JPH0234093B2 - - 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-based 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 that traces recorded information using light instead of a mechanical record stylus. In this case as well, if there is a large scratch on the disk, which is the recording medium, the light spot will fly to the side tracks. In accordance with conventional practice, this phenomenon is also called needle skipping in optical recording and reproducing devices.

FIG. 1a shows the basic configuration of an example of a conventional general optical recording/reproducing device. In the same figure, 1 is a laser diode, 2 is a collimator lens, and 3 is a laser diode.
is a beam splitter, 4 is a focus lens, 5 is a
1 is a disk (FIG. 1b shows a sectional view of the disk 5), 6 is a photodetector lens, 7 is a light shielding plate, and 8 is a four-part photodetector. Also,
A tracking actuator 9 moves the focus lens 4 parallel to the disk 5, and a focus actuator 10 moves the focus lens 4 perpendicular to the disk 5.

In FIG. 1, light emitted from a laser diode 1 is collimated by a collimator lens 2, passes through a beam splitter 3, and is focused onto a disk 5 by a focus lens 4. The reflected light from the disk 5 passes through the focus lens 4 and the beam splitter 3 again, and is focused by the photodetector lens 6 onto the 4-split photodetector 8. Half of the light exiting the photodetector lens 6 is blocked by a light shielding plate 7. When the disk 5 moves up and down and the focus shifts, the light spot on the 4-split photo detector 8 moves up and down, and the amount of light hitting (A+B) on the 4-segment photo detector 8 and (D+
C) The amount of light falling on the area changes. Also, disk 5
When the upper track 11 shifts, the reflected diffraction light distribution 1
A difference in light amount occurs between 2 and 13. Since the photodetector lens 6 is a cylindrical lens, the amount of light hitting (A+D) and the amount of light hitting (B+C) of the four-division photodetector 8 change. In this way, a focus error signal and a tracking error signal are detected.

FIG. 2 shows a signal processing system of the optical recording/reproducing apparatus shown in FIG. In FIG. 2, 21 is a focus error calculation circuit which calculates the difference between the (A+B) output and (C+D) output of the 4-division photodetector 8. A focus error amplification circuit 22 amplifies the output of the focus error calculation circuit 4 to move the focus actuator 10 so that the focus error becomes zero. Similarly, 23 is a tracking error calculation circuit, and 24 is a tracking error amplification circuit.
C) The difference between the outputs is taken, and the output is amplified by the tracking error amplification circuit 24 to move the tracking actuator 9 so that the tracking error becomes zero. Reference numeral 25 denotes an information signal extraction calculation circuit which calculates the sum (A+B+C+D) of each output signal of the photodetector 8, A, B, C, and D, and reproduces the information recorded on the disk 5 from this output.

Conventionally, in this method, if there is a scratch on the disk, the reflected light is greatly disturbed, which is output to the focus error signal and tracking error signal, causing the needle to go out of focus or skip to the side track. happen. Even if only the focus is off, needle skipping is often induced.

In addition, there is no good method for flaw detection in the past, and experimentally, when an abnormally large signal is output from the error calculation circuit 21 or 23 in FIG. It was very difficult to determine the signal level for detection.

Further, FIG. 3 shows an example of a method for preventing needle skipping in a conventional optical recording/reproducing apparatus.

In FIG. 3, the same parts as in FIG. 2 are given the same numbers, and redundant explanation will be omitted. The output signal of the information signal extraction calculation circuit 25 is passed through the low pass filter 3.
3 to cut out high frequency components. Since the information signal is usually a high frequency signal of about 1 MHz, the output signal of the low-pass filter 33 does not contain any information signal component. Further, since no error signal component is included, the output signal of the low-pass filter 33 is normally a signal with very little change. By the information signal extraction calculation circuit 25 and the low-pass filter 33,
It constitutes a sum signal extraction circuit 35 for flaw detection.

If there is a scratch on the disk 5, the total amount of light will fluctuate, so a large pulse will appear in the output of the low-pass filter 33. The output of the low-pass filter is input to a level determination circuit 34, and the level determination circuit 34 determines that there is a flaw when a large pulse of a predetermined level or higher comes, and outputs a flaw detection signal. The output of the level determination circuit 34 is connected to the control inputs of the focusing error hold circuit 31 and the tracking error hold circuit 32, and the immediately preceding error signal is held using the flaw detection signal at the moment a flaw is detected. In this way, the focus error signal or the tracking error signal will not be affected by scratches, and the occurrence of needle skipping will be significantly reduced.

The conventional method shown in FIG. 3 holds the error signal at the moment when needle skipping occurs, but since the disk being controlled is still moving during that time, holding it for a long time will still cause needle skipping. Therefore, the value obtained by differentiating the focus error signal and the tracking error signal once or twice is held, and the value obtained by integrating the hold value once or twice is used to control the focus actuator 10 and tracking. By driving the actuator 9, it is possible to prevent needle skipping even in the case of large scratches.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the conventional problems as described above and to effectively prevent the needle skipping phenomenon in optical recording/reproducing devices.

Structure of the Invention In order to achieve the above object, the present invention includes a light source, a light focusing means for focusing the light emitted from the light source onto a recording medium, and a light source for receiving and recording reflected light or transmitted light from the recording medium. a photodetector for receiving information and control signals; a light spot position control means for controlling the light focusing means to focus light on a predetermined information position on the recording medium; and a predetermined portion of the photodetector. flaw detection means for determining flaws on the recording medium from the output signal of the sum signal extraction means; and means for controlling the position of the light spot based on the output signal of the flaw detection means. The optical recording and reproducing apparatus includes a needle skip prevention control means for controlling the needle skipping and preventing needle skipping from occurring.

In the present invention, focus error detection is performed using (A+
(A+B)+(C+D) instead of B)-(C+D)
This is done by taking the sum signal of This sum signal is (A+B+C+D), which is essentially the same signal as the output signal of the information signal extraction arithmetic circuit 25, but with the high frequency components (approximately 10 KHz or higher) cut off. Therefore, the information signal extraction calculation circuit 2
A signal obtained by cutting out high-frequency components from the output signal of No. 5 may also be used.

The simplest way to prevent needle skipping when a flaw is detected is to hold the focus signal and tracking signal so that the light spot does not waver.

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

FIG. 4 shows a block diagram of an embodiment of the present invention. In FIG. 4, the same parts as in FIG. 3 are given the same numbers, and redundant explanations will be omitted. 41, 42
is a differentiation circuit, and 43 and 44 are integration circuits. The operation of the focus error signal system will be explained. If a flaw is detected, the output signal of the differentiating circuit 41 is held by the focus error hold circuit 31. The output of the differential circuit 41 includes speed or acceleration information indicating whether the disk 5 is moving upward or downward. Therefore, if the focus actuator 10 is driven using this information, better control than that shown in FIG. 3 can be achieved. The integration circuit 43 converts the information into the velocity or acceleration information and drives the focus actuator 10. A similar operation is performed by the differentiating circuit 42 and the integrating circuit 44 in the tracking error signal system.

In the optical system shown in FIG. 1, the output of the total amount of light is used as the flaw detection signal, but various combinations are possible depending on the optical system. That is, any signal can be used as long as it is a sum signal of output signals of predetermined portions between divided photodetectors that does not contain signal components harmful to flaw detection.

A case where the present invention is applied to a well-known three-beam optical system will be explained with reference to FIG.

As shown in FIG. 5, the three-beam optical system focuses three light spots on the track of the disk. In FIG. 5, 51 is a track, 52 is a main light spot, and 53 and 54 are first and second sub-light spots, respectively. In order to read the information written on the track using the main light spot 52, a tracking error signal is extracted using the first and second sub-light spots 53 and 54 so that the main light spot 52 is located on the track in a different manner. , tracking control. 55 indicates a 6-division photodetector. Since the configuration of the optical system is well known, the explanation will be omitted, but the three lights reflected from the disk (not shown) are transmitted to E, F, and G of the 6-segment photodetector 55, respectively, as shown in the figure.
The optical system is configured so that the light is incident on the part. That is, the reflected light from the main light spot 52 is directed to the E portion.
The reflected light from the first sub-light spot enters the lower part, and the reflected light from the second sub-light spot enters the G part. The tracking error signal is obtained from the difference between the F and G output signals. However, it is clear that if the output signal of (F+G) is taken instead, it can be used as a flaw detection signal. Alternatively, the sum of the output signals of the four photodetectors in the E section can be used as the flaw detection signal.

As described above, there are various methods for extracting flaw detection signals depending on the type of optical system and photodetector used, but it goes without saying that the essence of the present invention does not change depending on the difference.

Furthermore, although the above embodiments have been described only in the case of reproduction, the present invention can also be used in the case of optical recording since focus control and tracking control are performed in the same way in the case of optical recording. Needless to say.

Effects of the Invention As described above, according to the present invention, scratches on a disk can be detected reliably and quickly, and the needle skipping phenomenon can be reliably prevented, so that the present invention has extremely great practical value.

[Brief explanation of drawings]

Figures 1a and 1b are block diagrams and cross-sectional views of the main parts of the optical system of a conventional general optical recording/reproducing device, and Figure 2 is a block diagram of a conventional signal processing system used in the device shown in Figure 1. , FIG. 3 is a block diagram illustrating a conventional needle skip prevention method, FIG. 4 is a block diagram of main parts of an embodiment of the present invention, and FIG. 5 is a principle diagram of another optical system in which the present invention can be used. It is. 1... Laser diode, 2, 4, 6... Lens, 3... Beam splitter, 7... Light shielding plate,
8... Photo detector, 21... Focus error calculation circuit, 22... Tracking error calculation circuit, 34... Level judgment circuit, 35... Sum signal extraction circuit, 41, 42... Differentiation circuit, 43, 44...
...integrator circuit.

Claims (1)

[Claims] 1. A light source, a light focusing means for focusing the light emitted from the light source onto a recording medium, and a light detection unit for receiving reflected light or transmitted light from the recording medium to obtain recorded information and a position error signal of a light spot. an error detection means for extracting the position error signal from the output of the photodetector, a control signal holding means for differentiating the output signal of the error detection means at least once and holding the differential value, and the control signal. control signal integrating means for integrating the output of the holding means at least once; and a light receiving the output signal of the control signal integrating means to control the light focusing means to focus the light on a predetermined information position on the recording medium. spot position control means; sum signal extraction means for obtaining a sum signal of a predetermined portion of the photodetector; flaw detection means for determining a flaw on a recording medium from an output signal of the sum signal extraction means; An optical recording/reproducing device characterized in that the control signal holding means is controlled by the output signal of the detection means.