SU1197145A1 - Device for correcting gradation distortions - Google Patents

Abstract

The invention relates to a technique of television and provides an increase in correction accuracy and quality of a television image by reducing the level of bluntness in its light areas. The input television signal is fed to the first low-pass filter (LPF) 3, through the third line, delay (LZ) 18 - on the fifth threshold element (PE) 19, and through the first IG - on the second low-pass filter 8. The output signal of the low-pass filter 8 goes to the first adder (C) 11 and to the subtraction unit (BB) 9, to another input of the BV 9 receives a signal from LZ 1, passing through the second LZ 7. High-frequency components l kitsie spectrum TV signal with BV 9 through a switch (K) 10 provided to the other input of the first from 11 9 C 13 or second depending on which control input / S e

Description

K) a logical 1 signal is present. From the output of the first C 11 signal through a nonlinear | 51st block 12, it arrives at the second C 13, the output of which forms the output signal of the device, K 10 is controlled by signals generated by PE 5, 6, 16, 17, 19. Their signals through the OR element 20 and the And 21 element arrive at the corresponding control inputs K 10. With the low-pass filter 3, the signal through the first differentiating unit 4 enters the PE 5, 6, and the signal from the LZ 1 part through the second differentiating unit 1.5 goes to PE 16 and 17. PE 5 and 6 detect single video pulses of short duration, and PE 16 and 17 - gr ppovye izobrazhe197145 structure

neither When a signal from contrasting detail is detected, the signal from K 10 is supplied to the first C 11 to effect a non-linear transformation. The signal mixture of low contrast details and noise is fed to the second C 13, mine is a nonlinear block 12. So on. Two modes of operation are provided: at the level of the input signal corresponding to the dark areas of the image, the low-frequency components of the television signal and components of contrasting fine details are subjected to non-linear transformation, and at the level of the input signal corresponding to the bright parts of the image, all components of the TV signal. 1 il.

The invention relates to a television technique and is used to improve the quality of a television image.

The purpose of the invention is to improve the accuracy of the correction and the quality of the television image by reducing the level of noise in its light areas.

The drawing shows a structural electrical circuit of the device for correcting the gradation distortions.

Correctional distortion correction device Contains the first delay line 1, the input of which is connected to the input width 2 of the device, and through the first low-pass filter 3 and the first differentiating unit 4 to the inputs of the first 5 and second 6 threshold elements, the output of the first delay line 1 is connected through the second delay line 7 with the first input and through the second low-pass filter 8 with the second input of the subtraction unit 9, the output of which is connected to the input of the switch 10, the first output of which is connected to the first input of the first adder 1 1, the second input of which is connected to the second input of subtraction unit 9, and the output through nonlinear block 12 is connected to the first input of the second adder 13, the second input of which is connected to the second output of the switch 10, and the output is connected to the output thickness 14 of the device, the additional output of the first lines

delay 1 through the second differentiating unit. 15 is connected to the inputs of the third 16 and fourth 17 threshold elements, the direct outputs of the first 5 and second 6 threshold

elements are connected respectively to the direct outputs of the fourth 17 and third 16 threshold elements, the input of the first delay line 1 through the third delay line 18 is connected

with the input of the p of the threshold element 19, the direct output of which is connected to the first input of the element OR 20, the second input of which is connected to the direct output of the third threshold

element 16, and the output is connected to the first control input of the switch 10, the second control input of which is connected to the output of the element And 21, the first, second, third

and the quarter inputs of which are connected respectively to the direct output of the first 5 and inverse outputs of the second 6, third 16 and fifth 19 threshold elements.

The correction device of the gradation distortion works as follows.

3

TV input signal. comes to the delay line 1 and filter 3. The delay line 1 provides a signal delay for the time it spreads through the filter 3, differentiation unit 4, threshold element 5 and element 21. The output signal from delay line 1 goes to filter 8 and through the delay line 7 to a subtraction unit 9, at the output of which the high-frequency components of the television signal spectrum are allocated, and at the output of the filter 8 its low-frequency components. The signal of the high-frequency components is fed to the switch 10, and the low-frequency components to the first adder 11.

The switch 10 performs the switching of the high frequency components of the television signal. In this case, if there is a level signal corresponding to the logical T at the first control input of the switch 10, the high frequency components arrive at the input of the second adder 13. In the presence of a signal level corresponding to logical 1 at the second control input of the switch 10, the high frequency components arrive at input of the first adder 11.

Switch 10 is controlled by the output signals generated by threshold elements 5, 6, 16, 17, 19, the element OR 20 and the element 21.

At the direct output of the threshold elements, a signal corresponding to the level of logic 1 appears in the event that the incoming signals exceed the set threshold.

The input signal through the delay line 18 is fed to. the input of the threshold element 19. The delay line 18 provides a delay of the signal for the duration of its passage in filter 3 and the differential block 4. The choice of the threshold value of the threshold element 19 depends on the type of nonlinear element used. In the general case, the threshold value Ugj (can be determined from the condition dU / dUg., 1, where

out

ki;

and

9b “ex

in the case of multistage nonlinear converters, the threshold value corresponds to the drop point from the stage corresponding to

97145

the transfer coefficient of the nonlinear element K 1, to a step with K 1. For 0.5, the threshold value

 0.2-0.25 UA, o, Kc, where U l ,, ks is the maximum swing of the input signal.

In case the input signal size does not exceed the threshold of the threshold element 19, then the first input of the OR OR 20 signal is logical O, and the first input of the AND 21 logical 1 element. Then the information on the control inputs of the switch 10 depends on output signals CJS of threshold elements 5, 6, 16 and 17. Signals from the output of filter 3 and from the additional output of delay line 1 are fed to differentiating blocks 4 and 15. The signal delay on part of delay line 1 ensures that the signals at the inputs coincide in time differentiating units 4 and 15. In threshold elements 16 and 6, threshold elements 17 and 5 are set respectively

5 thresholds of 35 and (gpe S -. Rms noise level). The threshold elements 5 and 6 are designed to detect in the signal fronts of single video pulses

0 short duration. The use of filter 3 increases the noise immunity of detection, and the threshold elements 16 and 17 are designed to detect the components of group (periodic) image structures in the frequency range lying above the cut-off frequency of filter 3.

At the combined direct outputs of threshold elements 6 and 1.6, a logical 1 signal appears in the case of detecting a signal from contrasting fine details, the video signal from which exceeds 38. The signal from the input of the switch 10

5 switches to the input of the first adder 11, i.e. the signal from the contrasting fine details undergoes non-linear conversion. In the case when the signal amplitude of the high-frequency components lies in the range of about - 38, i.e. The threshold value of threshold elements 17 and 3 is exceeded, but the value of 3 5 threshold of threshold 5 of threshold elements 16 and 6 is not exceeded, the logical O signal is present at the output of the OR 20 element, and the logical

Claims (1)

Claim Gradation distortion correction apparatus, comprising: 'a first delay line, to the input of which via a serially coupled first low pass filter and a first differentiator ₄₅ podklyuche- us inputs of the first and second threshold There are 145 elements, the input of the first delay line being the input of the device, the output of the first delay line connected through the second delay line to the first input and through the second low-pass filter to the second input of the subtraction unit, the output of which is connected to the input of the switch, the first output of which is connected to the first the input of the first adder, the second input of which is connected to the second input of the subtraction unit, and the output through a non-linear block is connected to the first input of the second adder, the second input of which is connected to the second output of the switch, and the output is the output of the device, the additional output of the first delay line through the second, differentiating unit is connected to the inputs of the third and fourth threshold elements, the direct outputs of the first and second threshold elements are combined, respectively, with the direct outputs of the fourth and third threshold elements, which, in order to increase correction accuracy, a third delay line, a fifth threshold element, an AND element, and an OR element are introduced into it, wherein the input of the first delay line through the third delay line is connected to the input a large threshold element, the direct output of which is connected to the first input of the OR element, the second input of which is connected to the direct output of the third threshold element, and the output is connected to the first control input of the switch, the second control input of which is connected to the output of the element AND, the first, second, third and the fourth inputs of which are connected respectively to the direct output of the first and inverse outputs of the second, third and fifth threshold elements.