JPH0559609U - Optical disc player - Google Patents

Abstract

(57) [Summary] [Purpose] To eliminate the jitter of the reference signal in the audio signal system,
To provide an optical disk reproducing device which does not deteriorate the characteristics of an audio signal reproduced from an EFM signal. A sync signal detection circuit 44 for detecting the presence or absence of a sync signal in an EFM signal, a phase shifter 16 for phase comparison between the sync signal in the demodulation output of a video FM signal and the output of a voltage controlled oscillator 40, and an EFM. Sync signal in signal and reference oscillator 4
A phase comparator 29 for performing a phase comparison with the oscillation output of 0, and when the synchronization signal detection circuit 44 detects the presence of a synchronization signal, the phase comparison output of the phase comparator 29 controls the rotation of the optical disk. In addition, the oscillation frequency of the voltage controlled oscillator 40 is controlled based on the phase comparison output of the phase comparator 16, and the phase comparator 1 is detected when it is detected that there is no EFM signal.
The rotation of the optical disc is controlled by the phase comparison output of No. 6, and the oscillation frequency of the voltage controlled oscillator 40 is controlled to be constant.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an optical disc reproducing apparatus in which both video signals and audio signals are recorded.

[0002]

[Prior Art]

 As shown in FIG. 3, an optical disc on which both a video signal and an audio signal are recorded is a video FM signal FM-modulated by a decoded video signal and 2.3 MHz and an FM signal FM-modulated by an analog audio signal. A signal of 8 MHz (analog voice FM signal) and an EFM signal EFM-modulated by a digital voice signal are frequency-multiplexed and recorded.

In the conventional optical disc reproducing apparatus for reproducing the above-mentioned optical disc, the RF signal detected from the optical disc 2 by the pickup 1 is separated in the decoder 3 as shown in FIG. 4, and the analog audio FM signal is 2.3 MHz. After passing through the 2.8 MHz band-pass filters 4 and 5, the respective outputs are demodulated in the FM demodulators 6 and 7, respectively, and output.

The video FM signal separated by the decoder 3 is demodulated by the FM demodulator 8, converted into a digital signal by the A / D converter 9, and stored in the memory 10. The PLL circuit 11 detects the jitter on the time axis generated in the disk rotation system from the horizontal synchronizing signal and the burst signal in the FM demodulated reproduced video signal, and obtains a signal synchronized with the reproduced signal including those jitters. This signal is used as a write clock pulse for the memory 10.

On the other hand, the read crolock pulse from the memory 10 is the oscillation output of the reference oscillator 12 such as a crystal oscillator, and the data read from the memory 10 is converted into an analog signal by the D / A converter 13, Get a video signal output without jitter.

In controlling the rotation of the disk, the horizontal sync signal in the output of the FM demodulator 8 is separated by the sync separation circuit 14, and the separated horizontal sync signal and the output from the reference oscillator 12 are divided by the frequency divider 15. The signal is phase-compared by the phase comparator 16, the phase comparison output is passed through the low-pass filter 17, and the output of the low-pass filter 17 is supplied to the drive circuit 18 of the spindle motor 31 to control the rotation of the optical disk 2.

Therefore, the rotation of the optical disc 2 is controlled so that the horizontal synchronizing signal in the reproduced video signal is synchronized with the reference clock pulse.

The EFM signal separated by the decoder 3 is EFM demodulated by the EFM demodulator 19. A clock pulse synchronized with the EMF signal is generated by the PLL circuit 20 which receives the separated EFM signal, and the demodulated digital audio signal is stored in the memory 21 by using this clock pulse as a write clock pulse.

The oscillation output of the voltage controlled oscillator 22 is frequency-divided by the frequency divider 23, the frequency-divided output is read out, the digital audio signal stored in the memory 21 is read out as a clock pulse, and the data demodulator 24 demodulates the data. Then, the D / A converter 25 converts the analog audio signal and outputs the analog audio signal. Here, a signal obtained by dividing the oscillation output of the voltage controlled oscillator 22 by the frequency divider 26 is supplied to the D / A converter 25 as a clock pulse.

On the other hand, the synchronous signal demodulator 27 demodulates the synchronous signal in the EFM signal separated by the decoder 3, and outputs the synchronous signal and the oscillation output of the voltage controlled oscillator 22 divided by the frequency divider 28. Phase comparison is performed in the phase comparator 29, the phase comparison output is passed through the low-pass filter 30, the output signal from the low-pass filter 30 is applied to the voltage-controlled oscillator 22 as a frequency control voltage, and the oscillation frequency of the voltage-controlled oscillator 22 is controlled. Thus, the oscillation frequency of the voltage controlled oscillator 22 is synchronized with the synchronizing signal in the EFM signal.

[0011]

[Problems to be solved by the device]

 However, according to the above-described conventional optical disc reproducing apparatus, the rotation of the optical disc is controlled based on the oscillation output of the reference oscillator 12, so that the oscillation output of the voltage controlled oscillator 22 and the EFM signal are asynchronous. Therefore, in order to synchronize the oscillation output of the voltage controlled oscillator 22 with the EFM signal, a configuration including the synchronization signal demodulator 27, the frequency divider 28, the phase comparator 29, and the low pass filter 30 is required. Here, it can be said that the oscillation output of the reference oscillator 12 is a video system reference clock, and the oscillation output of the voltage controlled oscillator 22 is an audio system reference clock.

However, since the optical disc 2 is rotationally controlled so that the sync signal in the reproduced video signal is synchronized with the reference clock pulse, the jitter of the sync signal in the EFM signal is sufficiently attenuated by the output from the low-pass filter 30. Therefore, the jitter remains in the oscillation output of the voltage controlled oscillator 22. However, the oscillation output of the voltage controlled oscillator is also necessary for the D / A converter 25, and as a result of D / A conversion by the clock pulse having jitter, the D / A converted audio signal is affected by this jitter. However, there was a problem that the reproduced sound quality deteriorates.

An object of the present invention is to provide an optical disc reproducing apparatus which eliminates the jitter of the reference signal in the audio signal system and does not deteriorate the characteristics of the audio signal reproduced from the EFM signal.

[0014]

[Means for Solving the Problems]

 The optical disc reproducing apparatus of the present invention is an optical disc reproducing apparatus in which a video FM signal FM-modulated by a decoded video signal and a modulated audio signal modulated by a digital audio signal are recorded in a superposed manner. Detecting means for detecting the signal, demodulating means for demodulating the video FM signal, first phase comparing means for comparing the phase of the synchronizing signal in the demodulated output with the first reference signal, and synchronizing signal in the modulated audio signal. The second phase comparison means for performing phase comparison with the second reference signal of a constant frequency, and the phase comparison output by the second phase comparison means when the detection means detects the presence of the modulated voice signal When the rotation control is performed and the frequency of the first reference signal is controlled based on the phase comparison output of the first phase comparison means, and the detection means detects that there is no modulated audio signal, the first phase comparison is performed. It controls the rotation of the optical disk in the phase comparison output by stage, and wherein the frequency of the first reference signal and a control means for controlling the constant.

[0015]

[Action]

 According to the optical disk reproducing apparatus of the present invention, when it is detected that the modulated audio signal is present, the rotation of the optical disk is controlled by the phase comparison output by the second phase comparison means, and the phase comparison of the first phase comparison means is performed. The frequency of the first reference signal is controlled based on the output. Therefore, in this case, the rotation of the optical disc is controlled so that the synchronizing signal in the modulated audio signal has a constant frequency, the first reference signal has no jitter, and the modulated audio signal is converted into an analog audio signal. , Jitter components are not mixed in the analog audio signal output. When it is detected that there is no modulated audio signal, the rotation of the optical disk is controlled by the phase comparison output by the first phase comparison means, and the frequency of the first reference signal is controlled to be constant. Therefore, in this case, the frequency of the first reference signal is a constant frequency, and the optical disc so that the synchronization signal in the reproduced video signal is synchronized with the constant frequency of the first reference signal based on the phase comparison output of the first phase comparison means. Will be rotation controlled.

[0016]

【Example】

 Hereinafter, the present invention will be described with reference to examples. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the present embodiment, in order to avoid duplication, the same components as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted. .

In the present embodiment, a voltage controlled oscillator 40 is provided in place of the reference oscillator 12, and the oscillation output of the voltage controlled oscillator 40 is supplied to the memory 10 as a read clock pulse and supplied to the frequency divider 15 for division. Go around. The phase comparison output from the phase comparator 16 is passed through a low-pass filter 41 and is used as the other input of a switch 42 to which a fixed voltage is applied as one input, and either the fixed voltage or the output of the low-pass filter 41 is selected by the switch 42. Is applied to the voltage controlled oscillator 40 as an oscillation frequency control voltage.

Further, a reference oscillator 43 such as a crystal oscillator is provided in place of the voltage controlled oscillator 22, and the oscillation output of the reference oscillator 43 is supplied to the memory 21 as a read clock pulse and to the frequency dividers 26 and 28. And divide. On the other hand, a synchronizing signal detecting circuit 44 is provided, and the synchronizing signal detecting circuit 44 detects the synchronizing signal from the EFM signals separated by the decoder 3, and the switch 42 is switched by the detected synchronizing signal.

Furthermore, the output of the low-pass filter 17 and the output of the low-pass filter 30 are supplied to the switch 45, and the switch 45 is switched by the sync signal detected by the sync-signal detection circuit 44. One of the output and the output of the low-pass filter 30 is selected and supplied to the drive circuit 18 to control the rotation of the spindle motor 31. Other configurations are the same as those of the conventional example.

The operation of the embodiment configured as described above will be described. The optical disc 2 includes one in which the video FM signal, the analog audio FM signal, and the EFM signal are recorded together (hereinafter referred to as A optical disc), and the video FM signal and the analog audio FM signal. Some are recorded together (hereinafter referred to as B optical disk), and some are recorded together with the video FM signal and the EFM signal (hereinafter referred to as C optical disk).

During reproduction of the A optical disc and the C optical disc, the EFM signal is present in the RF signal detected by the pickup 1, the sync signal is detected by the sync signal detection circuit 44, and the switch 45 is operated by the low pass filter 30. The output is switched to the side that selects it. A phase comparator 29 compares the phase of the synchronizing signal demodulated by the synchronizing signal demodulator 27 in the EFM signal with the signal obtained by dividing the oscillation output of the reference oscillator 43, which is the reference signal of the voice system, by the frequency divider 28. The phase comparison output is supplied to the drive circuit 18 via the low pass filter 30.

Therefore, the rotation control of the A optical disc and the C optical disc is performed so that the synchronizing signal in the EFM signal has a constant frequency, the reference signal for digital audio demodulation has no jitter, and the D / A conversion of the digital audio signal is performed. At this time, the jitter component is not mixed in the analog audio signal output. At this time, the synchronization signal in the reproduced image signal demodulated by the FM demodulator 8 and the oscillation output of the voltage controlled oscillator 40 are asynchronous.

However, at this time, the switch 42 is switched to the side that selects the output of the low-pass filter 41, and the video system oscillator is the voltage-controlled oscillator 40, and the phase comparator 16 passing through the low-pass filter 41 is used. The oscillating frequency of the voltage controlled oscillator 40 is controlled by the phase comparison output of (1) to synchronize the oscillated output of the voltage controlled oscillator 40 with the synchronizing signal in the reproduced video signal. The synchronized oscillation output of the voltage controlled oscillator 40 is used as a read clock pulse of the memory 10.

When the B optical disc is reproduced, the EFM signal does not exist in the RF signal, and the rotation control of the disc 2 is performed based on the EFM signal as in the A optical disc reproduction and the C optical disc reproduction. I can't.

In this case, the sync signal detection circuit 44 determines that there is no sync signal, the switch 42 applies a fixed voltage as a frequency control voltage to the voltage controlled oscillator 40, and the voltage controlled oscillator 40 oscillates at a constant frequency. Is done. On the other hand, the switch 45 guides the output of the low-pass filter 17 to the drive circuit 18, and controls the rotation of the optical disk 2 based on the phase comparison output of the phase comparator 16 which has passed through the low-pass filter 17 to reproduce the reproduced video signal. Thus, the rotation of the optical disk 2 is controlled so that the synchronizing signal of # 1 is synchronized with the output of the voltage controlled oscillator 40 having a constant oscillation frequency.

Therefore, in the case of reproducing the B optical disc, the rotation control of the optical disc 2 is performed so that the horizontal synchronizing signal in the video signal is synchronized with the reference signal as in the conventional example.

Next, the synchronization signal detection circuit 44 is a circuit for detecting the synchronization signal in the EFM signal. Instead of the synchronization signal detection circuit 44, the RF signal is supplied to the low-pass filter 50 as shown in FIG. An output of the low-pass filter 50 is supplied to a rectification and smoothing circuit 51 to be rectified and smoothed, a smoothed output is supplied to a comparator 52, and the comparator 52 detects whether or not the EFM signal itself in the RF signal exists. May be used.

Although the above embodiment has been described with respect to the optical disc reproducing apparatus in which the audio signal and the video signal are recorded, it is further applied to the optical disc reproducing apparatus capable of reproducing the CD disc in which only the audio signal is recorded as the EFM signal. can do.

[0029]

[Effect of the device]

 As described above, according to the present invention, when the presence of the modulated audio signal is detected, the rotation of the optical disk is controlled by the phase comparison output by the second phase comparison means, and based on the phase comparison output of the first phase comparison means. Since the frequency of the first reference signal is controlled in this case, the rotation of the optical disc is controlled so that the synchronizing signal in the modulated audio signal has a constant frequency, and the first reference signal has no jitter. This has the effect of eliminating the inclusion of jitter components in the analog audio signal output when converting the modulated audio signal to the analog audio signal.

Further, when it is detected that there is no modulated audio signal, the rotation of the optical disc is controlled by the phase comparison output by the first phase comparison means, and the frequency of the first reference signal is controlled to be constant. In this case, the frequency of the first reference signal is a constant frequency, and the optical disc is rotated based on the phase comparison output of the first phase comparison means so that the synchronization signal in the reproduced video signal is synchronized with the constant frequency of the first reference signal. Has a controlled effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a circuit diagram of an EFM signal detection circuit that replaces the synchronization signal detection circuit according to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing frequency components of a detection output from a pickup according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 2 optical disk 8 FM demodulator 14 sync separation circuit 16 and 29 phase comparator 18 drive circuit 19 EFM demodulator 27 sync signal demodulator 31 spindle motor 40 voltage controlled oscillator 42 and 45 switch 43 reference oscillator 44 sync signal detection circuit

Claims (1)

[Scope of utility model registration request] 1. An optical disk reproducing apparatus in which a video FM signal FM-modulated by a decoded video signal and a modulated audio signal modulated by a digital audio signal are recorded in a superposed manner, and detection means for detecting the presence or absence of the modulated audio signal. A demodulating means for demodulating the video FM signal; a first phase comparing means for comparing the phase of the synchronizing signal in the demodulated output with the first reference signal; and a synchronizing signal in the modulated audio signal and a second of a constant frequency. The second phase comparing means for comparing the phase with the reference signal, and the second comparing means for detecting the presence of the modulated audio signal for controlling the rotation of the optical disk by the phase comparing output by the second comparing means, and The frequency of the first reference signal is controlled based on the phase comparison output of the phase comparison means, and when the detection means detects that there is no modulated audio signal, the phase comparison output by the first phase comparison means is used. An optical disc reproducing apparatus comprising: a control unit that controls the rotation of the optical disc and controls the frequency of the first reference signal to be constant.