JPH04263122A - Optical disk mirror surface defect detection device - Google Patents

Abstract

PURPOSE:To enable a defective portion to be detected accurately by retaining an RF signal at the time of recording which is specified by a sampling pulse with a sample/hold circuit and performing detection of a defect based on the retained RF signal. CONSTITUTION:An optical disk mirror-surface detection device generates a sampling pulse at a recording pause level of a recording signal by a sampling pulse generation circuit 1 based on a recording signal controlling recording operation, retains the RF signal at the time of recording which is specified by this sampling pulse with a sample/hold circuit 2, and then performs detection of a defect based on the retained RF signal. In this case, an unstable large- amplitude RF signal which is input at the time of recording operation cannot be included and a defective portion at the mirror-surface region of the optical disk can be detected properly even at the time of recording with a same circuit configuration as in the case of reproduction.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to R-CD (Record).
The present invention relates to an optical recording/reproducing device using a recordable/reproducible optical disk such as an optical disk (Compact Disk), and particularly to an optical disk specular defect detection device for detecting a specular defect in an optical disk.

0002

[Prior Art] Generally popular CD (Compac)
R-CD is known as an optical disc on which information can be recorded by the user, in addition to the R-CD. To record information on the recording surface of an R-CD, pits with a length corresponding to recording data are formed in grooves formed on the recording surface. The pits are formed by irradiating the groove with a laser beam from a laser diode as a light emitting source and thermally melting the groove. Even when recording information in this way, it is necessary to form pits at appropriate groove positions on the recording surface of the R-CD by performing tracking error detection in the same way as when reproducing information.

Conventionally, there have been devices shown in FIGS. 6 and 7 as mirror surface defect detection devices of this type. FIG. 6 is a block diagram of the conventional device, and FIG. 7 is a timing chart of the defect detection operation of the conventional device. In each of the above figures, the conventional specular defect detection device includes an inverting amplifier 4 that inverts the RF signal output from the optical pickup 100, amplifies it at a predetermined amplification factor, and outputs the inverted RF signal; a first bottom hold 5 that attenuates the signal response exponentially to a small value with a time constant and outputs a short time constant signal; a differentiating circuit 9 that differentiates the short time constant signal; a second bottom hold 6 that outputs a long time constant signal by exponentially greatly attenuating the signal response; a DC shift section 7 that increases the long time constant signal by a certain voltage; and a long time constant whose potential has been increased. The configuration includes a comparator 8 that compares the signal and the differential signal of the short time constant signal and outputs a defect signal.

Next, the operation of the conventional device based on the above configuration will be explained. First, regarding the reproduction operation of reading information stored in the R-CD 10, a laser beam is irradiated onto the R-CD 10 from a semiconductor laser (not shown), and is reflected and diffracted by the lands and grooves of the R-CD 10. The signal light is transmitted through an optical system 11 to a two-split photodiode 1.
2, and the electrical signal photoelectrically converted by the two-split photodiode 12 is outputted from the optical pickup 100 as an RF signal via the operational amplifier 13. This RF signal is a high frequency component signal with a predetermined amplitude, as shown in FIG. 7(A). Portions a1 and a2 of these high frequency components that are not output
corresponds to a defective portion where the reflected signal light cannot be detected in the mirror area of the R-CD 10. In addition, R in the same figure (A)
A portion a3 in the F signal is generated by crossing three lands when a seek operation is performed in the radial direction of the R-CD 10.

[0005] This RF signal is input to an inverting amplifier 4,
This inverting amplifier 4 outputs an inverted RF signal as shown in FIG. 7(B). The inverted RF signal is input to each of the first and second bottom holds 5 and 6, and after the first bottom hold 5 attenuates the inverted RF signal exponentially to a small value with a short time constant, the differentiating circuit 9 By differentiating it by Generate a long time constant signal. This long time constant signal is bottomed up by adding a predetermined DC value α to the short time constant signal by the DC shift section 7. This bottom-up long time constant signal and the short time constant are compared by a comparator 8, and the comparison result is output as a defect signal shown in FIG. 7(E).

By detecting a defective portion in the mirror area of the R-CD 10 in this manner, processing for the defect in the mirror area is performed so that the tracking control signal and focus control signal at this defective area are not affected.

[0007]

[Problem to be Solved by the Invention] Since the conventional optical disk mirror surface defect detection device was constructed as described above,
If the circuit used to detect mirror surface defects based on a uniform RF signal during playback operation is applied directly to recording operation, defects on the mirror surface will be detected during recording operation in which the power supplied for recording has an extremely large amplitude. The problem was that it could not be detected. That is, when the recording output in the recording operation is powered on (when the recording signal is at "H" level), a large amplitude RF signal is included in the electrical signal based on the signal light reflected and diffracted by the lands and grooves of the R-CD 10. It will be included. This large-amplitude RF signal is unstable due to variations in reflection recording characteristics, etc., and because the amplitude is extremely large compared to that during playback, the dynamic range of the circuit is insufficient and the circuit will not operate normally. The problem was that it could not be detected accurately.

The present invention has been made to solve the above-mentioned problems, and is an optical disk specular surface defect that can detect defects in the specular portion of an optical disk during both recording and reproducing operations with the same circuit configuration. The purpose is to propose a detection device.

[0009]

Means for Solving the Problems The optical disk specular defect detection device according to claim 1 is an optical disk that optically records information based on the control of a recording signal and optically reproduces the recorded information. R output by reading defects in the mirror area from the optical disc
In an optical disk mirror surface defect detection device that detects based on an F signal, a sampling pulse generation circuit 1 detects a recording pause level at which pits are not formed on the optical disk in the recording signal and outputs a sampling pulse;
Based on a sample hold circuit 2 that holds the RF signal level based on the sampling pulse, and a reproduction/record selection signal that selects the recording operation and the reproduction operation,
A signal switching circuit 3 is provided, which outputs an RF signal at the signal level held by the sample hold circuit 2 during a recording operation, and switches and outputs the RF signal during a reproduction operation, so that the signal output from the signal switching circuit is This detects specular area defects on optical discs based on RF signals.

In the optical disk specular defect detection device according to the second aspect of the invention, information is optically recorded based on the control of a recording signal, and the recorded information is optically reproduced. In the optical disk mirror surface defect device that detects based on an RF signal output by reading from the optical disk, a sampling pulse generation circuit generates a sampling pulse during a recording pause level period in which pits are not formed on the optical disk in the recording signal; , a sample and hold circuit that passes the RF signal during the generation period of the sampling pulse and holds the previous RF signal level in response to the timing of the generation of a trading edge.

[0011]

[Operation] In the invention according to claim 1, in the stage before detecting defects in the specular area of the optical disk based on the RF signal, the recording stop level of the recording signal is set in the sampling pulse generation circuit based on the recording signal that controls the recording operation. By generating a sampling pulse in the recording operation, holding the RF signal during recording specified by this sampling pulse in a sample hold circuit, and performing defect detection based on this held RF signal, the unstable input during the recording operation can be detected. RF signals with large amplitudes are no longer included, and defective portions in the mirror area of the optical disc can be accurately detected during recording using the same circuit configuration as during playback.

In the invention as set forth in claim 2, the sampling pulse generation circuit generates the sampling pulse during the recording pause period when no pits are formed on the optical disc. The sample and hold circuit conducts the RF signal during the generation period of the sampling pulse, and holds the immediately preceding RF signal at the timing of the trading edge of the sampling pulse.

In this way, during the period when pits are formed on the optical disk, large-amplitude RF signals are no longer included, and the same circuit configuration as during reproduction is used to detect defective areas in the mirrored area of the optical disk. to be detected.

[0014]

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a block diagram of the apparatus of this embodiment, and FIG. 2 is an operation timing chart of the main parts of this embodiment. In each of the figures, the optical disc specular defect detection device according to the present embodiment includes an inverting amplifier 4, first and second bottom holds 5, 6,
The inverting amplifier 4 and the optical pickup 10 in this configuration include a differentiating circuit 9, a CD shift section 7, and a comparator 8.
0, a sampling pulse generation circuit 1, a sample hold circuit 2, and a signal switching circuit 3 are connected between the sampling pulse generation circuit 1, the sample hold circuit 2, and the signal switching circuit 3.

The sampling pulse generating circuit 1 controls the formation of pits in the grooves of the R-CD 10 during the recording operation, and generates a control signal that turns on when a pit is formed and turns off in a specular area where no pits are formed. The configuration is such that a sampling pulse is generated in the OFF state of this control signal. The sample and hold circuit 2 is configured to receive an RF signal from the optical pickup 100 during a recording operation and hold this RF signal in accordance with the timing of generation of the sampling pulse. The signal switching circuit 3 switches between the RF signal directly output from the optical pick-up 100 and the RF signal held in the sample hold circuit 2 based on a reproduction/recording selection signal that controls selection between reproduction operation and recording operation. The configuration is such that the selected signal is switched and outputted to the inverting amplifier 4.

Next, the operation of the apparatus of this embodiment based on the above configuration will be explained separately into (1) reproducing operation and (2) recording operation. (1) Reproduction operation First, in the case of reproduction operation, the signal switching circuit 3 switches to the terminal A based on the reproduction command specified by the reproduction/recording selection signal.
Switch to the playback terminal side. By this switching, the RF signal from the optical pickup 100 is directly input to the inverting amplifier 4 via the signal switching circuit 3. After the RF signal is input to the inverting amplifier 4, a defective portion in the mirror area of the R-CD 10 can be detected by the same operation as the conventional device.

(2) Recording operation Furthermore, in the case of a recording operation, the signal switching circuit 3 switches the terminal B to the recording terminal side based on a recording command specified by the reproduction/recording selection signal. Further, a recording signal for controlling the recording operation (see (A) in FIG. 2) is input to the sampling pulse generation circuit 1, and the output signal of the recording signal is inputted to the sampling pulse generation circuit 1.
A sampling pulse is generated in the FF state as shown in FIG. 2(B). The optical pickup 100 based on the recording signal
A recording laser beam is irradiated onto the R-CD 10 from the R-CD 10, and this recording laser beam is reflected and diffracted by the lands and grooves of the R-CD 10, and is received by the optical pickup 100 as signal light. This optical pickup 100 photoelectrically converts the signal light, and converts the converted large-amplitude RF signal (FIG. 2(C)
) is output to the sampling hold circuit 2. Note that the large-amplitude RF signal corresponds to the recording laser beam output based on the recording signal, and therefore matches the pit string formed by the recording laser beam (see FIG. 2(D)).

The sample and hold circuit 2 holds a level corresponding to a reproduction power of about 0.4 mV out of the input large amplitude RF signal based on the sampling pulse. This held RF signal is output to the inverting amplifier 4 via the terminal B of the signal switching circuit 3. This inverting amplifier 4
The RF signal output to is about 0.4 even during recording operation.
Since it is held and output at a level equivalent to mV reproduction power, a large-amplitude RF signal based on the recording output is not included. Therefore, the defective portion in the mirror area of the R-CD 10 can be reliably detected based on the result detection operation of the inverting amplifier 4 and subsequent parts based on the RF signal at a level equivalent to the reproduction power, which does not include any unstable factors.

Next, an embodiment of the second aspect of the present invention will be described. FIG. 3 is a block diagram of the configuration of an embodiment of the second invention of the present invention. In the figure, a sampling pulse generation circuit 1 generates a pulse having a length corresponding to the length of the recording signal OFF period. FIG. 4 shows the configuration of an embodiment of the sampling pulse generation circuit 1, in which a recording signal is inverted by an inverter 11, and the inverted signal is charged with a time constant determined by a resistor R and a capacitor C. supplied to The output of the time constant circuit and the output signal of the inverter 11 are supplied to an AND gate 10. In addition, a diode D is connected in parallel to both ends of the resistor R, and the input is high.
When the voltage changes from low to low, the stored charge in the capacitor C is instantly discharged.

FIG. 5 is a timing chart showing the operation of the circuit of FIG. The recording signal a is inverted by the inverter 11 to become an inverted recording signal. When this inverted recording signal b is supplied to the resistor R, electricity is stored in the capacitor with an appropriate time constant from the time when the pulse rises to H, resulting in a waveform like the integral signal c. AND gate 10 is
When the waveform of the integral signal c exceeds a predetermined threshold level and enters the H state, a sampling pulse d as shown in the figure is outputted.

That is, the waveform of the sampling pulse d becomes a pulse that rises after a slight delay when the recording pause period in the recording signal begins, and falls as the recording period begins. The sample hold circuit 2 is configured to output the input RF signal as it is during the H period of the sampling pulse, and hold the immediately preceding RF signal during the L period of the sampling pulse. It consists of a capacitor C and a so-called pre-hold circuit that turns on and off the signal at the input terminal of the capacitor C.

Therefore, during the recording operation, the sample and hold circuit 2 outputs an RF signal during the recording pause period in which pits are not formed. On the other hand, during the reproduction operation, it is equivalent to a continuous recording pause period, so the sampling pulse d is always in the H state, and the sample and hold circuit 2 outputs the RF signal as it is.

In FIG. 3, the recording/reproduction selection signal is supplied to the sampling pulse generation circuit 1, but this means that when the reproduction operation is selected, the sampling pulse d is forcibly set to the H state. In order to do this, the sampling pulse d and the recording/reproduction selection signal are logically summed by an OR gate (not shown), thereby preventing malfunction of the apparatus.

Furthermore, the configuration of the sampling pulse generation circuit 1 is not limited to the configuration shown in FIG. 4, but the point is that the sampling pulse is formed so that the H period continues as long as possible during the L level period of the recording signal waveform. That's fine. In the above embodiment, the defect detection section after the signal switching circuit is configured to be performed by an inverting amplifier, first and second bottom holds, a DC shift section, and a comparator. It is also possible to use other defect detection portions as long as they detect defective portions in the specular area of the optical disc.

[0025]

As described above, in the invention as set forth in claim 1, sampling pulses are generated based on a recording signal for controlling a recording operation at a stage before detecting a defect in a mirror area of an optical disk based on an RF signal. A circuit generates a sampling pulse at a recording stop level of a recording signal, and a sample hold circuit holds an RF signal during recording specified by the sampling pulse,
By performing defect detection based on this retained RF signal, unstable large amplitude RF input during recording operation can be detected.
Since no signal is included, it is possible to accurately detect defective portions in the mirror area of the optical disk even during recording using the same circuit configuration as during playback.

According to the second aspect of the invention, the sampling pulse generation circuit generates the sampling pulse during the recording pause period, and the RF signal is made conductive during the sampling pulse generation period to correspond to the trading edge. Since a sample and hold circuit is provided to hold the previous RF signal, there is no need for a special switch or the like, and the device can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram for explaining one embodiment of the present invention.

FIG. 2 is an operational timing chart of main parts of the embodiment shown in FIG. 1;

FIG. 3 is a block configuration diagram for explaining another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a specific example of the sampling pulse generation circuit in the embodiment shown in FIG. 3;

FIG. 5 is a main part operation timing chart of the embodiment shown in FIG. 3;

FIG. 6 is a block diagram of a conventional optical disc mirror surface defect detection device.

FIG. 7 is a block diagram of a conventional optical disc mirror surface defect detection device.

[Explanation of symbols]

1...Sampling pulse generation circuit 2...Sample hold circuit 3...Signal switching circuit 3 4...Inverting amplifier 5...First bottom hold 6...Second bottom hold 7...DC shift section 8...Comparator 9... Differential circuit 10...R-CD 100...Optical pickup

Claims (2)

[Claims] 1. An RF signal output by reading a defect in a specular area of an optical disc on which information is optically recorded based on control of a recording signal and optically reproducing the recorded information from the optical disc. An optical disk specular surface defect detection device that detects based on a sampling pulse generation circuit that detects a recording pause level period in which pits are not formed on the optical disk in the recording signal and outputs a sampling pulse; a sample hold circuit that responsively holds the RF signal level until the next sampling pulse generation timing; and a sample hold circuit that responds to the recording operation based on a reproduction/record selection signal that selects between the recording operation and the reproduction operation. In addition to outputting the RF signal at the maintained signal level, the R
An optical disc specular defect detection device comprising: a signal switching circuit that switches and outputs an F signal, and detects a specular area defect of an optical disc based on an RF signal output from the signal switching circuit. 2. An RF signal output by reading a defect in a specular area of an optical disc on which information is optically recorded based on control of a recording signal and optically reproducing the recorded information from the optical disc. In the optical disk specular surface defect detection device, the sampling pulse generation circuit generates a sampling pulse during a recording pause level period in which pits are not formed on the optical disk in the recording signal, and the RF during the generation period of the sampling pulse. The signal is passed through, and in response to the timing of the trading edge, the previous RF
What is claimed is: 1. An optical disc specular surface defect detection device comprising: a sample hold circuit for holding a signal level.