JPH03245680A - 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 with a differentiating waveform of a luminance signal and converting a digital luminance signal into an analog signal while the signal is expanded or contracted by a ratio of periods of clock signals before and after phase modulation. CONSTITUTION:A digital luminance signal is fed to a differentiating circuit 1 and converted into an analog signal at a next-stage D/A converter circuit 2 and a clock signal of a prescribed period fed from an input terminal I2 is subject to pulse phase modulation by using an analog differentiating signal (E) outputted from the D/A converter circuit 2 at a phase modulation circuit 3 of the next stage. Thus, the phase-modulated clock signal CK' is generated by the phase modulation circuit 3 and fed to a D/A converter circuit 5 together with the clock signal CK before phase modulation. The D/A converter circuit 5 converts the digital luminance signal into an analog luminance signal while the time axis of the digital luminance signal via a delay circuit 4 is expanded 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 a TV set, outline enhancement 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 specifications of Japanese Patent Publication No. 55-2114 and Japanese Patent Publication No. 63-992, if necessary.

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, phase-modulates a clock signal with this analog differential signal, and converts the clock signal into a digital signal. Means is provided for converting the digital luminance signal into an analog luminance signal while expanding or contracting the time axis of the luminance signal by a ratio of the period of the clock signal before and after the phase modulation.

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.

Furthermore, since the contour enhancement circuit for a television display screen according to the present invention is mainly composed of a digital differentiator circuit, a phase modulation circuit, etc. with a simple configuration, it is different from conventional circuits that are mainly composed of a digital filtering circuit with a relatively complicated configuration. The cost can be reduced compared to circuits.

Hereinafter, the operation of the present invention will be explained in detail together with examples.

(Embodiment) FIG. 1 is a block diagram of an edge enhancement circuit for a television display screen according to an embodiment of the present invention, where I is an input terminal for a digital luminance signal, I is an input terminal for a clock signal, 1 is a digital differentiation circuit, 2 is a D/A conversion circuit, 3
is a phase modulation circuit, 4 is a delay circuit, 5 is a D/A conversion circuit,
6 is a low-pass filter circuit, and OI is an output terminal for an analog luminance signal subjected to edge enhancement processing.

As illustrated in FIG. 2, the digital differentiation circuit 1 shown in FIG. It is composed of an adder 12 that adds signals, and outputs a differential waveform of a digital luminance signal supplied from an input terminal 10 to an output terminal 13.

The D/A conversion circuit 5 shown in FIG. 1 is composed of a time axis expansion/contraction section 21 and a main body section 22, as shown in FIG. The time axis expansion/contraction section 21 at the front stage is composed of a batza memory 21a and a memory control circuit 21b. The rear main body section 22 has a well-known configuration consisting of a combination of a switch, a resistor network, and a group of operational amplifiers.

The delay circuit 4 shown in FIG. 1 uses a differential circuit 1 to differentiate a digital luminance signal, a D/A converter circuit 2 to perform D/A conversion, and the analog differentiated signal to phase modulate the clock signal CK. D/ by delaying the original digital luminance signal
This is for supplying the signal input terminal of the A conversion circuit 5.

The digital luminance signal Y supplied to the input terminal ■ in FIG. The video signal is converted into a digital video signal while being processed, and this digital video signal is created by performing Y/C separation in a digital Y/C separation circuit.

As shown in Figure 4, the original analog luminance signal is shown in waveform (A).
The clock signal CK with a predetermined period for D/A conversion transducer sampling 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 into a binary signal so that the change in amplitude can be seen at a glance. By supplying this digital luminance signal to the differentiating circuit 1, a digital differential signal shown in waveform (D) is created. This digital differential signal is converted into an analog signal by the D/A conversion circuit 2 at the next stage, thereby creating an analog differential signal shown in waveform (B).

In the next stage phase modulation circuit 3, the clock signal CK of a predetermined period supplied from the input terminal I: is pulse phase modulated by the analog differential signal (E) outputted from the D/A conversion circuit 2. This pulse phase modulation is pulse position modulation (P
It is also known as pulse modulation (PM) 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 between the modulated clock signals CK'' is densest in the negative-to-positive change region of the modulated signal (B), and coarsest in the zero-to-negative change region and positive to zero change region. Therefore, as shown in waveform (F), a phase modulated clock signal CK' is generated by the phase modulation circuit 3, and is supplied to the D/A conversion circuit 5 together with the clock signal CK before phase modulation.

The D/A conversion circuit 5 having the configuration shown in FIG. 3 converts the digital luminance signal that has passed through the delay circuit 4 into an analog luminance signal while expanding or contracting the time axis by the ratio of the clock signal period before and after phase modulation.

That is, the memory control circuit 21b in the time axis expansion/contraction unit 21
writes the digital luminance signal supplied to the input terminal 5a via the delay circuit 4 in the previous stage into the buffer memory 21a in synchronization with the clock signal CK before phase modulation, and also subjects the written digital luminance signal to phase modulation. The time axis is expanded or contracted by reading it out from the buffer memory 21a and passing it to the main unit 22 in synchronization with the later clock signal CK', that is, as is clear from the waveform (C,) in FIG. The time axis of the central part of the original waveform of the luminance signal shown by the dotted line is reduced, and the time axis of the surrounding parts is expanded, so that the analog luminance signal shown by the solid line is processed by the D/A conversion circuit. Output from 5.

The edge-enhanced analog luminance signal output from the D/A conversion circuit 5 passes through a low-pass filter circuit 6 to an output terminal 0. is output to. This low-pass filter circuit 6 is for removing harmonic components generated in the digital differentiation circuit 1 and the D/A conversion circuit 5.

In this way, the time axis of the luminance signal is expanded or contracted by the differential signal indicating the appearance of the contour of the luminance signal, and the contour is emphasized.

FIG. 5 is a block diagram showing the configuration of an outline enhancement circuit for a television eye display screen according to another embodiment of the present invention;
3 is an input terminal for a digital luminance signal, I4 is an input terminal for a clock signal, 31 is a D/A conversion circuit, 32 is an analog differentiation circuit, 33 is a phase modulation circuit, 34 is a delay circuit, 35
is a D/A conversion circuit, 36 is a low-pass filter circuit, 0. is an output terminal for an analog luminance signal.

The digital luminance signal supplied to input terminal I is D/
After being converted into an analog luminance signal by the A conversion circuit 31,
It is differentiated by the analog differentiator circuit in the subsequent stage. The clock signal CK supplied to the input terminal I4 is a clock signal C whose phase is modulated by an analog differential signal in the phase modulation circuit 33.
K' and D together with the clock signal CK before phase modulation.
/A conversion circuit 35.

The D/A conversion circuit 35, like the D/A conversion circuit 5 in FIG. The analog luminance signal is converted into an analog luminance signal while being expanded or contracted by the ratio of the period of the clock signal before and after phase modulation.The analog luminance signal that has been D/A converted without being expanded or compressed on the time axis is sent to the output terminal via the low-pass filter circuit 36. 0. is output to.

In this way, the contour emphasizing circuit shown in FIG. 5 corresponds to the contour emphasizing circuit shown in FIG. 1 in which the processing order of differentiation and D/A conversion is switched, and accordingly, the differentiating circuit may be configured with a digital circuit. There is a difference in whether it is constructed using analog circuits.

FIG. 6 is a block diagram showing the configuration of a digital image quality improvement processing device including as part of a television display screen edge enhancement circuit according to still another embodiment of the present invention.

In FIG. 6, IN is an analog video signal input terminal, 51 is an A/D conversion circuit, 52 is a timing generation circuit,
53 is a clock generation circuit, 54 is a Y/C separation circuit, 55
a, 55b are image quality improvement circuits, 56a, 56b are D/A conversion circuits, 57 is a delay circuit, 58 is a digital differentiation circuit,
59 is a D/A conversion circuit, and 60 is a phase modulation circuit.

An analog video signal is supplied to the input terminal IN from a video detection circuit of a television receiver, a reproduction circuit of a video tape recorder, or the like. This analog video signal is A/
It is supplied to the D conversion circuit 51 and converted into a digital video signal, and is also supplied to the timing generation circuit 52 and the clock generation circuit 53, and is necessary for the above-mentioned D/A conversion etc. based on the various synchronization signals included therein. timing and clock signals are generated.

The digital video signal output from the A/D conversion circuit 51 is converted into a luminance signal Y in a subsequent Y/C separation circuit 54.
and the carrier color signal C, and the corresponding image quality improvement circuit 55
a and 55b.

These image quality improvement circuits perform various image quality improvement processes such as noise removal using line-to-line correlation and frame-to-frame correlation, progressive scan conversion using scanning line interpolation, and flare correction. and the digital carrier color signal are converted into an analog luminance signal and an analog carrier color signal in the subsequent D/A conversion circuit 56a, and outputted to output terminals oy and OC.

On the other hand, the digital luminance signal output from the Y/C separation circuit 54 passes through a delay circuit 57 and is then sent to a digital differentiation circuit 58.
is supplied to The output of this digital differentiation circuit 58 is
It is converted into an analog differential signal by the D/A conversion circuit 59 and supplied to the phase modulation circuit 60. In the phase modulation circuit 60,
Clock signal CK supplied from clock generation circuit 53
is phase-modulated by the analog differential signal supplied from the D/A conversion circuit 59, and is supplied as a clock signal GK' to the D/A conversion circuit 56a.

This D/A conversion circuit WR56a is a digital luminance signal outputted from an image quality improvement circuit 55a which is provided with a time axis expansion/contraction section at the front stage of the main body section, similar to the D/A conversion circuit 5 shown in FIG. is a clock signal CK before phase modulation and a clock signal C after phase modulation in the D/A conversion circuit 56a.
It is converted into an analog luminance signal while being expanded or contracted by the ratio of the period of K'.

The signal is supplied to the output terminal oy via the low-pass filter circuit 61.

On the other hand, the device digital carrier color signal constituted by the image quality improvement circuit 55b is converted into an analog carrier color signal in synchronization with the clock signal CK, and is supplied to the output terminal Oc.

The delay circuit 57 is for compensating the difference between the delay times in the image quality improvement circuits 55a and 55b and the delay times in the digital differentiation circuit 58, the D/A conversion circuit 59, and the phase modulation circuit 60.

FIG. 7 is a block diagram showing the configuration of an outline enhancement circuit for a television display screen according to another embodiment of the present invention;
■, is an analog luminance signal input terminal, 71 is a delay circuit,
72 is an analog differentiation circuit, 73 is a phase modulation circuit, 74 is an A/D conversion circuit, 75 is a D/A conversion circuit, 76 is a low-pass filter circuit, 77 is a clock generation circuit, 03 is an analog luminance signal output terminal It is.

The analog luminance signal Y supplied to the input terminals D/
The signal is supplied to the A conversion circuit 74 and the clock generation circuit 77, and is also supplied to the analog differentiation circuit 72 via the delay circuit 71. The analog luminance signal supplied to the A/D conversion circuit 74 is sampled in synchronization with the clock signal CK of a predetermined period supplied from the clock generation circuit 77, and then converted into a digital luminance signal, which is then subjected to D/A conversion at the subsequent stage. The signal is supplied to circuit 75. In the phase modulation circuit 73, the clock signal CK supplied from the clock generation circuit 77 is phase-modulated by the differential signal of the analog luminance signal supplied from the analog differentiation circuit 72, and becomes a clock signal CK', which is sent to the D/A conversion circuit 75. is supplied to

The D/A conversion circuit 75 is the D/A conversion circuit 5 shown in FIG.
Similarly, a time axis expansion/contraction section is provided at the front stage of the main body section.

The digital luminance signal output from the A/D conversion circuit 74 is expanded or compressed by the ratio of the period of the clock signal CK before phase modulation and the clock signal CK' after phase modulation in the D/A conversion circuit 75, and is converted into an analog brightness signal. converted to
The signal is supplied to the output terminal 03 via the low-pass filter circuit 76.

(Effects of the Invention) As explained in detail above, the contour enhancement circuit of the present invention has the following features:
By phase modulating the clock signal with the differential waveform of the luminance signal, expanding or contracting it by the ratio of the clock signal period before and after phase modulation, and then converting the digital luminance signal into an analog signal, the time axis is the same as that of the conventional speed modulation method. Since the structure is such that the expansion/contraction is performed within the digital video signal processing system, a significant reduction in cost and higher performance can be achieved compared to conventional circuits in which this is performed within the deflection system.

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 according to an embodiment of the present invention, FIG. 2 is a block diagram illustrating the configuration of the digital differentiation circuit 1 of FIG. 1, and FIG.
The figure is a block diagram illustrating the configuration of the D/A conversion circuit in Figure 1, Figure 4 is a waveform diagram to explain the operation of the circuit in Figure 1, and Figure 5 is a diagram showing still another embodiment of the invention. FIG. 2 is a block diagram illustrating the configuration of an image quality improvement circuit that includes a related television edge enhancement circuit as a part. 1,, I3...Input terminal for digital luminance signal, l
χr I4...Clock signal input terminal, IN
...Analog video signal input terminal, 1°58...
Digital differentiation circuit, 2, 31.59... D/A conversion circuit, 32... Analog differentiation circuit, 3.33.60.
. . . Phase modulation circuit, 5° 35.65a . . . Luminance signal D/A conversion circuit, 21 . Control circuit, 22... Main body of D/A converter 5, 01
10z, Oy... Output terminals for analog luminance signals subjected to contour enhancement.

Claims (3)

[Claims] (1) A digital differentiation circuit that differentiates digital luminance signals arranged in synchronization with a clock signal of a predetermined period, a D/A conversion circuit that converts the output of this digital differentiation circuit into an analog signal, and this D/A conversion a clock phase modulation circuit that phase-modulates the clock signal with an output of the circuit; 1. An edge enhancement circuit for a television display screen, comprising: a D/A conversion circuit that converts a digital luminance signal into an analog luminance signal. (2) D/A that converts digital luminance signals arranged in synchronization with a clock signal of a predetermined period into analog luminance signals
a conversion circuit; an analog differentiation circuit that differentiates the output of the D/A conversion circuit; a clock phase modulation circuit that modulates the phase of the clock signal with the output of the analog differentiation circuit; A television display characterized by comprising: a D/A conversion circuit that converts this digital luminance signal into an analog luminance signal while expanding or contracting the ratio of the period of a clock signal after phase modulation to the period of the clock signal before modulation. Screen contour enhancement circuit. (3) an analog differentiation circuit that differentiates an analog luminance signal; a clock phase modulation circuit that modulates the phase of a clock signal of a predetermined period with the output of the analog differentiation circuit; an A/D conversion circuit that converts the digital luminance signal into a signal, and an A/D conversion circuit that expands or contracts the time axis of the digital luminance signal output from the A/D conversion circuit by a ratio of the period of the clock signal after the phase modulation to the period of the clock signal before the phase modulation. and a D/A conversion circuit for converting the digital luminance signal into an analog luminance signal.