JPS61287043A - Focus controller - Google Patents

Abstract

PURPOSE:To improve the reliability of a recording/reproducing signal by providing a focus error signal detection circuit detecting that a defocus quantity is deviated from the prescribed quantity. CONSTITUTION:When defocus takes place at recording of information and an output of a focus errorsignal being an output of a differential amplifier 9 reaches a prescribed level, a defocus detection circuit 21 outputs a recording stop signal to a semiconductor laser drive circuit 16 to allow a semiconductor lasder 1 to generate a reproduced light quantity. Further, a CPU 20 stops the transfer of recording information to a recording information buffer memory 18 and after focus control is stabilized, the information recorded at defocus is recorded succeedingly or recorded on another track newly. When defocus takes place at the reproduction of signal, the CPU 20 stops the transfer of the reproducing information to an external bus 17 and after the focus control is stabilized, the track reproduced at defocus is reproduced again.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical information recording/reproducing apparatus for recording signals on a record carrier having tracks formed with unevenness or for reproducing recorded signals. And,
In particular, a focusing means for focusing and irradiating the light beam, a focusing state detection means for detecting the focusing state of the light beam on the record carrier, a moving means for moving the focusing means in a direction perpendicular to the surface of the record carrier, and a focusing means for moving the focusing means in a direction perpendicular to the surface of the record carrier; The present invention relates to a focus control device having a focus control means that drives a moving means in accordance with a signal from a state detection means and controls the focus state of a light beam on a record carrier to always be in a predetermined state.

Conventional technology There are various types of record carriers used in optical information recording and reproducing devices. Tracks are formed on the surface of a base material such as acrylic (commonly known as acrylic) with a concentric or spiral uneven structure, and a recording material film that can be optically recorded and reproduced is formed on the track by means such as vapor deposition. (hereinafter referred to as a disk).

For example, a focus control device for an optical information recording/reproducing device using such a disk is disclosed in Japanese Patent Application No. 58-43.
There is something like the specification of No. 517.

FIG. 6 is a block diagram showing the configuration of a conventional 7-orcus control device, which will be explained below.

A light beam generated by a light source 1 such as a semiconductor laser is collimated by a coupling lens 2, reflected by a polarizing beam splitter 3, and passed through a λ/4 plate 4 (λ is the wavelength of the light beam). The light is focused by a focusing lens 6 and irradiated onto a disk 7 which is being rotated by a motor 6.

The reflected light from the disk 7 is passed through a focusing lens 5. λ/4 plate 4
．． The light passes through the polarizing beam splitter 3 and is irradiated onto a photodetector 8 having a three-part structure.

The direction of the dividing line of the photodetector 8 having a three-part structure is set to coincide with the tangential direction of the track on the disk 7 onto which the light beam is irradiated in a predetermined focused state.

The sum signal of the output cam and the output C of the photodetector 8 and the signal of the output B are respectively input to a differential amplifier 9, and the differential amplifier 9 outputs a difference signal between the two signals.

At this time, the difference signal output from the differential amplifier 9 is D.

The signal representing the focused state of the light beam on the lens, that is, the focus error signal representing the relative positional relationship in the vertical direction between the disk 7 and the focusing lens 5, is shown in Fig. e, a, b,
This is explained by c.

6a, b, and c show the image formation state of the light beam on the photodetector 8 with respect to the relative distance between the focusing lens 6 and the disk 7. FIG. Note that the same numbers are used for the same parts as in FIG.

Fig. e a shows a case where the focusing lens 6 is too far away from the disk 7, and in this case, the sum of the light amounts of the light receiving surface M and the light receiving surface C and the light amount of the light receiving surface B are not equal, and the differential amplifier 9 has a positive ( or negative) output appears.

FIG. 6 shows that when a light beam is focused and irradiated onto the disk 7 in a predetermined focused state, the sum of the light amounts on the light receiving surface M and C is equal to the light amount on the light receiving surface B, and the output of the differential amplifier 9 is zero. It is.

FIG. 6C shows a case where the focusing lens 6 is too close to the disk 7. At this time, the sum of the light amounts of the light receiving surface M and the light receiving surface C and the light amount of the light receiving surface B are not equal, and the differential amplifier 9 has a negative (or positive) output appears.

For example, if the light receiving surface C is configured to take the difference in the amount of light between the light receiving surface M and the light receiving surface C, the error signal will be a signal representing the relative positional relationship between the light beam and the track on the disk 7 (hereinafter referred to as a tracking error signal). ).

Therefore, if the tracking element is configured so that the focusing lens 6 can be moved in a direction perpendicular to the track direction on the disk 7, and a tracking error signal is applied to the tracking element, the light beam on the disk 7 will always scan the track. Tracking control can be performed as follows.

Incidentally, the output of each of the photodetectors 8 having a three-division structure is also input to a combining circuit 14, and the combining circuit 14 outputs a sum signal of the outputs of each of the photodetectors 8 having a three-part structure to an output terminal 16. do.

The sum signal output from the output terminal 16 indicates the amount of light beam reflected from the disk 7.

Therefore, in a state where tracking control is performed so that the light beam on the disk 7 always scans the track,
Information recorded on the tracks of the disk 7 can be reproduced by processing the signals obtained based on the amount of reflected light.

Problems to be Solved by the Invention In the conventional technology, focus control is performed so that a light beam is irradiated onto a track on a disk in a predetermined focused state. If the recording/reproducing device is subjected to disturbances such as vibrations or shocks, the light beam will no longer be irradiated onto the disk in a predetermined focused state (this state of the light beam is called defocusing), and the reliability of the device will deteriorate. There was a problem of decreased sex.

For example, if defocus occurs during playback, the spot of the light beam on the disc (hereinafter referred to as the optical spot) becomes larger, so it is necessary to apply an appropriate amount of light to the part of the track where information is actually recorded. The amplitude of the reproduced signal obtained by processing the amount of reflected light decreases, making it impossible to demodulate accurately.

Furthermore, if defocus occurs during recording, signals may not be recorded because an appropriate amount of light cannot be applied to the area where information should originally be recorded.

Further, during defocusing, the tracking control becomes unstable, and track skipping (a light spot on a certain track deviates from that track) is likely to occur.

If track skipping occurs during playback, the expected playback signal cannot be obtained. Furthermore, if track skipping occurs during recording, not only will a signal not be recorded on a predetermined track, but the worst result will be that information already recorded on another track will be damaged.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a device that can reliably record or reproduce information even when defocusing occurs due to external vibrations or shocks. It is.

Means for Solving the Problem In order to achieve this object, the present invention detects, based on the signal of the focusing state detection means, that is, the focus error signal, that the focusing state of the light beam on the record carrier has deviated from a predetermined state, that is, A defocus detection means is provided for detecting the occurrence of defocus.

Effects of the present invention The defocus detection means detects the occurrence of defocus, and when recording, the output of the light source is immediately set to the reproduction light intensity, so that damage to other tracks can be prevented, and defocus can be prevented. Since the system detects the occurrence of the problem and performs recording again, it is possible to reliably record a high-quality signal.

Furthermore, during playback, if defocus occurs, it is detected and playback is repeated again, making it possible to play back high quality and reliable signals.

Example Embodiments of the present invention will be described in detail using the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. Components similar to those in FIG. 6, which is a configuration diagram of a conventional focus control device, are given the same numbers, and their explanations will be omitted.

The information to be recorded is stored in the recorded information backup memory 18 via the external bus 17 by the CPU 20 which controls input/output of external information to the optical recording/reproducing device.

The recorded information buffer memory 18 is composed of two parts, B and B. During recording, the recorded information is divided into information blocks of a certain size, and the divided information is alternately transferred to the recorded information buffer memory 18 and B. do.

Further, the CPU 20 transmits a recording gate signal to the semiconductor laser drive circuit 16, and while the signal is being output, a recording signal is sent to the semiconductor laser drive circuit 16 from the recording information buffer memory 1, and the information is recorded. It will be done.

FIG. 2 is a diagram showing the timing of the recording gate signal and the recording signal when the light beam is in a predetermined focused state, that is, when the output of the focus error signal is approximately zero, and the waveform & is a diagram showing the timing of the recording gate signal. , waveform S indicates a recording signal, and waveform C indicates a focus error signal, respectively.

By the way, the recorded information is divided into blocks 31 of a certain size as shown in the waveform of FIG. Since the information is sent to the semiconductor laser drive circuit 16 and recorded, even if defocus occurs during recording and recording is stopped, the recorded information of that block will certainly remain in the recording buffer memory 18.

In addition, when reproducing information, as described in the related art section, a reproduced signal can be obtained from the output terminal 15 of the synthesis circuit 14, and this reproduced signal is processed by the CPU 20 and sent to the external bus 17 as reproduced information. The output is rL.

Here, the defocus detection circuit 21 that detects that the light beam on the record carrier is defocused from the focus error signal provided in this embodiment will be described below.

When information is defocused during recording and the output of the focus error signal, which is the output of the differential amplifier 9, reaches a certain level, the defocus detection circuit 21 outputs a recording stop signal to the semiconductor laser drive circuit 16, and the second The output of the recording gate signal shown in FIG.

The recording stop signal is also input to the CPU 20, and in response to this input, the CPU 20 starts recording information backup memory 1 of the recording information.
Cancel transfer to 8. Further, the CI'U 20 causes the information that was recorded when the focus control is stabilized or defocused to continue to be recorded, or to record it anew on another track.

When the signal is defocused during reproduction and the output of the differential amplifier 9 reaches a certain level, the defocus detection circuit 21 outputs a recording stop signal to the CPU 20 in the same way as when recording the signal. As a result, the CPU 20 stops transferring the playback information to the external bus 17, and after the focus control becomes stable,
The track that was playing when the focus was defocused will be played again.

Next, the configuration of the defocus detection circuit 21 will be explained in more detail using FIG. 4.

FIG. 3 is a partially enlarged view of FIG. 1, and shows the configuration of the defocus detection circuit 21 and signal input/output. Components similar to those in FIG. 1 are designated by the same numbers, and their explanations will be omitted.

The defocus detection circuit 21 includes an inversion circuit 22 and a rectifier 2.
3, a rectifier 24, and a comparator 25.

One of the focus error signals output from the differential amplifier 9 is directly transmitted to the rectifier 23 and the other is transmitted to the rectifier 24 through the inverting circuit 22. The rectifier 23 rectifies the positive component of the focus error signal, and the rectifier 24 rectifies the negative component of the focus error signal. Since the focus error signal of the rectifier 24 is inverted by the inverting circuit 22, the signals output from the rectifier 23 and the rectifier 24 have the same polarity.

Rectifier 23. The output of the rectifier 24 is connected to a comparator 25, respectively.
is input. In the comparator 26, when this input signal exceeds a predetermined voltage, the output is in a high state, and when it is below a predetermined voltage, the output is in a low state, and defocus is detected as a high state.

The output of the comparator 26 is input to the CPU 20 as the above-mentioned recording stop signal, and when this output is in a high state, that is, in a defocused state, the output of the recording gate signal is dropped, and the recording information is transmitted from the external bus 17. Transfer of information to the buffer memory 18 is stopped to stop recording. Then, the CPU 20 reproduces the information of the defocused track again when the output of the comparator 26 does not change from a high state to a low state and becomes a high state even after a certain period of time, that is, when the focus control becomes stable. If the reproduced information is defocused when recording the information, the CPU 20 compares it with the information recorded in the recorded information buffer memory 18, and after confirming the correctness, the CPU 20 outputs the recording gate signal again and determines whether to continue recording again. Or record the information again on another track.

If the information is defocused during playback, 0PU20
uses this replayed information as correct information and transfers it to external bus 1.
Output to 7.

FIG. 4 shows the timing of the recording gate signal, the recording signal, and the output signal of each component in the defocus detection circuit 21 shown in FIG. 4 in the case of defocusing while recording information. In this figure, waveform a is the recording gate signal, waveform 2 is the recording signal, waveform C is the focus error signal, waveform d is the output of the inverting circuit 22, and waveform e is the rectifier circuit 23.
．． Waveform f is the output of rectifier B24, and waveform g is the output of comparator 25.

Below, FIG. 4 will be briefly explained.

As described above, when the focus error signal exceeds a certain voltage V at two points, the output g of the comparator 26 becomes high, and it is detected that defocus has occurred. At this time, the recording gate signal a drops and transmission of the recording signal is also stopped. The focus error signal is rectified by a rectifier 23.one directly and one through an inversion circuit 22. Since the signals are respectively input to the rectifier B24, defocus can be detected whether it occurs in either the positive or negative direction.

If the focus error signal is not output for a certain period of time τ, it is assumed that the focus control has been stabilized, and the recording gate signal a is output again at point Q to restart recording.

As described above, in this embodiment, the focus error signal and the shive focus amount are detected, recording and playback are stopped by outputting a signal representing the detection, and after the focus control is stabilized, the recording and playback at that time is restarted. This makes it possible to supplement information whose reliability has decreased.

Effects of the Invention As described above, by providing a focus error signal detection circuit that detects when the amount of defocus deviates from a predetermined state, the reliability of recording/playback signals that were hitherto affected by defocus is improved. It is possible to do so, and its practical effects are significant.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a focus control device according to an embodiment of the present invention, and FIG. 2 is a signal timing diagram showing the operation when information is recorded with a light beam in a predetermined focused state in the same embodiment. 3 is a block diagram showing the defocus detection circuit of the same embodiment, FIG. 4 is a signal timing diagram showing the operation when defocus occurs during recording of information in the same embodiment, and FIG. 6 is a block diagram showing the defocus detection circuit of the same embodiment. 6 is a block diagram showing the configuration of a conventional focus control device, and FIG. 6 is a diagram showing the image formation of the reflected light of the light beam on the light receiving surface of the photodetector with respect to the relative distance between the focusing lens and the disk in the conventional device. It is. 1... Semiconductor laser, 2... Coupling lens, 3... Polarizing beam splitter, 4
.....lambda./4 plate, 5 ..... focusing lens, 6
...Motor, 7.1....Disk, 8.
...Photodetector, 9...Differential amplifier, 10.
...Phase compensation circuit, 11...Switch,
12...Focusing lens drive circuit, 13...
Focusing lens driving element, 14...Synthesizing circuit, 15
. . . Synthesis circuit output terminal, 16 . . . - Semiconductor laser drive circuit, 17 . . . External lotus, 18.
...Record information buffer memory, 20...
CPU, 21... Defocus detection circuit, 22
...Inverting circuit, 23... Rectifier circuit, 2
4... Rectifier B125... Comparator, 3
1...recording signal when no defocus occurs, 32...recording signal when defocus occurs. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
111 Figure 4 Figure 5...

Claims (1)

[Claims] (1) An optical recording/reproducing device using a record carrier having an information signal recorded thereon or a track formed of unevenness for recording the information signal, wherein a light beam generated from a light source is transmitted to the record carrier. a focusing means for converging and irradiating the light beam upward; a focusing state detecting means for detecting a focusing state of the light beam on the record carrier; and movement for moving the focusing means in a direction substantially perpendicular to the surface of the record carrier. and a focus control means for controlling the moving means so that the focusing state of the light beam on the record carrier is always in a predetermined state by driving the moving means according to a signal from the focusing state detecting means; A focus control device comprising defocus detection means for detecting, based on a signal, that a focused state of the light beam on the record carrier deviates from a predetermined state.