JPH0431875U - - Google Patents

Description

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an image quality adjustment circuit in a television receiver according to one embodiment of this invention, FIG. 2 is a diagram showing the operation of FIG. 1, and FIG.
This figure is a block diagram showing the configuration of an image quality adjustment circuit according to a modification of FIG. 1, and FIG. 4 is a block diagram showing the configuration of an image quality adjustment circuit according to a modification of FIG. 3. FIG. 5 is a block diagram showing the configuration of a conventional image quality adjustment circuit for a television receiver. Explanation of main symbols, 10...Contrast adjustment circuit, 12...Bright adjustment circuit, 22...Video signal extraction circuit, 24...Upper peak level detection circuit, 26...Lower peak level detection circuit, 28
...Contrast control circuit, 30,30A...Bright control circuit.

Claims (1)

[Claims for Utility Model Registration] (1) An image quality adjustment circuit having a contrast adjustment circuit that changes the gradation of a brightness signal based on a contrast control signal, and a brightness adjustment circuit that changes the brightness of a brightness signal based on a brightness control signal. , an effective video signal extraction circuit extracts an effective video signal portion from the clamped luminance signal input to the image quality adjustment circuit, and detects an upper peak level of the effective video signal extracted by the effective video signal extraction circuit. An upper peak level detection circuit, a lower peak level detection circuit that detects the lower peak level of the effective video signal extracted by the effective video signal extraction circuit, and an upper peak level detected by the upper peak level detection circuit. Based on the lower peak level detected by the lower peak level detection circuit, a contrast control signal is created that strengthens or weakens the gradation in the direction opposite to the magnitude of the difference between the upper peak level and the lower peak level, Based on the contrast control circuit that outputs to the contrast adjustment circuit, the upper peak level detected by the upper peak level detection circuit, and the lower peak level detected by the lower peak level detection circuit, the contrast of the output of the contrast adjustment circuit is determined. For the difference between the lower peak level of the effective video signal part and the black level or a predetermined level close to the black level, the level of which is shifted by control in the control circuit, a bright control signal is applied to increase or decrease the brightness in the direction of canceling out this difference. An image quality adjustment circuit comprising: a brightness control circuit that generates and outputs to a brightness adjustment circuit; (2) The effective video signal extraction circuit extracts the effective video signal portion from the luminance signal output from the image quality adjustment circuit instead of the luminance signal input to the image quality adjustment circuit; The image quality adjustment circuit according to claim 1, characterized in that: (3) The bright control circuit creates a bright control signal that increases or decreases brightness based on the upper peak level detected by the upper peak level detection circuit and the lower peak level detected by the lower peak level detection circuit. , a lower peak level detected by the lower peak level detection circuit and a bright control signal for maintaining the black level or a predetermined level close to the black level are created and output to the bright adjustment circuit. The image quality adjustment circuit according to claim 2.