JPS60191593A - Video disc player - Google Patents

Abstract

PURPOSE:To attain stable turning of a disc record by using a reproduced pilot signal so as to attain correction of jitter and turning control of a disc motor thereby reducing remarkably residual jitter. CONSTITUTION:The phase of a reproduced pilot signal being an output of the 2nd BPF15 is shifted by 90 deg. at a phase shift circuit 17 and used as a comparison input of the 1st phase comparator circuit 18. The circuit 18 consists of a multiplier circuit and a low pass filter and a low frequency component in a multiplication output is led as a phase comparison output. The compared output is inputted to a drive coil C of a tracking mirror T via a phase compensation circuit 20. Since a reproducing beam changes the reading position in the track direction because of residual jitter, a reproducing signal without residual jitter is led. Moreover, a reproduced pilot signal is fed to a disc servo circuit 21 so as to control the turning of a disc motor 22.

Description

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

(b) Prior Art A video disc player that reproduces a normal NTSC color signal demodulates the reproduced FM video signal and demodulates the negative side (
Horizontal synchronization (below the pedestal level) - Separates the signals and removes the thick component of the reproduced FM video signal.

However, in order to accurately detect the synchronization signal regardless of fluctuations in the video signal level or frequency characteristics of the video signal, the circuit configuration becomes complicated.

In addition, wideband video signals <27 MHz) can be transmitted using the TCI multiple sub-sampling transmission method (Dempa Shimbun, page 6, January 20, 1981, and Research Association Materials No. 127-128, published by NHK Publishing Association, June 2, 1980). When efficiently compressing the band to <BMHz (see page 4), the horizontal synchronization signal is
Naturally, it is included in the video signal level range, so when playing a video disc record recorded by FM modulating this band-compressed high-quality video signal, a more complicated circuit configuration is required to achieve accurate synchronization separation. It is predicted that

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, horizontal synchronization 1δ (15, 75, 11
Since jitter correction is performed at 1.6KHz (equivalent to
Only jitter below can be removed and residual chic is 16nsec
It is only below. However, even if a residual jitter of 16 nSe ((16 times the ideal) occurs, there is apparently no problem with the reproduced screen. Note that the residual jitter with respect to the jitter frequency to be removed changes at a rate of -6 dB.

On the other hand, in the case of a high-definition video signal, it is said that the residual thick must be limited to 2n5ec or less because the information band is wide. Therefore, horizontal synchronization 1δ in high-quality video signal
Even if the signal (33,75KH7) is separated using a complicated synchronous separation circuit, the jitter frequency that can be removed is 3K.
Hz or less, and it has been confirmed that the residual jitter is also 41 seconds or more, and it has become necessary to detect jitter preferably at a period less than or equal to the horizontal synchronization period.

However, if the horizontal synchronization signal is not separated, there is no way to detect the rotation of the disk motor.

Particularly when reproducing a disk record in which video signals are recorded at a constant linear velocity, the rotation detection output of the disk motor cannot be used, making it impossible to control the rotation of the disk motor.

(C) Purpose of the Invention Therefore, the present invention has the objective of significantly reducing the amount of residual sick by detecting jitter at intervals shorter than the horizontal synchronization period.
This invention proposes a video disc player that stabilizes the rotation of disc records.

(2) Structure of the Invention The present invention performs FM modulation on a wideband video signal obtained by band-compressing a high-quality video signal and then reproduces a disc record recorded with a constant frequency pyroft signal. It is characterized by realizing motor rotation control.

(E) Embodiment The present invention will be described below with reference to an illustrative embodiment. In this example, the field frequency is set to 60H2%, and the number of scanning lines is 112.
5 lines, interlace ratio 2 = 1 aspect ratio 1 to ratio 5 =
3. Luminance signal band: 20MH7, color signal band: 7
The present invention is applied to a video disc player that optically plays back 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), and each field is assembled together using a 16.20 MHz sampling clock; 8. I
A wideband video signal of OM) lz is derived.

This sampling is also called multiple subsampling, and the sampling phase is changed by 90@ each field period, and when the four fields are superimposed, the original high-quality video signal is reproduced (see the Dempa Shimbun mentioned above). ). Furthermore, the 802nese signal that precedes the time-axis compressed color signal
During the period (13 sampling clocks), the horizontal synchronization signal that shifts within the range from the black/hell of the luminance signal to the white level has been inserted, and the horizontal synchronization signal is exactly at the intermediate level between the white level and the black level. The timing when the levels match is used as the horizontal synchronization timing. Regarding audio signals, 3 lines other than 522 each field video signal line are used.
The time axis is compressed and multiplexed into 4 lines. The specific method for band compression described 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 modulation signal (hereinafter referred to as information signal) is set to 16 MHz (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 it to z, SN deterioration of the reproduced demodulated output is sufficiently prevented simply by including the first lower sideband in the recorded green band.

Also, when recording the maximum frequency of 16 MHz, considering that the maximum pitch length that can be formed is 0.5 μm,
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 150 m for a video disk record with a constant angular velocity that rotates once per frame period, the radius is 95 to 15 m.
0nn is the recordable range, and 1.61JITl bi・
Approximately 19 minutes of information signals can be recorded on the /chi spiral track.

On the other hand, a video disk record with a constant linear velocity (radius 150n)
In the case of wn), when the recordable range is a radius of 55 to 150111 m, approximately 36 minutes of information signals are recorded on a spiral track with a pitch of 1.61 Jm.

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

First, it is necessary to select a pilot signal frequency that is not affected by unnecessary disturbances during reproduction. Unwanted disturbances have been confirmed to be caused by tracking control and focus control, and by scratches and dust on the disc. The maximum frequency of tracking control and focus control has reached more than 10 KHz, and the harmonics of the reproduction fluctuation component caused by these controls are approximately 100 KHz.
It has been confirmed that there will be a substantial impact in the near future. It has also been confirmed that harmonic components due to scratches and dust on disc records have a substantial effect up to nearly 100 KHz. Therefore, the pilot number 48 frequency is FM
Regardless of the modulation band, 1oOKHz must be selected.

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 sometimes reaches 14 MHz or less, and that the first lower sideband also reaches around 4 M)lz. Therefore, when a pilot signal of 2 MHz or more is superimposed, noise can be observed during reproduction, although only slightly, because the first harmonic component of the pilot signal caused by recording distortion overlaps with the first lower sideband. 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, the frequency of the pilot signal needs to be set to a value north of 100 KHz and less than half of 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 must be -29 dB or less relative to the information credibility level.

Furthermore, the pilot signal produces a beat of vertical stripes that are selected to be multiples of the horizontal synchronization period. This beat can be suppressed to some extent by limiting the signal level, but by selecting the frequency in an interleaved relationship with the horizontal synchronization signal, the beat can be visually eliminated. Therefore, the relationship between the pilot signal frequency 5 and the horizontal synchronization frequency 5H is Sp
= (n+'1/'2)7H (where n is a natural number), the visual beat component is removed, so there is no need to limit the pilot signal level more than necessary.

When setting the pilot signal frequency, when using a fixed oscillator output of 48.6 MHz for synchronization with a high-quality video camera, divide the frequency by 1/64 (-2") to 455N/2.
(= 759.395 + z) (the relationship between this pilot signal and information signal is shown in Figure 3), or if you use the fixed oscillation output of 64.8 MHz of the band compression encoder, you can get 256 (-2'). 155+ divided by 1/2
/2 may be used, and the cost of the video disc recorder can be reduced 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 input to the band compression (band compression).:1=da (1), and as described above, the TC According to the multiple sub-sampling transmission method, it is converted into a wideband video signal of 8. IMHz.This wideband video signal is
input to the M modulation circuit (3), and the carrier frequency shift range is 14M.
It is converted into an information signal with a frequency of Hz to 16 MHz. This information signal includes a frequency shift range and a first lower sideband of 4-17M.
The signal can be input to a first bandpass filter (4) whose passband is Hz.

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), and the waveform is shaped into a sine wave, which is then derived as a pilot signal.

The 1st bandpass output and the 10th bandpass output are the adder circuit (
7). This addition ratio is set such that the 10th bus output is -36 dB lower than the first bandpass output. The level of the addition output is limited by a limiter (8) and output to the optical modulation means (9>).

This light modulation means (9) optically polarizes the laser light emitted by the Rade light source (1 (1)), and the light led out through the polarizing plate (11) becomes intermittent light.This intermittent light is well-known. Recording pits are formed by condensing light onto the record disc (D) through the optical system (12) of the video disc player. When (D) is rotated 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>).
In addition, when rotating at a constant linear velocity, the recording position is
Rotation control is possible by combining a recording position detection mechanism that detects on the order of Jr or less and a rotation control mechanism of the disk motor (M>).

A video disc player that uses the disc record recorded in this manner as a master disc and plays back a duplicate disc record is equipped with at least the circuit shown in FIG. 1.

The reproduced signal 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 and a selected frequency 15/
25H is input to the second bandpass filter (15).

The reproduced information signal, which is the output of the bypass filter, is input to the FM demodulation circuit, converted to a wideband video signal, and then
The signal is input to a band compression decoder attached to a high-definition television receiver. 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 and sound is input to a high-definition television receiver.

The reproduced pilot signal, which is the second bandpass output, has its phase shifted by 90° in the phase shift circuit (17), and is then input as a comparison input to the first comparison circuit (18). The reference input of this first comparison circuit (18) is a fixed oscillator (
19) is input. , - fixed oscillator (19)
emits a stable reference signal of 25.3.125KHz (= 1558/2). The first phase comparison circuit (1B)
consists of a multiplication circuit and a low-pass filter, and the low-frequency component in the multiplication output is derived as a phase comparison output. This phase comparison output is input to the drive coil (20) of the tracking mirror (T) via the phase compensation circuit 20). Therefore, since the reproduction beam changes the reading position l in the track direction according to the jitter, a reproduced reproduction information signal with almost no residual jitter can be guided and output.

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, a variable delay circuit such as COD (electrical correction means) may be used. The circuit may be installed after the amplifier (13) or after the FM demodulation circuit (16) to mainly remove high-frequency jitter. Furthermore, as a method to easily perform electrical correction, two stages of sample and hold circuits are connected continuously to the signal line, and the sample and hold circuit in the first stage is operated with a constant clock, and the sample bold timing (i.e., the phase of the clock) in the second stage is adjusted. Small residual jitter correction is possible even if the jitter is weighted and rolled.

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.

In order to compensate for dropouts, the reproduced pilot signal is input to the AFC circuit (23) and then input to the first frequency dividing circuit (24). On the other hand, the reference signal is input to the second frequency dividing circuit (25). Both divisions (24) (2)
In '5), the frequency division value is set to 1715, and the rotation detection signal and the reference signal are input 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 the very least. The output must be set below 20K)Iz.

However, it should be noted that the low frequency component obtained from the first phase comparison circuit (18) can be used as a control signal for the auxiliary disk motor (22) (even if it is -1).

(f) Effects of the Invention According to the present invention, it is possible to realize thick correction and disk motor rotation control with a simple circuit configuration without detecting the horizontal synchronization signal of a wideband video signal, and the effect can be achieved by a dog. be.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of the main part of a video disc player showing an embodiment of the present invention, FIG. 2 is a solo diagram of the main part of the video disc recorder, and FIG. 3 is a diagram illustrating the frequency characteristics of the video disc recorder. Explanation of main figure numbers (D>... Video disc record, (22)...
...Disc motor, (21)...Disc servo. Applicant Japan Broadcasting Corporation Applicant Sanyo Electric Co., Ltd. Agent Patent Attorney Shizuo Sano Figure 1 ↓ Figure 2 Two Forces 1 Army 0 Figure 8 Exit Continued from page 1 0 Inventor Hidetaka Kokubun [phase] Inventor Ishii Yasuhiro [Phase] Inventor Takeo Toyama @ Inventor Mori 1) Yoshihiko

Claims (1)

[Claims] (1) A wide band obtained by time-axis multiplexing only the color components of a high-quality video signal within the horizontal blanking period and sampling the multiplexed signal using sampling/curse that shifts the phase by 90 @ for each field. The information signal and the pilot signal are reproduced from 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 lower than the information signal band. The reproduction pilot signal is input to a sync detection circuit to detect a jitter component and actuate a sick correction means, and the reproduction pilot signal is input to a disk servo circuit to rotate the disk record at a constant speed. video disc player. (2) The frequency 5 of the pilot signal and the horizontal synchronization frequency 5H have the following relationship: 5e = < n + 1/2) 5+ (where n is a natural number) video disc player.