JPH05153519A - Video amplifier circuit - Google Patents

Abstract

PURPOSE:To obtain a video amplifier circuit in which a picture with fidelity is reproduced by correcting an increase/a decrease in the black level of a video signal in response to a change in an external light even in the manual adjustment or preset adjustment of the brightness and the contrast of the picture with a visual sense in a television receiver or the like. CONSTITUTION:An external luminous quantity 7 is detected by using a photosensor 1, control signals 10, 11 adjusting the brightness and the contrast of a video signal based on data numerized by the detection quantity and the control signals 10, 11 are used to correct automatically the increase/decrease in a black level of a video signal 8 in a video signal processing circuit 5.

Description

Detailed Description of the Invention

[0001]

[Industrial application] In video-related equipment such as TV receivers and display monitors, the amount of outside light is detected by a photo sensor to faithfully reproduce the image, and the brightness and contrast of the video signal are automatically adjusted to the optimum state for image reproduction. Regarding the circuit to be set.

[0002]

2. Description of the Related Art In order to faithfully reproduce an image on a picture tube surface, it is necessary to adjust the brightness and contrast of a video signal to an optimum adjustment state according to the amount of external light. Since the preset adjustment and the like are performed, there is a problem with a change in the amount of outside light. For example,
When changing from bright external light to dark external light, the contrast becomes too high and a black image of the black level of the video signal is easily noticeable to produce a bright image, and conversely the image is viewed in dark external light. When the state changes to bright outside light, the contrast becomes insufficient, and it is impossible to reproduce a faithful image such as a kopperi image in which black depression of the black level of the video signal is easily noticeable.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional example, and it is possible to change external light even in the manual or preset adjustment state of the brightness and contrast of an image visually by a television receiver or the like. Accordingly, the present invention provides a video amplifier circuit that corrects black floating and black sinking (black shadow) of a video signal to reproduce a faithful image.

[0004]

SUMMARY OF THE INVENTION The present invention detects a quantity of outside light using a photosensor, and a control signal for adjusting the brightness and contrast of a video signal in an arithmetic circuit based on data obtained by digitizing the detected quantity. Is generated, and the black level rise and the black level sink of the video signal in the signal processing circuit are automatically corrected by the control signal to obtain the video signal of the optimum contrast level.

[0005]

As shown in FIG. 1, a photosensor 1 for detecting an external light amount 7, a digitizing circuit 2 for outputting digitized external light amount data 9, and an arithmetic circuit for outputting control signals 10, 11 based on the data 9 3, a video signal input circuit 4, a signal processing circuit 5 that corrects the brightness and contrast level of the video signal, a video output circuit 6 that drives a picture tube, and the like. The brightness and contrast level of the input video signal 8 is adjusted in the signal processing circuit 5 by the brightness control signal 10 and the contrast control signal 11 which are generated based on 9.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram for automatically correcting the brightness and contrast of a video signal by a photo sensor for detecting the amount of external light.
Shown in. Further, FIG. 2 shows a conceptual diagram of the correction amounts of brightness and contrast according to the external light amount of FIG. Reference numeral 1 in FIG. 1 denotes a photosensor such as a photodiode or a phototransistor that detects the amount of external light 7, and 2 denotes a digitizing circuit that outputs data 9 that digitizes the detection amount of the photosensor 1 for easy processing. Is a brightness control signal 10 for correction by comparison with standard data of brightness and contrast preset based on the external light amount data 9 output from the digitizing circuit 2.
And a brightness control signal 5 for generating and outputting the contrast control signal 11, and a brightness control signal 10 and a contrast control signal 11 for adjusting the brightness and the contrast level of the video signal 8 output from the video signal input circuit 4, respectively. A signal processing circuit that has a manual and preset adjustment function for the height and contrast, and that corrects the black floating and black sinking (black crushing) of an image. Reference numeral 6 is an image output from the signal processing circuit 5 in which black floating and black sinking are corrected. This is a video output circuit that amplifies the signal to a predetermined level and drives a picture tube CRT.

FIG. 2A shows the input / output characteristics of the arithmetic circuit 3 with respect to the input external light amount (brightness) 7 of the photosensor 1.
This is a characteristic that the brightness also increases in the direction of increasing the amount of outside light 7. still,
ST indicates a preset standard data value of the arithmetic circuit 3,
+ And-indicate increase and decrease in brightness. 2B shows the characteristics of the brightness control signal 10 and the contrast control signal 11 of the generated output by comparison with the standard data ST set in advance in the arithmetic circuit 3. On a black floating screen where the amount of external light (brightness) 7 increases, the brightness level of the video signal in the signal processing circuit 5 is lowered to a predetermined value by the brightness control signal 10 and the contrast control signal 11 output from the arithmetic circuit 3.
Further, the contrast level is raised to a predetermined value to reproduce an image with optimum contrast without blackening. On the contrary, in the case of a black sunken screen in which the amount of external light (brightness) 7 decreases, the brightness level of the video signal in the signal processing circuit 5 is similarly raised to a predetermined value by the control signals 10 and 11 output from the arithmetic circuit 3.
Further, the contrast level is lowered to a predetermined value to reproduce an image with optimum contrast without blackout. It should be noted that the brightness and the contrast adjustment in the signal processing circuit 5 can be performed by both normal manual adjustment and preset adjustment.
In the automatic adjustment by the arithmetic circuit 3, automatic correction is performed centering on the set level of manual and preset adjustment.

[0008]

As described above, according to the present invention, the control signal for detecting the amount of outside light by using the photosensor and adjusting the brightness and contrast of the video signal in the arithmetic circuit based on the data obtained by digitizing the detected amount. By generating the image signal and automatically correcting the black level rise and the black level sink of the video signal in the signal processing circuit by the control signal to obtain the video signal of the optimum contrast level, the visual brightness and contrast of the image It is possible to configure a video amplifier circuit that reproduces a faithful image according to changes in external light even in the manual adjustment or preset adjustment state.

[Brief description of drawings]

FIG. 1 is a block diagram of a circuit for automatically correcting the brightness and contrast of a video signal by a photo sensor that detects the amount of external light.

FIG. 2 is a conceptual diagram of brightness and contrast correction amount for explaining FIG.

[Explanation of symbols]

 1 Photosensor 2 Numerical circuit 3 Arithmetic circuit 4 Video signal input circuit 5 Signal processing circuit 6 Video output circuit 7 External light amount 8 Video signal 9 Numerical data of external light amount 10 Brightness control signal 11 Contrast control signal

Claims (1)

[Claims] 1. In a video amplifier circuit of a television receiver or the like, based on a digitizing circuit for digitizing a photosensor output for detecting an external light amount so as to facilitate data processing, and an external light amount data output from the digitizing circuit. An arithmetic circuit that generates a signal that controls the brightness of the video signal and a signal that controls the contrast, and corrects the input video signal to a predetermined brightness and contrast level by the brightness control signal and the contrast control signal output from the arithmetic circuit. An image amplification circuit that consists of a signal processing circuit that does this, and an image output circuit that amplifies the corrected video signal output from the signal processing circuit and drives the picture tube CRT.