JPH0553113B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a recorded information reproducing apparatus, and more particularly to a reproducing apparatus for reproducing recorded information including video information recorded on a recording medium.

BACKGROUND ART As a recording medium on which information including video information is recorded, for example, a video disk (hereinafter abbreviated as LD), in which a video signal and an audio signal are frequency-modulated and recorded, is known. At the time, the audio signal is digitized using a predetermined digital modulation method and a pulse train signal is superimposed and recorded on each FM modulated signal of the video signal and audio signal (Japanese Patent Application No. 1983-
45780)) has been developed.

In this recording method, the audio signal is made into two channels, 2.3MHz and 2.8MHz.
The audio carriers are each FM modulated by two audio channel signals.
In addition, the video signal has a sync chip of 7.6MHz, a pedestal level of 8.1MHz, and a white peak.
The frequency has been converted to 9.3MHz. The audio signal is further processed using PCM (Pulse Code).
The signal is digitized and converted into a pulse train signal using a modulation method such as "Modulation".

This pulse train signal is, for example, EFM (Eight to
Fourteen Modulation) method makes the signal suitable for recording, and the frequency spectrum is 3
This becomes a frequency component of a pulse train having a width of T to 11T. Here, T indicates the bit period of the PCM signal, and the 3T pulse is approximately 720KHz, and the maximum width 11T pulse is approximately 200KHz. 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-crossing point to become a pulse width modulated signal, which is used as a recording signal.

Video signals and audio signals can be obtained from a recording disk recorded using the above recording method.
The frequency spectrum of the RF (high frequency) signal is as shown in FIG. In Figure 1, the component denoted by A is a digitized audio signal component, the component denoted by B is an audio FM signal component, the component denoted by C is a color information component in a video FM component, and the component denoted by D is a color information component in a video FM signal. This is a luminance information component.

Since the dynamic range of the digitized audio signal can be approximately 90 dB or more, the sound quality can be significantly improved compared to recording and reproducing audio signals using the FM modulation method.

FIG. 2 is a block diagram showing the configuration of a conventional recorded information reproducing apparatus for reproducing recorded information from such a recording disk.

Such playback devices, along with LDs and LDDs, are digital audio disks, so-called compact disks (hereinafter referred to as CDs), on which audio signals are subjected to predetermined digital modulation processing and pulse train recording.
It is a so-called compatible player that can also play the following files. This player has different playback speeds for video discs (LD, LDD) and digital audio discs (CD), so
LD, LDD rotation drive spindle motor 1 and CD
A spindle motor 2 for rotational driving is provided. These spindle motors 1 and 2 are selected depending on the type of disc to be played. For example, motor 3
The switching mechanism 4 uses a driving source as the driving source.

For example, three detection sensors 6, 7 and 8 are used to detect the disc size of the disc 5 to be played.
are provided corresponding to the disk size in the disk radial direction. Disc size is CD
In the case of , the outer diameter is approximately 5 inches (12 cm), and in the case of video disks (LD, LDD), there are two types of outer diameter: 8 inches and 12 inches. The outputs of the three detection sensors 6, 7, and 8 are waveform-shaped by a waveform shaping circuit 9 and then supplied to a disk discrimination circuit 10. As the detection sensor, for example, an optical sensor is used, but the detection sensor is not limited to this.

In the disk discrimination circuit 10, the detection sensors 6 and 7
Based on the detection outputs of and 8, it is determined which of the three types of disks, CD, LDD, and LD, the disk to be played back is. A specific circuit configuration of this disk discrimination circuit 10 is shown in FIG. In this figure, in the case of a CD, the disc size is determined to be the minimum (12 cm), and the detection output of the innermost detection sensor 6 and the inverted output of the detection sensors 7 and 8 via inverters 79 and 80 are the three inputs. do
The output of the AND gate circuit 78 becomes CD discrimination information. That is, when the detection sensor 6 is on and the other detection sensors 7 and 8 are off, it is determined that it is a CD. In the case of a video disc, since the disc sizes are 8 inches and 12 inches, the detection output of the detection sensor 7 or 8 becomes one input of each of the AND gate circuits 70 and 71 via the OR gate circuit 69.
In addition, a frame synchronization detection signal generated when a frame synchronization signal is detected from a frame synchronization detection circuit 21, which will be described later, becomes another input to the AND gate circuit 71 and is inverted by an inverter 72.
It also serves as another input to the AND gate circuit 70. When the detection output of the detection sensor 7 or 8 is generated and a frame synchronization detection signal is input, the AND gate circuit 71 outputs LDD discrimination information, and when the frame synchronization detection signal is not input.
LD discrimination information is output from the AND gate circuit 70. This discrimination information is used to drive an indicator 11 that displays the type of disk, and as a switching signal for various switches to be described later.

A pick-up 12 for reading recorded information from the disk 5 is supported by a slider base (not shown) that is movable in the radial direction of the disk 5, and the slider base is driven by a slider motor, a reduction gear, etc. It is driven by a mechanism (not shown). The read information read from the recording disk 5 by the pick-up 12 passes through the RF amplifier 13 to the digital information demodulation system 14 and the analog audio demodulation system 15.
and a video demodulation system 16, respectively.
The RF amplifier 13 has a wide band of about 5KHz to 14MHz, and can reproduce PCM audio signals with a single amplifier.
It is now possible to amplify the reproduced FM audio signal and the reproduced video signal.

In the digital information demodulation system 14, a changeover switch 17 is operated depending on the type of playback disc.
This switch 17 is switched to the A side in the case of an LDD, and to the B side in the case of a CD, based on the disk information from the disk discrimination circuit 10 mentioned above. In other words, the signal processing system for the reproduced digital signal is switched between LDD playback and CD playback. When playing a CD, the reproduced RF output is PCM audio information, and this PCM audio information is processed by the equalizer 18 using MTF (Modulation Transfer
Function) Compensation is applied.

On the other hand, in the case of LDD, the reproduced RF signal is included along with FM audio information and FM video information.
PCM audio information is LPF (low pass filter)
19 and supplied to a de-emphasis circuit 20. PCM audio information is for example EFM
However, if the digital signal is directly superimposed on the FM-modulated video signal during recording, the digital component will be interfered with by the low-frequency components of the FM video signal, so the low-frequency components will be boosted. recorded. Therefore, during reproduction, the de-emphasis circuit 20 performs compensation by dropping the low-frequency components boosted during recording. As a result, the digital signal's S/
This means that N can be improved.

Note that, instead of switching the signal processing systems using the changeover switch 17, the same effect can be obtained by turning on/off the power supply to the circuits of each signal processing system.

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 the reproduced clock extraction circuit 2.
3, and this regenerated clock extraction circuit 23
Using the reproduced clock extracted in , the EFM demodulation circuit 22 demodulates the signal into a PCM digital signal.
This demodulated signal is RAM (Random Access Memory)
etc., under the control of the memory controller 25. At this time, the memory controller 25 performs writing in synchronization with the write clock which is the frequency-divided output from the frequency divider 26 of the reproduced clock.

Reading of stored information from the memory 24 is performed using a PLL.
VCO in (phase lock droop) circuit
(voltage controlled oscillator) 27 oscillation output to frequency divider 28
This is done in synchronization with the readout clock obtained by frequency division. concerned
The PLL circuit includes a phase comparator (P/C) 31 which has two inputs: the above-mentioned VCO 27, the frequency-divided output from the frequency divider 29 of the reproduced clock, and the frequency-divided output from the frequency divider 27 of the oscillation output of the VCO 27; When the comparison output is input, LPF (low pass filter) 32 and this
It is constituted by a changeover switch 33 that selectively supplies the output voltage of the LPF 32 and the reference voltage Vref1 to the VCO 27.

In the PLL circuit, the changeover switch 33 switches the output voltage of the LPF 32 to the a side during LDD playback, and switches the output voltage of the LPF 32 to the b side during CD playback, and sets the reference voltage Vref1 to the VCO 27 based on the discrimination result of the disk discrimination circuit 10 described above. supply to. As a result, during LDD playback, the readout clock for reading stored information from the memory 24 is phase-synchronized with the playback clock by the PLL circuit.
During CD playback, when a loop switch 59 (described later) is turned on (closed), the output of the phase comparator 31 drives the CD rotation drive spindle motor 2 through the LPF 77, so that the bias of the playback clock is kept in a fixed state. The phase is synchronized to the fixed clock obtained by the VCO 27.

The digital signal read out in this way is a D/A
It is converted into an analog audio signal by the (digital/analog) converter 34, and the LPF 35L,
It becomes the left and right playback audio outputs via 35R.

The usage status in the memory 24 is constantly monitored by the memory controller 25.
When the memory 24 overflows or becomes blank (no data), the voltage generator 5 supplies information indicating these conditions to the voltage generator 36.
During LDD playback, this voltage generator 36 outputs a positive control voltage when the memory 24 overflows, and a positive control voltage when the memory 24 becomes blank, depending on information indicating the usage status of the memory 24 from the memory controller 25. Generate a negative control voltage and LPF
By superimposing it on the output voltage of 32 and supplying it to the VCO 27 via the changeover switch 33, the frequency of the read clock is controlled.

In this way, the amount of data stored in the memory 24 is constantly monitored, and when there is an excess or deficiency in the capacity and processing capacity of the memory 24, a positive or negative control voltage is generated to request the PLL circuit to take action. By doing so, the memory 24 can always be maintained in a normal state.

In analog audio demodulation system 15, playback
The outputs of BPF (bandpass filters) 37L and 37R, which pass only the 2.3MHz and 2.8MHz audio carrier components from the RF signal, are sent to the FM demodulator 3.
The signal is FM demodulated at 8L and 38R, and becomes left and right reproduced audio outputs via day emphasis circuits 39L and 39R.

In the video demodulation system 16, the reproduced RF signal is
Only video information is extracted by the BPF & notch circuit 40. In this BPF & notch circuit 40, LDD
EFM components included in the reproduced RF signal during reproduction and
It actively removes 2.3MHz and 2.8MHz audio carrier components. This extracted information is supplied to the FM demodulator 42 via the limiter circuit 41 and is FM demodulated. This demodulation output is LPF43
The regenerated RF signal is supplied to a dropout compensator (DOC) 44 via a HPF (high pass filter) 45 in the compensator 44
Dropout compensation is performed in response to the detection output of a dropout detection circuit (DOS) 46 that detects dropout based on the signal. The output of this dropout compensator 44 becomes a video output.
The output of the dropout compensator 44 is also supplied to a horizontal synchronization separation circuit 47, and a horizontal synchronization signal is separated and output. This horizontal synchronizing signal is transmitted to phase comparators 48, 4.
9 and the phase difference with 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 becomes the other input of the adder 51 via the equalizer amplifier 52. The output of the adder 51 drives the spindle motor 1 for driving the rotation of the LDD and LD via an equalizer amplifier 53 and a driver 54. This is the spindle servo system. Further, the output of the equalizer amplifier 52 drives an actuator (not shown) built into the pickup 12 via a loop switch 55, a changeover switch 56, and a driver 57. By driving this actuator, a light spot for reading information is biased in the direction tangential to the recording track of the disk. This is a tangential servo system. The actuator may be a tangential mirror that, when rotated, deflects the light spot for reading information in the direction tangential to the recording track of the disk, or a tangential mirror that deflects the lens in a direction perpendicular to the optical axis. It is also possible to have a configuration in which the information reading light spot is shifted in the tangential direction of the recording track of the disk by displacing the information.

The loop switch 55 is turned on (closed) in response to a spindle lock signal output from the spindle lock detection circuit 58 when locking of the spindle servo system is substantially completed. That is,
At the start of reproduction, the spindle motor 1 is first driven by the output of the phase comparator 48 to perform coarse adjustment of the time axis (spindle servo), and when the locking of the spindle servo is almost completed, the loop switch 55 is turned on. The actuator is turned on and the actuator is driven by the output of the phase comparator 49 to perform fine adjustment of the time axis (tangential servo). According to this, residual jitter components that cannot be removed by the spindle servo system can be removed by the tangential servo system.

However, even in the tangential servo system, the high-frequency components of the residual jitter cannot be completely removed because the mechanical system such as the actuator drive mechanism cannot sufficiently follow it.
Therefore, in the digital information demodulation system 14 mentioned above, the PLL circuit that generates the read clock is
The residual jitter component can be removed by setting the cutoff frequency of the LPF 32 lower than the maximum frequency of the band of the tangential servo loop to cut the high frequency component of the residual jitter. More preferably, the cutoff frequency of LPF32 is set to the eccentric frequency of the disk (30 in the case of LDD).
By setting the frequency lower than 8 Hz, it is possible to completely eliminate jitter caused by disk eccentricity.

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

The above is the servo system when playing a video disc (LDD, LD), but when playing a CD,
Spindle servo is performed based on the output of the phase comparator 31 in the digital information demodulation system 14 mentioned above. That is, the output of the phase comparator 31 is
The spindle motor 2 for driving the CD rotation is driven via the loop switch 59 and the driver 60, which are turned on (closed) during CD playback. Conventionally,
During CD playback, the above-mentioned tangential servo was not performed, 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,
In this embodiment, the high frequency component of the time axis error signal extracted by the HPF 61 is transferred to the selector switch 56.
A servo that drives an actuator in the pickup 12 via a driver 57, that is, a tangential servo, is also employed. The changeover switch 56 is switched to the a side when reproducing an LDD or LD, and to the b side when playing a CD, based on the determination result of the disc discriminating circuit 10.

In addition, the tangential servo during CD playback is
This is done based on the divided output of the reproduced clock extracted by the reproduced clock extraction circuit 23, but
Even if this is done based on the frequency-divided output of the frame synchronization signal detected by the frame synchronization detection circuit 21, the same effect can be obtained since the frame synchronization signal and the reproduced clock are in a synchronous relationship.

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

The specific circuit configuration of the recovered clock extraction circuit 23 is shown in FIG. The phase difference signal is supplied to the VCO 66 via the LPF 67 and the changeover switch 68. As described above, a PLL circuit that generates a reproduced clock is configured.

The changeover switch 68 is normally on the a side and is set to LPF.
67 is supplied to the VCO 66, but when a command signal is output from the control command circuit 64 mentioned above, the circuit switches to the b side in response to this command signal and supplies a predetermined reference voltage Vref2 to the VCO 66. That is, when the spindle servo is not in the locked state or when the information reading optical spot jumps track due to a random access command such as scan, search, jump, etc., the reference voltage Vref2 is applied to the VCO 66 to reproduce its oscillation frequency. By fixing it to a value close to the clock frequency,
This makes it possible to hasten the lock-in of the regenerated clock after the spindle servo is locked or after the random access command is released.

Referring again to Figure 2, the audio output section has the following:
A pair of left and right output terminals 73L, 73R for an analog audio output system and a pair of left and right output terminals 74L, 74R for a digital output system are provided.
Audio output from the analog audio demodulation system 14 is supplied to the output terminals 73L and 73R.
This audio output is also supplied to output terminals 74L and 74R via a changeover switch 75 during LD reproduction. The changeover switch 75 is placed on the a side in a normal state during, for example, LD playback, and is switched to the b side based on the disk discrimination information from the disk discrimination circuit 10 during LDD and CD playback. The audio output from the digital information demodulation system 14 is supplied to output terminals 74L, 74R via left and right mode changeover switches 76L, 76R and changeover switch 75.

As a result, during LD playback, the output terminals 73L,
Normal audio signals are output from 73R and output terminals 74L and 74R, and when playing LDD and CD, high quality audio signals are output from output terminals 74L and 74R, and when playing LDD, normal audio signals are also output from output terminals 73L and 73R. An audio signal will be output.

The mode changeover switches 76L and 76R are provided to change over the output mode of the digital audio system audio signal in an analog stage. That is, if the audio output from the digital audio demodulation system 14 is stereophonic, the above-mentioned output mode is sufficient, but in the case of audio multiplexing, for example, the L (left) channel is Japanese and the R (right) channel is Mode change switch 7 that is in a foreign language and operates independently of each other.
Output terminals 74L, 74R by 6L, 76R
The audio output from the device can be switched to three output modes: Japanese and foreign languages, Japanese only, and foreign languages only. The mode changeover switches 76L and 76R are driven separately according to control information from an operation section (not shown).

Relays that operate independently are used as the mode changeover switches 76L and 76R. Normally, a relay with one movable contact and two fixed contacts is sufficient for signal switching, but in this embodiment, a relay with one movable contact and two extra fixed contacts is used. is used. That is, to explain the relay 76L on the L channel side as an example, there are two sets of movable contacts s11 and s21 that interlock with each other, and these two sets of movable contacts s11,
Consisting of two sets of fixed contacts s12, 13, s22, 23 provided one pair for each set of fixed contacts s21, of the two sets of fixed contacts, the two fixed contacts s1 that are the most distant from each other
2 and s23 serve as input ends for two signals (left and right audio signals), and one movable contact s11 serves as an output end. According to this, since two gaps exist between the left and right signal lines, crosstalk between the left and right signals can be reliably prevented. By increasing the number of contacts and providing more gaps, crosstalk can be reliably prevented. Of course, strokes can be more reliably prevented by increasing the number of contacts and providing more gaps.

Although not shown in the figure, a focus servo system that controls the position of the pick-up 12 relative to the disk 5 in a direction perpendicular to the disk surface;
Of course, a tracking servo system is also provided to control the position of the pickup 12 in the disk radial direction, and these servo systems also generate error signals during video disk (LDD, LD) playback and digital audio disk (CD) playback. It is preferable to switch the signal processing system of
Good servo can be performed regardless of the type of disk being played back.

Furthermore, the digital signals recorded on CDs or LDDs include not only audio information but also digitized image information, control information for computer control, and the like.

By the way, in a reproducing apparatus for reproducing recorded information, a dropout compensating device for detecting and compensating for so-called dropout is essential in order to obtain a good reproduced video signal.
Here, especially when considering LDD playback, since the EFM signal is superimposed on the FM video signal, the relative level of the video signal input to the dropout detection circuit is determined by the signal in the lower band than the video band containing the EFM component. If it is not relatively high,
There is a risk that the low frequency components of the EFM signal, especially the frame sync frequency of 7.35KHz, may become noise and cause false detection of dropouts. Therefore, conventionally HPF
Dropout detection is performed based on the reproduced RF signal from which low-frequency components including EFM components have been removed by 45. However, if the low-frequency components are completely removed by the HPF, the DC energy of the entire video information signal will decrease, so the DC component of the dropout will also decrease, resulting in a problem that the dropout may not be detected. There is.

Summary of the invention The present invention has been made in view of the above points, and
It is an object of the present invention to provide a recorded information reproducing device having a dropout compensation function that enables accurate dropout compensation and noise reduction with a simple circuit configuration.

A recorded information reproducing apparatus according to the present invention includes a day emphasis circuit that compensates for the low frequency range of a digital signal contained in a read signal from a recording medium, and
digital information demodulation means for demodulating the digital signal passed through the emphasis circuit; video demodulation means for demodulating the video signal passed through the day emphasis circuit; detection means for detecting dropout based on the output of the day emphasis circuit; The present invention is characterized by comprising compensation means for compensating for dropout at the output of the video restoration means in response to the detection output of the detection means.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 5 shows the configuration of a recorded information reproducing apparatus according to the present invention.

In the figure, the day emphasis circuit 2 in the digital information demodulation system 14 in FIG.
Playback after the low range of the digital signal has been compensated for at 0
The input is an RF signal. Therefore, in the digital demodulation system 14, the LPF 19 is connected after the de-emphasis circuit 20.

Further, functional blocks having the same functions as those in FIG. 2 are given the same reference numerals.

In FIG. 5, the day emphasis circuit 20
The reproduced RF signal that has passed through is sent to the dropout detection circuit 4.
6 and BPF & notch circuit 40.

The day emphasis circuit 20 has a day emphasis characteristic as shown in FIG. 6, and functions to suppress the low frequency component of the EFM signal contained in the reproduced RF signal as described above. This allows playback RF
The relative levels of the video components in the signal are
It will be even higher than the EFM component. f1 and f2 in Fig. 6 are 1/2f1=5μsec, 1/
2f2=318nsec is selected.

In the dropout detection circuit 46, the dropout detection circuit 46
The reproduced RF signal that has passed through the emphasis circuit 20 is amplitude limited by a limiter amplifier 80, and then amplified and converted into a pulse train signal. That is, when the signal level of the reproduced RF signal is higher than a predetermined level, the limiter amplifier 80 outputs a signal whose signal level is limited to the predetermined level. Therefore, if a state in which the reproduced RF signal repeatedly exceeds the predetermined level and then drops below the predetermined level again occurs, the limiter amplifier 80 outputs a train of pulse signals. This pulse train signal becomes one input of the multiplier 81 and, after being delayed by the delay circuit 82, becomes the other input of the multiplier 81. With the configuration of the delay circuit 82 and the multiplier 81, level change points of each pulse signal of the above-mentioned pulse train signal are detected and supplied to a time constant circuit 83 consisting of an integrating circuit or the like. The output voltage of the time constant circuit 83 is compared with a predetermined reference voltage in a comparator 84, and when the output voltage exceeds the reference voltage, the comparator 84 outputs, for example, a high level signal, which becomes a dropout detection signal.

In other words, in a state where there is no dropout, the reproduced RF signal always changes its amplitude within a predetermined period, so the generation period of the pulse signal output from the limiter amplifier 80 is also limited to within this predetermined period. becomes. Therefore, the time constant circuit 83 consisting of an integrating circuit or the like repeats charging and discharging, charging when the pulse signal generated within the predetermined period is at a low level, and discharging when the pulse signal is at a high level. At this time, the output voltage of the time constant circuit 83 does not exceed the reference voltage of the comparator 84 due to the discharge that occurs within this predetermined period.

Here, if a dropout occurs in the reproduced RF signal, no amplitude change occurs in the reproduced RF signal itself, so the limiter amplifier 80 outputs the DC low level signal obtained at the time of dropout as it is. Therefore, since the time constant circuit 83 is supplied with this DC low level signal, only charging continues, and its output voltage exceeds the above-mentioned reference voltage. Therefore, dropout is detected by comparing and determining at the comparator 84 whether or not the output voltage of the time constant circuit 83 exceeds the above-mentioned reference voltage.

This dropout detection signal is supplied to a correction command generation circuit 85. The correction command generation circuit 85 is
It is configured to generate a correction command signal that exists for a predetermined period of time longer than the dropout detection signal from the point in time when the dropout detection signal is generated. This correction command signal becomes a control input to the selector 86 of the dropout compensator 44.

In the dropout compensator 44, the demodulated video signal that has passed through the LPF 43 is directly applied to one input terminal of the selector 86. Also, selector 8
A demodulated video signal that has passed through a 1H (one horizontal synchronization period) delay circuit 87 is applied to the other input terminal of the signal generator 6.
This selector 86 is configured to selectively output the demodulated video signal that has passed through the 1H delay circuit 87 when the correction command signal is generated, and selectively output the demodulated video signal that is directly supplied when the correction command signal disappears. It is configured.

When considering LDD playback, the EFM signal is superimposed on the FM video signal in the playback RF signal, so if dropout detection is performed directly from the playback RF signal, the dropout contained in the low frequency component of the EFM signal will be detected. There is a risk that the frame sync signal may be erroneously detected as a dropout.

However, in the present invention, since the dropout detection circuit 20 performs dropout detection based on the reproduced RF signal in which the low frequency components of the EFM signal are suppressed, the dropout detection circuit 46 detects the dropout caused by the EFM component. This eliminates false positive detections. This enables accurate dropout compensation and reduces noise in the reproduced video signal. Moreover, since the de-emphasis circuit 20 is essential to the digital information demodulation system 14, by using this circuit also, it can be realized without adding a new circuit, and the cost will not increase.

Note that if the low-frequency components including the EFM components are completely removed, the DC energy of the entire video information signal will decrease, which may even result in undetected dropouts, so it is preferable to attenuate the signal level of the EFM signal. It is.

Effects of the Invention As explained above, according to the recorded information reproducing apparatus according to the present invention, the day emphasis circuit
Dropout detection is performed based on the reproduced RF signal with the low frequency components of the EFM signal suppressed, which eliminates the false detection of dropouts caused by EFM components and reduces the DC energy of the entire video information signal. This eliminates undetected dropouts, which makes it possible to perform accurate dropout compensation and reduce noise in the reproduced video signal. Moreover, since the de-emphasis circuit is essential for the digital information demodulation system, by using this circuit also, it can be realized without adding a new circuit, and the cost will not increase.

[Brief explanation of the drawing]

Figure 1 shows the frequency modulated video signal and audio signal, respectively, and the analog signal.
A diagram showing the frequency spectrum of an RF signal obtained from a recording disk recorded by superimposing a PCM-modulated pulsed signal. Figure 2 is a block diagram showing the configuration of a conventional recorded information reproducing device. 3
FIG. 4 is a block diagram showing a specific circuit configuration of the disk discriminating circuit in FIG. 2, FIG. 4 is a block diagram showing a specific circuit configuration of the recovered clock extraction circuit in FIG. 2, and FIG. A block diagram showing the configuration of the recorded information reproducing device, FIG.
It is a figure which shows the de-emphasis characteristic of the de-emphasis circuit in a figure. Explanation of symbols of main parts, 1...Spindle motor for LD, LDD, 2...Spindle motor for CD,
5... Recording disk, 10... Disc discrimination circuit, 12... Pickup, 14... Digital information demodulation system, 15... Analog audio demodulation system, 16... Video demodulation system, 22... EFM demodulation circuit, 23... ...Regenerated 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 recorded information reproducing device that reproduces recorded information of a recording medium in which a video signal and an audio signal are respectively recorded by superimposing a predetermined modulated signal and a predetermined digital signal, wherein a read signal from the recording medium is a day emphasis circuit that compensates for the low frequency range of the included digital signal; digital information demodulation means that demodulates the digital signal that has passed through the day emphasis circuit; and video demodulation means that demodulates the video signal that has passed through the day emphasis circuit. , comprising a detection means for detecting dropout based on the output of the day emphasis circuit, and a compensation means for compensating for dropout at the output of the video demodulation means in response to the detection output of the detection means. Recorded information reproducing device.