JP2001296492A - Scanning optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning optical device capable of not only color printing by a tandem system but monochrome printing at higher speed than that for color printing. SOLUTION: In the scanning optical device of a tandem system provided with a light source part 11 to emit a plurality of laser beams L1-L4, a plurality of photoreceptor drums 51-54 made to correspond to laser beams L1-L4 respectively, and the polygon mirror part 2 and scanning optical systems 3, 4 which make each laser beam L1-L4 scan on each photoreceptor drum 51-54, respectively, an optical path changeover part 12 capable of changing an optical path is provided so that each laser beam L1-L4 emitted from the light source part 11 is altogether guided on one photoreceptor drum 51. Because a plurality of mutually adjacent scanning lines can be formed on the photoreceptor drum 51 by this optical path changeover part 12, two or more lines can be simultaneously plotted on the photoreceptor drum 51.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called tandem scanning optical device used for a color laser printer or the like.

[0002]

2. Description of the Related Art A tandem scanning optical apparatus includes a plurality of photosensitive drums provided for each color component, and a plurality of scanning optical systems for forming scanning lines on the respective photosensitive drums. And this tandem scanning optical device is
An image formed for each color component on each photosensitive drum is subjected to multiple development on one sheet to perform color printing.

Usually, four photosensitive drums are provided corresponding to the respective color components of yellow, magenta, cyan, and black (YMCK). The scanning optical device of the tandem system uses a YMC
The laser beam is individually scanned in correspondence with each color component of K, and an image of each color component of YMCK is formed on each photosensitive drum, thereby speeding up the image formation for color printing.

[0004]

The tandem scanning optical device is used not only for forming an image for color printing but also for forming an image for monochrome printing. When forming an image for monochrome printing, the scanning optical system in the scanning optical device scans only a laser beam corresponding to one color (black) to form an image on one photosensitive drum. In this case, the scanning optical system uses the other three colors (yellow,
The laser beams corresponding to magenta and cyan, respectively, are not scanned.

Therefore, although an image for monochrome printing only needs to be formed on one photosensitive drum, the image formation for one photosensitive drum is the same as that for color printing. It takes the same amount of time.

It is therefore an object of the present invention to provide a scanning optical apparatus which can form an image for color printing at a high speed and can form an image for monochrome printing at a higher speed than the image forming for color printing. It is an object of the present invention.

[0007]

The scanning optical device according to the present invention employs the following configuration in order to solve the above problems.

According to a first aspect of the present invention, there is provided a scanning optical device, comprising: a light source unit for emitting a plurality of laser beams at regular intervals in a predetermined direction; and a laser beam emitted from the light source unit in the predetermined direction. An optical path switching unit that switches between a first state in which light is guided by being separated into each of a plurality of spatial regions in the above and a second state in which light is guided densely in any of the spatial regions; A deflecting unit that simultaneously deflects and scans the plurality of guided laser beams in a direction orthogonal to the predetermined direction; and converges each of the laser beams deflected and scanned by the deflecting unit. And a scanning optical system that separates the optical path and guides the optical path onto a photoconductor corresponding to each spatial region.

With such a configuration, the optical path switching unit includes:
Not only can each laser beam emitted from the light source unit be scanned on the photoconductor corresponding to the laser beam, but also, by collecting each laser beam emitted from the light source unit on a photoconductor, It is also possible to draw a plurality of lines on the body at the same time.

The optical path switching unit includes a first prism that receives a plurality of laser beams emitted from the light source unit and emits the laser beams arranged at a predetermined interval in the predetermined direction. A second prism into which a plurality of laser beams emitted from the light source unit enter and are arranged in a state of being arranged close to each other in the predetermined direction, and the first prism is arranged in the first state. A switching mechanism arranged on the optical path of each laser beam emitted from the light source unit, and in the second state, the second prism arranged on the optical path of each laser beam emitted from the light source unit. It may be.

Further, the scanning optical system includes a front group lens for transmitting both laser beams deflected and scanned from the deflection section, and a plurality of rear group lenses arranged corresponding to each photoconductor. It may have a scanning lens. The deflecting unit may be a polygon mirror unit having a polygon mirror. In this case, the scanning lens is f
An fθ lens having θ characteristics may be used.

In addition, when the optical path switching unit is in the first state, the scanning optical system transmits each laser beam emitted from the front lens to the rear lens corresponding to the position in the predetermined direction. Light guiding means for guiding each of the laser beams emitted from the front group lens to one of the rear group lenses when the optical path switching unit is in the second state. Is also good. The light guide may be a mirror group including a plurality of mirrors.

Further, each of the photoconductors may be a photoconductive drum corresponding to each color component of yellow, magenta, cyan, and black. Further, the light source unit may include four light sources that emit laser beams. Note that each light source may be a semiconductor laser.

Further, the scanning optical device may have a control unit for controlling each of the light sources and the photosensitive drums.
The control unit sets the optical path switching unit to the first state when forming a color image, and causes the light sources to correspond to the color components of the photosensitive drums arranged on the optical path of the laser beam emitted from the light source. And each photosensitive drum is rotated at the same speed. On the other hand, the control unit sets the optical path switching unit to the second state when forming a monochrome image, and sets each light source on a single photosensitive drum arranged on the optical path of a laser beam emitted from the light source. Are modulated in accordance with a plurality of scanning lines arranged in close proximity to each other, and the photosensitive drum on which these scanning lines are formed is rotated at a higher speed than when forming a color image.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A scanning optical device according to an embodiment of the present invention will be described below with reference to the drawings. FIG.
1 is a plan view showing a scanning optical device of the present embodiment. FIG. 2 is a sectional view taken along line II-II in FIG. This scanning optical device includes a light source unit for emitting a plurality of laser beams, a polygon mirror unit for simultaneously deflecting and scanning these laser beams, and a polygon mirror unit 2
Lens group 3 for converging each laser beam deflected and scanned from the image plane to the image plane, and a folding mirror group 4.

A base plate 6 is provided at the bottom of the scanning optical device and fixed horizontally to the upper part of a housing (not shown). The base plate 6 has a substantially rectangular plate shape. Above the base plate 6, a light source unit 1, a polygon mirror unit 2, an fθ lens group 3, and a folding mirror group 4 are arranged. The photosensitive drum 5 is disposed below the base plate 6.

The light source unit 1 has four laser beams L
A light source unit 11 for emitting light beams L1 to L4, an optical path switching unit 12 for switching the optical paths of the laser beams L1 to L4 emitted from the light source unit 11 as will be described later, and an optical path switching unit 12
And has a cylinder lens 13 for converging each laser beam emitted from the. The four cylinder lenses 13 are provided side by side in a direction perpendicular to the base plate 6, and convert each of the laser beams incident as parallel light in a direction perpendicular to the base plate 6 (a direction corresponding to the sub-scanning direction). Only converge.

Hereinafter, the light source unit 11 in the light source unit 1 will be described.
The configuration of the optical path switching unit 12 will be further described. FIG. 3 is a plan view of the light source unit 11 and the optical path switching unit 12.
As shown in FIG. 3, the light source unit 11 and the optical path switching unit 12 are arranged on the base B. In addition, this base B
Are fixed on the base plate 6.

The light source unit 11 includes semiconductor lasers LD1 to LD4 as light sources and these semiconductor lasers LD1 to LD4.
, The collimator sections C1 to C4, the adjustment sections W1 to W4, and the respective collimator sections C1 to C4.
4 and a holding unit 112 that holds the adjustment units W1 to W4,
Have.

The vertical wall 111 is disposed substantially perpendicular to the base plate 6, and fixes the first to fourth semiconductor lasers LD1 to LD4, respectively. The first to fourth semiconductor lasers LD1 to LD4 emit the first to fourth laser beams L1 to L4, respectively.

Each of the semiconductor lasers LD1 to LD4 is
The arrangement is such that the beam axis of the first laser beam L1 coincides with the beam axis of the fourth laser beam L4 when viewed from a plane. Further, each of the semiconductor lasers LD1 to LD1
When viewed from a plane, the LD 4 emits these laser beams L
With respect to the beam axes of L1 and L4, the second laser beam L2
And the beam axis of the third laser beam L3 are arranged at predetermined intervals on opposite sides.

The first to fourth semiconductor lasers LD1 to LD4
The semiconductor lasers LD4 are arranged at regular intervals in the height direction from the side close to the base plate 6 to the side away from the base plate 6 (see FIGS. 5 and 6). The semiconductor lasers LD1 to LD4 are arranged such that the beam axes of the laser beams L1 to L4 are parallel to the base plate 6, respectively.

The holding section 112 has four flat blocks having a predetermined thickness. These blocks are arranged at predetermined intervals in a direction perpendicular to the base plate 6 corresponding to the semiconductor lasers LD1 to LD4. The respective blocks corresponding to the respective semiconductor lasers LD1 and LD4 are arranged so that their positions in plan view coincide with each other. On the upper side of each block, a holding groove having a substantially V-shaped cross section is formed along the beam axis direction of each of the laser beams L1 to L4.

Each of the first to fourth collimator sections C1 to C4 comprises a cylindrical lens barrel and a collimator lens fixed in the lens barrel. First adjustment unit W1
The fourth to fourth adjusting units W4 each include a cylindrical lens barrel and a wedge prism fixed in the lens barrel.

In each holding groove of the holding section 112, collimator sections C1 to C4 and adjustment sections W1 to W4 are mounted, respectively. The collimator sections C1 to C4 and the adjustment sections W1 to W4 are pressed and fixed to the holding grooves by leaf springs (not shown).

In this state, the first collimator C
The optical axis of the first collimator lens and the central axis of the lens barrel of the first adjustment unit W1 coincide with the beam axis of the laser beam L1. The optical axis of the collimator lens of the second collimator unit C2 and the center axis of the lens barrel of the second adjustment unit W2 are:
It coincides with the beam axis of the laser beam L2. The optical axis of the collimator lens of the third collimator section C3 and the center axis of the lens barrel of the third adjustment section W3 are the laser beam L3
Of the beam axis. Further, the optical axis of the collimator lens of the fourth collimator unit C4 and the fourth adjustment unit W4
The center axis of the lens barrel coincides with the beam axis of the laser beam L4.

The laser beams L1 to L4 emitted from the respective semiconductor lasers LD1 to LD4 are converted into parallel light by the collimator lenses of the respective collimator sections C1 to C4, and pass through the wedge prisms of the respective adjustment sections W1 to W4. I do. The operator adjusts the focus by displacing each of the collimator sections C1 to C4 in the optical axis direction of the collimator lens so that a laser beam is formed on each of the photosensitive drums 51 to 54 as described later. Can be. In addition, the operator rotates each of the adjustment units W1 to W4 about the central axis of the lens barrel to thereby rotate each of the laser beams L1 to L4 formed on each of the photosensitive drums 51 to 54 as described later.
The spot position of L4 can be adjusted.

FIG. 4 schematically shows the semiconductor lasers LD1 to LD4, the collimator sections C1 to C4, and the adjustment sections W1 to W4, which are arranged as described above, in the light source section 11 when viewed from a plane. FIG. 5 is a view of FIG. 4 as viewed in the direction of arrow V. FIG. 6 is a view of FIG.
It is the figure seen in the I direction. With reference to these drawings, the configuration of the light source unit 11 will be further described.

Semiconductor laser LD1 and collimator section C1
Are not shown in FIG. 4 because they are disposed immediately below the semiconductor laser LD4 and the collimator section C4, respectively. When viewed from a plane, the semiconductor laser LD4 is
It is arranged between the two semiconductor lasers LD3 and LD2. Similarly, the collimator section C4 includes both collimator sections C
3 and C2. Also, the adjusting unit W4
Is arranged in the middle between the two adjustment units W3 and W2. Then, in such a plan view, the adjustment unit W1 is disposed on the rear side (the left side in FIG. 4) of the adjustment unit W4.

Further, as shown in FIG.
The beam axes of the laser beams L1 to L4 emitted from the laser beams L1 to L4 are arranged in the height direction from the bottom to the top in FIG. They will line up as if they were open. Note that the beam axes of the laser beams L1 to L4 are completely parallel when viewed in a plan view, but slightly inclined from a state where they are parallel to each other in a side view.

Next, the optical path switching section 12 will be described.
As shown in FIG. 3, the optical path switching unit 12 includes an elongated rectangular plate-shaped stage 121, a color rendering prism T and a monochrome rendering prism M, a worm 122, and a worm 122 fixed on the stage 121, respectively. Gear 12
3, the rotating shaft 124 and its pair of bearings 125,
126. The prism T for color drawing corresponds to the first prism, and the prism M for monochrome drawing.
Corresponds to the second prism.

In the base B of the light source unit 1, a guide groove G perpendicular to each of the laser beams L1 to L4 emitted from the light source unit 11 is opened at a position behind the light source unit 11 on the optical path. Have been. And the stage 121
Is slidably engaged with the guide groove G with its surface parallel to the surfaces of the base plate 6 and the base B and its longitudinal direction parallel to the direction of the guide groove G. For example, the stage 121 may be engaged by slidably fitting a dovetail tenon formed at a lower portion thereof with a dovetail groove formed in the guide groove G.

Further, the stage 121 has a protruding plate P protruding from its side surface perpendicularly to its longitudinal direction. The protruding plate P has a screw hole formed in a direction parallel to the longitudinal direction of the stage 121. Rotary shaft 12
Reference numeral 4 denotes a state in which a male screw cut on the surface is screwed into a screw hole of the protruding plate P, and both ends thereof are both bearings 125, 12 respectively.
6 rotatably supported.

The second bearing 1 on the rotating shaft 124
In the vicinity of the end on the side close to 26, a worm gear 123
Is attached. The worm gear 123 meshes with the worm 122. And this worm 1
Reference numeral 22 is connected to a motor (not shown), and rotates the worm gear 123 by being rotationally driven by the motor. When the worm gear 123 rotates, the rotating shaft 1
24 also rotates, and the stage 121 slides along the guide groove G. These stages 121, worm 122,
Worm gear 123, rotating shaft 124, and dual bearing 12
Reference numerals 5 and 126 correspond to a switching mechanism.

In FIG. 3, the stage 121 is
The position where the protruding plate P is brought close to the first bearing 125 is taken. In this state, the laser beams L1 to L4 emitted from the light source unit 11 are incident on the prism M for monochrome drawing. The position of the stage 121 in the state shown in FIG. 3 is called a monochrome drawing position. When the scanning drawing apparatus performs monochrome drawing by a so-called multi-beam method, the stage 121 is arranged at this monochrome drawing position.

Further, the stage 121 can take a position where the protruding plate P is brought close to the second bearing 126 by rotating the worm 122 by a motor (not shown). FIG. 7 is a plan view of the light source unit 11 and the optical path switching unit 12 in a state where the stage 121 is arranged as described above. That is, in the state shown in FIG. 7, the laser beams L2 and L3 emitted from the light source unit 11 are incident on the prism T for color drawing. The light source unit 11
The laser beams L1 and L4 emitted from pass through the vicinity of the color drawing prism T. The position of the stage 121 in this state is called a color drawing position.
When the scanning type drawing apparatus performs the so-called tandem color drawing, the stage 121 is arranged at this color drawing position.

An origin dog J is attached to the protruding plate P. Then, the origin sensor E fixed to the base B detects the position of the origin dog J. That is, the origin sensor E can detect whether the stage 121 is moving to the monochrome drawing position or the color drawing position.

FIG. 8 is a plan view showing a color drawing prism T in the optical path switching unit 12. As shown in FIG. Also, FIG.
FIG. 9 is a diagram when FIG. 8 is viewed in the IX direction. As shown in these figures, the prism T for color drawing is a first prism T
a and the second prism Tb.

The first prism Ta has a slender parallelogram on its surface and bottom surface, and its four side surfaces are perpendicular to the surface and bottom surface, respectively. Accordingly, as shown in FIG. 8, the first prism Ta has an elongated parallelogram shape in plan view. The first prism Ta has a first reflecting surface Ta1 and a second reflecting surface Ta2 having a pair of side surfaces in contact with the short sides of the parallelogram on the surface.

The first reflection surface Ta1 is connected to the light source section 11 (FIG. 8).
45 ° to the side of (right side of). Then, when the stage 121 is arranged at the color drawing position, the first prism Ta is configured such that the beam axis of the second laser beam L2 coincides with the center of the first reflection surface Ta1.
It is fixed to the stage 121. In this case, the beam axis of the laser beam L2 is bent by 90 ° in a plane parallel to the base plate 6 by the first reflection surface Ta1, and is directed upward in FIG. 8 to reach the center of the second reflection surface Ta2. Further, the beam axis of the laser beam L2 is
The light is bent 90 ° in a plane parallel to the base plate 6 by the second reflection surface Ta2, and goes out of the first prism Ta to the left in FIG.

The second prism Tb has the same shape as the first prism Ta, but is arranged above the first prism Ta with its front and back reversed. The second prism Tb is arranged such that, in plan view, each long side of the surface of the parallelogram is located on a straight line extending from each long side of the surface of the first prism Ta. One of the short sides is one of the short sides (Ta2) on the surface of the first prism Ta.
) Are arranged so as to intersect at the midpoint of each other. Note that, of the pair of reflection surfaces Tb1 and Tb2 of the second prism Tb, the one that intersects with the second reflection surface Ta2 of the first prism Ta in plan view is the second one.
The first reflection surface Tb1 is the reflection surface Tb2 and is disposed on the side away from the first prism.

The second prism Tb is arranged such that when the stage 121 is arranged at the color drawing position, the beam axis of the third laser beam L3 coincides with the center of the first reflection surface Tb1. It is fixed to the stage 121. In this case, the beam axis of the laser beam L3 is bent by 90 ° in a plane parallel to the base plate 6 by the first reflection surface Tb1, and is directed downward in FIG. 8 to reach the center of the second reflection surface Tb2. Further, the beam axis of the laser beam L3 is bent by 90 ° in a plane parallel to the base plate 6 by the second reflection surface Tb2, and goes to the left in FIG. 8 to go out of the second prism Tb.

The laser beam L1 passes below the prism T, and the laser beam L4 passes above the prism T. Note that the beam axis of the laser beam L1 and the beam axis of the laser beam L4 correspond to the second reflection surface Ta2 and the second prism Tb of the first prism Ta in plan view.
Pass through the point where the second reflection surface Tb2 intersects with the second reflection surface Tb2. Further, the beam axis of the laser beam L2 reflected by the second reflection surface Ta2 of the first prism Ta and the beam axis of the laser beam L3 reflected by the second reflection surface Tb2 of the second prism Tb are also viewed in plan. , Coincides with the beam axes of the laser beams L1 and L4.

As described above, the beam axes of the laser beams L1 to L4 have the same position in plan view immediately after the prism T, and are arranged at equal intervals in the direction perpendicular to the base plate 6. That is, the beam axes of the laser beams L1 to L4 are arranged at regular intervals in a plane perpendicular to the base plate 6 so that the interval between adjacent ones becomes d.

FIG. 10 is a plan view showing a prism M for monochrome drawing in the optical path switching unit 12, and FIG.
It is the figure which looked at FIG. 10 in the XI direction. FIG. 12 is a perspective view of the prism M for monochrome drawing. As shown in these figures, a prism M for monochrome drawing
Consists of a first portion Ma, a second portion Mb, and a third portion Mc, and is fixed to the stage 121. Here, for convenience of explanation, the prism M is replaced with the first portion M
Although the prism M is divided into a, a second portion Mb, and a third portion Mc, the prism M may be actually formed integrally. In addition, the prism M may be configured by bonding the respective parts according to a division method other than the division method of the first part Ma, the second part Mb, and the third part Mc to each other.

The prism M is arranged with the vertical direction in FIG. 10 and 11, the right side of the prism M corresponds to the front side on the optical path of each of the laser beams L1 to L4.
11 corresponds to the rear side on the optical path of each of the laser beams L1 to L4. Here, the up-down direction is the up-down direction in FIG. 11, and the front-rear direction is the left-right direction in FIGS. However, when referring to the up, down, left, and right directions only in the figures in FIG.

The first portion Ma has a shape equivalent to that obtained by cutting off both ends of a right prism by a pair of mutually parallel planes each forming 45 degrees with respect to the center axis thereof. That is,
The first part is a pair of parallelogram-shaped side surfaces parallel to each other,
And four side surfaces formed by a pair of mutually parallel rectangular side surfaces, and a pair of reflecting surfaces M1 and M2 which are parallel rectangular end surfaces. Then, the first portion Ma
Is directed parallel to the plane including the beam axes of the laser beams L1 and L4, and the rectangular sides are directed to the beam axes of the laser beams L1 to L4. , And are arranged vertically. The reflecting surface M1 and the reflecting surface M2 are arranged at positions shifted by about 3 × d in the vertical direction.

The second portion Mb has the same shape as that obtained by diagonally cutting off both ends of an elongated rectangular prism. The second portion Mb is arranged such that the central portion of one of the four side surfaces is in contact with the rear surface of the first portion Ma, and the longitudinal direction of the second portion Mb is the longitudinal direction of the first portion Ma. It is arranged perpendicular to the direction. Both end surfaces of the second portion are rectangular, and the third reflection surface M3 (the lower side in FIG. 10) and the fourth reflection surface M
4 (upper side in FIG. 10). The normal line of the one reflection surface M3 is perpendicular to the beam axis of each of the laser beams L1 to L4, and forms an angle of 45 ° with the lower surface of the second portion Mb. The other reflecting surface M4
Are parallel to the upper and lower surfaces of the second portion Mb, respectively, and each of the laser beams L1 to L4
Each form an angle of 45 ° with respect to the beam axis.

Further, the second portion Mb has a reflection surface M3
Immediately below the lower surface at the side end, a projection having a shape protruding from this surface is provided. The projection is continuous with the front surface of the second portion Mb and formed in the same plane as the square surface, and contacts the lower end of the square surface and the second surface.
Fifth reflecting surface M in rectangular shape in contact with the rear surface of portion Mb
5 is provided. The fifth reflecting surface M5 forms an angle of 45 ° with the front surface of the second portion Mb. Note that the reflection surface M4 and the reflection surface M5 are arranged at positions shifted by substantially d in the vertical direction.

The third portion Mc has a substantially inverted L-shaped outer shape as a whole. That is, the third portion Mc is composed of a pair of prismatic portions whose longitudinal directions are orthogonal to each other. One of the prism-shaped portions has one of its four side surfaces, and the second portion M
The rear surface b is arranged so as to contact from the central portion of the rear surface to the end on the fourth reflection surface M4 side. The other prismatic portion is a second portion Mb in one prismatic portion.
Are arranged so as to protrude downward from the end near the center.

A rectangular sixth reflecting surface M6 orthogonal to the reflecting surface M4 is provided at one end of the second portion Mb of the third portion Mc near the reflecting surface M4. Are formed. Further, a portion of the third portion Mc where the two prismatic portions are joined is provided with a reflection surface M of the second portion Mb.
A seventh reflecting surface M7 parallel to 3 is formed. In addition, at the lower end of the other prismatic portion of the third portion Mc,
Eighth reflection surface M8 parallel to reflection surface M1 of first portion Ma
Are formed. The reflection surface M6 and the reflection surface M7
Is arranged at a position shifted by about 2 × d in the vertical direction with respect to the reflection surface M8.

The prism M is mounted on the stage 12
1 is arranged at the monochrome drawing position, the beam axis of the first laser beam L1 substantially coincides with the center of the reflecting surface M1 and the center of the reflecting surface M8, and the second axis is arranged at the center of the reflecting surface M5. The beam axis of the laser beam L2 substantially matches, the center of the reflecting surface M4 and the center of the reflecting surface M6 substantially match the beam axis of the third laser beam L3, and the center of the second reflecting surface M2. The fourth laser beam L4 is fixed to the stage 121 such that the beam axes of the fourth laser beam L4 substantially coincide with each other.

In the state where the stage 121 is arranged at the monochrome drawing position, the beam axis of the first laser beam L1 enters the prism M from the reflection surface M1. Then, this beam axis once goes outward, enters the prism M again from the reflection surface M8, and then enters the prism M
Go outside.

The beam axis of the second laser beam L2 enters the prism M, and is bent upward by 90 ° in the plane of FIG. 11 by the reflecting surface M5. The beam axis bent by the reflecting surface M5 reaches the reflecting surface M3.
3 is bent upward by 90 ° in FIG. 10 in a plane perpendicular to both the paper surfaces of FIGS. 10 and 11. The beam axis bent by the reflection surface M3 reaches the reflection surface M4, and the reflection surface M4 causes the beam axis in FIG.
Is folded 90 ° to the left. The beam axis bent by the reflecting surface M4 reaches the reflecting surface M6, and is bent by 90 ° downward in FIG. 10 in the paper of FIG. 10 by the reflecting surface M6. The beam axis bent by the reflecting surface M6 reaches the reflecting surface M7, and is bent 90 ° toward the base plate 6 in a plane perpendicular to both the paper surfaces of FIGS. The beam axis bent by the reflecting surface M7 is
When the light reaches the reflection surface M8 and moves leftward in FIG.
It is bent at 0 °. The beam axis bent by the reflecting surface M8 comes out of the prism M.

The beam axis of the third laser beam L3 enters the prism M from the fourth reflecting surface M4 and reaches the sixth reflecting surface M6. Then, this beam axis is bent 90 ° downward in FIG. 10 in the plane of FIG. 10 by the reflecting surface M6. The beam axis bent by the reflecting surface M6 reaches the reflecting surface M7, and is bent 90 ° toward the base plate 6 in a plane perpendicular to both the paper surfaces of FIGS. The beam axis bent by the reflecting surface M7 is reflected by the reflecting surface M8.
And is bent 90 ° to the left in FIG. 11 in the plane of FIG. The beam axis bent by the reflecting surface M8 comes out of the prism M.

The beam axis of the fourth laser beam L4 enters the prism M and is bent 90 ° downward in FIG. 11 in the plane of FIG. 11 by the reflecting surface M2. The beam axis bent by the reflecting surface M2 reaches the reflecting surface M1, and FIG.
1 is bent 90 ° to the left in FIG. 11 and once out of the prism M. Further, this beam axis enters the prism M again from the reflecting surface M8,
Go out of the prism M.

As described above, the beam axis of the first laser beam L1 is not bent by the prism M,
The light passes through the prism M. Then, the beam axes of the other laser beams L2 to L4 are bent at the prism M, respectively, and exit the prism M in a state substantially coincident with the beam axis of the first laser beam L1. That is, on the rear side of the prism M on the optical path, each of the laser beams L1 to L
The beam axes of No. 4 are substantially coincident.

However, although the beam axes of these laser beams L1 to L4 are completely coincident in plan view,
They do not exactly match in side view. That is, the beam axes of these laser beams L1 to L4 are densely arranged substantially in parallel in order from the bottom to the top in a plane perpendicular to the base plate 6 so that the gaps between adjacent beam axes are uniform. Are lined up. Each beam axis is slightly inclined from a state parallel to each other in a side view.

Next, a polygon mirror section 2, an fθ lens group 3,
The folding mirror group 4 and the photosensitive drum 5 will be described. Each of the laser beams L shown in FIGS.
The optical paths 1 to L4 correspond to the stage 1 in the optical path switching unit 12.
Reference numeral 21 denotes a case in which the color printer 21 is arranged at the color drawing position.

The polygon mirror unit 2 includes a polygon mirror 2
1 and a polygon motor (not shown). The polygon mirror 21 has a substantially regular hexagonal column shape, and each side surface is formed as a reflection surface. The polygon mirror 21 has its central axis directed perpendicular to the base plate 6 and is rotatably supported about the central axis. The polygon mirror 21 is close to an end of the base plate 6 on the side opposite to the direction of the arrow x (FIGS. 1 and 2), and
At a predetermined height from the camera. The polygon mirror 21 is driven by a polygon motor and rotates counterclockwise in FIG.

The cylinder lens 1 of the light source unit 1
Each laser beam emitted from 3 is converged only in a direction perpendicular to the base plate 6 and forms an image on the base plate 6 in the form of a horizontal line segment near each reflection surface of the polygon mirror 21. This polygon mirror 21
Are rotating, the four laser beams L1 to L4 reflected by the respective reflecting surfaces are respectively
Scanning is performed in an arrow y direction (main scanning direction) in FIG.

Lens group 3 includes a first lens 31 and a second lens 32 arranged on the optical path of each of the laser beams L1 to L4 reflected by the polygon mirror 21, and a light beam emitted from the second lens 32. Each laser beam L
Third lenses 331 to 331 provided corresponding to each of 1 to L4
334. Note that the first lens 31 is
This is a lens for correcting aberration of the lens group 3. The second lens 32 has power mainly in the main scanning direction (the y direction in FIG. 1).

The third lenses 331 to 334 are fixed in elongated holding members F1 to F4, respectively. Each of these holding members F1 to F4 has a longitudinal direction indicated by y in FIG.
As they face the direction, they are arranged in order from the side away from the polygon mirror 21 to the side closer to it. Note that each of the holding members F1 to F4 is open at the upper and lower portions. In addition, each holding member F1 of the base plate 6
At the position corresponding to the lower opening of F4, a slit S
1 to S4 are formed. Note that these third lenses 331 to 334 are mainly arranged in the x direction (sub scanning direction) in FIG.
Have power.

The folding mirror group 4 is provided with laser beams L1 to L2 emitted from the second lens 32 of the fθ lens group 3.
4 are classified into a first system to a fourth system provided on each of the four optical paths. The optical paths of the laser beams L1 to L4 here are those when the stage 121 of the optical path switching unit 12 of the optical unit 1 is arranged at the color drawing position.

The first system in the folding mirror group 4 includes a mirror 411, and the second system includes a mirror 42.
1 and a mirror 422. The third system includes mirrors 431 to 433, and the fourth system includes:
It comprises mirrors 441 through 443. And f
Of the laser beams L1 to L4 emitted from the second lens 32 of the θ lens group 3, the laser beam L1 is guided to the third lens 331 by the mirror 411. The laser beam L2 is guided to the third lens 332 by the mirrors 421 and 422, and the laser beam L3 is
The laser beam L4 is guided to the third lens 334 by the mirrors 441 to 443.

The laser beams L1 to L4 guided by the folding mirror group 4 are respectively transmitted to the holding members F1
To the third lens 331 to 3
The light passes through the lower opening of each of the holding members F1 to F4, and is emitted from the slits S1 to S4 of the base plate 6 below the base plate 6. Note that the fθ lens group 3 and the folding mirror group 4 correspond to a scanning optical system.

A photosensitive layer is formed on the cylindrical surface of the four photosensitive drums 5 (51 to 54). These photosensitive drums 51 to 54 are arranged below the slits S1 to S4 of the base plate 6, respectively. That is, each of the photosensitive drums 51 to 54 is rotatably supported at the central axis so that its central axis is parallel to the longitudinal direction of each of the slits S1 to S4.

The photosensitive member section 5 is provided with the respective photosensitive drums 5.
It has a drive mechanism (not shown) connected to 1 to 54. This drive mechanism can individually drive each of the photosensitive drums 51 to 54 and rotate them around the central axis.
Further, the photoconductor section 5 has a toner supply section and a fixing section (not shown) arranged for each of the photosensitive drums 51 to 54. The photosensitive drums 51 to 54 are supplied with black, yellow, cyan, and magenta toners, respectively.

Each of the laser beams L1 to L4 reflected by the polygon mirror 21 is scanned in the y direction in FIG. 1 and passes through the first lens 31 and the second lens 32 of the fθ lens group 3. The laser beams L1 to L4 transmitted through the second lens 32 are reflected by the folding mirror group 4
The laser beams are divided for each of the laser beams L1 to L4 and enter the third lenses 331 to 334 of the fθ lens group 3, respectively. The laser beams emitted from the third lenses 331 to 334 form spots on the photosensitive drums 51 to 54, respectively.
A scanning line parallel to the central axis of the 54 is formed.

Further, the scanning optical device includes a detecting section 7 for detecting a drawing start position. The detection unit 7 includes a separation mirror 71, a condenser lens 72, and a beam detector 73.
Having.

The separation mirror 71 is the second mirror of the fθ lens group 3.
On the optical path of the laser beam L1 between the lens 32 and the mirror 411 of the folding mirror group 4, the laser beam L1 is arranged at a position deviated from the area corresponding to the scanning range on the photosensitive drum 51 in the direction of the arrow in the y direction of FIG. I have. When the polygon mirror 21 rotates counterclockwise in FIG. 1, the laser beam L1 reflected by the polygon mirror 21 is scanned in the direction opposite to the arrow in the y direction in FIG. Therefore, immediately after each reflection surface of the polygon mirror 21 starts scanning with the laser beam L1, the laser beam L1 is reflected by the separation mirror 71.

The condenser lens 72 is a cylinder lens, and is arranged on the optical path of the laser beam reflected by the separation mirror 71 with its curved generatrix directed parallel to the base plate 6. The laser beam transmitted through the first lens 31 and the second lens 32 of the fθ lens group 3 is
The light is converged only in a direction (main scanning direction) perpendicular to the beam axis and horizontal to the base plate 6, but enters the condenser lens 72 while diverging in a direction perpendicular to the base plate 6 (sub-scanning direction). This condenser lens 72
Converges the incident laser beam in the sub-scanning direction. The beam detector 73 is arranged near the image forming position of the convergent light emitted from the condenser lens 72, and detects this convergent light.

Next, a control system of the scanning optical device will be described. FIG. 13 is a block diagram schematically illustrating a control system of the scanning optical device. As shown in FIG. 13, the scanning optical device has a control unit 8 for controlling each unit of the device.
The control unit 8 includes a light source unit 11 and an optical path switching unit 12, a polygon mirror unit 2,
They are connected to the photoconductor unit 5 and the detection unit 7, respectively.

That is, the control section 8 controls each of the semiconductor lasers LD1 to LD1 in the light source section 11 via an LD drive circuit (not shown).
Each of the semiconductor lasers LD1 to LD4 is connected to D4, acquires drawing data from a higher-level device (not shown), and controls ON / OFF of each of the semiconductor lasers LD1 to LD4 according to the drawing data.

The control unit 8 is connected to a motor (not shown) in the optical path switching unit 12 via a motor drive circuit (not shown). Then, the control unit 8 rotates the motor so that the worm 122 and the worm gear 1 are rotated.
23 is rotated, and the stage 121 is slid along the guide groove G. That is, the control unit 8 controls the stage 12
1 is placed at either the color drawing position or the monochrome drawing position. The state of the optical path switching unit 12 when the stage 121 is located at the color drawing position corresponds to the first state, and the state of the optical path switching unit 12 when the stage 121 is located at the monochrome drawing position is as follows. This corresponds to the second state.

When the controller 8 places the stage 121 at the color drawing position, the laser beams L1 to L
4 travels on the optical path shown in FIG. 1 and FIG.
A spot is formed on each of the photosensitive drums 51 to 54.

However, when the control unit 8 places the stage 121 at the monochrome drawing position, all the laser beams L1 to L4 become the laser beams L in FIGS.
The light travels substantially the same as the optical path indicated by No. 1 and forms four spots close to each other on the first photosensitive drum 51.
Since the beam axes of the laser beams L1 to L4 are slightly inclined with respect to each other only in the sub-scanning direction, these spots are arranged at equal intervals on the surface of the photosensitive drum 51 in the sub-scanning direction. Here, the main scanning direction is a direction of a scanning line on the surface of the photosensitive drum 51, and the sub-scanning direction is a direction orthogonal to the scanning line on the surface of the photosensitive drum 51.

Further, the controller 8 controls the polygon mirror 2
The polygon mirror 21 is rotated at a constant speed in the counterclockwise direction in FIG. 1 by rotating the polygon motor. The control unit 8 is connected to a drive mechanism (not shown) of the photoconductor unit 5 and rotates each of the photosensitive drums 51. Further, the control unit 8 controls the beam detector 7 in the detection unit 7.
By receiving the output signal from the beam detector 73, it is possible to recognize the start of scanning performed for each reflection surface of the polygon mirror 21.

The operation of the scanning optical device configured as described above will be described below. First, the control unit 8 acquires drawing data from a higher-level device (not shown). Then, the control unit 8 determines whether the drawing data specifies color printing or monochrome printing.

When the drawing data specifies color printing, the control unit 8 controls the stage 12 of the optical path switching unit 12.
1 is arranged at the color drawing position. Also, the control unit 8
The polygon mirror 21 of the polygon mirror unit 2 is rotated at a constant speed, and the photosensitive drums 51 to 54 of the photoconductor unit 5 are rotated at a constant speed. Then, the control unit 8 controls the respective semiconductor lasers LD1 to LD1 of the light source unit 11 according to the acquired drawing data.
The LD 4 is individually turned on / off. Then, each of the semiconductor lasers LD1 to LD4 emits a laser beam L1 to L4 modulated for each corresponding color component. These laser beams L1 to L4 are respectively transmitted to the respective collimator sections C
1 to C4 to convert the light into parallel light.
The direction of the beam axis is adjusted by 4 and emitted from the light source unit 11.

Each of the laser beams L1 to L4 emitted from the light source unit 11 travels to the optical path switching unit 12, respectively. Since the stage 121 of the optical path switching unit 12 is disposed at the color drawing position, a prism T for color drawing is disposed on the optical path of each of the laser beams L1 to L4.

For this reason, the laser beam L2 is incident on the first prism Ta of this prism T, and its first reflection surface T
The light is sequentially reflected by a1 and the second reflection surface Ta2, and is emitted from the first prism Ta. The laser beam L3 enters the second prism Tb of the prism T,
The light is sequentially reflected by the first reflection surface Tb1 and the second reflection surface Tb2, and emitted from the second prism Tb. On the other hand, both laser beams L1 and L4 pass near the prism T. These laser beams L1 to L4 are emitted from the optical path switching unit 12 with their beam axes coincident in a plan view, and with a distance d between beam axes adjacent to each other in a direction perpendicular to the base plate 6 as d.

Each of the laser beams L1 to L4 emitted from the optical path switching unit 12 enters the cylinder lens 13 respectively. The cylinder lens 13 converges each of the laser beams L1 to L4 incident as parallel light only in the sub-scanning direction. Each of the laser beams L1 to L4 emitted from the cylinder lens 13 forms an image once in a line segment shape in the vicinity of the reflection surface of the polygon mirror 21.

Each of the laser beams L1 to L4 reflected by the reflection surface of the polygon mirror 21 enters the fθ lens group 3 while diverging in the sub-scanning direction. First lens 31 in this fθ lens group 3
And the laser beams L1 to L transmitted through the second lens 32
4 are emitted in a state of being converged mainly only in the main scanning direction.

The laser beam L 1 emitted from the second lens 32 is scanned in the direction opposite to the arrow in the y direction in FIG. 1 as the polygon mirror 21 rotates. Therefore, each reflection surface of the polygon mirror 21 is
Immediately after the scanning of L4 is started, the laser beam L1 is reflected by the separation mirror 71, converged by the condenser lens 72, and detected by the beam detector 73. The beam detector 73 converts the detected convergent light into an electric signal and transmits the electric signal to the controller 8.

The laser beam L1 emitted from the second lens 32 is reflected by the separation mirror 71 immediately after the scanning by the reflection surface of the polygon mirror 21 as described above, and thereafter, is scanned within a predetermined scanning range. While
Go to mirror 411. The mirror 411 reflects the laser beam L1 toward the third lens 331. Then, the laser beam L1 incident on the third lens 331 is
The light is converged mainly in the sub-scanning direction and travels toward the photosensitive drum 51. This laser beam L1 is converged by the second lens 32 in the main scanning direction, and furthermore, the third lens 3
31 converges in the sub-scanning direction. That is,
The laser beam emitted from the third lens 331 is converged in both the main scanning direction and the sub-scanning direction, and forms a spot on the photosensitive drum 51. This spot moves in accordance with the rotation of the polygon mirror 21, and forms a scanning line on the photosensitive drum 51.

Similarly, the laser beam L 2 emitted from the second lens 32 is sequentially reflected by the mirrors 421 and 422, and travels toward the third lens 332. Then, the laser beam L2 is converged in the sub-scanning direction by the third lens 332 to form a spot on the photosensitive drum 52. The spot moves on the photosensitive drum 52 in synchronization with the spot of the laser beam L1 on the photosensitive drum 51, and forms a scanning line on the photosensitive drum 52.

The laser beam L 3 emitted from the second lens 32 is sequentially reflected by the mirrors 431 to 433, and travels toward the third lens 333. Then, the laser beam L3 is converged in the sub-scanning direction by the third lens 333 to form a spot on the photosensitive drum 53. The spot moves on the photosensitive drum 53 in synchronization with the spot of the laser beam L1 on the photosensitive drum 51, and forms a scanning line on the photosensitive drum 53.

Further, the laser beam L4 emitted from the second lens 32 is sequentially reflected by each of the mirrors 441 to 443, and travels to the third lens 334. Then, the laser beam L4 is converged in the sub-scanning direction by the third lens 334 to form a spot on the photosensitive drum 54. The spot moves on the photosensitive drum 54 in synchronization with the spot of the laser beam L1 on the photosensitive drum 51, and forms a scanning line on the photosensitive drum 54.

Here, each of the photosensitive drums 51 to 54 is rotating at a constant speed. Therefore, a latent image is formed on each of the photosensitive drums 51 to 54 for each corresponding color component. Then, the toner corresponding to each color component is supplied to each of the photosensitive drums 51 to 54. In this state, the transport device (not shown) transports the paper to be printed. On the conveyed sheet, an image of toner of each color component formed on the surface of each of the photosensitive drums 51 to 54 is sequentially transferred. Further, the sheet on which the image for each color component is transferred is subjected to a heat fixing process in a fixing unit (not shown), thereby completing the color printing. The color-printed sheet is discharged to a discharge unit (not shown).

On the other hand, when the drawing data obtained from the higher-level device (not shown) specifies monochrome printing, the control unit 8 arranges the stage 121 of the optical path switching unit 12 at a monochrome drawing position. Further, the control unit 8 rotates the polygon mirror 21 of the polygon mirror unit 2 at a constant speed. Further, the control unit 8 rotates the photosensitive drum 51 of the photoconductor unit 5 at a constant speed about four times as fast as that of the above-described color drawing.

Then, the control unit 8 controls ON / OFF of each of the semiconductor lasers LD1 to LD4 of the light source unit 11 according to the obtained drawing data. Then, each semiconductor laser LD1
To LD4 emit laser beams L1 to L4 modulated for multiple beams for simultaneous writing of four lines.
That is, the laser beams L1 to L4 are modulated so as to simultaneously scan four scanning lines (four lines) on the photosensitive drum 51.

Each of these laser beams L1 to L4 is converted into parallel light by each of the collimator sections C1 to C4, and the direction of the beam axis is adjusted by each of the adjusting sections W1 to W4. Is done.

Each of the laser beams L1 to L4 emitted from the light source unit 11 travels to the optical path switching unit 12, respectively. Since the stage 121 of the optical path switching unit 12 is disposed at the monochrome drawing position, a prism M for monochrome drawing is disposed on the optical path of each of the laser beams L1 to L4.

Therefore, the laser beam L1 sequentially passes through the respective reflecting surfaces M1 and M8 of the prism M and is emitted from the prism M. The laser beam L2 is applied to each of the reflecting surfaces M5, M3, M4, M6, M7,
The light is sequentially reflected by M8, and emitted from the prism M with its beam axis substantially coincident with the beam axis of the laser beam L1. The laser beam L3 is directed to the prism M by
The light enters from the reflection surface M4, and each reflection surface M6, M7, M8
, And its beam axis is changed to the laser beam L.
The light is emitted from the prism M so as to be substantially coincident with the beam axis 2. The laser beam L4 is sequentially reflected by the reflecting surfaces M2 and M1 of the prism M, passes through the reflecting surface M8, and is emitted from the prism M with its beam axis substantially coincident with the beam axis of the laser beam L3. .

That is, each of the laser beams L1 to L4 is emitted from the optical path switching unit 12 and substantially enters the cylinder lens 13 with their beam axes substantially coincident. The cylinder lens 13 is provided with laser beams L1 to L
4 is converged only in the sub-scanning direction. Each of the laser beams L1 to L4 emitted from the cylinder lens 13
Form an image once in a line segment shape near the reflection surface of the polygon mirror 21. Each of the laser beams L1 to L4
FIG. 1 and FIG.
Travels along the optical path shown as the optical path of the laser beam L1 in FIG.

Each of the laser beams L1 to L4 reflected by the reflection surface of the polygon mirror 21 enters the fθ lens group 3 while diverging in the sub-scanning direction. The laser beams L1 to L4 transmitted through the first lens 31 and the second lens 32 in the fθ lens group 3 are:
Each of them is emitted in a state of being converged mainly only in the main scanning direction.

The laser beams L1 to L4 emitted from the second lens 32 are scanned in the direction opposite to the arrow y in the y direction in FIG. Therefore, immediately after each reflection surface of the polygon mirror 21 starts scanning with each of the laser beams L1 to L4, each of the laser beams L1 to L4 is reflected by the separation mirror 71,
The beam is converged by the condenser lens 72 and is
3 is detected. The beam detector 73 converts the detected convergent light into a signal and transmits the signal to the controller 8.

Each of the laser beams L1 to L4 emitted from the second lens is reflected by the separation mirror 71 immediately after the scanning by the respective reflection surfaces of the polygon mirror 21, but thereafter, within a predetermined scanning range. While scanning is performed, the mirror heads toward the mirror 411. This mirror 411 is
The laser beams L1 to L4 are respectively reflected toward the third lens 331. Each of the laser beams L1 to L4 incident on the third lens 331 is converged mainly in the sub-scanning direction and travels toward the photosensitive drum 51. Each laser beam L
1 to L4 are converged in the main scanning direction by the second lens 32 and further converged in the sub-scanning direction by the third lens 331 to form spots on the photosensitive drum 51, respectively.

These spots are uniformly arranged on the photosensitive drum 51 in the sub-scanning direction. These spots move in the main scanning direction together with the rotation of the polygon mirror 21, and
Four scanning lines are formed on and parallel to each other in close proximity to each other.

Therefore, each of the laser beams L1 to L4 is
Four lines on the photosensitive drum 51 are simultaneously drawn. Since the photosensitive drum 51 is rotating at a higher speed than at the time of color printing, a latent image for monochrome printing is quickly formed on the surface thereof. Then, black toner is supplied to the photosensitive drum 51. In this state, the transport device (not shown) transports the paper to be printed. The image formed by the black toner formed on the surface of the photosensitive drum 51 is transferred to the conveyed sheet. Further, the sheet on which the image has been transferred is subjected to a heat fixing process in a fixing unit (not shown), thereby completing the monochrome printing. The monochrome printed sheet is discharged to a discharge unit (not shown).

As described above, when receiving the drawing data designating monochrome printing, the control unit 8 simultaneously performs multi-beam drawing for four lines on the photosensitive drum 51, and performs high-speed monochrome printing on the photosensitive drum 51. Is formed. Therefore, this scanning optical device can not only execute color printing at high speed by a so-called tandem method, but also execute monochrome printing at a higher speed by so-called multi-beam scanning.

[0103]

According to the scanning optical apparatus of the present invention constructed as described above, not only can each laser beam be simultaneously scanned on each photosensitive member, but an image can be formed on each photosensitive member. By changing the optical path of the laser beam by the optical path switching unit, a plurality of lines can be simultaneously drawn on a certain photoconductor. When a plurality of lines are simultaneously drawn, the speed of image formation on the photoconductor is increased.

[Brief description of the drawings]

FIG. 1 is a plan view showing a scanning optical device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a plan view of a light source unit and an optical path switching unit during monochrome drawing.

FIG. 4 is an explanatory view schematically showing a state where a semiconductor laser, a collimator section, and an adjustment section are viewed from a plane.

FIG. 5 is a view of FIG. 4 as viewed in the direction of arrow V;

FIG. 6 is a view of FIG. 5 in the direction of arrow VI.

FIG. 7 is a plan view of a light source unit and an optical path switching unit during color drawing.

FIG. 8 is a plan view showing a prism for color drawing.

FIG. 9 is a view of FIG. 8 as viewed in the IX direction.

FIG. 10 is a plan view showing a prism for monochrome drawing.

FIG. 11 is a view of FIG. 10 viewed in the XI direction.

FIG. 12 is a perspective view of a prism for monochrome drawing.

FIG. 13 is a block diagram schematically showing a control system.

[Explanation of symbols]

Reference Signs List 1 light source unit 11 light source unit 12 optical path switching unit 2 polygon mirror unit 3 fθ lens group 31 first lens 32 second lens 331-334 third lens 4 mirror group 411, 421, 422, 431-433, 441-4
43 mirror 51-54 photosensitive drum 8 control unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/113 H04N 1/04 104A 9A001 F term (Reference) 2H045 AA01 BA02 BA22 BA32 BA34 CA63 DA02 DA04 2H087 KA19 LA22 RA41 5C051 AA02 CA07 DA02 DA09 DB22 DB23 DB24 DB30 DC02 DC04 EA01 5C072 AA03 BA03 DA02 DA04 DA10 HA02 HA06 HA09 HA13 HB08 QA14 XA05 5F073 BA07 EA29 FA30 9A001 BB06 HH31 KK16 KK42

Claims (9)

[Claims] 1. A light source unit for emitting a plurality of laser beams so as to be arranged at regular intervals in a predetermined direction, and separating each laser beam emitted from the light source unit into a plurality of spatial regions in the predetermined direction. An optical path switching unit that switches between a first state in which light is guided by the optical path and a second state in which light is guided densely in any of the spatial regions; and a plurality of laser beams guided by the optical path switching unit. A deflecting unit for simultaneously deflecting and scanning in a direction orthogonal to a predetermined direction; and converging the respective laser beams deflected and scanned by the deflecting unit. A scanning optical system for guiding the light onto a photoconductor corresponding to the region. A first prism for receiving the plurality of laser beams emitted from the light source unit and arranging the plurality of laser beams at a predetermined distance from each other in the predetermined direction; A second prism into which a plurality of laser beams emitted from the light source unit enter and are arranged in a state of being arranged close to each other in the predetermined direction, and the first prism is arranged in the first state. A switching mechanism arranged on the optical path of each laser beam emitted from the light source unit, and in the second state, the second prism arranged on the optical path of each laser beam emitted from the light source unit. The scanning optical device according to claim 1, wherein: 3. The scanning optical system according to claim 1, wherein the optical path switching unit is a first optical path switching unit.
In the state of, each laser beam guided by the optical path switching unit and deflected and scanned by the deflecting unit, form an image on each photoconductor, respectively, to form a scanning line on the photoconductor,
When the optical path switching unit is in the second state, each laser beam guided by the optical path switching unit and deflected and scanned by the deflecting unit forms an image on one of the photoconductors, and 3. The scanning optical device according to claim 1, further comprising a scanning lens for forming a plurality of scanning lines arranged close to each other on a body. 4. A scanning lens of the scanning optical system, comprising: a front lens group for transmitting both laser beams deflected and scanned by the deflection unit; and a plurality of rear lens groups arranged corresponding to each photoconductor. A lens, and the scanning optical system is configured to, when the optical path switching unit is in the first state, transmit each laser beam emitted from the front group lens to a rear group lens corresponding to a position in the predetermined direction. Light guiding means for guiding each of the laser beams emitted from the front group lens together with one of the rear group lenses when the optical path switching unit is in the second state.
The scanning optical device according to claim 3, further comprising: 5. The scanning optical apparatus according to claim 4, wherein said deflecting unit has a polygon mirror, and said scanning lens is an fθ lens including a front group lens and a rear group lens. 6. The scanning optical device according to claim 4, wherein said light guide means is a mirror group comprising a plurality of mirrors. 7. Each of the photoconductors is a photoconductive drum having a surface equivalent to a cylindrical surface, and each of the photoconductors corresponds to each of yellow, magenta, cyan and black color components for forming a color image. The scanning optical system is provided so as to be rotatable about a central axis, and the scanning optical system forms a scanning line in a direction parallel to the central axis on the surface of the photosensitive drum. Scanning optics. 8. The scanning optical device according to claim 7, wherein said light source section has four light sources for emitting a laser beam. 9. When forming a color image, the optical path switching means is set to a first state, and each light source is made to correspond to a color component of each photosensitive drum arranged on an optical path of a laser beam emitted from the light source. The photosensitive drums are rotated at the same speed, and when forming a monochrome image, the optical path switching means is set to the second state, and the light sources are placed on the optical path of the laser beam emitted by the light sources. Modulation is performed in correspondence with a plurality of scanning lines arranged in close proximity on one arranged photosensitive drum, and the photosensitive drum on which each of these scanning lines is formed is rotated at a higher speed than when forming a color image. 9. The scanning optical device according to claim 8, further comprising a control unit that controls the scanning.