JPH02284589A - Recordable optical disk recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a reproduced output free from picture disturbance from the first by adding a DC component to the demodulation output of an FM demodulator of a reproducing system in an unrecorded area at the time of reproducing. CONSTITUTION:When an unrecorded area of an optical disk is irradiated with a laser beam at the time of reproducing, a switch 29 is closed because an RF signal is not obtained, and the FM carrier frequency which is outputted from an FM modulator 16 and is non-modulated or modulated only by a synchronizing signal is supplied to an FM demodulator 22. When the laser beam reaches a recorded area of the optical disk at a time t0 to obtain a reproduced RF signal, the switch 29 is turned off, and the reproduced RF signal inputted to the FM demodulator 22 is outputted as a demodulated video signal Sv. At such a time, a reproduced picture is immediately obtained because muting is released. This reproduced picture and a demodulation output SDC outputted before this picture are continuous.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a recording/reproducing device for a recordable optical disc that is sensitive to light and can write or read information at any location on a spiral track. It is something.

[Summary of the Invention] The present invention provides that, when reading information recorded on an optical disc, when a laser beam is irradiated to an area where no video signal is recorded on the optical disc, for example, a demodulator of a reproduction circuit Since the carrier frequency of the video signal is supplied to the unrecorded area and the playback output is obtained from the demodulator in the unrecorded area, the first playback image will not be distorted even when the video recording area is accessed. can do.

[Conventional technology]

Concave pits are arranged in a spiral on the recording surface of an optical disc,
By modulating the dimensions (duty) of this concave pit based on recorded information, digital audio signals,
or an optical disc (C
For D, VD), use a photosensitive recording medium whose reflectance changes when irradiated with laser light, or a recording medium that can form pits due to the heat generated when irradiated with laser light. Write-on optical discs on which information can be recorded and reproduced have also reached the stage of practical use.

In such writable optical discs, pre-grooves or sample bits for guiding the laser beam, track addresses, etc. are usually formed in advance along tracks on the recording surface, and the laser beam is irradiated along these tracks. By intermittent laser beams with recording signals, the temperature of the recording surface at the laser irradiation position is instantaneously raised, and the recording signals remain in the form of dot information or bit information.

The recording density is set in relation to the rotational speed of the optical disc, the laser beam wavelength, etc., but generally when recording a video signal that repeats in units of one field,
1 per track of an optical disc rotating at a constant angular velocity.
The image signal for one frame can be recorded.

Therefore, the same field screen as the number of spiral tracks of the optical disc can be recorded on one disc, but the recordable optical disc D has the same number of spiral tracks as the number of spiral tracks on the optical disc. However, as shown in FIG. ．． Since the image is read out only after it is recorded, a continuous screen is not necessarily formed during playback.

In this way, on the recording surface of the optical disc D, tracks T, , T2 . T3, and tracks Q, , Q2Q3 . on which no images have been recorded yet. If there is an unrecorded area consisting of A method is adopted in which muting is canceled when the signal is obtained.

By the way, the video signal recorded on the optical disc is an FM signal obtained by frequency modulating the video signal with a predetermined carrier frequency fc, and the frequency of the dark level indicating the black part of the video signal and the frequency of the white level indicating the white part are F
It is determined by the modulation index of the M signal.

On the other hand, the reproducing circuit uses a frequency demodulator to reproduce 1111 FM.
The signal is demodulated to obtain a video signal, but since the frequency demodulator has the characteristic of demodulating the carrier signal component as a DC signal of a value, as mentioned above, there are recorded areas and unrecorded areas on the optical disc. When reproducing an optical disc containing a mixture of .

When the recording area is irradiated with a laser beam at time to, a video signal Sv as shown in FIG. 5(a) is obtained from the FM demodulator.

By the way, when a DC output with such a step difference is supplied to the clamp circuit in a reproduction circuit, the transient characteristics of the circuit cause the sync tip level to jump as shown in Figure 5(b), and the waveform This makes it difficult to stably separate the synchronization signal components.

For this reason, even if the optical head moves from an unrecorded area to a recorded area during playback and muting is canceled, the initially output reproduced image will be distorted.
In particular, there was a problem with skew occurring at the top of the screen.

[Point 1 to be solved by the invention The present invention has been made in view of the above problems,
When reproducing a recordable optical disc, a means for detecting whether an RF signal is being reproduced from the optical disc is always provided, and when the detecting means does not detect an RF reproduction signal, that is, an unrecorded area of the optical disc. For example, when approaching the FM modulator of the reproduction system, a means for supplying the carrier frequency of the recording system to the input terminal of the reproduction system is installed so that an output signal is always obtained in the reproduction mode regardless of the presence or absence of recorded information. This is what I did.

[Effect]

In playback mode, a video signal or a signal corresponding to the DC level of this video signal is output to the output of the FM demodulator, so even when entering a recorded area from an unrecorded area, synchronization is established immediately. , it is possible to eliminate disturbances in the reproduced image.

[Embodiment] FIG. 1 is a block diagram of the main parts of the recordable optical disc recording and reproducing apparatus of the present invention, and numeral 10 converts an input composite video signal (Y+C) into an MPX video signal as described later. It is an MPX decoder.

This MPX decoder includes a Y/C separation circuit, an A/D converter,
Equipped with a D/A converter, three memory means, etc.
As described later, the color composite signal is separated into the carrier color signal component and the luminance signal, and the time axis of the color signal components (R-Y) and (B-Y) is compressed to 1/4, and the luminance signal is An MPX video signal is formed by continuation of a signal in which the time axis of the component is compressed to 1/2 in a time-division manner, and to which an audio signal converted into a digital signal is added.

Reference numeral 11 indicates a synchronization signal separation circuit, and reference numeral 12 indicates a waveform shaping circuit that forms a separated synchronization signal.

The audio signal SA to be recorded together with the video signal is the same <A/D
Audio decoder circuit 1 comprising a converter and a memory circuit
3, where it is converted into a digital signal with a compressed time axis.

The signal is then supplied to the synthesis circuit 14 together with the synchronization signal outputted from the waveform shaping circuit 12 mentioned earlier.

Reference numeral 15 indicates a pre-emphasis circuit for emphasizing high-frequency signal components, and reference numeral 16 indicates an FM modulator.

The FM modulator 16 is composed of, for example, a CO whose frequency changes depending on the voltage, and its carrier frequency is configured so that it changes slightly depending on the track position of the optical disc.

That is, when the laser beam is located on the inner circumferential side of the optical disk, the carrier frequency is 9.3MH2,
When moved to the outer circumference side, it is set so that 9.3 Mr (Z → 10.3 MH2), so that the recording and reproducing ability on the outer circumference side of the optical disk can be fully demonstrated.

Reference numeral 17 denotes an output amplifier for amplifying the MPX video signal converted into an FM signal, and by modulating the laser power of the optical head 18 with the output of the output amplifier 17, the MPX video signal is recorded on the optical disc.

Reference numeral 19 denotes a servo circuit, which rotates the spindle motor M so that the angular velocity is constant, and also drives the optical head 1.
8 tracking control and focus servo.

Reference numeral 20 denotes a head amplifier that amplifies the reproduced RF signal generated from the reflected light of the laser beam irradiated to the optical head 18 during reproduction, and the reproduced RF signal obtained from this head amplifier 20 is passed through the limiter circuit 21. The signal is then supplied to an FM demodulator 22, demodulated as an MPX video signal, and further supplied to a de-emphasis circuit 23.

The MPX video signal whose frequency characteristics have been changed before recording by the de-emphasis circuit 23 is input to the MPX encoder 24, where it is converted into a normal NTSC or PAL composite video signal or component video signal.

Furthermore, the digital audio signal included in the MPX video signal is subjected to signal processing by the audio encoder 25 and output as a continuous audio signal.

Note that 26 and 27 indicate a synchronization signal separation circuit and a waveform shaping circuit for the separated synchronization signal.

The optical disc recording and reproducing apparatus of the present invention includes a reproduction RF signal detection section 28 that detects whether or not a reproduction RF signal is output during reproduction, and a reproduction RF signal detection section 28 in such a circuit system.
A switch 29 that is opened and closed by the output of the signal detection section
It is characterized by having the following.

In the present invention, by adding the above-mentioned configuration, when the laser beam approaches an unrecorded area of the optical disc during reproduction of the optical disc, the output of the reproduction RF signal detection section disappears and the switch 29 is closed.

Then, the FM carrier frequency fc obtained from the FM modulator 16 of the recording system is supplied to the FM demodulator 22, and the FM demodulator 22 outputs a demodulated signal corresponding to this carrier frequency.

That is, in the embodiment of the present invention, when the laser beam is irradiated to the unrecorded area of the optical disk during reproduction, the switch 29 is closed because no RF signal is obtained. Therefore, the unmodulated FM carrier frequency output from the FM modulator 16 or the FM carrier frequency modulated only with the synchronization signal is F
The demodulated output S from the FM demodulator 22 is supplied to the FM demodulator 22 even in the unrecorded area as shown in FIG. C has been obtained.

Then, when the laser beam reaches the recording area of the optical disk at time point to and a reproduced RF signal is obtained, the switch 29
is turned off, and the reproduced RF signal input manually to the FM demodulator 22 is output as a demodulated video signal Sv.

At this point, mutating is canceled, so
A reproduced image can be obtained immediately.

Moreover, this reproduced image is the demodulated output S that was output before that. Since it is continuous with C, the waveform will not be distorted by the transient characteristics of the reproduction system circuit, especially the clamp circuit, and the synchronization signal will not be disturbed.

FIG. 3 shows the signal waveform (one horizontal period) seen in the MPX video signal recording and reproducing apparatus previously proposed by the present applicant. According to the present invention, following the horizontal synchronizing signal SH,
Audio data A I) converted to PCM digital signal
D T is inserted with the time axis compressed, and then the time axis is compressed by 1
/4 compressed two color difference signals BC (B-Y) and Rc
(RY) signal is inserted.

Further, the signal waveform is a time-division type signal waveform in which a luminance signal Y whose time axis is compressed to 1/2 continues.

Although such a video signal has a wide frequency band, the chrominance signal component and the luminance signal component are recorded at different positions, so the signal-to-noise ratio of the signal does not deteriorate due to cross modulation.

In the above embodiment, the carrier signal of the recording system is supplied to the FM demodulator 22 via the switch 29, but as shown by the dotted line in FIG. It may also be added to the output side of the FM demodulator 22 via the FM demodulator 22.

This DC bias can be a voltage proportional to the radius of the optical disk.

The optical disk recording and reproducing apparatus of the present invention is not limited to recording and reproducing MPX video signals, but can also be applied to recording and reproducing apparatuses for ordinary component video signals or NTSC video signals.

Furthermore, to detect an unrecorded area, an ID signal indicating that no information is recorded on the track is detected and a switch 29 is pressed.
The opening/closing control may be performed.

[Effects of the Invention] As explained above, the present invention provides the following advantages: When reproducing an optical disc in which video signals are sequentially recorded in predetermined areas of the optical disc, the FM demodulator of the reproducing system performs demodulation in the unrecorded area. Since a DC component is added to the output, there is an effect that when accessing and reproducing a recorded area from an unrecorded area, a reproduced output without image disturbance can be obtained from the beginning.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a writeable optical disc recording and reproducing apparatus showing an embodiment of the present invention. FIG. 2 is an explanatory diagram of the FM demodulation output waveform. FIG. 3 is a waveform diagram of an MPX video signal. FIG. 4 is an explanatory diagram of a recordable optical disc. FIGS. 5(a) and 5(b) are waveform diagrams showing the output of a conventional I'M demodulation circuit. In the figure, 15 is a pre-emphasis circuit, 16 is an FM modulator, 18 is an optical head, 22 is an I/M demodulator, 28 is a reproduced RF signal detection section, and 29 is a switch.

Claims (2)

[Claims] (1) In a recording and reproducing apparatus equipped with a circuit that writes recorded information on a desired track using the output of a laser beam irradiated to the optical disc and reads out the recorded information from the reflected light of the optical disc, the optical disc is reproduced. RF
A reproduction RF signal detection means for detecting the presence or absence of a signal, and means for adding a predetermined DC component to the demodulated output of the reproduction circuit system when an unrecorded area of the optical disc is detected by the output of the reproduction RF signal detection means. A recordable optical disc recording and reproducing device characterized by the following. (2) The recordable optical disc recording and reproducing apparatus according to claim (1), characterized in that a carrier frequency of the recording system is supplied to a demodulator of the reproducing system and a DC component is added thereto.