JP2002323690A - Automatic light control method and device for liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically control the luminance of a display screen according to various individuals' preferences and to control luminance to be matched with individuals' tastes. SOLUTION: When one out of a first to a fourth functions F1(x)-F4(x) is selectively set to calculate luminance y taking ambient illuminance x as a variable by operating an operation part 3, the luminance y corresponding to the ambient illuminance x is found based on the set function and a backlight 11 is made to emit light with the luminance y. Furthermore, brightness of the display screen of a color liquid crystal panel 12 is stabilized by variation of the luminance y in incremental steps and hysteresis characteristics of the backlight 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic light control device for a liquid crystal display device which automatically adjusts the brightness of a backlight of the liquid crystal display device according to the illuminance of the surroundings.

[0002]

2. Description of the Related Art As is well known, when the periphery of a display device is bright, the display screen is felt dark, and when the periphery is dark, the display screen is bright. In particular, in a liquid crystal display device,
Since the amount of light emission is smaller than that of a CRT, it is necessary to adjust the brightness of the display screen according to the peripheral brightness.

For example, JP-A-5-241512 and JP-A-9-146073 provide an optical sensor for detecting the peripheral brightness, and a display of a liquid crystal display device according to the detected peripheral brightness. A technique of adjusting screen brightness has been disclosed.

[0004]

However, according to the above-mentioned conventional technique, the brightness of the display screen has not been automatically adjusted according to various personal preferences. That is,
Although there is an individual difference in the brightness of the display screen that is felt to be optimal according to the peripheral brightness, it was not possible to cope with this individual difference.

[0005] Further, although the periphery may be very dark or very bright, the brightness of the display screen is only monotonically increased or decreased with respect to the surrounding brightness. Could not be performed.

Accordingly, the present invention provides an automatic adjustment of a liquid crystal display device capable of automatically adjusting the brightness of a display screen according to various personal tastes and adjusting the brightness in accordance with individual senses. It is an object to provide an optical method and apparatus.

[0007]

In order to solve the above-mentioned problems, the present invention relates to a method for automatically adjusting the brightness of a backlight of a liquid crystal display device. A detecting step of detecting, a selecting step of selecting any one of a plurality of functions set in advance for calculating luminance using the surrounding illuminance as a variable, and, based on the selected function, detecting the surrounding illuminance. The method includes a luminance setting step of obtaining a corresponding luminance, and a luminance adjusting step of causing a backlight to emit light at the obtained luminance.

According to such a method of the present invention, when any one of a plurality of functions is selected, the luminance corresponding to the surrounding illuminance is determined based on the selected function, and the backlight is determined by the determined luminance. Is emitted. That is, the relationship between the surrounding illuminance and the luminance of the display screen can be changed depending on which function is selected. For this reason, it is possible to automatically adjust the brightness of the display screen according to various personal preferences.

In the present invention, the selecting step includes a step of displaying the luminance on a display screen of the liquid crystal display device, a step of adjusting the displayed luminance, and a step of selecting each function according to the displayed luminance. Selecting one of the following.

Here, the brightness displayed on the display screen of the liquid crystal display device is adjusted, and one of the functions is selected according to the brightness. For example, a function for adjusting the luminance of the display screen to a higher level or a function for adjusting the luminance to a lower level with respect to the illuminance around the liquid crystal display device is set in advance, and based on the luminance displayed on the display screen. Then, one of the functions is appropriately selected.

Further, in the present invention, the luminance setting step compares the detected peripheral illuminance with each of the preset levels, and makes the luminance correspond to the illuminance of each level based on the selected function. In this case, the luminance is gradually increased and decreased, and the luminance is gradually increased and decreased with a hysteresis characteristic.

As described above, the luminance is gradually increased or decreased, and
If the hysteresis characteristic is given to the gradual increase and decrease of the brightness,
The brightness of the display screen is stabilized without frequently changing.

Next, according to the present invention, there is provided an automatic dimming method for a liquid crystal display device for adjusting the brightness of a backlight of the liquid crystal display device, wherein a detecting step for detecting illuminance around the liquid crystal display device is performed. And selecting a luminance corresponding to the detected peripheral illuminance based on a preset function for calculating the luminance using the peripheral illuminance as a variable. The method includes a luminance setting step of setting the luminance by limiting the selected saturation luminance, and a luminance adjusting step of causing the backlight to emit light at the set luminance.

According to the present invention, since the luminance obtained based on the function is limited by the selected saturation luminance, the maximum luminance of the display screen can be restricted according to various personal preferences. .

In the present invention, the selecting step includes a step of displaying the luminance on a display screen of the liquid crystal display device, a step of adjusting the displayed luminance, and a step of adjusting each saturation according to the displayed luminance. Selecting one of the luminances.

Here, the luminance displayed on the display screen of the liquid crystal display device is adjusted, and one of the saturation luminances is selected according to the luminance. For example, the saturation luminance for limiting the maximum luminance of the display screen to a high level and the saturation luminance for restricting the luminance to a low level with respect to the illuminance around the liquid crystal display device are set in advance and displayed on the display screen. One of the saturation luminances is appropriately selected based on the luminance.

Further, according to the present invention, the luminance setting step compares the detected illuminance of the surrounding area with each of the preset levels, and adjusts the luminance to the illuminance of each level based on the selected function. In this way, the luminance gradually increases and decreases, and the luminance gradually increases and decreases to have a hysteresis characteristic.

The luminance of the display screen is stabilized by such a stepwise increase and decrease in luminance and the hysteresis characteristic.

Next, according to the present invention, there is provided an automatic dimming method for a liquid crystal display device for adjusting the brightness of a backlight of the liquid crystal display device. Selecting a function corresponding to an illuminance range and selecting a function corresponding to an illuminance range including the detected peripheral illuminance from among respective functions for calculating luminance using the peripheral illuminance as a variable; And a brightness adjustment step of causing a backlight to emit light at the determined brightness based on the calculated brightness.

According to the method of the present invention, a function corresponding to the illuminance range including the peripheral illuminance is selected from the plurality of functions, and the detected peripheral illuminance is determined based on the selected function. Is obtained, and the backlight is emitted with the obtained brightness. For example, by setting in advance a function for adjusting the luminance of the display screen when the illuminance around the liquid crystal display device is high and a function for adjusting the luminance of the display screen when the illuminance is low, the luminance of the display screen can be adjusted. Can be adapted to the individual's senses.

Further, in the present invention, an instruction step of instructing the luminance of the backlight, the instructed luminance and the illuminance of the surroundings detected when the luminance is instructed, and the illuminance of the detected surroundings are determined. And a function setting step of obtaining a reference value for setting a function corresponding to the included illuminance range.

Here, the luminance of the backlight is specified,
At this time, the designated luminance and the peripheral illuminance are obtained as reference values for setting a function corresponding to the illuminance range including the peripheral illuminance. For this reason, it is possible to easily set a function according to personal preference by appropriately instructing the luminance of the backlight.

Further, in the present invention, each time the luminance is specified, the illuminance range including the peripheral illuminance detected when the luminance is specified is increased.

Here, the illuminance range is increased each time the luminance is specified. Also, at this time, the designated luminance and the surrounding illuminance can be obtained as reference values for setting the function, so that the illuminance range and the function can be set only by specifying the luminance.

Further, in the present invention, an illuminance range including the peripheral illuminance detected when the luminance is designated is selected from a plurality of illuminance ranges set in advance.

Here, a plurality of illuminance ranges are set in advance, and one of the illuminance ranges is selected when the luminance is instructed. Also, at this time, the designated luminance and the surrounding illuminance can be obtained as reference values for setting the function, so that each function corresponding to each illuminance range can be determined while appropriately setting each illuminance range. Can be set.

Next, the present invention relates to an automatic light control device for a liquid crystal display device for adjusting the brightness of the backlight of the liquid crystal display device, wherein a detecting means for detecting the illuminance around the liquid crystal display device, Selecting means for selecting any one of a plurality of preset functions for calculating luminance, and comparing the detected peripheral illuminance with each preset level, based on the selected function, A brightness setting means for increasing or decreasing stepwise in accordance with the illuminance of each level, and having a hysteresis characteristic for the stepwise increase or decrease in luminance, and a luminance adjustment means for emitting a backlight at the determined luminance. ing.

According to the apparatus of the present invention as described above, the relationship between the illuminance of the surrounding area and the luminance of the display screen can be changed depending on which function is selected. The screen brightness can be automatically adjusted.

According to the present invention, there is provided an automatic light control device for a liquid crystal display device for adjusting the brightness of a backlight of the liquid crystal display device, wherein a detecting means for detecting illuminance around the liquid crystal display device, A luminance corresponding to the detected peripheral illuminance is obtained based on a selection means for selecting one of the saturation luminances and a preset function for calculating the luminance using the peripheral illuminance as a variable. There are provided a luminance setting means for setting the luminance by limiting the selected saturation luminance, and a luminance adjusting means for emitting a backlight at the set luminance.

According to such an apparatus of the present invention as well, since the luminance obtained based on the function is limited by the selected saturation luminance, the maximum luminance of the display screen can be restricted according to various personal preferences. .

Further, according to the present invention, there is provided an automatic light control device for a liquid crystal display device for adjusting the brightness of a backlight of the liquid crystal display device, comprising: a detecting means for detecting illuminance around the liquid crystal display device; Selecting means for selecting a function corresponding to the illuminance range including the detected peripheral illuminance from among the respective functions for calculating the luminance using the peripheral illuminance as a variable corresponding to the range, A luminance setting unit that calculates a luminance corresponding to the detected peripheral illuminance based on the detected luminance; and a luminance adjustment unit that causes a backlight to emit light at the determined luminance.

Also according to the apparatus of the present invention, a function corresponding to the illuminance range including the peripheral illuminance is selected, and a luminance corresponding to the detected peripheral illuminance is obtained based on the selected function. Since the backlight emits light at the determined luminance, it is possible to adjust the luminance of the display screen to a human sense.

[0033]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a liquid crystal display device to which the first embodiment of the automatic light control method of the present invention is applied.
In this liquid crystal display device, a plurality of functions for calculating luminance using the surrounding illuminance as a variable are stored in advance, and when any of the functions is selected, based on the selected function,
The luminance corresponding to the surrounding illuminance is obtained, and the backlight of the display screen is caused to emit light at this luminance.

In FIG. 1, the liquid crystal display unit 1
An FT-type color liquid crystal panel 12 and a backlight 11 disposed on the back of the panel are provided. Backlight 11
Is a cold cathode ray tube, for example, which emits light by receiving an AC drive signal from the inverter circuit 4 and increases or decreases its luminance in accordance with the amount of current of the AC drive signal. Alternatively, a backlight whose luminance increases or decreases according to the voltage of the drive signal may be used as the backlight 11.

The display control unit 2 has a built-in CPU, input / output ports, memory, and the like. In the memory of the display control unit 2, a program for controlling the liquid crystal display unit 1, a display program for displaying and developing display data on a display screen of the color liquid crystal panel 12, and a program for changing the brightness of the backlight 11 Etc. are stored.

The display control unit 2 reads the display data from the display memory 6, converts the display data into RGB signals, and applies the RGB signals to the interface circuit 9. The interface circuit 9 supplies the RGB signals to a display drive circuit (not shown) of the color liquid crystal panel 12. Thus, an image is displayed on the display screen of the color liquid crystal panel 12.

The display control unit 2 applies a digital signal having a frequency corresponding to the luminance of the backlight 11 to the inverter circuit 4. The inverter circuit 4 generates an AC drive signal corresponding to the frequency of the digital signal, and applies the AC drive signal to the backlight 11. As a result, the backlight 11 emits light and its brightness is set.

Further, the display control unit 2 receives the display data from the OSD circuit 7, combines the display data with the display data read from the display memory 6, and outputs an RGB signal indicating a combined image. As a result, the composite image is displayed on the display screen of the color liquid crystal panel 12. The OSD circuit 7 receives an input instruction from the operation unit 3 such as a keyboard or a mouse through the display control unit 2, and updates display data in response to the input instruction.

The optical sensor 10 detects the illuminance around the liquid crystal display device and applies a detection signal indicating the illuminance around the liquid crystal display to the A / D converter 8. The A / D converter 8 converts the detection signal into a digital signal and applies the digital signal to the display control unit 2. In addition, the optical sensor 10 is disposed at a position where irradiation light from the backlight 11 does not enter. Further, the light sensor 10 has a characteristic that the light receiving sensitivity increases as the illuminance decreases. As the illuminance decreases, the amount of change in the detection signal with respect to the constant amount of change in the illuminance increases.

Now, in the liquid crystal display device having such a configuration,
One of the first function F1 (x) = a + b1, the second function F2 (x) = a + b2, the third function F3 (x) = a + b3, and the fourth function F4 (x) = a + b4 shown in the graph of FIG. Based on this, the luminance y of the backlight 11 corresponding to the surrounding illuminance x detected by the optical sensor 10 is obtained. In this graph, the surrounding illuminance x is represented in a range of 0 to 800 lux,
The luminance y is expressed in the range of 100 to 200 cd / m ² . For example, when the first function F1 (x) = a + b1, the surrounding illuminance x detected by the optical sensor 10 is 400 Lu.
x, the luminance y of the backlight 11 is 180 cd /
m ² . The brightness y of the backlight 11 corresponds to the brightness of the display screen of the color liquid crystal panel 12.

When the first function F1 (x) = a + b1 is selected,
The luminance y of the backlight 11 is set to be the highest, and the display screen of the color liquid crystal panel 12 becomes the brightest. When the second function F2 (x) = a + b2 is selected, the display screen becomes slightly darker. When the third function F3 (x) = a + b3 is selected, the display screen further darkens, and the fourth function F4 (x) = a + b4 is changed. When selected, the display screen is darkest.

The display control unit 2 calculates the first function F1 (x) =
a + b1 and the complement b of the second to fourth functions F2 (x) to F4 (x)
2 to b4 are stored in the memory of the display control unit 2, and the complement b1 of the first function F1 (x) = a + b1 is added to each complement b1.
The second to fourth functions F2 (x) to F4 (x) are set by substituting any one of 2 to b4.

Note that the first function F1 (x) = a + b1 and each complement b
Instead of storing 2 to b4, the first to fourth functions F1 (x) to
Each of the data tables corresponding to F4 (x) may be stored, and one of these data tables may be selected, and the luminance y corresponding to the illuminance x may be obtained by referring to the selected table.

When selecting one of the first to fourth functions F1 (x) to F4 (x), the operation unit 3 is operated to instruct the display control unit 2 to select a function. In response, the display control unit 2 activates the OSD circuit 7. The OSD circuit 7 has a bar symbol 2 as shown in FIG.
1 through the display control unit 2
Is displayed on the display screen. Each range m1 to m4 of the length of the bar symbol 21 corresponds to the first to fourth functions F1 (x) to F4 (x). By operating the operation unit 3, the bar symbol 21 can be reduced or expanded by the display control unit 2.
When instructing the SD circuit 7, the OSD circuit 7 reduces or expands the bar symbol 21 on the display screen of the color liquid crystal panel 12. After appropriately adjusting the length of the bar symbol 21 and further operating the operation unit 3 to instruct selection of a function, the length of the bar symbol 21 is reduced to the range m1.
Ｍm4, the first to fourth functions F1
One of the flags F1 to F4 indicating (x) to F4 (x) is instructed to the display control unit 2. Display control unit 2
Selects one of the first to fourth functions F1 (x) to F4 (x) depending on which of the flags F1 to F4 is indicated.

In other words, the length of the bar symbol 21 corresponds to the brightness of the display screen of the color liquid crystal panel 12, and the first to fourth functions F1 (x) to F1
One of 4 (x) is selected.

On the other hand, in the linear functions such as the first to fourth functions F1 (x) to F4 (x), even if the illuminance x slightly changes, the luminance y changes accordingly. Therefore, when the backlight 11 emits light at the luminance y derived by the linear function, the brightness of the display screen of the color liquid crystal panel 12 becomes unstable. For example, even if a person crosses in front of the optical sensor 10 or the temperature of the optical sensor 10 fluctuates temporarily and the illuminance x detected by the optical sensor 10 changes, the luminance y of the backlight 11 changes. Therefore, the brightness of the display screen of the color liquid crystal panel 12 changes.

In order to stabilize the brightness of the display screen of the color liquid crystal panel 12, the luminance y of the backlight 11 is changed stepwise and with a hysteresis characteristic as shown in the graph of FIG. . In this graph,
The dotted line indicates any one of the first to fourth functions F1 (x) to F4 (x). In addition, each of the five levels of illuminance xn1, xn2,
xn3, xn4, and xn5 are set, and respective luminances yc1, yc2, yc3, yc4, and yc5 corresponding to the respective illuminances are shown.
The intervals between the illuminances xn1 to xn5 are made narrower as the illuminance increases. This is because the higher the illuminance is, the lower the detection sensitivity of the optical sensor 10 is, so that the responsiveness of the automatic adjustment of the brightness of the display screen on the high illuminance side is improved. Further, the intervals between the illuminances xn1 to xn5 are determined by the first to fourth functions F1
(x) to F4 (x), the first function F1 (x) is the narrowest, the second function F2 (x) is slightly wider, the third function F3 (x) is wider, and the fourth function F4 (x) x) is the widest.

The illuminances xn1 to xn5 set for the first to fourth functions F1 (x) to F4 (x) are stored in the memory of the display control unit 2.

Here, for example, the luminance y of the backlight 11
Is set to the luminance yc2, the luminance y of the backlight 11 is not increased to the luminance yc3 unless the illuminance x detected by the optical sensor 10 reaches xn3, and the illuminance x detected by the optical sensor 10 Unless is lower than xn1, the luminance y of the backlight 11 is not reduced to the luminance yc1. When the illuminance x detected by the optical sensor 10 reaches xn3, the first to fourth functions F1 (x) to F4
(x), luminance yc corresponding to illuminance xn3
3 is obtained, and the luminance y of the backlight 11 is increased to the luminance yc3. Then, once the luminance y is increased, the luminance y of the backlight 11 is not reduced to the luminance yc2 unless the illuminance x detected by the optical sensor 10 becomes lower than xn2. Similarly, when the illuminance x detected by the optical sensor 10 becomes lower than xn1, the luminance yc1 corresponding to the illuminance xn1 is obtained based on one of the first to fourth functions F1 (x) to F4 (x). As a result, the luminance y of the backlight 11 is reduced to the luminance yc1. Then, once the luminance y is reduced, the luminance y of the backlight 11 is not increased to the luminance yc2 unless the illuminance x detected by the optical sensor 10 reaches xn2.

The brightness of the display screen of the color liquid crystal panel 12 is stabilized by such a stepwise change of the luminance y of the backlight 11 and the hysteresis characteristic.

FIG. 5 is a flowchart showing a process for obtaining the luminance y of the backlight 11 in the liquid crystal display device of the present embodiment.

Here, when the power supply of the liquid crystal display device is first turned on, the display control unit 2 reads out the first function F1 (x) = a + b1 from the memory and performs an initial setting (step S1). Thereafter, the display control unit 2 determines whether or not the setting of the function has been instructed by the operation of the operation unit 3 (step S2). If not (“No” in step S2), the process proceeds to step S11. Move on.

When the function selection is set ("Yes" in step S2), the bar symbol 21 is displayed on the display screen of the color liquid crystal panel 12 by the OSD circuit 7 as described above, and the operation unit is operated. After the length of the bar symbol 2 is adjusted by the operator 3, the selection of a function is instructed by operating the operation unit 3, and the flags F1 to F4 indicating the first to fourth functions F1 (x) to F4 (x) are selected. Either one is instructed to the display control unit 2. The display control unit 2 controls each of the flags F1 to
One of the first to fourth functions F1 (x) to F4 (x) is selected and set depending on which of F4 is instructed. That is, when the flag F1 is designated ("Yes" in step S3), the display control unit 2 sets the first function F1 (x) = a + b1 corresponding to the flag F1 (step S3).
4), proceed to step S11. If the flag F1 is not designated ("No" in step S3) and the flag F2 is designated ("Yes" in step S5), the complement b2 is substituted into the complement b1 of the first function F1 (x) = a + b1. By doing so, the second function F2 (x) = a + corresponding to the flag F2
After setting b2 (step S6), step S11
Move on to Similarly, when the flag F3 is instructed ("Yes" in step S7), a second function F3 (x) = a + b3 corresponding to the flag F3 is set (step S9).
The process proceeds to step S11, and when the flag F4 is designated ("No" in step S7), the second function F4 (x) = a + b4 corresponding to the flag F4 is set (step S10), and then the process proceeds to step S11. .

In step S11, the display control unit 2 determines the illuminance x of the surroundings detected by the optical sensor 10.
Through the A / D converter 8. Then, the display control unit 2 obtains the luminance y corresponding to the surrounding illuminance x based on the function set previously and the hysteresis characteristic shown in the graph of FIG. 4 (step S12), and the luminance adjustment circuit 5 and the inverter circuit By controlling the backlight 11 through 4, the backlight 11 emits light at this luminance y (step S13).

FIG. 6 is a flowchart showing the processing of steps S11 and S12 in FIG. 5 in more detail.

First, the display control unit 2 includes the optical sensor 1
When the peripheral illuminance x detected by 0 is fetched, the illuminance x is replaced with the illuminance xi (step S30), and it is determined whether or not the detected illuminance xi is equal to or greater than the reference illuminance xN (step S31). Further, the display control unit 2 controls the illuminances xn1 to xn5 in five stages of the function set previously.
Is read from the memory. The reference illuminance xN is set when the processing of the flowchart in FIG. 6 has been performed before, and is set to an initial value when the power of the liquid crystal display device is turned on.

If the detected illuminance xi is equal to or greater than the reference illuminance xN ("Yes" in step S31), the illuminance in the surrounding area is higher than before. In this case, the display control unit 2 compares the detected illuminance xi with each of the illuminances xn2 to xn5 of the previously set function (steps S32, S33,
S34, S35). If the detected illuminance xi is less than the illuminance xn2 ("No" in step S32), the illuminance xn1 is substituted for the reference illuminance xN (step S40). Similarly, if the detected illuminance xi is less than the illuminance xn3 ("No" in step S33), the illuminance xn2 is substituted for the reference illuminance xN (step S39), and if the detected illuminance xi is less than the illuminance xn4. ("No" in step S34), the illuminance xn3 is substituted for the reference illuminance xN (step S38), and if the detected illuminance xi is less than the illuminance xn5 (step S3).
5, "No"), the illuminance xn4 is substituted for the reference illuminance xN (step S37). If the detected illuminance xi is equal to or greater than the illuminance xn5 ("Yes" in step S35), the illuminance xn5 is substituted for the reference illuminance xN. (Step S36).

The detected illuminance xi is equal to the reference illuminance xN.
If it is less than (“No” in step S31), the surrounding illuminance is lower than before. In this case, the display control unit 2 compares the detected illuminance xi with the illuminances xn1 to xn4 of the previously set function (steps S41 and S4).
2, S43, S44). If the detected illuminance xi is equal to or greater than the illuminance xn4 ("No" in step S41),
The illuminance xn5 is substituted for the reference illuminance xN (step S3).
6). Similarly, if the detected illuminance xi is equal to or greater than the illuminance xn3 ("No" in step S42), the illuminance xn4 is substituted for the reference illuminance xN (step S39), and the detected illuminance xn
If i is equal to or greater than the illuminance xn2 (“N” in step S43)
o "), and substitute the illuminance xn3 for the reference illuminance xN (step S).
38) If the detected illuminance xi is equal to or greater than the illuminance xn1 ("No" in step S44), the illuminance xn2 is referred to as the reference illuminance x
N (step S39), and if the detected illuminance xi is less than the illuminance xn1 ("Ye" in step S44).
s "), and substitute the illuminance xn1 for the reference illuminance xN (step S40).

After setting the reference illuminance xN in this way, the luminance y of the backlight 11 is obtained by substituting the reference illuminance xN into the previously set function (step S46).

For example, if the previous reference illuminance xN corresponds to the illuminance xn2, and the luminance y of the backlight 11 has already been set to the luminance yc2, the detected illuminance xi does not reach xn3 (step S33). "No"), the previous reference illuminance xN is maintained (step S39), and the backlight 1
1 is maintained at the luminance yc2 (step S4).
6). When the detected illuminance xi reaches xn3 ("Yes" in step S33, "N" in step S34).
o "), the illuminance xn3 is substituted for the reference illuminance xN (step S38), and the luminance y of the backlight 11 is increased to the luminance yc3 (step S46). Further, once the luminance y is increased, if the detected illuminance xi is not lower than xn2 ("No" in step S43), the reference illuminance xN corresponding to the illuminance xn3 is maintained (step S38), The luminance y of the light 11 is maintained at the luminance yc3 (step S46). Then, when the detected illuminance xi becomes lower than xn2 ("Yes" in step S43, step S4).
4, "No"), the illuminance xn2 is substituted for the reference illuminance xN (step S39), and the luminance y of the backlight 11 is reduced to the luminance yc2 (step S46).

As described above, in the liquid crystal display device of the present embodiment,
By operating the operation unit 3, the first to fourth functions F1
One of (x) to F4 (x) is selectively set, and the luminance y of the backlight 11 is adjusted based on the set function. That is, the relationship between the surrounding illuminance and the luminance y of the backlight 11 can be changed depending on which function is selected. For this reason, it is possible to automatically adjust the luminance y of the backlight 11 according to various personal preferences. In addition, due to the stepwise change of the luminance y of the backlight 11 and the hysteresis characteristic, the color liquid crystal panel 12
The brightness of the display screen is stabilized.

It should be noted that if the cycle at which the processing of the flowchart shown in FIG.
Of the display screen can be prevented, and the brightness of the display screen can be further stabilized. The color liquid crystal panel 12
By changing the cycle in accordance with the frequency of updating the data on the display screen and the frequency of operation input of the operation unit 3, when there is no data update or operation input, the brightness of the display screen is automatically adjusted. The response speed may be slow.

Next, a second embodiment of the automatic light control method of the present invention will be described with reference to FIGS. 7, 8 and 9.
The method of the present embodiment is applied to the liquid crystal display of FIG. In the present embodiment, a plurality of saturation luminances are set in advance, and one of the saturation luminances is selected. Then, the brightness obtained based on the function is limited by the selected saturation brightness, thereby limiting the maximum brightness of the backlight 11.

In the graph of FIG. 7, a predetermined function F for obtaining the luminance y of the backlight 11 using the surrounding illuminance x detected by the optical sensor 10 as a variable is shown.
(x) = a + b, first to fourth saturation luminances y1, y2, y3
, Y4, and first to fourth illuminances L1, L2, L3, L4 corresponding to the respective saturation luminances are shown. The first saturation luminance y1 is the maximum luminance of the backlight 11 (200 c
d / m ² ).

When any one of the saturation luminances y1 to y4 is selected, the operation unit 3 is operated to instruct the display control unit 2 to select the saturation luminance. In response, the display control unit 2 activates the OSD circuit 7,
The bar symbol 21 shown in FIG. 3 is displayed on the display screen of the color liquid crystal panel 12 by the OSD circuit 7. Each range m1 to m4 of the length of the bar symbol 21 corresponds to the first to fourth saturation luminances y1 to y4. The OSD circuit 7 reduces or expands the bar symbol 21 on the display screen of the color liquid crystal panel 12 in response to the operation of the operation unit 3. If the length of the bar symbol 21 is appropriately adjusted and then the operation unit 3 is further operated to instruct selection of a function, the length of the bar symbol 21 falls within any of the ranges m1 to m4. One of the flags F1 to F4 indicating the first to fourth saturation luminances y1 to y4 is instructed to the display control unit 2.

That is, the length of the bar symbol 21 corresponds to the brightness of the display screen of the color liquid crystal panel 12, and according to this brightness, the first to fourth saturation luminances y1 to y1.
y4 is selected.

Further, based on the function F (x) = a + b, not only is the luminance y of the backlight 11 corresponding to the surrounding illuminance x obtained, but also as shown in the graph of FIG. Is changed stepwise and with a hysteresis characteristic.

FIG. 8 is a flowchart showing a process for obtaining the luminance y of the backlight 11 in the liquid crystal display device of the present embodiment.

First, when the power of the liquid crystal display device is turned on, the display control unit 2 reads and sets the function F (x) = a + b and the identifier SAT1 of the first saturation luminance y1 from the memory (step S101). Thereafter, the display control unit 2 determines whether or not the setting of the saturation luminance has been instructed by the operation of the operation unit 3 (step S102). If it has not been instructed (“No” in step S102), the process proceeds to step S111. And move.

When the setting of the saturation luminance is instructed (“Yes” in step S 102), the bar symbol 21 is displayed on the display screen of the color liquid crystal panel 12 as described above, and After the length of the symbol 2 is adjusted, the selection of the saturation luminance is instructed by operating the operation unit 3, and one of the flags F1 to F4 indicating the first to fourth saturation luminances y1 to y4 is displayed by the display control unit 2. Is instructed. For example, when the flag F1 is instructed ("Yes" in step S103), the display control unit 2 sets the identifier SAT1 of the first saturation luminance y1 corresponding to the flag F1 (step S104), and proceeds to step S111. . Also, the flag F1 is not designated (step S10).
If the flag F2 is designated ("Yes" in step S105), the identifier of the second saturation luminance y2 is determined.
After setting SAT2 (step S106), step S106
Move to 111. Similarly, when the flag F3 is instructed ("Yes" in step S107), the identifier SAT3 of the third saturation luminance y3 corresponding to the flag F3 is set (step S109), and the process proceeds to step S111. Is instructed (“N” in step S107).
o "), the identifier SAT4 of the fourth saturation luminance y4 corresponding to the flag F4 is set (step S110), and the process proceeds to step S111.

In step S111, the display control unit 2 takes in the surrounding illuminance x detected by the optical sensor 10. Then, the display control unit 2 selects an illuminance corresponding to the saturated luminance from the first to fourth illuminances L1, L2, L3, L4 based on the previously set identifier of the saturated luminance. The lower one of the detected illuminance and the detected illuminance is selected, and the function F (x) = a + b and FIG.
The luminance y corresponding to the lower illuminance is obtained based on the hysteresis characteristics shown in the graph (step S11).
2) By controlling the backlight 11 through the luminance adjustment circuit 5 and the inverter circuit 4, the backlight 11 emits light at this luminance y (step S113).

FIG. 9 shows steps S111 and S11 in FIG.
3 is a flowchart illustrating the process of FIG. still,
In FIG. 9, steps S30 to S44 are the same as steps S30 to S44 in FIG.

First, in steps S30 to S44, the reference illuminance xN is obtained as described above. Thereafter, the display control unit 2 determines that the previously set saturation luminance identifier is SAT1.
Is determined (step S45), and the identifier SAT1 is determined.
If (Yes in step S45), the function F (x)
= A + b and the hysteresis characteristic shown in the graph of FIG. 4 to determine the luminance y corresponding to the detected peripheral illuminance xi (step S46).

In addition, instead of the identifier SAT1 (step S45)
Is "No"), if it is the identifier SAT2 ("Yes" in step S47), the detected surrounding illuminance xi is the identifier SAT2
It is determined whether or not the second illuminance is larger than the second illuminance L2 corresponding to the saturation luminance (step S48). If it is larger ("Yes" in step S48), the second illuminance L2 is substituted for the peripheral illuminance xi (step S49), and the luminance y corresponding to the peripheral illuminance xi is obtained (step S46).
If it is not large ("No" in step S48), step S49 is omitted, and the luminance y corresponding to the detected peripheral illuminance xi is obtained (step S46).

Further, instead of the identifier SAT2 (step S47)
Is "No"), if it is the identifier SAT3 ("Yes" in step S50), the detected surrounding illuminance xi is the identifier SAT3
It is determined whether the illuminance is higher than the third illuminance L3 corresponding to the saturation luminance (step S51).
("Yes" at 51), the third illuminance L3 is substituted for the peripheral illuminance xi (step S52), and the luminance y corresponding to the peripheral illuminance xi is obtained (step S46). "No"), Step S52
Is omitted, and the luminance y corresponding to the detected surrounding illuminance xi is obtained (step S46).

If it is not the identifier SAT3 (step S
Since the identifier SAT4 remains, it is determined whether the detected surrounding illuminance xi is greater than the fourth illuminance L4 corresponding to the saturation luminance of the identifier SAT4 (step S53). If it is larger ("Ye" in step S53)
s "), the fourth illuminance L4 is substituted for the peripheral illuminance xi (step S54), and the luminance y corresponding to the peripheral illuminance xi is obtained.
(Step S46), and if not large ("No" in step S53), step S54 is omitted, and
The luminance y corresponding to the detected surrounding illuminance xi is obtained (step S46).

As described above, in the present embodiment, the first to fourth illuminances L 1 and L 2 are determined based on the set saturation luminance identifier.
, L3, L4, the illuminance corresponding to the saturation luminance is selected, and the lower one of the selected illuminance and the detected illuminance is selected, and the function F (x) = a + b and the graph of FIG. The luminance y corresponding to the lower illuminance is obtained based on the hysteresis characteristics shown. Therefore, the luminance y of the backlight 11 does not exceed the set saturation luminance.

If the cycle at which the processing of the flowchart shown in FIG. 8 is repeated is set as appropriate,
Frequent change of the luminance of the image can be prevented. Further, the cycle may be changed according to the frequency of updating data on the display screen of the color liquid crystal panel 12 or the frequency of operation input of the operation unit 3. Instead of storing the function, a data table in which the illuminance x and the luminance y are associated may be stored.

Next, a third embodiment of the automatic light control method of the present invention will be described with reference to FIGS. The method of the present embodiment is applied to the liquid crystal display of FIG. In the present embodiment, from among the functions corresponding to the plurality of illuminance ranges, a function corresponding to the illuminance range including the detected peripheral illuminance is selected, and based on the selected function,
A luminance corresponding to the detected peripheral illuminance is obtained, and the backlight 11 of the display screen is caused to emit light at this luminance.

In the graph of FIG.
A predetermined function F for obtaining the luminance y of the backlight 11 using the surrounding illuminance x detected as a variable
(x) = {(y2-y0) / (x2-x0)} x + y0,
Any function F1 corresponding to the illuminance range L11 of x0 to x1
(x) and an arbitrary function F2 (x) corresponding to the illuminance range L12 of x1 to x2.

When setting any of the functions F1 (x) and F2 (x), the operation unit 3 is operated to instruct the display control unit 2 to set the luminance. In response, the OSD circuit 7 is activated by the display control unit 2, and the bar symbol 21 shown in FIG. 3 is displayed on the display screen of the color liquid crystal panel 12 by the OSD circuit 7. The length of the bar symbol 21 corresponds to the luminance of the backlight 11. OS
The D circuit 7 reduces or expands the bar symbol 21 on the display screen of the color liquid crystal panel 12 in response to the operation of the operation unit 3. When the function setting is instructed by further adjusting the length of the bar symbol 21 and further operating the operation unit 3, the luminance y corresponding to the length of the bar symbol 21 is instructed to the display control unit 2. You. The display control unit 2 replaces the luminance y with the luminance y1, and replaces the surrounding illuminance x detected by the optical sensor 10 at this time with the illuminance x.
1 and the set reference value (x1,
y1) is set. Then, the display control unit 2 changes the set reference value (x1, y1) from the lower limit reference value (x0, y0).
The function F1 (x) of the following equation (1) leading to the following equation (1) is derived, and the function F2 (x) of the following equation (2) ranging from the set reference value (x1, y1) to the upper limit reference value (x2, y2) is derived. I do.

F1 (x) = {(y1-y0) / (x1-x0)} (x-x0) + y0 (1) F2 (x) = {(y2-y1) / (x2-x1)} (X−x1) + y1 (2) That is, the luminance y corresponding to the length of the bar symbol 21
, And arbitrary functions F1 (x) and F2 (x) are set based on the surrounding illuminance x detected by the optical sensor 10.

FIG. 11 is a flowchart showing a process for obtaining the luminance y of the backlight 11 in the liquid crystal display device of the present embodiment.

First, when the power supply of the liquid crystal display device is turned on, the display control unit 2 reads the lower limit reference values (x0, y0) and the upper limit reference values (x2, y2) preset from the memory.
) Is read. If the set reference value (x1, y1) has already been set, the set reference value (x1
, Y1). Further, the set reference values (x1, y1
) Has not yet been set, the set reference value (x1
, Y1) are regarded as the same as the upper limit reference value (x2, y2) (step S201). Thereafter, the display control unit 2
Determines whether the setting of the luminance is instructed by the operation of the operation unit 3 (step S202). If not ("No" in step S202), the process proceeds to step S207.
Move to

If the setting of the luminance is instructed (“Yes” in step S 202), the bar symbol 21 is displayed on the display screen of the color liquid crystal panel 12 as described above, and the bar symbol is After the length of 2 is adjusted, the setting of the function is instructed by operating the operation unit 3.
In response, the display control unit 2 displays the bar symbol 2
The luminance y corresponding to the length of the optical sensor 10
The illuminance x of the surroundings detected by is acquired (step S203). Then, the display control unit 2 confirms that the detected peripheral illuminance x is less than the upper limit reference value x2 (“Yes” in step S204) and is larger than the lower limit reference value x0 (step S204). In S205, “Y
es "), the luminance y corresponding to the length of the bar symbol 21 is replaced with the luminance y1, the surrounding illuminance x detected by the optical sensor 10 is replaced with the illuminance x1, and the set reference value (x1
, Y1) are set (step S206).

When the peripheral illuminance x detected by the optical sensor 10 is detected after the setting reference values (x1, y1) are set in this way, the display control unit 2 replaces the illuminance x with the illuminance xi ( In step S207, it is determined whether or not the detected surrounding illuminance xi is larger than the set reference value x1 (step S208). If the detected peripheral illuminance xi is larger than x1 ("Yes" in step S208), that is, if the detected peripheral illuminance xi falls within the illuminance range L12 of the graph of FIG. 8, the display control unit 2 Based on the function F2 (x) of the above equation (2) from the set reference value (x1, y1) to the upper limit reference value (x2, y2), the luminance y corresponding to the detected peripheral illuminance xi is obtained ( Step S209). If the detected illuminance xi of the surrounding area is equal to or less than x1 ("N" in step S208).
o "), that is, if the detected surrounding illuminance xi falls within the illuminance range L11 of the graph of FIG. 8, the display control unit 2 changes the lower limit reference value (x0, y0) to the set reference value (x1, y1).
Is determined based on the function F1 (x) of the above equation (1), which corresponds to the detected illuminance xi of the surrounding area (step S).
210).

As described above, the set reference values (x1, y
1) is not set, the set reference value (x1, y1)
) Is considered the same as the upper reference value (x2, y2). In this case, the detected surrounding illuminance xi is determined to be less than or equal to x1 ("No" in step S208), and based on the function F1 (x) of the above equation (1), the detection is performed. The luminance y corresponding to the illuminance xi in the vicinity thus obtained is obtained (step S210).

When the display control unit 2 obtains the luminance y corresponding to the surrounding illuminance xi, the display control unit 2 controls the backlight 11 through the luminance adjustment circuit 5 and the inverter circuit 4 so that the backlight 11 emits light at this luminance y. (Step S211).

As described above, in the liquid crystal display device of the present embodiment,
One of arbitrary functions F1 (x) and F2 (x) is selected depending on which of the detected illuminances xi in the surrounding area falls within each of the illuminance ranges L11 and L12, and based on the selected function. Then, the luminance y corresponding to the detected surrounding illuminance xi is obtained, and the backlight 11 is caused to emit light at this luminance y. For example, in the illuminance range L11, a sufficiently high luminance y is set for the detected peripheral illuminance xi, and in the illuminance range L12, an appropriately low luminance y is set for the detected peripheral illuminance xi. Thereby, the brightness adjustment of the display screen is adapted to the individual sense.

It should be noted that if the cycle at which the processing of the flowchart shown in FIG.
1 can be prevented from frequently changing. Also,
The cycle may be changed according to the frequency of updating data on the display screen of the color liquid crystal panel 12 or the frequency of operation input of the operation unit 3. Furthermore, instead of remembering each function,
Each data table corresponding to each function is stored as a data table in which the illuminance x is associated with the luminance y, and one of these data tables is selected, and the illuminance x is referred to by referring to the selected table. The corresponding luminance y may be obtained.

Next, a fourth embodiment of the automatic light control method of the present invention will be described with reference to FIGS. The method of the present embodiment is applied to the liquid crystal display of FIG. In the present embodiment, each function corresponding to the five illuminance ranges is set, and based on the function corresponding to the illuminance range including the detected peripheral illuminance, the luminance corresponding to the detected peripheral illuminance is calculated. Then, the backlight 11 of the display screen is caused to emit light at this luminance.

In the graph of FIG.
A predetermined function F for obtaining the luminance y of the backlight 11 using the surrounding illuminance x detected as a variable
(x) = {(y5-y0) / (x5-x0)} x + y0,
Also, arbitrary functions F0 (x) to F4 (x) corresponding to the five illuminance ranges L20 to L24 are shown.

When any of the functions F0 (x) to F4 (x) is set, the operation of the operation unit 3 instructs the display control unit 2 to set the luminance, and the bar symbol 21 shown in FIG. When the function is displayed on the display screen of the panel 12 and the length of the bar symbol 21 is appropriately adjusted by operating the operation unit 3, and the operation of the operation unit 3 is further instructed to set a function, the length of the bar symbol 21 is reduced. The corresponding luminance y is instructed to the display control unit 2. The display control unit 2 replaces the luminance y with the luminance yn (n = 0 to 5), and converts the surrounding illuminance x detected by the optical sensor 10 into the illuminance xn (n
= 0 to 5), and a function Fn (x) of the following equation (3) is derived based on six reference values including a lower limit reference value (x0, y0) and an upper limit reference value (x5, y5).

Fn (x) = {(y (n + 1) −yn) / (x (n + 1) −xn)} (x−xn) + yn (1) FIG. 13 shows the liquid crystal of this embodiment. 5 is a flowchart illustrating a process for obtaining a luminance y of the backlight 11 in the display device.

First, when the power of the liquid crystal display device is turned on, the display control unit 2 reads the preset lower limit reference values (x0, y0) and upper limit reference values (x5, y5) from the memory.
) Is read. Further, the first to fourth setting reference values (x1
, Y1) to (x4, y4), the first to fourth setting reference values are read from the memory. Furthermore, if there is a setting reference value that has not yet been set, this setting reference value is regarded as the same as the upper limit reference value (x5, y5) (step S220). Thereafter, the display control unit 2
Determines whether or not the setting of the luminance is instructed by the operation of the operation unit 3 (step S221). If the instruction is not issued (“No” in step S221), the process proceeds to step S233.
Move to

When the setting of the luminance is instructed (“Yes” in step S 221), the bar symbol 21 is displayed on the display screen of the color liquid crystal panel 12 as described above, and the bar symbol is After the length of 2 is adjusted, the setting of the function is instructed by operating the operation unit 3.
In response, the display control unit 2 displays the bar symbol 2
The luminance y corresponding to one length is taken in as luminance yi,
The surrounding illuminance x detected by the optical sensor 10 is represented by illuminance x
i (step S222). Then, the display control unit 2 changes the surrounding illuminance xi to x0, x1,.
2, x3, x4, x5 (each step S22
3, S224, S225, S226, S227, S22
8), the surrounding illuminances xi are represented by x0, x1, x2, x3, x
4 or x5, and x0, x1,.
x2, x3, x4, x5 are updated (each step S22).
9, S230, S231, S232).

For example, if the surrounding illuminance xi is less than x1 ("Yes" in step S227) and equal to or more than the lower limit reference value x0 ("Ye" in step S228).
s "), replacing the existing third setting reference value (x3, y3) with the fourth setting reference value (x4, y4), and replacing the existing second setting reference value (x2, y2) with the third setting reference value (x3 , Y3) and replace the existing first set reference value (x1, y1) with the second
After replacing with the set reference value (x2, y2), the surrounding illuminance xi and luminance yi are substituted for the first set reference value (x1, y1) (step S229). That is, the surrounding illuminance x
When substituting i and luminance yi for the first set reference value (x1, y1), the existing first to third set reference values are moved up to the second to fourth set reference values.

If the surrounding illuminance xi is less than x2 ("Yes" in step S226) and not less than x1 ("No" in step S227), the existing third setting reference values (x3, y3) are set. ) Is the fourth set reference value (x4, y4)
And the existing second setting reference value (x2, y2) is replaced with the third setting reference value (x3, y3), and then the surrounding illuminance xi and luminance yi are changed to the second setting reference value (x2, y2).
(Step S232).

If the surrounding illuminance xi is less than x3 ("Yes" in step S225) and equal to or more than the lower limit reference value x2 ("No" in step S226), the existing third setting reference value is set. After replacing (x3, y3) with the fourth setting reference value (x4, y4), the surrounding illuminance xi and luminance yi are substituted for the third setting reference value (x3, y3) (step S231).

If the peripheral illuminance xi is less than x5 ("Yes" in step S223) and equal to or greater than x3 ("No" in step S225), the peripheral illuminance xi
And the luminance yi are substituted for the fourth setting reference value (x4, y4) (step S230).

Further, if the surrounding illuminance xi is equal to or greater than x5 ("No" in step S223), the reference value is not updated.

Here, the first setting reference value is set with the highest priority, and the second, third, and fourth values are set in the following order.
The first to fourth setting reference values are sequentially set. For example, when only the first set reference value (x1, y1) is set, the second to fourth set reference values are set to the upper limit reference value (x5, y1).
5), and only the illuminance range from the lower reference value x0 to the first setting reference value x1 and the illuminance range from the first setting reference value x1 to the upper reference value x5 are set. Therefore, by sequentially setting the first to fourth setting reference values,
With this, the illuminance range increases sequentially.

When the surrounding illuminance x detected by the optical sensor 10 is detected after the setting reference value is set in this way, the display control unit 2 replaces the illuminance x with the illuminance xi (step S233), and performs the detection. It is determined whether or not the illuminance xi of the surrounding area is larger than the fourth setting reference value x4 (step S234). If the detected peripheral illuminance xi is larger than x4 ("Yes" in step S234), that is, the detected peripheral illuminance xi is calculated as shown in FIG.
In the illuminance range L24 of the graph of FIG. 2, the display control unit 2 calculates the function F4 (x) of the above equation (3) from the fourth set reference value (x4, y4) to the upper limit reference value (x5, y5). Based on this, the luminance y corresponding to the detected surrounding illuminance xi is obtained (step S238). Further, the detected illuminance xi of the surrounding area is equal to or less than x4 (“N” in step S234).
o "), if the detected peripheral illuminance xi is greater than x3 (" Yes "in step S235), that is, if the detected peripheral illuminance xi falls within the illuminance range L23 of the graph of FIG. Based on the function F3 (x) of the above equation (3) from the reference value (x3, y3) to the fourth set reference value (x4, y4), the luminance y corresponding to the detected peripheral illuminance xi is obtained ( Step S239). Similarly, if the detected peripheral illuminance xi falls within the illuminance range L22 of the graph of FIG. 12 ("No" in step S235, "Yes" in step S236), the second set reference value (x2, y2) 3
The function F2 of the above equation (3) leading to the set reference value (x3, y3)
Based on (x), a luminance y corresponding to the detected peripheral illuminance xi is obtained (step S240). If the detected peripheral illuminance xi falls within the illuminance range L21 of the graph of FIG. 12 (step S236). No "and" Ye "in the step S237.
s "), based on the function F1 (x) of the above equation (3) from the first set reference value (x1, y1) to the second set reference value (x2, y2), The corresponding luminance y is obtained (step S241). Further, if the detected peripheral illuminance xi falls within the illuminance range L20 of the graph of FIG. 12 ("No" in step S237), the lower-limit reference values (x0, y0).
) To the first set reference value (x1, y1), the luminance y corresponding to the detected peripheral illuminance xi is obtained based on the function F0 (x) of the above equation (3) (step S242).

As described above, the unset reference value is regarded as the same as the upper limit reference value (x5, y5). Therefore, for example, when the fourth setting reference value (x4, y4) is not set, it is determined that the detected surrounding illuminance xi is equal to or greater than x4 ("N" in step S234).
o "), if the detected peripheral illuminance xi is larger than x3 (" Yes "in step S235), the luminance corresponding to the detected peripheral illuminance xi is determined based on the function F3 (x). y is obtained (step S239).

When the display control unit 2 obtains the luminance y corresponding to the surrounding illuminance xi, the display control unit 2 controls the backlight 11 through the luminance adjustment circuit 5 and the inverter circuit 4 so that the backlight 11 emits light at this luminance y. (Step S243).

As described above, in the liquid crystal display device of the present embodiment,
One of the arbitrary functions Fn (x) is selected depending on which of the detected peripheral illuminances xi falls within each of the illuminance ranges, and the detected peripheral illuminance is determined based on the selected function. The luminance y corresponding to xi is obtained, and the backlight 11 emits light at this luminance. Therefore, if each function is set according to individual preference for each illuminance range, the brightness adjustment of the display screen can be adapted to the individual's sense.

If the cycle at which the processing of the flowchart shown in FIG. 13 is repeated is set appropriately, the backlight 1
1 can be prevented from frequently changing. Also,
The cycle may be changed according to the frequency of updating data on the display screen of the color liquid crystal panel 12 or the frequency of operation input of the operation unit 3. Furthermore, instead of remembering each function,
Each data table corresponding to each function is stored as a data table in which the illuminance x is associated with the luminance y, and one of these data tables is selected, and the illuminance x is referred to by referring to the selected table. The corresponding luminance y may be obtained.

In the present embodiment, each illuminance range is set arbitrarily. However, each illuminance range may be appropriately limited or specified in advance. In the case where each illuminance range is limited, the first to fourth steps in the flowchart of FIG.
The setting range of the setting reference values x1 to x4 is limited, and the first
The fourth to fourth setting reference values x1 to x4 are set within the respective setting ranges. Then, even if one set reference value is updated within the set range, the other set reference values are maintained without being changed.

The present invention is not limited to the above embodiments, but can be variously modified. For example, although only the linear function is illustrated, the luminance corresponding to the illuminance may be obtained based on another type of function. Further, the illuminance range and the luminance range can be set arbitrarily.

[0111]

As described above, according to the present invention, when any one of a plurality of functions is selected, the luminance corresponding to the surrounding illuminance is obtained based on the selected function, and the obtained luminance is used as the luminance. The backlight is emitted. That is, the relationship between the surrounding illuminance and the luminance of the display screen can be changed depending on which function is selected. For this reason, it is possible to automatically adjust the brightness of the display screen according to various personal preferences.

Further, according to the present invention, the luminance displayed on the display screen of the liquid crystal display device is adjusted, and one of the functions is selected according to the luminance. For example, a function for adjusting the luminance of the display screen to a higher level or a function for adjusting the luminance to a lower level with respect to the illuminance around the liquid crystal display device is set in advance, and based on the luminance displayed on the display screen. Then, one of the functions is appropriately selected.

Further, according to the present invention, since the luminance is increased or decreased stepwise and the hysteresis characteristic is provided for the stepwise increase or decrease of the luminance, the luminance of the display screen is stabilized without frequently changing.

According to the present invention, one of a plurality of preset saturation luminances is selected, and the luminance obtained based on the function is limited by the selected saturation luminance.
The maximum brightness of the display screen can be limited according to various personal preferences.

According to the present invention, the luminance displayed on the display screen of the liquid crystal display device is adjusted, and one of the saturation luminances is selected according to the luminance. For example, the saturation luminance for limiting the maximum luminance of the display screen to a high level and the saturation luminance for restricting the luminance to a low level with respect to the illuminance around the liquid crystal display device are set in advance and displayed on the display screen. One of the saturation luminances is appropriately selected based on the luminance.

Further, according to the present invention, a function corresponding to the illuminance range including the peripheral illuminance is selected from the plurality of functions, and the function corresponding to the detected peripheral illuminance is determined based on the selected function. Brightness is determined, and the backlight is illuminated at the determined brightness. For example, by setting in advance a function for adjusting the luminance of the display screen when the illuminance around the liquid crystal display device is high and a function for adjusting the luminance of the display screen when the illuminance is low, the luminance of the display screen can be adjusted. Can be adapted to the individual's senses.

Further, according to the present invention, the luminance of the backlight and the peripheral luminance are designated as reference values for setting a function corresponding to the illuminance range including the peripheral luminance at this time. I want illuminance. For this reason, it is possible to easily set a function according to personal preference by appropriately instructing the luminance of the backlight.

Further, according to the present invention, the illuminance range is increased each time the luminance is instructed. Also, at this time, the designated luminance and the surrounding illuminance can be obtained as reference values for setting the function, so that the illuminance range and the function can be set only by specifying the luminance.

Further, according to the present invention, a plurality of illuminance ranges are set in advance, and one of the illuminance ranges is selected when the luminance is instructed. Also, at this time, the designated luminance and the surrounding illuminance can be obtained as reference values for setting the function, so that each function corresponding to each illuminance range can be determined while appropriately setting each illuminance range. Can be set.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a liquid crystal display device to which a first embodiment of an automatic light control method of the present invention is applied.

FIG. 2 is a graph illustrating characteristics of luminance of a backlight with respect to peripheral illuminance in the first embodiment.

FIG. 3 is a diagram illustrating bar symbols displayed on the display screen of the liquid crystal display device.

FIG. 4 is a graph showing a hysteresis characteristic of a luminance of a backlight with respect to a surrounding illuminance.

FIG. 5 is a flowchart illustrating a process for obtaining the luminance of the backlight in the liquid crystal display device according to the first embodiment.

FIG. 6 is a flowchart showing the processing of steps S11 and S12 in FIG. 5 in more detail;

FIG. 7 is a graph showing a characteristic of a luminance of a backlight with respect to a surrounding illuminance in a second embodiment of the automatic light control method of the present invention.

FIG. 8 is a flowchart illustrating a process for obtaining the luminance of a backlight in the liquid crystal display device according to the second embodiment.

FIG. 9 is a flowchart showing the processing of steps S111 and 112 in FIG. 8 in more detail;

FIG. 10 is a graph showing a characteristic of a luminance of a backlight with respect to a surrounding illuminance in a third embodiment of the automatic light control method of the present invention.

FIG. 11 is a flowchart illustrating a process for obtaining the luminance of a backlight in the liquid crystal display device according to the third embodiment.

FIG. 12 is a graph showing a characteristic of a luminance of a backlight with respect to a surrounding illuminance in a fourth embodiment of the automatic light control method of the present invention.

FIG. 13 is a flowchart showing a process for obtaining the luminance of the backlight in the liquid crystal display device of the fourth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal display unit 2 Display control unit 3 Operation part 4 Inverter circuit 5 Brightness adjustment circuit 6 Display memory 7 OSD circuit 8 A / D converter 9 Interface circuit 10 Optical sensor 11 Backlight 12 Color liquid crystal panel

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) G09G 3/34 G09G 3/34 J 3/36 3/36 F term (Reference) 2H091 FA41Z LA18 2H093 NC24 NC34 NC42 NC49 NC55 ND07 5C006 AF51 AF52 AF54 BB16 BF27 BF38 EA01 FA56 5C080 AA10 BB05 CC03 DD04 EE28 JJ02 JJ05 JJ07

Claims (13)

[Claims] 1. A method for automatically adjusting the brightness of a backlight of a liquid crystal display device, comprising the steps of: detecting an illuminance around the liquid crystal display device; and calculating the brightness using the illuminance around the variable as a variable. A selection step of selecting any of a plurality of functions set in advance, a luminance setting step of obtaining a luminance corresponding to the detected peripheral illuminance based on the selected function, Controlling the brightness of the light to emit light. 2. The method according to claim 1, wherein the selecting step includes displaying the luminance on a display screen of the liquid crystal display device, adjusting the displayed luminance, and selecting one of the functions according to the displayed luminance. 2. The method of claim 1, further comprising the steps of: 3. The brightness setting step includes: comparing the detected illuminance of the surrounding area with each preset level, and increasing or decreasing the brightness stepwise in accordance with the illuminance of each level based on a selected function. 2. The automatic light control method for a liquid crystal display device according to claim 1, wherein a hysteresis characteristic is provided for the stepwise increase and decrease of the luminance. 4. A method for automatically adjusting the brightness of a backlight of a liquid crystal display device, the method comprising the steps of: detecting a illuminance around the liquid crystal display device; And selecting a luminance corresponding to the detected peripheral illuminance based on a preset function for calculating the luminance using the peripheral illuminance as a variable, and determining the luminance based on the selected saturation. An automatic dimming method for a liquid crystal display device, comprising: a luminance setting step of setting a luminance by limiting the luminance; and a luminance adjusting step of causing a backlight to emit light at the set luminance. 5. The selecting step includes a step of displaying the luminance on a display screen of the liquid crystal display device, a step of adjusting the displayed luminance, and selecting one of the saturation luminances according to the displayed luminance. 5. The method according to claim 4, further comprising the step of selecting. 6. The luminance setting step includes: comparing the detected illuminance of the surrounding area with each preset level, and increasing or decreasing the luminance stepwise in accordance with the illuminance of each level based on a selected function. 5. The automatic light control method for a liquid crystal display device according to claim 4, wherein the step of increasing and decreasing the luminance has a hysteresis characteristic. 7. A method for automatically adjusting the brightness of a backlight of a liquid crystal display device, the method comprising the steps of: detecting a illuminance around the liquid crystal display device; A selecting step of selecting a function corresponding to an illuminance range including the detected peripheral illuminance from among respective functions for calculating luminance using the peripheral illuminance as a variable, and detecting based on the selected function A brightness setting step of obtaining a brightness corresponding to the determined surrounding illuminance; and a brightness adjusting step of causing a backlight to emit light at the obtained brightness. 8. An instruction step of instructing the luminance of the backlight, and the instructed luminance and the peripheral illuminance detected when the luminance is instructed correspond to an illuminance range including the detected peripheral illuminance. A function setting step of obtaining a reference value for setting a function to be adjusted. 9. The automatic liquid crystal display device according to claim 8, wherein each time the luminance is specified, an illuminance range including the peripheral illuminance detected when the luminance is specified is increased. Dimming method. 10. An illuminance range including a peripheral illuminance detected when a luminance is designated is selected and set from a plurality of illuminance ranges set in advance. Automatic dimming method for liquid crystal display device. 11. An automatic light control device for a liquid crystal display device for adjusting the luminance of a backlight of the liquid crystal display device, wherein a detecting means for detecting the illuminance around the liquid crystal display device, and the luminance is calculated using the illuminance around the liquid crystal as a variable. Selecting means for selecting any of a plurality of functions set in advance, and comparing the detected illuminance of the surrounding area with each of the preset levels, based on the selected function, and adjusting the luminance of each of the levels. It is characterized by comprising a luminance setting means for increasing and decreasing stepwise in accordance with the illuminance, and having a hysteresis characteristic for the stepwise increase and decrease in luminance, and a luminance adjusting means for emitting a backlight at the required luminance. Automatic light control device for liquid crystal display. 12. An automatic light control device for a liquid crystal display device for adjusting the brightness of a backlight of the liquid crystal display device, wherein: a detecting means for detecting illuminance around the liquid crystal display device; A luminance value corresponding to the detected peripheral illuminance based on a preset function for calculating the luminance using the peripheral illuminance as a variable, and determining the luminance based on the selected saturation. An automatic dimming device for a liquid crystal display device, comprising: a luminance setting unit configured to set the luminance by limiting the luminance; and a luminance adjusting unit configured to emit a backlight at the set luminance. 13. An automatic light control device for a liquid crystal display device for adjusting the brightness of a backlight of the liquid crystal display device, wherein a detecting means for detecting the illuminance around the liquid crystal display device corresponds to a plurality of mutually different illuminance ranges. Selecting means for selecting a function corresponding to an illuminance range including the detected peripheral illuminance from among respective functions for calculating luminance using the peripheral illuminance as a variable; detecting based on the selected function An automatic dimming device for a liquid crystal display device, comprising: a luminance setting unit that obtains a luminance corresponding to the determined surrounding illuminance; and a luminance adjustment unit that causes a backlight to emit light at the obtained luminance.