JPS5928251A - optical recording and reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording/reproducing device (
(including those that do not have either recording or playback functions).

Page 3 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,
Needle skipping occurs when the record needle jumps to the track next to it. 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 horizontal track. In accordance with conventional practice, this phenomenon is also called needle skipping in optical recording and reproducing devices.

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

In FIG. 1, light emitted from a laser diode 1 is made parallel by a collimator lens 2, passes through a beam splinter 3, and is focused onto a disk 5 by a focus lens 4. The reflected light from the disk 5 is reflected again by the focus lens 4. The beam passes through a beam splitter 3 and is focused by a photodetector lens 6 onto a four-part photodetector 8''. A light shielding plate 7 shields the minor portion of the light that exits the photodetector lens 6. When the disk 6 moves downwards and the focus shifts, the light spot on the 4-split photodetector 8 moves up and down, and the light spot on the 4-split photodetector 8 (
The amount of light that hits A+B) and the amount of light that hits (D+C) change. Furthermore, if the trunk 11 on the disk 5 is shifted, a difference in light amount will occur in the reflected and diffracted light distributions 12 and 13. Since the photodetector lens 6 is a cylindrical lens, the amount of light hitting (A+D) of the 4-split photodetector 8 and (B
10)6 The amount of light hitting the page changes. 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-split photodetector 8.

A focus error amplification circuit 22 amplifies the output of the focus error calculation circuit 4 to move the focus actuator 1o so that the focus error becomes zero.

Similarly, 23 is a tracking error calculation circuit, and 24 is a tracking error amplification circuit. The circuit 24 amplifies the signal and moves the tracking actuator 9 so that the tracking error becomes zero. 26 is an information signal extraction calculation circuit, and photodetector 8
The sum of each output signal of A, B, C, and D (A + B +
C+D) and reproduce the information recorded on the disc 6 page 6 from this output.

In this conventional method, if there is a scratch on the disc, the reflected light will be greatly disturbed, and this will be output as a focus error signal or tracking error signal, causing the focus to be lost or the light to fly to the side track. Needle skipping occurs. Even if only the focus is lost, 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.

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-mentioned 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 method for detecting reflected light or transmitted light from the recording medium. a photodetector for receiving light and recording information and a control signal; a light spot position control means for controlling the light focusing means to focus the light on a predetermined information position on the recording medium; and the photodetector. sum signal extraction means for obtaining a sum signal of a predetermined portion of the recording medium; flaw detection means for determining flaws on the recording medium from the output signal of the sum signal extraction means; The optical recording and reproducing apparatus includes a needle skip prevention control means for controlling the spot position control means and preventing needle skipping from occurring.

In the present invention, focus error detection is performed as (A+B)-(
This is done by taking the sum signal of (A+B)+(C+D) instead of C+D). This sum signal is (A+
B+C+D), which is essentially the same signal as the output signal of the information signal extraction calculation circuit 26, but with a high frequency component (approximately 10
kHz or higher) is cut. Therefore,
A signal obtained by cutting high frequency components from the output signal of the information signal extraction calculation circuit 25 may be used.

The easiest 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 examples Embodiments of the present invention will be described below based on the drawings.

FIG. 3 shows a block diagram of an embodiment of the present invention.

In FIG. 3, the same parts as in FIG. 2 are given the same numbers, and redundant explanation will be omitted. Information signal extraction calculation circuit 26
The output signal is passed through a low-pass filter 33 to cut high-frequency components. Since the information signal is normally a high frequency signal on the order of I 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. The information signal extraction calculation circuit 25 and the low-pass filter 33 constitute a sum signal extraction circuit 36 for flaw detection.

If there is a scratch on the disk 5, a large pulse will appear at the output of the low-pass filter 33 because a nine-page variation in the total light amount will occur. 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 focus 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 embodiment shown in FIG. 3 holds the error signal at the moment when needle skipping occurs, but since the disk to be 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 for 10 pages is used to control the focus actuator 1° and the tracking actuator. By driving the needle 9, it is possible to prevent the needle from flying even when a large scratch is made.

FIG. 4 shows a block diagram of another embodiment of the present invention based on this idea. In FIG. 4, the same parts as in FIG. 3 are given the same numbers, and redundant explanation will be omitted. 41.42 is a differentiation circuit, and 43.44 is an integration circuit. The operation of the focus error signal system will be explained. If a flaw is detected, the output signal of the differentiator circuit 41 is held by the focus error hold circuit 31. The output signal of the differential circuit 41 includes speed or acceleration information indicating whether the disk 5 is moving upward or downward. Therefore, if the shift focus actuator 1o is driven using this information, better control than that shown in FIG. 3 can be achieved. The integration circuit 43 converts the velocity or acceleration information into position information and drives the focus actuator 1o. Similar operations 11, . . . are performed in the tracking error signal system as well.
and is performed by the integrating circuit 44.

In the optical system shown in Fig. 1, the flaw detection signal is
Although the total light output was used, 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 tracks of the disk. In FIG. 6, 51 is a track, 62 is a main light spot, and 63 and 54 are first and second sub-light spots, respectively. In order to read the information recorded on the track with the main light spot 52, a tracking error signal is extracted with the first and second sub-light spoilers 53 and 54 so that the main light spot 52 is located exactly on the track. and control tracking. 66 indicates a 6-segment photodetector. Although the configuration of the optical system is well known and will not be described here, the three lights reflected from the disk (not shown) are sent to six-segment photodetectors 560E and 560F, respectively, as shown in the figure.

An optical system is configured so that the light enters the G portion.

That is, the main light spot 520 reflected light goes to the E part, and the first
The reflected light from the second 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 is not changed by these differences.

Furthermore, in the explanation of the above embodiment, only the case of playback was described on page 13, but since the focus control and tracking control are performed in the same way in the case of optical recording, the present invention can also be used in the case of optical recording. Needless to say, it can be done.

Effects of the Invention As described above, according to the present invention, it is possible to detect scratches on a disc reliably and quickly, and the stylus skipping phenomenon can be reliably prevented, so that the present invention has extremely great practical value.

[Brief explanation of drawings]

1(a) and 1(b) are a configuration diagram and a sectional view of the main parts of the optical system of a conventional general optical recording/reproducing device, and FIG.
Block diagram of the conventional signal processing system used in the device shown in Figure 3.
The figure is a block diagram of the essential parts of one embodiment of the present invention, FIG. 4 is a block diagram of the essential parts of another embodiment of the present invention, and FIG. 5 is a principle diagram of another optical system in which the present invention can be used. be. 1...e laser diode, 2, 4, 6...
... Lens, 3 ... Beam splinter, 7 skewers
... e light shielding plate, 8 ... photodetector,
21...14 Page focus error calculation circuit, 22. , . . . Tracking error calculation circuit, 31 , 32 , , , Hold circuit, 34 . . . Level judgment circuit, 35 , ,
,,, sum signal extraction circuit, 41.42...differentiation circuit, 43.44...integration circuit. Name of agent: Patent attorney Toshio Nakao, 1st person, 2nd person
Figure 3

Claims (1)

[Scope of Claims] A photodetector for receiving transmitted light to obtain recorded information and a position error signal of a light spot, error detection means for extracting the position error signal from the output of the photodetector, and the error detection means for extracting the position error signal from the output of the photodetector. a light spot position control means for controlling the light focusing means to focus light on a predetermined position on the recording medium according to the output of the detection means; and a sum signal for obtaining a sum signal of a predetermined portion of the photodetector. an extracting means, a flaw detecting means for determining flaws on the recording medium from the output signal of the sum signal extracting means, and controlling the light spot position control means using the output signal of the flaw detecting means to prevent needle skipping. An optical recording/reproducing device comprising a needle skip prevention control means. (2) The needle skip prevention control means is provided between the error detection means and the optical spot position control means, and includes a hold circuit that holds the output of the error detection means when the flaw detection means detects a flaw. An optical recording/reproducing apparatus according to claim (1), characterized in that: (3) Needle jump prevention control is provided between the error detection means and the light spot position control means, and differentiates the output of the error detection means at least once and then integrates it again at least once to detect the output of the light spot position control means. configured to add to
Further, when the flaw detection means detects a flaw, it is configured to hold a value obtained by differentiating the output of the error detection means at least once.
1) The optical recording/reproducing device according to item 1).