JPH11133908A - Optimal contrast adjustment device for display panel - Google Patents

Abstract

(57) [Summary] [Problem] Contrast adjustment can be performed quickly and uniformly.
Provided is an optimal contrast adjusting device that can contribute to cost reduction of a display panel. SOLUTION: The display area of the STN liquid crystal panel 1 is divided into upper and lower parts, and the highest luminance data is displayed in an upper display area, and at the same time, the lowest luminance data is displayed in a lower display area. The transmitted light from the highest luminance display area is detected by the optical sensor 2 and the transmitted light from the lowest luminance display area is detected by the optical sensor 3. The division processing unit 4-2 performs a division process using the output of the optical sensor 2 as a denominator and the output of the optical sensor 3 as a numerator. The divided calculation power is monitored by a voltmeter, and its output has a certain relationship with the contrast ratio of the STN liquid crystal panel 1. If the variable resistor provided on the STN liquid crystal panel 1 is rotated clockwise or counterclockwise, the contrast can be adjusted to an optimum state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optimum contrast adjusting device for a display panel used for adjusting the contrast of various display panels such as an STN liquid crystal panel, a plasma display panel, and an EL display panel at the time of shipping. .

[0002]

2. Description of the Related Art As an example of this type of display panel, there is an STN liquid crystal panel to which a DC voltage is applied from the outside. This STN liquid crystal panel is shipped after adjusting the contrast.

[0003] As a conventional example of a method of adjusting the contrast of an STN liquid crystal panel, there is a method of visually adjusting the contrast. FIG. 12 shows this contrast adjustment method, in which a proper display content is displayed on the STN liquid crystal panel 100 in a state where a predetermined contrast adjustment voltage (hereinafter, referred to as Vcon voltage) is applied from the outside of the STN liquid crystal panel 100. Then, the adjuster visually observes the display state and adjusts an AC conversion circuit in a liquid crystal control circuit (not shown) in order to adjust the optimum contrast.

FIG. 1A shows an STN liquid crystal panel 1.
For example, at the center of the display area of 00, 0, 1, 2, 1
FIG. 3B shows a case where the gray scale data of 3, 14, and 15 are partially displayed. FIG.
16 is displayed.

As another conventional example, there is a method shown in FIG. The entire display area of the STN liquid crystal panel 100 is displayed with the highest luminance data (R, G, and B constituting one pixel are all at “H” level = full screen white) (FIG. 10A).
Then, the entire display area is displayed with the lowest luminance data (R, G, and B are all “L” level = full screen black) (see FIG. 13B). Then, the display screen in each display state is imaged by the imaging device 101, and the output is given to the luminance meter 102, whereby the luminance in each display state is measured.

Next, the following equation (1) is calculated using the luminance data measured in the two display states, and the AC conversion circuit is adjusted so that the contrast becomes maximum (optimum).

Contrast ratio (Co) = maximum luminance / minimum luminance (1)

[0008]

However, FIG.
Both of the methods shown in (a) and (b) have a problem that contrast adjustment is apt to vary due to differences in individual senses, differences in skill levels, and the like, because the adjustments are made by the eyes of the adjuster. In addition, since the STN liquid crystal panel 100 has a narrow viewing angle, the adjuster must be located in front of the STN liquid crystal panel 100, and the operator is forced to take a cramped posture.

In the conventional example shown in FIG. 13, the contrast is adjusted semi-automatically, so that the variation in the adjustment can be reduced. However, the highest luminance state and the lowest luminance state are displayed alternately, and each state is displayed. , It is necessary to measure the luminance, so that the man-hour required for the adjustment increases. For this reason, there is a problem that productivity is poor and the cost of the STN liquid crystal panel 100 is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is possible to adjust the contrast quickly and uniformly, thereby contributing to the cost reduction of a display panel such as an STN liquid crystal panel. An object is to provide an optimum contrast adjusting device.

[0011]

An optimum contrast adjusting device for a display panel according to the present invention is an optimum contrast adjusting device for a display panel used for adjusting the contrast of a display panel to an optimum state at the time of shipping or the like.
Screen dividing means for dividing the display area of the display panel into at least two or more display areas; displaying display data that gives the highest luminance to at least one of the divided display areas; Display control means for displaying display data giving at least one of the lowest luminances, a first optical sensor arranged in association with a display area for displaying the highest luminance data, and a display area for displaying the lowest luminance data A second optical sensor disposed in association with the first optical sensor, and an output of the second optical sensor as a numerator,
And a division unit that performs a division process using the output of the optical sensor as a denominator, and operates the contrast adjustment unit provided on the display panel based on the output of the division unit to adjust the brightness of the display panel. Thus, the above object is achieved.

Preferably, there is provided a monitor for monitoring the output of the divider, wherein the contrast of the display panel is adjusted by operating the contrast adjuster manually or automatically so that the output becomes substantially the minimum value. And

[0013] Preferably, the apparatus further comprises an operation result output unit to which an output of the division means is provided, and the operation result output unit outputs a display material to a Vcon signal among display data and control signals sent to the display panel. A signal obtained by superimposing a sine wave signal having a frequency equal to or lower than the response speed as a reference wave as a reference wave is transmitted to the display panel, and the output of the dividing means is synchronously detected in synchronization with the reference wave.

[0014] Preferably, the optical sensor has a filter having a spectral sensitivity characteristic corresponding to human visibility.

Preferably, the display panel is ST.
N liquid crystal panel.

The operation of the present invention will be described below.

According to the present invention, a display area of a display panel is divided into at least two or more display areas, at least one of the divided display areas is displayed with display data giving the highest luminance, and at the same time, the remaining data is displayed. In the above-described conventional example, the display data that gives the lowest brightness is displayed on at least one of the display areas of the display area, and the highest brightness data and the lowest brightness data are alternately displayed, and the brightness in each display state is measured. In comparison, the man-hour required for the contrast adjustment can be reduced. Accordingly, the productivity of the display panel can be improved correspondingly, which can contribute to the cost reduction of the display panel.

In addition, in the present invention, a division process is performed using the output of the second optical sensor for measuring the lowest luminance data as a numerator and the output of the first optical sensor for measuring the highest luminance data as a denominator. , The division value, that is, the contrast ratio, as shown in FIG. 4 described later, the maximum point (optimum point) coincides with the minimum point of the output voltage of the optimal contrast adjustment device.

Therefore, for example, when manually adjusting the contrast adjusting means having a variable resistor, the adjuster visually checks the voltage of the monitor means (for example, a voltmeter) without measuring the actual contrast ratio. However, by operating the variable resistor so that the output voltage value is minimized, the optimum contrast of the display panel can be adjusted.

As a result, unlike the conventional visual method, there is little variation in adjustment, and uniform contrast adjustment can be performed.

According to a configuration in which a motor control circuit is used as the monitor means and the motor control circuit drives the contrast adjustment means via the motor in accordance with the amount of adjustment based on the output voltage from the optimum contrast adjustment device, Since the contrast adjustment of the display panel can be automatically performed, it is possible to more quickly perform the uniform contrast adjustment with less variation in the adjustment.

In addition, according to the present invention, the output of the division means, that is, the division result is always 1 or less. For this reason, when performing division processing by performing analog processing on the output of the optical sensor, output saturation can be prevented. In the case of performing digital processing, overflow can be prevented.

The display device further includes an operation result output section to which an output of the dividing means is provided, and the operation result output section includes Vcon among the display data and the control signal transmitted to the display panel.
According to a configuration in which a signal in which a sine wave signal having a frequency equal to or lower than the frequency corresponding to the response speed of the display material is superimposed on the signal as a reference wave is sent to the display panel, and the output of the dividing means is synchronously detected in synchronization with the reference wave, the variable resistor It is possible to obtain a voltage output (see FIG. 7) substantially proportional to the adjustment amount of the vessel. Therefore, the contrast can be more easily and accurately adjusted.

Further, according to the configuration in which a filter having a spectral sensitivity characteristic corresponding to the human visual sensitivity is used as the optical sensor, the filter cuts out the light in the infrared and ultraviolet regions. Can be blocked. As a result, more accurate optimal contrast adjustment becomes possible.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optimum contrast adjusting device for a display panel according to the present invention will be specifically described below with reference to the drawings.

(Embodiment 1) FIGS. 1 to 4 show Embodiment 1 of an optimum contrast adjusting device for a display panel according to the present invention. As shown in FIG. 1, the optimal contrast adjusting device according to the first embodiment divides the display area of the STN liquid crystal panel 1 into upper and lower parts, and stores the highest luminance data in the upper display area (hereinafter referred to as the highest luminance display area). (R, G, and B constituting one pixel are all at “H” level).
At the same time, the lowest luminance data (R, G,
B is displayed at “L” level).

The display driving is performed by a digital interface (not shown) provided on the side of the STN liquid crystal panel 1 and the contrast adjusting device 4, and the liquid crystal display data, the control signal and the Vcon are transmitted to the STN liquid crystal panel 1 by the STN.
This is performed in cooperation with the sending unit 4-4 that sends out to the liquid crystal panel 1.

The light transmitted from the highest luminance display area is detected as the highest luminance data by the optical sensor 2 (PD1) composed of a photodiode, and the transmitted light from the lowest luminance display area is detected by the optical sensor 3 (PD) composed of a photodiode.
In 2), it is detected as the lowest luminance data.

Here, the optical sensors 2 and 3 in the illustrated example are removably mounted at positions near the left end on the front surface of each display area. More specifically, it is adhered to the panel surface of the STN liquid crystal panel 1 in order to receive only transmitted light from the STN liquid crystal panel 1 and prevent adverse effects from disturbance light such as indoor lighting. In addition, this effect is obtained by the optical sensor 2,
It can also be achieved by mounting a hood in front of 3.

The optical sensors 2 and 3 are provided with a filter (not shown) having a spectral sensitivity characteristic shown in FIG. 3, and the filter cuts light in the infrared and ultraviolet regions. That is, light of a wavelength outside the human visual range is blocked, thereby enabling more accurate optimal contrast adjustment.

In addition, a contrast adjustment unit 1-1 having a variable resistor is provided at an internal position in the upper right end of the STN liquid crystal panel 1. This contrast adjusting section 1-1 is specifically provided in a liquid crystal control circuit section (not shown). When the variable resistor is rotated clockwise or counterclockwise, the contrast of the STN liquid crystal panel 1 is increased. Can be adjusted.

The luminance data detected by the optical sensors 2 and 3 is input to the optimum contrast adjusting device 4. As shown in FIG. 1, the optimal contrast adjustment device 4 is
-4, optical sensor input unit 4-1 and division processing unit 4-2
And a calculation result output unit 4-3 and a power supply unit 4-5.

FIG. 2 shows the details of the division processing unit 4-2. The division processing unit 4-2 uses the output of the optical sensor 2 for detecting the maximum luminance data as the denominator and detects the minimum luminance data. A division process is performed using the output of the light sensor 3 as a numerator. That is, the reciprocal of the contrast ratio represented by the above equation (1) is calculated.

This operation, together with the configuration of the optimum contrast adjusting device 4, will now be described more specifically. As shown in FIG. 2, the optical sensor input unit 4-1 includes an I / V conversion circuit (current / current
A voltage conversion circuit) 4-1 (X section) and 4-1 (Y section), and one of the I / V circuits 4-1 receives the detected luminance data of the optical sensor 2 and the other I / V circuit 4-1. The / V circuit 4-1 receives the detected luminance data of the optical sensor 3.

The voltage signals converted by the I / V conversion circuits 4-1 and 4-1 are provided to a division processing unit 4-2, where the above-described division processing is performed. The result of the division, that is, the contrast ratio obtained by this division processing, is output from the operation result output unit 4-3 to a voltmeter (not shown) serving as monitoring means.

FIG. 4 shows the relationship between the output voltage value V of the voltmeter and the contrast ratio. As can be seen from FIG. 4, when the output voltage value of the voltmeter becomes the lowest level, the contrast ratio becomes the optimum level. . Therefore, the output voltage value V of the voltmeter
When the adjuster rotates the variable resistor of the contrast adjustment section 1-1 clockwise or counterclockwise so that the minimum level is obtained, the contrast ratio of the STN liquid crystal panel 1, that is, the brightness is adjusted to the optimum contrast. become.

Unlike the above-described conventional visual inspection, the optimal contrast adjusting device of the first embodiment automatically adjusts the contrast of the STN liquid crystal panel 1 when the adjuster operates the variable resistor. It can be said that this is a semi-automatic type optimal contrast adjustment device. Therefore, there is little variation in adjustment, and uniform contrast adjustment can be performed.

Further, as compared with the above-described conventional example in which the highest luminance data and the lowest luminance data are alternately displayed, the display time can be reduced, and the contrast ratio does not need to be actually measured. Since the reduction can be achieved, there is an advantage that the productivity of the display panel can be improved and the cost of the display panel can be reduced.

In addition, assuming that the output of the optical sensor 2 provided in the highest brightness data display area is X and the output of the optical sensor 3 provided in the lowest brightness data display area is Y, X and Y are expressed by the following formula (2). Satisfies the conditions.

X ≧ Y> 0 (2) Here, in the first embodiment, X is a denominator input, and Y is a numerator input. Therefore, the division result Y / X is always 1 or less.

Therefore, when the division processing is performed by performing analog processing on the outputs of the optical sensors 2 and 3, output saturation can be prevented. When performing digital processing,
Overflow can be prevented.

For this reason, according to the optimal contrast adjusting device of the first embodiment, there is an advantage that the stability and reliability of the optimal contrast adjusting device can be improved in any case.

(Embodiment 2) FIG. 5 shows Embodiment 2 of the optimum contrast adjusting apparatus of the present invention. The optimal contrast adjusting device according to the second embodiment has a configuration in which the display area of the STN liquid crystal panel 1 is divided into four parts vertically and horizontally, and the maximum luminance data and the minimum luminance data are simultaneously displayed in each divided display area.

That is, as shown in FIG. 5, of the four divided display areas, the highest luminance data is displayed in the upper left and lower right display areas, and the lowest luminance data is simultaneously displayed in the lower left and upper right display areas. It has a configuration.

In each of the divided display areas, the first embodiment
Similar optical sensors 2-1, 2-2, 3-1 and 3-2 are detachably attached.
And a half of the total output value of the optical sensor 2-2 as the detected luminance data, via the X section of the optical sensor input section 4-1 of the optimal contrast adjusting device 4 shown in FIG.
-2. Similarly, a half value of the total output value of the optical sensor 3-1 and the optical sensor 3-2 is set as the detected luminance data as the optical sensor input unit 4 of the optimal contrast adjusting device 4.
It is given to the division processing unit 4-2 via the Y part of -1.

The other configuration is the same as that of the first embodiment, and the description is omitted here.

The same effect as in the first embodiment can be obtained by the optimum contrast adjusting device of the second embodiment. In addition, in the optimal contrast adjustment device of the second embodiment, luminance data from two different display areas are
In other words, the average and the numerator output and denominator output are used.
There is an advantage that a more realistic contrast adjustment can be performed.

(Embodiment 3) FIGS. 6 to 10 show Embodiment 3 of the optimum contrast adjusting apparatus of the present invention. The optimal contrast adjusting device according to the third embodiment uses the transmission unit 4 so that the contrast of the STN liquid crystal panel 1 can be more easily adjusted from the output characteristics of the division processing unit 4-2 shown in FIG.
-4 from the liquid crystal display data and control signals sent to the STN liquid crystal panel 1, a sine wave signal having a frequency equal to or lower than the frequency corresponding to the response speed of the liquid crystal is superimposed on the Vcon signal (usually a predetermined DC voltage signal) as a reference wave. A signal is sent to the STN liquid crystal panel 1, and the output of the division processing of the optimum contrast adjusting device is detected in synchronization with the reference wave.

FIG. 6 shows a circuit configuration for performing synchronous detection. The detection circuit includes a switch 10 to which a division signal from the division processing unit 4-2 shown in FIG. 1 is supplied, a waveform shaping circuit 11 for shaping a waveform of a reference wave, and low-pass filters 12-1 and 12-1.
2-2 and the differential amplifier 13 and are provided in the division result output unit 4-3 in FIG.

According to the configuration in which this detection circuit is provided, FIG.
The voltage output (see FIG. 7) substantially proportional to the adjustment amount of the variable resistor of the contrast adjustment unit 1-1 shown in FIG. The reason will be described below with reference to FIGS.

FIG. 8 shows output characteristics of the division processing unit 4-3 corresponding to the adjustment amount of the variable resistor. A, B, and C in the figure show the cases where the adjustment is excessive, the optimal adjustment, and the adjustment is insufficient. FIG. 9 shows excessive adjustment (see FIG. 9A), optimal adjustment (see FIG. 9B), and insufficient adjustment (see FIG. 9C).
Are plotted with respect to the phase angle of the reference wave in each state.

The output of the division processing unit 4-3 switches the position of the switch 10 to the low-pass filter 12-1 while the phase angle of the reference wave is 0 to 180 ° (π) (during the “H” level). When the phase angle of the reference wave is 180 to 360 ° (2π) (during the “L” level), the position of the switch 10 is switched to the low-pass filter 12-2.

At this time, each low-pass filter 12-
When the outputs of 1 and 12-2 are differentially amplified by the differential amplifier 13, a positive voltage is generated if A is excessively adjusted (FIG. 9A).
In the optimal adjustment state of B, a zero potential (see FIG. 9B) is generated, and in the under-adjustment state of C, a negative voltage is generated (see FIG. 9C).

Here, the differentially amplified output V is measured by a voltmeter, which is a monitoring means, as in the first embodiment. Therefore, according to the third embodiment, the direction in which the contrast adjustment is performed, that is, the rotation direction of the variable resistor can be easily determined. That is, if the output V is positive, the variable resistor is rotated, for example, counterclockwise, and stops at the position where the potential becomes zero. On the other hand, if the output V is negative, the variable resistor is rotated clockwise, and similarly stopped at zero potential, so that the contrast can be optimally adjusted.

Next, the flow of the optimal contrast adjustment in the optimal contrast adjusting device of the third embodiment will be described with reference to FIG. First, the adjuster visually checks the output voltage value V of the voltmeter and determines whether the output voltage value V is within (0 ± Xm) V (step S1). Where ± Xm
Is a voltage value corresponding to an allowable range of the optimal contrast adjustment.

Next, the adjuster determines whether or not the output voltage value V is a positive value (step S2), and confirms that the output voltage value V is a positive value. The resistor is rotated in the counterclockwise direction (the direction of decreasing the voltage value) to adjust the contrast (step S3). Subsequently, the output voltage value V of the voltmeter after the adjustment is visually observed to determine whether or not the output voltage value V is within (0 ± Xm) V. When it is confirmed that this condition is satisfied, the contrast adjustment is performed at that time. End the processing for. In step S1,
When the output voltage value V before the adjustment satisfies the above condition, the contrast adjustment work is unnecessary.

On the other hand, if it is determined in step S2 that the output voltage value V is a negative value, the adjuster rotates the variable resistor clockwise (in the direction of increasing the voltage value) to adjust the contrast (step S4). ). Hereinafter, similarly, step S
In step 1, the output voltage value V of the voltmeter after the adjustment is visually observed to determine whether or not the output voltage value V is within (0 ± Xm) V. When it is confirmed that this condition is satisfied, the contrast adjustment is performed at that time. The processing for this is ended.

When the contrast adjustment operation is completed, the optical sensors 2 and 3 are removed from the STN liquid crystal panel 1 and attached to the display area of the next STN liquid crystal panel 1 to be inspected.

According to the optimum contrast adjusting device of the third embodiment, there is an advantage that the contrast of the STN liquid crystal panel 1 can be adjusted more easily and accurately.

(Embodiment 4) FIG. 11 shows Embodiment 4 of the optimum contrast adjusting device of the present invention. The optimal contrast adjustment device according to the fourth embodiment includes the calculation result output unit 4-3.
Is input to a motor control circuit 20, which is a drive control circuit for the DC motor 21, thereby controlling the direction and amount of rotation of the DC motor 21 in accordance with the sign of the output V and its value. Contrast adjusting means 23 such as a key connected to a speed reducer 22 connected to an output shaft 21
The contrast of the STN liquid crystal panel 1 is automatically adjusted by rotating the adjustment unit 24, that is, the variable resistor in the clockwise or counterclockwise direction by a predetermined amount.

The driving conditions of the DC motor are the same as those shown in FIG.

According to the fourth embodiment, since the contrast adjustment of the STN liquid crystal panel 1 can be performed fully automatically without the intervention of an adjuster, there is an advantage that a uniform adjustment of the contrast with little variation in the adjustment can be performed in a shorter time. There is.

(Other Embodiments) Embodiments 1 to
In the fourth embodiment, the case where the present invention is applied to the contrast adjustment of the STN liquid crystal panel has been described. However, the present invention can be similarly applied to the contrast adjustment of other display panels such as a plasma display panel and an EL display panel. Of course. Also, in the first embodiment, the case where the present invention is applied to the contrast adjustment of the transmission type STN liquid crystal panel has been described. However, the reflection type STN liquid crystal panel can be similarly formed by devising the mounting position of the optical sensor and the like. Can be applied to

[0064]

As described above, the optimum contrast adjusting device for a display panel according to the present invention divides the display area of the display panel into at least two or more display areas and gives the maximum brightness to at least one of the divided display areas. Since the display data is displayed, and at the same time, the display data giving the lowest brightness is displayed in at least one of the remaining display areas, the highest brightness data and the lowest brightness data are alternately displayed, and The number of steps required for contrast adjustment can be reduced as compared with the above-described conventional example in which luminance in a display state is measured. Accordingly, the productivity of the display panel can be improved correspondingly, which can contribute to the cost reduction of the display panel.

In addition, in the present invention, a division process is performed using the output of the second optical sensor for measuring the lowest luminance data as a numerator and the output of the first optical sensor for measuring the highest luminance data as a denominator. , The division processing value, that is, the contrast ratio is the same as the maximum point (optimum point) and the minimum point of the output voltage of the optimal contrast adjustment device.

Therefore, for example, when manually adjusting the contrast adjusting means having a variable resistor, the adjuster visually checks the voltage of the monitor means (for example, a voltmeter) without measuring the actual contrast ratio. However, by operating the variable resistor so that the output voltage value is minimized, the optimum contrast of the display panel can be adjusted.

As a result, unlike the conventional visual method, there is little variation in adjustment, and uniform contrast adjustment becomes possible.

In addition, according to the display panel optimum contrast adjusting apparatus of the present invention, the output of the dividing means, that is, the division result is always 1 or less. For this reason, when performing division processing by performing analog processing on the output of the optical sensor, output saturation can be prevented. In the case of performing digital processing, overflow can be prevented.

According to a third aspect of the present invention, there is provided a display panel optimum contrast adjusting device, further comprising an operation result output unit to which an output of the dividing means is provided, wherein the operation result output unit is configured to output the display data transmitted to the display panel. And among the control signals, a signal obtained by superimposing a sine wave signal having a frequency equal to or lower than the frequency corresponding to the response speed of the display material on the Vcon signal as a reference wave is sent to the display panel, and the output of the dividing means is synchronously detected in synchronization with the reference wave. With this configuration, it is possible to obtain a voltage output that is substantially proportional to the adjustment amount of the variable resistor, which is the contrast adjustment means. Therefore, the contrast can be more easily and accurately adjusted.

Further, in particular, according to the optimum contrast adjusting device for a display panel according to the fourth aspect, since the optical sensor has a configuration using a filter having a spectral sensitivity characteristic corresponding to the human visual sensitivity, the configuration is adopted. Since the filter cuts light in the infrared and ultraviolet regions, it is possible to block light having a wavelength outside human vision. As a result, more accurate optimal contrast adjustment becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing Embodiment 1 of an optimal contrast adjusting device for a display panel.

FIG. 2 is a block diagram illustrating details of a division processing unit and peripheral circuits of the division processing unit of the optimal contrast adjustment device according to the first embodiment.

FIG. 3 is a graph showing spectral sensitivity characteristics of a filter attached to an optical sensor.

FIG. 4 is a graph showing a relationship between an output of a calculation result output unit and a contrast ratio.

FIG. 5 is a schematic diagram showing a second embodiment of the optimum contrast adjusting device.

FIG. 6 is a block diagram illustrating a detection circuit provided in an operation result output unit of the optimal contrast adjustment device according to the third embodiment.

FIG. 7 is a graph showing the relationship between the output of the calculation result output unit and the adjustment amount of the contrast adjustment unit in the optimal contrast adjustment device according to the third embodiment.

FIG. 8 is a graph illustrating a relationship between an output of a division processing unit and an adjustment amount of the contrast adjustment unit in the optimal contrast adjustment device according to the third embodiment.

9A and 9B are graphs showing a relationship between a phase angle of a reference wave and a voltage, wherein FIG. 9A shows excessive adjustment, FIG. 9B shows optimum adjustment, and FIG. 9C shows insufficient adjustment.

FIG. 10 is a flowchart showing the flow of contrast adjustment by the optimum contrast adjustment device according to the third embodiment.

FIG. 11 is a block diagram illustrating an optimal contrast adjustment device according to a fourth embodiment.

FIGS. 12A and 12B are diagrams showing a conventional visual contrast adjustment method.

13A and 13B are diagrams showing another conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 STN liquid crystal panel 1-1 Contrast adjustment part 2, 2-1, 2-2, 3-1 and 3-2 Optical sensor 4 Optimal contrast adjustment device 4-1 Optical sensor input part 4-2 Division processing part 4-3 Calculation result output unit 4-4 Sending unit 4-5 Power supply unit 10 Switch 11 Waveform shaping circuit 12-1, 12-2 Low-pass filter 13 Differential amplifier 20 Motor control circuit 21 DC motor 22 Reduction gear 23 Contrast adjustment means 24 Adjustment unit (Variable resistor)

Claims (5)

[Claims] 1. An optimal contrast adjusting device for a display panel used for adjusting a contrast of a display panel to an optimal state at the time of shipping or the like, wherein a display area of the display panel is divided into at least two or more display areas. Screen dividing means, and display control means for causing at least one of the divided display areas to display display data giving the highest luminance and simultaneously displaying at least one of the remaining display areas display data giving the lowest luminance. A first optical sensor disposed in association with a display area for displaying the highest luminance data; a second optical sensor disposed in association with a display area for displaying the lowest luminance data; Division means for performing a division process using an output of the second optical sensor as a numerator and an output of the first optical sensor as a denominator,
An optimum contrast adjusting device for a display panel, wherein the contrast adjusting means provided on the display panel is operated based on the output of the dividing means to adjust the brightness of the display panel. 2. The apparatus according to claim 1, further comprising monitor means for monitoring the output of said division means, wherein said contrast adjustment means is manually or automatically operated to adjust the contrast of the display panel so that the output becomes substantially the minimum value. 2. The optimal contrast adjusting device for a display panel according to 1. 3. An operation result output unit to which an output of the division means is provided, wherein the operation result output unit includes V of the display data and control signal transmitted to the display panel.
2. A signal in which a sine wave signal having a frequency equal to or lower than the frequency corresponding to the response speed of the display material is superimposed on the con signal as a reference wave, the signal is transmitted to the display panel, and the output of the division means is synchronously detected in synchronization with the reference wave. Or an optimal contrast adjusting device for a display panel according to claim 2. 4. The optimal contrast adjusting device for a display panel according to claim 1, wherein said optical sensor has a filter having a spectral sensitivity characteristic corresponding to human visual sensitivity. 5. The optimal contrast adjusting device for a display panel according to claim 1, wherein said display panel is an STN liquid crystal panel.