JPH0743627A - Optical scanning device - Google Patents

Abstract

PURPOSE:To prevent the generation of the irregularity of a pitch and a bow with a simple constitution and to miniaturize the device in the sub-scanning direction with an inexpensive constitution by providing a lens provided for every light source and having the power in the sub-scanning direction and a lens provided in common with the light source and having the power only in the main scanning direction. CONSTITUTION:In the optical path of a first light beam Ba, a collimator lens 10a is provided for making a radial light beam transmitted from a first laser diode LDa nearly a parallel light beam. A first cylindrical lens 11a having a positive power in the sub-scanning direction for linearly converging the light beam made to be nearly parallel by means of the lens 10a in the vicinity of the polarization plane of a polygon mirror 2. The polygon mirror 2 for deflecting/scanning the first light beam Ba and a second light beam Bb in the same way and a first lens 12 and a second lens 13 having the power only in the direction of main scanning common in both the first and the second light beams Ba, Bb are provided. The light beams Ba, Bb reach a photoreceptor 1 through these common lenses.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning optical device, and more particularly to a scanning optical device provided in a laser beam printer, a digital copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, as a scanning optical device, as shown in FIG. 8, a laser beam from a plurality of laser light sources is deflected and scanned by one deflection mirror to irradiate a photoconductor as a recording medium, and the photoconductor is irradiated with the laser beam. Those that form a latent image have been proposed. In this scanning optical device, a plurality of laser lights are incident on a polygon mirror as a deflection mirror perpendicularly to the sub-scanning direction, a lens is provided for each optical path of the plurality of laser lights, and the plurality of lenses are arranged in the sub-scanning direction. They are arranged in layers. Further, each laser beam is configured to be able to pass through the generatrix of the lens having power in the sub-scanning direction. With such an arrangement, the unevenness of the pitch due to the deviation of the scanning line on the photoconductor due to the tilting of the deflecting surface of the polygon mirror and the entering and leaving of the surface is prevented. Also, the occurrence of bow due to lens aberration and the like is prevented.

[0003]

However, the scanning optical device having the above-mentioned structure has a problem that the number of parts of the lens is large and the cost is high because the lens is arranged for each of the plurality of laser light sources. Further, since the lenses are arranged so as to correspond to the plurality of laser light sources, the polygon mirror becomes large in the sub-scanning direction. Therefore, in order to improve the deflection scanning of the polygon mirror, it is necessary to improve the processing accuracy of the polygon mirror. On the other hand, in order to reduce the size of the polygon mirror in the sub-scanning direction, it is necessary to thin the condenser lens in the vertical direction, and it is necessary to improve the processing accuracy of the lens. Increasing the processing accuracy of the polygon mirror and the lens has a problem of further increasing the manufacturing cost.

[0004]

[Purpose] The present invention has a simple structure and has a uniform pitch.
An object of the present invention is to provide a scanning optical device capable of preventing the occurrence of bow. Another object of the present invention is to provide a scanning optical device which is inexpensive and can be downsized in the sub-scanning direction.

[0005]

In order to solve the above-mentioned problems, the invention according to claim 1 is provided in common to a light source and a first lens provided for each light source and having a power in the sub-scanning direction. And a second lens having a power only in the main scanning direction, and a scanning optical device.

According to a second aspect of the present invention, there is provided a synthesizing unit for synthesizing the laser beams from the plurality of light sources, and a separating unit for separating the plurality of laser beams synthesized by the synthesizing unit. The first lens is provided between the synthesizing unit and the separating unit, and the second lens is provided between the separating unit and the recording medium. It is a scanning optical device.

[0007]

According to the scanning optical device of the first aspect, the laser light is condensed in the sub-scanning direction by the first lens, while being condensed in the main scanning direction by the second lens. The first lens is provided for each light source, and is provided so that its generatrix coincides with the scanning plane of the laser light from the light source. Further, the second lens is provided commonly to all the light sources.

According to the scanning optical device of the second aspect,
The laser light is combined by the combining means, and then passes through the first lens provided commonly to the plurality of light sources. or,
The laser light passes through the second lens after being separated by the separating means.

[0009]

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

FIG. 1 is a perspective view showing the overall construction of an optical system of a laser beam printer which is an embodiment of the scanning optical apparatus according to the present invention, and FIG. 2 is a side view of the overall construction.

The scanning optical device 100 includes an optical path of a first light beam Ba oscillated by a first laser diode LDa and a second optical path of a first light beam Ba.
Second light flux Bb oscillated by laser diode LDb
And the optical path of.

In the optical path of the first light flux Ba, a collimator lens 10a for converting the radial light flux emitted from the first laser diode LDa into substantially parallel light, and the light flux converted into substantially parallel light by the collimator lens 10a. The first cylindrical lens 11a having a positive power in the sub-scanning direction for linearly condensing the polygon mirror-2 in the vicinity of the deflection surface, the first light beam Ba and the second light beam Bb are deflected and scanned on the same deflection surface. Polygon mirror-2 common to the first and second light fluxes Ba and Bb, first lens 12 and second lens 1 having power only in the main scanning direction common to the first and second light fluxes Ba and Bb
3, a separation mirror 20a for separating the first light flux Ba from the second light flux Bb, a first folding mirror 22a for deflecting the first light flux Ba onto the photoconductor 1, and a first folding mirror 22a.
A third lens 14a for converging the first light beam Ba deflected on the photoconductor 1 by the point lens on the photoconductor 1 is provided, and the first light beam Ba on the photoconductor 1 is passed through these third lenses 14a. To reach.

Further, in the optical path of the second light beam Bb, a collimator lens 10b for converting the light beam emitted from the second laser diode LDb into substantially parallel light, and this collimator lens 1
The polygon mirror-2
Of the first cylindrical lens 11b having a positive power in the sub-scanning direction for linearly condensing in the vicinity of the deflecting surface of the second mirror, a synthetic mirror -21b for matching the second light flux Bb with the first light flux Ba in the horizontal plane, The first and second light beams Ba and B for deflecting and scanning the first light beam Ba and the second light beam Bb on the same deflection surface.
b common polygon mirror-2, first and second luminous fluxes Ba, B
b First lens 1 having power only in the common main scanning direction
2 and the second lens 13, and the second light flux between the first folding mirror 22b and the second folding mirror 23b that deflect the second light flux Bb onto the photoconductor 1 and between the first folding mirror 22b and the second folding mirror 23b. A third lens 14b for condensing Bb in a dot shape on the photoconductor 1 is provided, and the second light flux Bb reaches the photoconductor 1 via these.

Here, both light fluxes Ba and Bb are incident perpendicularly to the rotation axis of the polygon mirror-2. Therefore, the deviation of the scanning position on the photoconductor 1 due to the entry and exit of the deflecting surface of the polygon mirror-2 is prevented.

FIG. 3 shows a scanning optical device 1 in which the mirror group is omitted.
00, FIG. 3A shows the power of each lens in the sub-scanning direction, and FIG. 3B shows the power of each lens in the main-scanning direction. As is apparent from FIGS. 3A and 3B, the first lens 12 and the second lens 13, which are lenses common to the first and second light beams Ba and Bb, have no power in the sub-scanning direction. . On the other hand, the lenses 10a, 10b, 11a, 11b, 14a, 14b having power in the sub-scanning direction.
Is provided for each of the light fluxes Ba, Bb, and each of the light fluxes Ba, B
lens 10a, 10b, 11a, 1 corresponding to b
It can be passed through the bus lines of 1b, 14a, 14b. Therefore, the linearity of the scanning line is secured on the photoconductor 1 and the occurrence of bow can be prevented. Further, as is apparent from FIG. 3A, the lenses 11a to 14a and 11b to 14b have a conjugate relationship between the deflecting surface of the polygon mirror 2 and the photosensitive member 1, so that the deflecting surface of the polygon mirror is The deviation of the scanning position on the photoconductor 1 due to the surface tilt can be corrected.

The specifications of the lens used in this embodiment are shown below.

F = 272 mm, F = 50, wavelength used λ = 780 nm r1 = 2405.956 ∞, d1 = 8.00, n1 = 1.5168 r2 = 285.994 ∞, d2 = 50.00, n2 = 1 .0000 r3 = 2121.315 ∞, d3 = 13.58, n3 = 1.5168 r4 = −111.628 ∞, d4 = 150.00, n4 = 1.0000 r5 = ∞ *, d5 = 5.00, n5 = 1.4916 r6 = ∞ ∞ * The sectional shape is a part of a circle, and when the distance in the sub-scanning direction is a, r at that time is r = 43.500 + 3.2829 × 10 −3 × a + 3. 0
36 * 10-4 * a2 + 1.4895 * 10-6 * a3.

By using the above-mentioned lens and having the above-mentioned structure, the field curvature in the main scanning direction is ± 0.4 mm, and the field curvature in the sub-scanning direction is ± 0.8 mm, and good scanning can be performed.

FIG. 4 is a perspective view showing the configuration of another embodiment of the scanning optical device of the present invention. In this embodiment, the laser diode LDa and the collimator lens 10a are unitized to form a laser unit LUa, and the laser unit LUa and the first cylindrical lens 11a are arranged in the V block 30a. Different from
The V block 30a is configured to be adjustable in the sub scanning direction. The other structure is the same as that of the first embodiment, and the description thereof is omitted here.

FIG. 5 is a diagram showing the movement of the optical path of the light flux when the V block 30a is moved in the sub-scanning direction.
The broken line in this figure is the optical path of the light beam before adjustment, and the solid line is the optical path of the light beam after adjustment. By adjusting the optical system for each V block 30a, the optical path can be adjusted so as to pass through the generatrix of the lens 14a having power in the sub-scanning direction.

FIG. 6 is a perspective view showing a method of adjusting the V block 30a in the sub-scanning direction. In this embodiment, V
A member for disposing the block 30a and the optical member (hereinafter, referred to as PH
Is written. The height of the adjusting screw 31a between 40) is adjusted to adjust the V block 30a in the sub-scanning direction.

FIG. 7 is a perspective view showing another method of adjusting the V block 30a in the sub-scanning direction. By inserting a spacer 32a between the V block 30a and the PH 40, V is blocked.
The block 30a is adjusted in the sub-scanning direction.

As described above, in the above two embodiments, the first, second and third lenses 1 provided for each of the light fluxes Ba and Bb.
Power in the main scanning direction may be distributed to 2, 13, 14a, and 14b.

[0024]

As is apparent from the above description, claim 1
According to the scanning optical device described in (1), the laser light is condensed in the sub-scanning direction by the first lens, and is condensed in the main scanning direction by the second lens. The first lens is provided for each light source, and is provided so that its generatrix coincides with the scanning plane of the laser light from the light source. Also, the second
The lens is provided for all light sources. Therefore,
Since each laser beam can pass through the generatrix of the first lens, it is possible to prevent pitch unevenness and bow from occurring. Further, since the second lens is provided in common for each light source, the number of parts can be reduced. Therefore, the present invention can provide a scanning optical device having a simple structure and capable of preventing pitch unevenness and bow from occurring.

According to the scanning optical device of the second aspect,
The laser light is combined by the combining means and then passes through the first lens. Further, the laser light passes through the second lens after being separated by the separating means. Therefore, the arrangement of the second lens is free, and the dimensions of the first lens and the deflection mirror in the sub-scanning direction can be reduced without making the second lens thin.

[Brief description of drawings]

FIG. 1 is a perspective view showing an optical system of a laser beam printer which is an embodiment of a multi-beam scanning optical system according to the present invention.

FIG. 2 is a side view showing an optical system of a laser beam printer which is an example of a multi-beam scanning optical system according to the present invention.

FIG. 3 is an optical system in which a mirror group is omitted, (a) is a diagram showing a power of each lens in a sub-scanning direction, and (b) is a diagram showing a power of each lens in a main-scanning direction.

FIG. 4 is a diagram showing an overall configuration of an optical system of Example 2.

FIG. 5 is a diagram showing movement of an optical path of a light beam when a V block is moved in a sub scanning direction.

FIG. 6 is a perspective view showing an embodiment of a method for adjusting the V block in the sub-scanning direction.

FIG. 7 is a perspective view showing another embodiment of the method of adjusting the V block in the sub-scanning direction.

FIG. 8 is a diagram showing a configuration of a conventional scanning optical device.

[Explanation of symbols]

 1: Photoconductor 2: Polygon mirror 10a, 10b: Collimator lens 12: First lens 13: Second lens 14a, 14b: Third lens 20a: Separation mirror 21b: Synthetic mirror 22a, 22b: First folding mirror 23b : Second folding mirror LDa: First laser diode LDb: Second laser diode Ba: First light flux Bb: Second light flux 30a: V block 31a: Adjustment screw 32a: Spacer LUa: Laser unit

Claims (2)

[Claims] 1. A plurality of light sources for emitting laser light, a single deflection mirror for deflecting the laser light from the plurality of light sources, and a lens for forming an image of the plurality of laser lights on a recording medium. In the scanning optical device in which the laser light is incident on the deflection mirror at different positions in the sub-scanning direction, a first lens that is provided in common to the light sources and that has power only in the main scanning direction; A scanning optical device comprising: a second lens provided for each of the second lenses and having a power in the sub-scanning direction. 2. A synthesizing means for synthesizing laser light from the plurality of light sources, and a separating means for separating the plurality of laser light synthesized by the synthesizing means, wherein the first lens is the synthesizing means. 2. The scanning optical apparatus according to claim 1, wherein the second lens is provided between the separating means and the recording medium, and the second lens is provided between the separating means and the recording medium.