JPS60223280A - Time axis correcting device - Google Patents

Abstract

PURPOSE:To obtain an accurate time axis error signal by defining a phase error of a reproduced color burst signal as a correction signal when the phase error of a reproduced horizontal synchronizing signal is limited within a certain range. CONSTITUTION:The RF signal read by a pickup is converted into a color video signal by a demodulator 1 and sent to a time axis corrector 2 and then sent outside as a reproduced color video signal. The horizontal synchronizing signal separated by a horizontal synchronizing separator 9 undergoes the comparison of phase with a reference signal given from a divider 12 through a phase comparator 13. This output of comparison drives a tangential mirror 17 and a spindle motor 18 via an adder 14. Furthermore said color video signal is compared with a reference signal given from a divider 4 by a comparator 5. This signal is sent to the corrector 2 by the output of a window comparator 11 as a time axis error signal when the output of the comparator 13 is kept within a prescribed range.

Description

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

111 Method 1 of detecting time axis fluctuation of reproduced color video signal
Another method is to directly compare the phase of the reference signal and the reproduced burst signal, but this method is impossible if the phase difference between the reference signal and the burst signal is at or near the center of the operating range of the phase comparator. Axis errors cannot be detected. In other words, this method cannot be used unless the frequency difference between the reference signal and the reproduced burst signal is zero and the phase difference is also within a certain range.

Another known method is a method using a PLL (phase locked loop) circuit having an rlVCO (N pressure controlled oscillator). In this method, the feedback loop operates so that the phase of the VCO is locked to the phase of the reproduced burst signal, so that if the time axis error is within the pull-in range of the PLL circuit, the error can be detected accurately.

However, in this method using a PLL circuit, the stability of the PLL circuit is determined by the loop filter and loop gain, but the filter characteristics and loop gain are set to stabilize the PLL circuit and widen the pull-in range. Then, the PLL circuit also responds to the low-frequency component of the time-axis variation of the reproduced burst signal, and as a result, there is a disadvantage that the preceding time-axis error'' signal lacks the low-frequency component.

Therefore, it is possible to accurately detect the time axis error of the reproduced signal regardless of the fluctuation range of the burst phase of the reproduced color video signal and by eliminating the above-mentioned problems related to the loop stability of the PLL method. The device was published in Japanese Patent Application Laid-Open No. 58-134.
It is disclosed in Japanese Patent No. 594.

In this device, a signal having the same frequency as the color burst signal and a phase equal to the average phase of the reproduced burst signal is generated based on a fixed oscillation output, and the phase difference between this signal and the reproduced color burst signal is The apparatus is configured to correct the time axis error of the reproduced color video signal according to the color video signal.

The device disclosed in JP-A-58-13459/1 includes a 4111i1 multiplier, four LPFs (low-pass filters), and a reference oscillation signal (subcarrier) of π/2
A phase shifter, etc. is required at a minimum, which complicates the configuration, and
It also requires adjustment.

To 11 11 An object of the present invention is to provide a time axis correction device that can generate an accurate time axis error signal by eliminating the need for adjustment, the complexity of the configuration, and the lack of low frequency components of the time axis error signal. It is to be.

The time axis correction device according to the present invention performs a phase comparison between the reproduced horizontal synchronization signal and the reference signal, and also performs phase comparison between the reproduced horizontal synchronization signal and the reference signal, and
Compare the phase of the signal and the reference signal, and when the phase error of the reproduced horizontal synchronizing signal falls within a certain range, the phase error of the reproduced color burst signal is derived by means of Goo 1 and the time axis of the reproduced color video signal is calculated. In addition to being used as a correction signal for correction, the output from the Goo 1 means and the phase error of the reproduced horizontal synchronization signal are combined, and this synthesis horn is used as an error signal for the time axis feedback loop.

,! EJJL The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a circuit block diagram of an embodiment of the present invention, in which an RF (high frequency) signal read by a pickup (not shown) is converted into a color video signal by a demodulator 1, and is converted into a color video signal via a time axis corrector 2. It becomes a reproduced color video signal output and is led out.

On the other hand, an oscillator 3 that generates an oscillation output of 7 and 16 MHz as a reference signal is provided, and this oscillation output is sent to a frequency divider 4.
and 12, the frequencies are divided into 1/2 and 1/455, respectively, to become reference signals for the color subcarrier signal 7 and the horizontal synchronization signal. In the phase comparator 13, the phase of this horizontal synchronization signal reference signal and the horizontal synchronization signal in the reproduced video signal separated by the horizontal synchronization separator 9 are compared,
This comparison output passes through an adder 14 and equalizers Fj' 15 and 16, respectively, and drives the tangential mirror 1f and the spindle motor 18.

On the other hand, the frequency divided output from the frequency divider 4 is phase-compared with the reproduced color video signal in the phase comparator 5, and the next S/H (
Sample/bold) circuit 6 samples and holds each burst. The output of this S/H circuit 6 is the gate 7
It becomes a control signal for the time axis corrector 2 through the LPF 8, and becomes a control signal for the adder 14 through the LPF 8.
This becomes a drive signal for the 7° spindle motor 18.

The gate 7 is opened and closed by the output of a window comparator 11, which detects the level of the comparison output of the phase comparator 13 and opens the gate 7 only when this level is within a certain range. It is configured to be open.

In such a configuration, a phase error of the reproduced horizontal synchronizing signal with respect to the reference signal and a phase error of the reproduced color burst signal with respect to the reference signal are respectively detected, but if the phase error of the reproduced horizontal synchronizing signal is within a certain range. The phase error of the reproduced color burst signal is derived from the gate 7 and becomes a control signal for the time base corrector 2 only when the time axis corrector 2 is present. Further, the low-frequency error component of the output of the gate 7 that has passed through the LPF 8 is added and synthesized with the phase error of the horizontal synchronizing signal by an adder 14, and becomes an error signal of a feedback loop for time axis correction. Therefore, when the phase error of the horizontal synchronization signal becomes small to a certain extent, the phase error of the color burst signal is reduced to 1~1 and the time axis is corrected, so that the phase of the subcarrier is locked and this burst phase error is reduced. Since the frequency components are combined and inserted into the feedback loop, the horizontal synchronization (the phase of the i signal is also overlocked).

Incidentally, the time axis corrector 2 is disclosed in, for example, Japanese Patent Application No. 1268-1983.
A delay element such as that disclosed in the specification of No. 8 or a CCD (charge coupled device) can be used.

The above embodiment is for the NTSC system, but in the PAL system, the oscillator 3' of <3.75M1-1z as shown in FIG. and 1
The output of the oscillator 3' may be input to the phase comparator 5, and the output of the frequency divider 12' may be input to the phase comparator 13 using the /240 frequency divider 12'.

Furthermore, instead of the tangency 1 full mirror 17 in the feedback loop, a variable delay line such as a COD may be used to detect the phase error of the reproduced horizontal synchronizing signal and the reproduced color burst signal at its output. A block diagram of the embodiment in the case shown in FIG. There is. I am trying to control CCD19. The other configurations are similar to the example shown in FIG.

As described above, according to the present invention, the circuit configuration is simplified, which is advantageous in terms of cost, and also eliminates the need for adjustment. Another advantage is that it is easy to become familiar with the NTSC and PΔL systems.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a partial modification of block L1 in FIG. 1, and FIG. 3 is a block diagram of another embodiment of the present invention. Explanation of symbols of main parts 2... Time axis corrector 3... Reference signal generator 5.13... Phase comparator 7... Goo i~ Applicant Pioneer Co., Ltd. Agent Patent Attorney Motohiko Fujimura

Claims (1)

[Claims] a first phase comparison means for performing a phase comparison between the reproduced horizontal synchronization signal and the reference signal; a second phase comparison means for performing a phase comparison between the reproduction color burst signal and the reference signal; and the first phase comparison means described in 60. a gate output for deriving the comparison output of the second phase comparison means whenever the comparison output of the second phase comparison means is within a predetermined range, and the gate output of the gate means forms a time axis correction loop for the reproduced video signal. At the same time,
A time axis correction device characterized in that a signal corresponding to the gate output and a comparison amount horn of the first phase comparing means are combined, and a time axis correction feedback loop is formed by the combined output.