JP2003140631A - Brightness control system for display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adjust brightness of a display device correspondingly to predetermined degrees of ambient brightness by using a photo-sensor having an arbitrary characteristic. SOLUTION: In a display device wherein the brightness control system for the disclosed display device is provided with a illuminance threshold value table storing a plurality of threshold values about the output voltage values of the photo-sensor for measuring illuminance of a light receiving part, and the brightness of the screen is sequentially changed over according to a plurality of modes corresponding to predetermined degrees of the ambient brightness, it is possible to change over the brightness according to a plurality of modes by using the photo-sensor having an arbitrary characteristic, by using an illuminance threshold value table 12 where each threshold value in the illuminance threshold value table 11 corresponding to a photo-sensor having a standard characteristic is rewritten by an output voltage corresponding to each threshold value by a photo-sensor having an arbitrary characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brightness control method for a display device for adjusting brightness of a display surface corresponding to a predetermined level of ambient brightness by using an optical sensor having arbitrary characteristics. Regarding

[0002]

2. Description of the Related Art In a portable device having a display device for visually displaying characters, graphics, etc., such as a mobile phone device,
The illuminance of external light applied to the display surface is measured at regular intervals, and the brightness of the display surface is adjusted according to the result to make the display easier to see and to improve the appearance. At this time, the display device is a liquid crystal display (Li
In the case of having a quid crystal display (LCD), the brightness adjustment is performed by adjusting the luminous intensity of a backlight provided on the back surface of the liquid crystal panel. Also, TF
In the case of a T (Thin Film Transistor) panel, the brightness is adjusted by adjusting the luminosity of the front light.
In the case of an L (Electric Luminescence) panel, this is performed by adjusting the brightness of self-luminous emission.

Conventionally, in such a portable telephone device, as a method of adjusting the brightness of the display surface when the illuminance due to external light changes, the brightness of the display surface, for example, when the illuminance of the display surface is 0 to 100 lx. Darken, 100-3000l
A method is adopted in which a normal state is set for x and a bright state is set for 3000 lx or more.

FIG. 5 is a block diagram showing the structure of a conventional portable telephone device to which the present invention is applied. As shown in FIG. 5, the mobile phone device 1 has a central processing unit (Central Pr
ocessing Unit: CPU 2 and FROM (Flash Read
Only Memory) 3 and SRAM (Static Random Access)
Memory) 4, optical sensor 5, analog / digital (A / D) conversion circuit 6, LCD 7, backlight 8
And an external input / output circuit (external I / O) 9.

The CPU 2 performs all control and judgment processing such as a call, standby, LCD display, etc. performed by the portable telephone device 1 based on a program. FROM3 is an external I
/ O9, a fixed storage device that can be electrically read and written from the CPU 2, a brightness threshold value table for setting the luminous intensity of the backlight 8 according to the illuminance based on external light, and a call of the mobile phone device 1. , A program for performing standby, lighting control of the backlight 8, and the like are stored. The SRAM 4 is a temporary storage device that does not require refreshing and serves as a work area for storing the calculation result of the CPU 2 and the like. The optical sensor 5 detects external light received by the mobile phone device 1 and generates an output voltage (analog value) according to the illuminance. The A / D conversion circuit 6 includes the optical sensor 5
The output voltage of is converted into a digital value. The LCD 7 visually displays information such as the destination telephone number and communication date and time in the mobile phone device 1. The backlight 8 illuminates the liquid crystal panel of the LCD 7 from the back side to brighten the display surface.
The external I / O 9 is an external personal computer (not shown) and a CPU
It becomes an interface for inputting / outputting information between the two.

The operation of changing the brightness of the display surface of the LCD 7 in the portable telephone device 1 according to the ambient brightness will be described below with reference to FIG. LCD7
The display surface of is made up of a liquid crystal panel, and the display surface is made bright by transmitting light from a backlight 8 provided on the back surface of the liquid crystal panel without emitting light by itself. Therefore, by changing the light intensity of the backlight 8 according to the ambient brightness,
It is necessary to maintain the brightness of the display surface in an appropriate state regardless of the ambient light and darkness. Therefore, an optical sensor 5 is provided to measure the illuminance based on external light at an appropriate location on the mobile phone device 1. Then, the program stored in the FROM3 performs lighting control for comparing the measured value with the threshold of the illuminance threshold table stored in the FROM3 in advance and changing the luminous intensity of the backlight 8 according to the comparison result. Based on the output voltage value of the optical sensor 5, the CPU 2 performs the brightness of the display surface in the "bright mode" when the surroundings are bright, and the "normal mode" when the brightness is normal. It is configured so that it can be changed in three steps so as to be set to the "dark mode" when is dark. Further, at this time, since the brightness of the display surface is controlled stepwise, in order to prevent the brightness of the display surface from fluttering when the measured illuminance changes in the vicinity of the threshold, the illuminance threshold table The threshold is set to have hysteresis.

In this case, as a characteristic of an IC (Integrated Circuit) that constitutes an optical sensor for measuring illuminance based on external light, even if the linearity of illuminance vs. output voltage is maintained, it is the same for each IC. Since there is a large variation in the output voltage when the illuminance and the variation gradient of the output voltage when the illuminance changes, when the illuminance threshold setting when performing the backlight brightness adjustment as described above is constant, Using an optical sensor with arbitrary illuminance output voltage characteristics,
In order to obtain a constant brightness state, it is necessary to correct the measured voltage to obtain the output voltage.

FIG. 6 shows an example of a conventional illuminance threshold value table. In the conventional illuminance threshold table 10,
The setting and correction of the illuminance threshold for switching between the "bright mode", the "normal mode" and the "dark mode" are performed as follows. First, when the brightness adjustment state of the backlight changes from the “normal mode” to the “bright mode” when the illuminance increases, the illuminance reference value is 90 h, and the correction value by the optical sensor at this time is correction. Further, when the illuminance is lowered, the illuminance reference value when the “bright mode” is changed to the “normal mode” is 60 h, and the correction value by the optical sensor at this time is correction. Further, when the illuminance increases, the illuminance reference value when the “dark mode” changes to the “normal mode” is 0Eh, and the correction value by the optical sensor at this time is correction. Furthermore, when the illuminance is lowered, the illuminance reference value when the "normal mode" is changed to the "dark mode" is 05h, and the correction value by the optical sensor at this time is correction.
The default value of the corrections shown in FIG. 6 is 00h.

L based on the illuminance threshold value table shown in FIG.
The brightness control of the CD 7 is performed as follows. In the following, a digital value obtained by A / D converting the output voltage of the optical sensor 5 is displayed as an A / D value. Here, the backlight lighting mode is set according to the A / D value as follows. To do. When 1.05h ≧ A / D value, the brightness of the backlight is adjusted by turning on the backlight in the “dark mode”. When 2.0Eh ≦ A / D value ≦ 60h, the brightness of the backlight is adjusted by turning on the backlight in the “normal mode”. 3.06h <A / D value <0Eh, 60h <A / D value <9
0h is a region having hysteresis. When 4.90h ≦ A / D value, the brightness of the backlight is adjusted by turning on the backlight in the “bright mode”.

FIG. 7 is a diagram for explaining a brightness control method of a conventional display device, which is a characteristic (solid line) of illuminance (lx) and output voltage (A / D value) by an optical sensor having an average characteristic. And the illuminance (l
x) and the output voltage (A / D value) characteristic (dotted line). In the case of FIG. 7, the required mode switching operation is such that when the illuminance decreases to 100 lx or less, the “normal mode” shifts to the “dark mode”, and the illuminance increases to 300 lx or more. , When the "dark mode" shifts to the "normal mode" and the illuminance decreases to 2000 lx or less, the "light mode" shifts to the "normal mode", and the illuminance rises to 3000 lx or more ,
It is to shift from the “normal mode” to the “bright mode”.

FIG. 8 is a diagram showing a configuration of a test system at the time of measuring an output of an optical sensor to which the prior art and the present invention are applied. At the time of measuring the output of the optical sensor, as shown in FIG. 8, the light source B and the mobile phone device 1 to be tested are installed in a dark box A that blocks external light, and the light from the light source B is transferred to the mobile phone device. The light receiving section D of the first optical sensor 5 is irradiated so that the illuminance at that time can be measured. Then, the external I of the mobile phone device 1
The personal computer C is connected via / O9 and a dedicated command is transmitted from the personal computer C to the CPU 2 of the mobile phone device 1 to measure the illuminance of the light applied to the light receiving section D by the optical sensor 5. After going through the cancer part I / O9,
The output data of the measurement result of the optical sensor 5 is sent to the personal computer C.
Return to.

The test of the illuminance vs. output voltage characteristic of the optical sensor using the test system shown in FIG. 8 is conducted as follows. First, the light source B irradiates uniform light such that the illuminance at the light receiving portion of the optical sensor becomes 3000 lx. Now, it is assumed that the optical sensor mounted on the mobile phone unit C has the characteristics of the sample X shown by the dotted line in FIG. As shown in the illuminance threshold value table of FIG. 6, the average output value of the optical sensor that is in the “bright mode” when the illuminance increases is as shown in FIG.
90h on the average characteristics shown by the solid line,
Actually, the sample X has the characteristic shown by the dotted line, so the output value at this time is F0h. So personal computer C
Corrects the difference between F0h and 90h, and
The CPU 2 of the mobile phone device 1 is controlled via O9 to perform FR.
The correction data is written in the correction value writing area of the illuminance threshold value table (FIG. 6) stored in the OM3.

Next, the light intensity of the light source B is lowered to irradiate with uniform light such that the illuminance at the light receiving portion of the photosensor becomes 2000 lx, and the same measurement is performed. Write the data to the illuminance threshold table. Further, by lowering the luminous intensity of the light source B and irradiating with uniform light so that the illuminance at the light-receiving portion of the photosensor becomes 100 lx, and performing the same measurement, the personal computer E obtains the correction data from the illuminance threshold value. Write on the table.
Next, by increasing the luminous intensity of the light source B and irradiating with uniform light such that the illuminance at the light receiving portion of the photosensor becomes 300 lx, and performing the same measurement, the personal computer E obtains the correction data from the illuminance. Write to the threshold table.

As described above, in the brightness control method of the conventional display device, the illuminance by the light source B is set to the illuminance which is the threshold in the illuminance threshold table, and the correction data corresponding to the variation in the characteristics of the optical sensor is set as the illuminance threshold. It was written in the correction value writing area of the table. By performing the correction in this way, the control method of the CPU 2 at the time of adjusting the light amount of the backlight is as follows. For example, in the "bright mode", when the value obtained by subtracting the correction from the A / D value measured by the optical sensor 5 is 60 h or less, the mode is switched to the "normal mode". For example, in the case of the sample X shown in FIG. 8, this corresponds to when the measured value becomes A0h or less. Further, when the A / D value which is the measured value by the optical sensor 5 is, for example, 30 h or less in the “normal mode” state, the correction is subtracted from the measured value, and the result is 05 h or less. For example, switch to "dark mode", and if the A / D value is 30h or more, subtract the correction from the measured value and the result is 90
If h or more, the mode is switched to the "bright mode".

As described above, in the conventional brightness control method for the display device, the variation in the characteristics of the photosensor is corrected by incorporating the correction data in the illuminance threshold value table. However, in this way,
When controlling the brightness of the display device, the light output correction amount for the illuminance is different for each optical sensor, so the correction value cannot be made a constant value, and the output voltage value corresponding to each illuminance threshold value is set. It was necessary to make a correction after checking. For example, as in the above example, it is necessary to perform the measurement twice at least corresponding to the threshold illuminance on the upper and lower sides. Furthermore, in order to prevent fluttering during mode switching, when a threshold value for mode switching has hysteresis, two measurements are performed for increasing the illuminance and for decreasing the illuminance. Four measurements had to be taken to determine the correction value.

[0016]

Conventionally, in a portable telephone device or the like, when deciding an output voltage value of an optical sensor for controlling the brightness of a display device, an illuminance of a standard value set at a predetermined stage is set in advance. According to the threshold value, a correction value is set for each optical sensor according to its output characteristic, and the measured voltage value is corrected using this correction value to determine the output voltage value. However, there is a problem that the number of times of measurement required when determining such a correction value is large, and thus the inspection time of the mobile phone device or the like becomes long, which inevitably affects the cost.

The present invention has been made in view of the above circumstances, and when the output voltage value of the optical sensor for controlling the brightness of the display device is determined, only one measurement is required. It is an object of the present invention to provide a brightness control method for a display device capable of creating an illuminance threshold value table that defines a required output voltage value.

[0018]

In order to solve the above-mentioned problems, the invention according to claim 1 relates to a brightness control system of a display device, and a plurality of threshold values for an output voltage value of an optical sensor for measuring the illuminance of a light receiving portion. With an illuminance threshold table that stores
When the output voltage value of the optical sensor exceeds the threshold value, in the display device configured to sequentially switch the brightness of the display surface according to a plurality of modes corresponding to a predetermined level of the ambient brightness, as the illuminance threshold value table. , Each threshold value in the illuminance threshold value table corresponding to the optical sensor having a standard illuminance vs. output voltage characteristic is rewritten by an output voltage value corresponding to each threshold value by the optical sensor having an arbitrary illuminance vs. output voltage characteristic Is used, it is possible to switch the brightness corresponding to the plurality of modes by using the optical sensor having the arbitrary illuminance-to-output voltage characteristic.

The invention according to claim 2 relates to the brightness control system of the display device according to claim 1, wherein when the illuminance threshold value table is rewritten, the standard illuminance vs. output corresponding to any one of the threshold values. Rewriting the output voltage value of the photosensor having a voltage characteristic by the output voltage value corresponding to the one threshold value by the photosensor having the arbitrary illuminance-to-output voltage characteristic, and corresponding to another threshold value. The output voltage value of the photosensor having the standard illuminance-to-output voltage characteristic is determined as the illuminance-output voltage characteristic of the photosensor is linear, and the corresponding output voltage value of the photosensor having the arbitrary illuminance-to-output voltage characteristic is obtained. It is characterized by rewriting by.

Further, the invention according to claim 3 relates to the brightness control system of the display device according to claim 2, wherein the one threshold value is a maximum value threshold value in the illuminance threshold value table. .

The invention according to claim 4 relates to the brightness control method of the display device according to any one of claims 1 to 3, wherein the plurality of modes are a dark mode, a normal mode and a bright mode. In the illuminance threshold table, an illuminance threshold for mode switching when the illuminance changes to a normal mode or a bright mode in an ascending direction, and an illuminance threshold for mode switching when an illuminance changes to a normal mode or a dark mode in a descending direction. Are specified respectively.

The invention according to claim 5 relates to the brightness control method of the display device according to any one of claims 1 to 3, wherein the plurality of modes are a dark mode, a dark mode and a normal mode. Consisting of a bright mode and a bright mode, in the illuminance threshold table, the illuminance threshold for mode switching when the illuminance changes to the slightly dark mode or the normal mode or the slightly bright mode or the bright mode, and the illuminance to the descending direction. It is characterized in that it defines an illuminance threshold for mode switching when changing to a slightly bright mode or a normal mode, or a slightly dark mode or a dark mode, respectively.

The invention according to claim 6 relates to the brightness control method of the display device according to any one of claims 1 to 5, wherein the display device includes a liquid crystal panel and a backlight for illuminating the liquid crystal panel from the back. And a light, and the brightness of the display surface is controlled by adjusting the luminous intensity of the backlight.

The invention according to claim 7 relates to the brightness control method of the display device according to any one of claims 1 to 6, wherein the display device forms a display portion of a portable telephone device. It is characterized by that.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The description will be specifically made using the embodiments. First Example FIG. 1 is a diagram for explaining a brightness control method of a display device in a first example of the present invention, and FIG. 2 is a diagram showing an illuminance threshold value table in this example. In addition, in FIG.
(A) shows the illuminance threshold table which described the default value, (b) has shown the illuminance threshold table which corrected the default value corresponding to the specific sample X. The configuration of the mobile phone device to which the brightness control method of the display device of this example is applied is the same as that of the conventional example shown in FIG. 5, and in the mobile phone device 1, the LCD 7 in the LCD 7 is adjusted according to the ambient brightness. The same applies to the operation of changing the brightness of the display surface. Further, the configuration of the test system at the time of measuring the photosensor output voltage in the brightness control system of the display device of this example is the same as that of the conventional example shown in FIG. 8, so a detailed description thereof will be given below. Omit it.

Next, the brightness control system of the display device in this example will be described with reference to FIGS. As shown in FIG. 8, the mobile phone device 1 is installed in the dark box A.
Then, the light source B irradiates the light receiving section D of the optical sensor 5 with uniform light of 3000 lx which is the threshold value of the “bright mode”. The personal computer C measures the illuminance at the light receiving portion D by the optical sensor 5 by transmitting a dedicated command to the CPU 2 via the external I / O 9 of the mobile phone device 1. Then, the measurement result of the optical sensor 5 is used as the external I
Return to PC C via / O9. At this time, the optical sensor mounted on the mobile phone device 1 has the characteristics of the sample X shown in FIG.

FIG. 1 is a diagram for explaining the brightness control system of the display device in this example, which shows the characteristics (solid line) of the illuminance and the output voltage (A / D value) by an optical sensor having average characteristics. The illuminance and the output voltage (A / D value) characteristic (dotted line) of the specific sample X by the optical sensor are shown. Figure 1
In the case of, the required mode switching operation is to shift from the “normal mode” to the “dark mode” when the illuminance is decreased to 100 lx or less, and when the illuminance is increased to 300 lx or more, When the transition from "dark mode" to "normal mode" occurs and the illuminance drops below 2000 lx,
This is to shift from the “bright mode” to the “normal mode” and shift to the “bright mode” from the “normal mode” when the illuminance rises to 3000 lx or more.

In the brightness control system of the display device of this example, the fact that the photosensor has a linear characteristic of illuminance vs. output voltage (A / D value) is utilized, and sample X of sample X shown by a dotted line in FIG. 1 is used. The "slope" of the illuminance vs. A / D value characteristic is obtained from the output voltage A / D value at a specific illuminance, and the "slope" is equal to the average optical sensor characteristic.
By determining the output voltage value of a specific photosensor, it is possible to correctly perform the required mode switching using a photosensor having arbitrary characteristics.

More specifically, in the brightness control method for the display device of this example, the photosensor output voltage corresponding to the threshold illuminance when the "normal mode" is switched to the "bright mode" is 3000 lx. Obtained from the measurement results, this is taken as the A / D value (3000). Next, illuminance 3000
2000lx, 300x, 100l which becomes the illuminance threshold from the "inclination" determined from lx and A / D value (3000)
Obtaining the A / D value at x by calculation,
A / D value (3000 * 2000), A / D value (3000
* 300) and A / D value (3000 * 100). Then, the personal computer C uses the A / D value (3000) and the A / D value calculated in this way as threshold values to determine the external I
Each "default value" of the illuminance threshold value table 11 that stores the default value, as shown in FIG. 2A, stored in the FROM 3 by controlling the CPU 2 via / O9.
Then, the threshold value is overwritten. Here, in the illuminance threshold value table shown in FIG. 2A, the illuminance threshold value by an optical sensor having an average characteristic is written as the "default value".

For example, in the case of the sample X shown in FIG. 1, since the A / D value at 3000 lx is F0h, it is A0h at 2000 lx and 1 at 300 lx.
It can be calculated that the optical sensor outputs an A / D value of 08h at 8h and 100lx. Therefore, the A / D value F0h obtained from the measurement and the A / D value obtained from the calculation
0h, 18h, 08h are written to the default values of the illuminance threshold value table shown in FIG. 2A under the control of the personal computer C, and for the specific sample X as shown in FIG. 2B, Illuminance threshold table 12 after correction
To get The corrected illuminance threshold table has different illuminance thresholds for each device depending on the variation of the optical sensor.

By using the corrected illuminance threshold value table 12 as shown in FIG. 2B, the CPU 2
In the case of the optical sensor of sample X, the optical sensor output voltage A / D
Depending on the value, set the backlight lighting mode as follows. When 1.08h ≧ A / D value, the brightness of the backlight is adjusted by turning on the backlight in the “dark mode”. When 2.18h ≦ A / D value ≦ A0h, the brightness of the backlight is adjusted by turning on the backlight in the “normal mode”. 3.08h <A / D value <18h, A0h <A / D value <F
0h is a region having hysteresis. 4. When F0h ≦ A / D value, the brightness of the backlight is adjusted by turning on the backlight in the “bright mode”.

By making such a correction, the CP
In the case of the sample X shown in FIG. 1, for example, in the “bright mode” state, U2 switches to the “normal mode” when the measured value becomes A0h or less. Also, "normal mode"
In the state, if the measured value is 08h or less, the mode is switched to the "dark mode", and if it is F0h or more, the mode is switched to the "bright mode". Therefore, it is the same as when the optical sensor output voltage is corrected by the conventional method. The operation of can be performed.

As described above, according to the brightness control method of the display device of this example, the illuminance at the time of determining the output voltage value of the optical sensor corresponding to the illuminance threshold may be constant at 3000 lx, for example, so that maintenance of the light source is possible. In addition to being easy, the measurement at the time of inspecting the characteristics of the optical sensor and the writing to the illuminance threshold value table need only be performed once, so that the inspection time can be greatly shortened as compared with the case of the conventional method. It will be possible.

Second Embodiment FIG. 3 is a diagram showing a brightness control system of a display device in a second embodiment of the present invention, and FIG. 4 is a diagram showing an illuminance threshold value table in the present embodiment. The illuminance threshold table in the brightness control method of the display device of this example is obtained by further dividing the illuminance threshold table shown in FIG. 2 into, for example, “bright mode”, “slightly bright mode”, “normal mode”, “slightly bright”. There are five levels of "dark mode" and "dark mode". The configuration of the mobile phone device to which the brightness control method of the display device of this example is applied is the same as that of the conventional example shown in FIG.
In the mobile phone device 1, the LCD according to the ambient brightness
The operation of changing the brightness of the display surface in 7 is also the same. Further, the configuration of the test system at the time of correcting the optical sensor output in the optical sensor output correcting method of this example is the same as that of the conventional example shown in FIG. 8, and therefore detailed description thereof will be omitted below. To do.

The brightness control system of the display device in this example will be described below with reference to FIGS. 3, 4, 5, and 8. As shown in FIG. 8, the mobile phone device 1 is installed in the dark box A.
Then, the light source B irradiates the light receiving section D of the optical sensor 5 with uniform light of 3000 lx which is the threshold value of the “bright mode”. The personal computer C measures the illuminance at the light receiving portion D by the optical sensor 5 by transmitting a dedicated command to the CPU 2 via the external I / O 9 of the mobile phone device 1. Then, the measurement result of the optical sensor 5 is used as the external I
Return to PC C via / O9. At this time, the optical sensor mounted in the mobile phone device 1 has the characteristics of the sample X shown in FIG.

FIG. 3 is a diagram for explaining the brightness control system of the display device in this example, in which the characteristics (solid line) of the illuminance and the output voltage (A / D value) by the photosensor having the average characteristics, The illuminance and the output voltage (A / D value) characteristic (dotted line) of the specific sample X by the optical sensor are shown. Figure 3
In the case of, the required mode switching operation is "slightly dark mode" when the illuminance drops to 100 lx or less.
To "dark mode", the illuminance increases and 200 lx
When the above is reached, go from "Dark Mode" to "Slightly Dark Mode"
When the illuminance is decreased to 300 lx or less, the “normal mode” is changed to “slightly dark mode”, and when the illuminance is increased to 400 lx or more, “slightly dark mode” is changed to “normal” Mode ”, the illuminance decreases and
When it is less than 00lx, it shifts from "slightly bright mode" to "normal mode", and when the illuminance rises to 1000lx or more, it shifts from "normal mode" to "slightly bright mode" and illuminance falls. Then, when it becomes 2000 lx or less, it shifts from “bright mode” to “slightly bright mode”, and when the illuminance rises to 3000 lx or more, it shifts from “slightly bright mode” to “bright mode”. is there.

In the brightness control method of the display device of this example, the fact that the photosensor has a linear characteristic of illuminance vs. output voltage (A / D value) is utilized, and sample X of sample X shown by a dotted line in FIG. 3 is used. "Slope" of illuminance vs. A / D value characteristic is 3000l
It is determined from the A / D value (3000) which is the measurement result when x. Next, from the obtained "tilt", a brightness threshold value 20
00lx, 1000lx, 900lx, 400lx, 3
The A / D values at 00x, 200lx, and 100lx are calculated, and the A / D values (3000 * 2) are calculated.
000), A / D value (3000 * 1000), A / D value (3000 * 900), A / D value (3000 * 40)
0), A / D value (3000 * 300), A / D value (30
00 * 200) and A / D value (3000 * 100). Then, the personal computer C displays the A / D value (3000),
Using the A / D value calculated in this way as a threshold,
FROM 2 controlling the CPU 2 via the external I / O 9
The threshold value is overwritten on the "default value" of the illuminance threshold value table that stores the default value stored in 3. Here, the illuminance threshold value table in which the default value is described has the illuminance threshold value by the photosensor having an average characteristic written as the "default value".

For example, in the case of the sample X shown in FIG. 3, since the A / D value at 3000 lx is F0h, it is A0h at 2000lx, 50h at 1000lx, and 48h at 900lx. , 400l
20 hours at x, 18 hours at 300lx, 2
It is found from calculation that the optical sensor outputs an A / D value that is 10 h at 00 lx and 08 h at 100 lx. Therefore, the A / D value F0h obtained from the measurement
And A0h, 50h, 48h, 20 obtained from the calculation
h, 18h, 10h, 08h are written in the default values of the illuminance threshold table under the control of the personal computer C, and the corrected illuminance threshold table 13 for the specific sample X as shown in FIG. 4 is displayed. obtain. The corrected illuminance threshold table has different illuminance thresholds for each device depending on the variation of the optical sensor.

By using the corrected illuminance threshold table as shown in FIG.
In the case of the optical sensor of No. 1, the lighting mode of the backlight is set as follows according to the optical sensor output voltage A / D value. When 1.08h ≧ A / D value, the brightness of the backlight is adjusted by turning on the backlight in the “dark mode”. When 2.10h ≦ A / D value ≦ 18h, the brightness of the backlight is adjusted by turning on the backlight in the “slightly dark mode”. 3.08h <A / D value <10h, 18h <A / D value <2
0h is a region having a "slightly dark mode" hysteresis. When 4.20h ≦ A / D value ≦ 48h, the brightness of the backlight is adjusted by turning on the backlight in the “normal mode”. 5.18h <A / D value <20h, 48h <A / D value <5
0h is a region having a "normal mode" hysteresis. When 6.50h ≦ A / D value ≦ A0h, the brightness of the backlight is adjusted by turning on the backlight in the “slightly bright mode”. 7.48h <A / D value <50h, A0h <A / D value <F
0h is a region having a "slightly bright mode" hysteresis. 8. When F0h ≦ A / D value, the brightness of the backlight is adjusted by turning on the backlight in the “bright mode”.

By thus determining the output voltage value of the optical sensor, the CPU 2 causes the sample X shown in FIG.
In the case of, for example, in the “bright mode” state, the measured value is F
When it becomes 0h or less, it switches to "slightly bright mode".
In the "normal mode", when the measured value is 48h or less, the mode is switched to "slightly dark mode", and when it is 50h or more, the mode is switched to "slightly bright mode". It is possible to perform the same operation as when the correction is performed.

As described above, according to the brightness control method of the display device of this example, since the number of illuminance thresholds is increased, the brightness of the display device can be controlled more strictly, and the output voltage of the photosensor can be controlled. The illuminance at the time of measurement is, for example, 30
Since 001x is constant, maintenance of the light source is easy, and measurement at the time of inspecting the characteristics of the optical sensor and writing to the illuminance threshold value table need only be performed once, so compared with the conventional method. The inspection time can be shortened significantly.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific structure is not limited to this embodiment, and there are design changes and the like without departing from the scope of the invention. However, it is included in this invention. For example, the display device to which the present invention is applied is not limited to a display device having a liquid crystal panel and a backlight, but can be applied to other types of display devices having no backlight.
Further, in the above-described embodiment, the case of the mobile phone device has been described, but the present invention is not limited to this, and it may change outdoors, indoors, or both fixed use and mobile use, for example, day and night. May be used in the environment,
It can be applied to a device having an indicator.

[0043]

As described above, according to the brightness control method for a display device of the present invention, only one kind of illuminance value is used when the brightness of the display device is controlled according to the ambient brightness. By measuring the illuminance with the light from the light source, it is possible to obtain the illuminance threshold table necessary for controlling the brightness of the display device using the optical sensor with variations in illuminance-to-output voltage characteristics. In addition to improving the maintainability of the inspection system, it is possible to significantly reduce the inspection time.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a brightness control method of a display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an illuminance threshold value table in the present embodiment.

FIG. 3 is a diagram illustrating a brightness control method of a display device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an illuminance threshold value table in the present embodiment.

FIG. 5 is a block diagram showing a configuration of a conventional mobile phone device to which the present invention is applied.

FIG. 6 is a diagram showing an example of a conventional illuminance threshold value table.

FIG. 7 is a diagram illustrating a brightness control method of a conventional display device.

FIG. 8 is a diagram showing a configuration of a test system at the time of measuring an output of an optical sensor to which a conventional and the present invention are applied.

[Explanation of symbols]

1 Mobile phone device 2 Central processing unit (CPU) 3 FROM 4 SRAM 5 Optical sensor 6 A / D conversion circuit 7 LCD 8 backlight 9 External I / O 11, 12, 13 Illuminance threshold table

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 680 G09G 3/20 680S 3/34 3/34 J 3/36 3/36 F term (reference) ) 2H091 FA41X FA41Z FD22 LA12 LA16 2H093 NC42 NC49 NC50 NC52 NC55 NC62 ND02 ND07 ND53 ND54 ND56 NH18 5C006 AA02 AF13 AF46 AF54 AF63 AF81 BF09 BF39 CB01 CB01 QC02 EA01 EJ02 EJ01 EB01 EA02 EJ02 EJ01 EJ01 EJ02 EJ01 DD02 DD15 DD15 DD02 DD15 DD15 DD02 DD15 DD15 DD02 DD15 DD02 DD15 DD15 DA71 EA20 MM07 MM09 MM10

Claims (7)

[Claims] 1. An illuminance threshold table that stores a plurality of threshold values for an output voltage value of an optical sensor that measures the illuminance of a light receiving unit, and when the output voltage value of the optical sensor exceeds the threshold value, the brightness of the display surface is displayed. In a display device adapted to sequentially switch according to a plurality of modes corresponding to a predetermined level of ambient brightness, as the illuminance threshold value table, the illuminance threshold value corresponding to an optical sensor having a standard illuminance vs. output voltage characteristic. By using each threshold value in the table rewritten by the output voltage value corresponding to each threshold value by the optical sensor having an arbitrary illuminance-output voltage characteristic, an optical sensor having the arbitrary illuminance-output voltage characteristic can be obtained. A brightness control method for a display device, wherein the brightness can be switched in correspondence with the plurality of modes by using the brightness control method. 2. When rewriting the illuminance threshold table, the output voltage value of the photosensor having the standard illuminance-to-output voltage characteristic corresponding to any one of the thresholds is set to the arbitrary illuminance-to-output voltage characteristic. By rewriting the output voltage value corresponding to the one threshold value by the optical sensor, the output voltage value of the optical sensor having the standard illuminance-to-output voltage characteristic corresponding to another threshold value is changed to the illuminance value of the optical sensor. 2. The brightness control method for a display device according to claim 1, wherein the brightness is rewritten according to a corresponding output voltage value of the photosensor having the arbitrary illuminance-to-output voltage characteristic, which is obtained assuming that the output voltage characteristic is linear. 3. The brightness control method for a display device according to claim 2, wherein the one threshold value is a maximum value threshold value in the illuminance threshold value table. 4. The plurality of modes includes a dark mode, a normal mode, and a bright mode, and in the illuminance threshold table, an illuminance threshold for mode switching when the illuminance changes in an increasing direction to the normal mode or the bright mode. 4. The brightness control method for a display device according to claim 1, further comprising: an illuminance threshold for mode switching when the illuminance is changed to a normal mode or a dark mode in a descending direction. . 5. The plurality of modes are composed of a dark mode, a slightly dark mode, a normal mode, a slightly bright mode and a bright mode, and in the illuminance threshold value table, the illuminance is slightly increased in a dark mode or a normal mode or a little. It defines the illuminance threshold for mode switching when changing to bright mode or bright mode and the illuminance threshold for mode switching when changing illuminance to slightly bright mode or normal mode or slightly dark mode or dark mode. 4. The brightness control method for a display device according to claim 1, wherein the brightness control method is for a display device. 6. The display device comprises a liquid crystal panel and a backlight for illuminating the liquid crystal panel from the back side, and the brightness of the display surface is controlled by adjusting the luminous intensity of the backlight. The brightness control method for a display device according to claim 1. 7. The display device forms a display portion of a mobile phone device, according to any one of claims 1 to 6.
2. A brightness control method for a display device according to any one of 1.