JPS62262584A - Automatic brightness setting system for video device - Google Patents

Abstract

PURPOSE:To quickly correct brightness by digitally and instantaneously averaging the digital signals of all picture elements read out fo a frame memory at every frame. CONSTITUTION:A video signal showing an object 1 image-picked up by an image pickup part 2 is transmitted to an adder circuit 14 from a video signal amplifier 5. Its output is A/D-converted and stored in the frame memory 8. The digital video signal stored in the frame memory 8 is D/A-converted and displayed on a display part 6. The mean value of digital signal level at every frame is calculated at a digital calculation part 12 as for the digital signals outputted from the frame memory 8. The mean value is D/A-converted and applied to a difference voltage detection part 10. It obtains the difference between the voltage and that of brightness set outside, and supplies the difference voltage as a correction signal to the adder circuit 14.

Description

[Detailed Description of the Invention] [Summary] In the 9JJ brightness setting method of a video device, when a video signal captured by an imaging unit is set to a predetermined brightness level and displayed as an image, the video signal is converted into a digital signal. Digitally calculate the average level of the video signal for each frame, detect the voltage difference between the calculated average level and the externally set brightness level, and add the detected voltage difference to the set brightness level to calculate the video signal for each frame. The display brightness of the image is corrected to be constant depending on whether the average level is large or small, and it is possible to automatically correct fluctuations in the average brightness level caused by contrast switching etc. at high speed. It is said that

[Industrial application field]

The present invention relates to an automatic brightness correction method for a video device, and more particularly to an automatic brightness correction method for a video device that can automatically correct fluctuations in average brightness level caused by contrast switching or the like at high speed.

[Conventional technology]

FIG. 3 shows a block diagram of an automatic brightness correction method for a conventional video device.

In FIG. 3, an image display circuit of a conventional imaging device scans a subject l using an optical system such as a scanning mirror, captures optical information of the subject 1, and uses multi-element detectors 2-1 to 2-n. an imaging unit 2 that photoelectrically converts the video signal into a video signal, a video signal amplification circuit 5 that amplifies the output video signal of the imaging unit 2, and an A/D conversion that converts the output video signal of the video signal amplification circuit 5 into a digital signal. a frame memory 8 which stores and outputs the output digital signal of the A/D converter 7 frame by frame, and a D/D converter which converts the digital signal outputted from the frame memory 8 into an analog signal and displays the image. A converter 1
1 and a display section 6.

In addition, the brightness correction circuit for the display image includes a multi-element detector 2-1.
An average value calculation circuit 4 that adds the output video signals of arbitrary detectors within ~2-n and divides by the number of detectors to create the average value, and smoothes the output video signal of the average value calculation circuit 4. a filter circuit 3 that detects a difference between the average output value of the filter circuit 3 and an externally set brightness voltage; The adder circuit 14 includes an adder circuit 14.

The video signal of the subject 1 photoelectrically converted by the multi-element detectors 2-1 to 2-n is amplified by the video amplification circuit 5, and the brightness level is set by an externally set brightness voltage A and displayed on the display unit 6 for each frame. The image is displayed.

On the other hand, the output video signals of any one of the detectors 2-1 to 2-n are taken out and added in the average value calculation circuit 4, and then divided by the number of the random detectors to calculate the average value. It is detected and input to the filter circuit 3 as an averaged video analog signal. The filter circuit 3 smoothes the averaged video analog signal and outputs it as a DC voltage to one input terminal of the differential voltage detection section 10.

The differential voltage detection unit 10 detects the difference value between the output DC voltage of the filter circuit 3 and the externally set brightness voltage inputted to the other input terminal, and outputs it to the addition circuit 14 .

The adder circuit 14 adds the difference voltage and the video signal, and corrects the display brightness of the video signal to be constant.

[Problem that the invention seeks to solve]

In the automatic brightness correction method of the above-mentioned video equipment, the filter circuit is composed of a capacitor C and a high resistance R, and the time constant is large to form a perfect DC voltage, which reduces the correction response speed. There is a problem that it is slow.

The present invention was created in view of these points, and it is an object of the present invention to provide an automatic brightness setting method that can quickly correct fluctuations in brightness levels caused by contrast fluctuations and the like.

[Means for solving problems]

In order to increase the response speed, in place of the average value calculation circuit 4 and filter 3 that create an average level using a direct current video analog signal, the average level of all pixels for each frame of video is calculated in the process of digital signal processing. The configuration includes a digital calculation section 12 for calculation.

[Effect]

The digital calculation unit 12 digitally calculates the average level of all pixels for each frame at high speed, and creates a corrected brightness level that corresponds to fluctuations in the video brightness level at high speed.

〔Example〕

Fig. 1 is a block diagram of an automatic brightness correction method for a video device according to an embodiment of the present invention, and Fig. 2! 81~(dl indicates a signal waveform diagram for explaining one embodiment.

In FIG. 1, the image display circuit of the video device of one embodiment is as follows:
The object l is scanned using an optical system such as a scanning mirror, and the object l is
an imaging unit 2 that captures optical information and photoelectrically converts it into a video signal by multi-element detectors 2-1 to 2-n; a video signal amplification circuit 5 that amplifies the output video signal of the imaging unit 2; A Δ/D converter 7 that converts the output video signal of the signal amplification circuit 5 into a digital signal, a frame memory 8 that stores and outputs the output digital signal of the A/D converter 7 for each frame, and a frame memory 8. It is comprised of a D/A converter 11 and a display section 6 that convert digital signals output from the converter into analog signals and display images.

The display image brightness correction circuit also includes a digital calculation section 12 that calculates the average value of the digital signal level for each frame outputted from the frame memory 8, and a digital calculation section 12 that converts the output average digital signal of the digital calculation section 12 into an analog signal. a D/A converter 13 that detects the difference between the average analog signal voltage output from the D/A converter 13 and an externally set brightness voltage; an amplifier 9 that amplifies the differential voltage to a predetermined level;
and an adder circuit 14 that adds the output voltage of the amplifier 9 and the video signal.

Image display is performed by amplifying the video signal of the subject I, which has been charged and converted by the multi-element detectors 2-1 to 2-n, in the video amplifying circuit 5, and adding it to the brightness correction signal in the adding circuit 14, for each frame. is displayed on the display section 6.

On the other hand, the brightness correction of the displayed image is shown in Figure 2 (al~(d+f
This will be explained with reference to the No. a waveform diagram.

The video signal as shown in FIG. 2 (al) is stored as a digital signal every frame in the frame memory 8,
The data are sequentially output to the digital calculation section 12.

The digital calculation unit 12 calculates the average voltage of the digital signal for every l frame that is sequentially input,
2 is instantaneously calculated, and the difference ΔV is output, which is converted into an analog signal via the D/A converter 13 and sent to the difference voltage detection unit lO.
Output to.

Now, as shown in FIG. 2 (al), when the video signal level of the second frame becomes higher than the video signal level of the first frame, the differential voltage detection unit 10 detects The average value v2 of the digital signals of all pixels of the second frame outputted from the frame memory 8 is compared with the externally set brightness voltage A, the difference voltage Δv3 is detected, and the negative potential Δ
V3A is created, amplified by the amplifier 9, and output to the adder circuit 14.

With the above luminance correction circuit, the output video signal due to the change in ΔV of the input video signal is expressed by the following equation.

Vout=ΔV-A (Vout-VBRT)Vo
ut = 1/1 +A (ΔV + A x VBRT
)Vout = (ΔV/1 +A) + (A/1 +
A) xVBRT (11)

However, A is the amplification degree of the amplifier, V B)? T indicates an externally set brightness voltage, and VouL indicates an output voltage of the frame memory.

Now, when A>1, (from equation 11, Vout = VBR
It becomes T. This indicates that the output video signal is determined only by the externally set voltage.

In this way, a control system is configured by each of the circuits, and the brightness level is automatically corrected with respect to the average level of the video signal, and images are displayed at a constant brightness level as shown in FIG. 2(d). .

On the other hand, if the video signal level of the second frame becomes lower than the video signal level of the first frame, a correction operation opposite to the above is performed to correct the decrease in display brightness due to the decrease in the video signal level and keep it constant. Displays an image of brightness.

〔Effect of the invention〕

As described above, according to the present invention, high-speed brightness correction is possible by instantaneously calculating by digital calculation the average value of the digital signals of all pixels for each frame read from the frame memory.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an automatic brightness correction method for a video device according to an embodiment of the present invention, Fig. 2 (a) to [d] are signal waveform diagrams for explaining an embodiment, and Fig. 3 is a conventional method. FIG. 2 is a block diagram of an automatic brightness correction method for the video device of FIG. In the figure, ■ is the subject, 2 is the imaging unit, 2-1 to 2-n
3 is a filter circuit, 4 is an average value calculation circuit, 5 is a video signal amplification circuit, 6 is a display section, 7 is an A/D converter, 8 is a frame memory, 9 is an amplifier, 10 is a A differential voltage detection section, 11.13 is a D/A converter, 12 is a digital calculation section, and 14 is an addition circuit. Shito A5 Dangetsu'' Ichidai 7th generation example sr 侭-g-をノ艙zl
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Claims (1)

[Scope of Claims] A video device that converts a captured video signal into a digital signal and stores it in memory for each frame, and displays the stored video signal for each frame with brightness at an externally set brightness level, comprising: a digital calculation unit (12) that calculates the average level of the digital signal level for each frame;
A difference voltage detection part (10) is provided to detect a difference voltage between the output level of the digital calculation part and the externally set brightness level, and the average level of the video signal is corrected by the detected difference voltage. Automatic brightness setting method for video equipment.