JPS6321168B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an optical scanning device, and more specifically, an optical scanning device that obtains a synchronization signal for starting scanning by detecting a change in the intensity of zero-order light during hologram reproduction. .

2. Description of the Related Art Conventionally, a method is well known in which a light beam is incident on a hologram made by interfering two beams of light and the light beam is scanned by moving the hologram. In this method, for example, it is common to arrange multiple holograms on the same circumference of a disc-shaped medium and perform multiple scans in one rotation, but in this case, each hologram must be arranged at equal pitches. The starting point of the scan differs from scan to scan, eventually causing image jitter. In order to prevent this, efforts have been made to improve the precision of machines and other equipment when recording holograms so that they can be arranged accurately at equal pitches. However, this has the disadvantage that it is technically difficult and the recording apparatus becomes expensive.

The present invention has been made to overcome the above-mentioned drawbacks of conventional devices.

An object of the present invention is to provide an optical scanning device that can perform scanning without causing a jitter phenomenon even if the hologram is recorded without any special enhancement of mechanical or other precision.

The above object of the present invention is achieved by detecting a change in the intensity of zero-order light during hologram reproduction and obtaining a synchronization signal for starting scanning.

Next, the present invention will be described with reference to the accompanying drawings showing preferred embodiments thereof. First, a hologram optical deflector will be described with reference to FIGS. 1 and 2.
FIGS. 1 and 2 are a plan view and a side view, respectively, showing a hologram creation method. In those figures,
A and B are coherent beams, A is a diverging wave originating from point 0, and B is a converging wave converging to point 0'. The interference fringes of both waves are recorded on the surface of the photosensitive material S. A kind of off-axis Fresnel zone plate is then recorded on the photosensitive material S. This recording is a hologram, and its basic property is that when beam A is made incident on it, beam B is reproduced, and conversely, when beam B is made incident on it, beam A is reproduced. As shown in FIG. 3, when a part of the diverging wave A from 0 during recording is made incident on the hologram, a part of the converging wave B during recording is reproduced. At this time, when the hologram is moved in the direction of the arrow, the diffraction angle of the reproduction light beam changes successively, resulting in the light being scanned. Actually, the fourth
As shown in the figure, multiple holograms are placed side by side on the same circumference and are constantly rotated by a motor.
An optical deflector is realized by inputting fixed illumination light for reproduction into this. In the same figure, 1
is a hologram disk around which a plurality of holograms 3 are arranged; 2 is a motor for rotating the disk; 4 is a zero-order beam; and 5 is a photodetector such as a photodiode.

Now, in such a hologram optical deflector, when N holograms exist on the recording medium,
The light is scanned N times during one rotation of the recording medium. At this time, if the holograms are not arranged at equal pitches on the circumference, the scanning start point of each scanning line will be different, and jitter will appear in the image.

In order to prevent this image jitter phenomenon, the present invention detects the zero-order light from the hologram, generates a synchronization signal to start scanning, and reads or writes information based on this signal. The objective is to obtain an image free of jitter.

To explain again with reference to FIG. 4 showing an embodiment of the present invention, a photodetector 5 is disposed in the zero-order light 4 that has passed through the hologram 3, and when the disk 1 is rotated, the photodetector 5 is The output is as shown in Figure 5a. That is, while the incident beam is incident on the hologram, the level of the 0th-order light decreases because the light is diffracted toward the 1st-order diffracted light. When the incident beam is placed between the holograms, there is no diffracted light, so the level of the zero-order light increases. The resulting output signal from the photodetector is as seen in Figure 5a.
The falling edge of the pulsed signal output between the holograms is the point at which the holograms start scanning. Even if the holograms are not arranged at equal pitches due to recording errors, the scanning start point can be accurately determined by detecting this falling edge. To detect the falling edge, for example, by inputting the output from the photodetector 5 to the trigger circuit of the mono multivibrator, it is possible to generate a pulse of any width at the falling edge of the signal, and the fifth
Figure b shows how this pulse is generated. If the image signal is read or written based on this pulse, it is possible to obtain a high-quality image free from jitter phenomena.

From the above explanation, even if the hologram is recorded without particularly increasing the accuracy of the machine or other equipment,
It has been revealed that an optical scanning device capable of scanning without causing jitter phenomenon can be obtained.

[Brief explanation of the drawing]

Figure 1 is a plan view to explain the method of creating a hologram, Figure 2 is a similar side view, and Figure 3 is a diagram to illustrate the angular deflection of the beam resulting from successive reproductions of different parts of the original beam. 4 is a schematic diagram showing an embodiment of the present invention, FIG. 5a is a waveform diagram showing a signal from the photodetector 5, and FIG. 5b is a diagram showing a pulse generation state.

Claims (1)

[Claims] 1. In an optical scanning device that makes a light beam enter a hologram made by interfering two beams of light and scans the light beam by moving the hologram, the intensity change of zero-order light between holograms occurs when the hologram is reproduced. is detected by a photodetector, the fall of the output signal from the photodetector is input to a mono-multivibrator, and a synchronization signal for starting scanning is obtained based on the pulse from the mono-multivibrator. Optical scanning device.