JPS6026313A - Photoscanner - Google Patents

Abstract

PURPOSE:To correct a shift in the convergence position of diffracted light due to the expansion of a hologram disk by providing a means which detects the convergence position of the diffracted light from a hologram which rotates continuously, and varies a photoscanning position and an angle. CONSTITUTION:The hologram disk 3 expands in high-speed rotation up to a state shown by a broken line 3a. Laser light 6 emitted by a laser device 1 is reflected by a mirror 2 to illuminate the disk 3, and its diffracted light 7 is converged to a position 8, but diffracted light 7a is converged to a position 8a on the expanded disk 3a. A position detector 4 detecting the difference between the positions 8 and 8a outputs a signal to rotate the mirror 2, thereby correcting the shift 8a in the convergence position 8a of the diffracted light.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an optical scanning device for a hologram disk, and particularly to a position for irradiating light onto a hologram disk.

This invention relates to an optical scanning device whose angle can be automatically changed.

(2) Background of the technology In recent years, various laser devices have been developed and manufactured, and are particularly stable at high output and are used in various fields. On the other hand, Gabor's holography technology had been established before the development of laser equipment. This holography records the diffraction pattern on each plane of waves transmitted or reflected by an object, and then performs diffraction inversion processing to reproduce the shape, structure, etc. of the object contained in the diffraction pattern. It is. This recorded hologram is created by irradiating, for example, an object with coherent light and photographing it on a photosensitive material using the light reflected by the object and the light irradiated onto the object as reference light. This holography technology has been developed in conjunction with laser devices that output coherent light, and has led to research and development of laser holography. On the other hand, in laser printers etc. that use laser light, polygon mirrors,
Research and development are being conducted on techniques that utilize holograms instead of optical scanning using lens systems and the like. This hologram is used for various recording purposes because it does not affect the reproducibility of laser beams even if it is dusty or damaged to some extent. Since this hologram disk has a hologram recorded on a glass plate, there is a demand for a reduction in weight and cost.

(3) Conventional technology and problems Conventionally, hologram disks have used glass plates, so there has been a natural limit to their ability to reduce weight and cost. For this reason, hologram disks made of film have been researched and developed in place of the glass.

However, the hologram or disk of the film works well when rotated at low speed, but when rotated at high speed, it has the problem of stretching in the outer circumferential direction. That is, this hologram disk has a drawback that the pitch of the interference fringes of the hologram recorded on the disk changes. Then, the light of wavelength λ that is irradiated onto this hologram disk at an incident angle θi has a pitch d of interference fringes, a diffraction angle θ0, and a sin θ〇−
Since it is diffracted by 5inθi=n·λ/8, the diffraction angle θ0 changes with a change in the pitch d of the interference fringes.

This results in a shift in the convergence position of the light. Therefore, when applied to a laser printer or the like, there is a problem in that the dots are misaligned.

(4) Purpose of the Invention In view of the above-mentioned conventional drawbacks, the present invention detects in advance the convergence position of the diffracted light when the hologram disk of the film is not stretched, and eliminates the shift in the convergence position of the diffracted light due to the stretch of the hologram disk. It is an object of the present invention to provide an optical scanning method that corrects this by changing the position and angle at which light is irradiated onto the hologram disk.

(5) Structure and object of the invention According to the present invention, in an optical scanning device using a hologram disk, an optical scanning line is formed in a direction perpendicular to the scanning direction by diffracted light from the continuously rotating hologram. This is achieved by providing an optical scanning device characterized by providing a means for changing the position and angle at which light is irradiated onto the hologram so that the hologram is detected at a position and scanned to a predetermined position based on the detection.

(6) Examples of the invention An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram for explaining an optical scanning device according to the present invention.

In FIG. 1, a laser beam 6 output from a laser device 1 is reflected by a mirror 2 and is reflected by a hologram disk 3 of a film.
The surface is illuminated. The irradiated light is diffracted by the interference of the hologram disk 3 of the film and becomes a single diffracted light 7 which is converged at a convergence position 8.

Further, if the state in which the hologram disk 3 of the film is extended by rotating at high speed is assumed to be 33, then the first diffracted light is converged at 8a. Hologram disk 3.3a of said film
The position detector 4 detects the deviation of the convergence positions 8, 8a of the diffracted lights 7, 7a, and outputs a signal to the drive control unit 5 for driving the mirror 2. The drive control unit 5, which receives the signal, is configured to move and drive the mirror 2 three rotations.

In FIG. 1, the film hologram disk 3 is rotated at high speed and is stretched into the state shown by the broken line 3a.

At this time, if the pinch of the hologram interference fringes recorded on the hologram disk 3 is d, and the pitch of the hologram interference fringes when the hologram disk 3 is extended to become 3a is d+Δd, then sin θ=n −λ/d,s
The diffraction angles θ and θ' by the respective hologram disks are different from the two equations inθ#=n·λ/(d+Δd). Note that the light irradiated onto each hologram disk is, for example, a laser beam that is perpendicular and has a constant wavelength λ. Therefore, the diffracted lights 7, 7a by the respective hologram disks 3, 3a are 8.8a
converges at the position. Diffracted light 71 by the hologram disk 3. The position detector 4 detects in advance the convergence position 8 and the convergence position 8a caused by the diffracted light 7a by the hologram disk 3a, and outputs a signal indicating the positional deviation of the convergence positions 8, 8a to the mirror drive control section 5. The mirror drive control unit 5 inputting the signal drives the mirror 2 in order to change the position and angle at which light is irradiated onto the hologram disk 3a according to the positional deviation of the convergence positions 8 and 8a. The drive to change the position moves the mirror 2 parallel to the surface of the hologram disk 3a, and the drive to change the angle rotates the mirror 2. As mentioned above, hologram disk 3
Even if it is in the extended state 3a due to high speed rotation, the convergence position of the diffracted light can be corrected by moving and rotating the mirror 2.

Next, correction of the convergence position by one rotation of the mirror 2 will be explained based on an enlarged view of the main part.

FIG. 2 is an enlarged view of essential parts of an embodiment of the present invention.

In the figure, the film hologram disk 3 indicated by the solid line is rotating at a low speed, for example, and is in a state of no elongation. At this time, a coherent light, for example a laser beam 6 having a wavelength λ, is reflected by the mirror 2.

The three surfaces of the hologram disk are irradiated perpendicularly. This irradiation light converges as a diffracted light 7 having a diffraction angle θ according to the relational expression sin θ=n·λ/8 due to the pitch d of the interference fringes of the hologram disk 3. However, the hologram disk 3
rotated at high speed and elongated. In other words, the hologram disk 3a changes, and the pitch of the interference fringes recorded on the hologram disk 3 changes. If the amount of change in pitch is △d, then from the previous equation, sinθ'aI-n・
λ/(d+Δd) holds, and unlike the diffracted light 7, a diffracted light 7a shown by a broken line is obtained at a diffraction angle θ'al. As a result, the convergence positions of the laser beams of the hologram disk 3 and the hologram disk 3a are different. Therefore, the mirror 2 is rotated in accordance with the positional deviation as described in FIG. 1, and is brought into a state 2a shown by a broken line. By doing so, it is possible to obtain the irradiation light 6a that is incident on the surface of the hologram disk 3a at an angle θa, for example. The so-called irradiation light 6a is sinθa −
5jnθal=nλ/(d+△d), the diffracted light 7a is diffracted at a diffraction angle θa1 so as to converge at the convergence position of the diffracted light 7.
becomes. That is, in order to converge the diffracted light 7a by the hologram disk 3a to the convergence position of the diffracted light 7 by the hologram disk 3, the angle of incidence on the hologram disk 3a is determined according to the pinch change amount Δd of the interference fringes. θ
It should be a. Therefore, by rotating the mirror 2, it is possible to correct the elongation caused by high-speed rotation of the hologram disk. FIG. 3 is a diagram showing essential parts of another embodiment of the present invention.

In FIG. 3, when the hologram disk 3 of the film rotates at high speed and becomes 3a and elongates as in FIG. 2,
The correction of the convergence position of the diffracted light by the hologram disk 3a is performed by moving the mirror 2 parallel to the surface of the hologram disk 3a according to the elongation of the hologram disk 3, and then rotating it.

That is, even if the mirror 2 is moved parallel to the hologram disk 3a surface by the amount of elongation, it is not necessarily possible to converge the diffracted light 7 at the convergence position.

Therefore, the amount that cannot be corrected only by parallel movement of the mirror 2 can be corrected by rotating the mirror 2. This moves the mirror 2 parallel to the hologram surface from the position indicated by the solid line to a predetermined position according to the elongation of the hologram disk 3,
A state 2b indicated by a broken line is assumed, which is an incident angle θb to the hologram disk 3a. Therefore, as explained in FIG.

According to the relational expression sinθb−sinθb+=nλ/d+Δd, the diffracted light 7b is converged by the hologram disk 3 at the same position as the convergence position of the diffracted light 7 at the diffraction angle θ. Here, λ is the wavelength of the light used, and d and Δd are the pitch of the interference fringes of the hologram recorded on the hologram disk and the amount of change in the pitch of the hologram interference fringes depending on the elongation of the hologram disk.

(7) Effects of the Invention As explained in detail above, the optical scanning device of the present invention achieves convergence by changing the diffraction angle due to the pinch change of the interference fringes of the hologram due to the elongation caused by rotating the film hologram disk at high speed. There is a highly effective method that can converge the diffracted light by a hologram to the correct position by moving the mirror once, even if the position has shifted. In addition, since hologram disks can be made from film, they are lightweight and low-cost, which is a useful feature.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an optical scanning device according to an embodiment of the present invention. FIG. 2 is an enlarged view of the main part of FIG. 1, and FIG. 3 is an enlarged view of the main part of another embodiment of the present invention. 1...Laser device, 2...Mirror. 3.3a... Hologram disk, 4... Position detector, 5... Mirror drive unit. 6...Coherent light, 6a...Irradiation light, 7
．． 7a, 1a+, 7b+...diffraction light

Claims (2)

[Claims] (1) In an optical scanning device using a hologram disk, an optical scanning line is detected at a position perpendicular to the scanning direction by diffracted light from the continuously rotating hologram,
A position at which the hologram is irradiated with light so as to scan to a predetermined position based on the detection. An optical scanning device characterized by being provided with a means for changing the angle. (2) The optical scanning device according to claim 1, wherein the means for changing the position and angle at which the hologram is irradiated is by moving a reflecting mirror nine times.