JP2001125021A - Light beam scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light beam scanner which can be made compact by simplifying a 1st optical system. SOLUTION: Laser beams LB1 and LB2 emitted from laser diodes LD1 and LD2 are collimated to luminous flux width being wider than the surface width of the deflection surfaces M1-M12 of a polygon mirror from a diffusion state in common by the collimator lens 63A of the 1st optical system 6A. Then, the beams LB1 and LB2 emitted from the diodes LD1 and LD2 are synthesized so as to be advanced in the direction of the lens 63A with a slight angle by a beam splitter 61. The splitter 61 is disposed halfway the optical path of the laser beams which is not collimated to the above luminous flux width yet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam scanning device used in a laser printer or the like, and more particularly, to a multi-beam type light beam scanning device for simultaneously scanning a plurality of beams.

[0002]

2. Description of the Related Art In a light beam scanning device used in an image forming apparatus such as a laser printer or a digital copying machine, the rotation speed of a polygon mirror is increased in order to meet the demand for higher image forming speed and higher resolution. Also, the number of deflection surfaces of the polygon mirror has been increased, and multi-beams have been achieved.

The light beam scanning apparatus has an under-filled optical system (hereinafter referred to as an under-filled optical system) in which a light beam narrower in the rotation direction (main scanning direction) than the width of the deflecting surface is incident on the deflecting surface of the rotating polygon mirror. Hereinafter, this will be simply referred to as “underfilled optical system”) and an overfilled optical system (hereinafter simply referred to as “overfilled optical system”) that receives a light beam having a light beam width wider than the surface width of the deflection surface in the main scanning direction. system"
It is written. ). In an underfilled optical system, the surface width of the deflecting surface must be formed wider than the light beam width of the incident light beam. Increasing the number of surfaces from 12 to 12 doubles the diameter of the inscribed circle of the polygon mirror, increasing the size and increasing the weight.
The practical limit is about eight surfaces. On the other hand, in the overfilled optical system, since the light beam is incident on the entire surface width of the deflecting surface, the surface width of the deflecting surface can be made substantially the same as the light beam width of the deflected light beam. Without increasing the size and weight of the polygon mirror as in the system, the number of surfaces is, for example, 6 to 12 (in the maximum,
There is an advantage that it can be increased to about 16).

FIG. 7 shows a conventional example of a light beam scanning apparatus which employs such an overfilled optical system and realizes multi-beams. FIG. 7 is a perspective view showing a schematic configuration of a multi-beam overfilled light beam scanning device used in a conventional laser printer 100. As shown in FIG.
Includes a photosensitive drum 200 that is driven to rotate in the direction of arrow a (sub-scanning direction), and a laser beam scanning device 300. The laser beam scanning device 300 has a laser beam LB100,
Laser diode LD1 for emitting LB200 respectively
00, LD 200, a beam splitter 500 formed by bonding two triangular prisms, a first optical system 800, a second optical system 700, and the like.

The polygon mirror 400 has a plurality of (12 in the illustrated example) deflecting surfaces around the polygon mirror 400, and is formed in a prism shape having a diameter of an inscribed circle of about 20 to 40 mm. The surface width of each deflection surface in the main scanning direction is set to, for example, 5 to 10 mm. Laser diodes LD100, LD200
Are respectively driven by drive signals based on image data output from a controller (not shown), and emit light-modulated laser beams LB100 and LB200 at predetermined beam divergence angles.

FIG. 8 is a diagram showing a detailed configuration near the first optical system 800 shown in FIG. In FIG. 8,
Illustration of the lens barrels 811 and 821 is omitted. The first optical system 800 is attached to a lens barrel 811 (see FIG. 7), and is attached to a collimator lens 814 having positive power in the main scanning direction and the sub-scanning direction, and a lens barrel 821 (see FIG. 7). A collimator lens 824 having a positive power in the main scanning direction and the sub-scanning direction, a beam splitter 830 obtained by bonding two triangular prisms, and a lens 840 having a cylindrical surface and having a positive power in the sub-scanning direction. Consists of The collimator lens 804 is composed of two lenses 8
12, 813 and the collimator lens 82
Reference numeral 4 denotes two lenses 822 and 823.

A laser beam LB100 emitted from one laser diode LD100 is applied to a first optical system 800
The light beam width (2 to 3 of the underfilled optical system) wider than the deflection surface in the main scanning direction by the collimator lens 814
When the light is diffused up to twice (for example, 20 mm), it is collimated from the diffused state to the parallel state. Laser beam LB200 emitted from the other laser diode LD200
Is incident on the collimator lens 824 and diffuses to the same light beam width of 20 mm as the laser diode LD100, and is collimated from the diffused state to the parallel state.

[0008] The laser beams LB100 and LB200 collimated to the above light beam width are incident on the beam splitter 830 at an angle of about 90 ° to each other. The beam splitter 830 deflects the laser beam LB100 by 90 ° on the bonding surface, and the laser beam LB20
By passing 0 as it is, the images are synthesized so as to travel in the same direction at a slight angle. Laser beams LB100 and LB synthesized by beam splitter 830
The beam splitter 200 shown in FIG. 7 is condensed by the lens 840 only in the sub-scanning direction.
Go to zero.

The laser beams LB100 and LB200 are
The beam is deflected by 90 ° by the beam splitter 500, is incident on the deflection surface of the polygon mirror 400, and is scanned in the main scanning direction as the polygon mirror 400 rotates. Thereafter, the laser beams (scanning beams) LB100, LB20
0 passes through the beam splitter 500 again, and the two fθ lenses 701 and 70 of the second optical system 700 respectively.
2 and a lens 703 having a cylindrical surface, pass through a scanning lens 704, are deflected by a return mirror 705, and spot the surface of the photosensitive drum 200 adjacent to each other at a predetermined interval in the sub-scanning direction. Exposure scanning is performed in the main scanning direction while the light is condensed.

According to the light beam scanning device configured as described above, two laser beams LB100 and LB200, which are wider in the main scanning direction than the surface width of the deflecting surface, are irradiated on the deflecting surface. Therefore, the number of scanning lines on the photosensitive drum surface during one rotation of the polygon mirror 400 can be increased to twice the number of deflecting surfaces, which is suitable for increasing the image forming speed and increasing the resolution. ing.

[0011]

However, in the above-mentioned prior art, as shown in FIG. 8, laser beams LB100 and LB200 emitted from laser diodes LD100 and LD200 are collimated by a collimator lens 814.
At 824, the light beams are individually collimated into a predetermined light beam width, and after the collimation, the beam splitter 830 combines the principal rays of the laser beams LB100 and LB200 so as to travel in the same direction at a small angle. For this reason, two sets of large collimator lenses are required, and a large beam splitter 830 having a side of about 30 mm must be arranged between each collimator lens 814 and 824 and the polygon mirror 400. There is a problem that one optical system 800 is enlarged.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a light beam scanning apparatus which simplifies the first optical system and realizes a compact apparatus.

[0013]

In order to solve the above-mentioned problems, a light beam scanning apparatus according to the present invention comprises a polygon mirror which rotates light beams emitted from a plurality of light sources via a first optical system. Main scanning while irradiating each light beam deflected by the deflecting surface on the surface to be scanned via the second optical system so as to be adjacent to each other at a constant interval in the sub-scanning direction. A light beam scanning device that scans in a direction, wherein the first optical system collimates each of the light beams emitted from each of the light sources into a light beam width wider than the deflection surface in the main scanning direction; Light synthesizing means for synthesizing each light beam emitted from the light source so as to travel in the same direction at a slight angle, and wherein the light synthesizing means is arranged in the middle of the optical path before being collimated to the light flux width. There is And it features.

Further, the light beam scanning device according to the present invention comprises:
The collimator may include a single or a plurality of lenses disposed in an optical path between the light combiner and the polygon mirror. Further, in the light beam scanning device according to the present invention, the collimating unit may include a first lens disposed in an optical path between each of the light sources and the light combining unit, and a first lens disposed between the light combining unit and the polygon mirror. And a second lens disposed in the optical path.

Further, the light beam scanning device according to the present invention comprises:
The optical axis of the first optical system and the optical axis of the second optical system are substantially included in the same plane including the rotation axis of the polygon mirror. Further, in the light beam scanning device according to the present invention, the first optical system and the second optical system may be configured such that the plurality of light beams synthesized by the light synthesizing unit are partially or entirely included in a lens group of the second optical system. Are arranged so as to irradiate the deflecting surface of the rotating body through the lens, and collimate each light beam at least in the main scanning direction via a lens that has passed when the light beam is incident on the deflecting surface. Accordingly, a part or all of the collimating means is replaced by the passed lens.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Embodiment 1 Hereinafter, an example in which a multi-beam overfilled light beam scanning device according to Embodiment 1 of the present invention is applied to a laser printer will be described with reference to the drawings. I do.

FIG. 1 is a perspective view showing a schematic configuration of an optical system of a laser printer according to Embodiment 1 of the present invention. In FIG. 1, only the principal rays (the rays having the highest light intensity) of the laser beams LB1 and LB2 are drawn as straight lines.
As shown in FIG. 1, a laser printer 1 includes a photosensitive drum 2 that is driven to rotate at a predetermined angular velocity in a direction indicated by an arrow a (sub-scanning direction), and two photosensitive drums 2 (surfaces to be scanned). A laser beam scanning device 3A for scanning with the laser beams LB1 and LB2 is provided.

The laser beam scanning device 3A emits laser beams LB1 and LB2 around a polygon mirror 4 driven at high speed in the direction of arrow b (main scanning direction) at a constant angular velocity by a polygon motor (not shown). Diodes LD1 and LD2, beam splitter 5 formed by bonding two triangular prisms, laser diode LD
1, a first optical system 6 disposed in the optical path of the laser beams LB1, LB2 between the LD2 and the beam splitter 5.
A, a second optical system 7 disposed in the optical path of the laser beams LB1 and LB2 between the beam splitter 5 and the photosensitive drum 2, and the like.

The polygon mirror 4 has a plurality of (12 in the illustrated example) deflecting surfaces M1 to M12 (see FIG. 3) around the polygon mirror 4, and is formed in a prism shape having a diameter of an inscribed circle of about 25 to 40 mm. I have. The surface width of each of the deflection surfaces M1 to M12 in the main scanning direction is set to, for example, about 6 to 10 mm. The laser diodes LD1 and LD2 are respectively driven by drive signals based on image data output from a control unit (not shown), and light-modulated laser beams LB1 and LB2.
Are emitted at predetermined beam divergence angles. Note that the laser beam LB1 is optically modulated by image data of an odd line constituting one image, and the laser beam LB2 is optically modulated by image data of an even line.

FIG. 2 is a diagram showing a detailed configuration near the first optical system 6A. 2, illustration of the lens barrel 62 is omitted. The first optical system 6A is disposed at a position equidistant from the two laser diodes LD1 and LD2, and is attached to a beam splitter 61 (light combining means) formed by bonding two triangular prisms and a lens barrel 62. A collimator lens 63A having a positive power in the main scanning direction and the sub-scanning direction and having a single lens, and a lens 64 having a cylindrical surface and having a positive power only in the sub-scanning direction.

Returning to FIG. 1, the second optical system 7 has two fθ lenses 71 and 72 having a positive power in the main scanning direction and a lens having a cylindrical surface and having a positive power in the sub-scanning direction. 73 and a folding mirror 75. The fθ lenses 71 and 72 and the lens 73 constitute a scanning lens 74. Here, the optical axis of the first optical system 6A,
The optical axis of the second optical system 7 is configured to be substantially included in one plane including the rotation axis of the polygon mirror 4 via the beam splitter 5 (this configuration is referred to as The angle between the optical axis of the first optical system 6A and the optical axis of the second optical system 7 is set to substantially 0 °, and the laser beams LB1 and LB2 are directed to the polygon mirror 4 with respect to the optical axis of the second optical system. Hereinafter, it is referred to as “0 ° incidence” in the sense that the light is incident at substantially 0 °.)

As shown in FIG. 2, the laser beams LB1 and LB2 emitted from the laser diodes LD1 and LD2 enter the beam splitter 61 of the first optical system 6A in a diffused state, respectively. The beam splitter 61 deflects the laser beam LB1 by 90 ° on the bonding surface and passes the laser beam LB2 as it is, thereby combining the two laser beams LB1 and LB2 so as to be directed toward the collimator lens 63A at a slight angle. . The laser beams LB1 and LB2 synthesized by the beam splitter 61 have a predetermined light flux width (2 to 3 of the underfilled optical system) wider than the surface width of the deflection surfaces M1 to M12.
(For example, 20 mm), the light is collimated into parallel light by the collimator lens 63A. The laser beams LB1 and LB2 collimated by the collimator lens 63A travel toward the beam splitter 5 while being condensed in the sub-scanning direction by the lens 64.

In the beam splitter 5, the two laser beams LB1 and LB2 are deflected by 90 ° and are incident on the deflection surface of the polygon mirror 4 wider than the surface width in the main scanning direction. In the sub-scanning direction, the laser beams LB1 and LB2 are condensed linearly near the deflection surface of the polygon mirror 4 by the condensing power of the lens 64.

FIG. 3 is a view showing the detailed configuration of the polygon mirror 4 and its vicinity. The laser beams LB1 and LB2 incident on the polygon mirror are cut off by the deflecting surface with the rotation of the polygon mirror because the laser beam scanning device 3A is an overfield optical system, and the light beam width is substantially equal to the surface width of the deflecting surface. Is deflected by Here, the optical axis of the first optical system 6 is L1, and the optical axis of the second optical system 7 is L1.
If the angle is 2, the optical axes L1 and L2 coincide with the main scanning direction under 0 ° incidence, and the angle between these optical axes L1 and L2 is “0 °”. The normal line of the deflecting surface M1 is set to N, and the angle between the optical axis L1 of the first optical system 6 and the normal line N of the deflecting surface M1 (deflection surface incident angle) δ is 0 °. 2. An image forming center position for forming an image at the center of
This is referred to as “COI”. COI: Center of Im
age. In FIG. 3B, the case where the normal line N is deviated from the optical axis L1 by −δm (= 12.5 °) in the main scanning direction is referred to as an image formation start position (hereinafter, referred to as “SOI”).
OI: Startof Image. See FIG. ), The normal line N is + δ in the main scanning direction from the optical axis L1.
An image formation end position (hereinafter, referred to as “EOI” when the image is shaken by m (= 12.5 °). EOI: End of
Image. FIG. 3C). Then, the incident angle δ of the deflecting surface, the principal rays of the laser beams (scanning beams) LB1 and LB2 deflected by the deflecting surface and the second
The angle (deflection angle) in the main scanning direction between the optical system 7 and the optical axis L2.
The relationship of δ = (θ / 2) holds between θ and θ.
Further, the cutout width D of the incident beam LB1 by the deflecting surface M1 is proportional to the cosine of the deflecting surface incident angle δ.
When the width in the main scanning direction of D.1 is D0 (10 mm), D
= D0 · cosδ, and the scanning beam LB
1, LB2 equal to the light beam width in the main scanning direction.

For this reason, the incident beam L by the deflection surface M1
As for the cutting width D of B1 and LB2, the cutting width D2 at the position of the COI becomes the maximum (D2 = D0 = 10 mm), and S
The cutout widths D1 and D3 (about 9.8 mm) at the positions of OI and EOI are minimized. As a result, SOI, CO
I. The difference between the cutout widths in each state of the EOI is extremely small. Therefore, the fluctuation of the cut width in one scanning cycle is extremely small. It should be noted that such a small change in the cutting width is the effect of the configuration at 0 ° incidence. Therefore, in the case of incidence at 0 °, there is an advantage that the unevenness of the light amounts of the scanning beams LB1 and LB2 in one scan is extremely small.

On the other hand, α (for example, 45 to 90)
In the case of high incidence, the cutout width D of the incident beam by the deflecting surface is expressed by the formula D = D0 · cos (δ + α), and cos (δ + α) greatly fluctuates between 0 and 1. As a result, SOI, COI. The variation of the cutting width at each position of the EOI is extremely large. Therefore, in the case of α ゛ incidence, the unevenness of the light amount of the scanning beam in one scan becomes extremely large.

Laser beam (scanning beam) LB after deflection
1 and LB2 pass through the beam splitter 5 again and then pass through the scanning lens 74 shown in FIG.
The light is deflected by the turning mirror 75 and condensed in a spot shape at a predetermined interval, and at the same time, the main scanning of the photosensitive drum 2 is performed. At this time, the beam interval between the centers of the beam spots of the laser beams LB1 and LB2 condensed on the photosensitive drum 2 is 42.3 μm, which corresponds to a print resolution of 600 dpi. .

The lens 73 cooperates with the lens 64 to minimize the deviation of the scanning line in the sub-scanning direction due to the tilt of the deflecting surfaces M1 to M12 of the polygon mirror 4, and to make the scanning line straight. The focus position of the scanning beam is corrected so that Around the photosensitive drum 2,
A cleaner (not shown), an eraser lamp, a charging charger, a developing device, a transfer charger, and the like are provided. Before the photosensitive drum 2 is exposed to the laser beams LB1 and LB2, the residual toner on the surface of the photosensitive member is removed by a cleaner, and the photosensitive drum 2 is irradiated with an eraser lamp to be neutralized, and then uniformly charged by a charging charger. When exposure is performed in such a uniformly charged state, an electrostatic latent image is formed on the photoconductor on the surface of the photoconductor drum 2. This electrostatic latent image is visualized as a toner image by receiving a supply of toner from a developing device. The toner image is transferred onto a recording sheet fed from a sheet feeding unit (not shown) by electrostatic force between a drum and a transfer charger in synchronization with the image forming operation, and then transferred to a fixing roller (not shown). Be established. Thus, the image formation based on the image data is completed.

According to the light beam scanning apparatus 3A of the multi-beam overfilled scanning type configured as described above, the laser beam which is wider in the main scanning direction than the surface width of the deflecting surface is sequentially applied to each of the deflecting surfaces. Since LB1 and LB2 are radiated two by two, the number of scanning lines during one rotation of the polygon mirror 4 can be reduced to twice the number of deflecting surfaces without increasing the diameter of the inscribed circle. It is suitable for increasing the image forming speed and increasing the resolution.

Further, the laser beams LB1 and LB2 combined by the beam splitter 61 of the first optical system 6A are collimated from the diffused state to the parallel light by the collimator lens 63A in common, so that one collimator lens can be used. . In addition, laser diodes LD1, LD
Since the laser beams LB1 and LB2 emitted from the beam splitter 2 are combined by the beam splitter 61 at the stage of diffused light having a smaller light flux width than that of the laser beam reaching the collimator lens 63A, the beam splitter 61 is reduced in size to about 5 mm per side. Can be. Therefore, the first optical system 6A including the beam splitter 61 despite the multi-beam conversion is used.
Can be downsized to the same extent as in the case of a single beam, and the laser beam scanning device 3A can be downsized.

In the conventional light beam scanning device shown in FIGS. 7 and 8, laser beams LB100 and LB20 are used.
0 was individually collimated into wide beams by the collimator lenses 814 and 824,
If at least one of 14, 824 is displaced due to an environmental change, the writing positions of the laser beams LB100 and LB200 are individually displaced, and the interval may be changed.
On the other hand, according to the configuration according to the first embodiment, the individual arrangement of the collimator lenses which caused the positional deviation of the writing position of the laser beams LB1 and LB2 is eliminated, and the collimator lens 63A is reduced to one. Therefore, even if the collimator lens 63A is displaced due to environmental fluctuation, the writing positions of the laser beams LB1 and LB2 are displaced integrally. As a result, the laser beam LB
There is also an effect that the deviation of the interval between the writing positions of 1 and LB2 can be kept small.

(2) Second Embodiment FIG. 4 shows a laser beam scanning device 3B according to a second embodiment.
FIG. 5 is a plan view showing a first optical system 6B and a configuration around the first optical system 6B. The same components as those in the first embodiment are denoted by the same reference numerals, description thereof will be omitted, and only different portions will be described. In the first optical system 6A of the first embodiment, the collimator lens 63A is constituted by one lens, but in the first optical system 6B of the second embodiment,
The collimator lens 63B is constituted by the lenses 630 and 631, and the laser beams LB1 and LB2 combined by the beam splitter 61 are changed from the diffused state to the parallel state by the lenses 630 and 631 in common.

According to the second embodiment, the first optical system 6
B collimator lens 63B into two lenses 630, 6
Since the number of lenses is 31, the number of lenses is increased and the cost is slightly increased as compared with the case of the first embodiment. However, as in the case of the first embodiment, there is an effect that the size can be reduced as compared with the conventional structure. As well as both laser beams LB1, L
There is also an effect that B2 can be brought into a parallel state with less aberration over the entire light beam width.

(3) Third Embodiment FIG. 5 shows a laser beam scanning device 3C according to a third embodiment.
FIG. 5 is a plan view showing a first optical system 6C and its vicinity. The same components as those in the first and second embodiments are denoted by the same reference numerals, and description thereof will be omitted. Only different portions will be described. The first optical system 6A of the first and second embodiments,
6B, the laser beams LB1 and LB2 synthesized by the beam splitter 61 are collimated by a collimator lens 63.
A and 63B are commonly used to convert the diffused state to parallel light.

On the other hand, in the first optical system 6C according to the third embodiment, a lens 632 individually disposed in the optical path of the laser beam LB1 between the laser diode LD1 and the beam splitter 61; Beam splitter 6
1 and the lens 634 disposed in the optical path of the laser beams LB1 and LB2 between the lens 64 and the laser beam L
A collimator lens 63aC for B1 and a lens 633 separately provided in the optical path of the laser beam LB2 between the laser diode LD2 and the beam splitter 61, and the lens 634 for the collimator lens for the laser beam LB2. 63bC.

According to the third embodiment, although the number of lenses is further increased as compared with the first and second embodiments, the cost is increased, but the effect that the size can be reduced as compared with the conventional configuration can be obtained. And the laser diode L
Laser beams LB1 and LB emitted from D1 and LD2
Even if there is a difference between the two aberration situations, the difference can be corrected individually, and there is an effect that both laser beams LB1 and LB2 can be brought into a parallel state with little aberration over the entire light beam width.

(4) Fourth Embodiment FIG. 6 is a diagram showing a first optical system 6D of a laser beam scanning device 3D according to a fourth embodiment and a schematic configuration around the first optical system 6D. In particular, FIG. FIG. 6B is a plan view showing one optical system 6D and a configuration in the vicinity thereof, and FIG. 6B is a side view thereof. The same components as those in the first to third embodiments are denoted by the same reference numerals, the description thereof will be omitted, and only different portions will be described in detail. The illustration of the folding mirror 75 of the second optical system 7 is omitted.

In the first to third embodiments, the first optical system 6A and the second optical system 7 are individually configured, and the beam splitter 5 is used to make the incident light at 0 °. On the other hand, in the fourth embodiment, the first optical system 6
D and the second optical system 7, the laser beams LB 1 and LB 2 combined by the beam splitter 61
By arranging them so as to irradiate the deflection surfaces M1 to M12 of the polygon mirror 4 through the fθ lenses 71 and 72 which are part of the scanning lens 74 of FIG.
と し Make the laser beams LB1 and LB2 incident on the deflection surface M
F71 lenses 72, 72 that have passed through upon incidence on 1-M12
In the main scanning direction, the fθ lenses 71 and 72 pass through to replace a part of the collimator lens 63D.

More specifically, in the fourth embodiment, the beam splitter 5 is omitted, and the optical axis of the first optical system 6D and the optical axis of the second optical system 7 are The polygon mirror 4 is arranged in such a positional relationship that the angle difference in the scanning direction becomes small.
The laser beam L is transmitted twice: when the laser beam is incident on the M12 substantially from the front, and when the laser beam is reflected by the deflection surfaces M1 to M12.
B1 and LB2 pass through the fθ lenses 71 and 72. Note that the laser diodes LD1 and LD2 of the first optical system 6D do not shield the scanning beam from light.
The laser beams LB1 and LB2 have an angle ω slightly upward with respect to a plane orthogonal to the rotation axis of the polygon mirror 4.
(See FIG. 6B).

In the first optical system 6D, a lens 634 individually disposed in the optical path of the laser beam LB1 between the laser diode LD1 and the beam splitter 61,
The fθ lenses 71 and 72 of the second optical system 7 disposed in the optical paths of the laser beams LB1 and LB2 between the beam splitter 61 and the polygon mirror 4 and the laser beam LB1
And a collimator lens 63aD for
The lens 635 individually disposed in the optical path of the laser beam LB2 between the laser diode LD2 and the beam splitter 61 and the fθ lenses 71 and 72 constitute a collimator lens 63bD for the laser beam LB2.

For this reason, the laser diodes LD1, LD
The laser beams LB1 and LB2 emitted from the laser beam 2 enter the beam splitter 61 at an angle of about 90 ° in a diffused state via the lenses 634 and 635, respectively, and the main splitter beams are slightly diffused by the beam splitter 61. The images are synthesized so as to be directed toward the lens 64 at an angle. After passing through the lens 64, the laser beams LB1 and LB2 synthesized by the beam splitter 61 are diffused to a predetermined light beam width wider than the surface width of the deflecting surface by the condensing power in the main scanning direction of the fθ lenses 71 and 72. Meanwhile, the light is collimated from the diffused state to the parallel state, and is incident on the polygon mirror 4 from the front.

According to the fourth embodiment, since the beam splitter 5 can be omitted, the cost can be reduced accordingly. Further, in the first to third embodiments, when the beam splitter 5 enters the polygon mirror 4, the light intensity of the laser beams LB 1 and LB 2 is almost half wasted, and when the laser beam LB 1 is reflected from the polygon mirror 4, Since the light intensity of LB2 is almost half wasted,
Although the energy efficiency of the laser beams LB1 and LB2 is low, according to the fourth embodiment, since the beam splitter 5 can be omitted, the energy efficiency can be improved. Further, the fθ lens 7 of the second optical system 7
Collimator lenses 63aD and 63b using
D, the first optical system 6D has an fθ lens 7
It has the same light condensing power in the main scanning direction as 1, 72, and can substantially reduce the number of collimating lenses having a diameter larger than a predetermined light beam width. Thus, the configuration of the first optical system 6D and, consequently, laser beam scanning The configuration of the device 3D can be reduced in cost and size.

(5) Modifications Although the light beam scanning device according to the present invention has been described based on the embodiments, it goes without saying that the content of the present invention is not limited to the above embodiments. The following modifications are possible. (5-1) In the above embodiment, the beam splitter 61 is used as the light combiner, but a half mirror or the like can be used. Further, a half mirror or the like can be used instead of the beam splitter 5.

(5-2) In the above embodiment,
The two laser beams are applied to the deflection surfaces M1 to M1 of the polygon mirror 4.
Although the laser beam is applied to the M12, three or more laser beams may be sequentially applied to each of the deflection surfaces with a light beam width wider in the main scanning direction than the surface width of the deflection surface. (5-3) In the above embodiment, the number of deflecting surfaces of the polygon mirror 4 is set to 12, but may be set to any other number in a practical range such as 16 surfaces.

(5-4) In the fourth embodiment, the light passes through the fθ lenses 71 and 72 of the second optical system 7. M12 may be irradiated,
The light may be irradiated only on the deflection surfaces M1 to M12 of the polygon mirror 4 by passing through only the fθ lens 71. (5-5) Furthermore, in the above-described embodiment, the present invention is applied to a laser printer.
The present invention can also be applied to an image forming apparatus such as a micro reader print and a multifunction peripheral thereof.

[0046]

As described above, according to the light beam scanning device of the present invention, the first optical system converts each of the light beams emitted from each of the light sources into a light beam wider than the deflection surface in the main scanning direction. Collimating means for collimating to a width, and light combining means for combining each light beam emitted from each light source so as to travel in the same direction at a slight angle, and in the middle of the optical path before being collimated to the light beam width. Since the light combining means is provided, the first optical system can be significantly reduced in size to about the same as a single beam optical system,
As a result, the size of the light beam scanning device can be reduced.

[Brief description of the drawings]

FIG. 1 is a laser printer 1 according to a first embodiment of the present invention.
It is a perspective view which shows schematic structure of.

FIG. 2 is a diagram showing a first optical system 6A shown in FIG. 1 and a configuration around the first optical system 6A.

FIG. 3 is a diagram showing a polygon mirror 4 shown in FIG. 1 and a detailed configuration around the polygon mirror 4;

FIG. 4 is a diagram illustrating a first optical system 6B according to a second embodiment and a configuration around the first optical system 6B.

FIG. 5 is a diagram showing a first optical system 6C according to a third embodiment and a configuration around the first optical system 6C.

FIG. 6 is a diagram illustrating a first optical system 6D according to a fourth embodiment and a configuration around the first optical system 6D.

FIG. 7 is a perspective view showing a schematic configuration of a conventional laser printer 100.

8 is a diagram showing a first optical system 800 of FIG. 7 and a configuration around the first optical system 800. FIG.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 laser printer 3A to 3D laser beam scanning device 4 polygon mirror 5, 61 beam splitter 6A to 6D first optical system 7 second optical system 63A to 63D collimator lens 64, 73 lens 71, 72 fθ lens 74 scanning lens LD1, LD2 Laser diode LB1, LB2 Laser beam M1-M12 Deflection surface

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasushi Nagasaka 2-13-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka International Building Minolta Co., Ltd. (reference) 2C362 BA58 BA86 DA06 2H045 AA01 BA02 BA22 BA32 DA01 5C072 AA03 BA01 DA01 DA02 DA21 HA02 HA06 HA08 HA10 HA13 XA05

Claims (5)

[Claims] 1. A light beam emitted from a plurality of light sources is incident on the same deflecting surface of a rotating polygon mirror via a first optical system, and each light beam deflected by the deflecting surface is transmitted to a second optical system. A light beam scanning device that scans in the main scanning direction while irradiating the surface to be scanned on the surface to be scanned adjacently to each other at a constant interval in the sub-scanning direction, wherein the first optical system includes: Collimating means for collimating each of the emitted light beams into a light beam width wider than the deflection surface in the main scanning direction, and combining the light beams emitted from the light sources so as to travel in the same direction at a slight angle. A light combining unit, wherein the light combining unit is provided in the middle of an optical path before being collimated to the light beam width. 2. The light beam scanning device according to claim 1, wherein said collimating means comprises a single or a plurality of lenses disposed on an optical path between said light combining means and a polygon mirror. . 3. The first collimating means is disposed on an optical path between the light sources and the light combining means, and the first lens is disposed on an optical path between the light combining means and the polygon mirror. 2. The light beam scanning device according to claim 1, further comprising a second lens. 4. The optical system according to claim 1, wherein the optical axis of the first optical system and the optical axis of the second optical system are substantially included in the same plane including the rotation axis of the polygon mirror.
4. The light beam scanning device according to any one of claims 3 to 3. 5. The rotator according to claim 1, wherein the first optical system and the second optical system are configured such that a plurality of light beams synthesized by the light synthesizing unit pass through a part or all of a lens group of the second optical system, and Are arranged so as to irradiate the deflecting surface, and collimate each light beam at least in the main scanning direction via a lens that has passed at the time of incidence on the deflecting surface, so that the passing lens is 5. The light beam scanning device according to claim 4, wherein a part or all of said collimating means is replaced.