RU2120193C1 - Corrector of video signals - Google Patents

Abstract

FIELD: TV equipment, in particular, TV sets. SUBSTANCE: device has low-frequency filter and electronic commutator. In addition device has introduced image contour detector and pulse generator. EFFECT: decreased noise and image redundancy without loss of horizontal resolution. 4 dwg

Description

 The present invention relates to television technology (using interlaced, interlaced, spiral and other scans) and can be used in broadcast television receivers, monitors for applied television systems, video recorders, transmitting television cameras and other components of broadcast and applied television systems.

 The well-known "Nonlinear Television Image Clarity Corrector" according to ed. St. USSR N 1140269, in which the reduction of image noise is provided by a low-pass filter with an adjustable upper cutoff frequency, which is controlled by a signal representing a rectified high-frequency component of the spectrum of the video signal.

 A disadvantage of the analogue is the impossibility of reducing the noise level of images of real practical interest that contain, in addition to the background, any details. Another disadvantage of the analogue is the impossibility of reducing the physiological redundancy of images, since the elimination of small non-essential details from an image will inevitably be accompanied by a significant deterioration in horizontal sharpness relative to large image parts, leading to an unacceptable deterioration in its quality.

 The closest in technical essence and the largest number of matching distinctive features analogue is "Device for correcting the clarity and sharpness of a television image" according to ed. St. USSR N 1188904, in which the operating mode is switched depending on the content of the image: to reduce the noise level of the image that does not contain sharp details (i.e., the image that is not of practical interest due to the lack of any information in it), using a filter low frequencies it suppresses high and medium frequencies of the spectrum of the video signal; during processing of the video signal corresponding to the image with large sharp details, using the low-pass filter in it only high frequencies of the spectrum of the video signal are suppressed; and during the processing of the video signal corresponding to the image with small sharp details, with the help of a high-pass filter in it, the high frequencies of the spectrum of the video signal are raised.

 The disadvantage of the prototype is the impossibility of using it to reduce the noisiness of images of real practical interest that contain, in addition to the background, any details. Another disadvantage of the analogue is the impossibility of reducing the physiological redundancy of images, since the elimination of small non-essential details from the image will inevitably be accompanied by a significant deterioration in sharpness relative to large parts of the reproduced image, leading to an unacceptable deterioration in its quality.

 The invention solves the problem of reducing the noise and physiological redundancy of a television image without deteriorating its horizontal sharpness by composing the output video signal from fragments of the input video signal with significantly attenuated high-frequency and mid-frequency spectral components corresponding to the inter-contour portions of the image and fragments of the undistorted original video signal corresponding to the contours of relatively large large image parts .

 The solution is achieved by the fact that in the inventive video signal corrector containing a low-pass filter (LPF) and an electronic switch, series-connected image loop detector and pulse shaper are introduced, the output of which is connected to the control input of the electronic switch, the first and second signal inputs of which are connected respectively to the output of the low-pass filter and to the interconnected inputs of the image contour detector and the low-pass filter, the input of the image contour detector is the input of the video signal corrector, in swing corrector is an electronic switch output.

 The distinguishing features listed above are significant because their absence does not allow us to solve the task, and their presence, on the contrary, ensures its achievement. Indeed, the introduction of the image contour detector and the pulse shaper into the claimed video signal correction unit allows, while maintaining undistorted fronts of the original video signal corresponding to the image contours, to significantly smooth out sections of the video signal corresponding to the image contour intervals and thereby significantly suppress high-frequency noise and remove noise-like small ones from the image details, i.e., reduce the physiological redundancy of the image.

 The invention is illustrated by drawings, which depict: in FIG. 1 - an example implementation of the inventive device; in FIG. 2 is another example implementation of the inventive device; in FIG. 3 is a diagram explaining the operation of FIG. 1 implementation of the inventive device; in FIG. 4 is a diagram explaining the operation of FIG. 2 implementation of the inventive device.

 The inventive video signal corrector, a functional diagram of which is shown in FIG. 1 includes an electronic switch 1 (of any known implementation), to the first signal input of which an output of a low-pass filter 2 is connected (of any known implementation), an input of a low-pass filter 2 is connected to a second signal input of an electronic switch 1, and an electronic electronic control input switch 1 through a series-connected detector 3 loops of the reproduced image (for example, in the form of series-connected differentiating circuit, push-pull rectifier and comparator, or in the form of series the integrating circuit and the logic circuit (Exclusive OR ", to the other input of which the input of the integrating circuit is connected) and the shaper of 4 pulses (for example, in the form of a comparator or a monovibrator with restart) are connected to the input of the low-pass filter 3.

 The inventive video signal corrector, a functional diagram of which is shown in FIG. 2, differs from its previous implementation by the presence of an additional circuit component — the sampling and storage unit 5. To the signal input of the node 5 sampling and storage connected to the input of the filter 2 low pass. The output of the detector 3 of the image contours is connected to the control input of the sampling and storage unit 5. The output of the node 5 sampling and storage is connected to the second signal input of the electronic switch 1.

 It should also be borne in mind that all schemes are presented in a simplified form, i.e., in practical implementation, they may contain additional nodes (for example, the elements of the inputs and outputs of adjacent nodes in terms of polarity, time, level, etc.).

 The inventive video signal corrector, a functional diagram of which is shown in FIG. 1, works as follows. If at its current input moment the video signal values (Fig. 3a) correspond to the image contours (time intervals t0t1, t2t3, t5t6 in Fig. 3a), pulses (Fig. 3b) of the same magnitude appear at the output of the detector 3 of the image contours and polarity, the length of which is equal to the duration of the corresponding fronts of the input video signal (Fig. 3A). The leading edges (i.e., at time instants t0, t2, t5) of these pulses start the pulse shaper 4 (for example, as a monovibrator with a restart) of a longer duration, which is equal to the duration of the edges of the video signal at the output of the low-pass filter 2 (i.e. duration t2t4 and t5t7 in Fig. 3B). The latter, fed to the control input of the electronic switch 1 (at time intervals t0t4, t5t7 in Fig. 3d), ensures the passage to its output (Fig. 3d) of the original video signal (Fig. 3a). At other time instants (i.e., earlier t0, inside t4t5 and later t7), corresponding to the inter-contour sections of the image, there are no pulses at the outputs of the detector 3 of the image contours (Fig. 3b) and the pulse shaper 4 (Fig. 3d) and therefore the output electronic switch 1 at these times passes a video signal (Fig. 3B) from the output of the low-pass filter 2. As a result of this processing of the original video signal, the smoothing of sections of the video signal corresponding to the contour sections of the image is ensured, while maintaining the original slope of the edges corresponding to the image contours, i.e. ultimately reducing noise and physiological redundancy of the image.

 The inventive video signal corrector, a functional diagram of which is shown in FIG. 2, works as follows. If at its input at the current moment of time that part of the input video signal (Fig. 4a), which corresponds to the contour sections of the image (i.e., before the moment t0, inside the interval t4t5 and later than the time t7), is output (Fig. 4e), as in the previous implementation, the signal (Fig. 4d) from the output of the low-pass filter 2 passes to the output of the electronic switch 1. The rest of the time (i.e., at time intervals t0t4, t5t7), the output signal (Fig. 4f) is generated in a manner different from the previous implementation. Namely, in that part of these time intervals (t0t4, t5t7), which directly corresponds to the reproduction of the image contours (i.e., at time intervals t0t1, t2t3, t5t6), to the output (Fig. 4e) of the claimed video signal correction block through the node 5 of the sample and storage and the electronic switch 1 passes the original video signal (Fig. 4A). The rest of the time (i.e., at time intervals t1t2, t3t4, t6t7) of the durations of the edges of the video signal at the output of the low-pass filter 2 (i.e. t0t2, t2t4, t5t7) is transmitted to the output of the electronic switch 1 from the output of the sample node 5 and storage (Fig. 4c), which at these time intervals (t1t2, t3t4, t6t7) corresponds to the values of the input video signal (Fig. 4a) at time instants (t1, t3, t6) equal to the final values of its edges.

 The introduction into the inventive device of the distinguishing features listed in the claims makes it possible, by smoothing with a low-pass filter and a sampling and storing unit, only those parts of the input video signal that correspond to the contour sections of the image, while maintaining the remainder of the video signal unchanged, to ensure effective noise reduction and reduce the physiological redundancy of video information without compromising the horizontal sharpness of the image, and thereby significantly increase the comfort of watching television images.

Claims (1)

 A video signal corrector comprising a low-pass filter (LPF) and an electronic switch, characterized in that a series-connected image loop detector and a pulse shaper are introduced into it, the output of which is connected to the control input of the electronic switch, the first and second signal inputs of which are connected respectively to the output of the LPF and to the interconnected inputs of the image contour detector and the low-pass filter, the input of the image contour detector is the input of the video signal corrector, the output of the corrector i wish to set up an electronic switch output.

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