JPS60229248A - Information recording optical system - Google Patents

Abstract

PURPOSE:To execute plural optical scans having no distortion by a single optical scanner by placing a cylindrical lens in front of a recording material, when plural beams of laser light are made incident on a single optical scanner and plural records are executed by the reflected light. CONSTITUTION:A cylindrical lens 12 is placed in front of recording materials 9, 10. Laser light from laser light sources 19, 20 is brought to optical modulation by optical modulators 17, 18, made elliptical by one direction beam magnifiers 15, 16 and made incident on an optical scanner at each dirrerent angle. The reflected light is separated by mirrors 13, 14 and executes an optical scan to the recording materials 9, 10. In that case, for instance, when a screen is in an A position, unless the cylindrical lens 12 exists, the laser light is irradiated on a C position, but when the lens 12 is provided, the distortion is corrected to a D position and also, when the screen is placed at a Q position, the distortion is corrected completely. Therefore, plural optical scans having no distortion can be executed by a single optical scanner.

Description

[Detailed Description of the Invention] [Summary of the Invention] The present invention optically modulates a plurality of laser beams independently,
The present invention relates to an optical system that simultaneously performs optical recording on different positions on different recording materials.

[Background of the invention]

For example, a laser printer optical system as shown in FIG. 1 can be considered as a case where laser recording is performed independently and simultaneously on different recording materials. However, in Fig. 1, the two laser beams 1 and 2 are optically modulated independently,
A case is shown in which laser recording is performed at different positions on recording materials 9 and 10.

The rotating polygon mirrors 3 and 4 are for deflecting and scanning the laser beam, and the lenses 5 and 6 are for converting the laser beam into a minute spot to be scanned on the recording material 9.about.10. The recording materials 9 and 10 advance in the direction of the arrow, and laser recording can be performed on the entire surface of the recording materials. Note that 7 and 8 are reflecting mirrors.

However, in the laser printer shown in FIG. 1, the number of rotating polygon mirrors required for recording independently is required, which has the disadvantage that the apparatus becomes large, complex, and expensive.

[Purpose of the invention]

An object of the present invention is to eliminate the drawbacks of the prior art described above and to realize an inexpensive, small, and simple optical system for recording information.

[Summary of the invention]

In order to achieve the above object, the optical system of the present invention uses a single optical scanner to optically scan a plurality of laser beams to positions on a recording material, and uses a single optical scanner to optically scan a plurality of laser beams to positions on a recording material. It is characterized in that a cylindrical lens is placed in front of the recording material for all or all but one of the laser beams.

[Embodiments of the invention]

The present invention will be explained below with reference to the drawings. However, in order to guide a plurality of laser beams scanned by a single optical scanner to different recording material positions, it is necessary to spatially separate the plurality of laser beams.

Therefore, a plurality of laser beams are made to enter a single optical scanner at different angles.

FIG. 2 shows a case where a galvanometer mirror is used as the eight-beam scanner 11, which shows the case of laser recording using two laser beams. In order to optically scan different positions on the recording material (or screen) 9, the optical scanner is set at different angles ψ.
Inject two laser beams. Each of the two laser beams is a solid line.

Indicated by a chain line.

Assume that the deflection angle of the optical scanner is p. However, when p=Q, it is assumed that the laser beam irradiates the center of the optical scanning line formed on the screen 9. Further, if the angle between the laser beam emitted from the optical scanner and the laser beam incident on the optical scanner when p=Q is 90', the position y5 on the screen 9 is expressed by the following equation.

2(1-cos2F(1cos(2p))) However, 2
indicates the distance between the optical scanner and the screen.

According to the above calculation results, in the case of the laser beam shown by the solid line, -ψ = 0, and yS/Q shown in equation (1) becomes zero regardless of P, and a straight line scan as shown in Figure 2 is realized. can.

However, in the case of the dashed line, ψ±0 results in a curved scanning line as shown by δ in FIG.

In order to correct this distorted scanning line, a cylindrical lens is placed in front of the screen 9 in the present invention.

The correction principle for correcting distorted scanning lines will be explained with reference to FIG. FIG. 3(a) is a view of the cylindrical lens viewed from the direction of incidence of laser light, and a distorted scanning line g is incident on the cylindrical lens. FIG. 3(b) is a side view of the cylindrical lens. Assume that a distorted scanning line is incident as shown in the figure. The screen is at position A, that is, the distance between the cylindrical lens and the screen is the cylindrical lens focal length f. If they are separated, the laser beam will irradiate the position C when there is no cylindrical lens, but when the cylindrical lens is present, the laser beam will irradiate the same position, and as a result, the distorted scanning line will be corrected. The magnitude of distortion is the amount f shown in equation (1)
c/0 times relaxed.

It is clear from the figure that the distortion of the scanning line can be corrected even better if the screen position is shifted by an amount Δ from A to B.

When the screen position is set to Q, the distortion is completely corrected and a straight scan line can be achieved.

FIG. 4 is a diagram when the optical system according to the present invention is applied to a laser printer. However, as multiple laser beams, 2
This shows the case of a book. 19°20 is a laser light source, 17
, 18 are optical modulators that optically modulate each laser beam independently. 15° and 16 are one-sided beam expanders, consisting of a combination of cylindrical lenses. At the location where the laser beam exits the one-way beam expander and enters the imaging lens 5, the cross-sectional shape of the laser beam is elliptical as shown in FIG.

The two laser beams enter the optical scanner so that the optical scanning planes formed by the two laser beams have different angles, and after exiting the optical scanner, the mirror 13.
14 to enable spatial separation.

12 is a cylindrical lens that makes it possible to form a scanning line without distortion on the recording materials 9, 10;
10 is moved in the direction of the arrow so that it can be recorded on the entire surface.

The reason why the laser beam is formed into an elliptical shape as shown in FIG. 5 when it enters the rotating polygon mirror will be described below. That is, a wide 18g
Regarding the direction, since the cylindrical lens 12 has no curvature, it does not have a narrowing function. Therefore, the wide width d2 is narrowed down to the recording material minutely using only the imaging lens. Due to diffraction, the narrow width d1 cannot be narrowed down onto the recording material by the imaging lens alone, but is narrowed down by the cylindrical lens 12.

Therefore, as a result, it becomes possible to narrow down the light spot to a minute spot on the recording material in both the wide width direction and the narrow width direction.

FIG. 6 shows another application example of the optical system according to the present invention, in which it is applied to a laser printer for multicolor printing. However, the case where two laser beams are used as the plurality of laser beams is shown. The two laser beams are attached to a recording material 27 called a photosensitive drum.
Scan different positions on the top. The information optically recorded on the photosensitive drum is transferred to plain paper 2 using a well-known electrophotographic process.
4 is printed on. That is, if 21 is a charger, 22 is a developer using, for example, red toner, and 23 is a developer using, for example, black toner, printing in two colors will be recorded on the plain paper 24.

In addition, in FIG. 6, 25 is a transfer device, 26 is a cleaning device,
28 indicates the fixing amount.

In the above description, the case where a gas laser is used as the laser light source is shown, but it is also possible to replace it with a semiconductor laser. In particular, the use of a semiconductor laser array having a plurality of laser light output sections arranged in the negative dimension has the advantage of simplifying the optical system. FIG. 7 shows three laser beam output sections 31(a).

31(b) and 31(c). Laser light output from a semiconductor laser array generally has an elliptical laser light radiation distribution as shown at 30.

FIG. 8 shows a case where a semiconductor laser array having two laser light output sections is introduced into the optical system in the apparatus of FIG. 4. A coupling lens 32 is used to efficiently convert laser light emitted from a semiconductor laser into parallel light.

5 indicates an imaging lens.

Each of the two laser beams incident on the imaging lens 5 in FIG. 8 has an elliptical cross-sectional intensity distribution as shown in FIG. This is because, as explained using FIG. 7, the laser beam radiation distribution from the semiconductor laser is elliptical. It has already been explained that the laser beam having such an elliptical cross-sectional intensity distribution is focused by the imaging lens 5 and the cylindrical lens 12 into a minute circular spot on the recording material.

In the explanation so far, the case where the imaging lens is placed on the laser light source side of the optical scanner is shown, but it may be placed on the recording material side of the optical scanner. In this case, a known lens called an Fθ lens can be used as the imaging lens. 9th
The figure shows the case where the Ffl lens 34 is introduced into the optical system of FIG. 8.

The lens system 33 is for converting the beam width of the incident parallel beams 1 and 2 and emitting them as parallel beams again. F
The laser beam after exiting from the θ lens is divided by mirrors 13 and 14.
Recording materials 9 and 10 located at different locations are optically scanned. In front of the recording material, a cylindrical lens 12 is arranged for the purpose already mentioned above.

In the above description, the case of two laser beams has been described, but the present invention is of course applicable not only to two laser beams but also to a plurality of laser beams.

〔Effect of the invention〕

As described above, according to the present invention, a plurality of laser beams are incident on the scanning surface of an optical scanner at different angles, and the plurality of laser beams are optically scanned on a recording medium by a single optical scanner without distortion of the scanning line. can do.

[Brief explanation of drawings]

Figure 1 is a diagram for explaining the conventional optical system, Figure 2 is a diagram for explaining the drawbacks of the conventional optical system, and Figures 3 (a) and 3 (b) are details of the present invention. FIG. 4 is a diagram for explaining one embodiment of the optical system of the present invention.
FIG. 5 is a diagram for explaining the distribution of laser light to explain the present invention, FIG. 6 is a diagram for explaining the present invention in detail, FIG. 7 is a diagram showing a semiconductor laser array, and FIG. The figure shows an optical system of the present invention when a semiconductor laser array is used, and FIG. 9 is a diagram showing an optical system of the invention when a semiconductor laser array and an Fθ lens are used. Atsushi 1 Figure 2 Figure ') l' 53 Figure (a) Figure 3 (b) 8 δ 'VJ41!1 (6th VJ7 mouth δ Figure continued from page 1 0 Inventor Hashimoto Chapter Higashi, Kokubunji City Inventor Kimio Tateno Kunichi □Careo Research Institute ν1-28 @ Hitachi, Ltd. Naka Y1-chome Akeji Hitachi, Ltd. Naka

Claims (1)

[Claims] 1. A single optical scanner that scans a plurality of laser beams, a single or plural imaging lens that focuses the plurality of laser beams onto a recording material, and the optical scanner. an optical means that separates the plurality of scanned laser beams after emission and guides them to different locations on the recording material; and for all or only a predetermined number of the plurality of laser beams scanning the recording material; An information recording optical system comprising cylindrical lenses placed in front of the recording material. 2. As a laser light source that emits the plurality of laser beams,
2. An information recording optical system according to claim 1, characterized in that a semiconductor laser array 1 having a plurality of laser light output sections arranged in -dimensional form is used.