JP2001343603A - Multi-beam light source scanning device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To secure a wide interval between irradiation objects, to keep the optical path length from the polygon mirror to the irradiation object to the minimum necessary length, to reduce the size of the apparatus, and to perform scanning curvature. Provided is a multi-beam light source device that can suppress the influence of light. SOLUTION: Polarized light is scanned by a polygon mirror 320 and f
first to fourth optical path bending means 710, 720, 73 for guiding each light beam L passing through the? first lens 400 and the f? second lens 500 to the f? third lenses 600A to 600D.
0 and 740 are provided. The optical paths LA to LD constituted by the first to fourth optical path bending means include a first optical path portion for guiding the light beam L passing through the fθ first lens 400 to the first reflecting surface of each of the optical path bending means, It has a second optical path portion for guiding the light beam reflected by the reflecting surface to the second reflecting surface of each optical path bending means, and a third optical path portion for guiding the light beam reflected by the second reflecting surface to each photosensitive drum. It is configured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam light source scanning device for scanning light beams emitted from a plurality of light sources on an object to be irradiated such as a photosensitive drum.

[0002]

2. Description of the Related Art An optical scanning apparatus applied to a monochrome laser printer or the like includes a semiconductor laser that emits light in response to a pixel signal, and a laser beam (hereinafter, referred to as a light beam) output from the semiconductor laser is collimated by a collimating lens. After being converted to light, it is scanned and deflected in the horizontal direction by a polygon mirror, and this light beam is refracted and condensed by an fθ lens, incident on the surface of the photosensitive drum, and exposed to the surface of the photosensitive drum according to the intensity of the pixel signal. I do. After the exposed image is developed with toner, the toner image is transferred to a recording sheet and subjected to a fixing process, so that the image information is printed and fixed on the recording sheet.

Further, an optical scanning apparatus applied to an image forming apparatus such as a color printer or a color copier which prints a color image by transferring a toner image corresponding to each color of yellow, magenta, cyan and black onto a recording paper. There is a multi-beam light source scanning device using an independent light source for each color. This multi-beam light source scanning device is yellow,
An independent light source is provided for each of the colors magenta, cyan, and black, and an independent fθ lens is provided for each color. The photosensitive drum that is independent for each color is configured to irradiate a light beam corresponding to each color to perform exposure. Exposure, development, and transfer processes are performed for each color, and finally, four colors are simultaneously fixed by a fixing device, so that a color image is printed and fixed on recording paper.

[0004]

In the above-described multi-beam light source scanning device, it is necessary to secure a wide interval between independent photosensitive drums for each color. This is because there is a limit in reducing the size of each process member arranged around the photosensitive drum, which performs each process, that is, the charge removing unit, the charging unit, the developing unit, and the transfer unit. This is because the larger is larger, the more advantageous it is, and the greater the capacity of the toner container that supplies the toner to the developing unit, the more the number of toner replenishments can be reduced. On the other hand, in an optical system including an fθ lens, it is necessary to reduce the optical path length from the polygon mirror to each photosensitive drum to a minimum necessary length.
This is because the longer the optical path length from the polygon mirror to each photosensitive drum is, the larger the fθ lens for converging the light beam becomes, and the larger the whole apparatus becomes. Each light beam is deflected and scanned by a polygon mirror and is incident on an optical component that constitutes an optical system. However, depending on the configuration of the optical component, the optical configuration depends on the scanning position of the light beam that is deflected and scanned. A scanning curve may occur in which the position of each light beam scanned in the main scanning direction in the sub-scanning direction is curved by one tendency due to a component error. If the direction of the scanning curve is different in the number of reflections between the light beams, the above-mentioned error acts in reverse, and it is compared with the case where the direction of the scanning curve is the same between the light beams. Therefore, the influence on the print quality of the color image printed on the recording paper may be increased. The present invention has been devised in view of the above circumstances, an object of the present invention is to ensure a wide interval between the irradiation target, and,
The optical path length from the polygon mirror to the object to be illuminated can be kept to the minimum necessary length, and the entire device can be downsized.
An object of the present invention is to provide a multi-beam light source scanning device capable of suppressing the influence of scanning curvature.

[0005]

According to the present invention, there are provided a plurality of light sources for emitting light beams, a polygon mirror for deflecting and scanning each of the light beams emitted from each of the light sources, and a deflection mirror for deflecting and scanning by the polygon mirror. An optical system that converges and guides each of the light beams to a plurality of irradiation targets, wherein the plurality of irradiation targets have an optical path of a light beam deflected and scanned by the polygon mirror. Is positioned so as to be sequentially away from the polygon mirror on the side where is located, and the optical system is composed of a plurality of fθ lenses that converge a light beam.
A lens group, and an optical path bending means provided for each of the light beams to bend the optical path to which the light beam is guided, and the fθ lens group has an fθ through which all the light beams deflected and scanned by the polygon mirror pass. The first lens and the fθ first
A second lens having an fθ second lens through which all light beams that have passed through the lens are passed, and each of the optical path bending means reflects the light beam and changes the direction to turn the optical path first.
An optical path having a reflecting surface and a second reflecting surface, and constituted by the respective optical path bending means, is fθ next to the fθ first lens.
A first optical path portion that guides the light beam that has passed through the second lens to the first reflection surface; a second optical path portion that guides the light beam reflected by the first reflection surface to the second reflection surface; Third to guide the light beam reflected by the reflecting surface to the irradiation target object
And a third optical path portion of an optical path that guides the light beam to an irradiation target disposed closest to the polygon mirror. The third optical path portion includes the polygon mirror and the fθ first lens. And is configured to pass through a portion between

Therefore, according to the present invention, the first and second optical path bending means are so arranged that the optical path lengths of the respective light beams from the reflecting surface of the polygon mirror to the respective objects to be irradiated are all the same.
The position of the second reflecting surface can be set, and in this state,
The third optical path portion of the optical path that guides the light beam to the irradiation target disposed closest to the polygon mirror,
It is configured to pass through a portion between the polygon mirror and the fθ first lens. For this reason, the distance between the polygon mirror and the irradiation target located closest to the polygon mirror can be reduced as much as possible, thereby including the irradiation target located farthest from the polygon mirror. It is also possible to reduce the distance between all the irradiation targets and the polygon mirror. Therefore, it is possible to ensure that all the optical paths from the polygon mirror to each of the irradiation objects have the same optical path length, while securing a necessary interval between the irradiation objects. In addition, since the relative distance from the polygon mirror to each irradiation target can be shortened, the entire multi-beam light source scanning device can be reduced in size. Further, by adjusting the positions of the first and second reflecting surfaces of each optical path bending means, it becomes easy to finely adjust the optical path length of each light beam from the reflecting surface of the polygon mirror to each object to be irradiated. Further, since it is sufficient that each optical path bending means has the first and second reflecting surfaces, the number of reflecting surfaces is three.
Compared with the case where the required optical path bending means is used, the number of components is small, and the size and cost of the device can be reduced. Since each light beam deflected and scanned by the polygon mirror is reflected twice by the first and second reflecting surfaces and is irradiated on each irradiation target, the directions of the scanning curvatures coincide between the irradiated light beams. In addition, it is possible to suppress the influence of the scanning curvature.

Further, according to the present invention, the polygon mirror includes:
A polygon mirror reflecting surface for deflecting and scanning each of the light beams may be provided, and the polygon mirror reflecting surface may be formed of a single surface for deflecting and scanning all of the respective light beams.
Further, according to the present invention, the plurality of light sources can be provided corresponding to four colors of yellow, magenta, cyan, and black. Further, according to the present invention, the plurality of objects to be irradiated are photosensitive drums provided corresponding to four colors of yellow, magenta, cyan, and black, and the directions in which the light beams are scanned by the scanning mechanism are set as respective directions. It can be the length direction of the photosensitive drum.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment,
A case where the multi-beam light source scanning device is applied to a color image forming apparatus will be described. FIG. 1 is a plan view showing a configuration of a multi-beam light source scanning device according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view showing FIG. The multi-beam light source scanning device 1000 includes a housing 1
, A light source unit 100 (shown only in FIG. 1), a cylinder lens unit 200 (shown only in FIG. 1), a polygon mirror unit 300, fθ First lens 400, fθ second lens 5
00, fθ third lenses 600A to 600D, optical path bending means group 700 (only shown in FIG. 2), horizontal synchronization detecting section 80
0 (only shown in FIG. 1). The fθ first lens 400, the fθ second lens 500, the fθ third lenses 600A to 600D, and the optical path bending means group 700 correspond to the optical system in the claims.

As shown in FIG. 2, the bottom wall 10 is
It extends in the horizontal direction, and below it, the lower surface 10B of the bottom wall 10
The four photosensitive drums 20A, 20B, 2
0C, 20D (corresponding to the irradiation target in the claims)
Are rotatably provided with their axes parallel to each other with a horizontal space therebetween. Each of the photosensitive drums 20A, 20B, 20C, and 20D is arranged on one side of the polygon mirror unit 300 when viewed from above, so as to be located at a position sequentially separated from the polygon mirror unit 300 in the reverse order to the above order. ing. Similarly, each fθ third lens 6
00A to 600D are also polygon mirror parts 3 when viewed from a plane.
On one side of 00, it is arranged so as to be located at a position sequentially separated from the polygon mirror unit 300 in the reverse order to the above order. Note that one side of the polygon mirror unit 300 is a side (front side) where an optical path of the light beam L deflected and scanned by the polygon mirror 320 is located.

Further, when viewed from a plane, the polygon mirror 30
The photosensitive drum 20D arranged at a position closest to 0 is arranged so as to be located at a position between the polygon mirror unit 300 and the fθ first lens 400. Similarly, the fθ third lens 600D disposed closest to the polygon mirror unit 300 when viewed from above is disposed so as to be located between the polygon mirror unit 300 and the fθ first lens 400. Each photosensitive drum 20A, 20B, 20C,
20D are provided corresponding to different colors (yellow, magenta, cyan, and black) necessary for forming a color image, and transfer these yellow, magenta, cyan, and black toners to recording paper. Is configured.

The general operation of the multi-beam light source scanning device 1000 is as follows. That is, the four light beams L that have passed from the light source unit 100 through the cylinder lens 230 of the cylinder lens unit 200 are deflected and scanned in the main scanning direction by the polygon mirror unit 300. Each of the scanned light beams L is an fθ first lens 400 and an fθ second lens 50.
0, the optical path bending means group 700 and the fθ third lens 600 are configured to converge on the respective photosensitive drums 20A, 20B, 20C, and 20D and to be deflected and scanned in the main scanning direction. Each light beam L scanned by the polygon mirror unit 300 is guided to the horizontal synchronization detecting unit 800, and the timing of the writing start position in the main scanning direction is synchronized based on the detection operation of the horizontal synchronization detecting unit 800. . Note that the main scanning direction of each light beam L is
A, 20B, 20C, 20D along the length direction,
The scanning direction orthogonal to the main scanning direction is the sub-scanning direction.

Next, the configuration of each section will be described in detail.
The light source unit 100 includes four semiconductor lasers 120A to 120D having the same wavelength of the output light beam L, and four semiconductor lasers 120A to 120D for converting the light beams L emitted from the semiconductor lasers 120A to 120D into parallel light. A collimator lens,
And a semiconductor laser driving circuit for driving each semiconductor laser. And the light source unit 100
The respective light beams L, which have become parallel lights emitted from the respective semiconductor lasers 120A to 120D through the respective collimator lenses, have their respective optical axes coincident in a plan view and are parallel at the same interval in the vertical direction. It is configured to do.

The cylinder lens portion 200 includes a base 210 attached to the upper surface 10A of the wall portion 10 and a base portion 2
The lens holder 220 has a lens holder 220 erected from the top 10 and a cylinder lens 230 held by the lens holder 220. The cylinder lens 230 has an incident surface 230A on which each light beam L emitted from the light source unit 100 is incident.
And an emission surface 230B for emitting each of the incident light beams L. The cylinder lens 230 receives the parallel light beams L emitted from the light source unit 100 and converts the light beams L in the horizontal direction (main scanning direction).
Does not converge, but converges only in the vertical direction (sub-scanning direction) and exits to the polygon mirror unit 300. The focal position of the cylinder lens 230, that is, the position where each light beam L is most converged and becomes a line image extending in the horizontal direction is set to be the position of a reflection surface 322 of the polygon mirror 320 described later. I have.

The polygon mirror 300 includes a motor section 310 attached to the upper surface 10A of the bottom section 10 and a motor section 31.
And a polygon mirror 320 attached to a rotating shaft 312 oriented in the vertical direction of 0. Polygon mirror 3
Reference numeral 20 indicates that six reflecting surfaces 322 (corresponding to a polygon mirror reflecting surface in the claims) are provided so as to form a regular hexagon when viewed from a plane, and each reflecting surface 322 is orthogonal to a horizontal plane. ing. Each reflecting surface 322 forms a single surface, and each light beam L emitted from the cylinder lens 230 is incident on this single surface. In FIG. 1, the motor unit 310 is configured to be rotated at a high speed in the counterclockwise direction at a constant speed by a drive signal input from a motor control circuit (not shown). It is deflected and scanned in the main scanning direction from the top to the bottom of the paper.

The fθ first lens 400 constitutes an fθ lens group together with fθ second and fθ third lenses 500 and 600, which will be described later.
20 functions to converge each light beam L scanned in the main scanning direction on each of the photosensitive drums 20A to 20D. fθ first lens 400 is configured to receive each light beam L deflected and scanned by polygon mirror 320, and is attached to upper surface 10A of bottom wall 10 via a holding member (not shown). fθ first lens 400 is configured as a single member made of a single material. f
θ first lens 400 includes semiconductor lasers 120A to 120A
It has an incident surface 410 on which each of the 0D light beams L is incident, and an exit surface 420 from which each light beam L incident on the incident surface 410 is emitted. The exit surface 420 has a shape having four optical axes corresponding to the respective light beams L, and is configured such that the optical axes are parallel to each other at equal intervals in the vertical direction. Therefore, each light beam L incident on the incident surface 410 at equal intervals in the vertical direction
Are emitted from the emission surface 420 at equal intervals in the vertical direction. The fθ first lens 400 has an action of converging each light beam L mainly in the horizontal direction (main scanning direction), and in the vertical direction (sub scanning direction).
It also has the effect of converging on Here, the function of converging the light beam L in the vertical direction by the fθ first lens 400 is configured to be weaker than the function of converging the light beam L in the horizontal direction.

The fθ second lens 500 has an incident surface 5 on which the light beam L emitted from the fθ first lens 400 is incident.
10 and an emission surface 520 from which the light beam L incident on the incidence surface 510 is emitted.
Is attached via a holding member (not shown). The fθ second lens 500 is formed of a single member made of a single material, and all the light beams L pass through this single member. The fθ second lens 500 has an operation of converging each light beam L only in the horizontal direction (main scanning direction) and not in the vertical direction (sub scanning direction).

The optical path bending means group 700 includes a light beam L passing through the fθ first lens 400 and the fθ second lens 500.
The first to fourth optical path bending means 710, 720, 730, which guide the fθ third lenses 600A to 600D to
740.

The first optical path bending means 710 is composed of first and second mirrors 701 and 702, and of the light beams L emitted from the light source unit 100, the light beam L located at the lowest position in the vertical direction is polygonally shaped. An optical path LA that guides the photosensitive drum 20A disposed farthest from the mirror unit 300
Is composed.

The second optical path bending means 720 is composed of third and fourth mirrors 703 and 704. Of the light beams L emitted from the light source unit 100, the light beam L located second from the bottom in the vertical direction is provided. From the polygon mirror 300 to 2
An optical path LB for guiding the photosensitive drum 20B disposed at the second most distant position is configured.

The third optical path bending means 730 is composed of fifth and sixth mirrors 705 and 706, and among the light beams L emitted from the light source unit 100, the light beam L located at the third position from below in the vertical direction. From polygon mirror 300 to 3
The light path LC leads to the photosensitive drum 20C disposed at the second most distant position.

The fourth optical path bending means 740 is composed of seventh and eighth mirrors 707 and 708, and is the fourth light beam L from the bottom in the vertical direction (ie, the most light beam L in the vertical direction). Light beam L located above
Is configured to an optical path LD that guides the photosensitive drum 20 </ b> D disposed at the fourth farthest position from the polygon mirror unit 300 (that is, the closest relative position).

The first to eighth mirrors 701 to 70
Numerals 8 extend in the main scanning direction of the light beam L, and are attached to the upper surface 10A of the bottom wall 10 via a holding member (not shown).

The third fθ lenses 600A to 600D are:
Each light beam L has an action of converging mainly in the sub-scanning direction, and has an action of converging also in the horizontal direction (main scanning direction). Here, the fθ third lenses 600A to 600D
Is configured to be weaker than the function of converging the light beam L in the vertical direction.

On the other hand, on the bottom wall 10, each photosensitive drum 20A
20D, the openings 12A to 12D extending in parallel with the axes of the photosensitive drums 20A to 20D, that is, extending in the main scanning direction of the light beam L are formed on the bottom wall 1A.
It is provided so as to penetrate in the thickness direction of 0 (vertical direction).
The fθ third lens holding members 610A to 610 are respectively provided on the peripheral edges of the openings 12A to 12D on the upper surface 10A side.
0D (shown only in FIG. 1) is provided.
The fθ third lenses 600A to 600D are held by 10A to 610D. That is, the fθ third lenses 600A to 600D extend in the main scanning direction of the light beam L at individual locations corresponding to the respective light beams L. Then, the fθ third lenses 600A to 600A
00D is an incident surface on which the light beam L is incident, respectively.
Each of the light incident surfaces has an emission surface from which each light beam L is emitted.

Here, each optical path constituted by the optical path bending means group 700 will be described in detail. The optical path LA constituted by the first optical path bending means 710 is configured to transmit the light beam L passing through the fθ first lens 400 and the fθ second lens 500 to the reflection surface 701A of the first mirror 701 (the first reflection surface in the claims). A first optical path portion LA1 leading to
The light beam L reflected by the reflection surface 701A of the first mirror 701 and bent upward is reflected by the reflection surface 702 of the second mirror 702.
A (corresponding to a second reflection surface in the claims) and a light beam L reflected by the reflection surface 702A of the second mirror 702 and bent downward, and a second light path portion LA2 leading to the photosensitive drum 20.
And a third optical path portion LA3 that guides the light onto A.

The optical path LB constituted by the second optical path bending means 720 is used to reflect the light beam L passing through the fθ first lens 400 and the fθ second lens 500 to the reflecting surface 703A of the third mirror 703 (the third embodiment). A first optical path portion LB1 leading to the first mirror 703) and the reflecting surface 7 of the third mirror 703.
A second optical path portion LB2 that guides the light beam L reflected by the third mirror 03A and bent upward to a reflection surface 704A of the fourth mirror 704 (corresponding to a second reflection surface in the claims); and a reflection surface of the fourth mirror 704. A third optical path portion LB that guides the light beam L reflected at 704A and bent downward onto the photosensitive drum 20B
3 are provided.

The optical path LC constituted by the third optical path bending means 730 is used to reflect the light beam L passing through the fθ first lens 400 and the fθ second lens 500 to the reflecting surface 705A of the fifth mirror 705 (the third embodiment). The first optical path portion LC1 leading to the first reflecting surface and the reflecting surface 7 of the fifth mirror 705.
The light beam L reflected at 05A and bent upwards is
The reflection surface 706A of the mirror 706 (the second surface in the claims)
(Corresponding to a reflecting surface), and a third optical path portion L for guiding the light beam L reflected by the reflecting surface 706A of the sixth mirror 706 and bent downward to the photosensitive drum 20C.
C3.

The optical path LD constituted by the fourth optical path bending means 740 transmits the light beam L passing through the fθ first lens 400 and the fθ second lens 500 to the reflection surface 707A of the seventh mirror 707 (the third embodiment of the present invention). A first optical path portion LD1 leading to the first reflecting surface, and a reflecting surface 7 of the seventh mirror 707.
A second optical path portion LD2 that guides the light beam L reflected by the light beam 07A and bent upward to a reflection surface 708A (corresponding to a second reflection surface in the claims) of the eighth mirror 708, and a reflection surface of the eighth mirror 708 The third optical path portion LD that guides the light beam L reflected at 708A and bent downward onto the photosensitive drum 20D
3 are provided. Also, of the optical path LD, the light beam L turned back by the seventh mirror 707
The straight line portion until the light reaches the eighth mirror 708 has an optical path portion passing through a portion above the fθ first and second lenses 400 and 500. Further, in the optical path LD, the light beam L turned back by the eighth mirror 708 is fθ
The third optical path portion LD3 that passes through the third lens 600D and reaches the photosensitive drum 20D includes a polygon mirror portion 3
It passes through a portion between 00 and the fθ first lens 600D.

Further, as is apparent from FIG. 2, the first optical path portions LA1 to LD1 are parallel to each other and are arranged at equal intervals in the vertical direction. The first optical path portion LA1 is disposed, the first optical path portion LB1 is located immediately above the first optical path portion LA, and the first optical path portion LC1 is located immediately above the first optical path portion LB1.
The first optical path portions LD1 are respectively arranged directly above the optical path portions LC1. Further, the first to fourth optical path bending means 7
10, 720, 730, and 740 are the third optical path portions LA3
, LD3 to LD3 intersect with the first optical path portions LA1 to LD1. Further, the first to fourth optical path bending means 710, 720, 730, 740 are arranged so that the light beam L guided by the second optical path parts LA2 to LD2 is directed upward in FIG. 2, that is, the first optical path part LA1.
To the photosensitive drum 20 to be irradiated with the LD1 interposed therebetween
It is configured to face in the opposite direction (upward in FIG. 2) to A to 20D.

Fθ first lens, fθ second lens 400, 500
, Each light beam L is converged mainly in the main scanning direction, and by the action of the fθ third lens 600, each light beam L is converged in the sub-scanning direction. As a result, each light beam L, which is a line image extending in the horizontal direction at the position of the reflection surface 322 of the polygon mirror 320, is deflected and scanned by the reflection surface 322, and thereafter, the fθ first through fθ third lenses are used. 4
Each of the photosensitive drums 20 is operated by the action of 00, 500, and 600.
Point images are converged in both the main scanning direction and the sub-scanning direction at the positions of the planes A to 20D.

In order that the four light beams emitted from the light source unit 100 converge in the main scanning direction and the sub-scanning direction at the positions of the surfaces of the photosensitive drums 20A to 20D to form a point image. The optical path lengths of the four optical paths from the respective collimating lenses of the light source unit 100 to the respective photosensitive drums 20A to 20D are all the same, that is, the optical path lengths of the four optical paths from the polygon mirror 322 to the respective photosensitive drums 20A to 20D are also equal. All are configured to be the same.

The horizontal synchronization detector 800 includes a mirror 810
And a light receiving sensor 820. The mirror 810 moves in the main scanning direction of the photosensitive drum in the beam direction.
An upper surface 10 </ b> A of the bottom wall 10 is disposed at a predetermined position just outside a scanning range that contributes to image formation, and reflects the light beam L reaching the predetermined position to the light receiving sensor 820.
Are attached by a mounting member 812. The light receiving sensor 820 detects the light beam L passing through the fθ second lens 500.
Of the bottom wall 10 is attached to the upper surface 10A of the bottom wall 10 by a mounting member 822 so that the light beam L in a scanning range that does not contribute to image formation guided by the mirror 810 is incident.
By controlling the driving signals of the semiconductor lasers 120A to 120D based on the light receiving signal output from the light receiving sensor 820, the timing of the writing start position in the main scanning direction with respect to the photosensitive drums 20A to 20D can be synchronized. I have.

According to the multi-beam light source scanning device 1000 configured as described above, each light beam L emitted from the light emitting unit 100 and passed through the cylinder lens 230 is deflected and scanned by each reflection surface 322 of the polygon mirror 320. Then, the light enters the fθ first lens 400 and the fθ second lens 500 and is converged. Then, each light beam L emitted from the fθ second lens 500 is applied to each of the above-described optical paths LA to LD.
Are guided to the fθ third lenses 600A to 600D, and are converged as point images on the respective photosensitive drums 20A to 20D, and are scanned in the main scanning direction.

In the first embodiment described in detail above, the first to fourth optical path bending means 710, 720, 73
0, 740 are optical paths LA through LD
θ A first optical path portion for guiding the light beam L passing through the first lens 400 to the first reflecting surface of each of the optical path bending means, and a light beam reflected by the first reflecting surface for the second reflecting surface of each optical path bending means. And a third optical path for guiding the light beam reflected by the second reflection surface to each photosensitive drum. Therefore, the positions of the first and second reflecting surfaces of each optical path bending means can be set such that the optical path lengths of the respective light beams from the reflecting surface of the polygon mirror to the respective photosensitive drums are all the same. In addition, the first of each optical path bending means,
By adjusting the position of the second reflection surface, fine adjustment of the optical path length of each light beam from the reflection surface of the polygon mirror to each photosensitive drum becomes easy.

The reflection surface 32 of the polygon mirror 320
With the positions of the first and second reflecting surfaces of each optical path bending means being set such that the optical path lengths of the respective optical beams L from 2 to the respective photosensitive drums 20A to 20D are all the same, The optical path LD that guides the light beam L to the photosensitive drum 20 </ b> D disposed at a close position has an optical path portion that passes through a location between the polygon mirror 320 and the fθ first lens 400. Accordingly, it is possible to reduce the relative distance between the polygon mirror 320 and the photosensitive drum 20D and the relative distance between the polygon mirror 320 and the fθ third lens 600D when viewed from above. That is,
The distance between the polygon mirror 320 and the photosensitive drum 20D disposed closest to the polygon mirror 320 can be shortened as much as possible, whereby the photosensitive drum 20A disposed farthest from the polygon mirror 320 and other photosensitive drums can be moved. The distance between the drums 20B and 20C and the polygon mirror 320 can also be reduced. As a result, the necessary distance between the photosensitive drums 20A to 20D is secured, and all the optical path lengths of the optical paths LA to LD from the polygon mirror 320 to the respective photosensitive drums 20A to 20D are set to the same length. It becomes possible to be constituted so that it may become. Therefore, it is possible to secure a sufficient space around the photosensitive drums for disposing the charge removing unit, the charging unit, the developing unit, and the transfer unit for performing each process. Also, by securing these spaces, it is possible to secure a space for arranging the toner storage unit that supplies the toner to the developing unit, so that the toner capacity can be increased. Further, since the relative distance from the polygon mirror to each photosensitive drum can be shortened, the entire multi-beam light source scanning device can be downsized. In addition, each optical path bending means has two reflecting surfaces (first and second reflecting surfaces).
(Reflection surface), the number of components is smaller than in the case of using an optical path bending means that requires three or more reflection surfaces, and the device can be reduced in size and cost.

Next, a description will be given of how the multi-beam light source scanning device 100 according to the present embodiment can suppress the influence of scanning curvature. FIG. 3 is an explanatory diagram of a positional relationship between a mirror constituting the optical path bending means and the light beam.
(A) is an explanatory view showing a case where the optical path bending means is constituted by one mirror, and FIG. 3 (B) is an explanatory view showing a case where the optical path bending means is constituted by two mirrors.
FIG. 4 is an explanatory diagram comparing the directions of the scanning curvature of the light beam deflected and scanned by the polygon mirror when the number of reflections of the reflected beam is an odd number and an even number.

FIGS. 3A and 3B show that the light beam L deflected by the polygon mirror is scanned by the optical path bending means 7.
It shows a state of being bent by 50A and 750B. In FIG. 3A, scanning bending occurs until the light beam L deflected and scanned by the polygon mirror is incident on one mirror 751 constituting the optical path bending means 750A, and the light beam L is convex from the position P1 to the position P2. Suppose that it is curved so that Then, the light beam L is reflected only once by the reflection surface 751A, and is guided to a lower photosensitive drum (not shown) below. The moving range of the light beam L in the sub-scanning direction after being bent by the reflecting surface 751A is the range indicated by the positions P1 and P2. On the other hand, the light beam L deflected and scanned by the polygon mirror as shown in FIG.
When the light is reflected twice by the two mirrors 752 and 753 constituting B and guided to a lower photosensitive drum (not shown),
The moving range of the light beam L in the sub-scanning direction after being bent by the two reflecting surfaces 752A and 753A is the range indicated by the positions P1 and P2, and the positional relationship between the positions P1 and P2 is as shown in FIG. And the opposite. That is, the convex direction of the scanning curve is reversed.

FIG. 4 shows that the first optical path bending means 710 is
It is composed of one mirror as shown in FIG.
When the third and fourth optical path bending means 720, 730, and 740 are composed of two mirrors as shown in FIGS. 1 and 2, the base 10 is replaced with each of the photosensitive drums 20A to 20D. A scanning locus drawn by each light beam L formed on the plane S when the light beam L guided by each of the optical paths LA to LD is irradiated on a rectangular plane S that is parallel to the lower surface 10B at an interval. It is illustrated. And, namely,
The convex direction of the scanning curve of the light beam L guided by the optical paths LB, LC, and LD and reflected twice (even number of times) by the reflecting surfaces of the two mirrors, and the reflecting surface of one mirror guided by the optical path LA It can be seen that the convex directions of the scanning curve of the light beam L reflected once (odd number) are opposite to each other. This is due to the difference between whether the number of reflections of the light beam L is odd or even as described with reference to FIG. in this way,
If the direction of the scanning curve is different between the multiple light beams,
There is a possibility that the influence on the print quality of the color image printed on the recording paper may be greater than when the direction of the scanning curve is the same between the light beams.

However, in the multi-beam light source scanning device 100, the first to fourth optical path bending means are each constituted by two mirrors, and each light beam L deflected and scanned by the polygon mirror is reflected twice (even number of times). Irradiates the photosensitive drums 20A to 20D. Therefore, since the directions of the scanning curvatures of the light beams applied to the respective photosensitive drums 20A to 20D coincide with each other, it is possible to suppress the influence of the scanning curvature.

In the above-described first embodiment, an example is shown in which each optical path bending means is constituted by two mirrors, but the present invention is not limited to this. It can be composed of a single prism as shown below. FIG. 5 is a configuration diagram illustrating an example in which the optical path bending means is configured using a single prism, and FIG. 5A is a configuration diagram illustrating a second embodiment using a single prism. (B) is a configuration diagram showing a third embodiment using a single prism.

In the configuration shown in FIG. 5A, the optical path bending means 760 is composed of a single prism 761, and this prism 761 has two reflecting surfaces 761A (the first reflecting surface in the claims). Surface), reflective surface 761B
(Corresponding to the second reflection surface in the claims).
The case where this optical path bending means 760 is configured as the first optical path bending means in FIG. 2 will be described. The optical path LA constituted by the optical path bending means 760 includes a first optical path portion LA1 that guides the light beam L that has passed through the fθ first lens 400 and the fθ second lens 500 from the incident surface 761C of the prism 760 to the reflective surface 761A; A second optical path portion LA2 that guides the light beam L reflected by the surface 761A and bent upward to the reflecting surface 761B, and a third light path L2 that guides the light beam L reflected by the reflecting surface 761B and bent downward to the photosensitive drum 20A.
An optical path portion LA3 is provided. Also in the second embodiment, the optical path bending unit 760 is configured such that the third optical path portion LA3 crosses the first optical path portion LA1. Further, the light beam L guided by the second optical path portion LA2 is directed upward in FIG. 5A, that is, in the direction opposite to the photosensitive drum 20A that is the irradiation target with the first optical path portion LA1 interposed therebetween (see FIG. And upward).

In the configuration shown in FIG. 5B, the optical path bending means 770 is composed of a single prism 771, and this prism 771 has two reflecting surfaces 771A (the first reflecting surface 771A in the claims). Surface), reflective surface 771B
(Corresponding to the second reflection surface in the claims).
A case where the optical path bending means 770 is configured as the first optical path bending means in FIG. 2 will be described. The optical path LA constituted by the optical path bending means 770 is a first optical path that refracts the light beam L passing through the fθ first lens 400 and the fθ second lens 500 downward at the incident surface 771C of the prism 770 and guides the light beam L to the reflecting surface 771A. An optical path portion LA1, a second optical path portion LA2 for guiding the light beam L reflected by the reflecting surface 771A and bent upward to the reflecting surface 771B, and a reflecting surface 77
And a third optical path portion LA3 for guiding the light beam L reflected by 1B and bent downward to the photosensitive drum 20A. Also in the third embodiment, the optical path bending means 7
70 is configured such that the third optical path portion LA3 crosses the first optical path portion LA1. Also, the light beam L guided by the second optical path portion LA2 is directed upward in FIG. 5B, that is, in the direction opposite to the photosensitive drum 20A that is the irradiation target with the first optical path portion LA1 interposed therebetween (see FIG. 5). And upward).

In the second and third embodiments described above, since two reflecting surfaces are formed in a single prism, the positions of the two reflecting surfaces cannot be adjusted independently. Of course has the same operational effects as the first embodiment.

FIG. 6 is a configuration diagram showing a fourth embodiment showing an example in which the optical path bending means is constructed using one prism and one mirror. The case where this optical path bending means 780 is configured as the first optical path bending means in FIG. 2 will be described. The optical path bending means 780 includes a prism 781 and a mirror 782. The optical path LA constituted by the optical path bending means 780 is composed of the fθ first lens 400 and f
The light beam L passing through the second lens 500 is
The first optical path portion LA1 which is once refracted downward at the entrance surface 781B of the light guide 81 and is guided to the reflection surface 781A, and the reflection surface 781A.
The light beam L reflected by the light source and bent upward is emitted from the output surface 781.
A second optical path portion LA2 for guiding the light beam L from C to the reflecting surface 782A of the mirror 782, and a third optical path portion LA3 for guiding the light beam L reflected by the reflecting surface 782A and bent downward onto the photosensitive drum 20A. ing. Also in the fourth embodiment, the optical path bending means 780 is configured such that the third optical path portion LA3 crosses the first optical path portion LA1. Further, the light beam L guided by the second optical path portion LA2 is directed upward in FIG. 6, that is, the photosensitive drum 20 which is an object to be irradiated with the first optical path portion LA1 interposed therebetween.
It is configured to face in the opposite direction (upward in FIG. 6) to A.

In the fourth embodiment described above, the position of the reflecting surface of the prism 781 and the position of the reflecting surface of the mirror 782 are adjusted in order to adjust the optical path length of the light beam L. It is possible to adjust the distance during which fine adjustment of the optical path length of each light beam to the photosensitive drum is facilitated, and it is needless to say that the same operation and effect as those of the first embodiment can be obtained.

In the second, third, and fourth embodiments, the case where the optical path bending means 760, 770, and 780 are respectively replaced by the first optical path bending means has been described as an example. The means 760, 770, and 780 can be replaced with other light path bending means (second, third, and fourth light path bending means) in FIG. FIG.
FIG. 14 is a configuration diagram illustrating a configuration of a multi-beam light source scanning device according to a fifth embodiment. As shown in FIG. 7, in the fifth embodiment, the first optical path bending unit 710 in FIG.
And the second optical path bending means 720 is replaced by an optical path bending means 79 constituted by a single prism 792.
Replaced by 5. The optical path LA constituted by the optical path bending means 790 includes a first optical path portion LA1 that guides the light beam L passing through the fθ first lens 400 and the fθ second lens 500 to the reflection surface 791A of the prism 791;
A second optical path portion LA2 that guides the light beam L reflected by the reflection surface 791A and bent upward to the reflection surface 791B, and a light beam L reflected by the reflection surface 791B is bent downward and guided onto the photosensitive drum 20A. And a third optical path portion LA3. The optical path LB constituted by the optical path bending means 795 is composed of the fθ first lens 400 and the fθ second lens 400.
A first optical path portion LB1 that guides the light beam L passing through the lens 500 to the reflecting surface 792A of the prism 792, and a second optical path portion LB2 that guides the light beam L reflected by the reflecting surface 792A and bent upward to the reflecting surface 792B. And the reflection surface 79
And a third optical path portion LB3 that bends the light beam L reflected by 2B downward and guides it onto the photosensitive drum 20B. In the fifth embodiment described above, since two reflecting surfaces are formed on each of the single prisms 791 and 792, the position of these two reflecting surfaces cannot be adjusted independently. Of course has the same operational effects as the first embodiment.

In the first to fifth embodiments described above, the light source unit 100 is provided with four semiconductor lasers 120A to 120D, and four colors (yellow, magenta, cyan,
Four light beams L corresponding to black) are emitted, and f
Although the four light beams L are converged in the main scanning direction by the θ first and fθ second lenses 400 and 500, the present invention is limited to a configuration in which the number of light sources and light beams L is four. Not something. For example, each of the three light sources emits three light beams L corresponding to three colors of yellow, magenta, and cyan, and the three light beams L are respectively shifted in the main scanning direction by the fθ first and fθ second lenses 400 and 500. Of course, it is also possible to adopt a configuration that converges to

[0048]

As is clear from the above description, the present invention
In a multi-beam light source scanning apparatus, comprising: a plurality of light sources; a polygon mirror; and an optical system that converges and guides each light beam deflected and scanned by the polygon mirror to a plurality of irradiation targets. The object is arranged so as to be located at a position sequentially separated from the polygon mirror on the side where the optical path of the light beam deflected and scanned by the polygon mirror is located, and the optical system includes a plurality of fθ lenses for converging the light beam. lens group, and an optical path bending unit provided for each of the light beams to bend the optical path to which the light beam is guided, and the fθ lens group allows all the light beams deflected and scanned from the polygon mirror to pass therethrough. an fθ first lens, and an fθ second lens through which all light beams passing through the fθ first lens pass;
Each of the optical path bending units has a first reflection surface and a second reflection surface that turn the optical path by reflecting and changing the direction of the light beam. A first optical path portion that guides the light beam that has passed through the fθ second lens after the fθ first lens to the first reflection surface, and a second light path portion that guides the light beam reflected by the first reflection surface to the second reflection surface An irradiation target configured to include an optical path portion and a third optical path portion that guides the light beam reflected by the second reflection surface to the irradiation target, and disposed at a position closest to the polygon mirror; The third optical path portion of the optical path for guiding the light beam to an object is configured to pass through a location between the polygon mirror and the fθ first lens.

Therefore, according to the present invention, the first and second optical path bending means are arranged so that the optical path length of each light beam from the reflecting surface of the polygon mirror to each object to be irradiated is all the same.
The position of the second reflecting surface can be set, and in this state,
The third optical path portion of the optical path that guides the light beam to the irradiation target disposed closest to the polygon mirror,
It is configured to pass through a portion between the polygon mirror and the fθ first lens. For this reason, the distance between the polygon mirror and the irradiation target located closest to the polygon mirror can be reduced as much as possible, thereby including the irradiation target located farthest from the polygon mirror. It is also possible to reduce the distance between all the irradiation targets and the polygon mirror. Therefore, it is possible to ensure that all the optical paths from the polygon mirror to each of the irradiation objects have the same optical path length, while securing a necessary interval between the irradiation objects. In addition, since the relative distance from the polygon mirror to each irradiation target can be shortened, the entire multi-beam light source scanning device can be reduced in size. Further, by adjusting the positions of the first and second reflecting surfaces of each optical path bending means, it becomes easy to finely adjust the optical path length of each light beam from the reflecting surface of the polygon mirror to each object to be irradiated. Further, since it is sufficient that each optical path bending means has the first and second reflecting surfaces, the number of reflecting surfaces is three.
Compared with the case where the required optical path bending means is used, the number of components is small, and the size and cost of the device can be reduced. Since each light beam deflected and scanned by the polygon mirror is reflected twice by the first and second reflecting surfaces and is irradiated on each irradiation target, the directions of the scanning curvatures coincide between the irradiated light beams. In addition, it is possible to suppress the influence of the scanning curvature.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a multi-beam light source scanning device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which FIG. 1 is viewed from a cross section taken along line AA.

FIG. 3 is an explanatory diagram of a positional relationship between a mirror and a light beam constituting an optical path bending unit. FIG.
FIG. 3 is an explanatory view showing a case where the mirror is composed of two mirrors.
(B) is an explanatory view showing a case where the optical path bending means is composed of two mirrors.

FIG. 4 is an explanatory diagram comparing the directions of the scanning curvature of the light beam deflected and scanned by the polygon mirror when the number of reflections of the reflected beam is an odd number and an even number.

FIG. 5 is a configuration diagram illustrating an example in which an optical path bending unit is configured using a single prism, and FIG. 5A is a configuration diagram illustrating a second embodiment using a single prism; FIG. 5B is a configuration diagram showing a third embodiment using a single prism.

FIG. 6 is a configuration diagram illustrating a fourth embodiment illustrating an example in which an optical path bending unit is configured using one prism and one mirror.

FIG. 7 is a configuration diagram illustrating a configuration of a multi-beam light source scanning device according to a fifth embodiment of the present invention.

[Explanation of symbols]

1000 Multi-beam light source scanning device 20A to 20D Photosensitive drum 100 Light source unit 320 Polygon mirror 400 fθ first lens 500 fθ second lens 710, 720, 730, 740 First, second, third,
Fourth optical path bending means 760, 770, 780, 790, 795 Optical path bending means L Light beam LA1 to LD1 First optical path section LA2 to LD2 Second optical path section LA3 to LD3 Third optical path section

Claims (10)

[Claims] A plurality of light sources that emit light beams; a polygon mirror that deflects and scans each of the light beams emitted from each of the light sources; and a plurality of light beams that are deflected and scanned by the polygon mirror. A multi-beam light source scanning device comprising: an optical system that converges and guides an object to be irradiated; wherein the plurality of objects to be irradiated are separated from the polygon mirror on the side where the optical path of the light beam deflected and scanned by the polygon mirror is located. The optical system is arranged so as to be sequentially located at a distance from each other, and the optical system turns an fθ lens group including a plurality of fθ lenses that converge a light beam, and an optical path provided for each light beam and guided to the light beam. The fθ lens group includes an fθ first lens through which all light beams deflected and scanned from the polygon mirror pass; fθ second that all light beams passing through the θ first lens passes
A lens, and each of the optical path bending means has a first reflection surface and a second reflection surface for turning the optical path by reflecting and changing the direction of the light beam, and is constituted by each of the optical path bending means. The optical path is f
a first optical path portion that guides the light beam that has passed through the fθ second lens after the θ first lens to the first reflection surface, and a second light path portion that guides the light beam reflected by the first reflection surface to the second reflection surface
An irradiation target configured to include an optical path portion and a third optical path portion that guides the light beam reflected by the second reflection surface to the irradiation target object, and disposed at a position closest to the polygon mirror; A multi-beam light source scanning device, wherein the third optical path portion of the optical path for guiding the light beam to an object is configured to pass through a location between the polygon mirror and the fθ first lens. . 2. At least one of said optical path bending means.
One optical path bending means is composed of first and second mirrors,
2. The multi-beam light source scanning device according to claim 1, wherein said first and second reflecting surfaces are constituted by respective reflecting surfaces formed on said first and second mirrors. 3. At least one of said optical path bending means.
The two optical path bending means are constituted by a single prism having two reflecting surfaces, and the first and second reflecting surfaces are constituted by the two reflecting surfaces of the single prism. The multi-beam light source scanning device according to claim 1. 4. At least one of said optical path bending means.
The two optical path bending means include a prism having one reflection surface and a mirror having one reflection surface.
The second reflecting surface is constituted by a reflecting surface of the prism and a reflecting surface of the mirror.
A multi-beam light source scanning device according to claim 1. 5. The optical path bending means according to claim 1, wherein said third optical path section crosses said first optical path section. Multi-beam light source scanning device. 6. The optical path bending means is characterized in that a light beam guided by the second optical path portion is directed in a direction opposite to the irradiation target object with the first optical path portion interposed therebetween. The multi-beam light source scanning device according to any one of claims 1 to 5, wherein 7. The fθ first lens according to claim 1, wherein the fθ first lens is configured to mainly converge the light beams in a sub-scanning direction orthogonal to the main scanning direction. The multi-beam light source scanning device according to claim 1. 8. The multi-beam as claimed in claim 1, wherein the fθ second lens is configured to only converge the light beams in the main scanning direction. Light source scanning device. 9. The fθ lens group further includes a number of fθ third lenses corresponding to the number of the light sources, and each light beam passes through the fθ second lens after passing through the fθ second lens. The multi-beam light source scanning device according to any one of claims 1 to 8, wherein the multi-beam light source scanning device is configured to perform scanning. 10. The fθ third lens constituting the fθ third lens is characterized in that each of the plurality of fθ lenses mainly converges a light beam in a sub-scanning direction orthogonal to the main scanning direction. The multi-beam light source scanning device according to claim 9, wherein