JPS5892178A - Time axis corrector - Google Patents

Abstract

PURPOSE:To prevent the deterioration in picture quality in advance due to the time axis correction, by counting a horizontal synchronizing signal in one frame period of a still picture and performing the time axis correction only when the count value is between predetermined maximum and minimum values. CONSTITUTION:A counter 16a of a reproducing signal discriminating circuit 16 counts an output of a reproducing horizontal synchronizing separation circuit for one revolution of a disc motor, and only when the count value during one revolution is between predetermined maximum and minimum values, a switch is closed to form a feedback loop of time axis correction to attain the correction. In this case, a Q output of a retriggerable monostable multivibrator 16d and Q' output of a 16e turn to H level and an output of an AND gate 16f turns to H level. When the count value is smaller than the minimum value, the Q output of the 16d turns to L level, and when more than the maximum value, the Q' output of the 16e turns to L level and the output of the gate 16f turns to L level.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a means for correcting time axis errors in reproduced signals caused by eccentricity caused by replacing the disk and steady phase fluctuations of the disk in a disk reproducing apparatus. It is.

Generally, the tit smell when playing a recorded disc is
C, due to the shift in the center of rotation of the disk during recording and playback, the reproduced signal causes time axis fluctuations in disk rotation-wave number. Using FIG. 1, the movement of the CC time axis will be explained below.

As shown in FIG. 1 (!I), it is assumed that a signal is recorded in a circle with radius r centered at ty (C,). Next, as shown in FIG. 1(b), when the disk is rotating around a point (C1) that is a distance of 1 from the point (Co), when a track that has already been recorded is played back, the playback and The relative velocity between the rad and the recording track is determined by the eccentricity l, i! of the rotational wave number component of the disk motor. ! , giving rise to dark electricity. That is, if the angular velocity of the disk motor is ω, the maximum value of the relative velocity 1V between the playback/rolling and recording tracks is (r
+1)ω, and the minimum value is (r-1)ω.

Due to this variation in relative speed, the time axis of the signal during C reproduction will vary with respect to the time axis of the recorded signal.

FIG. 2 shows a block diagram of a specific example of time axis correction by driving the optical system in the optical disc described above. (1)
is a disk, (2) is a disk motor, and (3) is a tracking mirror for performing a known tracking servo. Tracking mirror (3) centered on Suke (8a)
When rotated, the light beam (a) moves radially across the disk 4st. (4) is a mirror for time axis correction, hereinafter referred to as a TBC mirror.

When the TBC mirror (4) is rotated about the axis (4a), the light beam (a) moves on the disk (1) in the track tangential direction. (5) is the objective lens, and the light beam (a)
Narrow it down. Then, c1 is controlled by a known focus servo so that the position of the narrowly focused beam is on the surface t. Neither the tracking servo nor the focus servo are directly related to the present invention, so they will not be discussed further. (6) is the 11 reflected light (
The signal recorded on the disc from b) is reproduced and amplified. (1) is a separation circuit that extracts the horizontal synchronization signal from the reproduced signal. (8) is a reference horizontal synchronization signal generation circuit, (9
) is a circuit that creates a sawtooth wave synchronized with the reference horizontal synchronization signal generated in the circuit (8).

2) is a sample and hold circuit, into which the sawtooth wave is input, and the output of the reproduction horizontal synchronizing signal separation circuit (7) is shaped into a constant width pulse by the pulse shaping circuit Ql, and the output is used as a sample pulse. is sampled and held, and this sampled and held signal is outputted as a phase comparison output. (b) is a phase compensation filter for compensating the phase of the servo system. (I is a drive circuit that drives the TBC mirror (4) with the output of the phase compensation filter @.
6) 17) +8) +*) A ``C field pack loop'' is formed by the (2) (2) heating (4), and a time axis correction force is performed. Specifically, a signal corresponding to the phase of the reference horizontal synchronization signal and the reproduced horizontal synchronization signal is output from the sample and hold circuit μQ, and this output signal is sent to the TBC.
By adding to the ξ error (4), the optical beam (Jl) on the C disk drive 1 is moved in the track direction so that the phase of the C reproduction horizontal synchronization signal always has a constant relationship with the phase of the reference horizontal synchronization signal. It is controlled as follows.

If a dropout occurs in the °C1 reproduction signal in the method described above, the reproduction horizontal synchronization signal may be missing, or a false signal may appear in the song of the reproduction horizontal synchronization signal. If a pseudo signal occurs between the reproduced horizontal synchronization signals, the sample-and-hold circuit a1 samples and holds an abnormally large or small signal. This signal does not represent the phase of the reference horizontal synchronization signal and the reproduced horizontal synchronization signal, but is a pseudo signal. Generally, it is known that when a servo system is approximated as a quadratic system, the follow-up response to a step signal or a pulse signal oscillates at a constant frequency. Therefore, when a pulse-like pseudo signal is generated in the sample-and-hold circuit, driving occurs due to the follow-up response of the servo system. This vibration varies depending on the servo system, but generally ranges from several hundred Hz to several K.
Hz, and increases in proportion to the same wave number of the time axis f @ caused by eccentricity (the same wave number of the disk. Accordingly, °
Even if the vibration due to the overspeed response of the servo system generated by the C pseudo signal is small in terms of time axis fluctuation, 1iiiirfJ
At the top, it appears as a large disturbance.

In addition, if the reproduced horizontal sync signal is missing due to dropout, the sample and hold circuit continues to hold the signal sampled and held by the reproduced horizontal sync signal immediately before the missing reproduced horizontal sync signal, and A new sample and hold is carried out by the reproduced horizontal periodic signal immediately after. Therefore, lIh1lI of the C reproduction signal
The l-axis variation information decreases, and the amount of time-axis variation accumulated by the reproduced horizontal synchronizing signal immediately after the missing reproduced horizontal synchronizing signal is output from the sample hold circuit. Due to this accumulated amount of time axis fluctuation, the servo system also vibrates as described above, causing large disturbances on the screen. Further, the sample and hold circuit cannot hold accurately for a long time, and there is charging and discharging, and if the reproduced horizontal synchronization signal is lost, this becomes large and it becomes impossible to perform accurate time axis correction.

In order to solve the above-mentioned problem Me, it is necessary to perform excessive processing against dropouts of reproduced signals. Below, the commonly used dropout processing method is divided into cases where a pseudo signal is detected between horizontal synchronization signals and cases where the horizontal synchronization signal is missing, and the processing method for each case is described. .

First, a C processing method will be described using FIG. 8 when a false signal is detected in the background of the horizontal synchronization signal.

Figure 8 (- indicates the signal output after separating the horizontal synchronization signal from the reproduced image signal. As can be seen in Figure 8 (a),
Pseudo pulses (A) are generated between the horizontal synchronizing signals arranged at approximately equal intervals. To extract the horizontal synchronization signal from such a signal, as shown in (b), at the rising edge of (a), turn on a non-retriggerable mono full pulse with a pulse width slightly narrower than the horizontal synchronization signal interval. A method is used to absorb pseudo-pulses (a) that occur within the pulse width. In this way, a sample pulse as shown in (c) from which the influence of the pseudo pulse (a) has been removed can be obtained. This sump 7. Pa.

If you sample and hold the trapezoidal wave created from the C1 standard horizontal synchronization signal using step (C), it will be accurate.1111
An axis error signal is obtained.

Next, the case where the horizontal synchronizing signal is lost will be explained using FIG. 4 of C1. FIG. 4(a) shows a signal output in which the horizontal synchronizing signal is separated from the reproduced image signal as in FIG. 8. In 8144 (a), the horizontal synchronization signal is missing in the center. Perform the same process as in Figure 8C
Also, the sample pulse is missing as shown in (C), and the temperature is the same as in (C).
There is. At this point, a method of correcting the missing pulses may be considered, but generally there is always a time delay in correcting the missing pulses. This time delay is approximately the length of time (several n5ee to several tens of n5ee) that is to be controlled by time axis correction.
), the sample-and-hold output is subject to large fluctuations. Rather, when a sample pulse is missing, it is better not to perform sampling to reduce fluctuations in the sample-hold output. In other words, it is better to use the output as shown in FIG. 4(c) as it is as the sample pulse. However, if the sample pulse is continuous
If it is missing, the fluctuation will increase for the reasons explained below.

The C1 sample hold will be explained using FIG.

(a) is a reference horizontal synchronization signal, (b) is a sawtooth wave for phase comparison created from the reference horizontal synchronization signal (a), and (C) is a one-sample pulse created from the reproduced horizontal synchronization signal.

(dl is the sample-hold deba with the sawtooth wave (b) as input and (C) as the sample pulse. The dotted lines in (C) and (d) are the n missing sample pulses and n missing sample pulses, respectively. This is the sample hold output when there is a missing pulse. As is clear from the 5th peak, when sample pulses are missing continuously, the change in the sample hold output becomes rapid. As already mentioned, the sample hold output If the output change is too rapid, the vibration of the servo system will become noticeable on the screen, and if it is significant, it will exceed the tracking range of the time axis correction means and become C-clamped.

As is clear from the above description, depending on the state of the horizontal synchronization signal of the reproduced image, it may be better not to perform mechanical time axis correction using the TBCi ramira.

The present invention improves image quality by counting horizontal synchronization signals during a period corresponding to one frame of a still image and performing time axis correction only when the signal is between a predetermined maximum value and minimum value. The purpose of this is to prevent this from happening.

The configuration of the present invention will be explained below based on the drawings.

FIG. 6 shows a block diagram of an embodiment of the present invention, and the same signals as in FIG. 2 correspond to the explanation of FIG. 2. As already mentioned, a4 is an excessive pulse removal circuit that removes spurious pulses included in the output of the reproduced horizontal synchronization signal separation circuit (7) using a non-retriggerable monomultiply.

2) is a rotation detection circuit that generates an l pulse every time the disk motor (2) rotates. In general, the motor 12) has a reference voltage ii! The position detection signal required when applying phase control using a synchronization signal can be used. (g) counts the output (7)/fAz'X interval of (7)/fAz'X (to the rotation detection circuit), that is, the output of the reproduction horizontal synchronization signal separation 1 river (7) during the disk motor (2) (7) - times $i. This reproduced signal discrimination circuit closes the shift α only when the count value during one rotation is between a predetermined maximum value and a predetermined minimum value to form a feedback loop for correction of the °C time axis.

Playback signal discrimination [Il! A specific example of the configuration of I#1 JoIk is shown in FIG. (16aJ is a counter that inputs the output of the rotation detection circuit (to) to the reset terminal and the output of the reproduced horizontal synchronizing signal separator 1gI (1) to the clock terminal, and counts the reproduced horizontal synchronizing signal during rotation. (16b
) inputs the output of the counter (16a) and inputs the output of the C1 counter (
When the output of 16a) reaches a predetermined minimum value, the retriggerable monomulti (16d) is triggered as a decoder. (16c) is a decoder that inputs the output of the counter (16a) and triggers the J Gable Mono Multi (16e) when the output of the C column (18a) reaches a predetermined maximum value. The pulse width of the retriggerable monomulti (16d) (166) is set larger than the one rotation interval. (16f)
is an AN that outputs the logic term of the positive retriggerable monomulti (LED) alarm Q and the negative output Q of the retriggerable monomulti (16e).
This is the D gate.

When the number of pulses of the reproduced horizontal synchronization signal during one rotation is greater than or equal to the minimum value and less than the maximum value, the Q output of (16d) is H.
level, the Q output of (16e) also becomes H level, and (16
The output of f) becomes H level. - When the number of pulses of the reproducing horizontal synchronization signal during rotation is smaller than the minimum value, (16d)
When the Q output of is at L level and the number of pulses of the reproduced horizontal synchronizing signal during one rotation is greater than the maximum value, the four outputs of (16e) are at L level, and the outputs of (16f) are at L level. Judgment is made through such operations.

As described above, according to the present invention, when performing time axis correction, the screen t
This method has an advantage in that it is possible to automatically prevent time axis correction from being performed on images having a missing reproduced horizontal synchronization signal to some extent that may cause vibrations in the servo system.

Although an optical disk device has been described as an example of the configuration of the present invention, the present invention can also be used in magnetic disk devices and other disk devices. Furthermore, the signal "C" is not limited to still images, but can also be used for moving images.

[Brief explanation of drawings]

Figure 1 is a diagram explaining that eccentricity caused by disk replacement causes time axis fluctuations in the reproduced signal, Figure 2 is a block diagram of a conventional time axis correction device, and Figure 8 is a diagram showing that pseudo pulses are present in the reproduced horizontal synchronization signal. Figure 4 is a diagram explaining the removal method when the reproduced horizontal synchronizing signal is included.
A diagram explaining the influence on the sample-hold output when there is a dropout. Figure 6 shows an example of the present invention. Figure 7 shows the configuration of the reproduced signal discrimination circuit of Figure 6. FIG. 2 is a block diagram illustrating an example. +1) ,...disk, a4)...time axis correction mirror, (7)...playback horizontal synchronization signal *circuit, c8)...
・・Reference horizontal synchronization signal generation circuit, sample hold (b) m, n ・・excessive pulse removal circuit, (to)・
...Rotation detection circuit, (to)...Reproduction signal discrimination circuit, (
b) Switch agent Yoshihiro Morimoto Figure 1

Claims (1)

[Claims]! , an apparatus for reproducing still image signals recorded on a disk-shaped recording medium, comprising means for counting reproduced horizontal synchronization signals during a period corresponding to one frame of a still image, and a range in which the count value of the counting means is predetermined. When is 'C
and a means for correcting the time axis, and only when the determining means determines that the count value of the counting means is within a predetermined range 'C. A time axis correction device characterized by operating a time axis correction means. 2. Count the playback horizontal synchronization signals during disk rotation,
A patent claim characterized in that the counted value is compared with a predetermined maximum value and a predetermined minimum value, and the time opening axis correction means is operated only when the counted value is smaller than the predetermined maximum value and larger than the minimum value. The time axis correction device according to the first item.