JPH11252408A - Luminance adjusting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform optimum A/D conversion with respect to an analog video signal by adjusting the black label and amplitude of the analog video signal so that a video start and end coordinates detected by comparing the luminance data of a digital video signal of an A/D converter output with a comparison value agree with the ideal values of a detection coordinate determined from the signal waveform of a video signal to be displayed. SOLUTION: A video amplifier 1 adjusts the black label and amplitude of an analog video signal inputted by a personal computer, an A/D converter 2 converts the analog video signal into a digital video signal, a video start and end coordinate detection circuit 3 compares the luminance data of the digital video signal with a comparison value and detects the video start and end coordinate. a microcontroller 4 controls the amplifier 1, based on video start and end coordinate detection data detected by the circuit 3. As a result, it is possible to determine the black label and amplitude of the analog video signal that is optimum for the converter 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, such as a liquid crystal display or a plasma display, which digitizes and displays an analog video signal and adjusts the black level and amplitude of the analog video signal input to the AD converter. The present invention relates to an adjusting device.

[0002]

2. Description of the Related Art Conventionally, as shown in Japanese Patent Publication No. Hei 8-106684, a digital display device after analog-to-digital conversion has been used to optimally adjust the number of clocks of an analog-to-digital converter and the screen display position. There has been a detection circuit that detects video start / end coordinates from a video signal.

Further, as shown in Japanese Patent Publication No. 2-168296, the most significant bit output signal of the AD converter is
There has been an adjusting device for adjusting the contrast by adjusting the reference voltage of the converter. Note that the same effect can be obtained by adjusting the black level and amplitude of the analog video signal with a video amplifier in the preceding stage of the AD converter instead of the reference voltage of the AD converter.

[0004]

However, since the contrast adjustment shown in the prior art can determine only the binary value of the brightness data after AD conversion, the optimum AD conversion for the analog signal input to the AD converter is performed. This cannot be performed, and a circuit for detecting the most significant bit output signal of the AD converter is required. Therefore, there is a problem that the circuit scale of the display device becomes large.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a brightness adjustment device that does not require a dedicated circuit for brightness adjustment and enables optimal AD conversion on an analog video signal.

[0006]

In order to solve the above-mentioned problems, a luminance adjusting apparatus according to the present invention compares the luminance data of a digital video signal output from an AD converter with a comparison value to determine the video start / end coordinates. The analog video signal is adjusted by adjusting the black level and amplitude of the analog video signal so that the detection result of the video start / end coordinate detection circuit to be detected matches the detection ideal value determined from the signal waveform of the video signal to be displayed. It is possible to realize an optimal AD conversion for a signal.

The amplitude of the analog video signal is adjusted by minimizing the difference between the detected video end coordinate and the detected video start coordinate by making the comparison value the full scale of the output of the A / D converter. Effective AD conversion can be realized without depending on the pattern.

The detection circuit used in the adjusting device of the present invention has been conventionally used for adjusting the number of clocks of the AD converter, and thus does not require the addition of a dedicated circuit.

[0009]

The invention according to claim 1 of the present invention determines an image start / end coordinate detected from a luminance level of an analog image signal after AD conversion and a signal waveform of the image signal to be displayed. The brightness adjustment device adjusts the black level and amplitude of the analog video signal to optimal values for the AD converter by making the ideal values of the detected coordinates coincide with each other, and requires a specific video signal pattern. Since the adjustment is performed using the video start / end coordinate detection circuit of the conventional liquid crystal display device, the black level and amplitude of the analog video signal can be adjusted to realize the optimal AD conversion without adding a dedicated circuit. The value can be determined.

According to a second aspect of the present invention, there is provided a video amplifier for amplifying an analog video signal, an AD converter for AD converting the analog video signal output from the video amplifier, and a digital video output from the AD converter. A video start / end coordinate detection circuit for detecting the video start / end coordinates by comparing the luminance data of the signal with a comparison value, and a signal waveform of the video signal to be displayed with the detection values of the video start / end coordinate detection circuit And a microcontroller that controls the video amplifier so that the detection ideal value determined from the above becomes equal to adjust the black level and the amplitude of the analog video signal output from the video amplifier to optimal values for the AD converter. ing.

According to this configuration, a specific video signal pattern is required. However, since the adjustment is performed using the video start / end coordinate detection circuit of the liquid crystal display device, a dedicated circuit is added. It is possible to determine the black level and the amplitude adjustment value of the analog video signal that realizes the optimum AD conversion without performing.

According to a third aspect of the present invention, the difference between the video end / start coordinates detected by comparing the luminance level of the analog video signal after AD conversion with the full scale of the output of the AD converter is minimized. This is a brightness adjustment device that adjusts the amplitude of the analog video signal to an optimal value for an AD converter, and performs adjustment using a video start / end coordinate detection circuit conventionally provided in a liquid crystal display device. Therefore, it is possible to determine the amplitude adjustment value of the analog video signal that realizes the optimal AD conversion without adding a dedicated circuit, and a specific video pattern is not required as an input signal.

According to a fourth aspect of the present invention, there is provided a video amplifier for amplifying an analog video signal, an AD converter for AD converting the analog video signal output from the video amplifier, and a digital video output from the AD converter. A video start / end detection circuit for detecting the video start / end coordinates by comparing the luminance data of the signal and the comparison value, and the video end coordinates and the video detected by making the comparison value the full scale of the output of the AD converter A microcontroller that controls the video amplifier so that the difference between the start coordinates is minimized, thereby adjusting the amplitude of the analog video signal output from the video amplifier to a value optimal for the AD converter.

According to this configuration, since the adjustment is performed by using the video start / end coordinate detection circuit conventionally provided in the liquid crystal display device, the analog video that realizes the optimal AD conversion without adding a dedicated circuit. The amplitude adjustment value of the signal can be determined, and no specific video pattern is required as an input signal.

Hereinafter, an embodiment of the present invention will be described.
This will be described with reference to FIGS. (Embodiment 1) FIG. 1 is a block diagram of the present invention, in which 1 is a video amplifier for adjusting the black level and amplitude of an analog video signal input from a personal computer, and 2 is the output of 1 An analog-to-digital (AD) converter for converting the converted analog video signal into an 8-bit digital video signal. Reference numeral 3 denotes a video start for detecting the video start / end coordinates by comparing the luminance data of the output digital video signal 2 with the comparison value. An end coordinate detection circuit, and 4 is a microcontroller that controls 1 based on the video start / end coordinate detection data detected by 3. Reference numeral 4 is conventionally used for adjusting the number of clocks of an AD converter.

FIG. 2 is a diagram showing the luminance distribution with respect to the horizontal coordinate of the video signal when the lamp signal is used as the input signal. The black level and amplitude of the analog video signal are not optimal for the AD converter, and the digital signal after the AD conversion is obtained. The signal is white and black is lost. ST1 and ED1 in FIG. 2 are a video start position (ST1) and a video end position (ED1) when the comparison value of the video start / end coordinate detection is set to 1, and
2. ED2 is the comparison value for detecting the start and end coordinates of the video which is 128
Are the video start position (ST2) and the video end position (ED2).

With this configuration, when the horizontal video pixel receives a 1024 ramp signal, if the number of clocks for AD conversion is optimally adjusted, the black level and amplitude of the analog signal are optimally adjusted for the AD converter. The difference between ED1 and ST1 when adjusted to an appropriate value is 1000 (1024-1024).
* 1/255), and the difference between ED2 and ST2 is 510
(1024-1024 * 128/255). Thus, the microcontroller 4 of FIG. 1 sets the luminance comparison value of the video start / end coordinate detection circuit 3 to 1, and
The video amplifier 1 is controlled to adjust the black level so that (ED1−ST1 = 1000), and the comparison value 12
8 (ED2−ST2 = 512) to control the video amplifier 1 to perform amplitude adjustment, and
The optimum black level and amplitude adjustment value of the analog video signal for the converter can be determined.

Next, another embodiment of the present invention will be described with reference to FIGS. 1, 3 and 4. FIG. Note that the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted. (Embodiment 2) In this embodiment, the microcontroller 4 shown in FIG. 1 uses the brightness comparison value of the video start / end coordinate detection circuit 3 as a full scale of the output of the AD converter, that is, 255.
After that, the amplitude adjustment value of the analog amplifier 1 is set to the maximum value. At this time, since the high luminance area of the analog video signal exceeds the dynamic range of the AD converter as shown in FIG. 3, a white area occurs in the digital video signal.

From this state, the microcontroller 4 gradually lowers the amplitude adjustment value of the video amplifier 1 and stops reducing the amplitude at an amplitude value at which the difference between the video end coordinates and the video start coordinates is minimized. FIG. 4 shows the luminance distribution with respect to the horizontal coordinate of the video signal at this time. Note that the Star in FIGS.
t and End are the image start coordinates (St) detected by the detection circuit 3.
art) and the image end coordinates (End).

According to this configuration, the maximum luminance of the video signal can be made to match the full scale of the output of the AD converter, and the amplitude adjustment value of the analog video signal that realizes the optimal AD conversion can be determined. .

[0021]

As described above, according to the brightness adjusting apparatus of the present invention, the video start / end for detecting the video start / end coordinates by comparing the brightness data after analog-to-digital conversion of the analog video signal with the comparison value. By making the detection value of the coordinate detection circuit coincide with the ideal value of the detection coordinates determined from the signal waveform of the video signal to be displayed, the black level and amplitude of the analog video signal can be adjusted to the optimum values for the AD converter. Can be adjusted.

The amplitude of the analog video signal is adjusted to an optimal value for the A / D converter by minimizing the difference between the end and start coordinates of the video detected using the comparison value as the full scale of the output of the A / D converter. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram of a brightness adjusting device according to the present invention.

FIG. 2 is a luminance distribution diagram with respect to horizontal coordinates when a ramp signal is input;

FIG. 3 is a luminance distribution diagram with respect to horizontal coordinates during amplitude adjustment according to the second embodiment of the present invention.

FIG. 4 is a luminance distribution diagram with respect to horizontal coordinates after amplitude adjustment is completed according to the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Video amplifier 2 AD converter 3 Video start / end coordinate detection circuit 4 Microcontroller

Continued on the front page (72) Inventor Taro Funamoto 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] An image processing apparatus according to claim 1, wherein an image start / end coordinate detected from a luminance level of the analog video signal after AD conversion is made to coincide with an ideal value of the detected coordinate determined from a signal waveform of a video signal to be displayed. A brightness adjusting device for adjusting a black level and an amplitude of the analog video signal to optimal values for an AD converter. 2. A video amplifier for amplifying an analog video signal, and an analog video signal output from the video amplifier,
The A / D converter to be converted and the brightness data of the digital video signal output from the A / D converter are compared with the comparison value to start the video.
A video start / end coordinate detection circuit for detecting end coordinates, and the video amplifier such that a detection value of the video start / end coordinate detection circuit matches a detection ideal value determined from a signal waveform of a video signal to be displayed. And a microcontroller for adjusting the black level and amplitude of the analog video signal output from the video amplifier to optimal values for the AD converter. 3. The amplitude of the analog video signal can be reduced by minimizing the difference between the video end / start coordinates detected by comparing the luminance level of the analog video signal after AD conversion with the full scale of the output of the AD converter. A brightness adjustment device that adjusts to the optimal value for the AD converter. 4. A video amplifier for amplifying an analog video signal and an analog video signal output from the video amplifier.
The A / D converter to be converted and the brightness data of the digital video signal output from the A / D converter are compared with the comparison value to start the video.
A video start / end detection circuit for detecting end coordinates, and controlling the video amplifier so that the difference between the detected video end coordinates and the detected video start coordinates by making the comparison value the full scale of the output of the AD converter is minimized. And a microcontroller for adjusting the amplitude of the analog video signal output from the video amplifier to an optimal value for the AD converter.