JPS6138531B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention focuses light such as a laser to a minute diameter and irradiates it onto a disc-shaped disk coated with an optical recording material.
It is related to equipment that records signals at high density and monitors playback.

2. Description of the Related Art Conventionally, as an optical recording and reproducing apparatus as described above, there is a machine that creates a master disc of a video disc. This type of device has a short wavelength laser for recording and a long wavelength laser for playback monitoring for a disk coated with photoresist or the like, or a disk coated with a thin metal film. The recording quality is monitored by performing high-density recording and checking the quality of the reproduced signal in the latter. For example, published patent publication,
No. 2415 discloses a technology related to the above-mentioned system.

This technology has a short wavelength, high output recording laser and a long wavelength, low output reproduction laser.
By focusing each laser beam with a single objective lens and slightly shifting the position of each aperture on the recording track, monitoring is performed to check whether the recording and recording quality are good. .

This device is used to concatenate and record signals on a disk in a spiral manner, but the device is complicated due to the presence of a circular light source, and requires high-precision adjustment to align the optical axes of each point. It becomes necessary.

Therefore, a device that can monitor recording and playback using a single light source is desired.

On the other hand, non-contact optical recording/reproducing devices require tracking control during playback and focusing control during recording and playback. The latter will be explained using FIGS. 1a, b, and c.

In Fig. 1, a, b, and c show the relationship between the disk and the light beam, respectively. Fig. 1 a shows a state where the beam waist is aligned with the disk surface, and b and c show the beam waist, respectively. This shows a state in which the discs are shifted above and below the disk. During recording, the state shown in FIG. 1a is desirable in order to minimize recording energy and enable recording of short wavelength signals. but,
When performing tracking control during playback, the control system operates so that the light transmitted through the disk is received by a light-receiving element arranged in parallel in a direction perpendicular to the recording track, and the output difference becomes zero. Since the system becomes unstable in state a, it is necessary to perform focusing control to state b or c.

SUMMARY OF THE INVENTION Therefore, the present invention is intended for use in an optical recording and reproducing apparatus that concentrically records still image signals on a rotating disk at least one frame per track, for example, for recording and reproducing monitoring using a single light source. , in response to a recording command, generates a recording interval signal with a pulse width corresponding to a servo switching interval signal and one rotation period of the disc that occurs later than the servo switching interval signal in relation to the rotation of the disk, and performs tracking control during the servo switching interval signal. put the system into a non-operating state, control the focus control system to a state suitable for recording, perform recording during the recording interval signal,
After the completion of both signals, the tracking control system is switched to an operating state and the focus control system is switched to a state suitable for playback, thereby enabling playback monitoring.

FIG. 2 shows an embodiment of the present invention.

Reference numeral 1 indicates a light source such as a laser, which generates a light beam a. 2 indicates an optical modulator, in which an electro-optic modulator or an acousto-optic modulator is used, which changes the intensity of incident light a to generate weak transmitted light b when reproducing a signal, and generates weak transmitted light b when recording a signal. Then, the transmitted light b is optically modulated according to the recording signal. 3 is a beam splitter consisting of an intermediate lens, 4 and 5 are half mirrors, which allows the transmitted light b to pass through and guides the reflected light from the disk to a focus detector, which will be described later. 6 is a tracking mirror, which is a well-known tracking mirror. control. Reference numeral 7 denotes an objective lens that focuses the light c reflected by the tracking mirror and irradiates it onto the disk. Reference numeral 8 indicates a voice coil fixed to an objective lens, which is used for performing known focus control. 9 is a disk coated with optical recording material, 10 is a disk motor, and 11 is a step motor, and the disk motor is moved by a fixed interval in response to a transfer command pulse. Reference numeral 12 denotes a photodetector for detecting light transmitted through the disk, and is composed of, for example, two divided pin diodes 12a and 12b. 13a and 13b are preamplifiers that amplify the output of each pin diode;
Reference numeral 14 indicates a differential amplifier that takes the difference between the outputs of the preamplifiers 13a and 13b. Reference numeral 15 indicates a switch circuit that is controlled to be turned off when the servo switching period signal A applied to the control terminal is at a high level and turned on when it is at a low level.
b. The function of the tracking servo system composed of the differential amplifier 14, the tracking mirror 6 and the light c is activated or deactivated.

16 is a photodetector that detects the reflected light on the disk 9 split by the beam splitter 5;
It is composed of a pair of photodetecting elements 16a and 16b. 17a, 17b are preamplifiers that amplify the output of the photodetecting element; 18 are preamplifiers 17a, 1;
7b shows a differential amplifier that takes the difference between the outputs of 7b. Similarly, 19 is a photodetector that detects the reflected light on the disk 9, and is composed of a pair of photodetection elements.
The respective outputs are composed of preamplifiers 20a and 20b, and a differential amplifier 21 calculates the difference. Reference numeral 22 denotes a switch circuit, which is connected to the terminal 22a when the servo switching signal A applied to the control terminal is at a high level corresponding to recording, and to the terminal 22b when it is at a low level corresponding to reproduction. 23, the voice coil 8 is connected by the output of the switch circuit 22.
It is an amplifier that drives the. The receivers 16 and 19 are
In order to realize different focus states during recording and playback as shown in Fig. 1 a, b or c,
The boundaries of the sensing elements are arranged so that they differ by a predetermined width.

24 is an FM modulator that performs FM modulation on the image signal to be recorded, which is applied from the recording signal input terminal. 2
Reference numeral 5 denotes a switching circuit which is turned on when the recording interval signal I applied to the control terminal is at a high level, and sends a modulation signal to the optical modulator 2 to modulate the light beam and enable recording on the disk. 26 is a synchronization separation circuit that extracts the vertical synchronization signal shown in FIG. 3E from the input signal, and 27 is a circuit that generates a rotation synchronization pulse U that is generated once every time the disk rotates once as shown in FIG. 3C. be. 28 compares the output of the synchronization separation circuit 26 of the recording signal with the rotational synchronization pulse U, and as shown in FIG. This is a disk motor drive circuit that drives the motor that drives the disk.

Reference numeral 29 denotes a pulse generating circuit that generates a servo switching interval signal A and a recording interval signal B based on the rotation synchronization pulse W and recording command input. The servo system for tracking and focusing requires response time for the switches 15 and 22, and time for the servo system itself to stabilize.
The servo switching section signal A is generated prior to the recording section signal A by at least the servo response time, and recording is performed for one revolution of the disk, and the recording section signal ends, and the servo switching section signal A also ends. do.

FIG. 4 shows an example of the configuration of the pulse generating circuit 29 shown in FIG. When the recording command signal O shown in FIG. 3A is input, the _J1 input of the JK flip-flop 42 becomes high level, and the output of the inverter ₄₁ is added
Since the input is at a low level, the synchronizing pulse from the rotation synchronizing pulse generation circuit 27 applied to the clock terminal causes the output _Q1 to go high, and since the _three outputs of the flip-flop 44 are at a high level at this time, the AND circuit 45 output becomes high level. Furthermore, when the output _Q2 of the JK flip-flop 43 is at a high level due to the next synchronous pulse,
The output of the AND circuit 46 also becomes high level. The outputs of these AND circuits 45 and 46 are output to the JK flip-flop 44 by the third synchronous pulse.
Since the _three outputs are kept in the high state until they become low level, the servo switching section signal and the recording section signal as shown in FIG. 3A and FIG. 3B are obtained.

In this configuration, the pulse width of the recording command signal O needs to be set longer than the time required for three rotations of the disk, taking into consideration the maximum period from its leading edge to the leading edge of the rotation synchronizing pulse. In addition, in this configuration, when three rotation synchronization pulses occur after the end of the recording period signal O, the Q outputs of all flip-flops 42 to 44 are reset to low level, so that the next recording after the end of recording is performed. Before the command signal is input, the time required for at least three rotations of the disk must have elapsed.

Next, the operation of the servo system of the present invention will be explained. During recording, the switch circuit 15 is activated by the servo switching interval signal A from the pulse generating circuit.
is turned off, the tracking control system becomes inactive, and the switch circuit 22 closes to the terminal 22a side, so that the beam splinters 4, 5, the tracking mirror 6, the photodetector 16, and the amplifiers 17a, 1
7b, the differential amplifier 18, the amplifier 23, the voice coil 8, and the objective lens 7 constitute a focus control system. The main parts of this control system are shown in FIG.

In Fig. 5, the distance between the two where the beam is most focused on the disk surface by the objective lens 7 is h ₂
At this time, the reflected light from the disk surface passes through the mirror 6 beam splitter 4 to the photodetector 16.
The photodetector 16 is fixed so as to reach a point A on the boundary between the photodetecting elements 16a and 16b at the top.
In this state, the outputs of the elements 16a and 16b are the same, and the focus control system is stable. If, during disk rotation, the distance between the objective lens and the disk surface is reduced to h ₁ due to uneven thickness of the disk, for example, the light reflected from the disk surface will be reflected at point B of the focus servo photodetector 16. reaches the top, and the outputs of the photodetecting elements 16a and 16b are 16b
becomes larger, an output difference is obtained from the differential amplifier 18, and this output difference drives the voice coil 8 via the amplifier 23 until the distance between the objective lens 7 and the disk surface reaches _h2 . The objective lens is pushed upward. Conversely, if the distance between the objective lens 7 and the disk surface is _h3 , the photodetector 16
The reflected light reaches the upper point C, and the detection element 16a, 1
6b is reversed, and the voice coil 8 is pushed down until the distance between the objective lens 7 and the disk surface becomes _h2 . In this way, the distance _h2 between the objective lens and the disk surface is always maintained.
As shown in , the most narrowed part of the light beam hits the disk surface.

On the other hand, during playback, the servo switching interval signal A is at a low level, the switch circuit 15 is turned on, and the tracking mirror 6, objective lens 7, photodetector 12, amplifiers 13a and 13b, differential amplifier The tracking control system consisting of the width switch 14 becomes operational, and at the same time the switch circuit 22 is connected to the terminal 22b.
side closed, beam splitter 4, 5, photodetector 1
9, a focus control system including amplifiers 20a, 20b, a differential amplifier 21, and an amplifier 23 is configured.

Here, as mentioned above, in the photodetector 19, the boundary line between the photodetecting elements 19a and 19b is
Or to achieve a focus state like c.
It is fixed at a position optically shifted from the photodetector 16. Now, suppose the focus control system is designed to be stable with the beam waist above the disk as shown in Figure 1b.
The relationship between the transmitted beam and the photodetecting elements 12a and 12b is as shown in FIG. and is always controlled to be in an on-track state.

In this embodiment, when the recording command signal O is generated as shown in FIG. 3, the servo switching section signal rises with the rise of the first pulse of the rotation synchronization pulse U that occurs every one rotation of the disk, and this causes the servo switching interval signal to rise. switch circuit 15 to OFF, switch circuit 2
2 to the 22a side, and focus control for recording as described above is started. With the subsequent rise of the rotation synchronization pulse, the recording section signal A rises.
By the time the image signal FM modulated by the FM modulator 24 is applied to the modulator 2 and recording is started, the servo system is in a stable state. When recording is performed for one rotation of the disk and both the servo switching section signal A and the recording section signal B disappear due to the next rotation synchronization pulse, the tracking control system becomes operational as described above. Focus control for playback is started, and at the same time switch circuit 2
5 is turned off, and the recording signal can be reproduced and monitored using a relatively weak beam obtained through the modulator 2. The reproduced signal is transmitted to the photodetector elements 12a, 1
2b through amplifiers 13a and 13b in adder 30, and demodulator 3
1 and can be monitored immediately after recording on the monitor 32.

As is clear from the above description, the optical recording and reproducing apparatus according to the present invention has a servo system suitable for recording and reproducing, and switches the servo system in response to recording command input and disk rotation. This allows recording and monitoring with a single light source.

[Brief explanation of the drawing]

1a, b, and c are diagrams showing focus states during recording and reproduction in an optical recording/reproducing apparatus, and FIG. 2 is a block diagram showing the configuration of an embodiment of the optical recording/reproducing apparatus according to the present invention. , Figure 3 is the second
4 is a block diagram showing the configuration of the pulse generation circuit 29 in FIG. 2, and FIG. 5 explains the operation of the focus control system in the optical recording/reproducing apparatus shown in FIG. 2. diagram for,
FIG. 6 is an explanatory diagram of the operation of the tracking control system in FIG. 2. 1... Light source, 2... Modulator, 4, 5... Beam splitter, 6... Tracking mirror, 7...
Objective lens, 8... Voice coil, 9... Disk, 12, 16, 19... Photodetector, 14, 1
8, 21... Differential amplifier, 15, 22, 25...
Switch circuit, 24...FM modulator, 26...Synchronization separation circuit, 27...Rotation synchronization pulse generation circuit,
28...Disc motor drive circuit, 29...Pulse generation circuit, 30...Addition circuit, 31...Demodulation circuit, 32...Monitor.

Claims (1)

[Claims] 1. In a device that records and reproduces a signal such as a still image of at least one frame per rotation on a disk by irradiating a light beam from a light source such as a laser, different beam focus states are realized during recording and reproduction. a control system that performs tracking control during playback; a means for generating pulses in synchronization with the rotation of the disk; and a recording command signal and the pulse that cause the disk to rotate once. means for generating a recording interval signal having a pulse width corresponding to a period; and generating a servo switching interval signal that starts before the recording interval signal and whose trailing edge is not earlier than the recording interval signal, from the recording command signal and the pulse. means for selecting one of the first and second focus control systems and switching the tracking control system to one of a non-operating state and an operating state according to the servo switching interval signal; 1. An optical recording/reproducing device comprising: means for modulating a light beam from a light source during a period of time.