JPS60191589A - Video disc record - Google Patents

Abstract

PURPOSE:To detect jitter at an optional period by recording superimposingly a pilot signal of a constant frequency on a disc record to an information signal formed through FM modulation of a broad band video signal. CONSTITUTION:A high definition video signal is inputted to a band compression encoder 1 and converted into a broad band video signal in 8.1MHz by using a clock lead by a fixed oscillation circuit 2 in 64.8MHz. The video signal is inputted to an FM modulation circuit 3. The video signal is inputted to an FM modulation circuit 3, the carrier frequency shift region is converted into an information signal having 14-16MHz carrier frequency region, and inputted to the 1st band pass filter 4 taking the frequency shift region and the 1st lower side band in 4-17MHz as the pass band. On the other hand, a 1/256 frequency division circuit 5 inputting the clock signal leads out the frequency division output of 15fH/2 (fH is horizontal synchronizing frequency). This frequency division output is inputted to a low pass filter 6, waveform-shaped into a sinusoidal wave and led out as a pilot signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a video disc record suitable for reproducing wideband video signals.

(Example) Conventional technology A video disc player that reproduces a normal NTSC color signal demodulates the reproduced FM video signal and uses the negative side (
The horizontal synchronizing signal below the pedestal level is separated to remove thick components from the reproduced FM video signal.

However, in order to accurately detect the synchronization signal, which is related to fluctuations in the video signal level and frequency characteristics of the video signal, the circuit configuration becomes complicated.

In addition, wideband video signals (27 MHz> (See page 128) to efficiently compress the band to <8 MHz, the horizontal synchronization signal is naturally included in the video signal level range, so the video recorded by FM modulating this band-compressed high-quality video signal. When reproducing a disc reflex code, it is expected that a more complicated circuit configuration will be required to achieve accurate synchronization separation.

Furthermore, the ideal residual jitter in a normal NTSC color video signal is 10 nsec or less, and for this purpose it is necessary to remove jitter of 2 kHz or less. Therefore, at present, sick correction is performed at the horizontal synchronization period (equivalent to 15.7! KFlz), so that only jitter of 1.6 KHz or less can be removed, and the residual jitter is only 16 nsec or less. However, 16nsec (ideal 1
．． Even if a residual jitter of 6 times) occurs, there appears to be no division on the playback screen. Note that the residual jitter with respect to the jitter frequency that can be completely removed changes at a rate of -6 dB.

On the other hand, in the case of high-definition video (iN), it is said that the residual thick must be limited to 2n5ec or less because the information band is wide. Therefore, the horizontal synchronization signal (33,75KIIZ ) is separated using a complicated synchronous separation circuit, the jitter frequency that can be removed is 3.
KHz or less, and it has been confirmed that the residual jitter is also 4n5ec or more, and it has become necessary to detect jitter preferably at a period less than or equal to the horizontal synchronization period.

(c) Purpose of the Invention Therefore, the present invention proposes a video disc record that detects jitter at an arbitrary period.

(D) Structure of the Invention The present invention is characterized in that a constant frequency pilot signal is superimposed and recorded on a disk record with respect to an information signal obtained by FM modulating a wideband video signal obtained by band-compressing a high-quality video signal.

(E) Embodiment The present invention will be described below with reference to an illustrative embodiment. In this example, the field frequency is 60Hz and the number of scanning lines is 112.
5 trees, interlacing ratio 2:1 aspect ratio 5=3
, luminance signal band 20MHz, color signal band 7M
The present invention is applied to a video disc player that optically reproduces a video disc record in which an 8 MHz wideband video signal obtained by inputting an 8 MHz high-quality video signal to a band compression encoder is FM-modulated recorded.

The band compression encoder multiplexes (TC
I method), each field is sampled using a 16.20MHz sampling clock, and an 8.10MHz
A wideband video signal of z is derived.

This sampling is also called multiple subsampling, and the sampling phase is changed by 90'' in each field period, and when the four fields are superimposed, the original high-quality video signal is reproduced (see the Denpa Shimbun mentioned above). .Furthermore, 802nese (
During the period of 13 sampling clocks), a horizontal synchronization signal that shifts within the range from the black level to the white level of the luminance signal is inserted, and the horizontal synchronization signal level exactly matches the intermediate level between the white level and black level. The timing is used as the horizontal synchronization timing. Note that the audio signal is time-base compressed and multiplexed onto 34 lines other than the 522 lines of each field video signal. The specific method for band compression mentioned above is not directly related to the gist of the present invention, so further explanation will be omitted.

In this embodiment, a wideband video signal (8.02 MHz>) including a horizontal synchronizing signal within the range of the video signal level is FM-modulated and recorded on a disc record.

The maximum frequency of this FM modulated signal (hereinafter referred to as information signal) is set to 16 MB, z (twice that of the wideband video signal) to prevent moiré.

Furthermore, this information signal has a carrier frequency shift range of 14 to 16 MHz.
By setting z, SN deterioration of the reproduced demodulated output can be sufficiently prevented simply by including the first lower sideband in the recording band.

Further, when recording at a maximum frequency of 16 MHz, taking into account that the maximum pitch length that can be formed is Q, 51 m, the recording speed must be at least 16 m/sec.

In this example, the lower limit of the recording speed is set to 18 m, taking into account changes in pit duty due to pilot signal multiplexing, which will be described later.
/sec.

Therefore, in the case of a radius of 15011111 for a video disc record with a constant angular velocity that rotates once per frame period, the radius is 9
The recordable range is 5-150m, 1.61jIT
Approximately 19 minutes of information signals are recorded on an l-pitch spiral track.

On the other hand, a video disk record with a constant linear velocity (radius of 150 m)
), when the recordable range is 55 to 150 m in radius, approximately 36
Record minute information signals.

Furthermore, in this embodiment, a continuous constant frequency pilot signal is superimposed on the information signal.

The L's pilot signal frequency must be selected to be a frequency that will not be affected by unnecessary disturbances during reproduction. Unwanted disturbances have been confirmed to be caused by tracking control and focus control, as well as by scratches on the disc and dust. 1- The maximum frequency of rack control and focus control has reached more than 10 KHz, and the harmonics of the reproduction fluctuation component caused by these controls are about 100 KHz.
It has been confirmed that there is a substantial effect up to frequencies near KHz. Furthermore, it has been confirmed that harmonic components caused by kisses and dust on a music record have a substantial effect up to nearly 100 KHz. Therefore, the pilot signal frequency is F
M modulation band (must be selected at 100 KHz or higher).

In addition, in the case of this embodiment, the first lower sideband of the information signal to be recorded is theoretically between 6 MHz and 14 MHz, but in reality, the frequency changes following the rapid change in the pre-emphasized brightness level. It has been confirmed that the shift range may reach 14 MHz or less, and the first lower sideband may also reach around 4 MHz. Therefore, when a pilot signal of 2 MH2 or more is superimposed, noise is observed during reproduction because the first harmonic component of the pilot signal caused by recording distortion overlaps with the first lower sideband, although it is slight. Therefore, the pilot signal needs to be selected to be 172 or below the lower limit frequency of the first lower sideband.

Therefore, in the end, it is necessary to set the frequency of the pilot signal to be 100KH2 or more, but not more than half the lower limit frequency of the first lower sideband.

However, even if the above conditions are satisfied, it is necessary to limit the level to such a level that harmonics higher than the second harmonic can be ignored when they reach the first lower sideband, and to do so, the pilot signal level must be It is necessary to keep it below -29CIB with respect to the signal level.

In momme, the pilot signal produces a vertical striped beat that is selected to multiply the horizontal synchronization period.This beat can be suppressed to some extent by limiting the pilot signal level, but if its frequency is selected in an interleaved relationship with the horizontal synchronization signal, Ba,
Beats can be visually resolved. Therefore, the relationship between the pilot signal frequency 5 and the horizontal synchronization frequency 5H is '
rr = (n+1/2), ++ (where n is a natural number) Since the visual Be-1 component can be removed, there is no need to limit the pilot signal level more than necessary.

When setting the pilot signal frequency, when using the fixed oscillator output 48.6MHz for high-quality video camera synchronization, divide the frequency by 1/64 (-2") to 45.5□/2.
(= 759.395Khz) (the relationship between this pilot signal and information signal is shown in Fig. 3), and the fixed oscillation output 64. ．． 8MIIz
If you use
It is preferable to use H/2, and it is possible to reduce the cost of the video disc recorder compared to the case where a fixed oscillation circuit having a unique oscillation frequency is separately provided for frequency division.

The recording operation of this embodiment will be explained below with reference to FIG.

In this embodiment, a high-quality video signal is processed using a band compression encoder (1
), and as described above, using the clock derived by the 64.8 MHz fixed oscillation circuit (2), the process is performed according to the TCI multiple sub-sampling transmission method.8. It is converted to an IHz wideband video signal. This wideband video signal is input to the FM modulation circuit 3), and the carrier frequency shift range is 14MHz to 16MHz.
M) Convert to an information signal of lz. This information signal is
The signal is input to a first bandpass filter <4) whose passband μ is 4 to 17MHz including the frequency shift range and the first lower sideband.

On the other hand, the 1/256 frequency divider circuit (5) that inputs the clock signal
derives a frequency divided output of 155H/2. This frequency-divided output is input to a low-pass filter (6), shaped into a sine wave, and derived as a pilot signal.

The 1st bandpass output and the 10th bus output are connected to the adder circuit (
7). This addition ratio is set so that the 10th-pass output is -36 dB lower than the first band-pass output. The level of the addition output beam is limited by a beam control (8) and inputted to a light modulation means (9).

This light modulation means (9) optically polarizes the laser light emitted by the laser light source (10), and the light that is completely led out through the polarizing plate (11) becomes intermittent light. Recording pits are formed by condensing light onto the record disc (D) through the video disc recorder (12).The video disc recorder is larger and more precise than the player, and is When rotating D) at a constant angular velocity, the rotation can be controlled by a rotation detection mechanism and a rotation control mechanism provided in the disk motor (M), and when rotating at a constant linear velocity, the recording position can be controlled by I.J.
Rotation control is possible by combining a recording position detection mechanism that detects on the order of m or less and a rotation control mechanism of the disk motor (M>).

A video disk player that plays back a duplicated disk record using a disk record recorded in this manner as a master disk is equipped with at least the circuit shown in FIG.

Reproduction No. 18 optically reproduced from the pickup is amplified by an amplifier (13), and then a bypass filter (14) with a pass band of 4 MHz or more, a selection layer, and a wave number of 15.
/2f+ is input to the second bandpass filter (15).

The reproduced information signal that is the output of the bypass filter is input to the FM demodulation circuit, converted to a wideband video signal, and then
It can be input to several stages of band compression decoders in high-definition television receivers. The band compressor decoder performs the inverse function of the band compressor encoder and converts 27 MHz (20 MHz video and 7 MHz video)
A high-definition video signal of MHz (voice volume) is input to a high-definition television receiver.

The reproduced pilot signal, which is the second bandpass output, is phase-shifted by 90'' in the phase shift circuit (17) and then output as the comparison input of the first comparison circuit (18). ) is a fixed oscillator (
19) is input. This fixed oscillator <19) emits a stable reference signal of 253.125 KHz (=1558/2). The first phase comparison circuit (18) is composed of a multiplication circuit and a low-pass filter, and derives the low frequency component in the multiplication output as a phase comparison output 2. This phase comparison output passes through a phase compensation circuit (20) and is inputted to the drive coil (20) of the tracking mirror (T). Therefore, since the reproduction beam changes the reading position in the track direction in accordance with the jitter, a reproduced reproduction information signal with almost no residual jitter is derived.

In this embodiment, jitter is removed by mechanical correction means, but if the response of the tracking mirror is slow and high frequency jitter cannot be removed, it is necessary to use a variable delay circuit such as COD (electrical correction means). The high-frequency jitter may be removed by installing the circuit (means) after the amplifier (13) or after the FM demodulation circuit (16). Furthermore, as a method for easily performing electrical correction, two stages of sample and hold circuits are connected continuously to the signal line, and the sample and hold in the first stage is operated with a constant clock, and the sample and hold timing in the second stage is adjusted (i.e., the phase of the clock). Even if it is controlled according to the jitter, small residual jitter correction is possible.

In this embodiment, a reproduction pilot signal is also input to the disc servo circuit (21) to control the rotation of the disc motor (22) on the video disc player side.

The reproduced pilot signal is input to the AFC circuit (23) and then input to the first frequency dividing circuit (24) in order to compensate for dropouts. On the other hand, the reference signal is input to the second frequency dividing circuit (25). Both frequency dividing circuits (24) (25)
), the frequency division value is set to 1/15, and the rotation detection signal and the reference signal are input manually to the second phase comparison circuit (26). This phase comparison output is supplied as a rotation control signal for the disk motor (22) via the second phase compensation circuit (27).

Incidentally, the phase comparison period of the second phase comparison circuit (26) is as follows:
It is better to set it to a certain length so as to include the rotational fluctuation range of the video disc record, and it is impossible to make the phase comparison period common to the first phase comparison circuit (18) at least. The output must be set to 20KHz or less.

However, it should be noted that the low frequency component obtained from the first phase comparator circuit (18) can be used as a control signal for the auxiliary disk motor 22>.

(F) Effects of the Invention Therefore, according to the present invention, jitter correction can be realized with a simple circuit configuration without detecting the horizontal synchronization signal of a wideband video signal, and the effect is great.

[Brief explanation of the drawing]

Fig. 1 is a circuit block diagram of the main parts of a video disc player showing an embodiment of the present invention, Fig. 2 is a block diagram of the main parts of the video disc recorder, and Fig. 3 is a diagram explaining the frequency characteristics. Each is shown below. Explanation of main figure numbers (D)...Video disc record, (22)...
・Disc motor, (21)...disc servo. Applicant Sanyo Electric Co., Ltd. Agent Patent Attorney Shizuo Sano Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) Wideband obtained by time-domain multiplexing only the color components of a high-quality video signal within the horizontal blanking period and sampling the -C multiplexed signal using a sambling pulse that shifts the phase by 90'' for each field. A video disc record formed by superimposing and recording an information signal obtained by FM modulating a video signal and a continuous constant frequency pilot signal in a lower band than the information signal band. (2) Frequency 5 of the pilot signal. 2. The video disc record according to claim 1, wherein b = (n + 1/2) 5+ [where n is a natural number].