JPH0243256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording and reproducing apparatus for optically recording and reproducing information on a recording medium such as a disk.

Conventionally, optical recording and reproducing devices rotate a disk coated with a photosensitive material, and emit a minute spot of light from a laser or the like onto the disk to a diameter of 1 μm or less, so as to follow the fluctuations of the disk surface. By irradiating the disc with focus control and modulating the intensity of the light output with a recording signal, information such as video signals is recorded on the disc as irregularities or changes in optical properties such as refractive index and reflectance. , an apparatus has been proposed that reproduces the information by detecting the change in the optical characteristics.

In such devices, in order to increase the density of recording tracks, guide tracks are provided in advance in concentric circles or in a spiral shape to guide the tracks to be recorded on the disk, and tracking is performed so as to follow the guide tracks. A system has been devised that writes information to a predetermined track under control and reproduces information from that track.

However, such devices are susceptible to vibrations, shocks, etc., and if there is a disturbance during recording, the tracking control or focus control becomes erroneous, causing the problem that information that should have been recorded is not recorded and cannot be reproduced. Therefore, it is possible to construct the legs of the device with dampers such as rubber or springs, but the effect against vibrations is insufficient, and in the end, an inspection is performed after recording to the disk is completed to look for recording errors and correct them. I had to.

In view of the above points, the present invention detects an abnormality in recording operation due to disturbance such as vibration or shock, and avoids recording in an abnormal state.One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of the recording and reproducing operation, in which 1 is a semiconductor laser, 2 is a condensing lens for condensing the light of the semiconductor laser 1, and 3 and 4 are perpendicular to the junction surface of the semiconductor laser 1. These are concave and convex cylindrical lenses for correcting laser light having different divergence angles in the direction and the horizontal direction, and the cylindrical lenses 3 and 4 have a lens action only in the horizontal direction with respect to the cemented surface. It is a cylindrical lens. 5 is a tracking mirror, 7 is its driving device, which is configured like a galvanometer, and the tracking mirror 5
Tracking control is performed by rotating the . 6 is an aperture lens with a diameter of approximately
Creates a minute spot light of 1μm. Reference numeral 9 denotes an aperture lens drive device composed of something like a voice coil, which moves the aperture lens 6 according to the surface deflection of the disk 8, so that the focus of the minute spot light is always irradiated onto the disk 8. The focus is controlled like this. 13 is a disk motor that rotates the disk 8; 10 is a beam splitter that changes the reflected light from the disk 8 as shown; 11 is a convex lens; the convex lens 11 and the convex cylindrical lens 4 eliminate astigmatism in the reflected light. It has the effect of giving. In other words, the condensing position of the reflected light from the disk 8 in the direction where the convex cylindrical lens 4 is acting as a lens is A, and conversely, the condensing position of the reflected light from the disk 8 in the direction where the convex cylindrical lens 4 is not acting as a lens is A.
In other words, the reflected light is focused at different locations. 12
is a photodetector divided into four parts, which detects changes in the shape of the reflected light according to the surface wobbling of the disk 8 due to the effect of the astigmatism to obtain a focus error signal.

FIG. 2A is a cross-sectional view of the disk 8 along the radial direction, and one surface 8a of the disk 8 has a width T _W ,
A groove X having a pitch T _P and a depth T _D is formed in a concentric or spiral shape. A photosensitive recording material (not shown) is applied from one side 8a, and then a protective layer or the like (not shown) is applied thereon. The minute spot lights are emitted, for example, from the other surface 8b side, and are connected on one surface 8a. Specific values of the width T _W , pitch T _P , and depth T _D are, for example, width T _W =0.6μ.
m, pitch T _P =1.6 μm, and depth T _D =1000 Å.

When recording information on the disk 8, the groove x becomes a guide track, and tracking control is applied to this guide track, and focus control is applied based on the focus error signal, so that the minute spot light is always Disc 8 groove x
By changing the light intensity of the minute spot light, the disk 8 is illuminated with:
For example, information is recorded as pits with changes in light reflectance.

Next, a method of applying tracking control to the groove x of the disk 8 will be briefly explained. disk 8
The photodetector 12, which detects reflected light, is divided into four parts 12a to 12d, as shown in FIG. This photodetector 12 is arranged with respect to the groove x as shown in FIG.
It is obtained by taking the difference in the amount of received light with c. That is, FIG. 2B shows the photodetectors 12a and 12c when the minute spot light crosses the groove x.
In the output waveform diagram, for example, a is the output waveform of the photodetector 12.
a and c respectively indicate the amount of light received by the photodetector 12c, and e in FIG. becomes.

As an embodiment of the means for detecting an abnormality in the recording operation of the present invention in the optical recording/reproducing apparatus as described above, a case where an error signal of tracking control is used will be explained with reference to the circuit block diagram shown in FIG. . 14 and 15 are amplifiers;
amplify the outputs of the photodetectors 12a and 12c, respectively. A differential amplifier 16 takes the difference between the outputs from the amplifiers 14 and 15 to generate the tracking error signal. 17 is a phase compensation circuit necessary for control, 18 is an amplifier, and 19 is a drive circuit. The output of the drive circuit 19 is connected to the drive device 7 of the tracking mirror 5, and rotates the tracking mirror 5. As a result, the minute spot light is made to follow the eccentricity of the guide track. 20 and 21 are comparators, and when the tracking error signal from the amplifier 18 is larger than +V ₁ , the comparator 20
The output signal of the comparator ₂₁ becomes high level, and when it is smaller than -V2, the output signal of the comparator 21 becomes high level. At other times, comparators 20 and 21
The output signal of is low level. 22 is an OR circuit, and 23 is an RS flip-flop circuit. When either of the output signals from the comparators 20 and 21 is at a high level, the output signal of the OR circuit 22 is at a high level, and the RS flip-flop circuit 2
3 maintains this high level until a reset signal is input to the R terminal, and is input via the changeover switch 24 to a control circuit 25 that controls the operation of the entire device. In addition, the changeover switch 24
The RS flip-flop circuit 23 is used only during recording.
and a control circuit 25, and during playback, a low level is input to the control circuit 25, and when a high level is input from the changeover switch 24, the control circuit 25 stops emitting light from the semiconductor laser 1, etc. is configured to do so.

Conventionally, when disturbances such as vibrations and shocks are applied to the apparatus from the outside, the error signals of the tracking control and focus control become large, and the minute spot light becomes large, resulting in poor recording conditions or the control being deviated. The minute spot light may completely deviate from the guide track or focus position, making it impossible to record and reproduce normally. At this time, the amplifier 18
As shown in FIG. 5, an error signal corresponding to the magnitude of disturbance such as vibration is output from the sensor. The error signal is +
Since normal recording cannot be performed in a state exceeding the V ₁ or -V ₂ level, recording is abnormal or not performed in the range Y in FIG. 5.

Therefore, the abnormality detection means having the above configuration detects that the recording state becomes abnormal by detecting that the tracking error signal exceeds the +V ₁ and -V ₂ levels, and stops the semiconductor laser 1 from emitting light. This interrupts the recording operation. That is, when the error signal attempts to exceed the range of +V ₁ to -V ₂ due to a disturbance such as an attack, the comparators 20 and 21
operates, and the comparator 20 outputs a high level for an error signal of +V ₁ or more, and the comparator 21 outputs a high level for an error signal of -V ₂ or less, so the output of the OR circuit 22 outputs a high level for an error signal of +V ₁ or more and High level at −V ₂ or less. This high level is held by the RS flip-flop 23, and the changeover switch 2
The signal is input to the control circuit 25 via the control circuit 4, and the emission of the semiconductor laser 1 is stopped. Therefore, the recording operation is stopped in an abnormal state, and recording is always performed in a normal state. After the disturbance has subsided, a reset signal is sent to the R terminal of the RS flip-flop 23, and recording is restarted from the point where the recording was interrupted.

In the above embodiment, an example was explained in which recording is stopped when an abnormality is detected, but it is also possible to simply display a recording error and manually correct or change the recording track. It's okay. Further, as a signal for detecting an abnormality, a focus control error signal may be used instead of a tracking control error signal. Furthermore, in the embodiment described above, recording in an abnormal state can be prevented by detecting in advance that an abnormality occurs in recording and reducing the output of the semiconductor laser to an output that cannot be recorded.

As described above, according to the present invention, in an optical recording/reproducing device that is relatively susceptible to vibrations and shocks, recording errors due to the effects thereof can be prevented. Furthermore, as a result, it is no longer necessary to inspect all tracks after recording is completed as in the conventional method, and information can be recorded on the recording medium efficiently and with a high yield.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is an explanatory diagram of recording and reproducing operations, FIG. 2A is an enlarged sectional view of a disk, FIG. 2B is an output waveform diagram of a pair of photodetectors, and FIG. is a waveform diagram of the difference signal between the outputs of a pair of photodetectors,
FIG. 3 is an explanatory diagram of the positional relationship between the photodetector and the guide track, FIG. 4 is a circuit block diagram of means for detecting an abnormality in recording operation, and FIG. 5 is a waveform diagram of a tracking error signal. 1... Semiconductor laser, 8... Disk, 12...
...Photodetector, 16...Differential amplifier, 20, 21...
...Comparator, 22...OR circuit, 23...RS
Flip-flop circuit, 24...changeover switch.

Claims (1)

[Claims] 1. In an optical recording and reproducing apparatus that irradiates a disk-shaped optical recording medium with a laser beam or the like under focus control and records and reproduces information while applying tracking control using a track guide means that guides a recording and reproducing track, the above-mentioned An optical system comprising means for detecting that an error signal of at least one of focus control or tracking control exceeds a predetermined value, and the recording operation is stopped when the detecting means detects an error signal exceeding the predetermined value. Recording and reproducing device.