JPS589498A - Generator of time axis error signal for reproduced signal - Google Patents

Abstract

PURPOSE:To produce forcibly a timing signal serving as a sampling pulse even in case no reproduced burst signal exists, by storing the signals corresponding to the period from the generation of a reproduced horizontal synchronizing signal to the generation of a timing signal. CONSTITUTION:The signals corresponding to the period from the generation of a horizontal synchronizing signal to the generation of a timing signal are stored in a sample holding circuit 11. Then the signal corresponding to the timing signal is forcibly produced after a period from the generation of the horizontal synchronizing signal to the generation of the output signal of the circuit 11 when a reproduced color burst signal does not exist during the period from the generation of the horizontal synchronizing signal to the generation of the timing signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time axis error signal generating device for a reproduced signal, and more particularly to a time axis error signal generating device for time axis correction of a reproduced signal of color video information.

In order to obtain a good reproduction image of color video information, a time axis correction device is necessary, and this device detects the phase difference between the reproduced color burst signal and a separately provided reference signal, such as a reference signal having the period of a horizontal synchronization signal. This method obtains time axis error information. FIG. 1 is a general block diagram of a time axis error signal generator for a reproduced signal.
A burst separation circuit 1 consisting of an MI-1z bandpass filter is provided, and this reproduced color burst signal is processed in a waveform shaping circuit 2 into a pulse-like signal waveform (])). This output (T)) is the AND gate 3
has become the sole strength of

On the other hand, a horizontal synchronization separation circuit 4 is provided to separate the horizontal synchronization signal from the reproduction signal (A), and the MMV (
A monostable multivibrator) 5 and an MMV6 triggered by the output (11) of this MMV5 are provided. This single pulse (C) of MMV6 serves as the gate input to gate 3.

Further, a trapezoidal wave synchronized with the output of the reference generating circuit 7 is generated by the trapezoidal wave generating circuit 8, and this trapezoidal wave (F) is applied to the sample hold circuit 9.

The output of the gate 3 triggers MMVlo, and in response to the generation timing of this output, the trapezoidal wave (F') is sampled in the sample hold circuit 9, and the next timing signal, the sampling signal (E ) is held until the arrival of This output becomes a time axis error signal.

Figures 2 (A) to (F) are signals (A) of each part of the circuit in Figure 1.
~(F'), and a single pulse (B) of a fixed period is generated from the MMVs in response to the generation timing of the horizontal synchronizing signal of the reproduction signal (A). Therefore, the next MMV6
(q is a gate signal of a predetermined width that is delayed for a certain period from the generation of the reproduced horizontal synchronizing signal, and the output of gate 3 is the first rising edge of the reproduced color burst output during the generation period of the gate signal (C)). Transitions in sync with the downlink. The output (E) of MMV10 rises in agreement with this transition timing. This transition timing is as follows: 3- The phase of the zero cross point at the falling edge of the color burst that first appears during the period of the gate signal (C), that is, from the generation of the horizontal synchronization signal to the specific point of the reproduced burst signal, for example, the third zero cross. This indicates the period until the point occurs. Therefore, if the output (E) of MMV10 is used as a sampling pulse, the level of the trapezoidal wave (I?) at that time indicates the phase difference between the reference signal and the reproduced color burst signal, and 1. It is what it is.

Here, since no color burst signal is inserted in the vertical retrace section of the reproduced video signal, no sampling pulse (E) is generated, and accurate time axis correction cannot be performed during that period. Therefore, methods have been proposed for detecting the absence of color bursts and generating alternative sampling pulses, but these methods have the disadvantage of being complicated in structure or lacking in reliability if a simple structure is used.

An object of the present invention is to provide a time axis error signal generating device for a reproduced signal, which has a simple configuration and is capable of forcibly generating a timing signal as a sampling pulse even in the absence of a color burst with good characteristics. be.

The time axis error signal generating device according to the present invention detects the generation timing of a predetermined point on the reproduced color burst signal waveform every reproduction horizontal synchronization signal period, generates a timing signal, and calculates the time difference between this timing signal and a reference signal. A device that generates a time axis error signal according to the time axis,
The feature is that the signal corresponding to the period from the generation of the reproduction horizontal synchronization signal to the generation of the timing signal is stored in the storage means, and the reproduction color burst signal in the period from the generation of the horizontal synchronization signal to the generation of the timing signal is stored in the storage means. The object of the present invention is to forcibly generate a signal corresponding to a timing signal after a period corresponding to the output signal of the storage means has elapsed since the generation of the reproduced horizontal synchronizing signal when the signal is not present.

The present invention will be explained below with reference to the drawings.

FIG. 3 is a circuit diagram of an embodiment of the present invention, and parts equivalent to those in FIG. 1 are designated by the same reference numerals. The difference from Fig. 1 is that the MM that generates the gate signal (C)
V-+7) A time constant circuit is composed of a resistor R11 and a capacitor C8, and the time constant signal waveform of this time constant circuit section, that is, the charging waveform which is the terminal voltage of the capacitor C1 (q is the input of the sample and hold circuit 110) This hold circuit 110 input/output signal (q, σ
A level comparator 12 for comparing the levels of -D is provided, and the output of this comparison is made available to the NA and ND gates 13. On the other hand, in order to detect the presence or absence of a color burst, a color burst detection circuit 14 is provided which receives the output (B) of the waveform shaping circuit 2 and is set by the output (B) of the MMVs, and this detection output is inverted by an inverter 15. This gate output (T) is used as the MMV 6 reset signal.

An AND gate 16 is provided which inputs a sampling pulse (E) which is a timing signal, and the detection output of the color burst detection circuit 14 serves as its input. Here, if the color burst detection circuit 14 is configured to generate a high level output when a burst exists and a low level output when a burst does not exist, the gate 16 is opened only when a burst exists. Then, the sampling signal (E) is sent to the sample and hold circuit 11. Further, only when a burst does not exist, the gate 13 is opened, and the high level signal of the comparator 12 is inverted and outputted as a low level signal, thereby operating as a reset signal (I) of the MMV6.

The other configurations are the same as those shown in FIG. 1, and their explanation will be omitted.

Figures 4 (A) to (I) are signals (5) of each part of the circuit in Figure 3.
2 is a diagram showing the waveforms of each of the signals (A) to (F') in the case where a burst signal is present, and is the same as the signals (A) to (F) in FIG. A time axis error signal is output from the sample hold circuit 9 in accordance with the time axis fluctuation of the reproduced signal at that time. Since the gate 16 is open at this time, the sampling pulse (E) of MMV 1o becomes the sampling pulse of another sample-and-hold circuit 11, and the ramp signal (integral) waveform (of q) by the MMV 60 time constant circuit at that point in time is The level is sampled and stored. This ramped signal (q is 7- a predetermined time constant C
, R, , so the level of the signal (q) at the timing of the sampling pulse stop) is
This signal level (q) is stored in the hold circuit 11 and maintained until the next sampling pulse (E) occurs. Note that since the gate 13 is closed at this time, MMV6 is not reset by the output of the comparator 12.

Waveforms of various parts when there is no color burst signal in the vertical blanking interval etc. are shown on the right side of FIG. 4. At this time, since the gate 16 is closed, the sampling pulse () is not transmitted to the sample and hold circuit 11. Therefore, this hold circuit 11 continues to store the signal level of the previous state. At this time as well, the ramp signal (q) of the time constant circuit of MMV 6 rises with the same time constant, this level is compared with the output ■ of the hold circuit 11 in the comparator 12, and the signal (when q reaches the hold level The 8-reset signal (■) is generated through the gate [opened] 3. This reset signal resets the MMV 6, and its output gate signal (C) disappears at the same time, so that the gate 3 MM
Vlo is triggered and a sampling pulse (E), which is a timing signal, is forcibly generated.

The generation timing of this forced sampling pulse (E) is the same as the generation timing of the immediately preceding sampling pulse stored in the hold circuit 11, so even during periods when there is no color burst signal, the sampling pulse (E) is accurately generated. ) occurs, and the accuracy of the time axis error signal is also improved.

In addition, in the above, MMV for gate signal generation
of the sample and hold signal using the time constant circuit output of 6)
Although the circuit is simplified by storing the generation timing of , it is of course possible to provide a separate integration circuit and trigger this with the output of MMVs to generate a ramp signal.

As described above, according to the present invention, by adding an extremely simple configuration, it is possible to forcibly generate a sampling pulse, which is a timing signal, with high accuracy even during a period when there is no color burst signal, so it is possible to generate accurate sampling pulses at all times. A time axis error signal will be obtained.

[Brief explanation of the drawing]

Figure 1 shows a conventional time axis error signal generation circuit, Figure 2 shows a conventional time axis error signal generation circuit.
1 is an operating waveform diagram of the circuit of FIG. 1, FIG. 3 is a circuit diagram of an embodiment of the present invention, and FIG. 4 is an operating waveform diagram of the circuit of FIG. 3. Explanation of symbols of main parts 1...Color burst separation circuit 3...Gate 4...Horizontal synchronization separation circuit 5, 6.1
0...MMV' 7...Reference signal generation circuit 9.
11... Sample Bold Circuit 14... Color Burst Detection Circuit Applicant Eco(-+)-% Pioneer Co., Ltd. Agent Patent Attorney Motohiko Fujimura 11-

Claims (3)

[Claims] (1) A timing signal generating means for generating a timing signal by detecting the occurrence timing of a predetermined point on the reproduced color burst signal waveform every reproduction horizontal synchronization signal period, and a time axis according to the time difference of the timing signal with respect to a reference signal. a time axis error signal generating device for a reproduced signal, the apparatus comprising: means for generating an error signal; The presence or absence of the reproduced color burst signal in the period from the horizontal synchronization signal to the generation of the timing signal is detected, and when the reproduction color burst signal is absent, the timing signal is generated after a period corresponding to the storage signal of the storage means has elapsed from the generation of the reproduction horizontal synchronization signal. and means for forcibly generating a signal corresponding to. (2) the storage means has a ramp signal generating section that generates a ramp signal in response to the generation of the reproduced horizontal synchronization signal, and a section that samples and holds the ramp signal level based on the timing signal; The hold output level and the ramped signal level are compared when the reproduced color burst is not present, and when both levels become equal, a signal corresponding to the timing signal is forcibly generated. The device according to scope 1. (3) The timing signal generating means has a monostable multivibrator that generates a gate signal for gating a predetermined portion on the reproduced color burst signal waveform, and the time constant of the time constant circuit of the monostable multivibrator 3. The device according to claim 2, wherein a signal waveform is used as the ramped signal.