JPH03268582A - Device for controlling picture quality - Google Patents

Abstract

PURPOSE:To obtain waveform characteristics approximately symmetrical with frequency characteristics whose high band component is attenuated by variably controlling the delay time of each variable delay means based upon a sharpness control signal and variably controlling the amplitude of a signal formed by the 2nd adder in accordance with sharpness. CONSTITUTION:In the case of increasing sharpness, the delay time values of the 1st and 2nd variable delay lines 21, 22 are set up to short values in accordance with a sharpness controls signal inputted from a sharpness control signal input terminal 23 so as to set up the center frequency of each delay signal to a high level. In the case of reducing the sharpness, the center frequency is set up to a low level. Thereby, a video signal and the 1st and 2nd delay signals whose center frequency f0 is selectively adjusted and controlled are inputted to an adder 25 through the 1st, 2nd and 3rd coefficient devices 24a to 24c to form a secondary differential signal. The secondary differential signal is inputted to an adder 27 and added to the 1st delay signal having a half delay time to form a video signal having required sharpness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an image quality adjustment device used, for example, in a video signal processing section of a video tape recorder, a television receiver, or the like.

(Prior Art) Conventionally, as an image quality adjustment device, a transistor Q having a video signal input terminal 1 connected to its base as shown in FIG.
A second-order differentiating circuit 2 is connected to the collector of the circuit, an integrating circuit 3 is connected to the emitter of the second-order differentiating circuit 2, and the second-order differentiating circuit 2 and the integrating circuit 3 are combined and connected to a video signal output terminal 4. be. Of these, the resistance value of the variable resistor 2a of the second-order differential circuit 2 is variably controlled in accordance with the sharpness control signal from the sharpness control signal input terminal 5, and the responsiveness of the second-order differential waveform is set. . At the same time, the integrating circuit 3 integrates the video signal supplied to the transistor Q. As a result, the signal of the second-order differential waveform obtained by the second-order differentiation circuit 2 and the signal obtained by the integration circuit 3 are added and output to the video signal output terminal 4, and a video signal having a predetermined sharpness is output. Ru.

However, as shown in FIG. 4, the above-mentioned image quality adjustment device has the characteristic that the high-frequency components of its frequency characteristics are attenuated, making it difficult to cause double blurring of the image.
The problem was that the symmetry of the waveform characteristics was poor as shown in FIG.

A delay line type using a delay line is known as an image quality adjustment device capable of improving the symmetry of waveform characteristics.

That is, as shown in FIG. 6, the video signal supplied to the video signal input terminal 1 is transmitted through the first and second delay lines 6a, 6.
b, and are delayed by a predetermined time by the first and second delay lines 6a and 6b to obtain first and second delayed signals. Then, these video signals and the first and second delayed signals are respectively guided to coefficient multipliers 78 to 7c, and are each -0
, 25 times, 0.5 times and -0.25 times, the signals are led to an adder 8 and added to generate a second-order differential signal. This second-order differential signal is guided to a variable coefficient unit 9 where the amplitude is controlled, and the second-order differential signal whose amplitude has been controlled and the first delayed signal are added at an adder 10, and the video signal output terminal 4 is output to. As a result, the waveform characteristics become approximately symmetrical, as shown in FIG. 7, and the symmetry is improved.

However, in the above-mentioned image quality adjustment device, as shown in FIG. 8, the high-frequency components of its frequency characteristics are not attenuated.
It is possible to increase the sharpness, but if the sharpness is lowered, the signal waveform will change (see Figure 9), and there is a risk that the vertical lines of image A will be blurred double or triple as shown in Figure 10. Ta.

By the way, as a means to prevent such double blurring, as shown in FIG. 11, the center frequency f is used to emphasize or attenuate the frequency characteristics. There is a method of setting the value above the upper limit of the effective band of the signal passing through.

According to this, when the sharpness of the image is lowered, the center frequency f on the frequency characteristics. When the above bands are not attenuated, the bands become outside the effective band, and almost no signal components exist, thereby preventing image blurring such as double blurring.

However, in the above means, when the sharpness is increased, the higher the frequency within the effective band, the stronger the degree of emphasis becomes, resulting in a problem that the signal-to-noise ratio (S/N ratio) deteriorates.

(Problems to be Solved by the Invention) As described above, in conventional image quality adjustment devices, the symmetry of the waveform characteristics is poor, or the frequency characteristics are unsatisfactory, resulting in problems such as double blur. This has caused problems such as blurring of the image and deterioration of the S/N ratio.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide an image quality adjustment device that can realize substantially symmetrical waveform characteristics and attenuate high-frequency components of the frequency characteristics. shall be.

[Structure of the Invention] (Means for Solving the Problem) The present invention includes a plurality of variable delay means each having the same reference delay time, and passes a video signal through the plurality of variable delay means to generate a reference video signal. a signal delay means for generating a plurality of delayed video signals each delayed by a different time with respect to the signal; and a first addition means for adding predetermined coefficients to each of the reference video signal and the plurality of delayed video signals and then adding the same. , a variable coefficient means for adding a variable coefficient to the seeding force of the first adding means; and a first variable coefficient means for adding a delayed video signal having an intermediate delay time among the plurality of delayed video signals and the output of the variable coefficient means. an image quality adjustment device comprising: a second addition means; and a control means for changing the delay time of the plurality of variable delay means and the coefficient of the variable coefficient means according to a control signal; The sharpness of the video signal is adjusted by the control means.

(Operation) According to the above configuration, the delay time of the variable delay means is variably controlled by the sharpness control signal, so that the signal generated by the second addition means is adjusted according to the sharpness.
With the center frequency of its frequency characteristics variably controlled,
Its amplitude is variably controlled. Therefore, the video signal whose sharpness has been adjusted and controlled can have frequency characteristics in which high-frequency components are attenuated, and can also have substantially symmetrical waveform characteristics.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an image quality adjustment device according to an embodiment of the present invention, in which a first variable delay line 21 is connected to a video signal input terminal 20, and the output of the first variable delay line 2 is connected to a video signal input terminal 20. A second variable delay line 22 having the same delay time as the first variable delay line 21 is connected to the end. The first and second variable delay lines 21 and 22 have sharpness control signal input terminals 23 connected to their respective signal input terminals, and the sharpness control signals from the sharpness control signal input terminals 23 are connected to the sharpness control signal input terminals 23. Correspondingly, the delay time is variably controlled. Further, each output terminal of the video signal input terminal 20 and the first and second variable delay lines 21 and 22 is connected to each input terminal of the first to third coefficient multipliers 24a to 24c, respectively.

The first to third coefficient multipliers 24a to 24c convert the input video signal and the first and second delayed signals to -0, for example.
, 25 times, 0.5 times and -0,25 times, adder 25
Output to. The adder 25 adds the input signals to generate a second-order differential signal, and the second-order differential signal is sent to the variable coefficient multiplier 26.
Output to. A sharpness control signal input terminal 23 is connected to the signal input terminal of the variable coefficient multiplier 26, and depending on the sharpness control signal from this sharpness control signal input terminal 23, for example, the quadratic differential signal is multiplied by 11. The sharpness is variably controlled by controlling the amplitude in the range of ~1. The output end of the variable coefficient multiplier 26 is connected to one input end of the adder 27. This adder 27 has a first variable delay line 2 at its other input terminal.
1 output terminal is connected, and the video signal whose sharpness has been adjusted by adding the input second-order differential signal and the first delay line is outputted to the video signal output terminal 28.

In the above configuration, the first and second variable delay lines 21.2
2, when the delay time increases the sharpness, for example, in response to the sharpness control signal from the sharpness control signal input terminal 23,
If it is set short and its center frequency is set high and the sharpness is lowered, it is set long and its center frequency is set low.

This allows the video signal and the center frequency f. As described above, the first and second delay signals from the first and second variable delay lines 21 and 22 whose adjustment is selectively controlled are transmitted to the first, second and third coefficient multipliers 24a to 24a, respectively. After being led to the adder 24c and multiplied by -0.25 times, 0.5 times and -0.25 times, the signals are led to the adder 25 and a second-order differential signal is generated. This second-order differential signal is multiplied by a factor of 11 to 1 in a variable coefficient multiplier 26 in accordance with the sharpness control signal, and the amplitude is adjusted and controlled.Then, the second-order differential signal is led to an adder 27, where the total delay time is half the delay time. A video signal having a desired sharpness is generated and output to the video signal output terminal 28.

In this way, the image quality adjustment device delays the input video signal in accordance with the sharpness control signal to generate the first and second delayed signals, and the first and second delayed signals and the video signal By obtaining a second-order differential signal, variably controlling the amplitude of this second-order differential signal according to the sharpness control signal, and adding the second-order differential signal whose amplitude has been adjusted and controlled, and the first delayed signal, The system was configured to generate a video signal with controlled sharpness. According to this, the delay times of the first and second variable delay lines 21 and 22 are variably controlled by the sharpness control signal, the center frequency of the frequency characteristic is variably controlled according to the sharpness, and the amplitude thereof is variably controlled. Through variable adjustment by the coefficient multiplier 26, a frequency characteristic is realized in which the high frequency component of the frequency characteristic is attenuated in the effective band as shown in FIG. 2, and symmetry of the waveform characteristic is realized.

Note that in the above embodiment, the first and second variable delay lines 21.
Although 22 variable delay lines are used, the configuration is not limited to this, and an even number of variable delay lines may be used.

Therefore, it goes without saying that the present invention is not limited to the above embodiments, and that various modifications can be made without departing from the spirit of the invention.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide an image quality adjustment device that can realize substantially symmetrical waveform characteristics and attenuate high-frequency components of the frequency characteristics.

[Brief explanation of drawings]

- Fig. 11 is a circuit configuration diagram showing an image quality adjustment device according to an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the frequency characteristics of Fig. 1, and Figs. 3 to 11 are conventional image quality adjustment devices. FIG. 20...Video signal input terminal, 21.22...First
and a second variable delay line, 23... sharpness control signal input terminal, 24a to 24c... first to third coefficient multipliers, 2
5... Adder, 26... Variable coefficient unit, 27... Adder, 28... Video signal output terminal.

Claims (1)

[Claims] A plurality of variable delay means each having the same reference delay time are provided, and a video signal is passed through the plurality of variable delay means to produce a plurality of delays each having a different time delay relative to the reference video signal. a signal delay means for generating a video signal; a first addition means for adding predetermined coefficients to each of the reference video signal and the plurality of delayed video signals; and a variable seeding power of the first addition means; variable coefficient means for providing a coefficient; second addition means for adding a delayed video signal having an intermediate delay time among the plurality of delayed video signals and the output of the variable coefficient means; A control means for changing the delay time of the variable delay means and a coefficient of the variable coefficient means is provided, and the sharpness of the video signal obtained as the output of the second addition means is adjusted by the control means. Features an image quality adjustment device.