JPH11275386A - Automatic luminance adjusting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device which shows optimum contrast and brightness by adjusting a video level before A/D conversion so that a value divided by the number of samples of a pixel corresponding to a fixed area may be a prescribed value after inputting a signal of certain fixed luminance and performing cumulative addition of luminance value after the A/D conversion for a certain area of a screen. SOLUTION: An output of a video amplifier 1 is inputted to an A/D converter 2 and an output of the converter 2 is inputted to an accumulative adder circuit 6. The circuit 6 cumulatively adds only an area signal corresponding to a pulse timing generated by a pulse generation circuit 5. A cumulative addition result that is an output of the circuit 6 is inputted to a control circuit 7, a D/A converter 8 is controlled in accordance with the cumulative addition result and DC voltage which is for adjusting the amplitude and black level of the amplifier 1 is generated. For instance, when detection is performed in a pulse 1, the cumulative addition result is divided by a pixel number shown by a pulse to generate luminance data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video device for converting an analog video signal into a digital signal, such as a liquid crystal display device for sampling and displaying a video output signal of a personal computer or the like.

[0002]

2. Description of the Related Art As an example of a conventional brightness adjustment of contrast and brightness in a video device for converting an analog video signal into a digital signal, such as a liquid crystal display device for sampling and displaying a video output signal of a personal computer or the like, for example, An attempt has been made as shown in a contrast adjusting circuit of a color liquid crystal display device disclosed in Japanese Unexamined Patent Publication No. 6-60884. Hereinafter, a conventional automatic brightness adjustment device will be described with reference to the drawings.

FIG. 4 is a diagram showing a conventional automatic brightness adjusting device. 4, reference numeral 101 denotes a color liquid crystal display device;
02 is an R video signal, 103 is a G video signal, 104 is a B video signal, 105, 106 and 107 are reference voltages of A / D converters, 108 is a D / A converter, 109 is D / A converted data, 110 Is a CPU, 111 is an upper switch, 1
12 is a lower switch, 113 is an R video signal A / D converter, 114 is a G video signal A / D converter, 115 is a B video signal A / D converter, and 116 is an R video signal A / D converter. Digital video data 117 is a G video signal A
Digital video data of an A / D converter; 118, a digital video data of an A / D converter; 119, a dot clock synchronized with a video signal; 120, a liquid crystal;
21 is a horizontal synchronization signal, 122 is a vertical synchronization signal, 123 is a PLL circuit, 124 is a horizontal and vertical synchronization signal delay circuit, 1
27 is a contrast automatic adjustment switch, 128 is a video data selection circuit, 129 is a comparator, 130 is a data holding circuit, 131 is an RGB selection signal, 132 is digital video data, 133 is a comparison start / end control signal, and 134 is an initial value setting The signal 135 is the maximum value and the minimum value data of the digital video data, 136 is a selection switch, 137, 1
38 is a comparison result signal, 139 is a data holding signal, 140
Is a selection signal.

The vertical synchronizing signal 122 is input to the I / O
The signal is input to the O port to detect the occurrence of a vertical synchronization signal. The digital video data 116, 117, and 118 after A / D conversion are input to a video data selection signal 128, and RGB data transmitted from the CPU 110.
R, G, and B are selected by the selection signal 131.

A / D converted digital video data 132 selected from R, G, and B selected by the video data selection signal 128 is input to a comparator 129 and a data holding circuit 130. The data 135 held by the data holding circuit 130 is input to the comparator 129 and can be compared with the digital video signal 132. The comparison result signal 138 output when the comparison result is digital video data 132> held data 135
Selection can be made by the selection switch 136 according to a selection signal 140 sent from 110, and the selected result becomes a data holding signal 139, which is held by the data holding circuit 130, and which has the current maximum value or minimum value. The value data 135 is output.

Since the current reference voltage of the A / D converter is known, the maximum value and the minimum value are known, so the reference voltage is sent to the D / A converter 108 based on the data, and the A / D converter 113 , 114 and 115 can be adjusted to the optimum values. In the conventional example, the A / D converters 113, 1
The control of the reference voltages of 14, 115 is carried out.
The same applies to the case where the amplitude and the black level of the analog video signal are adjusted using a video amplifier or the like before the D converters 113, 114, and 115.

[0007]

As described above, when the maximum value and the minimum value of digital data are detected, there is a problem that noise is easily affected and the contrast cannot be adjusted stably.

That is, when the maximum value of the digital data is detected, and when noise is present in the screen even if only one pixel has a data value larger than the original video signal, a noise component is generated instead of the amplitude of the original analog video signal. Since the included amplitude is adjusted, the amplitude as the video signal becomes smaller than the amplitude to be obtained. In actual equipment, noise is generated due to various disturbances such as a transmission path of an analog video signal and a power supply system, and it is almost impossible to reduce the noise in one screen to zero. Therefore, the contrast cannot be adjusted stably.

In view of the above-mentioned problems, the present invention takes a signal of a certain luminance as an input, accumulates the luminance value after A / D conversion for a certain area of the screen, and calculates the number of pixels of the pixel corresponding to the certain area. It is an object of the present invention to provide an automatic brightness adjusting device that can obtain an optimum contrast and brightness by adjusting a video level before A / D conversion so that a divided value becomes a desired value.

[0010]

In order to solve the above-mentioned problems, an automatic brightness adjusting device according to the present invention comprises a video amplifier for adjusting an amplitude and a black level of an input signal, and a digital signal for sampling an output of the video amplifier. Convert to A /
A D converter, a horizontal counter that counts the number of dot clocks based on a horizontal synchronization signal of the input signal, a vertical counter that counts the number of lines of the horizontal synchronization signal based on a vertical synchronization signal of the input signal, A pulse generation circuit for decoding a value of a horizontal counter and a value of the vertical counter to generate a plurality of pulses, and the A / D converter only in a pulse region indicating an arbitrary portion of a screen generated by the pulse generation circuit A cumulative addition circuit for cumulatively adding digital data output from the CPU, a control circuit for dividing the result of the cumulative addition circuit by the number of samples, and controlling a D / A converter based on the value, and a control circuit controlled by the CPU. A D / A converter that outputs a DC level to be input to the video amplifier; a digital data output of the A / D converter, a clock; The generated horizontal sync signal in the pulse generating circuit is obtained by comprising the liquid crystal panel for inputting a vertical synchronizing signal.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An automatic brightness adjusting apparatus according to a first aspect of the present invention receives a signal of a certain brightness as an input, and executes an A / D conversion.
After cumulatively adding the converted luminance value for a certain area of the screen, A / A is adjusted so that the value obtained by dividing by the number of samples becomes a desired value.
Adjusting the video level before the D conversion has an effect that an optimum contrast and brightness can be obtained.

According to a second aspect of the present invention, there is provided an automatic brightness adjusting apparatus for adjusting the amplitude and the black level of an input signal, and an A / D for sampling an output of the video amplifier and converting the output into a digital signal. A converter, a horizontal counter that counts the number of dot clocks based on a horizontal synchronization signal of the input signal, a vertical counter that counts the number of lines of the horizontal synchronization signal based on a vertical synchronization signal of the input signal, and A pulse generation circuit that decodes a value of a counter and a value of the vertical counter to generate a plurality of pulses, and that the A / D converter includes only a pulse region indicating an arbitrary portion of a screen generated by the pulse generation circuit. An accumulating circuit for accumulating and adding digital data as an output, and dividing the result of the accumulating circuit by the number of samples, based on the value. / A control circuit for controlling the A converter, and a D / A converter for outputting a DC level to be input to the video amplifier is controlled from the CPU, the A /
A liquid crystal panel for inputting a digital data output of a D converter, a clock, and a horizontal synchronizing signal and a vertical synchronizing signal generated by the pulse generating circuit, to obtain optimal contrast and brightness. Has the effect of being able to.

Hereinafter, an embodiment of the present invention will be described.
This will be described with reference to FIGS.

(Embodiment 1) FIG. 1 is a view showing an embodiment of an automatic brightness adjusting device according to the present invention.
Is a video amplifier, 2 is an A / D converter, 3 is a horizontal counter, 4 is a vertical counter, 6 is a cumulative addition circuit, 7 is a control circuit, 8 is a D / A converter, and 9 is a liquid crystal panel.

FIG. 2 is a diagram showing the internal configuration of the accumulator 6. In FIG. 2, reference numeral 10 denotes an AND circuit, 11 denotes a first data type flip-flop (hereinafter referred to as DFF), 12 denotes an adder, and 13 denotes a second adder. DFF. FIG. 3 is a diagram showing an input signal and a region pulse.

The operation of the automatic brightness adjusting device according to the present invention will be described with reference to FIGS. 1, 2 and 3.

The input analog video signal is adjusted in amplitude and black level by the video amplifier 1. As a result, the dynamic range of the subsequent A / D converter 2 can be used effectively, and the white balance of each of the RGB colors can be adjusted.

For example, the black level is adjusted by the brightness of the video amplifier. Generally, the black level is adjusted by changing a DC voltage input to an input pin called brightness in a video amplifier.

For white balance adjustment, similarly, the video amplifier has input pins called sub-contrast and sub-brightness for each of the RGB colors, and D is input to these pins.
The adjustment is performed by changing the C voltage so that the contrast and brightness can be independently adjusted for each of the RGB colors.

The A / D converter 2 sequentially converts the output of the video amplifier 1 into a digital video signal in synchronization with the input clock. On the other hand, the horizontal counter 3 counts up the number of clocks starting from the input horizontal synchronizing signal, and outputs the count value. Similarly, the vertical counter 4 counts up the number of horizontal synchronizing signals starting from the input vertical synchronizing signal, and outputs the counter value.

The pulse generating circuit 5 generates an arbitrary pulse based on the output of the horizontal counter 3 and the output of the vertical counter 4. For example, as shown in FIG. 3A, the left half is all white (luminance 90%), and the right half is all black (luminance 10%).
When a signal for displaying a screen is input, a pulse to be generated is a pulse 1 for selecting a central area in the left half of the screen as shown in FIG. 3 (2), and a pulse as shown in FIG. 3 (3). A pulse 2 for selecting the central region of the right half is generated.
As shown in FIGS. 3 (2) and 3 (3), the size of each area is not particularly limited, and the pulse 2 is output so as to correspond to an area of an arbitrary size. In the case of this embodiment, the respective numbers of the pulse 1 or the pulse 2 are as shown in FIG.
Since the number of pixels corresponds to the area of the region shown in (2),
It is the number of horizontal pixels × the number of vertical lines. For example, horizontal 10
When 0 dots and 30 vertical lines are detected, the number of pixels is 3
000, 3000 pulses.

The output of the video amplifier 1 is input to the A / D converter 2, and the output of the A / D converter 2 is
Is input to The accumulative addition circuit 6 accumulatively adds only signals in a region corresponding to the timing of the pulse generated by the pulse generation circuit 5 (regions shown in FIGS. 3B and 3C).

FIG. 4 is a timing chart of signals to be cumulatively added. FIG. 4B shows data output from the A / D converter 2, and FIG. 4C shows FIG. 3B or FIG.
And is output from the pulse generation circuit 5. The accumulator 6 is a pulse generator 5
The data sent from the A / D converter 2 during the period in which the area setting pulse (FIG. 4C) output from is input. In FIG. 4, data for 6 clock periods (the number of samples is 6) are cumulatively added.

The result of the cumulative addition, which is the output of the cumulative adding circuit 6, is input to the control circuit 7, and D is added in accordance with the result of the cumulative addition.
The A / A converter 8 is controlled to generate a DC voltage for adjusting the amplitude and the black level of the video amplifier 1. For example, when detection is performed with pulse 1 (FIG. 3 (2)), luminance data per sample is obtained by dividing the cumulative addition result by the number of pixels indicated by pulse 1.

In this embodiment, since the adjustment is performed using the input signal in the state shown in FIG. 3A, that is, since the input signal has a luminance of 90%, in the case of an 8-bit A / D converter, 2 is used.
The contrast is adjusted to be 55 × 0.9230. Similarly, when detection is performed with pulse 2, by dividing the cumulative addition result by the number of pixels indicated by pulse 2,
The luminance data per sample is obtained. Since the luminance of the input signal is 10%, in the case of an 8-bit A / D converter, the brightness is adjusted to be 255 × 0.125. If the brightness is adjusted at a luminance of 10% after adjusting the contrast at a luminance of 90%, the detection result at the luminance of 90% shifts, so the contrast is adjusted again. The adjustment of contrast and brightness is repeated many times, and adjustment is performed so that both the luminance of 90% and the luminance of 10% become the target average luminance.

In the automatic brightness adjusting apparatus according to the present embodiment, in order to multiply the detected brightness data by the area, for example, when a signal having a brightness of 90% is input and the half value of the value to be obtained by the contrast is simply (simple). Therefore, the brightness is assumed to be optimal), and in an 8-bit A / D converter, digital data is 255 × 90% × 0.51
The optimum contrast can be obtained by changing the contrast from 0.5 to 1. In the same state, in the conventional automatic brightness adjustment device, when the noise of 150 pixels of digital data is included for one pixel when the contrast is half, the detected maximum value is 150 of the pixel including the noise. To try to make 150 into 230, the contrast is only changed from 0.5 to about 0.76. The contrast cannot be adjusted correctly due to the noise of one pixel.

However, in the automatic brightness adjusting device of the present invention,
In order to find the average luminance of luminance data for a certain area, even if the digital data 150 contains noise, if the number of pixels to be detected is 30,000, the average luminance data is (29).
999 × 115 + 150) / 30000 115, which indicates that the circuit is not affected by noise.

As described above, the input of the A / D converter 2 is A / D
The dynamic range of the converter 2 becomes full, and optimum contrast and brightness can be obtained. The pulse generation circuit 5 generates a horizontal synchronization signal and a vertical synchronization signal in addition to the pulse indicating the area to be detected, and supplies the signal to the liquid crystal panel 9 together with the digital output of the A / D converter 2. Note that the input signals are set to have a luminance of 90% and a luminance of 10% at 100% luminance and 0% luminance, because the output of the A / D converter 2 is limited. This is because the correlation between them is lost. The reason why the pulse indicating the area is not full is to avoid the influence of, for example, top curl due to PLL disturbance.

According to this configuration, it is possible to obtain an optimum contrast and brightness without being affected by noise.

As described above, at the time of factory shipment adjustment in the production of products, by inputting a signal as shown in FIG. 3 from the signal generator, the contrast due to the variation of parts in the analog circuit and the variation of the A / D converter can be improved. Deviations such as brightness and white balance can be adjusted. In addition, for example, by preparing the image data such as a bitmap file or distributing the signal as shown in FIG. 3 on a floppy disk or the like, it is possible for the user to adjust not only the factory shipment but also the actual use condition. Is also possible.

[0031]

As described above, according to the automatic brightness adjusting device of the present invention, since the average brightness of the brightness data of a certain area is obtained, the optimum contrast without the influence of noise is obtained.
Brightness can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an automatic brightness adjustment device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an internal configuration of a cumulative addition circuit of the device.

FIG. 3 is a diagram showing an input signal and a region pulse according to the embodiment of the apparatus.

FIG. 4 is an operation diagram of a cumulative addition circuit according to the present invention.

FIG. 5 is a circuit configuration diagram of a conventional automatic brightness adjustment device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Video amplifier 2 A / D converter 3 Horizontal counter 4 Vertical counter 5 Pulse generation circuit 6 Cumulative addition circuit 7 Control circuit 8 D / A converter 9 Liquid crystal panel 10 AND circuit 11, 13 DFF 12 Adder

Claims (2)

[Claims] 1. An A / D converter having a signal of a certain luminance as an input.
After cumulatively adding the converted luminance value for a certain area of the screen, A / A is adjusted so that the value obtained by dividing by the number of samples becomes a desired value.
An automatic brightness adjustment device that adjusts the video level before D conversion to obtain optimal contrast and brightness. 2. A video amplifier for adjusting an amplitude and a black level of an input signal, an A / D converter for sampling an output of the video amplifier and converting the output to a digital signal, and a dot based on a horizontal synchronization signal of the input signal. A horizontal counter that counts the number of clocks; a vertical counter that counts the number of lines of the horizontal synchronization signal based on a vertical synchronization signal of the input signal; a value of the horizontal counter; A pulse generation circuit for generating a pulse, a cumulative addition circuit for cumulatively adding digital data output from the A / D converter only in a pulse region indicating an arbitrary part of a screen generated by the pulse generation circuit, A control circuit for dividing the result of the accumulating circuit by the number of samples and controlling the D / A converter based on the value; A D / A converter controlled by the D / A converter to output a DC level to be input to the video amplifier;
An automatic brightness adjusting device comprising a liquid crystal panel for inputting a digital data output of a / D converter, a clock, and a horizontal synchronization signal and a vertical synchronization signal generated by the pulse generation circuit.