JPH02142279A - Picture quality improvement device - Google Patents

Abstract

PURPOSE:To attain remarkably high quality by providing a correction circuit for each series of 3-primary color video signal separately so as to obtain a proper correction for each signal and applying digital flair correction to the picture quality of a television receiver of a large screen. CONSTITUTION:The 3-primary color video signal inputted is corrected by the independent circuit at first. For example, an R signal is converted into a digital video signal by an A/D converter 11a, a correction signal generated by a horizontal low pass filter 14a and a vertical low pass filter 15a is converted into an analog signal by a D/A converter 13a and a digital video signal being subject to delay compensation at a delay compensation circuit 12a is converted by the D/A converter 13a into an analog video signal, which is synthesized with the former analog signal at a synthesis circuit comprising a subtractor 17a and an adder 18a, and the result is outputted. Thus, the 3-primary color signal whose picture quality is improved is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a color television receiver, particularly a so-called color television receiver in which an image is obtained by projecting three primary color image lights onto a large screen from a projection tube. Regarding projection type receivers.

Conventional technology Today, when displaying on a large screen, C
Due to manufacturing reasons, the current limit for RT is about 400 inches. For larger screens, the method using a projection tube is currently practical.

Also, in the case of large, high-quality screens, high image quality cannot be obtained simply by making the screen larger.

As the number of scans increases, requirements regarding image quality become stricter.

In particular, in the projection type, the current density of the beam of the projection tube is 5 to 10 times that of the direct view type, so the beam becomes thicker and the resolution decreases due to the influence of the lens, and the high brightness of the projection tube and lens etc. The flare caused by this caused a decline in image quality.

Perhaps because large-screen projection tube receivers are still in the RJH stage, the flare correction means described above have not yet been established as a completely defined technology.

For example, as a flare correction means that has been proposed for high-definition televisions, "Improvement of Image Quality of Projection Displays for High-Definition Televisions - Removal of Flare Interference by 8AW Filter"
"There is a method announced at the 1982 Annual Conference of the Television Society of Japan, 5PI-14, in which a video signal is first AM-modulated, passed through a SAW filter, and then an analog filter is used again.

This method is used to attenuate the modulated signal wave at ±I MHz near the modulated carrier frequency, thereby attenuating the low frequency components for flare correction.

However, in this method, the modulation carrier frequency is 100MHz.
, or higher frequencies must be used, and even if the horizontal flare component of the screen can be removed, responding to the vertical component requires a very accurate one-line delay line, which is difficult to implement. .

Therefore, a prototype flare correction device was created using a digital method to construct two-dimensional filters in the vertical and horizontal directions.
Due to the cost and size of digital filters, they have not reached the general market.

Problems to be Solved by the Invention As stated above, large-screen television receivers that fully adopt the necessary flare correction means and can obtain high-quality images are not manufactured as prototypes. There are some, but none are available on the general market due to cost issues.

Here, "completely" particularly means that flare correction is possible for both vertical and horizontal components.

In the analog method, there are some differences, especially in the uniformity of the filter and fluctuations due to temperature of the delay line, and in the case of a large-scale method,
There is a sense that the timing adjustment of the front equipment is elegant.

Digital methods can, in principle, adequately address the above-mentioned problems, and offer plenty of design flexibility.

There are difficulties with increasing scale.

The interlayer lies in how to implement the correction device digitally.

However, the above-mentioned digital filters have two configurations: a recursive filter and a non-recursive filter, but due to its characteristics, the single recursive filter requires processing such as time axis inversion to eliminate phase distortion, and it requires a large amount of processing power. There was a tier that was expensive because it required memory.

SUMMARY OF THE INVENTION An object of the present invention is to configure a circuit using digital means in order to solve the above problems, and to configure a flare correction device using a circuit that uses a filter that simultaneously realizes a reduction in size and cost. .

Means for Solving the Problems The image quality improvement device of the present invention inputs each video signal separately for each of the three primary color video signal series in a television receiver, converts the input from A/ In the image quality improvement device of the type that outputs each D/A converted signal, the flare correction section includes a guarantee delay circuit and a guarantee delay circuit provided in parallel to the A/D converted digital video signal input. It is constituted by a synthesis circuit that synthesizes the output signal of the flare correction section and a reference signal with guaranteed delay, and the flare correction section performs correction in the vertical and horizontal directions in series using a group of low-pass filters. , which is composed of circuits that perform calculations from delayed digital video signals. The vertical low-pass filter in the flare correction section is a combination of an acyclic filter and a recursive filter, so that the acyclic filter processes the front of the input impulse for one hour with respect to the required impulse response. At the same time, phase distortion is eliminated by processing with a recursive filter, and the horizontal low-pass filter is an acyclic filter in which the A/D conversion clock register is the 1-earth array. It is composed of

Function: According to the present invention, correction is provided separately for each series of three primary color video signals, so that appropriate correction can be obtained for each signal.

Since the correction is all done digitally, the signal is input to the flare correction section after A/D conversion.

In addition, the correction signal creation circuit uses a low-pass recursive filter to extract low-frequency components in the horizontal direction, and then uses a low-pass filter that is a combination of a recursive filter and an acyclic filter to extract low-frequency components in the vertical direction. Extract the area components. A high frequency component is obtained by subtracting the two-dimensional low frequency component thus extracted from the reference signal whose delay is guaranteed.

By D/A converting this signal and adding it to the reference signal, it is possible to obtain three primary color signals with improved image quality.

Embodiment One embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows the basic configuration of an embodiment of the present invention.

First, in this embodiment, the input three primary color video signals are corrected by independent circuits having the same configuration.
Focusing on the signal, the A/D converter 11a converts it into a digital video signal, and the horizontal low-pass filter 1 converts it into a digital video signal.
4a, converting the correction signal generated by the vertical low-pass filter 15a into an analog signal by the D/A converter 13a;
This signal is combined with the analog video signal obtained by converting the digital video signal whose delay has been guaranteed by the delay compensation circuit 12a and the D/A converter 13a by a combining circuit constituted by a subtracter 17a and an adder 18a, and outputs the result.

Note that in the following explanation, the explanation will be made without particularly distinguishing between R, G, and B signals, so the suffixes of the symbols will be omitted.

The horizontal low-pass filter 14 in this embodiment is intended to be an acyclic filter, but the same effect can be obtained by using a low-pass filter such as a one-cycle filter.

The details of the circuit of the vertical low-pass filter 15 are shown in FIG. This is composed of an FIR filter memory group 21, a counting circuit group 22, and an adding circuit group 23.
It is a combination of two types of filters: a filter and an IIR filter.

Note that the number of memory groups for each filter is appropriately set depending on the required characteristics of the filter.

Effects of the Invention As described above, according to the present invention, the image quality of a large-screen television receiver can be significantly improved by digitally performing flare correction.

Further, the following effects can be mentioned as effects of the present invention.

(1) Since each of the three primary color signals is corrected, any image can be completely corrected.

(2) Since the vertical low-pass filter uses a filter that is a combination of an FIR filter and an IIR filter, the memory for time axis inversion can be omitted compared to a case where it is configured with only an IIR filter, and it is configured with only an F1R filter. Compared to the conventional case, the line memory required for one line for one delay can be significantly reduced.

(3) The filter characteristic itself is a low-pass type, and by taking the difference from the reference signal, it is effectively an act-pass type filter, so good correction can be obtained even at the four corners of a quadrilateral window pattern.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing the basic configuration of an embodiment of the present invention, and FIG. 2 is a configuration diagram showing an example of a vertical low-pass filter. 11 a to l 1 c --A/D converter, 12a to 1
2c...guarantee delay circuit, 13a-13c...D/A converter. 14a-14c...Horizontal low-pass filter, 15a
~15c...Vertical low pass filter, 16a~16
c...D/A converter. 17a-17c...Subtractor, 18a-18c...Adder, 21...FIRIR filter line delay memory, 22...
- FIRIR filter number circuit group, 23... FIRIR filter calculation circuit group, 24... IIR filter counting circuit 5... IIRIR filter calculation circuit.

Claims (2)

[Claims] (1) Input each video signal individually for each of the three primary color video signal series in the television receiver, perform A/D conversion on this input, and after correcting flare, output the D/A converted signals respectively. In the image quality improvement device of the type, the flare correction section is connected to a guarantee delay circuit provided in parallel with the input of the digital video signal after A/D conversion, and a delay guaranteed between the output signal of the flare correction section and the output signal of the flare correction section. The flare correction section is composed of a synthesis circuit that synthesizes the reference signal with the reference signal, and the flare correction section is composed of a circuit that performs correction in the vertical and horizontal directions in series using a group of low-pass filters, and then performs calculations from the delayed digital video signal. An image quality improvement device that is characterized by: (2) The vertical low-pass filter in the flare correction section is a combination of an acyclic filter and a recursive filter. The horizontal low-pass filter is a non-recursive filter with a one-delay delay for the A/D conversion clock register. The image quality improving device according to claim 1, characterized in that the image quality improving device is configured as follows.