JPS5813664Y2 - color television receiver - Google Patents

Description

[Detailed description of the invention] Conventionally, for example, 19H of the vertical blanking period of an NTSC video signal
VI R8 (Vertical Interva)
It is known to insert and transmit a reference signal (Reference Signal) and use it as a reference signal when correcting various distortions in the transmission path on the receiving side, particularly when correcting color signals.

However, when various ghosts are encountered due to radio wave reflections in the transmission path, VV in the received television signal becomes
The IR8 is also distorted and becomes an incorrect reference signal, and when correcting the color signal with such an incorrect VIR8, the correction is made incorrectly and the image quality deteriorates.

Focusing on this point, the present invention provides a circuit for detecting the presence or absence of a ghost in a color television receiver equipped with a VIR8 correction circuit, and when a ghost is detected, the VIR
The above drawbacks are solved by stopping the 8 correction.

Figure 1 shows a system diagram when the present invention is implemented in a color television receiver that performs VIR8 correction of hue and saturation.

In FIG. 1, 200 is a VIR8 correction circuit, 300 is a VIR8 detection circuit, 500 is a ghost detection circuit according to the present invention, 400 is a switch switched by the ghost detection circuit 500, and 600 is a changeover switch 400 from a VIR8 correction voltage to a preset voltage. This is a control voltage adjustment circuit that switches the control voltage (hue and saturation).

The other parts are already well known, so their explanation will be omitted.

Before explaining the present invention, VIR8 correction of hue and saturation will be briefly explained.

First, a gate pulse VIR is used to extract VI R8 inserted at the 19th H from the horizontal synchronizing pulse and vertical synchronizing pulse separated by the same vision separation circuit 110.
This VIRS gate pulse is generated by an S gate pulse generator 203 and applied to sample and hold circuits 201 and 202.

Sample and hold circuits 201 and 202 each have R-
VIR8 contained in the Y signal and B-Y signal is extracted and applied to the changeover switch 400.

Since the changeover switch circuit 400 connects contact a when VIR8 is present, VIR8 is connected to the color gain leg device 2.
0 to correct the saturation, and the other to the phase shifter 80 to correct the hue.

Here, the VIR8 detector 300 is for detecting the presence or absence of VIR8, which was proposed earlier by the inventor of the present application, and when VIR8 is present, the changeover switch 400 is
The contact a remains connected, but when VIR8 is not present, the changeover switch 400 switches to contact A, stops VIR8 correction, and instead of the VIR3 correction voltage, the control voltage adjustment circuit 600 adjusts the hue and saturation, respectively. A preset DC voltage is supplied to each of the above-mentioned control units 20.80.

In the present invention, when a ghost is detected by the ghost detection circuit 500, the changeover switch 400 switches contact a to contact In addition to the above-mentioned control units 20.80, correction of hue and saturation by VIR3 is not performed.

Therefore, according to the present invention, false VIR due to ghost
8 correction can be prevented.

Next, the ghost detection circuit used in the present invention will be described.

Detection of whether or not there is a ghost in the received television radio waves is performed using an I/O signal with a vertical blanking period of the television video signal.
If a ghost detection pulse is superimposed on H, the H period may be gated and extracted, and the presence or absence of a ghost pulse delayed after the detection pulse may be determined.

If ghost detection pulses are not superimposed on current television broadcast waves, the following method can be considered.

(1) If a fixed signal such as VIR8 or VITS (television radio test signal) is superimposed on the vertical blanking period, detect whether or not there is a delayed signal (ghost) of these signals.

(2) Detect whether there is a delayed signal (ghost) of the synchronization pulse (or equalization pulse) in the vertical blanking period.

Although FIG. 3 shows a ghost detection circuit using method (2) above, the same applies to cases where other methods are used.

FIG. 2 shows waveforms at various points in the ghost detection circuit, and a in the figure shows the vertical blanking period of a composite video signal with a ghost.

However, ghosts are caused by the high-frequency phase difference ψ between the direct wave and the reflected wave.
is shown as zero.

From such a composite video signal a, for example, a gate pulse generator 501 that generates a sampling pulse b of approximately IHO width at the IOHth point extracts a horizontal synchronizing pulse no coast pulse C using an analog switch 502, and a flip-flop 503 is set. do.

The flip-flop 503 receives the vertical synchronization signal d in advance.
Since it has been cleared with , if there is a ghost, it is "1"
, and if there are no ghosts, it is in the reset state.

The changeover switch 400 shown in FIG. 1 is operated by the ghost detection output signal e, and when there is a ghost in the received television radio waves, the VIR8 correction can be stopped.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram regarding a ghost detection circuit, and FIG. 3 is a block diagram showing an example of the ghost detection circuit. 200 is a VIR8 correction circuit, 300 is a VIR8 detector,
400 is a changeover switch, 500 is a ghost detection circuit, 6
00 indicates a control voltage adjustment circuit.

Claims (1)

[Scope of utility model registration request] This VI is received by receiving VIR8 inserted in the vertical retrace period.
A color ten vision receiver equipped with a color correction circuit that corrects hue or saturation using R8 is equipped with a circuit that detects the presence or absence of ghosts, and the output of this detection circuit controls the color correction circuit to eliminate ghosts. When the above VI exists
A color television receiver characterized in that a color correction circuit based on R8 is made inactive.