JPH06315161A - Color television receiver - Google Patents

Abstract

PURPOSE:To provide a color television which is capable of performing an image control of the sharpness and the band limit, etc., which are suitable to an input signal and a screen size by providing more or one sharpness control circuit elements and more or one band limit circuits on the sharpness control circuit provided on a luminance signal circuit series. CONSTITUTION:A first sharpness control circuit element 22 controls the amplification degree of a Y signal in the vicinity of 1MHz and performs the peaking or the trapping of the vicinity of 1MHz. A second sharpness control circuit element 23 also performs operations in the vicinity of 2MHz in the same way as the first sharpenss control circuit element 22. The (n-1)th sharpness control circuit element 24 operates in the same way. A changeover switch 28 bypasses via an LPF and performs a switching so as to select either one of LPF 25, 26 and 27. By this constitution, the optinum control corresponding to the band of an input signal, an S/N and the size of a display screen become possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color television receiver capable of controlling image quality by switching sharpness and band.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram showing a main part of a general color television receiver (hereinafter referred to as a color TV), in which 1 is an antenna, 2 is a tuner, and 3 is a tuner.
Is a VIF circuit, 4 is a separation circuit for luminance signals and chroma signals (hereinafter referred to as Y / C separation circuit), and 5 is Y / C separation circuit 4
Is a luminance signal output (hereinafter referred to as Y output), and 6 is a chroma signal output of the Y / C separation circuit 4 (hereinafter referred to as C output).
Reference numeral 7 denotes a delay circuit, which is a circuit for eliminating a time difference between the Y signal and the C signal due to a difference in processing speed of the route signals. 8 is a sharpness control circuit, 9
Is a contrast control circuit, 10 is a clamp circuit, and 11 is a brightness control circuit. 12
Is a chroma amplifier circuit for amplifying the C output 6, 13 is an automatic color control circuit (hereinafter referred to as ACC circuit), 1
Reference numeral 4 is a color gain control circuit, and 15 is a demodulator circuit. 16 is a matrix circuit that combines Y and C signals; 17 is R of the matrix circuit 16;
GB output, 18 is a CRT driver circuit, and 19 is a CRT.

Next, the operation will be described. Antenna 1
The radio wave received by is selected by the tuner 2 as a high frequency signal having a target frequency, converted to an intermediate frequency, and output. Next, the VIF circuit 3 detects and outputs a video signal, and the Y / C separation circuit 4 separates it into a Y output 5 and a C output 6. The Y output 5 is delayed by the delay circuit 7, and as shown in FIG. 9, the sharpness circuit 8 has a high effect of enhancing the sharpness at a certain frequency, generally 1 to 1.
The amplification of the frequency of 3 MHz is controlled. Next, the contrast is controlled by the contrast control circuit 9,
After the clamp circuit 10 clamps the voltage of the pedestal portion, the brightness control circuit 11 variably controls the DC voltage of the pedestal portion.

On the other hand, the C output 6 from the Y / C separation circuit 4
Is amplified and controlled by the ACC circuit 12 so that the amplitude of the burst signal becomes constant, and the color gain control circuit 1
The amplitude of the C signal is controlled by 4 and then demodulated by the demodulator circuit 15. Brightness control circuit 11
The Y signal that has passed through and the C signal demodulated by the demodulator circuit 15 are arithmetically processed by the matrix circuit 16, and R
The GB output 17 is output, amplified by the CRT drive circuit 18, and then applied to the CRT 19.

[0005]

The conventional color TV is constructed as described above. In particular, the sharpness control circuit 8 has one sharpness control as shown in the block diagram of the internal construction of FIG. Since it has only the circuit element 22 (20 and 21 have its input and output terminals), it is possible to control only one location of the frequency as shown in FIG. 9, and the sharpness corresponding to the band of the input signal, S / N, etc. However, there is a problem in that the image quality control such as frequency and band limitation cannot be performed sufficiently.

The present invention has been made to solve the above problems, and a color TV capable of controlling the image quality such as sharpness suitable for an input signal and screen size and band limitation.
The purpose is to get.

[0007]

A color T according to the present invention
V is provided with one or more sharpness control circuit elements and one or more band limiting circuits in the sharpness control circuit provided in the luminance signal circuit series, or two or more sharpness controls for peaking or trapping at different frequencies. It is provided with circuit elements.

[0008]

In the color TV according to the present invention, the amplification degree in the vicinity of a plurality of frequencies can be adjusted by the sharpness control circuit element and the band limiting circuit, so that the band of the input signal, the S / N ratio, and the display screen size can be adjusted. Image quality can be controlled correspondingly.

[0009]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an internal block diagram of the sharpness control circuit 8 in FIG. 7, in which 20 is a Y signal input terminal of the sharpness control circuit 8, 21 is a Y signal output terminal, 22 is a sharpness control circuit element,
23 is a second sharpness control circuit element, 24
Is a (n-1) th sharpness control circuit element, 25 is a first low-pass filter (hereinafter referred to as LPF) having a cutoff frequency f ₁ , 26 is a second LPF having a cutoff frequency f ₂ , and 27 is Cut-off frequency is f _m
Is a changeover switch.

FIG. 2 is a diagram showing the control characteristics of the sharpness control circuit shown in FIG. 1, with the horizontal axis representing frequency f and the vertical axis representing gain. Further, FIG. 3 shows that when the roll-off order is changed at the same cutoff frequency in the LPF of FIG.
For example, the roll-off order of the first LPF 25 is second and second
LPF 26 has a roll-off order of 4th and m-th LP
It is a figure which shows the control characteristic when the roll-off order of F27 is 2 * l order.

In such a structure, the first sharpness control circuit element 22 is, for example, 1 MH.
By controlling the amplification of the Y signal near z, as shown in FIG.
Peaking or trapping around MHz. Second
The sharpness control circuit element 23 also operates similarly to the first sharpness control circuit element 22 in the vicinity of 2 MHz, for example. The same applies to the (n-1) th sharpness control circuit element 24.

The changeover switch 28 is a switch for bypassing without passing through the LPF or for selecting any one of the LPFs 25, 26, 27. The changeover switch 28 is indicated by f in FIG. 2 according to the characteristics of the bypass and each LPF. ₀ ,
The characteristics shown by f ₁ , f ₂ , and f _m are shown. When the LPF is set to the same cutoff frequency and the rolloff order is changed, 0 is set depending on the bypass and each LPF.
The characteristics are as shown in the second order, second order, fourth order, and 2 × l order.

Example 2. In the first embodiment, a plurality of L
The PF is switched to control the bandwidth.
As shown in FIG. 4, by inserting the m-th sharpness control circuit element 29 having a peaking frequency near the cutoff frequency, as shown in FIG.
A control characteristic similar to that of F can be obtained.

Example 3. Further, in the first embodiment, the bandwidth is controlled by switching a plurality of LPFs having different roll-off frequencies, but as shown in FIG.
Even if 25, 26, and 27 are connected in series and the tap output thereof is switched by the changeover switch 28, the same characteristics as in FIG. 3 can be obtained.

[0015]

As described above, according to the present invention, the sharpness and the band limitation can be controlled by one or more sharpness control circuit elements and one or more band limiting circuits, or two or more sharpness control circuit elements. Since it is configured to perform the above, the color T that can be optimally controlled according to the band of the input signal, the S / N, etc., and the display screen size.
V is obtained. Therefore, it is particularly effective for a projector having a variable screen size such as a projection type projector.

[Brief description of drawings]

FIG. 1 is an internal block diagram of a sharpness control circuit according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a control characteristic of that of FIG.

FIG. 3 is a diagram showing a control characteristic of that of FIG.

FIG. 4 is an internal block diagram of a sharpness control circuit according to a second embodiment of the present invention.

5 is a diagram showing a control characteristic of that of FIG. 4;

FIG. 6 is an internal block diagram of a sharpness control circuit according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a main part of a general color TV.

FIG. 8 is an internal block diagram of a conventional sharpness control circuit.

9 is a diagram showing a control characteristic of that of FIG. 8;

[Explanation of symbols]

 1 Antenna 2 Tuner 3 VIF Circuit 4 Y / C Separation Circuit 7 Delay Circuit 8 Sharpness Control Circuit 9 Contrast Control Circuit 10 Clamp Circuit 11 Brightness Control Circuit 12 Chroma Amplifier Circuit 13 ACC Circuit 14 Color Gain Control Circuit 15 Demodulator Circuit 16 Matrix Circuit 18 CRT drive circuit 19 CRT 20 Y signal input terminal 21 Y signal output terminal 22 Sharpness control circuit element 23 Sharpness control circuit element 24 Sharpness control circuit element 25 LPF 26 LPF 27 LPF 28 Changeover switch 29 Sharpness control circuit element

Claims (2)

[Claims] 1. A color television receiver in which a received video signal is separated into a luminance signal and a chroma signal, and then combined in a matrix circuit and added to a CRT. A color television receiver comprising a sharpness control circuit and at least one sharpness control circuit element and at least one band limiting circuit. 2. A color television receiver in which a received video signal is separated into a luminance signal and a chroma signal, and then combined in a matrix circuit and added to a CRT. A color television receiver comprising a sharpness control circuit and two or more sharpness control circuit elements for peaking or trapping at different frequencies.