JPH03245681A - Contour emphasis circuit for television display pattern - Google Patents

Abstract

PURPOSE:To realize the low cost and high performance by applying phase modulation to a clock signal at a prescribed period with a differentiating waveform of a luminance signal and expanding or contracting the time axis of digital R, G, B signals generated from a luminance signal and a color difference signal by a multiple of a ratio of periods of clock signals before and after phase modulation. CONSTITUTION:A digital luminance signal is fed to a differentiating circuit 11a and converted into an analog signal at a next-stage D/A converter circuit 11b and a clock signal of a prescribed period fed from an input terminal I4 is subject to pulse phase modulation by using an analog differentiating signal (E) outputted from the D/A converter circuit 11b at a clock phase modulation circuit 12. Thus, the phase-modulated clock signal CK' is generated by the phase modulation circuit 12 and fed to D/A converter circuits 14, 15, 16 together with the clock signal CK before phase modulation. Digital R, G, B signals outputted from a digital matrix circuit 13 of a prestage is converted into relevant analog R, G, B signals, while the time axis of the digital signals is extracted or contracted by a ratio of periods of clock signals before and after phase modulation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a circuit for enhancing the outline of a display screen installed in a television receiver.

(Prior Art) In television receivers, edge enhancement processing is performed to make the display screen clearer. One of these edge enhancement methods is a speed modulation method in which the scanning speed of an electron beam of a cathode ray tube is modulated by a differential waveform of a luminance signal. For details of this speed modulation method, please refer to the Japanese Patent Publication No. 55-211, if necessary.
Please refer to the specifications of No. 4 and Japanese Patent Publication No. 63-992.

Other edge enhancement methods include a method that uses a digital filter circuit to enhance high frequencies of luminance signals and color signals. Regarding the details of this high-frequency emphasis method using a digital filter circuit, please refer to Japanese Patent Publication No. 1-3 concerning the applicant's prior order as necessary.
Please refer to the specifications of Nos. 0347 to 30350.

(Problems to be Solved by the Invention) In the conventional contour enhancement method using speed modulation described above, a high voltage deflection system is operated. Large and expensive parts are required, resulting in high costs.

On the other hand, the conventional high-frequency emphasis method using a digital filter circuit described above is in line with the technological trend of converting an analog video signal into a digital signal and performing various image quality improvements such as Y/C separation and noise removal. ing. However, this high-frequency emphasis method has a problem in that it requires a relatively complex and expensive digital filtering circuit. Furthermore, the high-frequency emphasis method using a digital filter circuit has a problem in that characteristics are likely to deteriorate due to ringing.

(Means for Solving the Problems) The contour enhancement circuit for a television display screen according to the present invention creates an analog differential signal from a digital or analog luminance signal, and phase-modulates a clock signal of a predetermined period with this analog differential signal. and digital R, which is created from digital or analog luminance signals and color difference signals.
While expanding and contracting the time axes of the G and B signals by the ratio of the period of the clock signal before and after the phase modulation, each is converted into an analog R signal.
It is configured to convert into 2G and B signals.

That is, according to the contour enhancement circuit for a television display screen according to the present invention, expansion and contraction of the time axis similar to the conventional speed modulation method is performed within the digital video signal processing system, and this is performed within the deflection system. Compared to conventional technology, lower cost and higher performance can be achieved.

Also, what about the television program related to the present invention? The contour enhancement circuit for the main display screen is mainly composed of digital differentiating circuits and phase modulation circuits with simple configurations, so it is less expensive than conventional circuits that are mainly composed of digital filtering circuits with relatively complex configurations. Realized.

Hereinafter, the effects of the present invention will be explained in detail together with examples (Examples). FIG. I2 and I2 are input terminals for digital color difference signals (C1, C2), respectively, I4 is an input terminal for a clock signal (GK), 11 is an analog differential signal generation circuit, 12 is a clock phase modulation circuit, 13 is a digital matrix circuit, 14.15.16 is a time axis expansion/contraction/D/A conversion circuit, 09.0□, 0. is an analog R2G that constitutes a color display screen that has undergone contour enhancement processing,
This is the output terminal for the B signal.

The analog differential signal generation circuit 11 includes a digital differential circuit 11a that differentiates the digital luminance signal Y supplied via the input terminal 01, and a D/A converter circuit 11b that converts the output of the digital differential circuit 11a into an analog signal. It consists of

As illustrated in FIG. 2, the digital differentiation circuit 1 shown in FIG. It includes an adder 22 that adds signals, and outputs a differential waveform of the digital luminance signal supplied from the input terminal 20 to the output terminal 23.

Time axis expansion/contraction/D/A conversion circuits 14, 15, and 16 in Fig. 1
As shown in FIG.
, a main body portion 32 , and a low-pass filter circuit (LPF) 33 . The time axis expansion/contraction section 31 at the front stage is composed of a puffer memory 31a and a memory control circuit 31b. The main body section 22 at the rear stage has a well-known configuration including a combination of a switch, a resistor network, and a group of operational amplifiers.

The digital luminance signal Y and digital color difference signals C1 and C2 supplied to the input terminals 11=z and Is in FIG.
The analog video signal is sampled with a clock signal of a predetermined frequency (4fsc, etc.) and converted into a digital video signal, which is separated by Y/C, and the separated digital carrier color signal is demodulated into a digital color difference signal in a digital color demodulation circuit. 0 created by
The color difference signals C1 and C2 are any two of RY, G-Y, and BY. This digital luminance signal Y
and digital color difference signals C1, C2 are digital R, G, B (R
The three primary colors (ed, green, and blue) are converted into signals.

As shown in Figure 4, the original analog luminance signal is shown in waveform (A).
A clock signal CK with a predetermined period for sampling during D/A conversion is shown as an example in waveform (B).

In this case, the digital luminance signal supplied to the input terminal I has a waveform (C). however,
This waveform (C) is displayed in the form of discrete sampling data before conversion to 200 million signals so that the change in amplitude can be seen at a glance. By supplying this digital luminance signal to the differentiation circuit 11a, a digital differentiation signal shown in waveform (D) is created. This digital differential signal is converted into an analog signal by the next-stage D/A conversion circuit 11b, thereby creating an analog differential signal shown in waveform (E).

In the next stage clock phase modulation circuit 12, the clock signal CK of a predetermined period supplied from the input terminal I4 is pulse phase modulated by the analog differential signal (E) outputted from the D/A conversion circuit 11b.

This pulse phase modulation is also called pulse position modulation (PPM), and is well known as one of the most basic pulse modulation methods, along with pulse amplitude modulation (PAM) and pulse width modulation (PWM).

When the polarity of the modulating signal shown in waveform (E) is positive, the phase of the modulated signal (B) advances in proportion to its amplitude, and when the polarity of the modulating signal is negative, it advances in proportion to the absolute value of its amplitude. Assume that the phase of the modulated signal (B) is delayed. In this case, the interval of the clock signal CK' after modulation is the modulation signal (E)
It is densest in the region of change from negative to positive, and coarsest in the region of change from zero to negative and from positive to zero.

Therefore, a phase-modulated clock signal CK' as shown in waveform (F) is created by the clock phase modulation circuit 12,
Along with the clock signal CK before phase modulation, time axis expansion/contraction/D/
A conversion circuit! Supplied on 4, 15 and 16.

The time axis expansion/contraction/D/A conversion circuits 14 to 16 having the configuration shown in FIG. It converts each signal into the corresponding analog R, G, and B signals while expanding and contracting them by the ratio of the period.

That is, the memory control circuit 3ib in the time axis expansion/contraction unit 31
writes one of the digital R, G, and B signals supplied to the input terminal 30 into the buffer memory 31a in synchronization with the clock signal CK before phase modulation, and also writes this written digital signal after phase modulation. Specifically, such a time axis expansion/contraction section expands/contracts the time axis by reading it from the buffer memory 31a in synchronization with the clock signal CK" and passing it to the main body section 32. This is realized by a FIFO using the write and read clocks.

As a result, as is clear from the waveform (G) in Fig. 4, the time axis is reduced for the central part of the original waveform of the R, G, and B signals shown by the dotted line, and the time axis for the surrounding part is reduced. The analog R1G and B signals shown by solid lines, which have undergone contour enhancement by stretching the axis, are time axis stretched and D/
The signals are output from the A conversion circuits 14 to 16.

Analog R and G output from this main body section 32.

The B signal is output to the output terminal 34 via the low-pass filter circuit 33. This low-pass filter circuit 33 is for removing harmonic components generated in the digital differentiation circuit 11a in the analog differentiation signal generation circuit 11 and the main body section 32.

In this way, the time axes of the R, G, and B signals are expanded or contracted by the differential signal indicating the appearance of the contour of the luminance signal, and the contour is emphasized.

In the above embodiment, the analog differential signal generation circuit 11 is composed of a digital differential circuit 11a and a 17/A conversion circuit 11b. However, instead of this configuration, a D/A conversion circuit that converts a digital luminance signal into an analog signal,
An analog differential signal generation circuit can be configured with an analog differential circuit that differentiates the output of this D/A conversion circuit.

FIG. 5 is a block diagram showing the configuration of a contour enhancement circuit for a television display screen according to another embodiment of the present invention;
III is an input terminal for analog luminance signal Y, I Itr
113 are input terminals for the analog color difference signals C1 and C2, respectively; Il'4 is an input terminal for the clock signal CK; 40
a, 40 b, 40 c are A/D conversion circuits, 4
1 is an analog differential signal generation circuit, 42 is a clock phase modulation circuit, 43 is a digital matrix circuit, 44, 4
5.46 is time axis expansion/contraction/D/A conversion circuit, O++, O4
, 0, and 3 are analog R and G that constitute the color display screen that has been subjected to contour enhancement processing.

This is the output terminal for the B signal.

The analog differential signal generation circuit 41 includes an analog differential circuit 41a that differentiates the analog luminance signal Y supplied via the input terminal Ill.

This analog differentiation circuit 41a includes resistors, capacitors,
It consists of real amplifiers, etc.

Input terminal 1. The analog luminance signal supplied to is differentiated by an analog differentiation circuit 41a in an analog differentiation signal generation circuit 41, resulting in an analog differentiation waveform as shown in FIG. 4(E). The clock phase modulation circuit 42 phase-modulates the clock signal CK of a predetermined period using the analog differential waveform to generate a lock signal CK as shown in FIG. 4(F).
', the time axis expansion/contraction/D/A conversion circuit 44. 4
5. 46.

The time axis expansion/contraction circuits 44 to 46 are all configured as shown in FIG. is converted to the corresponding analog R, G, B signal while being expanded or contracted by the ratio of
Analog R that makes up the contour-enhanced color display screen,
The signals are output as G and B signals through output terminals 0++, 0□, and 013, respectively.

The above has exemplified the configuration in which the analog luminance signal on the input terminal III is differentiated by the analog differentiation circuit 41a to generate the analog differential signal to be supplied to the clock phase modulation circuit 42. However, the analog differential signal may be generated by differentiating the digital luminance signal output from the A/D conversion circuit 40a with a digital differentiating circuit and then converting it into an analog signal.

Furthermore, a configuration has been shown in which the analog luminance signal and the analog color difference signal are converted into digital signals and then converted into digital R, G, and B signals by a digital matrix circuit. However, after converting the analog luminance signal and analog color difference signal into analog R, G, and B signals using an analog matrix circuit, they are converted to digital R, G, and B signals using a D/A conversion circuit.
, B signal.

(Effects of the Invention) As explained in detail above, the contour enhancement circuit of the present invention has the following features:
A clock signal with a predetermined period is phase-modulated using an analog differential waveform of a luminance signal, and the time axes of digital R, G, and B signals generated from the luminance signal and color difference signal are multiplied by the ratio of the clock signal period before and after the phase modulation. Analog R and G that can be expanded and contracted.

By converting to the B signal, the time axis is expanded and compressed within the digital video signal processing system in the same way as in the conventional speed modulation method, so it is significantly cheaper than the conventional circuit that performs this within the deflection system. and high performance.

Furthermore, since the contour enhancement circuit of the present invention is mainly composed of a differential circuit, a phase modulation circuit, etc. with a simple configuration, the cost can be reduced compared to the conventional technology using a digital filter circuit with a relatively complicated configuration. .

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the configuration of an edge enhancement circuit for a television display screen according to an embodiment of the present invention, FIG. 2 is a block diagram illustrating the configuration of the digital differentiation circuit 11a in FIG. 1, and FIG. The figure is a block diagram illustrating the configuration of the time axis expansion/contraction/D/A conversion circuit shown in FIG. 1, FIG. 4 is a waveform diagram for explaining the operation of the circuit shown in FIG. FIG. 7 is a block diagram showing the configuration of an outline emphasis circuit for a television digital display screen according to another embodiment. III I! , Is...Input terminal for digital luminance signal (Y) and digital color difference signal (C1, C2) forming a color display screen for edge enhancement, I11+
I ,,I Iff...Input terminal for analog luminance signal (Y) and analog color difference signal (CI, C2) forming the color display screen to be edge emphasized, 14+114...Clock signal (CK) with a predetermined period Input terminal, 11.41
... Analog differential signal generation circuit, 12.42 ... Clock phase modulation circuit, 13.43 ... Digital matrix circuit, 14.15.16; 44.45.46.
・・Time axis expansion/contraction/D/A conversion circuit, 0. ,O,,O,,
01110st, Oo... Output terminal for analog R, G, and B signals forming a color display screen with edge enhancement.

Claims (6)

[Claims] (1) An analog differential signal generation circuit that generates and outputs an analog differential signal based on digital luminance signals arranged in synchronization with a clock signal of a predetermined period; a clock phase modulation circuit for modulating; a digital matrix circuit for converting the digital luminance signal and the digital color difference signal into digital R, G, and B signals and outputting the digital R;
, G, B signals are converted into corresponding analog R, G, B signals while expanding or contracting the time axes of the clock signal after phase modulation by a ratio of the period of the clock signal after phase modulation to the period of the clock signal before phase modulation. An outline enhancement circuit for a television display screen, characterized by comprising a circuit. (2) The analog differential signal generation circuit comprises a digital differential circuit that differentiates a digital luminance signal, and a D/A conversion circuit that converts the output of the digital differential circuit into an analog signal. The outline enhancement circuit for a television display screen according to scope 1. (3) A patent claim characterized in that the analog differential signal generation circuit comprises a D/A conversion circuit that converts a digital luminance signal into an analog signal, and a differentiation circuit that differentiates the output of this D/A conversion circuit. The outline enhancement circuit for a television display screen according to item 1. (4) a digital R in which analog luminance signals and analog color difference signals are arranged in synchronization with a clock signal of a predetermined period;
a signal conversion circuit that converts into G and B signals; an analog differential signal generation circuit that generates and outputs an analog differential signal based on the analog luminance signal; and phase modulates the clock signal with the output of the analog differential signal generation circuit. While expanding or contracting the time axes of the digital R, G, B signals output from the clock phase modulation circuit and the signal conversion circuit by a ratio times the period of the clock signal after phase modulation to the period of the clock signal before phase modulation. Compatible analog R, G,
1. A circuit for enhancing the outline of a television display screen, comprising: a D/A conversion circuit for converting into a B signal and outputting the signal. (5) The signal conversion circuit includes an A/D conversion circuit that converts the analog luminance signal and the analog color difference signal into digital signals while sampling them in synchronization with the clock signal, and the converted digital luminance signal and digital color difference signal. 5. The contour emphasizing circuit for a television display screen according to claim 4, further comprising a digital matrix circuit for converting signals into digital R, G, and B signals. (6) The signal conversion circuit includes an analog matrix circuit that converts the analog luminance signal and analog color difference signal into analog R, G, and B signals, and converts each of the converted analog R, G, and B signals into digital signals. Convert A/
5. The outline enhancement circuit for a television display screen according to claim 4, further comprising a D conversion circuit.