KR20000047548A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: A liquid crystal display device is provided to easily adjust the voltage variation of input image signal. CONSTITUTION: A liquid crystal display device includes an amplifier, an A/D converter(18), a signal processor circuit, and a liquid crystal display panel(21). The amplifier amplifies analog image signal. The signal processor circuit includes an on screen mixer circuit(19) mixing the output of the A/D converter and an on screen display signal. The liquid crystal display panel(21) is operated according to the digital output of the signal processor circuit. The signal processor circuit generates the digital output representing the region corresponding to the maximum value of the analog image and a test pattern of the maximum level. The amplifier is operated according to the input of an operator so as to change the gain of the amplifier. The output of the amplifier is regarded as the input voltage of the maximum level of the A/D converter.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, particularly a liquid crystal display device which is easy to adjust for dispersion of voltage amplitude of an input video signal.

In a liquid crystal display device, a video signal is input from video signal generating means such as a television receiver or a video tape recorder, and the video is displayed on a liquid crystal panel. In this case, the video signal input from the video signal generating means is prescribed to have a predetermined voltage amplitude, but there is some dispersion depending on the type of the video signal generating means or the like. Therefore, in order to effectively exhibit the gradation characteristics of the liquid crystal display device, it is necessary to adjust the video signal input from the video signal generating means to the optimum voltage amplitude on the liquid crystal display device side.

In general, a liquid crystal display device converts an analog video signal input from a video signal generating means into a digital signal with an A / D converter, and drives the liquid crystal panel with the digital signal. Therefore, in the liquid crystal display device, the voltage amplitude of the analog video signal before conversion to the digital signal is adjusted to correct the dispersion of the video signal input from the video signal generating means.

Here, the A / D converter converts the analog signal into a full-scale digital signal when an analog signal having a prescribed voltage amplitude is input. For example, in the case of a specification in which 256-gradation resolution is displayed with 8 bits when a video signal having a voltage amplitude of 2V is input to an A / D converter, the voltage amplitude of the video signal input from the video signal generating means is 0.7V. In this case, when the video signal input from the video signal generating means is amplified by an amplification circuit having an amplification rate of 2V ÷ 0.7V = about 2.86 times and input to the A / D converter, the A / D converter inputs the video signal in full-scale digital form. Can be converted into a signal.

On the other hand, when the voltage amplitude of the video signal input from the video signal generating means is 0.8V, the voltage amplitude input to the A / D converter becomes 0.8V x 2.86 times = 2.29V in the amplification circuit having an amplification factor of about 2.86 times. . In this case, since the voltage amplitude of the video signal input to the A / D converter exceeds 2.0 V, the output of the A / D converter is saturated and the gray level of the video signal inputted cannot be accurately reproduced.

On the contrary, when the voltage amplitude of the video signal input from the video signal generating means is 0.6V, the voltage amplitude input to the A / D converter is 0.6V x 2.86 times = 1.72V. In this case, 256 gradations, the resolution of the A / D converter, cannot be saved, so the number of colors displayed is reduced.

Therefore, in order to correct the dispersion of the voltage amplitude of the video signal input from the video signal generating means, the user needs to adjust the amplification ratio of the amplifying circuit that amplifies the video signal to the optimum value while looking at the screen displayed by the video signal generating means. .

As described above, conventionally, the video signal generating means inputs the highest luminance, for example, a white video signal to the liquid crystal display device, and the user adjusts the amplification ratio of the amplifying circuit while viewing the white display displayed on the liquid crystal display device.

However, in order to realize accurate color reproducibility with a liquid crystal display, it is necessary for the user to adjust the amplification ratio of the amplifying circuit while judging whether the output of the A / D converter is not saturated or whether the gray level of the A / D converter is sufficiently present. It was very difficult to optimally adjust the amplification factor based on the absolute luminance while looking at the white display in the display screen.

Accordingly, an object of the present invention is to provide a liquid crystal display device which is easy to adjust for dispersion of voltage amplitude of an input image signal.

1 is a configuration diagram of a liquid crystal display device according to a first embodiment of the present invention.

Fig. 2 is a voltage waveform diagram of a liquid crystal display device of the first embodiment of the present invention.

Fig. 3 is a voltage waveform diagram before adjustment of the liquid crystal display device of the first embodiment of the present invention.

4 is an on-screen test pattern diagram of the liquid crystal display device of the first embodiment of the present invention.

Fig. 5 is a voltage waveform diagram at the time of optimal adjustment of the liquid crystal display device of the first embodiment of the present invention.

6 is a configuration diagram of a liquid crystal display device according to a second embodiment of the present invention.

Fig. 7 is a waveform diagram between adjustments of the liquid crystal display device of the second embodiment of the present invention.

Fig. 8 is a voltage waveform diagram at the time of optimal adjustment of the liquid crystal display device of the second embodiment of the present invention.

9 is a configuration diagram of a liquid crystal display device according to a third embodiment of the present invention.

Fig. 10 is an explanatory diagram at the time of adjustment of the liquid crystal display device of the third embodiment of the present invention.

11 is a configuration diagram of an on-screen controller of an embodiment of the present invention.

12 is a block diagram of an on-screen synthesis circuit according to an embodiment of the present invention.

Explanation of the sign

11 Clock Regeneration Circuit 12 Red Signal Processing Circuit

13 Green signal processing circuit 14 Blue signal processing circuit

15 input circuit 16 programmable amplifier circuit

17 DC Regenerative Circuit 18 A / D Converter

19 On Screen Synthesis Circuit 20 Liquid Crystal Driving Circuit

21 LCD panel 22 Remote controller

23 CPU 24 Voltage Reference Circuit

25 On Screen Controller 41 Attenuation Circuit

The above object is to display a test pattern of the maximum luminance to be compared in a part of the on-screen area when correcting the dispersion of the voltage amplitude of the input image signal, and input the test pattern and the image signal of the maximum luminance. By adjusting the operation so as to eliminate the difference from the image, it is achieved by providing a liquid crystal display device in which the operator can easily perform optimal adjustment.

According to the present invention, for example, a white (maximum luminance) input image and a white (maximum luminance) test pattern made in a liquid crystal display are arranged side by side on the screen simultaneously. The operator adjusts the amplification ratio of the amplification circuit or the reference voltage of the A / D converter so that there is no difference in luminance between the white input image and the white test pattern. The human eye is difficult to discern the absolute value of brightness, but the ability to discern a slight difference in luminance adjacent to each other is excellent. As a result, it becomes easy to adjust the liquid crystal display device so as to correct the dispersion of the voltage amplitude of the input video signal so as to achieve optimal display.

The above object is also an amplification circuit for amplifying analog video signals, an A / D converter for converting the output signal of the amplification circuit to a digital signal, and an on-screen display signal for synthesizing the output signal of the A / D converter. A liquid crystal display device having a signal processing circuit having a screen synthesis circuit and a liquid crystal panel for displaying a predetermined display in accordance with the digital output of the signal processing circuit.

The signal processing circuit generates the digital output simultaneously displaying an area corresponding to the maximum value of the analog video signal and a test pattern of the maximum gradation level on a display screen, and amplifies the amplification ratio of the amplification circuit in response to an input from an operator. And a liquid crystal display device characterized in that the output signal of the amplifying circuit corresponding to the maximum value of the analog image signal corresponds to the input voltage for the maximum gradation level of the A / D converter.

According to the present invention, when adjusting the amplification ratio of the amplification circuit, the display screen simultaneously displays the area corresponding to the maximum value of the analog image signal and the test pattern of the maximum gradation level, and the area corresponding to the maximum value of the analog image signal and the test pattern Adjust to eliminate the difference in luminance. Therefore, the operator can easily determine the amplification factor of the amplifying circuit while viewing the on-screen display, so that the input voltage of the A / D converter can be adjusted to an optimum value even when the voltage amplitude of the video signal input from the video signal generating means is dispersed. Can be.

The above object is also an amplification circuit for amplifying analog video signals, an A / D converter for converting the output signal of the amplification circuit to a digital signal, and an on-screen display signal for synthesizing the output signal of the A / D converter. A liquid crystal display device having a signal processing circuit having a screen synthesis circuit and a liquid crystal panel for displaying a predetermined display in accordance with the digital output of the signal processing circuit.

The signal processing circuit generates the digital output for simultaneously displaying a region corresponding to the maximum value of the analog video signal and a test pattern of the maximum gradation level on a display screen, and in response to an input from an operation, the A / D. And changing the reference voltage of the converter so that the input voltage corresponding to the maximum gradation level of the A / D converter corresponds to the output signal of the amplifying circuit corresponding to the maximum value of the analog video signal. Is achieved.

According to the present invention, the display screen simultaneously displays the area corresponding to the maximum value of the analog image signal and the test pattern of the maximum gradation level, and eliminates the difference between the luminance corresponding to the area corresponding to the maximum value of the analog image signal and the test pattern. Adjust the reference voltage of the converter. Therefore, the operator can easily adjust the reference static voltage of the A / D converter while viewing the on-screen display, so that the resolution of the A / D converter is full-scale even when there is a dispersion in the voltage amplitude of the voltage of the analog video signal inputted from the video signal generating means. You can do

Example

EMBODIMENT OF THE INVENTION Hereinafter, the example of embodiment of this invention is described according to drawing. However, such an embodiment does not limit the technical scope of the present invention.

1 is a configuration diagram of a liquid crystal display device according to a first embodiment of the present invention. The liquid crystal display device 100 includes a red signal processing signal 12 into which a red image signal S3 is input, a green signal processing circuit 13 into which a green and blue image signal (not shown) is input, and a blue signal, respectively. The signal processing circuit 14, the clock regeneration circuit 11 for generating the claw signal S2 from the synchronization signal S1, and the reference voltage creation circuit 24 for generating the reference voltage of the A / D converter 18; And a CPU 23 for controlling the amplification factor of the programmable amplifier circuit 16, an on-screen controller 25 for generating the on-screen display signal S15, and a liquid crystal driving circuit for generating the liquid crystal driving signal S9. And a liquid crystal display panel 21 for displaying an image. The remote controller 22 also outputs various remote control signals S10 to the CPU 23.

The red signal processing circuit 12 includes an input circuit 15 to which a red video signal S3 is input, a programmable amplification circuit 16 for amplifying the video signal S4, and a DC component to the video signal S5. On-screen which synthesizes an additional DC reproduction circuit 17, an A / D converter 18 for converting an analog video signal S6 into a digital signal, and a digital video signal S7 and an on-screen display signal S15. It has a synthesis circuit 19. The green signal processing circuit 13 and the blue signal processing 14 have the same configuration as the red signal processing circuit 12.

Next, the operation of the liquid crystal display device 100 will be described.

The red analog video signal S3 input from the video signal generating means (not shown) is input to the signal processing circuits 12, 13, and 14 for red, green, and blue, respectively, together with the green and blue video signals. In the first embodiment, the CPU 11 responds to the remote control signal S10 from the remote controller 22 to each programmable amplifier circuit of each of the processing circuits 12, 13, 14 for red, green, and blue ( 16) to a common control signal S11, and the amplification factor is adjusted in common.

Here, the voltage amplitude of the analog video signal S3 input from the video signal generating means is 0.7V. The analog video signal S4 from which the noise is removed from the input circuit 15 composed of the terminating resistor or the filter is input to the programmable amplifier circuit 16 having a variable amplification factor. The amplification factor of the programmable amplifier circuit 16 is adjusted so that the voltage amplitude of the analog video signal S5 as its output becomes the input voltage amplitude specified in the A / D converter 18.

The A / D converter 18 assumes that the lowest resolution is 1.0 V and the highest input voltage 3.0 V is the highest when the analog signal is input, i.e., 8 bits can be converted into 256 gray scale digital signals. Therefore, when the video signal S3 having a voltage amplitude of 0.7 V is input from the video signal generating means now, the amplification factor of the programmable amplifier circuit 16 is set to about 2.86 times, and the video signal inputted to the A / D converter 18 ( Adjust the voltage amplitude of S6) to 2.0V.

On the other hand, since the analog video signal S5 from the programmable amplifying circuit 16 is output by AC coupling by a capacitor, the DC level is not determined. Thus, the analog video signal S5 from the programmable amplifying circuit 16 is input to the DC reproducing circuit 17 to reproduce the DC level. The DC regeneration circuit 17 clamps the black level (lowest luminance level) of the analog video signal S5 to the black side reference voltage S13 (1.0V) generated by the reference voltage generation circuit 24. As a result, the white level (maximum luminance level) of the analog video signal S5 having a voltage amplitude of 2V becomes the same potential as the white reference voltage S14 (3.0V) of the A / D converter 18. The A / D converter 18 is supplied with a black side reference voltage S13 (1.0V) and a white side reference voltage S14 (3.0V) generated by the reference voltage generation circuit 24.

The synchronizing signal S1 input from the video signal generating means is input to the clock reproducing circuit 11 and the liquid crystal driving circuit 20, and the clock reproducing circuit 11 supplies a clock signal to be phase-synchronized with the synchronizing signal S1. S2) is generated and output to the A / D converter 18 and the like. The digital video signal S7 converted from the A / D converter 18 into a digital signal is combined with the on-screen display signal S15 input from the on-screen controller 25 in the on-screen synthesis circuit 19. The synthesized digital image signal S8 is input to the liquid crystal driving circuit 20, converted into a liquid crystal driving signal S9, and output to the liquid crystal display panel 21.

The remote controller 22 outputs the remote control signal S10 to the CPU 23 to cause the CPU 23 to perform various controls. The CPU 23 outputs the control signal S12 to the on-screen controller 25 to perform on-screen control, and control the programmable amplifier circuit 16 in response to the control signal S10 from the remote controller 22. The amplification rate of the programmable amplifier circuit 16 is controlled by outputting the signal S11.

Fig. 2 is a voltage waveform diagram in the case where the voltage amplitude of a video signal is a standard state in the liquid crystal display device of the first embodiment of the present invention. That is, the analog video signal S3 having a voltage amplitude of 0.7 V input from the video signal generating means passes through the input circuit 15 and is amplified by about 2.86 times by the programmable amplifier circuit 16, thereby providing an analog video signal having a voltage amplitude of 2.0 V. It becomes (S5). In the analog video signal S5, a DC component is added in the DC regeneration circuit 17 to form an analog video signal S6 having a voltage amplitude of 1.0 to 3.0V. Since the analog video signal S6 is input to the A / D converter 18, the digital video signal S7 is converted into a full scale digital value of OOh to FFh.

3 is a whole waveform diagram when an analog video signal S3 having an amplitude smaller than the standard value is input to the liquid crystal display device of the first embodiment of the present invention. When the voltage amplitude of the analog video signal S3 input from the video signal generating means is 0.6V, the analog output from the programmable amplifying circuit 16 is provided if the amplification ratio of the programmable amplifying circuit 16 remains about 2.86 times the standard state. The voltage amplitude of the video signal S5 is 1.72V. Accordingly, the maximum input voltage of the analog video signal S6 input to the A / D converter 18 is about 2.7 V, and this digital conversion value is DCh, and 256 gray scales of the A / D converter 18 are included. Can not save. That is, the digital conversion value DCh is D = 13, C = 12, and corresponds only to the grayscale of D × 16 + C = 220 and is narrower than 256 grayscales.

Therefore, it is necessary to adjust the amplification factor of the programmable amplifier circuit 16 to set the voltage amplitude of the video signal S5 to 2.0V. In this case, as shown in FIG. 4, in this embodiment, the display screen of the liquid crystal display panel 21 is as wide as possible by the analog video signal S3 for the maximum luminance input from the video signal generating means. The white area (maximum luminance display) is displayed in the area 32, and the test pattern 31 is displayed on-screen. A white pattern corresponding to the maximum gradation level FFh (256 gradations) of the test pattern 31 at this time is assumed.

The operator then outputs the remote control signal S10 from the remote controller 22 to the CPU 23 to adjust the amplification factor of the programmable amplifier circuit 16. When the amplification of the programmable amplifier circuit 16 is gradually raised, the difference between the luminance of the white display area 32 due to the video signal S3 input from the video signal generating means and the test pattern 31 written thereon is gradually reduced. In this state, the amplification factor is optimal.

Fig. 5 is a voltage waveform diagram when the amplification factor of the programmable amplifier circuit 16 is optimally adjusted when an analog video signal S3 having an amplitude smaller than the standard value is input. Even if the voltage amplitude of the video signal S3 entered from the video signal generating means is 0.6V, the amplification rate of the programmable amplifier circuit 16 is adjusted to about 3.33 times so that the voltage amplitude of the analog video signal S5 at its output is 2.0V. . Therefore, the maximum input voltage of the analog video signal S6 input to the A / D converter 18 is 3.0V, and can be converted into a full scale digital value from 00h to FFh.

However, if the amplification factor of the programmable amplifier circuit 16 is further increased, the analog input to the A / D converter 18 without difference in luminance between the white display area 32 and the test pattern 31 by the video signal S3 is achieved. The voltage amplitude of the video signal S6 exceeds the prescribed range. When the amplification ratio of the programmable amplification circuit 16 is raised too much, the amplification ratio is lowered once, the luminance difference between the white display area 32 and the test pattern 31 by the video signal S3 is made, and then the amplification ratio is raised again. Need to be adjusted.

Further, even when the voltage amplitude of the video signal S3 input from the video signal generating means is larger than 0.7V, the white display area 32 and the test pattern 31 by the video signal S3 are lowered once in the same manner as described above. Adjust the luminance after making the difference. In addition, the white display area 32 by the analog video signal S3 overlaps the test pattern 31 to some extent even if there is no white display on the entire surface of the liquid crystal display panel 21, so that the portion to be compared can be displayed in white. If you can.

As described above, in the embodiment of the present invention, when adjusting the amplification factor of the programmable amplifier circuit 16, on-screen display of the test pattern 31 of the maximum gradation level on the white display area 32 by the analog image signal S3 having the maximum luminance. In this case, the boundary between the white region 32 and the test pattern 31 is removed. Therefore, the operator can easily adjust the amplification factor of the programmable amplification circuit 16 while viewing the on-screen display, so that the A / D converter 18 can be adjusted even if there is a dispersion in the voltage amplitude of the video signal S3 input from the video signal generating means. The input voltage can be adjusted to the optimum value.

6 is a configuration diagram of a liquid crystal display device according to a second embodiment of the present invention. The liquid crystal display device 100 of the second embodiment has a configuration substantially the same as that of the first embodiment, but instead of the programmable amplifier circuit 16, an amplifier circuit 26 having a fixed amplification factor is provided, and the CPU 23 uses the reference voltage. The point of outputting the control signal S17 to the creation circuit 24 is different. 6 shows only the signal processing circuit 12 for red.

In the second embodiment, the analog video signal S3 is inputted from the video signal generating means by fixing the amplification factor of the amplifying circuit 26, changing the reference voltage for A / D conversion of the A / D converter 18 to be variable. Even if there is a dispersion in the voltage amplitude, the digital video signal S7 output from the A / D converter 18 is converted into a full scale digital value of 00h to FFh.

That is, the input voltage of the A / D converter 18 corresponding to the maximum digital value is made to correspond to the signal S6 corresponding to the analog video signal S3 of maximum luminance. Here, the fixed amplification factor of the amplifier circuit 26 is set to about 2.86 times as in the first embodiment.

FIG. 7 is a voltage waveform diagram before adjustment when an analog video signal S3 smaller than the standard value is input from the video signal generating means in the second embodiment. When the voltage amplitude of the analog video signal S3 input from the video signal generating means is 0.6V, the voltage amplitude of the analog video signal S5 output from the amplifying circuit 26 is 1.72V, and the A / D converter ( 18, the maximum input voltage of the analog video signal S6 input to 18 is 2.72V. If the reference voltage on the white side (maximum luminance side) of the A / D converter 18 is set to 3.0V, the maximum input voltage 2.72V of the analog video signal S6 reaches the reference voltage 3.0V on the white side. As a result, resolution of 256 gradations cannot be obtained.

In this case, the operator adjusts such that the boundary between the white display area 32 and the on-screen display test pattern 31 by the analog video signal S3 of the video signal generating means is removed, as in the first embodiment. In this embodiment, the amplification factor of the programmable amplifier circuit 16 is not adjusted, but the reference voltage on the white side of the A / D converter 18 is adjusted.

Fig. 8 is a voltage waveform diagram when the reference voltage on the white side of the A / D converter 18 is optimally adjusted in the second embodiment. The voltage amplitudes of the analog video signals S3, S5, and S6 are the same as before adjustment, but the highest reference voltage of the analog video signal S6 to which the reference voltage on the white side of the A / D converter 18 is input to the A / D converter 18. Adjusted to 2.72V same as input voltage. Therefore, the A / D converter 18 can convert from 00h to full-scale digital value of FFh even if the maximum input voltage of the analog video signal S6 is 2.72V.

As described above, in the second embodiment, the test pattern 31 of the maximum gradation level is on-screen displayed on the white display area 32 by the analog video signal S3, and the white display area 32 is operated. The reference voltage on the white side of the A / D converter 18 is adjusted to remove the boundary between the and test patterns 31. Therefore, the operator can easily adjust the reference voltage on the white side of the A / D converter 18 while viewing the on-screen display, so that even if there is a dispersion in the voltage amplitude of the analog video signal S3 input from the video signal generating means, The resolution of the / D converter 18 can be made full scale.

9 is a configuration diagram of a liquid crystal display device according to a third embodiment of the present invention. The liquid crystal display device 100 of the third embodiment has a configuration substantially the same as that of the first or second embodiment, but an attenuation circuit 41 is provided between the on-screen synthesis circuit 19 and the liquid crystal drive circuit 20. One point is different. 9, only the signal processing circuit 12 for red is shown.

When adjusting the amplification factor of the programmable amplification circuit 16 or the reference voltage on the white side of the A / D converter 18, it is easier to see the difference between the intermediate groups rather than by looking at the difference of the white display of high brightness. It is based on the easy point. As shown in Fig. 10, the brightness characteristics of the liquid crystal display panel 21 are steeper in the halftone region 43 than in the high luminance region 42, so that the change in the brightness increases with respect to the change in the driving voltage. This is because it becomes easy.

The attenuation circuit 41 attenuates the digital video signal S8 output from the on-screen synthesis circuit 19 and outputs it to the liquid crystal driving circuit 20. As a result, the difference between the luminance of the white display area 32 and the on-screen test pattern 31 due to the analog video signal S3 shown in FIG. 4 is more easily discriminated, and the amplification factor of the programmable amplifier circuit 16 or A Adjustment of the reference voltage on the white side of the / D converter 18 becomes easier.

11 is a detailed block diagram of the on-screen controller 25 according to the embodiment of the present invention. The on-screen controller 25 receives the production signal S12 output from the CPU 23 at the serial input controller 52. The control signal S12 includes a chip select signal / CS for device selection, a serial data signal SDATA as on-screen data, and a serial clock signal SCLK. The serial input controller 52 receives the serial data signal SDATA and the serial clock signal SCLK when the chip select signal / CS is at the L level. In this case, the CPU 23 transmits the serial data signal SDATA in synchronization with the serial clock signal SCLK to change the setting and the setting of the on-screen controller 25.

The font ROM 54 stores a predetermined character font, for example, 512 characters of one character composed of 12 x 18 dots.

The display VRAM 53 stores screen data constituting the on-screen, for example, data such as the position and number of characters displayed on the screen. The display VRAM 53 is set by the control signal S12 from the CPU 23.

The display control unit 51 is supplied with the horizontal synchronizing signal HSYNC, the vertical synchronizing signal VSYNC, and the clock signal CLK from the liquid crystal drive circuit 20, and reads data of the screen display from the display VRAM 53 and the font ROM 54. Thus, red, green, and blue on-screen data signals ROUT, GOUT, BOUT, and on-screen control signals VOB are output to the on-screen synthesis circuit 19.

The on-screen control signal VOB controls whether or not on-screen display is performed by the on-screen synthesis circuit 19. That is, the on-screen display is performed when the on-screen control signal VOB is at the H level, and the on-screen display is not performed when the on-screen control signal VOB is at the L level.

Fig. 12 is a specific configuration diagram of the on-screen synthesis circuit 19 for red in the present embodiment. The on-screen data signal ROUT is combined with the digital video signal S7 input from the A / D converter 18 by the multiplexer 61. In this case, when the on-screen control signal VOB is at the H level, the on-screen synthesis circuit 19 synthesizes and outputs the on-screen data signal ROUT to the digital video signal S7, and when the on-screen control signal VOB is at the L level. Outputs only the digital video signal S7.

FIG. 13 is a configuration diagram of an on-screen synthesis circuit 19 used in the liquid crystal display device of the fourth embodiment. In the fourth embodiment, NAND circuits 62, 64, and 66 are provided on the output side of the on-screen synthesis circuits 19 for red, green, and blue. Other configurations of the fourth embodiment are the same as those of the first to third embodiments.

In the first to third embodiments, the amplification factor of the programmable amplifier circuit 16 or the reference voltage on the white side of the A / D converter 18 is determined by the signal processing circuits 12, 13, and 14 for red, green, and blue. Although adjustments are made in common in, the signal processing circuits 12, 13, and 14 for red, green, and blue need to be adjusted individually in order to make more precise adjustments.

In the fourth embodiment, similarly to the first to third embodiments, the analog video signal S3 displaying white color is input from the video signal generating means in a predetermined range of the liquid crystal display panel 21. When the red adjustment is performed, the on-screen display is performed with the on-screen control signal VOB at the H level, and the green digital video signal S7 is set with the green mask signal GEN and the blue mask signal BEN at the L level. (G) and the blue digital video signal S7 (B) are forcibly switched to the lowest level. As a result, only the red image is displayed on the liquid crystal display panel 21. Similarly to the above-described adjustment, adjustment is made such that the boundary between the display by the red digital video signal S7 (R) and the display of the red test pattern 31 of maximum gradation is removed. When adjusting the green, red and blue digital video signals S7 (R) and S7 (B) are set to the lowest level. When adjusting the blue, the red and green digital video signals S7 (R) are adjusted. Adjust S7 (G) to the lowest level.

As described above, in the fourth embodiment, red, green, and blue signals are displayed by the analog video signal S3, and the red, green, and blue test patterns 31 of the maximum gradation level are displayed on-screen, and the boundary is removed. So that it is adjusted. Therefore, the operator can easily adjust the amplification factor of the programmable amplifier circuit 16 or the reference voltage of the A / D converter 18 while viewing the on-screen display, so that the red, green, and blue analog video inputted from the video signal generating means can be adjusted. Even if there is dispersion in the voltage amplitude of the signal, the input voltage of the A / D converter 18 for red, green, and blue can be adjusted to an optimum value.

As described above, according to the present invention, the test pattern by the digital image signal of the maximum gradation to be compared with the display area by the input image signal of maximum luminance is displayed in a part of the on-screen, and the test pattern Since the amplification factor of the amplification circuit or the reference voltage of the A / D converter is adjusted so as to eliminate the boundary of the display area by the input video signal, the adjustment of the dispersion of the voltage amplitude of the input video signal becomes easy.

Claims (5)

An amplification circuit for amplifying an analog image signal, an A / D converter for converting the output signal of the amplification circuit into a digital signal, and an on-screen synthesis circuit for synthesizing the output signal of the A / D converter and an on-screen display signal; A liquid crystal display device having a signal processing circuit and a liquid crystal panel which displays a predetermined display in accordance with a digital output of the signal processing circuit. The signal processing circuit generates the digital output simultaneously displaying an area corresponding to the maximum value of the analog video signal and a test pattern of the maximum gradation level on a display screen, and adjusts the amplification factor of the amplification circuit in response to an input from an operator. And changing the output signal of the amplifying circuit corresponding to the maximum value of the analog video signal to the input voltage of the maximum gradation level of the A / D converter. An amplification circuit for amplifying an analog video signal, an A / D converter for converting the output signal of the amplification circuit into a digital signal, and an on-screen synthesis circuit for synthesizing the output signal of the A / D converter and an on-screen display signal; A liquid crystal display device having a signal processing circuit and a liquid crystal panel which displays a predetermined display in accordance with a digital output of the signal processing circuit. The signal processing circuit generates the digital output for simultaneously displaying an area corresponding to the maximum value of the analog video signal and a test pattern of the maximum gradation level on a display screen, and in response to an input from an operator, And varying a reference voltage so that an input voltage for the maximum gradation level of the A / D converter corresponds to an output signal of the amplifying circuit corresponding to the maximum value of the analog video signal. The method according to claim 1 or 2, And the signal processing circuit further comprises an attenuation circuit for attenuating the output signal of the on-screen synthesis circuit. The method of claim 1, The signal processing circuit generates the digital output for simultaneously displaying an area corresponding to the maximum value of the analog video signal of red, green or blue, and a test pattern of the maximum gradation level of red, green or blue on the display screen, and an operator. Varying the amplification factor of the amplification circuit in response to an input from the amplification circuit, and outputting the output signal of the amplifying circuit corresponding to the maximum value of the analog video signal of red, green or blue to the maximum of red, green or blue of the A / D converter. And an input voltage corresponding to the gradation level. The method of claim 2, The signal processing circuit generates the digital output simultaneously displaying a region corresponding to the maximum value of the analog image signal of red, green or blue, and a test pattern of the maximum gradation level of red, green or blue on the display screen; In response to an input from an operator, the reference voltage of the A / D converter is changed so that the input voltage for the red, green, or blue maximum gradation level of the A / D converter is changed to that of the analog video signal of red, green, or blue. And an output signal of the amplifying circuit corresponding to the maximum value.