JPS6130880A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To correct automatically characteristics of frequency of an video signal toward a good condition by controlling an amplifier of a variable frequency characteristics obtaining information of frequency characteristics thereof from a synchronous signal of video signals. CONSTITUTION:Supposing that high frequency of a video signal Sv' obtained at the output side of an amplifier 1 is in a deteriorated condition, a horizontal synchronizing signal dulled in rise and fall gated by a gate pulse PG is obtained from the gate circuit 13, and a differential pulse Pd2 having a peak value e1 is obtained from a differential circuit 9. While, a horizontal synchronizing signal having frequency characteristics as reference not undeteriorated in high frequency from a wave shoping circuit 8, a differential pulse Pd1 having a peak value e1 is obtained from a differential circuit 9. In this case, it becomes evidently e2<e1, so an error signal Sd is supplied from a comparator 11 to a correction section 1a, so that correction is made in order that e2=e1 may be realized, that is, frequency character of the video signal Sv' may possess frequency characteristics as reference not deteriorated in high frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal processing circuit that is capable of automatically correcting the frequency characteristics of a video signal whose high frequencies have deteriorated in a transmission path, for example.

Background technology and problems Eirin signals have various characteristics such as frequency characteristics, DG (
Gain), DP (phase), etc. are affected.

For example, if the high frequency range deteriorates, higher resolution will be hindered. For example, in the case of overcompensation in the aperture correction circuit, image quality deteriorates due to ringing and the like.

Purpose of the Invention In view of the above, the present invention is designed to automatically correct the frequency characteristics of a video signal to a favorable state.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention includes a variable frequency characteristic amplifier, a video signal is outputted through the amplifier, and information on the frequency characteristic of the video signal is obtained from a synchronization signal of the video signal.
Based on this, the variable frequency characteristic amplifier is controlled, and the frequency characteristic of the video signal is automatically corrected to a favorable state.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG.

In the same figure, (1) is a variable frequency characteristic amplifier;
The video signal Sv supplied to the terminal (2) is transmitted through this amplifier (
1) and is output to terminal (3). In the amplifier (1), (1a) is a frequency characteristic correction section, which in this example is configured using a variable capacitance diode (1b).

Further, the video signal Sv supplied to the terminal (2) is supplied to the dart circuit (5) via the amplifier (4). A polarity inversion signal ST is supplied from a terminal (6) to the amplifier (4), so that the polarity of the signal can be inverted. In addition, the dirt circuit (5) is connected to the terminal (7) and the jigut pulse P. is supplied, and the horizontal synchronization signal of the video signal Sv is gated.

The horizontal synchronizing signal gated by the dart circuit (5) is waveform-shaped by a waveform shaping circuit (8). This determines the state of the reference frequency characteristic.

This waveform-shaped signal is supplied to a differentiating circuit (9) and differentiated to obtain a differentiated pulse Pd1.
The pulse Pd1 has a peak level corresponding to the frequency characteristic 9. That is, it has a peak level that corresponds to the reference frequency characteristic.

This differential value Pd is supplied to a peak hold circuit ◇Q, its peak value e1 is held, and this hold output is supplied to one terminal of a comparator (11).

Further, the video signal S( obtained at the output side of the amplifier (1)) is supplied to the dart circuit (2) via the amplifier (2).

Similar to the amplifier (4) described above, the amplifier (6) is also supplied with a polarity inversion signal S from the terminal (6), so that the polarity of the signal can be inverted. In addition, the above r-t circuit (
Similarly to 5), the digital signal PG is supplied to the dart circuit (6) through the terminal (7), and the horizontal synchronizing signal of the video signal S'V is gated.

The horizontal synchronizing signal gated by the dart circuit (2) is supplied to the differentiating circuit α◆ and differentiated to obtain a differential signal Pd2. This differential signal Pd2 has a peak level that corresponds to the frequency characteristics of the video signal S'V.

This differential pulse Pd2 is supplied to a peak hold circuit αQ, its peak value e2 is held, and this hold output is supplied to the other terminal of the comparator a).

Further, from the comparator αp, an error signal Sd for e of the peak value e2 is obtained, which is supplied to the correction section (1a) of the amplifier (1) via the resistor (IE), ) is changed to control the amount of peaking. That is, it is controlled so that the peak value e2 becomes equal to 01, and therefore, the frequency characteristics of the video signal S (s) match the frequency characteristics of the reference.

In the circuit of this example configured as above, if, for example, the high frequency range of the video signal SY supplied to terminal (1) is degraded (see Figure 3A), therefore, as shown in Figure 2A, Let us consider a case in which the rising and falling edges of the horizontal synchronizing signal H8ync are slow.

If the video signal S'V obtained at the output side of the amplifier (1) remains degraded in the high frequency range in this way, the dirt pulse P0 shown in FIG. A horizontal synchronizing signal with slow rising and falling edges is obtained as shown in FIG. Then, from the differential circuit ←, the differential pulse Pd of the peak value e2 as shown in the same figure
2 is obtained.

On the other hand, from the waveform shaping circuit (8), as shown in FIG. 2E, a horizontal synchronizing signal having standard frequency characteristics with no deterioration in the high range is obtained. Then, from the differential circuit (9), a differential pulse Pd1 having a peak value of 61 as shown in FIG.
is obtained.

In this case, it is clear that e2(el), so the comparator (I
]) to the correction unit (1a), and the error signal Sd is supplied from @
2::J, that is, the frequency characteristics of the video signal etc. are corrected to have the standard frequency characteristics (see FIG. 3B) with no deterioration in the high range.

Therefore, the video signal S6 obtained at the output side of Anne f(1)
has a standard frequency characteristic as shown in FIG. 2G, and this is obtained at the terminal (3).

In the circuit of this example, by inverting the polarity of the output signals of amplifiers (4) and (2) using the polarity inversion signals S and r from the terminal (6), the rising edge and rising edge of the horizontal synchronizing signal can be controlled. The frequency characteristics in the lower image area are corrected. This is effective because the frequency characteristics may differ between rising and falling edges.

Furthermore, in the circuit of this example, the dirt circuits (5) and (11
By controlling the supply cycle of the gate/gurus PG supplied to the PG, the time for correcting the frequency characteristics can be arbitrarily set.

According to this example, even if the video signal Sv that does not have the reference frequency characteristics is supplied to the terminal (2), it is possible to obtain the video signal S (having the reference frequency characteristics) to the terminal (3). Can be done.

In the above-mentioned embodiment, the reference synchronization signal giving the reference frequency characteristic is formed by passing the horizontal synchronization signal which has been zigged from the video signal Sv through the waveform shaping circuit (8). It is also possible to use a synchronization signal separated by

Further, in the above embodiment, the correction section (1a) uses a variable capacitance diode (1b), but several capacitors are provided in a pot and the connection of each is controlled based on the error signal Sd. It can also be configured to change the value of the composite capacitance. Furthermore, a transpersal filter or the like can also be used.

In addition, in the above embodiment, the horizontal synchronization signal) [5yn
Although the focus is on the e portion, it is also possible to focus on the vertical synchronization signal portion.

Effects of the Invention As is clear from the embodiments described above, according to the present invention, the frequency characteristics of the video signal are automatically corrected to a favorable state. Therefore, if the present invention is applied to, for example, a television receiver, it will no longer depend on the performance of transmission equipment, etc., so there will be no difference in image quality between broadcasting stations, and high-resolution images can always be obtained.

Further, even if there is overcompensation in the aperture correction circuit, ringing phase shift is reduced, and deterioration of image quality is prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIGS. 2 and 3 are diagrams for explaining the same. (1) is a variable frequency characteristic A/Z, (1 &) is a frequency characteristic correction section, (5) and (2) are each a dart circuit, (8) is a waveform shaping circuit, (9) and α◆ are each a differentiating circuit , α0 and (2) are peak hold circuits, and H is a comparator. Figure 81 Figure 12

Claims (1)

[Claims] A variable frequency characteristic amplifier is provided, and a video signal is outputted through the amplifier, and a synchronization signal obtained by gated from this output signal is differentiated and peak-held to obtain a first signal and a reference synchronization signal. A video signal processing circuit characterized in that a second signal is obtained by peak holding after differentiation, and the frequency characteristics of the amplifier are controlled by a comparison output of the first and second signals.