JP2938258B2 - Image quality correction circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in image quality correction of, for example, a TV, and more particularly to an image quality correction circuit which improves the quality of a signal to be corrected.

[0002]

2. Description of the Related Art As is well known, there are various methods of image quality correction, and some methods improve the correction effect and the quality of a signal to be corrected. FIG. 3 shows a conventional image quality correction circuit. Hereinafter, FIG. 3 will be described with reference to FIG. 4 showing output signals of respective units in FIG.

In FIG. 3, reference numerals 1 to 4 denote delay groups having the same group delay.
Line. The amplifier 5 calculates the difference between the input Yin of the delay line 1 and the output C of the delay line 2, and the amplifier 6 calculates the difference between the output C of the delay line 2 and the output E of the delay line 4. Reference numeral 8 denotes a difference between the outputs F and H of the amplifiers 5 and 6.

The output I of the amplifier 8 is a secondary differential signal of the input signal Iin of the image quality correction circuit. The amplifier 7 calculates the difference between the output B of the delay line 1 and the output D of the delay line 3. The output G of the absolute value circuit 9 which takes the absolute value of the output of the amplifier 7 and the output I of the amplifier 8 are multiplied by a multiplication circuit 1
The output J is supplied to the amplifier 11. The output J of the multiplication circuit 8 is a narrow second derivative signal.

The output J is added to the input signal Yin of the delay line 1 as the original signal by adding the secondary differential signal and the signal C delayed in time through the delay lines 1 and 2 by the amplifier 11. It can be seen from the waveform at the output L of the amplifier 11 that the rising and falling, that is, the sharpness of the edge is improved.

As described above, the correction output of the conventional circuit is shown in FIG.
Of the output L. Looking at the waveform of this output L, it can be seen that undulations at edges not present in the original signal, that is, pre-shoots and overshoots occur. If the preshoot and the overshoot have a large amplitude and a large width, adverse effects such as a screen glare occur.

As an example of improving the sharpness of the edge, the second derivative signal of the output I in FIG.
To be added to the output C. This method is the most basic among the image quality correction circuits using a relay line. According to this method, the amplitude and width of the pre-shoot and the overshoot are larger than those of the above-described correction method, and the above-described adverse effects are increased. The conventional image quality correction circuit described above converts the secondary differential signal of the output I in FIG.
Direct addition to the output C of the delay line 2. Compared with the basic method, the pre-shoot and overshoot amplitudes are reduced to about 1/2, and the widths thereof are reduced to about 3/4, to bet to reduce the above-mentioned adverse effects. Things.

However, reducing the amplitude of the pre-shoot and the overshoot to about 1/2 does not provide a value for performing satisfactory image quality correction, and also requires an absolute value circuit 9 for rectifying the output of the amplifier 7. Therefore, the circuit configuration is complicated.

[0009]

As described above, in the conventional image quality correction circuit, the amplitudes of the pre-shoot and the overshoot are reduced to １ ／ as compared with the basic correction method, and a satisfactory reduction is achieved. Not only the value but also the circuit configuration was complicated.

An object of the present invention is to provide an image quality correction circuit which not only has a simple circuit configuration but also reduces pre-shoot and overshoot.

[0011]

An image quality correction circuit according to the present invention is configured such that an output signal of a preceding circuit is input to an input of a first delay line, and a first delay line is input to an input of a second delay line. , The input of the third delay line is connected to the output of the second delay line, and the input of the fourth delay line is connected to the output of the third delay line.

Further, a first amplifier which takes a difference between an input of the first delay line and an output of the second delay line, an output of the second delay line and a fourth delay line.
A second amplifier that takes the difference between the outputs of the lines, a third amplifier that takes the difference between the output of the first delay line and the output of the third delay line, and the output of the first amplifier and the second A fourth amplifier for taking the difference between the outputs of the amplifiers;
The first and second outputs of the first and fourth amplifiers, respectively.
Multiplying circuit, a second multiplying circuit having an output of the third amplifier and an output of the first multiplying circuit as inputs, and a second multiplying circuit for obtaining a difference between an output of the second delay line and an output of the second multiplying circuit. And an output of the fifth amplifier as a correction output.

[0013]

According to the above-mentioned means, the output of the third amplifier is applied to the fourth amplifier for obtaining the narrow second-order differential signal by a multiplying circuit. The amplitude can be reduced to half that of the conventional means.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit diagram showing one embodiment of the present invention. An input signal Yin, which is the same as that shown in FIG. 3 with the same reference numeral, is supplied to the input terminal of the delay line 1 and the positive input terminal of the amplifier 5 at point a in FIG. At the point b, the output signal of the delay line 1 is supplied to the input terminal of the delay line 2 and the positive input terminal of the amplifier 7. At the point c, the output signal of the delay line 2 is supplied to the input terminal of the delay line 3, the negative input terminal of the amplifier 5, and the positive input terminal of the amplifier 6. At a point d, the output signal of the delay line 3 is supplied to the input terminal of the delay line 4 and the negative input terminal of the amplifier 7. At point e, the output signal of the delay line 4 is supplied to the negative input terminal of the amplifier 6.

The signal waveform in the above-described configuration will be described with reference to FIG. 2, where the horizontal axis represents time. 2A to 2E show signal waveforms at points a to e in FIG. a indicates the input signal Yin. b, c, d, and e indicate signal waveforms at points b, c, d, and e in FIG. 3, respectively. b, c,
Since signals d and e pass from the delay line 1 to the delay line 4 having the same group delay amount, the signals are delayed by the same time with respect to the input.

At points f, g and h in FIG. 1, the output f of the amplifier 5 which takes the difference between the signals at points a and c, and the output g of the amplifier 7 which takes the difference between the signals at points b and d, respectively. And the output h of the amplifier 6 which takes the difference between the signals at points c and e. In FIG. 2, the signal waveforms of the outputs f, g and h are indicated by corresponding symbols.

The positive input of the amplifier 8 is connected to the output of the amplifier 5,
The negative input of the amplifier 8 is connected to the output of the amplifier 6. The output i of the amplifier 8 and the output g of the amplifier 7 are multiplied by a multiplication circuit 12, and the output j of the multiplication circuit 12 is taken out at point j. From the above description, in FIG.
Is the second derivative signal of the input signal Yin.
The signal waveform at the point j in FIG. 1 is a narrow second-order differential signal like the waveform j in FIG. The waveform at this j point is the same as J in FIG. However, in the circuit of FIG. 3, since the output of the amplifier 7 is rectified through the absolute value circuit 9, the secondary differential signal of the output j when the input signal falls is the secondary differential signal of the circuit of FIG. The waveform is opposite to that of J.

In this embodiment, the output j of the multiplication circuit 12 for obtaining a narrow second derivative signal and the output g of the amplifier 7 are multiplied by the multiplication circuit 13, and the output k of the multiplication circuit 13 and the signal at the point c are differentiated. A correction output is obtained by adding the signals by the amplifier 14. Therefore, while having a narrow width, the amplitude can be reduced to half that of the conventional means.

As described above, as shown by the waveform k in FIG. 2, j has a small amplitude but has the same slope near the point crossing the time axis.
The output of the amplifier 14 from which the next differential signal can be obtained and from which the corrected output is extracted is obtained as the output Yout of FIG. 2 having a small pre-shoot and overshoot, even though the rising and falling slopes are the same. be able to.

[0020]

According to the image quality correction circuit of the present invention, instead of this absolute value circuit, a circuit having a high correction effect is provided by using a multiplication circuit which can be constituted by the same number of elements as the absolute value circuit. realizable.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a signal waveform diagram of a main part of FIG.

FIG. 3 is a conventional circuit configuration diagram.

FIG. 4 is a signal waveform diagram of a main part of FIG. 3;

[Explanation of symbols]

1-4 delay lines, 5-8, 14 differential amplifiers, 12, 13 multiplication circuits.

Claims (1)

(57) [Claims] 1. A first delay line having the same group delay amount and having an input of an output signal of a preceding circuit as an input, and a second delay line having an input connected to an output of the first delay line. A third delay line having an input connected to the output of the second delay line, and a fourth delay line having an input connected to the output of the third delay line; A first amplifier that takes a difference between an input of a first delay line and an output of the second delay line; and a difference between an output of the second delay line and an output of the fourth delay line. A second amplifier that takes a signal; a third amplifier that takes a difference between the output of the first delay line and the output of the third delay line; a signal that outputs the output of the first amplifier and the signal of the second amplifier. The fourth method to take the output difference A first multiplier for multiplying the output of the third amplifier by the output of the fourth amplifier; and a second multiplier for multiplying the output of the third amplifier by the output of the first multiplier. An image quality adjustment circuit, comprising: a multiplication circuit; and a fifth amplifier that takes a difference between an output of the second delay line and an output of the second multiplication circuit.