JPH06217166A - Outline correcting circuit - Google Patents

Abstract

PURPOSE:To attain a well-balanced outline correction by gain adjusting an outline signal, non-linear converting it, correcting it into a proper level, and adding it to an input luminance signal as the outline signal of proper level amounts in both opposite and negative directions. CONSTITUTION:When the luminance signal is inputted, the output signal of an outline signal forming circuit 2 is shown by a figure (b). Also, an input luminance signal (a) is shown by a figure (c) by the output signal of a non-linear circuit 3. The gain of an outline signal (b) is adjusted by a gain control circuit 4 by the luminance signal to which the non-linear processing is applied, and outputted as an outline signal (d). That is, the outline signal which is subject to a level dependent effect is obtained, inputted to a non-linear conversion circuit 8, and non-linear converted. Therefore, the input outline signal is non- linear converted so that the gain of a negative polarity can be increased, and the gain of a positive polarity side can be decreased, and the excessive input outline signal is non-linear converted so that the gain can be compressed. Thus, an outline signal (f) which is well-balanced in both the opposite and negative directions can be obtain.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour correction circuit for improving the image quality of a television signal or the like, and more particularly to a contour correction circuit for a television camera.

[0002]

2. Description of the Related Art As a conventional contour correction circuit, for example,
There is a circuit as shown in FIG. In FIG. 6, 1 is an input terminal to which a luminance signal is input, 2 is a contour signal forming circuit that creates horizontal and vertical contour signals, 3 is a non-linear circuit that performs non-linear processing on the input luminance signal, and 4 is an output of the non-linear circuit 3. Is a gain control circuit that changes the gain of the contour signal, 5 is an adder that adds the luminance signal and the gain-adjusted contour signal, 6 is an output terminal, and 7 is a delay circuit that adjusts the delay time of the circuit.

The operation of the contour correction circuit configured as described above will be described with reference to FIGS.

FIG. 7 is a diagram showing an example of the internal configuration of the contour signal forming circuit 2 of FIG. 6, in which 8 is a 1H (1 horizontal scanning period) delay circuit, 9 is a τd time delay circuit, and 10 is a circle. A coefficient unit that multiplies the values of the coefficients (2k1, 2k2, etc.), and 11 is an adder. Here, in the 1 V (1 field) period, as shown in FIG.
When the vertical luminance change signal shown in (a) is input,
The input luminance signal and each signal delayed for the 1H period and the 2H period are multiplied by the coefficients -k1, 2k1, -2k1 and added. By the calculation of this vertical contour signal section, the contour signal of the vertical signal shown in FIG. 8B is obtained. Similarly, assuming that the input signal changes in the horizontal luminance shown in FIG. 8C within the 1H period, the horizontal contour signal shown in FIG. can get. Therefore, a two-dimensional contour signal can be obtained by adding the horizontal contour signal portion and the vertical contour signal portion.

For simplification of the explanation with reference to FIG. 6, it is assumed that the contour signal forming circuit 2 has only the horizontal contour signal and the input luminance signal is obtained as shown in FIG. 9 (a). FIG. 9 (a)
6A to 6E are signal waveforms in the portions of FIGS. 6A to 6E.
Further, FIG. 9F is a diagram showing the input / output characteristics of the nonlinear circuit 3. The output signal of the contour signal forming circuit 2 is the luminance signal (a)
Is input, the display becomes as shown in FIG. Further, the non-linear circuit 3 processes the input luminance signal (a) as shown in FIG. 9 (c). The gain of the contour signal (b) is adjusted by the gain control circuit 7 by the luminance signal subjected to the non-linear processing, and the contour signal shown in FIG. 9D is output. In other words, where the level of the luminance signal is low, so-called level dependency is performed to reduce the gain of the contour signal, and the contour signal formed by the luminance signal in the dark portion, that is, the contour formed by the change in the luminance signal due to the noise component. The signal becomes small or becomes 0, so that deterioration of the S / N ratio is suppressed. The gain-controlled contour signal (d) and the input luminance signal (a) are delayed by the delay circuit 7 and then added by the adder 5, and the contour-corrected luminance signal (e) is output from the output terminal 6. You get more.

[0006]

However, in the above-described conventional contour correction circuit, since the luminance signal is subjected to the non-linear processing as it is and the gain of the contour signal is controlled by the signal, the contour signal shown in FIG. As shown in (e), the luminance signal may change abruptly to some extent, that is, the contour signal gains on the high level side and the low level side of the signal may be different, and the level dependent effect may be obtained. There is a problem that the contour signal becomes unbalanced. This is because, in particular, when the change of the input luminance signal is large as shown in FIG. 10, the gain control of the non-linear processing of the luminance signal as it is causes the contour signal portion in the negative direction to become small as shown in FIG. The contour signal part in the positive direction becomes large, and the imbalance is noticeable. In addition, it becomes unnecessarily large in the positive direction, which causes a visually uncomfortable feeling.

The present invention solves the above-mentioned problems.
An object of the present invention is to provide a contour correction circuit which retains the level dependent effect and obtains a contour signal in a well-balanced manner even when the change of the input luminance signal is large, and which does not cause a visual discomfort.

[0008]

In order to achieve the above object of the present invention, a contour signal forming circuit for forming a contour signal from a luminance signal or a signal similar to the luminance signal, and a gain for adjusting the gain of the contour signal. A control circuit, a contour signal non-linear conversion circuit that non-linearly converts the output signal of the gain control circuit, a delay circuit that delays the luminance signal for a predetermined time, an output signal of the delay circuit, and a contour signal output from the conversion circuit And an adder for adding and.

[0009]

In the contour correction circuit of the present invention having the above-mentioned structure, the contour signal is adjusted in gain, then the contour signal is subjected to non-linear conversion, and the contour signal is corrected to an appropriate level. In addition, it is added as a contour signal of an appropriate level amount.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the contour correction circuit of the present invention in one embodiment. In FIG. 1, 1 is an input terminal to which a luminance signal is input, 2 is a contour signal forming circuit that creates horizontal and vertical contour signals, 3 is a non-linear circuit that performs non-linear processing on the input luminance signal, and 4 is an output of the non-linear circuit 3. Gain control circuit to adjust the gain of contour signal by
5 is an adder for adding the delayed luminance signal and the contour signal whose gain is adjusted, 6 is an output terminal, 7 is a delay circuit for adjusting the delay time of the circuit, and 8 is a non-linear conversion circuit for non-linearly converting the contour signal. is there. 1 to 6 are the same as the conventional example of FIG.

The operation of the contour correction circuit of the present embodiment constructed as above will be described with reference to FIGS. For simplicity of explanation, consider only the contour signal in the horizontal direction. If the input luminance signal is input as shown in FIG. 2A, the output signal of the contour signal forming circuit 2 is as shown in FIG.
As shown in (b). Further, the non-linear circuit 3 processes the input luminance signal (a) as shown in FIG. The gain of the contour signal (b) is adjusted by the gain control circuit 4 by the luminance signal subjected to the non-linear processing, and is output as the contour signal shown in FIG. The contour signal is subjected to the so-called level dependent effect. The contour signal is input to the non-linear conversion circuit 8 to perform non-linear conversion as shown in FIG.

That is, a nonlinear conversion is performed such that the gain on the negative polarity side is large and the gain on the positive polarity side is small with respect to the input contour signal, and the gain is compressed for the excessive input contour signal. , Both the positive and negative shown in FIG. 2 (f) are balanced contour signals. The input luminance signal (a) is delayed by the delay circuit 7 by the delay time of each circuit, added by the contour signal (f) and the adder 5, and the result is shown in FIG.
A contour-corrected luminance signal indicated by is obtained from the output terminal 6.

As can be seen from FIG. 2 (g), the high-level side and the low-level side of the edge portion of the luminance signal are balanced with the same gain of the contour signal without being different from the conventional gain of the contour signal.

4 (a) and 4 (b) show an example of contour correction when the change of the input luminance signal is large, the gain on the high-level side is suppressed by the contour correction circuit of this embodiment. Therefore, there is no visual discomfort due to imbalance as in the conventional case (FIG. 10).

Needless to say, the same effect can be obtained by the above-mentioned method even when the contour correction in the vertical direction is taken into consideration.

Although the operation of the contour signal non-linear circuit is described in this embodiment, the contour signal non-linear circuit is constructed by a RAM as shown in FIG. 5 when the signal system is processed as a digital signal. The table 9 is used, and the non-linear characteristic of the microcomputer 10 is arbitrarily set by a RAM.
By writing in the table 9 and controlling by various methods, more optimal non-linear characteristics can be obtained and discomfort due to imbalance is eliminated.

Even if the nonlinear circuit 3 shown in FIG. 1 is not provided, the nonlinear conversion circuit 8 operates, and it is clear that the present invention has the effect. Further, in the above description, the contour signal is formed from the luminance signal, but as another method, the contour signal is formed from only the green signal, and this signal is generated for each of R (red), G (green), and B (blue). The present invention is also effective when the contour signal is formed by the so-called “Out of Green” method of mixing in the process amplifier. (For example, Hiroshi Marubayashi et al., "Contour compensator for planvicon color cameras" Sho 4
4.6.26, 14th Television system circuit research committee material) This "Out of Green" system is often used for cameras using an image pickup tube due to registration, circuit scale, and the like.

[0019]

As is apparent from the above description, according to the contour correction circuit of the embodiment of the present invention, even when the level dependent effect is applied, the edge portion of the signal is at the low level side (negative direction). A well-balanced contour correction can be performed without causing a gain difference between the contour signal and the contour signal on the high level side (forward direction), and the practical effect thereof is great.

[Brief description of drawings]

FIG. 1 is a block diagram of a contour correction circuit according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing waveforms in portions (a) to (g) of FIG.

FIG. 3 is a diagram showing a non-linear conversion characteristic of a non-linear conversion circuit 8 of FIG.

FIG. 4 is a diagram showing a waveform in the case where there is a large change in the luminance signal in FIG.

FIG. 5 is a block diagram of a contour correction circuit when configured using a microcomputer in FIG.

FIG. 6 is a block diagram of a contour correction circuit according to a conventional example.

FIG. 7 is an internal block diagram of a contour signal forming circuit 2.

FIG. 8 is a waveform diagram showing the internal operation of the contour signal forming circuit 2.

FIG. 9 is a waveform diagram showing waveforms in portions (a) to (e) of FIG.

FIG. 10 is a diagram showing a waveform in the case where there is a large change in the luminance signal in FIG.

[Explanation of symbols]

 1 Input Terminal 2 Contour Signal Forming Circuit 3 Nonlinear Circuit 4 Gain Control Circuit 5 Adder 6 Output Terminal 7 Delay Circuit 8 Nonlinear Conversion Circuit 9 RAM Table 10 Microcomputer

Claims (3)

[Claims] 1. A contour signal forming circuit for forming a contour signal from a luminance signal or a signal similar to the luminance signal, a gain control circuit for adjusting the gain of the contour signal, and a non-linear conversion of an output signal of the gain control circuit. A contour signal non-linear conversion circuit, a delay circuit that delays the luminance signal for a predetermined time, and an adder that adds an output signal of the delay circuit and a contour signal output from the conversion circuit. Contour correction circuit. 2. The contour correction circuit according to claim 1, wherein the gain control circuit non-linearly processes the luminance signal or a signal similar to the luminance signal and inputs it as a control signal of the gain control circuit. 3. The contour signal non-linear conversion circuit is composed of a RAM (random access memory) to which a contour signal whose gain has been adjusted is input, and data of the RAM can be arbitrarily rewritten by a microcomputer. The contour correction circuit according to claim 1.