JPS60153268A - Picture quality adjusting circuit - Google Patents

Abstract

PURPOSE:To prevent the increase of an undesired component and to improve picture quality by detecting a prescribed signal frequency component out of an arrived input signal and controlling its frequency characteristics at the reproduction of a television picture. CONSTITUTION:A luminance signal is supplied to a frequency characteristic adjusting circuit 1 through a signal input terminal A and also supplied to a signal component detecting circuit 2 to detect only the prescribed signal frequency component out of the input luminance signal. The circuit 1 is controlled by said detecting signal and an adjusted frequency characteristic is outputted. Therefore, undesired components such as noise are not increased by a clearness improving circuit.

Description

Detailed Description of the Invention The invention relates to a circuit for varying the characteristics of an amplifier circuit to obtain a desired signal, and specifically relates to a circuit for varying the waveform response characteristics of a television video signal. This relates to an image quality adjustment circuit.

Conventional configuration and its problems When reproducing a television image, it is not necessarily desirable to faithfully maintain the signal waveform of the incoming input signal and perform predetermined amplification processing. It is known that emphasizing improves sharpness and has sound effects.

In NEC's standard television systems (CNTSC, PAL, SECAM, etc.) that handle relatively narrow signal frequency components, the video signal frequency is about 4 to 6, and the carrier color signal component is multiplexed within this band according to predetermined specifications. Therefore, the effective bandwidth of the bright # signal component becomes narrower than above. When the luminance signal and carrier chrominance signal are separated by normal frequency, the luminance signal bandwidth becomes even narrower, about 3 to 4 times. It is necessary to enhance the signal frequency components and their neighboring components. In addition, in a system that effectively utilizes the signal frequency band specified by the standard television system, for example, in a system that uses a pre-existing comb filter to separate the buried signal component and the carrier color signal component, the frequency band of the luminance signal is However, even in such a case, it is not certain that enhancing the predetermined signal frequency and components in its vicinity is effective in improving the sharpness of image f dust.

A known method of an image quality adjustment circuit having the above-mentioned effects will be described below with reference to the drawings.

In FIG. 1, the video news supplied to the signal input terminal is supplied to a frequency characteristic adjustment circuit 1 for amplifying a predetermined signal frequency component, and this adjustment circuit is, for example, a, b in FIG.
The amplitude-frequency characteristic shown by c is configured to change stepwise or along a road surface line depending on the signal applied to the control terminal C. If no distortion occurs in the phase characteristics when changing this frequency characteristic, for example, the third
As shown in a, b, and c of the figure, the output signal waveform for a rectangular input signal can be varied, and in particular, when a predetermined signal frequency component is to be enhanced, a known preshoot, as shown in the characteristics, can be used. The applied signal waveforms can be sent to all terminals B with approximately the same amplitude due to the aftershoot, and the sharpness can be improved. Even when using a simple configuration that causes phase distortion when changing the distorted frequency characteristics, the above-mentioned preshoot and aftershoot become non-uniform, but the sharpness is substantially improved.

Said 2j! Z1. Narrowing the passband width of the signal frequency indicated by C in Figure 3 is suitable for reducing relatively high-frequency noise components, especially in current television receivers that receive and reproduce radio frequency signals. , and is therefore used in many receivers for purposes other than improving sharpness.

The above-mentioned known image quality adjustment circuits have various drawbacks because they are designed to, in principle, give a certain enhancement effect to predetermined frequency components in the incoming input signal. Firstly, when the frequency characteristics shown in b in Fig. 2 are given, preshoot and aftershoot with a time width approximately determined by the peak frequency in the frequency bandwidth to be enhanced will occur. For example, if the peak frequency is 2 stone degrees, each time is about 0.25 microseconds,
This means that as long as the change times and amplitudes of the rise and fall of an input signal that changes stepwise are equal, the preshoot and aftershoot will be the same regardless of the repetition frequency of the signal change. become. In television images, the signal component generated through the camera system becomes an electrical signal in which the step change part of the subject changes somewhat gradually due to so-called aperture distortion caused by the deterioration of the camera's spatial frequency response to high frequency components. The signal components within the signal frequency band defined by the John system are sufficiently clear and even include electrically generated information signal components such as letters or numbers.

In particular, for the latter, it is normal to perform predetermined frequency band limiting processing before transmitting, but the rising and falling signal change times are shorter than for natural image signal components, and in some cases, the signal changes abruptly. , its amplitude is also sufficiently large. The above 0.2
Attachment 711 for sharpness improvement of 5 microseconds] For example, when the incoming input signal is a pulse with a width of 0.25 microseconds, the signal component is approximately equal to the width of the preshoot and aftershoot, and For a narrow pulse-like signal, the width of the additional signal for improving sharpness becomes too wide, resulting in unfavorable image quality. Although this known method is suitable for emphasizing the contours of low-frequency signal components with a relatively wide signal width, it is suitable for emphasizing the contours of low-frequency signal components that are relatively wide in signal width. Since it acts uniformly on the signal components of Of course, one way to improve image quality is to further increase the peak frequency to enhance the frequency characteristics used in the above explanation, but it may cause ringing or lack of sharpness improvement effect on average images. It is difficult to use because of the following drawbacks.

Firstly, secondly, frequency characteristic enhancement uniformly enhances undesirable components such as noise (by degrading the M-signal-to-noise ratio, which affects not only weak electric fields but also normal reception). It is well known that it is a drawback in terms of electric field strength.

Furthermore, when receiving and reproducing radio frequency signals, the frequency characteristics of the transmission system may differ depending on the receiving channel, and in order to provide a uniform effect to this effect, additional information for sharpness is added. The signal has drawbacks such as excessive or insufficient amplitude.

As mentioned above, although the known image quality adjustment methods have advantages, they also have major drawbacks and cannot provide sufficient performance.

OBJECTS OF THE INVENTION It is a primary object of the present invention to produce television images with improved sharpness.

A second object of the present invention is to prevent undesirable components such as noise from being significantly enhanced by the sharpness improvement path, thereby improving image quality.

Structure of the Invention Inventively, the image quality adjustment circuit has a mechanism for detecting all predetermined signal frequency components in the incoming input No. 16 and controlling the frequency characteristics using the detected signal components, thereby improving sharpness. It has a characteristic sound that weights the effective image parts. The frequency characteristic for this sharpness textbook comprises at least the known method of enhancing a given signal frequency component and its neighboring components in the amplitude-frequency characteristic, and is limited by the present invention with respect to the phase-frequency characteristic. It is selected as appropriate without any need. Of course, the characteristic curve of the amplitude-frequency characteristic described above is not limited by the present invention, but the amplitude to be enhanced or the peak frequency, etc., is controlled according to the content of the image.

DESCRIPTION OF EMBODIMENTS Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 4, a luminance signal is input to the frequency characteristic adjustment circuit 1 through the signal input terminal Ay, while a similar luminance signal is also supplied to the signal component detection circuit 2 arranged according to the present invention. This detection circuit 2 detects only the signal frequency component with a relatively larger amplitude change than the input luminance signal, and performs a predetermined linear amplification process on this signal, or converts it into a DC signal component. If the control signal voltage is converted and output, and the output signal voltage has a characteristic such that the output signal voltage decreases as the frequency increases, as shown by characteristic X in Figure 5, then this control signal voltage cannot be supplied via terminal C. The frequency characteristics of the adjustment circuit 1 as shown by a, b, and c in FIG. 2 are changed in a steno knob shape or in an analog manner. When the frequency characteristic adjustment circuit 1 controlled by the detection circuit 2 receives a rectangular wave signal as shown in FIG.
A signal as shown in the figure is output. The signal level is El
For a signal that changes from E2 to E2 and has a relatively wide pulse width T1, in the present invention, a preshoot and an aftershoot are added to each change with an amplitude of E4-E2,
This amplification has the same degree of amplification as, for example, known methods. On the other hand, the level change of the input signal is E
For signal components whose pulse width is relatively narrow from l to E2 or 'f2, the preshoot of E3-E2 is
Although the aftershoot is added, its amplitude is smaller than that of the above-mentioned one, and is approximately half that. It is assumed that the change times of the rise and fall of these two signals are the same, and the level ratio of the signal added to improve sharpness is selected or adjusted as appropriate depending on the slope of the characteristic X shown in FIG. Changeable and non-linear changes! It is also possible to do so.

Assuming that the detection circuit 2 has a detection characteristic as shown by characteristic Y in FIG. generates an output signal voltage of –! , a signal voltage of E6 is generated at T2, which means that the pulse width is narrow,
It is shown that a signal voltage that changes approximately linearly is output for signal components between the pulse widths of T1 and T2. A characteristic adjustment circuit 1 controlled by the output of this detection circuit applies an enhancement effect to a relatively large sharpness improvement signal component for an incoming input signal having a pulse width T1, similar to that shown in FIG. , on the other hand, the degree of enhancement is small for the input signal component having the pulse width T2, and a substantially linear change is given to the signal component between these. The above is just an example, and the detection circuit 2 has the pulse width T shown in FIG. 5, for example. The output signal 'tortoise pressure' is 1! -5
It may be configured to take two values: and E6.

FIG. 7 shows a second embodiment of the image quality adjustment circuit according to the present invention. In the figure, a video signal applied to signal output terminal 8 is supplied to delay circuit 3 and differentiation circuit 21, respectively. For example, if the input signal component is as shown in FIG. 8a, the differentiating circuit 21 sends out a second-order differentiated signal component as shown in FIG. 8a to its output terminal. The control pulse generator 22 has a pulse width T as shown in FIG. 8C as all inputs of the second-order differential signal components. The negative polarity signal is generated at the output terminal every time the positive polarity pulse shown in the figure is applied, but it also responds to the human-powered positive polarity a pulse that is applied during the period when the negative polarity iM@ is generated in the output. configured to do so.

Therefore, for a series of input pulses as shown at 82, the output is maintained, resulting in a wide negative polarity signal as shown at T0'.

The output of this pulse generator 22 is the characteristic adjustment circuit 1.
is used as a control signal for the incoming input signal delayed by the delay circuit 3, and operates to stop the sharpness improvement action or reduce the degree of enhancement during a period in which the control signal is negative with respect to the incoming input signal delayed by the delay circuit 3; Therefore, a signal as shown in FIG. 8e is obtained at the signal output terminal B. The delay circuit 3 determines the time To + for the control pulse generator to send out a negative polarity pulse signal to its output terminal in response to the human input pulse.
Basically, it has a delay time of /Z, but adding a delay of one line or an integral multiple of one line to this is permissible as long as the video signals have a correlation in the scanning line direction. It is of course possible to arrange a differentiating circuit in place of the above-mentioned delay circuit 3 on the side of the sub-side 1-pulse generator.

FIG. 9 shows another embodiment of the invention. In the figure, the output signal of the differentiating circuit 21 is transmitted to the control pulse generator 2.
2 edges and a delay circuit 23, and their outputs are supplied to a gate circuit 24. The differentiating circuit 21 and the control i11 pulse generator 22 operate in the same manner as those shown in FIG. 7, and a negative polarity signal as shown in FIG. 10C is obtained at the output of the control pulse generator 22. Delay circuit 23
is the time T during which the control pulse generator 22 sends a negative polarity pulse signal to its output terminal in response to a quasi- input pulse of the output signal of the differentiating circuit 21. It has a delay time of +a and is supplied to the gate circuit 24 at the timing shown in FIG. 10d. This gate circuit 24 supplies the output of the delay circuit 23 to the adder 11 only during the period when the gate signal indicated by the 101st line C is positive. By the addition, the signal shown in FIG. 10e is obtained and sent to the signal output terminal B.

Needless to say, it is possible to select various delay times for the delay circuit 3 in the same way as the delay circuit shown in FIG. 8 described above.
The delay circuit 23 can also be changed within a range for the purpose of matching the relative phases between the two signals in the adder 11.

In the uninvented embodiment of the invention, if the output pulse width of the control pulse generator 22 has a minimum width of, for example, about 25 microseconds, then the signal component has a repeating synchronization corresponding to two waves, In other words, as a boundary between the signal components that give approximately 160 horizontal resolution lines, the desired frequency is lower for signals that produce a larger number of resolution lines, and the desired frequency for signals that produce less than 160 resolution lines. Although it is possible to give a component enhancement effect, the number of resolution lines or the degree of enhancement of frequency components that serve as the boundary may be selected as appropriate.

1. In the above embodiment, a differential circuit was shown as an example for detecting the amplitude change of a video signal, but the present invention is not limited to the specific configuration of this circuit, and furthermore, the present invention is not limited to the specific configuration of this circuit. By installing two circuits and two devices, it is possible to configure the detection output signal voltage to vary approximately linearly with respect to the signal pulse width as shown in FIG. It is within the range.

Effects of the Invention As described above, the present invention includes a video signal that is an incoming input signal. The feature is that the degree of frequency component enhancement effect for sharpness improvement is controlled according to the width of the signal pulse to be distorted, and the sharpness improvement is suitable for the distortion of relatively wide and narrow signal components. Since a signal can be added, the image quality can be improved to the full width.

Noise again? For signals containing a large amount of signals, the detection circuit 11 of the present invention continues to operate, so that the sharpness improvement operation substantially automatically stops, which has the effect of preventing undesired enhancement of good sound. Value is a dog.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional image quality adjustment circuit, Figures 2 and 3 are special game 1 diagrams for explaining the circuit in Figure 1, and Figure 4
The figure is a basic configuration diagram of an image quality adjustment circuit according to an embodiment of the present invention, FIGS. 5 and 6 are characteristic diagrams and waveform diagrams for a brightness of the same embodiment, and FIGS. 7 and 9 are diagrams according to the present invention. FIG. 8 and FIG. 1o are block diagrams showing other embodiments, and are signal waveform diagrams for explaining the operation. 1...Characteristic adjustment circuit, 2...Detection circuit,
3... Delay circuit, 21... Differential circuit, 22...
...Control pulse generator, 23...Delay circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Ripples for Figure 2 Figure 3 Figure 4 / Figure 5 2 Figure 6 Figure 7 838 Figure 9 Figure 10

Claims (1)

[Claims] A signal detection means is provided which receives a video signal component as an input, has at least an amplitude-frequency characteristic changing means, and receives the video signal as an input and detects a predetermined signal frequency component;
An image quality adjustment circuit characterized in that the detection means fully controls the frequency characteristic changing means.