5P / 2, an image without color misregistration can be obtained.

Next, referring to FIG. 6, the optical scanning device 1 passes through the laser beam L (Y, M, C and B) reflected by the polygon mirror 5a of the optical deflecting device 5 and the post-deflection optical system 30. Laser beams LY, LM, LC and L emitted to the outside of the
The relationship between the inclination of B and the folding mirrors 33B, 37Y, 37M and 37C will be described.

As described above, the polygon mirror 5a of the light deflector 5 reflects the first and second imaging lenses 30a.
The laser beams LY, LM, LC and LB to which the predetermined aberration characteristics have been given by the first and the third folding mirrors 30b and 30b, respectively, are first folding mirrors 33Y, 33M, 33C and 33, 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 as it is to the photosensitive drum 58b through the dustproof glass 39B.
On the other hand, the remaining laser beams LY, LM and LC
Are guided to the second folding mirrors 35Y, 35M and 35C, respectively.
35M and 35C allow the third folding mirror 3
7Y, 37M and 37C, and further the third folding mirrors 37Y, 37M and 37C.
After being reflected by, the dustproof glass 39Y, 39, respectively
Images are formed on the respective photosensitive drums at substantially equal intervals through M and 39C. In this case, the laser beam LB emitted from the first folding mirror 33B and the laser beam LC adjacent to the laser beam LB are also imaged on the photoconductor drums 58B and 58C at substantially equal intervals.

By the way, the laser beam LB is applied to the polygon mirror 5.
After being deflected by a, it is emitted from the optical scanning device 1 toward the photoconductor drum 58 only by being reflected by the folding mirror 33B. From this, the folding mirror 33 is substantially formed.
It is possible to secure the laser beam LB guided by only one B sheet.

When a plurality of mirrors are present in the optical path, this laser beam LB is increased (multiplied) according to the number of mirrors, and changes in various aberration characteristics of an image on the image plane or main scanning line bending, etc. , It is useful as a reference ray for relatively correcting the remaining laser beams L (Y, M and C).

When there are a plurality of mirrors in the optical path, it is preferable that the number of mirrors used for each of the laser beams LY, LM, LC and LB be an odd number or an even number. That is, as shown in FIG. 6, the number of mirrors involved in the laser beam LB in the post-deflection optical system is one except for the polygon mirror 5 a of the optical deflector 5.
(Odd number), the number of mirrors in the post-deflection optical system involved in the laser beams LC, LM and LY is three (odd number) except for the polygon mirror 5a. Here, regarding any one of the laser beams LC, LM and LY, the second
Assuming that the second mirror 35 is omitted, the direction of the main scanning line bending due to the inclination of the lens of the laser beam passing through the optical path (the number of mirrors is even) where the second mirror 35 is omitted is The number of beams, that is, the number of mirrors, is opposite to the direction of the main scanning line bending due to the tilt or the like of an odd number of lenses, which causes a color shift which is a harmful problem when reproducing a predetermined color.

Therefore, 2 × 4 laser beams LY, L
When a predetermined color is reproduced by superimposing M, LC and LB, the number of mirrors arranged in the optical path of each of the laser beams LY, LM, LC and LB is substantially unified to an odd number or an even number. You.

The optical scanning device 1 sequentially deflects 2 × 4 laser beams to form an image on each of the photosensitive drums 58 (Y, M, C and B) of the four image forming sections. Is.

As already described, the optical scanning device 1 reflects the 2 × 4 laser beams emitted from the respective light sources 3 (Y, M, C and B) on the polygon mirror 5a of the optical deflector 5 by each reflection. The first and second image forming lenses 30a
And 30b to form an image on the image plane.

However, for example, the deviation (positional error) of the image forming position in the main scanning direction when a certain laser beam reaches the image surface is as shown in FIG. Beam position (angle of view converted to distance)
In contrast, it varies non-uniformly. That is, when there is a position error corresponding to the image plane beam position as shown in FIG. 12, the image on the image plane is distorted. In this case, the image clock length must be changed at any time in order to keep the distance between adjacent dots formed by the laser beam scanned on the image plane by one scan.

Apart from this, as shown in FIG.
When two laser beams with a constant distance between adjacent dots are obtained, the image clock length required for each laser beam is constant in one scan.

However, the two straight lines have different inclinations, and when the respective laser beams are superposed to form a color image, the respective image clock lengths must be set to different values.

FIG. 14 shows the positional deviation (positional error) of the image plane beam position in the main scanning direction provided by the optical scanning device to which the embodiment of the present invention shown in FIGS. 3 to 11 is applied. There is. In addition, as is clear from FIG.
Although the positional error in the image plane beam position in the main scanning direction is recognized, the deviation between the 2 × 4 laser beams is caused by setting the optical scanning device 1 on the holding members 42 shown in FIG. Are corrected to such a degree that they can be substantially ignored.

Referring to the position error shown in FIG. 14, if the theoretical value (design value) of the image plane beam position in the main scanning direction is Y and the actual value is y, then | y−Y | × When 100 / | Y | (%) is less than 0.5%, the index which is considered to be incapable of visually confirming the image distortion is, for example, a position error of 0.5 mm when the position in the main scanning direction is 130 mm. Therefore, it becomes 0.38%. Therefore, by using the optical scanning device shown in FIGS. 3 to 11, the image clock length during the scanning of the laser beam by one scanning is
It can be fixed.

As described above, since the beam intervals of a plurality of laser beams can be controlled by a single image clock, a plurality of clock variable mechanisms are not required and the cost of the laser drive system incorporated in the image forming apparatus is reduced. Will be reduced.

Next, the operation of the image forming apparatus 100 will be described with reference to FIGS. 1 and 15 to 17. In addition,
16 is a timing chart showing the output timing of main signals of the image forming apparatus shown in FIG. 15, and FIG. 17 is a concept showing a state in which an image is formed based on the main signals shown in FIG. It is a figure.

When an image forming start signal is supplied from an operation panel or a host computer (not shown), each image forming unit 50 (Y,
M, C and B) are warmed up, and the polygon mirror 5a of the optical 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.

Then, under the control of the main controller 101,
Image data D to be printed from an external storage device or host computer or scanner (image reading device)
The AT is loaded into the RAM 102. Part (or all) of the image data taken in 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.

Further, under the control of the main controller 101, the feed roller 82 is urged based on a predetermined timing, for example, the vertical synchronizing signal HSY from the timing control unit 113, and one sheet P from the sheet cassette 80. Is taken out. The timing of the taken-out sheet P is aligned with the toner images of Y, M, C and B provided by the image forming operation by the image forming units 50 (Y, M, C and B) by the registration roller 82. The suction rollers 84 closely contact the conveyance belt 52, and the conveyance belt 52 is guided toward each image forming unit 50 as the conveyance belt 52 rotates.

On the other hand, in parallel with or at the same time as the feeding and transporting operation of the paper P, the laser driving units 116 (Y, M, C and C) are driven 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 stored in the RAM 102 is transferred to each light source 3 (Y, M, C and B).
Is supplied to. As a result, a laser beam for one line is sequentially output from a predetermined position of the effective print width in the main scanning direction to each photoconductor drum 5 of each image forming section 50 (Y, M, C and B).
8 (Y, M, C and B).

In this way, each data control unit 115
Each laser drive unit 1 by controlling (Y, M, C and B)
16 (Y, M, C and B), image data is transferred in order 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 is transferred. 50 (Y, M, C and B) photoconductor drums 58 (Y,
In M, C, and B), a single image of the laser beam is formed by an image clock having a constant clock length.

The first to fourth image forming sections 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 transferred to each developing device 72 (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 corresponds to each photoconductor drum 5
8 (Y, M, C, and B) is rotated toward the paper P being conveyed by the conveyor belt 52, and the transfer device 74 causes the paper P on the conveyor belt 52 to be conveyed at a predetermined timing. Is transferred at a predetermined timing.

As a result, four-color toner images that exactly overlap each other on the paper P are formed on the paper P. In addition,
After the toner image is transferred onto the paper P, the residual toner remaining on the photosensitive drums 58 (Y, M, C and B) is removed by the cleaner 76 (Y, M, C and B), and The residual potential remaining on each photoconductor drum 58 (Y, M, C and B) is equivalent to the static elimination lamp 78 (Y, M, C and B).
It is used for the subsequent image formation.

Paper P holding toner images of four colors electrostatically
Are further conveyed as the conveyor belt 52 rotates, and are separated from the conveyor belt 52 by the difference between the curvature of the belt drive roller 56 and the straightness of the paper P, and the fixing device 9
You will be guided to 4. After the toner image as a color image is fixed on the sheet P guided to the fixing device 94 by melting the respective toners by the fixing device 94,
The sheet is discharged to a discharge tray (not shown).

On the other hand, after the paper P is supplied to the fixing device 94, the conveyor belt 52 is further rotated, the belt cleaner 92 removes the undesired toner remaining on the surface, and the paper is again fed from the cassette 80. It is used for transporting the sheet P to be used.

[0122]

As described above, according to the optical scanning apparatus and the image forming apparatus of the present invention, the beam intervals of a plurality of laser beams can be controlled by a single image clock. As a result, the cost of the laser drive system incorporated in the image forming apparatus is reduced. In addition, a color image free from color misregistration and distortion can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a schematic side view showing a peripheral portion of a photosensitive drum of an image forming unit incorporated in the image forming apparatus shown in FIG.

FIG. 3 is a schematic plan view showing the arrangement of optical members of an optical scanning device incorporated in the image forming apparatus shown in FIGS. 1 and 2.

FIG. 4 is a partial cross-sectional view of the optical scanning device shown in FIG. 3 taken along the optical axis of the system between the first light source and the optical deflecting device.

5 is a schematic cross-sectional view of the optical scanning device shown in FIG. 3 in the sub-scanning direction, showing a state 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. 3 taken at a position where the deflection angle of the optical deflecting device is 0 °.

FIG. 7 is a development view of an optical path obtained by removing a mirror and the like of an optical scanning device cut at a position where a deflection angle of the optical deflecting device shown in FIG. 6 is 0 °.

8 is a schematic plan view showing a state in which each optical member of the pre-deflection optical system of the optical scanning device shown in FIG. 3 is arranged.

9A and 9B are a plan view and a side view showing a laser synthesizing mirror unit of the optical scanning device shown in FIG.

10 is a schematic perspective view of a folding mirror for horizontal synchronization detection of the optical scanning device shown in FIG.

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

FIG. 12 is a graph showing an error of an image forming position with respect to a position of a beam in a main scanning direction which causes color misregistration.

FIG. 13 is a graph showing an error of an image forming position with respect to a position of a beam in a main scanning direction which causes color misregistration.

FIG. 14 is a graph showing the error of the image forming position with respect to the beam position of the 2 × 4 laser beams emitted from the optical scanning device shown in FIGS. 3 to 11 in the main scanning direction.

15 is a block diagram of an image controller of the image forming apparatus shown in FIG.

16 is a timing chart showing the output timing of main signals of the image forming apparatus shown in FIG.

FIG. 17 is a conceptual diagram showing a state in which an image is formed based on the main signals shown in FIG.

[Explanation of symbols]

1 ... Multi-beam optical scanning device, 1a ... Intermediate base, 3
Y, 3M, 3C and 3B ... Light source (first optical means),
3Ya ... yellow first laser, 3Yb ... yellow second laser, 3Ma ... magenta first laser, 3Mb ... magenta second laser, 3Ca ... cyan first laser, 3Cb ... cyan second laser, 3Ba ... black first laser, 3Bb … Black second
Laser, 5 ... Optical deflector, 5a ... Polyhedral main body, 7Y, 7
M, 7C and 7B ... Pre-deflection optical system (first optical means)
, 9Y, 9M, 9C and 9B ... Finite focus lens (first optical means), 11Y, 11M, 11C and 11B
... Hybrid cylinder lens, 13 ... Laser synthesizing mirror unit, 13M ... Magenta reflection surface, 13Y ... Cyan reflection surface, 13B ... Black reflection surface, 13α ... Base, 15 ... Holding member, 17Y, 17M, 17C and 17B ... Plastic cylinder lens , 19Y, 19M, 19C and 19B ... Glass cylinder lens, 23 ... Horizontal synchronization detector, 25 ... Horizontal synchronization folding mirror, 30 ... Post-deflection optical system (second optical means), 30a ... First imaging lens ,
30b ... Second imaging lens, 33Y, 33M, 33C and 33B ... First folding mirror, 35Y, 35M and 35C ... Second folding mirror, 37Y, 37M and 37C ... Third folding mirror, 39Y, 39M ，
39C and 39B ... Dustproof glass, 40a, 40b ... Frame, 41Y, 41M and 41C ... Fixed part, 42
a, 42b ... Holding member, 43Y, 43M and 43C ...
Mirror pressing leaf spring, 45Y, 45M and 45C ... Protrusion, 47Y, 47M and 47C ... Set screw, 50Y,
50M, 50C and 50B ... Image forming unit, 52 ... Conveying belt, 54 ... Belt driving roller, 56 ... Tension roller, 58Y, 58M, 58C and 58B ... Photosensitive drum, 60 ... Positioning roller, 62a, 62b ... Fixed shaft, 64a, 64b ... Bearings, 66a, 66b ... Flexible coupling, 68a, 68b ... Spring, 70Y,
70M, 70C and 70B ... Charging device, 72Y, 72
M, 72C and 72B ... Developing device, 74Y, 74M,
74C and 74B ... Transfer device, 76Y, 76M, 76
C and 76B ... Cleaner, 78Y, 78M, 78C and 78B ... Static eliminator, 80 ... Paper cassette, 82 ... Sending roller, 84 ... Registration roller, 86 ... Adsorption roller, 88 ... Registration sensor, 90 ... Registration sensor, 9
2 ... Conveyor belt cleaner, 94 ... Fixing device, 100 ... Image forming device, 101 ... Main control device, 102 ... RAM, 1
03 ... Nonvolatile memory, 110 ... Image control unit, 111 ...
Image control CPU, 112 ... Bus line, 113 ... Timing control unit, 114Y, 114M, 114C and 11
4 ... Image memory, 115Y, 115M, 115C and 115 ... Data control unit, 116Y, 116M, 116C
And 116 ... Laser driver, 118Y, 118M, 1
18C and 118 ... Timing setting device, 121 ... Horizontal synchronizing signal generating circuit, P ... Paper.

Claims (8)

[Claims] 1. N first lenses for converting a cross-sectional shape of each light emitted from each of the N light emitting members into a predetermined shape, and each light passed through the first lens. Are combined into M pieces, and M sets of second lenses that converge the respective lights combined into M pieces by the combining means in the first direction, and are passed through the second lens. Further, an aggregating unit that aggregates the respective lights so that they can be regarded as one light when viewed from a third direction orthogonal to the first direction and the second direction, and rotates along the first direction. A deflecting means for deflecting the light emitted from the pre-deflection optical system along the first direction, and the deflecting means when the light deflected by the deflecting means is deflected. Rotation of the reflection surface so that images are formed at equal intervals regardless of the rotation angle of the reflection surface And an image forming lens for forming an image of each of the M light beams deflected by the deflecting means at a predetermined position, and having a power defined in accordance with Optical scanning device for giving image forming characteristics, M image carriers arranged corresponding to the M sets of light emitted from the optical scanning device, respectively, and holding M sets of images, and the image carriers. Positioning means for positioning each of the bodies at a position where the M sets of light from the optical scanning device are imaged;
An image forming apparatus comprising: 2. N first lenses for converting a cross-sectional shape of each light emitted from each of the N light emitting members into a predetermined shape, and each light passed through the first lens. Are combined into M pieces, and M sets of second lenses that converge the respective lights combined into M pieces by the combining means in the first direction, and are passed through the second lens. Further, an aggregating unit that aggregates the respective lights so that they can be regarded as one light when viewed from a third direction orthogonal to the first direction and the second direction, and rotates along the first direction. A deflecting means for deflecting the light emitted from the pre-deflection optical system along the first direction, and the deflecting means when the light deflected by the deflecting means is deflected. Rotation of the reflection surface so that images are formed at equal intervals regardless of the rotation angle of the reflection surface Of the M light beams deflected by the deflecting means. , An image forming lens for forming an image at a predetermined position and giving substantially the same image forming characteristics to the respective lights, and M sets of light emitted from the optical scanning device, respectively. M image carriers that are arranged correspondingly and hold M sets of images, and positioning means for positioning each of the image carriers at a position where the M sets of light from the optical scanning device are imaged. When,
An image forming apparatus comprising: 3. N first lenses for converting a cross-sectional shape of each light emitted from each of the N light-emitting members into a predetermined shape, and each light passed through the first lens. Are combined into M pieces, and M sets of second lenses that converge the respective lights combined into M pieces by the combining means in the first direction, and are passed through the second lens. Further, an aggregating unit that aggregates the respective lights so that they can be regarded as one light when viewed from a third direction orthogonal to the first direction and the second direction, and rotates along the first direction. A deflecting means for deflecting the light emitted from the pre-deflection optical system along the first direction, and the deflecting means when the light deflected by the deflecting means is deflected. Rotation of the reflection surface so that images are formed at equal intervals regardless of the rotation angle of the reflection surface Of the M light beams deflected by the deflecting means. , An image forming lens for forming an image at a predetermined position and giving substantially the same image forming characteristics to the respective lights, and M sets of light emitted from the optical scanning device, respectively. M image carriers that are arranged correspondingly and hold M sets of images, and positioning means for positioning each of the image carriers at a position where the M sets of light from the optical scanning device are imaged. And the above M which is positioned at a predetermined position by this positioning means.
Holding means for holding the optical scanning device so that each of the N light beams emitted from the optical scanning device is accurately imaged at a predetermined position on the outer peripheral surface of each image carrier. An image forming apparatus characterized by. 4. N first lenses for converting a cross-sectional shape of each light emitted from each of the N light emitting members into a predetermined shape, and each light passed through the first lens. M combining means for combining the light into M pieces, M lights for combining the respective lights combined into the M pieces by the combining means in the first direction, and respective lights passing through the cylindrical lenses. And an aggregating means for aggregating so as to be regarded as one when viewed from a third direction orthogonal to each of the first direction and the second direction,
Deflection means having a reflecting surface rotated along the first direction, for deflecting the light emitted from the pre-deflection optical system along the first direction, and light deflected by the deflection means. Irrespective of the size of the rotation angle of the reflecting surface of the deflecting means, it is possible to form images at predetermined image forming positions at equal intervals, and the power is defined according to the rotation angle of the reflecting surface. An optical scanning device having an imaging lens for imaging each of the M lights deflected by the deflecting means at a predetermined position, and giving substantially the same imaging characteristics to each light. The M image carriers that are arranged corresponding to the M sets of light emitted from the optical scanning device and hold the M sets of images, and each of the image carriers are the M image carriers from the optical scanning device. Positioning means for positioning at a position where a set of light is imaged,
An image forming apparatus comprising: 5. N first lenses for converting a cross-sectional shape of each light emitted from each of the N light-emitting members into a predetermined shape, and each light passed through the first lens. M combining means for combining the light into M pieces, M lights for combining the respective lights combined into the M pieces by the combining means in the first direction, and respective lights passing through the cylindrical lenses. And an aggregating means for aggregating so as to be regarded as one when viewed from a third direction orthogonal to each of the first direction and the second direction,
Deflection means having a reflecting surface rotated along the first direction, for deflecting the light emitted from the pre-deflection optical system along the first direction, and light deflected by the deflection means. The deflection means and the power defined according to the rotation angle of the reflecting surface capable of forming images at predetermined image forming positions at equal intervals irrespective of the size of the rotation angle of the reflecting surface of the deflection means when the deflection means is rotated. M which has an image forming characteristic for removing the influence of the reflection surface of the light reflected by the reflection surface of M and is deflected by the deflection means.
An optical scanning device having an image forming lens for forming an image of each of the light beams at a predetermined position and giving substantially the same image forming characteristics to the respective light beams, and M emitted from the optical scanning device. M image carriers that are arranged corresponding to the respective sets of light and hold M sets of images, and the M sets of light from the optical scanning device are imaged on the respective image carriers. Positioning means for positioning in position,
An image forming apparatus comprising: 6. N first lenses for converting a cross-sectional shape of each light emitted from each of the N light-emitting members into a predetermined shape, and each light passed through the first lens. M combining means for combining the light into M pieces, M lights for combining the respective lights combined into the M pieces by the combining means in the first direction, and respective lights passing through the cylindrical lenses. And an aggregating means for aggregating so as to be regarded as one when viewed from a third direction orthogonal to each of the first direction and the second direction,
Deflection means having a reflecting surface rotated along the first direction, for deflecting the light emitted from the pre-deflection optical system along the first direction, and light deflected by the deflection means. The deflection means and the power defined according to the rotation angle of the reflecting surface capable of forming images at predetermined image forming positions at equal intervals irrespective of the size of the rotation angle of the reflecting surface of the deflecting means when the deflection means is rotated. M which has an image forming characteristic for removing the influence of the reflection surface of the light reflected by the reflection surface of M and is deflected by the deflection means.
An optical scanning device having an image forming lens for forming an image of each of the light beams at a predetermined position and giving substantially the same image forming characteristics to the respective light beams, and M emitted from the optical scanning device. M image carriers that are arranged corresponding to the respective sets of light and hold M sets of images, and the M sets of light from the optical scanning device are imaged on the respective image carriers. Positioning means for positioning at a position, and the above-mentioned M positioned at a predetermined position by this positioning means.
Holding means for holding the optical scanning device so that each of the N light beams emitted from the optical scanning device is accurately imaged at a predetermined position on the outer peripheral surface of each image carrier. An image forming apparatus characterized by. 7. A light source including N laser elements represented by N = 1 to N = i, and N for converting each laser beam emitted from each laser element of the light source into convergent light or parallel light. First lens group consisting of finite lenses or collimating lenses and M pieces of M = 1 to M = j are arranged, and each light passing through each lens of the first lens group is made into M pieces. The combining means for combining, a second lens group composed of M sets of cylindrical lenses for converging the respective lights from the light sources combined into M pieces by the combining means in the first direction, and the cylindrical lens Aggregation means for aggregating each light that has passed therethrough so that it can be regarded as one when viewed from a third direction orthogonal to each of the first direction and the second direction. , Deflecting means for deflecting the light collected by the collecting means along the first direction, the deflecting means having a reflecting surface rotated about a rotation axis parallel to the third direction, and deflected by the deflecting means. The power that can be focused at predetermined image forming positions at equal intervals regardless of the size of the rotation angle of the reflecting surface of the deflecting means when the light is deflected, and is defined according to the rotation angle of the reflecting surface. And a lens which has an image forming characteristic for removing the influence of the reflecting surface of the light reflected by the reflecting surface of the deflecting means, and forms an image of each of the M lights deflected by the deflecting means at a predetermined position. And an optical scanning device characterized by having a third lens group including, and an optical scanning device which is arranged corresponding to each of the M optical beams emitted from the optical scanning device and which holds M optical images. The individual image carriers and each of the image carriers are subjected to the optical scanning. Positioning means for positioning the M sets of light from the device to be imaged;
An image forming apparatus comprising: 8. A light source including N laser elements represented by N = 1 to N = i, and N for converting each laser beam emitted from each laser element of the light source into convergent light or parallel light. First lens group consisting of finite lenses or collimating lenses and M pieces of M = 1 to M = j are arranged, and each light passing through each lens of the first lens group is made into M pieces. The combining means for combining, a second lens group composed of M sets of cylindrical lenses for converging the respective lights from the light sources combined into M pieces by the combining means in the first direction, and the cylindrical lens Aggregation means for aggregating each light that has passed therethrough so that it can be regarded as one when viewed from a third direction orthogonal to each of the first direction and the second direction. , Deflecting means for deflecting the light collected by the collecting means along the first direction, the deflecting means having a reflecting surface rotated about a rotation axis parallel to the third direction, and deflected by the deflecting means. The power that can be focused at predetermined image forming positions at equal intervals regardless of the size of the rotation angle of the reflecting surface of the deflecting means when the light is deflected, and is defined according to the rotation angle of the reflecting surface. And a lens which has an image forming characteristic for removing the influence of the reflecting surface of the light reflected by the reflecting surface of the deflecting means, and forms an image of each of the M lights deflected by the deflecting means at a predetermined position. And an optical scanning device characterized by having a third lens group including, and an optical scanning device which is arranged corresponding to each of the M optical beams emitted from the optical scanning device and which holds M optical images. The individual image carriers and each of the image carriers are subjected to the optical scanning. Positioning means for positioning at a position where M sets of light from the device are imaged, and the above-mentioned M positioned at a predetermined position by this positioning means.
Holding means for holding the optical scanning device so that each of the N × M light beams emitted from the optical scanning device is accurately imaged at a predetermined position on the outer peripheral surface of each image carrier. An image forming apparatus having.