JPH0633576Y2 - Information signal reproducing device - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention removes noise components that fall into the PCM signal band from the FM video signal when the disk is created when playing the disk in which the PCM signal is multiplexed with the FM video signal. The present invention relates to a video disc reproducing apparatus with a PCM signal.

[Technical background of the invention]

FIG. 4 is a block diagram showing the structure of a conventional video disk reproducing apparatus. In FIG. 4, a pickup 1 for reading a signal from the disk D, a preamplifier 2 for amplifying the signal, a video BPF 3 (bandpass filter) for extracting an FM video signal from the output signal, and a limiter circuit for limiting the output thereof. 4 and an FM demodulator 5 for extracting a demodulated video signal from its output.

Also, a PCMLPF (low-pass filter) 6 for extracting the PCM signal from the output of the preamplifier 2 and a de-emphasis circuit 7 for applying de-emphasis after the extraction.
Then, it is composed of a PCM decoder 8 for decoding PCM.

In FIG. 4, the pick-up 1 converts the pit information into an electric signal from the disk D, and the pre-amplifier 2 amplifies the electric signal. The playback signal is divided into FM video and PCM bands by video BPF3 and PCMLPF6 respectively.

The FM video taken out by the video BPF 3 passes through the limiter 4, undergoes waveform shaping, and is demodulated into a video signal by the FM demodulator 5.

The PCM signal extracted by the PCMLPF 6 is passed through the de-emphasis circuit 7 and then demodulated by the PCM decoder 8 into voice or data.

In addition, if FM audio is included in the playback signal in addition to this, the signal can also be easily extracted by passing it through the BPF9 for FM audio.

The characteristics of video BPF3 are shown in FIG. The characteristics of PCMLPF6 are shown in FIG. The disk reproduction spectrum is shown in FIG.

[Problems of background technology]

During the disc manufacturing process, the FM video signal output from the FM modulator (not shown) is a sideband component J ₁ , J generated by the beat component of the luminance signal component and the chrominance signal component together with the luminance signal component J _{0. -1} , J ₂ , J _-2 ... A non-linear processing of a limiter (not shown) provided after the FM modulator causes a beat component between the luminance signal component and the sideband component in the FM video signal, that is, an intermodulation component. Among them, the second-order difference beat component J _-2 is J _-2 = 2J ₀ −J ₂ = 2f ₀ −
(F ₀ + 2f ₁ ) = f ₀ −2f ₁ (where J ₀ = f ₀ , f ₀ ,
f ₁ represents the luminance signal component and the color signal component respectively). A part of the intermodulation component produced by the beat of the luminance signal component and the chrominance signal component, J _-2, is recorded on the disc in a state of entering the PCM signal band.

On the other hand, when reproducing a disc on which a part of the intermodulation components are recorded as described above, the input signal of the PCMLPF in FIG. Since it is included in the demodulated signal as a matter of course, there arises a problem that the S / N of the PCM signal of the disc reproducing device is deteriorated.

[Purpose of device]

This invention was made in order to eliminate the above-mentioned conventional drawbacks, and the intermodulation of the luminance signal component and the chrominance signal component of the FM video signal mixed in the PCM signal band reproduced from the video disk with the PCM signal. The components are canceled by the phase-inverted component of the intermodulation component generated in the limiter circuit in the video disc playback device with PCM signal, and the intermodulation component mixed in the PCM signal band generated when the disc is created is removed.
It is an object of the present invention to provide a video disc reproducing device with a PCM signal, which can improve the SN of the reproduced PCM signal.

[Outline of device]

The video disc reproducing apparatus with a PCM signal of the present invention multiplexes an FM-modulated image signal and a PCM-converted signal of audio or data, and is FM-modulated from a reproduced signal from a recording medium optically recorded in the same track. The image signal is taken out by the band pass filter, the waveform is shaped by the limiter circuit, the noise component generated in this limiter circuit is extracted by the filter, and the signal which is phase-inverted by the phase inversion amplifier and the reproduced PCM signal by the reproduced signal are obtained. The signal taken out by the low-pass filter is mixed by a mixer so that the noise component in the reproduced PCM signal mixed in the recording medium at the time of recording is canceled at the time of reproducing.

[Example of device]

An embodiment of a video disc reproducing apparatus with a PCM signal of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the embodiment.
In FIG. 1, the same parts as those in FIG. The disk D is a recording medium in which an FM-modulated image signal and a signal obtained by converting voice or data into PCM are multiplexed and optically recorded in the same track.

The information recorded on the disk D is read by the pickup 1. The reproduction signal read by the pickup 1 is amplified by the preamplifier 2 and then output as the reproduction RF signal 2a. This reproduced RF signal is introduced into a video band bus filter (hereinafter referred to as video BPF), PCMLPF8 (low pass filter) and FM video signal extraction and demodulation circuit 12.

The video BPF 3 extracts the FM video signal from the reproduction RF signal 2a and outputs it to the limiter circuit 4.

The output of the limiter circuit 4 is sent to a video demodulator 5 and a band pass filter 6 (hereinafter referred to as BPF). Of these, the former video demodulator 5 demodulates the video from the output of the limiter circuit 4 to generate a demodulated video signal.
It is designed to output 5a.

The latter BPF 6 extracts the J ₂ component from the output of the limiter circuit 4 and outputs it to the phase inverting amplifier 7.

This J ₂ component is shown as J 2 in FIG. ₂ and is a component mixed in the PCM signal band among the intermodulation components of the luminance signal component and the chrominance signal component of the FM video signal.

The intermodulation component 7a is sent to the mixer 10 from the output terminal of the phase inverting amplifier 7.

On the other hand, the reproduction RF signal 2a output from the preamplifier 2 is
It is being introduced into the MLPF (Low Pass Filter) 8. The PCMLPF 8 extracts a PCM signal, and its output is output to the mixer 10 through the delay circuit 9.

The output of the mixer 10 is adapted to be taken out as a PCM signal output 13a through a PCM de-emphasis circuit.

Next, the operation of this invention will be described.

The information recorded on the disk D is photoelectrically converted by the pickup 1 and reproduced, and after being amplified by the preamplifier 2, the reproduced RF signal 2a having the disk reproduction spectrum as shown in FIG. 2 is converted into the video BPF3, PCMLPF8. , FM audio signal extraction and demodulation circuit 12.

Of these, the video BPF 3 removes the PCM signal and the FM audio signal from the reproduced RF signal 2a, extracts the FM video signal, and outputs it to the limiter circuit 4.

This limiter circuit 4 shapes the waveform of the video signal,
It is sent to the video demodulator 5, demodulated there, and the demodulated video signal 5a is output.

The output of the limiter circuit 4 is sent to the BPF 6 and the J ₂ component produced in the limiter circuit 4 is extracted. The characteristics of this BPF6 are shown in FIG.

The J ₂ component extracted by the BPF 6 is phase-inverted by the phase inverting amplifier 7, and the intermodulation component 7a is sent to the mixer 10.

On the other hand, the reproduction RF signal 2a is input to the PCMLPF8, where the PCM
The signal component is extracted, delayed by the delay circuit 9 for a predetermined time, and input to the mixer 10.

This mixer 10 reproduces the PCM signal 9 delayed by the delay circuit 9.
By mixing a and the intermodulation component whose phase is inverted by the phase inversion amplifier 7, the reproduced PCM signal 9a to the J ₂ component, that is,
The intermodulation component 7a is subtracted and output to the PCM de-emphasis circuit 13.

The PCM de-emphasis circuit 13 performs de-emphasis and outputs a PCM signal.

Here, the delay circuit 9 will be described.

The delay amount in the video BPF 3 is d ₁ , the delay amount in the limiter circuit 4 is d _2, and the delay amount in the BPF 6 and the phase inverting amplifier 7 is d ₃
And the delay amount in the PCMLPF8 is d ₄ and the delay amount in the delay circuit 9 is d ₅ , d ₁ + d ₂ + d ₃ = d ₄ + d ₅ ............ (1) If the delay amount d _{5 of} 9 is selected, the anti-phase J ₂ component produced from the FM video in front of the mixer 10 and
Since the delay amounts of the J ₂ component mixed in the reproduced PCM signal 9a match, the J ₂ component can be removed from the reproduced PCM signal 9a.

Along with this, the S / N ratio of the PCM signal is improved, and the error rate can be improved.

Further, the reproduced RF signal 2a is demodulated by the FM audio signal extraction and demodulation circuit 12 to extract the audio signal I and the audio signal II.

[Effect of device]

As described above, according to the video disc reproducing apparatus with PCM signal of the present invention, among the noise components already included in the PCM signal at the time of disc reproduction, the luminance signal component and the chrominance signal component of the FM video signal are mutually exchanged. among modulation component, it enters the playback PCM signal band, the FM video signal reproduced so-called J ₂ ingredient is passed through a Rimitsuta circuit extracts only J ₂ components by BPF, the J ₂ component contained in the reproduced PCM signal Since the phase was reversed and mixing was performed, playback after mixing
By removing the J ₂ component from PCM, the S / N ratio is improved and the PCM error rate is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the construction of an embodiment of a video disc reproducing apparatus with a PCM signal of the present invention, and FIG.
FIG. 3 is a block diagram of the BPF in the video disc reproducing apparatus with a PCM signal, FIG. 4 is a block diagram of the conventional video disc reproducing apparatus, and FIG. FIG. 6 is a characteristic diagram of the video BPF of the video disc reproducing apparatus, and FIG. 6 is a characteristic diagram of the PCMLPF of the conventional video disc reproducing apparatus. 1 …… Pickup 2 …… Preamplifier 3 …… Video BPF 4 …… Limiter circuit 5 …… Video demodulator 6 …… BPF 7 …… Phase inverting amplifier 8 …… PCMLPF 9 …… Delay circuit 10 …… Mixer 11… … PCM de-emphasis circuit 12… FM audio signal extraction and demodulation circuit D… Disk

Claims (1)

[Scope of utility model registration request] 1. Means for extracting an FM-modulated video signal from a reproduction signal of a recording medium optically recorded on the same track by multiplexing an FM-modulated video signal and a signal obtained by converting voice or data into PCM. A limiter circuit for shaping the waveform of the video signal extracted from the video signal extraction means, and an intermodulation component of the luminance component and the chrominance signal component of the FM video signal generated by the limiter circuit, within the PCM signal band Means for extracting a component mixed in the signal and inverting the phase, means for extracting a reproduced PCM signal from the reproduced signal, mixing the output of the phase inverting means and the output of the reproduced PCM signal extracting means, and reproducing the reproduced signal. An information signal reproducing apparatus comprising: a mixing unit that removes, from the PCM signal, the intermodulation component of the luminance signal component and the chrominance signal component that is mixed in the PCM band.