JPH02192049A - Information reproducing circuit of rewritable optical disk device - Google Patents

Abstract

PURPOSE:To correctly detect an erasing omitted part by providing a detection level switching means, which switches the detection level at the time of checking erasing omission after erasing by means of a signal level checking circuit so as to be lower than the checking level at the time of normal reproducing. CONSTITUTION:A detection level switching means 133, which switches the detec tion level of a signal level checking circuit 107 to check the presence/absence of a reproducing signal between at the time of normal reproducing and at the time of checking the erasing omission after erasing, is provided. By the switching, the detection level at the time of checking the erasing omission after erasing is set lower than the detection level at the time of normal reproduc ing. Thus since the detection level to check the regenerative signal due to the erasing omission after erasing is set at the lower value than the detection level to check the regenerative signal at the time of normal reproducing, even when the characteristics of the recording medium and a reproducing device have dispersion or fluctuation, the presence/absence of the normal regenerative signal can be correctly detected, and the presence/absence of the erasing omission can be surely and correctly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disk device (so-called information reproducing circuit) capable of recording and erasing data, such as a magneto-optical disk device.

[Prior Art] Generally, in a magneto-optical disk device, as shown in the plan view of an optical disk in FIG. Information is recorded depending on the direction of magnetization 3 of the film (upward or downward). To reproduce information signals from the optical disc 1, as shown in the diagram of the reproduction operation principle in FIG. 6, a laser beam 4 is irradiated onto the disc surface on which information is recorded in the form of a domain array, and a rotation angle due to the Kerr effect is detected. This is done by

As shown in the cross-sectional view and plan view of the magneto-optical disk section in FIGS. 6(a) and 6(b), the laser spot 4 has a larger diameter than the domain diameter due to spreading, and the adjacent pits are reproduced. As shown in the waveform diagram of FIG. 6(C), the signals have an overlapping portion.

Furthermore, as shown in the disc format diagram in Figure 7, the information track on an optical disc is divided into multiple areas (called sectors), and each area has a track number, sector number, etc. The part where the information necessary for recording and playback is recorded (usually this part is called the ID
(referred to as ) and a data section in which user data is recorded by additional recording. For example, an example of a method for recording data in sectors of an optical disc is described in Japanese Patent Application Laid-Open No. 181163/1983.

In a rewritable optical disc device, it is important that the data section can be additionally recorded any number of times by performing an erasing operation.

However, in the conventional detection method, the method for detecting unerased data is not sufficient, and erroneous detection of information due to a drop in S/N during re-recording and erroneous detection of information during reproduction occur.

FIG. 8 is a schematic diagram of a conventional information reproducing circuit.

The reproduced signal read from the optical disk by the optical head 10 is amplified by the preamplifier 11 and then sent to the AGC amplifier 1.
2 to a predetermined amplitude, and the differential circuit 13 and the DC regeneration circuit 1
Enter 6. The DC regeneration circuit 16 uses AC at the preamplifier.
This circuit adds a DC component to the combined signal and shapes the waveform into a signal close to the original optical reproduction signal. The DC reproduction signal is input to the amplitude detection circuit 17, which detects whether the signal amplitude is a predetermined amplitude and calculates AαCi! The information is given to the control circuit 18. Therefore, the AGC circuit 18 creates a signal that controls the AGC amplifier 12 so that the signal amplitude becomes a predetermined value. The output signal of the AGC amplifier 12 is passed through a differentiating circuit 13, a zero cross detection circuit 14, a signal amplitude detection circuit (signal level inspection circuit) 15, and a read data generation logic circuit 19 to obtain a read data signal.

Figure 3 shows the principle of reproducing recorded data before erasing.
Figure 4 shows the principle of reproducing recorded data after erasing, (a)
is an optical reproduction signal, (b) is a signal obtained by differentiating (a), (c)
is the signal obtained by zero-crossing the signal in (b) and digitizing it,
(d) is a signal sliced and digitized at a certain detection level determined by the signal amplitude detection circuit, (e) is (d)
The signal is pulse-shaped by a one-shot circuit,
(f) is a signal obtained by ORing (c) and (e). Here, in the conventional circuit, as shown in FIG.
When slicing is performed, the read data signal 132 is not generated (132').

It is determined that the operation has completed normally.

[Problems to be Solved by the Invention] The above-mentioned conventional technology has a problem in that the slice level during reproduction and the reproduction signal check after erasing (Read After Erase)
, hereinafter referred to as rRAEJ) are set to the same slice level (detection level), there is insufficient checking for unerased areas, resulting in the following problem.

(1) In the case of RA E, the erasing operation ended normally, but since the reproduced signal was at the very edge of the slice level, the reproduced signal exceeded the slice level due to changes over time or other fluctuations during subsequent reproduction, resulting in information errors. Detected.

(2) In the case of RA E, the erasing operation ended normally, but since the reproduced signal was at the very edge of the slice level, during subsequent recording, the unerased portion becomes noise and information is erroneously detected due to the S/N or lower.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a highly reliable information reproducing circuit that can solve the above problems and correctly detect unerased portions.

[Means for Solving the Problems] In order to achieve the above object, the information reproducing circuit of the rewritable optical disc device of the present invention checks the presence or absence of a reproduced signal and detects the detection level of the signal level inspection circuit during normal reproduction. A detection level switching means is provided for switching between the detection level and the inspection of the erased residue after erasing. By this switching, the detection level during the inspection of the remaining erased data after erasing is set lower than the detection level during normal reproduction.

[Effect] The operation based on the above configuration will be explained.

In the signal level inspection circuit, the detection level for checking the reproduced signal due to the remaining erased data after erasing is set to a lower value than the detection level for checking the reproduced signal during normal playback. Even if there are variations or fluctuations in characteristics, the presence or absence of a normal reproduction signal can be correctly detected, and the presence or absence of an erased residue can also be detected with sufficient reliability (correctly).

In addition, in the specific configuration of this signal level inspection circuit, the detection level voltage that cuts the magnitude of the reproduced signal during erasing is determined by a resistor divider circuit, so that the voltage at the RAE and Read By changing this ratio over time, read data can be generated even with a smaller signal during RAE compared to during Read, and it is possible to sufficiently check for unerased data. Switching of the detection level can be easily configured by using a driver IC such as an open collector, so malfunctions will not occur. In addition, by providing a sufficient difference between the detection levels during Read and RAE, data will not be erroneously detected due to changes over time or compatibility between devices.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is a block diagram showing the overall configuration of an information reproducing circuit and a sector mark detection circuit according to an embodiment of the present invention, and FIGS. 3 and 4 show waveforms during reproduction and erasure in each part of FIG. 1. It is a diagram. The information recorded on the optical disk is reproduced by the read detector 101 in the optical head to obtain a signal 120 (FIG. 3). The reproduced signal 120 is
The signal is amplified by a preamplifier 102, passes through an ID/DATA signal switching circuit 103, and reaches a differentiating circuit 104.

The differential circuit 104 moves the peak point of the domain of the reproduced signal 120 to the zero point of the differential signal 121 (FIG. 3).

Since the differential signal as it is has large signal amplitude fluctuations due to variations in the optical head, optical disk, etc.
The C amplifier 105, signal amplitude detection circuit 111, and AGC control circuit 110 control the signal to have a constant amplitude. Note that the operation of the signal amplitude detection circuit 111 is similar to that of the signal amplitude circuit 17 in FIG. The output signal of the AGC amplifier 105 is generated by the zero-crossing point detection circuit 106 so that the peak point of the reproduced signal 120 corresponds to the rising edge of the zero-crossing signal pulse. The AGC amplifier output signal is also input to the signal amplitude detection circuit (signal level inspection circuit) 107,
A signal amplitude detection level (reproduction level) is determined by a signal 133 representing the operating state of the optical disk device. The detection level during playback is 122, and the detection level during playback after erasure is 128. Above detection level and differential signal 121.1
29, amplitude detection signals 124, 130, 130' are obtained. Signals 125, 131, and 131' are obtained by a one-shot circuit 139 that extends the pulse width by a certain amount of time from the fall of the signals 124, 130, and 130'. Zero cross signal 123 and signal amplitude detection signals 125, 131, 131'
are input to the AND element 108, and the read data 126.
132,132' is obtained.

The preamplifier output signal is sent via circuits (DC regeneration circuit, A/D conversion circuit, and SM signal detection logic circuit) 113, 114, and 115 that detect the sector mark signal formatted at the beginning of the ID section. and thereby generate a sector mark signal. By supplying the sector mark signal to the timing signal generation circuit 112,
Generates GC control timing and ID/DATA switching timing signals.

FIG. 2 is a detailed configuration diagram of the signal amplitude detection circuit 107 of FIG. 1. As shown in FIG. 1, the signal amplitude detection circuit 107 is connected to a read data generation logic circuit 109, an AGC amplifier 105, and an AND element 108, respectively.

In FIG. 2, 116 is an open collector driver IC 1134, 135, 136, 137 is a resistive element (
R□ to R4), 138 is a comparator.

Further, 133 is a signal that indicates the operating state of the optical disc and switches the detection level, and indicates whether it is in the playback state after erasure (RAE) or not. 139 is a one-shot circuit that generates a pulse that is long for a certain period of time from the trailing edge of the pulse.

The voltages of detection levels 122 and 128, which are signals for generating signal amplitude detection signals 131 and 131', are R□,
R2, R3, and R4, and in this case, during normal playback (Read), the RAEMD-N signal 13
Since 3 is High level, the detection level is R3.
/(R1+R2+R,) is determined, and when RAE is RAEMD
-N signal 133 becomes Low level, so the detection level is R4/ (R2+R3)/R□R4//(R2+R3)
3). As can be seen from the above equation, the detection level during RAE is lower than that during Read. For this reason, conventional circuits do not generate read pulses for waveforms that have not been sufficiently erased, and operate as if sufficient erasure has been performed.
If erasing is not sufficient by the circuit of the present invention, read data is generated, and if the number of pulses exceeds a certain predetermined number, the erasing operation is performed again or the sector is registered as a non-erasable sector. Avoid using it. As described above, according to this embodiment, it is possible to perform a sufficient reproduction check after erasing, and data quality can be fully guaranteed during erasing.

[Effects of the Invention] As described in detail above, according to the information reproducing circuit of the rewritable optical disc device of the present invention, the detection level during the erased residual inspection after erasure is lower than the detection level during normal playback. Therefore, it is possible to sufficiently detect the remaining erased portions without omitting them, and the data quality for the remaining erased portions can be sufficiently guaranteed, and the reliability of reproduced data can be improved. Further, even if there are variations in performance of recording/reproducing devices and optical disk recording media, good recording/reproducing can be performed, so that it is possible to ensure data compatibility. Further, the circuit configuration can achieve effects that can be achieved by simply adding a simple detection level switching circuit to a conventional circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an information reproducing circuit and a sector mark detection circuit to which an embodiment of the present invention is applied, FIG. 2 is a detailed configuration diagram of a signal amplitude detection circuit and a zero-crossing point detection circuit, and FIG. Figure 3 is a waveform diagram showing the principle of reproduction of recorded data, Figure 4 is a waveform diagram of the principle of reproduction of erased data, and Figure 5 is an optical disc for explaining the principle of reproduction of general optical disc. FIG. 6 is an explanatory diagram of the principle of reproducing operation of a general optical disc, FIG. 7 is a diagram showing the format on the optical disc, and FIG. 8 is a block diagram of a conventional information reproducing circuit. 1... optical disc, 2... track,
3...domain, 4...laser beam,
10,101... Optical head, 11,102...
... Preamplifier, 103 ... ID/DATA signal switching circuit, 12, 105 ... AGC amplifier, 1
3,104... Differential circuit, 14.106...
・・Zero cross point detection circuit, 15°107・・・・・・
Signal amplitude detection circuit (signal level inspection circuit), 16, 11
3...DC regeneration circuit, 17...DC reproduction signal amplitude detection circuit, 18,110...AGC control circuit, 19,109...Read data generation logic Circuit, 112... Timing signal generation circuit, 1
14...A/D conversion circuit, 115...
SM signal detection logic circuit, 116...Open collector driver IC1108...AND circuit, 120...Reproduction signal of recorded data, 121.
... Signal obtained by differentiating signal 120, 122 ... Detection level during playback, 123 ... Zero cross signal,
124... Amplitude detection signal, 125...
A signal obtained by delaying the trailing edge of signal 124, 126...
Read data signal, 127... Insufficient reproduction signal after erasure, 128... Detection level during reproduction after erasure, 129... Signal obtained by differentiating signal 127, 1
30, 130'... Digitized signal of signal 129, 131, 131'... Signal 130°131
132, 132'...Read data signal, 133...Reproduction mode signal, 1
34-137... Resistance element, 138...
・Comparator, 139...One-shot circuit. Diagram (N-at birth) Diagram (at Urago)

Claims (1)

[Claims] 1. In an information reproducing circuit of a rewritable optical disk device having a signal level testing circuit that determines the presence or absence of a reproduced signal by checking whether the level of the reproduced signal exceeds a predetermined value, the signal level testing circuit: 1. An information reproducing circuit for a rewritable optical disk device, comprising a detection level switching means for switching a detection level during inspection of erased residue after erasing to be lower than a detection level during normal reproduction.