JPH0619910B2 - Recording disk information reproducing device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a recording disc information reproducing apparatus, and more particularly to a reproducing layer for reproducing recorded information of a recording disc on which a digital signal is recorded.

BACKGROUND ART As a recording disc on which a digital signal is recorded, there is known a digital audio disc on which an audio signal is subjected to predetermined digital modulation processing and pulse trained, that is, a so-called compact disc (hereinafter abbreviated as CD), More recently, a system in which an audio signal is digitized by a predetermined digital modulation system into a FM signal of a video signal and an audio signal and a pulse train signal is superimposed and recorded (Japanese Patent Application No. 58-45780).
Video discs (hereinafter abbreviated as LDD) have been developed.

In such a recording system, the audio signal has two channels, and the audio carriers of 2.3 MHz and 2.8 MHz are FM-modulated by two audio channel signals. Further, the video signal is frequency-converted so that the sync chip has a 7.6 MHz, the pedestal level is 8.1 MHz, and the white peak is 9.3 MHz. The audio signal is further digitized by a modulation method such as POM (Pulse Code Modulation) and converted into a pulse train signal.

This pulse train signal is, for example, EFM (Eight to Fourt).
The signal is suitable for recording by the een modulation method, and the frequency spectrum is a frequency component of a pulse train having a width of 3T to 11T. Where T is PCM
It shows the bit period of the signal. A 3T pulse is about 72
0 KHz, 11T pulse of maximum width is about 200 KHz. Such a pulse train signal is superimposed on the video main carrier at a level of about 1/10 or less, and is slice-amplified near the zero cross point to be a pulse width modulated signal, which is a recording signal.

RF (high frequency) obtained from a recording disc on which video signals and audio signals are recorded by the above recording method
The frequency spectrum of the signal is as shown in FIG. In FIG. 1, a component A is a digitized audio signal component, a component B is an audio FM signal component, a component C is a color information component in a video FM component, and a component D is a video FM signal. It is a luminance information component.

Since the dynamic range of the digitized audio signal can be set to about 90 dB or more, the sound quality can be remarkably improved as compared with the recording / reproduction of the audio signal by the FM modulation method.

By the way, in a general demodulator for a PCM digital signal in a CD player, the read clock is fixed,
On the other hand, the rotation of the recording disk is phase-synchronized, and the information once written in the memory is read in synchronization with the read clock by the write clock synchronized with the reproduction clock signal, thereby removing the jitter which is the time axis fluctuation component. It is composed.

On the other hand, in the case of demodulating the digital signal extracted from the reproduced signal by the video reproducing device at the time of reproducing the LDD, the reproduced signal is already synchronized with the reference signal for video synchronization, and the demodulating device in the conventional CD reproducing device is used. As described above, when data is read from the memory on the PCM demodulation side by using separate reference signals, the reproduced video signal and the reproduced and demodulated audio signal may be temporally deviated due to a slight phase difference between the two reference signals. However, a blank state occurs due to memory overflow or too much data read.

Therefore, when developing a reproducing apparatus capable of reproducing both a CD and an LDD, it is necessary to solve the above-mentioned various problems in considering the sharing of the demodulation system for the purpose of cost reduction. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described points, and reliably reproduces a jitter-free digital signal by suppressing a jitter component contained in a reproduced digital signal regardless of whether a CD or an LDD is reproduced. It is an object of the present invention to provide a recordable disc information reproducing apparatus which can be obtained.

A recording disc information reproducing apparatus according to the present invention includes a demodulating means for demodulating a reproduced digital signal, a writing means for writing a demodulated output of the demodulating means into a memory in synchronization with a reproduced clock signal included in the reproduced digital signal, and the memory. And a read clock generation circuit for generating a read clock signal for reading the stored information in synchronism with the reproduction clock signal, and a loop filter for band limitation is inserted in the control loop of the read clock generation circuit. The cutoff frequency of the loop filter is set lower than the eccentric frequency of the recording disk during reproduction.

Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the recording disk information reproducing apparatus according to the present invention. This playback device is a CD
And LDD, a so-called compatible player capable of reproducing a normal video disc (hereinafter abbreviated as LD) in which video signals and audio signals are frequency-modulated and recorded. As described above, in this player, since the video discs (LD, LDD) and the digital audio discs (CD) have different reproduction rotational speeds, the LD, LDD rotational drive spindle motor 1 and the CD are used.
A rotation driving spindle motor 2 is provided. The spindle motors 1 and 2 are selected according to the type of the disc to be reproduced, and are switched by a switching mechanism 4 having a motor 3 as a drive source.

In order to detect the disc size of the disc 5 to be reproduced, for example, three detection sensors 6, 7 and 8 are provided corresponding to the disc size in the disc radial direction. The disc size is about 5 inches (12 cm) in the case of a CD, and 8 types and 12 inches in the case of a video disc (LD, LDD). The outputs of the three detection sensors 6, 7 and 8 are waveform-shaped by the waveform shaping circuit 9 and then supplied to the disc discriminating circuit 10. For example, an optical sensor is used as the detection sensor, but the detection sensor is not limited to this.

In the disc discrimination circuit 10, the disc to be reproduced is a CD or LDD based on the detection outputs of the detection sensors 6, 7 and 8.
It is determined which of the three types of discs, the LD and the LD, is. FIG. 3 shows a specific circuit configuration of the disc discriminating circuit 10. In the figure, in the case of CD,
The disk size is determined to be the minimum (12 cm), and the detection output of the minimum circumference detection sensor 6 and the inverters 79, 80
AN which makes the inverted output of the detection sensors 7 and 8 which passed through 3 inputs
The output of the D gate circuit 78 becomes the CD discrimination information. That is, when the detection sensor 6 is on and the other detection sensors 7 and 8 are off, it is discriminated as a CD. In the case of a video disk, since the disk sizes are 8 inches and 12 inches, the detection output of the detection sensor 7 or 8 becomes one input of each AND gate circuit 70, 71 via the OR gate circuit 69. A frame synchronization detection signal generated when a frame synchronization signal is detected by a frame synchronization detection circuit 21, which will be described later, is input to the other input of the AND gate circuit 71 and is inverted by the inverter 72 to be output to the other of the AND gate circuit 70. It also serves as an input. Then, when the detection output of the detection sensor 7 or 8 is generated and the frame synchronization detection signal is input, the LDD discrimination information is output from the AND gate circuit 71, and when the frame synchronization detection signal is not input, the AND gate circuit 70 outputs the LD. Discrimination information is output.
These pieces of discrimination information are used to drive the indicator 11 that displays the type of disc and as switching signals for various switches described later.

A pickup 12 for reading recorded information from the disk 5 is carried by a slider base (not shown) movably provided in the radial direction of the disk 5, and the slider base is a drive composed of a slider motor, a reduction gear and the like. It is driven by a mechanism (not shown). The read information read from the recording disk 5 by the pickup 12 is supplied to a digital information demodulation system 14, an analog audio demodulation system 15 and a video demodulation system 16 via an RF amplifier 13. RF amplifier 13
Has a wide band of about 5 KHz to 14 MHz, and a single amplifier can amplify a reproduced PCM audio signal, a reproduced FM audio signal, and a reproduced video signal.

The digital information demodulation system 14 is provided with a changeover switch 17 that switches according to the type of the reproduction disc, and this switch 17 is the disc discrimination circuit 10 described above.
In the case of LDD, it is switched to the side a, and in the case of CD, it is switched to the side B based on the disc information from. That is, LD
The signal processing system of the reproduced digital signal is switched between the D reproduction and the CD reproduction. When playing a CD, the playback RF output is PCM audio information.
The audio information is MTF (Modulation Transfer Functi) that is used by the equalizer 18 to compensate for the particularly high frequency range.
on) compensation will be applied.

On the other hand, in the case of LDD, FM audio information and FM
The PCM audio information included in the reproduction RF signal together with the video information is extracted by the LPF (low-pass filter) 19 and supplied to the de-emphasis circuit 20. PCM
The audio information is, for example, an EFM signal, but if the digital signal is directly superimposed on the FM-modulated video signal at the time of recording, the digital signal component will be disturbed by the low-frequency component of the FM video signal. The low frequency components are boosted and recorded. Therefore, at the time of reproduction, the low-frequency component boosted at the time of recording is inversely compensated by the de-emphasis circuit 20. As a result, the S / N ratio of the digital signal can be improved with respect to low frequency noise during recording and reproduction.

Instead of switching the signal processing system using the changeover switch 17, the power supply to the circuits of each signal processing system is turned on.
Even if it is turned off, the same effect can be obtained.

The reproduced EFM signal that has passed through the changeover switch 17 is supplied to the EFM demodulation circuit 22 via the frame synchronization detection circuit 21 and also to the reproduced clock extraction circuit 23, depending on the reproduced clock extracted by the reproduced clock extraction circuit 23. The EFM demodulation circuit 22 demodulates into a PCM digital signal. This demodulated signal is written to the memory 24 such as a RAM (random access memory) under the control of the memory controller 25. At this time, the memory controller 25 is synchronized with the write clock which is the frequency-divided output of the reproduction clock frequency divider 26. Write.

The stored information is read from the memory 24 in synchronization with a read clock obtained by dividing the oscillation output of a VCO (voltage controlled oscillation) 27 in a PLL (phase locked loop) circuit by a frequency divider 28. It has become. The PLL circuit is based on the VCO2 described above.
7. Divided output of the recovered clock frequency divider 29 and VCO
A phase comparator (P / C) 31 having two inputs of the oscillation output of the frequency divider 27 and the frequency division output of the frequency divider 27, an LPF (low-pass filter) 32 having this comparison output as an input, and this LPF.
The output voltage of 32 and the reference voltage Vref ₁ are alternatively VCO
It is constituted by a changeover switch 33 which is supplied to 27.

In the PLL circuit, the changeover switch 33 switches the output voltage of the LPF 32 on the a side during LDD reproduction and switches to the b side during CD reproduction to change the reference voltage Vref ₁ to VCO 2 based on the discrimination result of the disc discrimination circuit 10 described above.
Supply to 7. This allows the memory 2 to be used during LDD playback.
The read clock for reading the stored information from 4 is PL
By the L circuit, the phase is synchronized with the reproduction clock, and the loop switch 59 described later is turned on (closed) at the time of reproducing the CD, so that the output of the phase comparator 31 becomes LP.
By driving the CD rotation driving spindle motor 2 through F77, the reproduction clock is phase-synchronized with the fixed clock obtained by the VCO 27 in which the bias is fixed.

The digital signal thus read is converted into an analog audio signal by the D / A (digital / analog) converter 34, and becomes left and right reproduced audio outputs via the LPFs 35L and 35R.

The usage status in the memory 24 is constantly monitored by the memory controller 25, and when the memory 24 overflows from the controller 25 or becomes blank (no data exists), information indicating these states is supplied to the voltage generator 36. To do. During LDD reproduction, this voltage generator 3
6 generates a positive control voltage when the memory 24 overflows and a negative control voltage when the memory 24 becomes blank according to the information indicating the usage status of the memory 24 from the memory controller 25. , The output voltage of the LPF 32 is superimposed and supplied to the VCO 27 via the change-over switch 33 to control the frequency of the read clock.

In this way, the amount of data stored in the memory 24 is constantly monitored, and when the capacity and processing capacity of the memory 24 become excessive or insufficient, a positive or negative control voltage is generated and the PLL circuit is requested to take measures. By doing so, the memory 24 can always be maintained in a normal state.

In the analog audio demodulation system 15, the outputs of BPFs (band pass filters) 37L and 37R which pass only the audio carrier components of 2.3 MHz and 2.8 MHz from the reproduced RF signal are FM demodulators 38L and 38, respectively.
FM demodulation at R, de-emphasis circuit 39
Left and right playback audio output is provided via L and 39R.

In the video demodulation system 16, only the video information of the reproduction RF signal is extracted by the BPF & notch circuit 40. This BP
In the F & notch circuit 40, the EFM component and 2.3 MHz, 2,8 MHz included in the reproduction RF signal during LDD reproduction
The audio carrier component of is actively removed. This extracted information is sent to F through the limiter circuit 41.
It is supplied to the M demodulator 42 and FM demodulated. This demodulated output is sent to the dropout compensator (DOC) via the LPF 43.
44, and the compensator 44 performs dropout compensation. This dropout compensator 44 is
For example, an analog switch that is turned off by a detection output of a dropout sensor (DOS) 46 that detects a dropout based on a reproduction RF signal supplied via an HPF (high-pass filter) 45, a switch output end, and a reference. It is configured by a hold capacitor provided between the potential point and the potential point. Therefore, when a dropout occurs, the output level of the LPF 43 immediately before the output of the dropout sensor 46 is held and sent to the next-stage circuit to perform dropout compensation. The output of the dropout compensator 44 becomes the video output.

The output of the dropout compensator 44 is the horizontal sync separation circuit 4
It is also supplied to 7, and the horizontal synchronizing signal is separately output. This horizontal synchronizing signal is supplied to the phase comparators 48 and 49, and the phase difference from the reference signal output from the reference signal generator 50 is detected. The output of the phase comparator 48 becomes one input of the adder 51, and the output of the phase comparator 49 is the equalizer amplifier 5.
It is the other input of the adder 51 via 2. The output of the adder 51 is equalizer amplifier 53 and driver 5.
The spindle motor 1 for driving the LDD and LD is driven via 4. This is the spindle servo system. The output of the equalizer amplifier 52 drives an actuator (not shown) incorporated in the pickup 12 via a loop switch 55, a changeover switch 56 and a driver 57. By driving this actuator, the light spot for reading information is displaced in the tangential direction of the recording track of the disc. This is the tangential servo system. Incidentally, the actuator may be a tangential mirror for displacing the information reading light spot in the tangential direction of the recording track of the disc by rotating, or the lens may be displaced in a direction perpendicular to the optical axis. Accordingly, the information reading light spot may be deviated in the tangential direction of the recording track of the disc.

The loop switch 55 is turned on (closed) in response to the spindle lock signal output from the spindle lock detection circuit 58 when the lock of the spindle servo system is substantially completed. That is, at the start of reproduction, first, the spindle motor 1 is driven by the output of the phase comparator 48 to perform coarse adjustment of the time axis (spindle servo), and when the spindle servo lock is substantially completed by this, the loop switch 55 is turned on. It turns on and the phase comparator 4
The actuator is driven by the output of 9 and the time axis is finely adjusted (tangential servo). According to this, the tangential servo system can remove the residual jitter component that cannot be removed by the spindle servo system.

However, even in the tangential servo system, the mechanical system such as the actuator drive mechanism cannot sufficiently follow the high frequency component of the residual jitter, so that the jitter cannot be completely removed. Therefore, in the digital information demodulation system 14 described above, a PL for generating a read clock is used.
By setting the cutoff frequency of the LPF 32 of the L circuit lower than the maximum frequency of the band of the tangential servo loop to cut the high frequency component of the residual jitter, the residual jitter component can be removed. More preferably, by setting the cutoff frequency of the LPF 32 lower than the eccentricity frequency of the disc (30 to 8 Hz in the case of LDD), it is possible to completely eliminate the jitter caused by the eccentricity of the disc.

Although the spindle servo and the tangential servo are performed on the basis of the horizontal synchronizing signal, the same effect can be obtained by performing the spindle servo and the tangential servo on the basis of the color subcarrier of 3.58 MHz included in the reproduced FM video signal.

The above is the servo system during reproduction of the video disk (LDD, LD), but during reproduction of the CD, spindle servo is performed based on the output of the phase comparator 31 in the digital information demodulation system 14 described above. That is,
The output of the phase comparator 31 drives the spindle motor 2 for CD rotation drive through the loop switch 59 and the driver 60 which are turned on (closed) during CD reproduction. Conventionally, the above-mentioned tangential servo has not been performed during CD reproduction, but since the spindle motor 2 cannot sufficiently follow the high frequency component of the output signal of the phase comparator 31 which is a time axis error signal, this embodiment is performed. In the example, HPF
The high frequency component of the time axis error signal extracted by 61 also employs a servo for driving an actuator in the pickup 12 via the changeover switch 56 and the driver 57, that is, a tangential servo. The change-over switch 56 is switched to the a side when the LDD and LD are reproduced and to the b side when the CD is reproduced, based on the discrimination result of the disc discriminating circuit 10.

Although the tangential servo during CD reproduction is performed based on the frequency division output of the reproduction clock extracted by the reproduction clock extraction circuit 23, the frequency division of the frame synchronization signal detected by the frame synchronization detection circuit 21 is performed. Even if it is performed based on the output, the same effect can be obtained because the frame synchronization signal and the reproduction clock have a synchronous relationship.

The output of the spindle lock detection circuit 58 is the inverter 62.
It is inverted by and becomes one input of the OR gate circuit 63 as a spindle unlock signal indicating that the spindle servo system is not in the locked state. The other input of the OR gate circuit 63 is supplied with a random access information signal generated at the time of a random access command such as scan, search, or jump. The LD information output from the disc discrimination circuit 10 is also input to the OR gate circuit 63. OR
The output of the gate circuit 63 is supplied to the recovered clock extraction circuit 23 via the control command circuit 64.

A specific circuit configuration of the recovered clock extraction circuit 23 is shown in FIG. In this figure, the reproduced EFM signal is the phase comparator 6
5, the phase difference from the oscillation output of the VCO (voltage controlled oscillator) 66 is detected, and the phase difference signal is supplied to the VCO 66 via the LPF 67 and the changeover switch 68. With the above, a PLL circuit that generates a reproduced clock is configured.

The change-over switch 68 is normally on the a side and supplies the output of the LPF 67 to the VCO 66.
When a command signal is output from No. 4, in response to this command signal, it is switched to the b side and the predetermined reference voltage Vref ₂ is changed to V.
Supply to CO66. That is, when the spindle servo is not in the locked state, or when the information reading light spot performs a track jumping operation by a random access command such as scan, search, or jump, and when the LD is played, V
By applying the reference voltage Vref ₂ to the CO 66 and fixing its oscillation frequency to a value close to the reproduction clock frequency, during CD or LDD performance, the spindle servo is locked or the random access command is released. It is possible to speed up the lock-in of the later reproduction clock.

Referring again to FIG. 2, the audio output section has a pair of left and right output terminals 73L and 73R of the analog audio output system.
And a pair of left and right output terminals 74L and 74R of the digital audio output system. Output terminal 73L,
The audio output from the analog audio demodulation system 14 is supplied to 73R. This audio output is output terminals 74L, 74 via the changeover switch 75 during LD reproduction.
Also supplied to R. The changeover switch 75 is, for example, on the a side when the LD reproduction is in a normal state, and is switched to the b side based on the disc discrimination information from the disc discrimination circuit 10 during the LDD and CD reproduction. And digital information demodulation system 1
The audio output from 4 is the left / right mode selector switch 7
It is supplied to the output terminals 74L and 74R via 6L and 76R and the changeover switches 75L and 75R.

As a result, a normal audio signal is output from the output terminals 73L and 73R and the output terminals 74L and 74R during the LD reproduction, and the output terminals 74L and 74L and 74R during the LDD and CD reproduction.
The 74R outputs a high-quality audio signal, and LDD
During reproduction, normal audio signals are further output from the output terminals 73L and 73R.

The mode changeover switches 76L and 76R are provided to change over the output mode of the audio signal of the digital audio system at the analog stage. That is, when the audio output from the digital audio demodulation system 14 is stereophonic, the output mode described above is acceptable. For example, in the case of voice multiplexing, the L (left) channel is Japanese and the R (right) channel is foreign. The mode changeover switch 76L, which operates independently of each other,
By 76R, the sound output from the output terminals 74L and 74R can be switched to three output modes of Japanese and foreign languages, only Japanese and only foreign languages. The mode changeover switches 76L and 76R are driven separately according to control information from an operation unit (not shown).

Relays that operate independently are used as the mode changeover switches 76L and 76R. Normally, a relay having one movable contact and two fixed contacts is sufficient for signal switching, but in the present embodiment, a relay having one movable contact and two fixed contacts additionally. Is used. That is, if the relay 76L on the L channel side is described as an example, two sets of movable contacts s interlocking with each other are provided.
₁₁ and s _21, and two sets of fixed contacts s ₁₂ , ₁₃ and s ₂₂ , which are provided in pairs for the two sets of movable contacts s ₁₁ and s _{21 respectively} .
_The two fixed contacts s ₁₂ and s ₂₃ , which are the most distant from the two sets of fixed contacts, are input ends of two signals (left and right audio signals), and one movable contact s ₁₁ is an output end. There is. According to this, since there are two gaps between the left and right signal lines, it is possible to reliably prevent crosstalk between the left and right signals. It goes without saying that crosstalk can be more reliably prevented by further increasing the number of contacts and providing a large number of gaps.

Although not shown in the drawing, a focus servo system that controls the position of the pickup 12 in the direction perpendicular to the disc surface with respect to the disc 5 and a tracking servo system that controls the position of the pickup 12 in the disc radial direction are naturally provided. In these servo systems as well, it is preferable to switch the signal processing system of the error signal between the reproduction of the video disc (LDD, LD) and the reproduction of the digital audio disc (CD). Good servo can be performed regardless.

The digital signal recorded on the CD or LDD is
Besides audio information, it also includes digitized image information or control information for computer control.

As described above, according to the recording disc information reproducing apparatus of the present invention, the cutoff frequency of the loop filter (LPF32) inserted in the loop of the read clock generating PLL circuit is set to the recording disc at the time of reproducing. Since it is set to be lower than the eccentricity frequency, the jitter component due to the eccentricity of the disk can be removed, the jitter component contained in the reproduced digital signal can be surely suppressed, and the read clock phase-synchronized with the reproduced digital signal can be obtained. From
PCM demodulation without jitter is possible.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 was obtained from a recording disk in which a signal obtained by frequency-modulating a video signal and an audio signal and a signal obtained by PCM-modulating an analog signal and pulsed are superimposed and recorded. FIG. 2 is a diagram showing a frequency spectrum of an RF signal, FIG. 2 is a block diagram showing an embodiment of a recording disc information reproducing apparatus according to the present invention, and FIG. 3 is a block showing a concrete circuit configuration of the disc discriminating circuit in FIG. Figure,
FIG. 4 is a block diagram showing a specific circuit configuration of the recovered clock extraction circuit in FIG. Description of symbols of main parts 1 ... LD, LDD spindle motor 2 ... CD spindle motor 5 ... Recording disk 10 ... Disk discriminating circuit 12 ... Pickup 14 ... Digital information demodulation system 15 ... Analog audio demodulation System 16 ... video demodulation system 22 ... EFM demodulation circuit 23 ... reproduction clock extraction circuit 25 ... memory controller 27, 66 ... voltage controlled oscillator 37, 48, 49, 66 ... phase comparator 38, 42 ... FM demodulator 44 ... Dropout compensator 52, 53 ... Equalizer amplifier 76L, 76R ... Mode changeover switch

Claims (1)

[Claims] 1. A recording disk information reproducing apparatus capable of reproducing a recording disk in which a signal in which a video signal and an audio signal are frequency-modulated and a predetermined digital signal are superimposed and recorded, and demodulating the reproduced digital signal. Demodulating means, writing means for writing the demodulated output of the demodulating means to a memory in synchronization with a reproduced clock signal included in the reproduced digital signal, and a read clock signal for reading stored information from the memory as the reproduced clock signal. A read clock generating circuit for generating in synchronization, a loop filter for band limitation is inserted in a control loop of the read clock generating circuit, and a cutoff frequency of the loop filter is the recording disk at the time of reproduction. The recording disc information is characterized by being set lower than the eccentric frequency of Reproducing apparatus.