JPH0227735B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording/reproducing device (having only one of the recording and reproducing functions) using a disk-shaped recording medium on which signals are digitally recorded as pits. (including things).

Conventional configuration and its problems When tracing recorded information on a recording medium such as a record with a record stylus, if there is a large scratch on the record, stylus skipping occurs, where the record stylus jumps to the side tracks. . Optical recording and reproducing devices use a so-called optical stylus to trace recorded information using light instead of a mechanical record stylus, but even in this case, if there is a large scratch on the recording medium, the disk. , the light spot flies into the truck beside you. In accordance with conventional practice, this phenomenon is also called needle skipping in optical recording and reproducing devices.

FIG. 1 shows the configuration of an example of an optical system of a conventionally used optical recording/reproducing apparatus. In FIG. 1, 1 is a laser diode, 2 is a collimator lens, 3 is a diffraction grating, 4 is a beam fritter, 5 is a focus lens, 6 is a disk, and 7 is a disk 6
Upper track, 8 and 9 are photodetector lenses, 10 is a 6-segment photodetector, 11 and 1
2 and 13 are zero-order, +1-order, and -1-order light spots, respectively; 14, 15, and 16 are photodetectors constituting a 6-division photodetector; and 17 is an actuator coil for driving the focus lens 5.

FIG. 2 is a block diagram of a conventional signal processing system used in the optical system of FIG. 1, in which 18 is a tracking error calculation circuit and 19 is a tracking error amplification circuit.

In Figure 1, the light emitted from a laser diode 1 is made into parallel light beams by a collimator lens 2, and then split into multiple beams by a diffraction grating 3 such as zero-order, ±1st-order, ±2nd-order, etc. . Of these beams, three light beams, zero-order light and ±first-order light, are actually used. The zero-order light and the ±1st-order light pass through a beam splitter 4 and are focused onto a disk 6 by a focus lens 5. Zero-order light is light spot 1
1, the +1st order light and the -1st order light are focused onto the disk 6 as optical spots 12 and 13, respectively.
The light reflected from the disk 6 passes through the beam splitter 4 again and is focused onto a 6-split photodetector 10 by photodetector lenses 8 and 9. The zero-order light is focused on a four-division photodetector 14, and the +1st-order light and -1st-order light are focused on photodetectors 15 and 16, respectively.

The focus error signal is obtained from the output of the four-part photodetector 14 by a well-known method called the astigma focus method. Further, the information signal recorded on the disk is also extracted from the output of the four-division photodetector 14. Therefore, tracking control is performed by moving the focus lens 5 left and right on the disk 6 so that the light spot 11 is positioned above the track 7. The focus lens 5 is moved by an electrodynamic actuator coil 17.

If the light spot 11 were to shift to the right in FIG.
are arranged on a line inclined to the track 7. Therefore, in this case, the amount of light reflected from the light spot 12 increases, and conversely, the amount of light reflected from the light spot 13 decreases. This amount of change is detected by photodetectors 15 and 16. As shown in Figure 2,
The difference between the outputs C and D of the photodetectors 15 and 16 is calculated by the error calculation circuit 18, amplified by the error amplification circuit 19, and the output of the error amplification circuit 19 drives the actuator coil 17. The focus lens 5 is moved so that the output of the lens 18 becomes zero.

Normally, it is sufficient to extract the tracking error signal as described above and apply tracking control, but if there is a large scratch 21 on the track 7 as shown in FIG.
Since the time it takes for the signal to pass through the scratch 22 is different, the output signal (tracking error signal) of the tracking error calculation circuit 18 becomes a positive pulse 31 and a negative pulse 32 as shown in FIG. Therefore, a large error signal current flows through the actuator coil 17, causing the focus lens 5 to swing significantly, and after passing through the scratch 21, the light spot may fly onto other tracks. In other words, needle skipping occurs.

To prevent such needle skipping, it is necessary to detect flaws early and interpolate the areas where the flaws occur. Conventionally, flaw detection has been determined based on whether the output signal of the error calculation circuit 18 exceeds a certain threshold value. However, since the output signal of the error calculation circuit 18 includes the tracking error signal itself and is constantly changing, there is a problem in that the threshold value must be changed depending on the degree of eccentricity of the disk itself.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an optical recording and reproducing device that solves the above-mentioned conventional problems, reliably detects scratches with a simple configuration, and prevents needle skipping.

Structure of the Invention The present invention includes a light source, a light separation means for separating light emitted from the light source into at least two or more light beams, and a light focusing means for focusing the separated light beams onto a recording medium. a photodetector for receiving reflected light or transmitted light from the recording medium to obtain recorded information and a control signal; a control signal holding means for holding a differential value of an output signal of the photodetector; and the control signal holding means. control signal integrating means for integrating the output of the means; and light spot position control means for receiving the output signal of the control signal integrating means and controlling the light focusing means to focus light on a predetermined information position on the recording medium. and a sum signal extracting means for obtaining the sum of output signals of at least two or more elements of the photodetector, and a flaw detecting means for determining flaws on the recording medium from the output signal of the sum signal extracting means. , the control signal holding means is configured to be turned on or off depending on the level of the output of the flaw detection means.

Note that a laser diode or a light emitting diode can be used as the light source. A diffraction grating or the like may be used as the light separation means. A photodiode, a phototransistor, etc. can be used as the photodetector. The light spot position control means may include a two-dimensional electrodynamic actuator that drives the light spot focusing lens two-dimensionally. An ordinary adder can be used as the sum signal extraction means. The flaw detection means detects whether the level of the input signal exceeds a certain value, and may use a normal comparator.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 5 is a block diagram of one embodiment of the present invention. In FIG. 5, 41 and 47 are focus error calculation circuits and tracking error calculation circuits, 42 and 48 are differentiation circuits, 43 and 49 are hold circuits, 44 and 50 are integration circuits, and 45 and 51 are focus error amplification circuits, respectively. , a tracking error amplification circuit; 46 and 52 are respectively a focus actuator and a tracking actuator;
3 is a sum signal calculation circuit for calculating the sum signal of the output signals C and D of the photodetectors 15 and 16 in FIG. 1, and 54 is a flaw detection circuit when the output signal level of the sum signal calculation circuit 53 exceeds a certain level. This is a level determination circuit that outputs a signal to operate the hold circuits 43 and 49. Focus error calculation circuit 4
1 inputs the output signals A and B of the four-division photodetector 14 shown in FIG.
The focus error signal outputted from 1 passes through a differentiation circuit 42, a hold circuit 43, and an integration circuit 44, and is amplified by a focus error amplifier 45 to drive a focus actuator 46. The tracking error calculation circuit 47 inputs the output signals of the photodetectors 15 and 16 shown in FIG.
After passing through the integration circuit 50, the signal is amplified by the tracking error amplification circuit 51 and drives the tracking actuator 52.

On the other hand, the output signal of the sum signal calculation circuit 53 is
As is clear from the figure, as the output of one phototransistor increases, the output of the other phototransistor decreases, so the signal has a substantially constant magnitude. However, if there is a scratch, the output signal of the sum signal calculation circuit 53 will increase, so it is easy to monitor the output signal of the sum signal calculation circuit 53 and determine that there is a scratch if a signal above a certain level appears. The output of the sum signal calculation circuit 53 is connected to a level determination circuit 54, and the output of the level determination circuit 54 is connected to the control input terminals of the hold circuits 43 and 49, respectively. The level determination circuit 54 can be constructed from a normal comparator.

If there is a scratch, the level determination circuit 54 outputs a scratch detection signal, and this scratch detection signal is sent to the hold circuit 43,
49 is operated to hold the differential signal of the focus and tracking error signal at the moment when the flaw is discovered, that is, the signal indicating velocity information. This velocity information is converted into position information by integrating circuits 44 and 50, respectively, and actuators 46 and 50, respectively, convert it into position information.
52 to hold the focus lens 5 in FIG. 1 at a fixed position. FIG. 6 is a waveform diagram for explaining the above operation. Addition circuit 41 in FIG.
Integrating circuit 44, adding circuit 47, integrating circuit 50
Assuming that the output is a sine wave as shown in Figure 6a, in the flawed section shown in Figure 6
It is sufficient if the output signal can be interpolated as shown by the broken line 61. However, if this signal is simply held during the scratch period, the result will be as shown in 62 in a of the same figure. FIG. 6b is a waveform diagram of the output signals of the differentiating circuits 42 and 48 corresponding to the signal in FIG. 6a, and the hold circuits 43 and 49 hold the waveform as shown in waveform 63 in FIG. When this signal is integrated by the integrating circuits 44 and 50, a waveform 64 shown in FIG. 6c is obtained. This waveform is extremely similar to the waveform output when there is no flaw, that is, the waveform 65 in FIG. 6c, and can be used practically as an interpolation signal. In this way, by fixing the light spot position using another interpolation signal while a scratch exists, the needle skipping phenomenon can be prevented.

Effects of the Invention As described above, according to the present invention, scratches on a recording medium can be reliably detected with a simple configuration, and needle skipping can be reliably prevented, so its practical value is extremely high. There is something.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of an optical system of a conventional optical recording/reproducing device, Fig. 2 is a block diagram of a conventional control signal processing system used in the device of Fig. 4 is a waveform diagram showing the influence of the scratches in FIG. 3, FIG. 5 is a block diagram of an embodiment of the present invention, and FIG. 6 is an explanation of the operation of the hold circuit used in this embodiment. FIG. 1... Laser diode, 2, 5, 8, 9...
Lens, 3... Diffraction grating, 4... Beam splitter, 10... Photo detector, 41... Focus error calculation circuit, 47... Tracking error calculation circuit, 42, 48... Differentiation circuit, 43, 49...
...Hold circuit, 44, 50...Integrator circuit, 4
6, 52... Actuator, 53... Sum signal calculation circuit, 54... Level determination circuit.

Claims (1)

[Claims] 1 light source and at least 2 light sources emitted from the light source.
a light separating means for separating into more than one light beam; a light focusing means for focusing the separated light beam onto a recording medium; a control signal holding means for holding the differential value of the output signal of the photodetector, a control signal integrating means for integrating the output of the control signal holding means, and an output of the control signal integrating means. a light spot position control means for receiving a signal and controlling the light focusing means to focus light on a predetermined information position on the recording medium; and a sum of output signals from at least two or more elements of the photodetector. and a flaw detection means for determining flaws on the recording medium from the output signal of the sum signal extracting means, the control signal holding means is turned on or off depending on the level of the output of the flaw detection means. An optical recording/reproducing device characterized by controlling.