JPH02121575A - Contour emphasizing circuit - Google Patents

Abstract

PURPOSE:To suppress a ringing or noise component that deteriorates the picture quality by providing a non-linear circuit having core ring characteristics and clipping characteristics in the low and high level areas of an input signal respectively into a secondary differentiating circuit. CONSTITUTION:A contour emphasizing signal generating circuit consists of a differentiating circuit 10, a polarity inversion amplifier 11, a level control variable amplifier 12, a non-linear amplifier 13, and a differentiating circuit 14 which are connected in series. The output of the circuit is connected to an addition circuit 15, and the output of the circuit 15 is connected to a terminal 2. The amplifier 13 has the 5-broken line characteristics whose gains are reduced in the low and high level areas of an input signal. Thus the amplifier 13 amplifies only the signal components set within a prescribed level range of a primary differential signal B and suppresses the ringing, the noises, and the excessive component that cause the deterioration of picture quality of a video receiver.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is applicable to the screen of a video receiving device such as a television receiver using a cathode ray tube. This relates to a contour enhancement circuit that improves sharpness.

[Summary of the invention]

The present invention provides an edge enhancement circuit that improves the sharpness of the screen of a video receiving device such as a television receiver using a cathode ray tube. By providing a nonlinear circuit having a coring characteristic in the low level region of the input signal and a clipping characteristic in the high level region of the input signal in the above-mentioned contour enhancement circuit section that adds the input signal and the video output signal, or In the contour enhancement circuit section, which supplies the signal obtained by passing the input video signal through a first-order differentiation circuit to the deflection speed modulation means of the cathode ray tube, a coring characteristic is set in the low level range of the input signal, and a clipping characteristic is set in the high level range of the input signal. By providing the nonlinear circuit having the above-mentioned nonlinear circuit, it is possible to obtain a video signal in which ringing and noise generated in the circuit before the contour emphasis circuit are suppressed in the input video signal, and the contour is emphasized. Furthermore, even when a sharp change in the video signal or a high-intensity video signal is input, it is possible to obtain a video signal with edge enhancement that does not contain excessive signal components.

(Prior Art) In general, the spatial frequency characteristics of a cathode ray tube in a video receiving device such as a television receiver, that is, the characteristics when a video signal is converted into a two-dimensional image, have low-pass filter characteristics, and the input video signal When compared with the actual screen of the video receiving device, the brightness change characteristics of the screen are less steep than the characteristics of the input video signal. The following methods (1) and (2) are used to correct the above-mentioned spatial frequency characteristics, improve the sharpness of the screen of the video receiving device, and further enhance the contours.
The method described in (3) and (3) is known.

(1) In FIG. 8, an input video signal A is input to a differentiator circuit 10 and an adder circuit 15 via an input terminal l. The input video signal A is differentiated twice in a differentiating circuit 10 and a differentiating circuit 14 connected in series, and is then differentiated from the above input video signal A by an adding circuit 15 via a polarity inverting amplifier 11 and a level adjustment circuit 12. The signals are added together and sent to the output terminal 2 as a video output signal F.

The waveforms of the signals of each component circuit, such as the input video signal A at this time, are shown in the ninth section. The second-order differential signal C is an acceleration component of the human-powered video signal A at portions P1, P2, P3, and 24 of the waveform of the human-powered video signal A. Therefore, the video output signal F to which this acceleration component has been added is the input video signal A.
Compared to the above, the video signal has preshoot and overshoot added at the Pl, P2, P3 and 24 sections.

When the video output signal F subjected to the series of processes described above is used as a cathode ray tube video signal, the outline of the screen of the video receiving device is emphasized.

(2) In the sharpness improvement circuit technology disclosed in Japanese Patent Application Laid-Open No. 52-132727, a non-linear amplifier whose gain decreases as the cough level increases for input signals of a predetermined level or higher is used. The input video signal is amplified by the non-linear amplifier, and this amplified signal is combined with the signal obtained through the second-order differentiator circuit (in front of the differentiator circuit 10 in FIG. 8). The input video signal is added and the added signal is used as a video signal.

When the video output signal F that has been subjected to the series of processes described above is used as a cathode ray tube video signal, for input video signals below a predetermined level, the screen of the video receiving device is The contours of the input video signal are emphasized, and the amount of change in the input video signal is suppressed for input video signals of a predetermined level or higher. This prevents the saturation phenomenon of the video output amplifier circuit from occurring.

(3) There is a method of modulating the deflection speed of the cathode ray tube using a signal obtained from an input video signal through a first-order differentiator circuit, thereby apparently improving the above spatial frequency characteristics and emphasizing the outline of the screen of the video receiving device. For example, in addition to main deflection scanning by a deflection yoke, there is a so-called electrostatic deflection velocity modulation method in which the output signal of the above-mentioned first-order differentiator circuit is supplied to the electrodes of a cathode ray tube to deflect the electron beam, or the output signal of the above-mentioned first-order differentiator circuit is supplied to the electrodes of a cathode ray tube to deflect the electron beam. There is a so-called electromagnetic deflection velocity modulation method in which an electron beam is deflected by supplying it to a velocity modulation coil (VM coil). Both of the above deflection speed modulation methods utilize the fact that the position of light emission is moved by modulating the speed of deflection. In other words, the brightness of a cathode ray tube screen is proportional to the beam current and inversely proportional to its scanning speed, so if the beam current is constant, a fast scanning speed will make the screen darker, and conversely, a slower scanning speed will make the screen brighter. It uses the principle of

[Problem to be solved by the invention]

In the conventional techniques described above, it is possible to obtain a certain degree of sharpness improvement effect using any of the methods, but if there is ringing or noise generated in the circuit before the contour enhancement circuit in the input video signal, Even this unnecessary noise is emphasized and included in the video signal after contour emphasis.

Furthermore, if a sharp change in the video signal or a high-intensity video signal is input, the video signal after edge enhancement will contain excessive signal components.

[Means to solve the problem]

The first invention related to the present application is a contour enhancement circuit that adds an input video signal and a signal obtained from the input video signal through a second-order differentiation circuit to obtain a video output signal. The present invention is characterized in that a nonlinear circuit having coring characteristics in the low level region of the input signal and clipping characteristics in the high level region of the input signal is provided in the differentiating circuit section.

A second invention according to the present application is a contour enhancement circuit for supplying a signal obtained by passing an input video signal through a first-order differentiating circuit to a deflection speed modulation means of a cathode ray tube, in which the input signal is It is characterized by the provision of a nonlinear circuit that has coring characteristics in the low level range and clipping characteristics in the high level range.

[Effect]

It is possible to perform edge enhancement in an input video signal by suppressing ringing and noise generated in the circuit before the edge enhancement circuit. Furthermore, even when a sharp change in the video signal or a high-intensity video signal is input, contour enhancement can be performed without including excessive signal components.

〔Example〕

Embodiments of the contour enhancement circuit according to the present invention will be described below with reference to the drawings.

Embodiment (1) In FIG. 1, terminal l is an input terminal for a video signal,
The circuit that generates the 0-contour emphasis signal, which is connected to the circuit that generates the contour emphasis signal and the addition circuit 15, is the differentiating circuit 10.
, a polarity inverting amplifier 11, and a variable amplifier 1 for adjusting the level.
2. A nonlinear amplifier 13 and a differentiating circuit 14 are connected in series, and the output thereof is connected to the above-mentioned adding circuit 15, and the output of the adding circuit 15 is connected to terminal 2. Note that the nonlinear amplifier 13 is a differentiating circuit 10.
and the differentiating circuit 13.

The waveforms in FIG. 2 are signals of each component circuit shown in FIG. 1, and the alphabets in FIGS. 1 and 2 indicate the correspondence between signals and waveforms.

Input video signal A is input to a differentiator circuit 10 and an adder circuit 15 via an input terminal l. By the way, the input video signal A
As shown in FIG. 2, the input video signal A is differentiated in the zero-order differentiating circuit 10, which always has ringing and noise at the rising portion PI and falling portion P4 of the normal waveform. In Fig. 2, the waveform of the first-order differentiated signal is shown in B. This first-order differentiated signal B includes the differentiated components of the ringing and noise described above, and this component is due to the image quality of the video receiving device. This is a factor that causes deterioration. Furthermore, if the first-order differential signal B contains a component above a predetermined level, the relationship between this component and the dynamic range of the cathode ray tube will cause the image quality to be similar to the defocusing of the screen of the video receiving device. This first-order differentiated signal is sent to the polarity inverting amplifier 1, which causes the deterioration.
1 and a level adjustment circuit 12 to a nonlinear amplifier 13.

By the way, as shown in FIG. 3, this nonlinear amplifier 13 has a five-fold line characteristic in which the gain decreases in the low level region and high level region of the input signal, and the signal component in the predetermined level range of the above-mentioned first-order differentiator B The waveforms in FIG. 3 schematically show the relationship between the input and output waveforms of the nonlinear amplifier. Therefore, the output waveform has a blunt shape in the low level range and high level range of the input signal. In other words, the above-mentioned causes of image quality deterioration are suppressed. Note that this nonlinear characteristic is obtained by connecting the coring circuit and the clipping circuit in series, for example, by using the characteristic (a) of a so-called coring circuit in the low level range and the characteristic (b) of a clipping circuit in the high level range. It can be realized by combination.

This nonlinear amplified signal is sent via the differentiating circuit 14 to the adding circuit I5. The above nonlinearly processed signal C is differentiated in the differentiation circuit 14, and becomes a relatively smooth contour emphasis signal F that does not contain ringing, noise, and excessive components compared to a conventional contour emphasis signal that is not subjected to nonlinear amplification. .

In the adder circuit 15, the input video signal A and the cough ring emphasis signal F are added together and sent to the terminal 2 as an output video signal. That is, this output video signal is a video signal that has preshoot and overshoot characteristics in the PI, P2, P3, and 24 portions of the input video signal A compared to the input video signal A, and is not subjected to conventional nonlinear amplification. This results in a relatively smooth video signal that does not contain ringing, noise, and excessive components compared to the video signal.

When this contour-enhanced signal is used as a cathode ray tube video signal, it is possible to effectively emphasize the contours of the screen of the video receiver and to suppress deterioration in image quality due to ringing and noise in the input video signal. In addition, there are characteristics derived from the characteristics of actual differentiating circuits, that is, even if the signal changes are the same, when differentiated, the value of the differentiated result becomes large for high-level signals, and the excessive value of human-powered video signals. By using the nonlinear amplifier to talimp the excessive differential value caused by such changes, the image signal after contour enhancement can be suppressed within the dynamic range of the cathode ray tube, and a good signal that does not suffer from deterioration similar to defocusing can be achieved. You can get better image quality.

Incidentally, in this embodiment, the nonlinear amplifier is placed before the second differentiating circuit 14, but the same effect can be obtained even if it is placed after the second differentiating circuit 14.

Next, a specific circuit of the nonlinear amplifier will be explained. Fourth
The figure shows a specific circuit configuration of the above-mentioned nonlinear amplifier. The video signal is passed through a terminal 30 to a common connection point of the emitter resistors of a coring circuit made up of transistors 3I and 32, and is connected to a differential amplifier with clipping characteristics (which amplifies the positive range) made up of transistors 33 and 34. ), and is input to a differential amplifier (amplifying the negative range) with clipping characteristics, which is composed of transistors 35 and 36.

The bases of the transistors 31 and 32 of the coring circuit are connected to each other and a bias voltage 50 is applied to them, and have a characteristic that the gain decreases as the signal level decreases in a relatively low level range. Also,
The above two differential amplifiers have a characteristic that the gain decreases as the signal level increases in a relatively high level range.

Next, the signals nonlinearly amplified in the coring circuit and the differential amplifier are added together as positive and negative signals in an adder circuit composed of a transistor 38 and a transistor 39, and outputted to a terminal 43 via a buffer amplifier. Ru.

The characteristics obtained by combining the coring circuit length and the differential amplifier described above have the characteristics shown in FIG.

Note that FIG. 5 shows the characteristics at the emitter of the transistor 42 in FIG. 4, and only shows the range in which the human input signal is positive. The gain characteristic of this nonlinear amplifier is similar to the five-fold line characteristic described above, and has a characteristic that the gain decreases in the low level region and high level region of the input signal. The outline of the screen of the receiving device is emphasized, and deterioration in image quality due to ringing and noise of the input video signal can be suppressed. Furthermore, even in the case of excessive changes or high levels of the input video signal, the edge enhancement can be performed without exceeding the dynamic range of the cathode tube, and without causing image quality deterioration similar to defocusing.

Embodiment (2) Next, an embodiment of the contour emphasizing circuit of the deflection velocity modulation method, which is the second invention described in the claims, will be described.

FIG. 6 shows a specific configuration of the contour emphasizing circuit for the deflection velocity modulation method. Terminal 50 is an input terminal for input video signals. The input terminal 50 includes a first-order differential circuit 52, a nonlinear amplifier 53,
An amplifier 54 and a speed modulation coil 55 are connected in a series connected circuit.

Note that the characteristics of the nonlinear amplifier 53 are as described in Example (1) above.
The input video signal, which has the characteristics of a circuit in which a coring circuit and a clipping circuit are connected in series, is differentiated by a first-order differentiating circuit 52 via a terminal 50 and an amplifier 51.

This differentiated signal is the velocity component of the input video signal, 0
Next, this differentiated velocity modulation signal is processed by the nonlinear amplifier 53 described above to suppress ringing and noise components in the differentiated signal, and to suppress the above-mentioned noise components derived from excessive changes in the video signal or high-level video signal input. The over-differentiated component is clipped. The velocity modulation coil 55 is excited by the velocity modulation signal in which components unnecessary for contour enhancement are suppressed, and the deflection velocity is modulated. Through the series of processes described above, the outline of the screen of the video receiving device is emphasized, and deterioration in image quality due to ringing and noise of the input video signal can be suppressed. Furthermore, even in the case of excessive changes or high levels of the input video signal, the edge enhancement does not exceed the dynamic range of the cathode tube, and effective edge enhancement can be performed without causing image quality deterioration similar to defocusing.

In this embodiment, the nonlinear amplifier is placed after the differentiating circuit, but the same effect can be obtained even if it is placed before the first-order differentiating circuit 63 as shown in FIG.

This embodiment describes a specific example in which the present invention is applied to a so-called electromagnetic deflection velocity modulation method. However, the present invention is applied to a so-called electrostatic velocity modulation method, and a cathode ray tube's velocity modulation electrode (for example, the fourth A similar effect can be obtained by supplying the above speed modulation signal to the electrode.

〔effect〕

By using the edge enhancement circuit according to the present invention, when edge enhancement is applied to the screen of a video receiving device such as a television receiver, the image signal that exists in the edge-enhanced video signal or the signal controlling deflection velocity modulation can be used. Ringing and noise components, which cause deterioration of screen image quality, are suppressed, allowing for excellent edge enhancement. Furthermore, the level of the video signal subjected to the above-mentioned edge enhancement can be suppressed within the wide range of the cathode ray tube, and edge enhancement can be performed without causing image quality deterioration similar to defocusing.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of a contour emphasizing circuit according to a first embodiment of the present invention, FIG. 2 is a waveform diagram in the contour emphasizing circuit, and FIG. 3 is a diagram of a nonlinear amplifier constituting the contour emphasizing circuit. Figures 4 and 5 are a specific circuit diagram and its characteristic diagram of the nonlinear amplifier, and Figure 6 is the second diagram of the present invention.
7 is a block circuit diagram of another embodiment of the present invention, FIG. 8 is a block circuit diagram showing a conventional example, and FIG. 9 is a waveform diagram thereof. l O・ 13 ・ 14 ・ 15 ・ 52 ・ 53 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ . Waveform! Figure 3: Nuri Tomoe Special Pillar Figure 5: Block circuit diagram of Saku Z's Shishitanori Figure 6: One-color actual sales daJme pro-tsuku circuit diagram Figure 7: Figure 8: Figure 9

Claims (2)

[Claims] (1) In a contour enhancement circuit that adds an input video signal and a signal obtained from the input video signal via a second-order differentiator circuit to produce a video output signal, the second-order differentiator circuit section is 1. An edge enhancement circuit comprising a nonlinear circuit having coring characteristics in a low level region and clipping characteristics in a high level region. (2) In the contour enhancement circuit that supplies the signal obtained by passing the input video signal through the first-order differentiating circuit to the deflection speed modulation means of the cathode ray tube, the first-order differentiating circuit has a coring characteristic in the low level region of the input signal. What is claimed is: 1. A contour emphasizing circuit comprising: a nonlinear circuit having clipping characteristics in a high level region.