JPS6218892A - Picture quality switching circuit of television receiver - Google Patents

Abstract

PURPOSE:To reduce the dot disturbance of a television signal without deteriorating frequency characteristics when a video input signal is selected by inserting a trap into a luminance signal when a television broadcasting signal side is selected by an input switching circuit. CONSTITUTION:A television broadcast signal 1 is detected by a detecting circuit 6 to becomes a video band signal, which is switched by an input switching circuit 7 to a video signal 2 inputted from a video input terminal. A switching signal 5 generated by the input switching circuit 7, on the other hand, is utilized to turn on a transistor (TR) Q for switching only when a television broadcast is received to insert a trap 9 of 3.58MHz into an output line of a luminance signal 4. Consequently, the television broadcast signal has frequency characteristics corrected even by the detecting circuit 6 and further has frequency characteristics corrected behind the input switching circuit 7 to increase dot disturbance, but the dot disturbance is reduce by the trap 9.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image quality switching circuit for a television receiver [1] having a video input terminal.

BACKGROUND OF THE INVENTION In recent years, many preview receivers have been equipped with video input terminals, allowing them to be connected to video equipment. Since video input signals are not subject to band limitations like normal broadcast signals, the frequency characteristics of television reception are improved, and the resolution is significantly improved.

FIG. 2 shows a conventional video switching circuit. 10 is an RF large input television broadcast signal, 11 is a video signal input from a video input terminal, 12 is a drive signal for displaying on a CRT, 13 is a detection circuit that detects the television broadcast signal 10 and converts it into a video band, 14 is a detection circuit An input switching circuit 15 switches between the television signal output from the detection circuit 13 and the video signal 11, and 15 is a frequency characteristic correction circuit for the switched signal.

With such a circuit, the frequency characteristics of the video signal 11 input from the video input terminal are improved, and the resolution is improved.

Problems that R-mei attempts to solve In such a conventional configuration, the band-limited television signal also passes through the frequency characteristic correction circuit 15 and its frequency characteristics are expanded. The TV signal is not a signal with stable characteristics like the signal input from the video input terminal, but
The phase characteristics vary depending on various radio wave conditions, and some signals have a lot of ringing. If the frequency characteristics of this signal are extended by the frequency characteristic correction circuit 15, dot interference and the like will be emphasized, and the image quality will deteriorate.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image quality switching circuit that can obtain good image quality without changing the frequency characteristics when selecting a video input signal when selecting a television signal with the input switching circuit.

Means for Solving the Problems The picture quality switching circuit of the present invention selects and outputs either the detected television signal converted into a video band or the video input terminal from the video input terminal. In addition, a signal separation circuit that separates the video signal output from the switching circuit into a chroma signal and a luminance signal, and a trap circuit that removes the carrier color signal component are provided. The present invention is characterized in that the trap circuit is inserted into the luminance signal output line of the signal separation circuit when the television signal side is selected in conjunction.

Effect: According to this configuration, a trap is inserted into the luminance signal when the input switching circuit selects the TV broadcast signal side, so dot interference in the TV signal is reduced without deteriorating the frequency characteristics when the video input signal is selected. can.

Example Hereinafter, one embodiment of the present invention will be described based on FIG. 1.

The television broadcast signal 1 is detected by a detection circuit 6 to become a video band signal, which is switched to a video signal 2 inputted from a video input terminal by an input switching circuit 7. The switched signals are separated into chroma signal 3 and i! by a luminance signal and chroma signal separation circuit 8 such as a comb filter. '! signal 4. On the other hand, using the switching signal 5 generated in the input switching circuit 7, the switching transistor Q is made conductive only when receiving a television broadcast, and the trap 9 of 3.588H2 is
is inserted into the output line of the luminance signal 4.

As a result, a video signal input from the video input terminal that is not subject to band restrictions is processed as a signal with good frequency characteristics, while a television broadcast signal is also corrected for its frequency characteristics in the detection circuit 6, and the input switching circuit 7 and onwards. Further frequency characteristic correction is performed in , and the dot interference becomes larger, but
This approximately 3.588 Hz trap 9 can reduce dot interference.

As described in the detailed description of the invention, the image quality switching circuit for the television receiver of the present invention inserts a trap for removing the carrier color signal component into the iris signal when the input switching circuit selects the television broadcast signal side. This makes it possible to reduce dot interference in television signals without deteriorating the frequency characteristics when a video input signal is selected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the picture quality switching circuit of the present invention, and FIG. 2 is a block diagram of a conventional video switching circuit.

Claims (1)

[Claims] 1. A switching circuit is configured to select and output one of a television signal detected and converted into a video band and a video input signal from a video input terminal, and an output of the switching circuit. A signal separation circuit that separates a video signal into a chroma signal and a luminance signal, and a trap circuit that removes a carrier color signal component are provided, and when the television signal side is selected in conjunction with switching of the switching circuit, the trap circuit An image quality switching circuit for a television receiver configured to be inserted into a luminance signal output line of a signal separation circuit. 2. An image quality switching circuit for a television receiver according to claim 1, wherein the trap circuit is a 3.58 MHz trap.