JPS61184515A - Laser scanning device - Google Patents

Abstract

PURPOSE:To the titled device by forming an image by a cylindrical lens having f.theta image forming capacity for the direction of main scanning and forming the image in the direction of sub-scanning by another cylindrical lens. CONSTITUTION:Laser light of a semiconductor laser 11a is made to parallel light by a collimator lens 12a. The first cylindrical lens 13a is made to a convex lens in the direction of sub-scanning, and has focal length to form an image on a photosensitive body 16, and the diameter d of a laser spot is determined by the lens 13a. Laser light of a laser 11b is made to parallel light by a collima tor lens 12b and deflected by a polygon polarizer 14b in the direction of main scanning. The laser beam forms an image on the photosensitive body 16b by the second cylindrical lens 15b having f.theta image forming capacity in the direc tion of main scanning. The diameter d2 of laser spot of the photosensitive body 16b is determined by the image forming capacity of the lens 15b. Thus, focusing can be made simply.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laser scanning device that records an image by deflecting and scanning a laser beam of a semiconductor laser onto a photoreceptor.

2. Description of the Related Art In recent years, laser scanning devices that record images using semiconductor lasers have been widely used in lasers, printers, and the like.

Hereinafter, an example of the conventional laser scanning device mentioned above will be explained with reference to the drawings. FIG. 6 shows a schematic configuration diagram of a conventional laser scanning device.
1 is a semiconductor laser, 52 is a collimator lens, 54 is a polygon deflector, 55 is a condensing lens, and 66 is a photoreceptor. The operation of the conventional laser scanning device configured as described above will be explained below.

First, a semiconductor laser 5 whose optical intensity is modulated by an image signal
After the laser beam No. 1 is made into parallel light by the collimator lens 62, it is deflected by the polygon deflector 54, and then
An image is formed on the photoreceptor 56 by the imaging lens 56 and scanned.By scanning the laser beam whose light intensity is modulated in accordance with the image signal on the photoreceptor 56, it is possible to record the entire image. can. Here, the imaging lens 56 forms an image of the laser beam on the photoreceptor 56, and at the same time, the image height f·θ (f is the focal length of the lens 56) is proportional to the incident angle θ of the laser beam. It has a correction effect of scanning on 66.

Problems to be Solved by the Invention However, in the above configuration, the imaging lens has a large diameter, and the entire laser scanning device becomes large. In particular, the imaging lens 55 uses only the central laser scanning portion. In addition, in order to use the one-quadrant lens 56 by cutting it into only the portion necessary for the central scanning section,
This has the problem of high costs for determining cutting.

In view of the above-mentioned problems, the present invention provides a flat and compact laser scanning device that is constructed with an optical system that is effective only for the scanning portion of the laser beam.

Means for Solving the Problems In order to solve the above problems, the laser scanning device of the present invention replaces the conventional imaging lens with a cylindrical lens having f/θ imaging performance in the scanning direction. and is configured so that imaging in a direction perpendicular to the scanning direction is performed by another cylindrical lens (first cylindrical lens) provided between the semiconductor laser and the polarizer and movable in the laser optical path. This makes it a good companion for thin scanning devices.

Effect Ω With the above configuration, the present invention has imaging performance in the direction perpendicular to the scanning direction with the first cylindrical lens, and imaging performance in the scanning direction with the polygon deflector and the second cylindrical lens provided later. By having the performance of f/θ scanning correction in the scanning direction, this is a thin laser scanning device that has the same performance as a conventional f/θ imaging lens.

Furthermore, by adjusting the first cylindrical lens back and forth along the optical path of the entire laser beam, the spot diameter of the laser beam on the photoreceptor can be changed and the focus can be easily adjusted.

EXAMPLES Below, a laser scanning device of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a laser scanning device according to a first embodiment of the present invention. In Fig. 1, 1 is a semiconductor laser, 2 is a collimator lens,
3 is a first cylindrical lens, 4 is a polygon deflector, 6 is a second cylindrical lens, and 6 is a photoreceptor.

The entire operation of the laser scanning device constructed as described above will be explained below with reference to FIGS. 1 and 2 (lL) and (b).

FIG. 2 (2L) shows the laser scanning device of the present invention in FIG. 1 in a direction perpendicular to the scanning direction (hereinafter referred to as the sub-scanning direction).
This is the view from. In FIG. 2 (2L), the laser light from the semiconductor laser 11& is made into parallel light by a collimator lens 122L. First cylindrical lens 13
& is a convex lens in the sub-scanning direction, and has a focal length for forming an image on the photoreceptor 16&.
Since the cylindrical lens 15& has no imaging performance in the sub-scanning direction, the laser spot diameter d1 on the photoreceptor 162L is the same as that of the first cylindrical lens 13&.
Determined by

FIG. 2(b) shows the laser scanning device in FIG. 1 viewed from above in a direction parallel to the scanning direction (hereinafter referred to as the main scanning direction). In FIG. 2(b), the semiconductor laser 11
The laser beam b is collimated by a collimator lens 12b and deflected in the main scanning direction by a polygon polarizer 14b. Here, the first cylindrical lens 13b does not have imaging performance in the main scanning direction. The deflected laser beam is imaged onto the photoreceptor 16b by the second cylindrical lens 15b with single-image focusing performance in the main scanning direction. The laser spot diameter d2 on the photoreceptor 16b in the main scanning direction is determined by the imaging performance of the second cylindrical lens 15b. Here, the second cylindrical lens has f/θ scanning correction characteristics. Therefore, it is often composed of multiple cylindrical lens groups.

In FIG. 1, the laser spot diameter d2 on the photoreceptor 6 in the main scanning direction, the laser spot diameter d2 in the sub-scanning direction,
Since it is designed to be very small, the focus on the photoreceptor 6 can be easily adjusted by simply adjusting the first cylindrical lens 3 back and forth on the laser optical path.

As described above, according to this embodiment, by providing the first cylindrical lens and the second cylindrical lens before and after the deflector, it has the same characteristics as the conventional f/θ one-quadrant lens. , it is possible to realize a thin laser scanning device that allows easy focus adjustment. In addition, to create the collimator lens, after creating a long cylindrical lens,
By cutting into multiple pieces, it is possible to create a large number of cylindrical lenses at once, and the cost can also be reduced.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a schematic configuration diagram of a laser scanning device showing a second embodiment of the present invention. In the figure, 21 is a semiconductor laser, 22 is a collimator lens, 23 is a first cylindrical lens, 24 is a polygon deflector, 25 is a second cylindrical lens, and 26 is a photoreceptor. The above configuration is similar to the configuration shown in FIG. The difference from the configuration shown in FIG. 1 is that a third convex cylindrical lens 27 is provided between the photoreceptor 26 and the second cylindrical lens 25. The operation of the laser scanning device configured as described above will be explained below. Even if there is an error in the angle of inclination of each reflecting surface of the polygon deflector 24, it is corrected by the third convex cylindrical lens 27. .

FIG. 4 shows the state of correction when there is an error in the angle of inclination of the reflective surface of the polygon deflector 24&. In FIG. 4, when the angle of the reflective surface of the polygon deflector 24b is different, the laser beam
Although the beam 28 deviates from its normal position, it is corrected to the normal scanning position on the photoreceptor 26a by the third convex cylindrical lens 27B. Here, the first cylindrical lens 231L and the third convex cylindrical lens 2a The focal lengths of the first cylindrical lens 232Lt and the laser beam are adjusted so as to form an image on the photoreceptor 26a.

In the embodiment shown in FIG. 3, a convex cylindrical lens is used to correct the inclination angle of the polygon deflector, but the same effect can be obtained by using a concave mirror 37 in the configuration shown in FIG. 4 as shown in FIG. .

Effects of the Invention As described above, the present invention includes a first cylindrical lens and a second cylindrical lens before and after the deflector, and a mechanism that allows the first cylindrical lens to move back and forth along the laser optical path. , it is possible to provide a thin laser scanning device with easy focus adjustment.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a laser scanning device according to a first embodiment of the present invention, FIGS. 2a and b are explanatory diagrams of the operation of the laser scanning device of FIG. 1, and FIGS. 5 is a schematic configuration diagram showing another embodiment of the present invention, and FIG. 6 is a schematic configuration diagram showing a conventional laser scanning device. It is. 1+ 11a, 11b+ 21, 21 a, 3
1-knee...semiconductor laser, 2. 12J 12b,
22. 22a+32...Collimator lens, 3.13&, 1:123.231L, 33...
...first cylindrical lens, 4.14 &, 14
b, 24.24&, 24b. 34... Polygon deflector, 5.15a, 16b
. 25.251.35...Second cylindrical
Lens, 6, 16a, 16b, 26, 26a, 36...
...Photoreceptor, 27 T 27 +L...
Third convex cylindrical lens, 37... Concave mirror. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
1 Semiconductor wood plate - 5 - 2nd gildrical lenses 6 - Photoconductor/2 2 - Collimator Lens tS - 2nd cylinder 16 -
Photoreceptor 21-11 semiconductor router. 22-m-co 11 meters Figure 3 23
- 1st cylindrical lens) SW27--1 year old 3 cylindrical lens! Figure 4

Claims (3)

[Claims] (1) a deflector that deflects and scans a laser beam of a semiconductor laser on a photoreceptor; a first cylindrical lens disposed between the deflector and the semiconductor laser; a second cylindrical lens section disposed between the first and second cylindrical lenses and having imaging performance in the scanning direction of the laser beam; and means for movable the first cylindrical lens along the optical path of the laser beam. A laser scanning device characterized by comprising: (2) The laser scanning device according to claim 1, wherein the second cylindrical lens portion is composed of a cylindrical lens having an imaging characteristic of f and θ in the scanning direction. (3) A patent claim characterized in that the second cylindrical lens section is provided with a third convex cylindrical lens or a concave mirror having imaging performance in a direction perpendicular to the scanning direction between the second cylindrical lens section and the photoreceptor. The laser scanning device according to item 1.