JPH0346125A - Recorded part detecting circuit for optical disk player - Google Patents

Abstract

PURPOSE:To exactly discriminate a recorded part and an unrecorded part on a magneto-optical disk by extracting a synchronizing signal from a demodulated video format signal and discriminating the recorded part based on this synchro nizing signal. CONSTITUTION:A reproducing video format signal, which is FM demodulated in a demodulation circuit 8, is supplied to a signal processing circuit 20 and supplied to a synchronizing sampling circuit 31 as a synchronizing signal separating means in a recorded part detecting circuit 30. In the detecting circuit 30, a recorded part detecting signal is generated as long as the synchronizing signal is extracted from the sampling circuit 31. Thus, even in case demodulation processing is executed to noise read from an unerased part, the video format signal can not be obtained and accordingly, the synchronizing signal is not outputted from the sampling circuit 31. Then, the recorded part signal is not outputted. Thus, only when the recorded part is read, the recorded part detecting signal is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an optical disc player, and in particular to an optical disc player for recording and playing back video signals (hereinafter referred to as video format signals) including synchronization signals such as so-called vertical and horizontal synchronization signals. The present invention relates to a recorded portion detection circuit in an optical disc player.

BACKGROUND ART A recording/reproducing method is known in which an FM-modulated video format signal is recorded as a file on an optical disc so that moving images or still images can be reproduced. In such a recording/reproducing method, an address signal is pre-recorded as pre-pits on a disk for file management, and an address signal based on the pre-address bits is detected from an RF multiplied signal read from the disk when recording a video format signal. The rotational speed of the disk is controlled according to the phase difference between this detected address signal and the vertical synchronization signal in the video format signal to be recorded, and recording is performed so that one frame of the video format corresponds to one track. Also,
In order to prevent the bria address bits from adversely affecting the video signal, time axis control is performed so that the bria address bits are located within the corresponding area of the vertical blanking interval.

As described above, in a disc player that records and plays back a video format signal, whether or not image information is recorded on a track is determined when determining whether to output a playback video format signal or when searching for an empty track. It is necessary to judge.

The methods include: (1) Each time a signal is recorded on one track on the disk, the track number of that track is recorded in a predetermined area on the disk and managed.

(2) A method in which an external storage device is provided separately, and each time a signal is recorded on one track on the disk, the track number of that track is recorded and managed in the external storage device.

■Method of directly detecting the presence or absence of recorded video format signals.

is being considered.

The above methods (1) and (2) have the disadvantage that the system configuration becomes complicated.

In addition, in the case of the method (2), for example, as shown in FIG. 52
The disc player is provided with a recorded portion detection circuit comprising a comparator 53 that compares the recorded portion with the reference level vth generated by the above. In the circuit of FIG. 3, when the RF multiplied signal obtained when reading is performed alternately in the unrecorded area and the low recorded area as shown in FIG. 4(A), the peak detector 51 A signal as shown in FIG. 5B is output and supplied to the comparator 53. The output of the peak detection circuit 51 corresponds to the unrecorded portion as follows.
The level becomes low, and the portion corresponding to the low recording portion becomes high level. Therefore, by appropriately setting the reference level vth, the output of the comparator 53 becomes high level only when the low recording portion is read as shown in FIG. 4(C). This high level signal is supplied as a recorded green portion detection signal to a control circuit (not shown), etc., and a low recorded portion is discriminated from an unrecorded portion.

In the conventional recorded area detection circuit as described above, in the case of a write-once disc, the R detected in the unrecorded area and the low recorded area is
Since there is a sufficient difference in the F-times signal level, it is possible to distinguish between a low recorded area and an unrecorded area without error. However,
In the case of a magneto-optical disk, there are an unerased track in the unrecorded area immediately after the disk was manufactured and an erased track that has been erased. As shown in (B), the level is sufficiently low compared to the RF multiplied signal shown in (C) of the same figure that is read from the low recording area, but in the unerased track, it is read as shown in (A) of the same figure. There is RF multiplied signal noise, and the level of this noise is not different from the RF multiplied signal level read from the low recorded area, so there is a problem that it is impossible to distinguish between recorded green areas and unrecorded areas. Ta.

If the entire disk is erased immediately after the disk is manufactured, there will be no unerased areas, and low-recorded areas and unrecorded areas can be distinguished using a simple circuit based on the method ① above. become. However, erasing the entire area is time-consuming and impractical.

Summary of the invention [Object of the invention] The present invention has been made in view of the above points, and includes:
It is an object of the present invention to provide a recorded portion detection circuit for an optical disc player that can discriminate between a low recorded portion and an unrecorded portion of a magneto-optical disk.

[Structure of the Invention] The recorded portion detection circuit in the optical disc player according to the present invention includes synchronization signal separation means for extracting the synchronization signal in the video format signal from the output of the demodulation means for demodulating the RF multiplied signal read from the optical disc. established,
As long as the synchronization signal in the video format signal is extracted from the synchronization signal separation means, the recorded portion detection signal is generated.

[Operation of the invention] With this configuration, even if the noise read from the unerased portion is demodulated, a video format signal is not obtained.
Therefore, no synchronizing signal is output from the synchronizing signal separating means, and no recorded portion detection signal is output. Therefore, only when a low recorded portion is read, a video format signal is obtained, a synchronizing signal is output from the synchronizing signal separating means, and a recorded portion detection signal is output.

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1 showing an embodiment of the present invention, a magneto-optical pickup 1 includes a semiconductor laser 2 as a light source, and a light receiving element 3.4 that receives light from both channels of a differential optical system and performs photoelectric conversion. is built-in. The light-receiving elements 3 and 4 detect, for example, laser light emitted from the semiconductor laser 2 and reflected by the recording surface of the disk 5 through analyzers, and one detects the positive direction component of the Kerr rotation angle. However, the other detects the negative component of the Kerr rotation angle. The disk 5 is rotationally driven by a spindle motor 6.

'Although not shown, the pickup 1 further includes a focus actuator and a tracking actuator, and these two actuators are driven by a focus servo circuit and a tracking servo circuit, respectively. The laser beam emitted from the semiconductor laser 2 is accurately focused on the recording surface of the disk 2 by these two actuators, the focus servo circuit, and the tracking servo circuit to form a beam spot, and this beam spot is reflected by the rotation of the disk 5. As a result, it will move along the pre-group.

Outputs a and b of the light receiving element 3.4 are supplied to a demodulation circuit 8 and an address detection circuit 9 via a head amplifier 7, respectively. The demodulation circuit 8 has a subtracter in its manual section that subtracts one of the outputs a and b of the light receiving elements 3 and 4 from the other, and the difference signal (a - b) produced by this subtracter is based on the information recorded magneto-optically. A read RF multiplied signal is obtained, and by FM demodulating this, a reproduced video format signal is obtained. The address detection circuit 9 has, for example, an adder configuration that adds the outputs a and b of the light receiving element 3.4, and the sum signal (a+b
) is obtained as address information recorded in advance as a bridle address pit. This address information signal becomes one input of the phase comparator 10.

The other input of the phase comparator is that in the recording (RFC) mode, the vertical synchronizing signal separated by 6 minutes from the video format signal to be recorded is used, and in the playback (PB) mode, the vertical synchronizing signal generated based on the clock pulse is Supplied. That is, the composite synchronization signal extracted from the recorded video format signal in the synchronization extraction circuit 11 becomes an input to one fixed contact RFC of the changeover switch 12,
A composite synchronization signal generated from a synchronization signal generation circuit 14 based on a clock pulse outputted from a clock generation circuit 13 consisting of a crystal oscillator, etc. is used as the human power for the other fixed contact PB of the changeover switch 12, and is used for recording (REC). ) /
The changeover switch 1 is activated in response to a changeover control signal supplied from a controller (not shown) in accordance with the playback (PB) operation mode.
2, one of the composite synchronization signals is selected, and a vertical synchronization signal is separated from the selected composite synchronization signal in the synchronization separation circuit 15 and becomes the other input of the phase comparator 10. The phase comparator 10 detects the phase difference between one of the vertical synchronization signals and the address information signal depending on the operation mode, and supplies the detected phase difference to the spindle servo circuit 16. The spindle servo circuit 16 controls the rotational drive of the spindle motor 6 in accordance with this phase difference signal.

In the recording mode, the video format signal to be recorded is supplied to the modulation circuit 17 and subjected to FM modulation processing. The FM signal output from the modulation circuit 17 is transmitted to the laser drive circuit 1.
8, the laser power of the semiconductor laser 2 in the pickup 1 changes according to the FM signal by the action of the laser drive circuit 18, and magneto-optical recording is performed.

On the other hand, in the playback mode, the playback video format signal obtained by modulating 1M1a in the demodulation circuit 8 is supplied to the signal processing circuit 20, and is also used for synchronization sampling as a synchronization signal separation means in the recorded portion detection circuit 30 according to the present invention. The signal is supplied to the circuit 31.

The synchronization sampling circuit 31 is configured to output a composite synchronization signal obtained by slicing, for example, a video format signal at a level slightly lower than the pedestal level. The horizontal synchronization signal (hereinafter simply referred to as a detection synchronization signal) in the reproduced composite synchronization signal extracted by the synchronization extraction circuit 31 is supplied to a hunting logic circuit 33 and a synchronization state detection logic circuit 34, respectively. The noting logic circuit 33 determines whether the mode is a counting mode in which synchronization is carried out or another non-hunting mode based on the presence or absence of a detected synchronization signal input and the synchronization flag supplied from the synchronization state detection logic circuit 34. to do. When the detection synchronization signal is input to the hunting logic circuit 33 in the hunting mode, this detection synchronization signal passes through the hunting logic circuit 33 and the OR gate circuit 35 and becomes the load (LOAD) input of the synchronization counter 36 . By this load input, the synchronous counter 36 is loaded with the load value set by the loading logic circuit 37, and at the same time, the synchronous counter 36 starts counting at the cycle of the internal clock.

Based on the count value of the synchronization counter 36, the window generation circuit 39 generates a window pulse of a predetermined width, and the window end detection circuit 40 detects the window end, that is, the falling edge of the window pulse. The detection output of the window end detection circuit 40 is OR
It passes through the gate circuit 35 and becomes a load input to the synchronous counter 36, and also becomes a trigger input to the loading logic circuit 37. The loading logic circuit 37 sets a predetermined load value in response to the detection output of the window end detection circuit 40.

The synchronization state detection logic 34 is for determining whether the synchronization state is present based on the count value of the synchronization compensation counter 41, and detects the detected synchronization signal within the window pulse output from the window generation circuit 39 in the asynchronous state. is input, the synchronization compensation counter 41 is enabled for counting, and the count value N becomes a predetermined value (for example, "2").
”), the synchronization flag is set to “H” level, that is, the synchronization state is set. Then, if the detected synchronization signal is input within the window pulse, the synchronization compensation counter 41 is cleared, and furthermore, in the synchronization state, the synchronization signal detected within the window pulse is input. If the synchronization signal is not input, the synchronization compensation counter 41 is enabled for counting, and the count value becomes a predetermined value (for example, "
4), it is determined that synchronization has been lost and the synchronization flag is set to “L”.
It has a configuration in which synchronization detection logic is set up so that the level is determined.

The "H" level synchronization flag output from the synchronization state detection circuit 34 is sent to the control circuit 25 as a recorded portion detection signal.
is supplied to The control circuit 25 is configured to supply various commands and data to each section of the signal processing circuit 20 in accordance with the recorded portion detection signal. In addition, the signal processing circuit 20
For example, synthesizes a luminance signal corresponding to a character or the like represented by data output from the control circuit 25 into a video format signal, and prohibits output of the video format signal in response to an output prohibition command output from the control circuit 25. It is configured as follows. The video format signal processed in this signal processing circuit 20 is supplied to an output terminal.

The operation of each part in the above configuration will be explained with reference to the timing chart of FIG. 2.

First, when the synchronization flag is at "L" level, that is, in an asynchronous state and no detection synchronization signal is input, the hunting logic circuit 33 is in hunting mode, and in this / When this happens (time t1), the mode becomes non-hunting mode. At this time, the input detection synchronization signal passes through the hunting logic circuit 33 and the OR gate circuit 35 and becomes the load input of the synchronization counter 36. As a result, the synchronous counter 36 is incremented from the load value at the cycle of the internal clock at the same time as the load value set by the loading logic circuit 37 is loaded. Then, when the count value of the synchronization counter 36 reaches the target value, a window pulse is generated by the three window generation circuits (time t2). The pulse width of the window pulse at this time is set to be the pulse width of the synchronization signal ±α clock width.

If the detection synchronization signal is not input within the window pulse,
The hunting logic circuit 33 enters the hunting mode again and waits for the next detection synchronization signal. Then, when the next detection synchronization signal is input manually (time t3), the hunting logic circuit 33 enters the non-hunting mode again. In this non-hunting mode, when a detected synchronization signal is manually input within the window pulse (time t4>), the synchronization state detection logic circuit 34 puts the synchronization compensation counter 41 into a count enable state. The value increases by '1'' and a counting operation is performed at the cycle of the internal clock. Then, when this count value N becomes, for example, N-2 (time t5),
That is, when the detected synchronization signal occurs twice in succession at a predetermined interval, the synchronization state detection logic circuit 34 detects this, sets the synchronization flag to "H" level, and determines the synchronization state.

Subsequently, when the detected synchronization signal is input within the window pulse (time t6), the synchronization state detection logic circuit 34 clears the synchronization compensation counter 41, so that the count value becomes N0. In this state, even if the erroneously detected detection synchronization signal is input outside the window pulse (time ty), this detection synchronization signal is blocked by the hunting logic circuit 33 because it is outside the window pulse. The synchronization counter 36 is never loaded.

On the other hand, when the detected synchronization signal that should be input within the window pulse is missing (time t8), the synchronization counter 36
is loaded by the detection output of the window end detection circuit 40, so in the timing generation circuit 38,
The synchronization signal is continuously generated at synchronization intervals without any loss. At this time, the synchronization counter 36 is loaded with the corrected load value, thereby correcting the pulse width of the window pulse.

Furthermore, if the detected synchronization signal is not input within the window pulse, the synchronization compensation counter 41 becomes count enabled, and the count value increases by all. For example, if this state continues four times in a row, the synchronous state detection logic circuit 3
4, it is determined that the synchronization is out of synchronization and the synchronization flag is set to the "L" level. When the detected synchronization signal is manually input within the window pulse before the fourth consecutive pulse (time t9), the synchronization state detection logic circuit 34 clears the synchronization compensation counter 41, and the count value becomes N-0.

With the above operation, two consecutive
If the detected synchronization signal is output at the correct interval, the synchronization flag becomes "H" level, and the low recording (p) detection signal is output.If the detected synchronization signal is not missed several times in succession, the synchronization The flag remains at the "H" level, and the low recording detection signal is continuously output.

Therefore, when the green portion described above is read, the video format signal is demodulated in the demodulation circuit 8 and supplied to the synchronization extraction circuit 31, so that the horizontal synchronization signal is continuously output from the synchronization extraction circuit 31. The synchronization flag is “
The signal becomes H'' level and a voice signal indicating that the measurement has been performed is output.

On the other hand, when an unerased part of the unrecorded part is read, noise having a level that is the same as that of the RF signal is supplied to the first demodulation circuit 8, but even if the noise is demodulated, the video format signal remains unchanged. is never obtained, so the demodulation circuit 8 never outputs a video format signal. Therefore, even if a signal similar to the horizontal synchronization signal is accidentally output once from the synchronization extraction circuit 31, it is impossible for a signal similar to the horizontal synchronization signal to be output continuously, and the synchronization flag may be incorrectly set. The recorded eave edge detection signal is not output at the "H" level, and it is possible to distinguish between a low recorded area and an unrecorded area.

Although the case of a player that plays magneto-optical discs has been described above, the present invention is applicable to other players such as players that play write-once discs, players that can play both write-once discs and magneto-optical discs. The invention can also be applied to optical disc players.

As described in detail of the invention, in the recorded portion detection circuit in the optical disc player according to the present invention, a synchronization signal is extracted from the output of the demodulation means for demodulating the RF multiplied signal read from the optical disc. A signal separating means is provided, and as long as the synchronizing signal in the video format signal is extracted from the synchronizing signal separating means, the green area detection signal described above is generated. Therefore, in the optical disc player according to the present invention, even if the noise read from the unerased portion of the magneto-optical disc is demodulated, a video format signal cannot be obtained, so the synchronization signal is not output from the synchronization signal separation means. Therefore, the recorded green area detection signal is not output, and only when the recorded area is read, a video format signal is obtained, a synchronization signal is output from the synchronization signal separation means, and a recorded green area detection signal is output. Therefore, it is possible to eliminate errors in determining the recorded portion and the unrecorded portion.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a timing chart for explaining the circuit operation of FIG. 1, and FIG. 3 is a circuit block diagram showing a conventional recorded area detection circuit. , FIG. 4 is a waveform diagram showing the operation of the circuit of FIG. 3, and FIG. 5 is a waveform diagram showing the RF multiplied signal read from the magneto-optical disk. Explanation of symbols of main parts 1...Magneto-optical pickup 5...Optical disk 8...Demodulation circuit 31...Synchronization sampling circuit 34... Synchronous state detection logic 39...
・Window generation circuit applicant

Claims (2)

[Claims] (1) A recorded portion detection circuit for an optical disc player, comprising a reading means for reading a recorded signal of an optical disc capable of recording a video format signal, and a demodulating means for demodulating the output of the reading means to obtain a video format signal. a synchronization signal separation means for extracting and outputting a synchronization signal in the video format signal from the output of the demodulation means; and as long as the synchronization signal in the video format signal is extracted from the synchronization signal separation means, recorded portion detection is performed. 1. A recorded portion detection circuit in an optical disc player, comprising detection signal generation means for generating a signal. (2) The detection signal generation means generates a window signal for a predetermined period every time a time corresponding to the period of the synchronization signal elapses from the output point of the signal extracted as the synchronization signal from the synchronization signal separation means. a window signal generating means for generating a window signal; a counting means for continuously counting the number of times a signal is output from the synchronizing signal separating means within the predetermined period each time the window signal is output; 2. The recorded portion detection circuit for an optical disc player according to claim 1, further comprising means for generating a recorded portion detection signal when the predetermined value is exceeded.