JPH06308891A - Display device - Google Patents

Abstract

PURPOSE:To provide a display device in which displayed characters and graphics are easily and visually recognized by a user at all times by automatically varying the luminance of a screen in accordance with the intensity of ambient light in the vicinity of the screen. CONSTITUTION:An ambient light receiving section 8 detects the brightness in the vicinity of a display screen 6. A screen luminance operation section 9 calculates a light control screen luminance band so as to secure and maintain a certain visibility of displayed characters and graphics based on the illuminance value in the vicinity of the display screen detected by the section 8. A luminance discrimination section 11 compares and judges the light control screen luminance band calculated by the section 9 with the set value in the past of the illuminance value stored in a storage section 15 and a screen luminance control section 12 controls the light. Thus, a certain visibility is secured considering human eye characteristics under various conditions of illumination environment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a function of automatically controlling the brightness of a display screen according to a change in brightness around the display device, and the user of the display device can be used in various lighting environments. Relates to a display device that makes it easy to visually recognize display characters and figures.

[0002]

2. Description of the Related Art In recent years, display devices applied to personal computers, word processors, terminals of engineering workstations, etc. have come to be used not only in offices but also in houses.

These display devices include cathode ray tubes (CR
T), liquid crystal (LCD), plasma display panel (PDP), electroluminescence (EL), and other light-emitting or non-light-emitting devices are used. These devices are arranged in a plane as a plurality of pixels. It is designed to present a display screen.

In these display devices, the user of the display device adjusts the brightness (luminance) of the display screen stepwise so that the displayed characters and figures are always easy to see in response to various changes in the lighting environment. Alternatively, the brightness of the display screen can be arbitrarily set by operating an adjustment knob or the like that continuously changes the brightness of the display screen.

However, with such means, the user has to continue to set the brightness of the display screen each time so as to cope with changes in the surrounding lighting environment, and often forgets the adjustment operation. However, there are some problems such as that the brightness may be lost and it may take time to set the brightness.

In order to solve these problems, the brightness (illuminance) received light amount detection unit on the front side of the display screen presented to the display device detects the brightness of the display screen according to the detected brightness. A method of automatically adjusting has been proposed (for example, Japanese Patent Application Laid-Open No. 4-20924 and Japanese Utility Model Application Laid-Open No. 4-75).
No. 321, etc.).

FIG. 9 is a principle diagram showing a conventional method. In FIG. 9, 1 is a display screen (using liquid crystal) of a liquid crystal display device used as an example of a display device,
Reference numeral 2 denotes a received light amount detection unit arranged on the side (rear surface) where the display screen 1 is transmitted, 3 is a backlight unit provided on the side where the display screen 1 is transmitted, and 4 is for adjusting the voltage applied to the backlight unit 3. The backlight power supply unit 5 is a processor that controls the backlight power supply unit 4 according to a signal from the received light amount detection unit 2.

In such a structure, the operation is as follows. First, after the transmitted light from the front side of the display screen 1 is received by the received light amount detection unit 2, the processor 5 adjusts the voltage applied to the backlight unit 3 based on the received light amount detection signal S emitted from the received light. The backlight power supply unit 4 is controlled. In accordance with this control operation, the brightness of the backlight unit 3 automatically changes according to the brightness of the front side of the display screen 1.

Conventionally, these automatic control functions are designed to extend the life of the backlight unit 3 of the display device. For example, in the above liquid crystal display device, when the front side or the surroundings are sufficiently bright, the life of the backlight unit 3 is extended by controlling the brightness of the backlight unit 3 to be suppressed. .

[0010]

However, in the above-described conventional display device, when the brightness around the display device becomes bright, the brightness of the backlight unit is controlled to be suppressed, and conversely, when the brightness becomes dark, the backlight unit 3 is controlled. The control is performed so as to increase the brightness, which does not necessarily match the characteristics of the human eye.

For this reason, although the life of the backlight unit 3 is extended and power saving can be achieved, the brightness of the display screen is too low for the user of the display device to make it difficult to see the characters and figures, or conversely. Due to the problem that the brightness of the screen 1 rises too much to give glare, the work efficiency decreases,
There was a problem of complaining of eye strain and promoting a feeling of mental fatigue.

In the light emitting section such as the backlight section 3 in the liquid crystal display device, the amount of light emitted generally decreases with the lapse of usage time. Therefore, even if the screen brightness is set high in advance and sufficient visibility is obtained in the initial state, there is a problem that it becomes difficult to see with the passage of time.

According to the present invention, the visibility of the display screen corresponding to various changes in the lighting environment is evaluated by using the visibility, and the brightness of the display screen is controlled to change the characteristics of the human eye. (EN) A display device capable of ensuring visibility in consideration and presenting characters and figures that are easy for a user to see.

[0014]

In order to achieve the above-mentioned object, a display device of the present invention includes an ambient light receiving portion arranged near a display screen and facing an observer, and the ambient light receiving portion. Ambient light illuminance I shown in equation (1) based on the output signal
Screen brightness calculation unit for calculating the range of the dimming screen brightness L, a brightness level setting unit for setting the screen brightness desired by the user, a storage unit composed of a rewritable storage medium, and the screen brightness calculation unit. And a brightness determination unit that determines the screen brightness value based on the output signals of the brightness level setting unit and the storage unit,
The storage unit includes a screen brightness control unit that adjusts the screen brightness of the display screen based on the output signal from the brightness determination unit, and the storage unit based on the signal from the ambient light receiving unit and the signal from the brightness level setting unit. The memory contents of are rewritten.

18I ^0.139 ≦ L ≦ 53I ^0.113 (1) Further, in the display device of the present invention, the ambient light illuminance I ′ obtained by the signal from the ambient light receiving section and the screen brightness L set by the brightness level setting section. 'And the relations of the equations (2) and (3), the screen luminance value L in the entire area of the ambient light illuminance I in the storage section is rewritten.

LogL ′ − (0.139−0.026a) logI ′ (2) = log (18 + 35a) where a is a coefficient.

L = (18 + 35a) I ^0.139-0.026a (3) Further, in the display device of the present invention, when the signal from the brightness level setting unit is within the range of the value indicated by the screen brightness calculating unit, The brightness determination unit rewrites the stored content in the storage unit corresponding to the signal from the ambient light receiving unit, and if it is not within the range, outputs a signal that suggests a review of the light environment before rewriting the stored content and displays it. It is intended to be announced.

Further, the display device of the present invention is provided with a backlight usage time integration section and a liquid crystal usage time integration section, and the signal from the brightness level setting section sets the upper limit of the range of values indicated by the screen brightness calculation section. If the output signal from the above-mentioned usage time integration unit exceeds the preset life time of the backlight, a signal warning the maintenance of the backlight or liquid crystal before rewriting the stored contents in the storage unit. Is output.

Further, in the display device of the present invention, the relationship between the ambient light illuminance stored in the storage section and the output signal of the ambient light receiving section is stepwise, and the step width is relative to the ambient light illuminance I by the equation (5). The screen brightness L is calculated, and the brightness difference discrimination threshold ΔL with respect to the screen brightness L is calculated by the equation (4), and the screen brightness L is calculated by the expression (6).
Ambient light illuminance I for new screen brightness L
Is calculated and the storage address of the storage unit is determined.

ΔL = 0.05936L {(1.639 / L) ^0.4 +1} ^2.5 (4) L = 18l ^0.139 (5) I = (L / 18) ^7.2 (6)

[0021]

In the above structure, the illuminance value in the vicinity of the display screen detected by the ambient light receiving unit controls the brightness range of the dimming screen to secure and maintain a certain level of visibility of the displayed characters and solid in the screen brightness calculation unit. The brightness determination unit calculates the brightness control screen brightness range calculated by this screen brightness calculation unit and the screen brightness desired by the user, and the brightness level set by the brightness level setting unit and the past setting value stored in the storage unit. The brightness is controlled by the screen brightness controller. As a result, it is possible to secure a certain level of visibility in consideration of the characteristics of the human eye under various lighting environments, and always obtain good visibility in the usage environment.

Further, taking into account the ambient light illuminance I'obtained by the signal from the ambient light receiving section and the screen brightness L'set by the brightness level setting section, the screen brightness value in the entire ambient light illuminance I in the storage section. By rewriting L, it is possible to prevent the screen brightness from extremely changing with respect to a slight change in the ambient light illuminance, and further, the signal from the brightness level setting unit is displayed by the screen brightness calculating unit. If the value is not within the range of values, a signal suggesting that the light environment should be reviewed can be output before rewriting the stored content to notify the user that the screen brightness will not be unnecessarily increased.

Further, in the backlight type liquid crystal display device, it is possible to clearly indicate to the user the time to replace the light source used for the backlight and the liquid crystal, and further, the ambient light illuminance and the ambient light receiving stored in the storage section. The step-by-step relationship with the output signal of the display unit simplifies the screen brightness calculation unit and prevents the screen brightness from changing extremely in response to slight changes in ambient light illuminance. Can be further simplified.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an outline of a display device which is a first embodiment of the present invention. In FIG. 1, 6 is a display screen made of a transmissive liquid crystal element, 7 is a backlight arranged behind the display screen 6 to illuminate the display screen 6, and 8 is a person who uses the display device near the display screen 6. Is an ambient light receiving portion that is arranged toward the front and receives the light (illumination light, natural light, etc.) from the surroundings that illuminates the display screen 6, and is composed of a silicon photodiode having a light receiving surface with luminosity correction and an amplifier. However, the illuminance is received. Although the specific position of the ambient light receiving portion 8 varies depending on the external shape of the display device body, it is desirable to place the ambient light receiving portion 8 at a place where an illuminance value corresponding to the adaptation state of the user's eyes can be obtained.

Further, the time constant of the ambient light receiving portion 8 is set between 10 seconds and 1000 seconds. It has a characteristic of adaptation by the human eye of about 130 seconds (eg, Rushton,
Annual of New York Academy Sciences, Vol. 74, pp. 291-304 (Rushton
(1958), Ann.NYAcad.Sci., Vol.74, p291-304)). If the time constant is longer than this range, the effect of the present invention cannot be fully expected, and if it is short, it sensitively follows subtle changes in the ambient light, resulting in flicker on the displayed screen.

Reference numeral 9 is a screen brightness calculation unit for inputting an illuminance signal from the ambient light receiving unit 8 and calculating the screen brightness region of the display screen 6 based on a function previously set. 10 is a knob operated by the user. The brightness level setting unit 10 inputs the brightness level desired by the user with the or button and outputs a signal having the same brightness level unless the brightness level is input again. It is advisable to provide three or more levels of average level, higher level, and lower level.

Reference numeral 11 denotes a brightness determination unit that determines an optimum value based on the screen brightness range from the screen brightness calculation unit 9 and the brightness level signal from the brightness level setting unit 10. Reference numeral 12 is based on the determination result of the brightness determination unit 11. , A screen brightness control unit that outputs a signal for controlling the brightness (luminance) of the display screen 6 and the backlight 7,
Reference numeral 3 denotes a backlight power supply unit that supplies power to the backlight 7 and receives a signal from the screen brightness control unit 12 to adjust the brightness of the backlight 7.
A liquid crystal driving unit for driving the liquid crystal element used for the above and adjusting the transmittance of the liquid crystal element, and a storage unit 15. The storage unit 15 outputs the stored content at the address corresponding to the signal from the ambient light receiving unit 8 to the brightness determining unit 11, and based on the determination result of the brightness determining unit 11, the ambient light receiving unit 8
The stored content at the address corresponding to the signal from is rewritten.

The operation of the display device configured as described above will be described below. FIG. 2 shows the relationship between the screen illuminance, which is the basic concept of the function incorporated in the screen brightness calculation unit 9, and the screen brightness for ensuring visibility, obtained through experiments and theoretical support. In the experiment, the display screen of characters set under various screen brightness conditions under various screen illuminances was presented to a total of 9 observers aged 24 to 43, and the visibility of the presented screen was Subjective evaluations of glare etc. were made, and further adjustments were made to the state of screen brightness at which the observer judged that the characters were easy to read and was optimal. This was performed in order to obtain the screen brightness for making the displayed characters sufficiently readable by the adjustment method in addition to the subjective evaluation method. The experimental condition is that the screen illuminance is 10,3.
The screen brightness is set to 10 in order to set 5 conditions of 0, 100, 300, and 1000 lx (lux) so that it is difficult to see in a dark environment, easily visible in a bright environment, and dazzling in a relatively dark environment. , 2
It was 0, 40, 80, 160 cd / m ² (candelas per square meter). The subjective evaluation items were 6 items, and each item was evaluated in 7 steps, and the adjustment method was performed at the same screen illuminance as the subjective evaluation.

FIG. 2 shows the results obtained from the experiment.
In Fig. 2, curve A is the screen brightness obtained by the adjustment method.
Is the average result of 9 observers. Upper limit of screen brightness
Hatching surrounded by a curve B shown and a curve C showing a lower limit
The range of is read at the screen brightness obtained by the adjustment method.
Assuming the ease rating is maximized, the screen brightness ±
50% range and maximum readability of 3
Two conditions of screen brightness condition that can obtain an evaluation value of / 4 or more
It is the relationship between screen illuminance and screen brightness obtained from the case. Picture
The screen brightness when the surface illuminance is 10 lx is 40 ± 20 cd /
m², 60 ± 25 cd / m for 100 lx²10,
115 ± 40 cd / m for 001x ²Becomes this
Achieves brightness within the hatching range of curve B and curve C
If so, almost satisfactory visibility can be obtained.

This is because it is always necessary to consider the sensitivity of the human eye when the brightness of the screen is automatically adjusted, and the visibility Vl is currently used to quantitatively evaluate the visibility. The visibility Vl quantitatively represents the visibility (visibility) of the object being viewed. The visibility Vl is compared with the minimum luminance ratio (called a luminance contrast discrimination area Cmin) that can be discriminated by the human eye in the visual environment looking at the object, and what is the luminance contrast C between the target and the background being seen. It is quantified by the ratio of double. That is, the visibility Vl is defined by the ratio (C / Cmin) between the contrast C of the object and the background thereof and the distinguishable contrast limit value Cmin. In this case, the contrast C is the equivalent light curtain luminance value Leq in which the object luminance is Lo, the background luminance is Lb, and the scattered light in the eyeball due to light from other than the object is taken into consideration.
Then, it becomes as shown in Expression (7).

C = | Lb−Lo | / (Leq + Lb) (7) Further, regarding the relationship between Cmin and Lb, a standard human eye as shown in the following equation (8) from the International Commission on Illumination: Characteristics have been reported.

Cmin = 0.05936 {(1.639 / Lb) ^0.4 +1} ^2.5 (8) Therefore, the visibility Vl is as shown in equation (9). Vl = 16.846 {(1.639 / Lb) ^0.4 +1} ^-2.5 xC (9) These equations (7), (8), and (9) are
S, Lighting Handbook, 1984, Reference Edition, Chapter 3 (IES, LIGHTING, HANDOBOOK, 1
984, REFERENCE, VOLUME). When the visibility Vl is calculated based on these equations, the visibility Vl is approximately a constant value (7
10). From this, it is possible to secure a certain level of visibility by performing light control within the hatching range formed by the curve B and the curve C obtained by the experiment in FIG. You can also consider the difference in dimming level depending on your preference.

Further, the screen luminance L in the hatched range can be expressed by the above-mentioned formula (1) than the illuminance I. 18I ^0.139 ≦ L ≦ 53I ^0.113 (1) In the screen brightness calculation unit 9, the function of the formula (1) is calculated once based on the signal from the ambient light receiving unit 8 or stored in advance. The light control range is output to the brightness determination unit 11. Further, in the storage unit 15, as an initial setting, an arbitrary value (for example, a lower limit value) in the range determined based on the expression (1) is stored in the address for the signal from the ambient light receiving unit 8.

The operation of the brightness determining section 11 will be described with reference to FIG. First, the signal Lm from the storage unit 15 is input. Then, the signal from the brightness level setting unit 10 is input. If there is no signal from the brightness level setting unit 10,
That is, in FIG. 3, when “none”, the signal Lm from the storage unit 15 is directly output to the screen brightness control unit 12. In this case, the storage unit 15 is not rewritten. When there is a signal from the brightness level setting unit 10, that is, when “present” in FIG. 3, a signal corresponding to the screen brightness range from the screen brightness calculation unit 9 is input. The brightness value Ld corresponding to the signal from the brightness level setting unit 10 is determined from the screen brightness range. Then, the value Ld is output to the storage unit 15 and the screen brightness control unit 12. In this case, the storage unit 15 replaces only the storage content at the address corresponding to the signal from the ambient light receiving unit 8 with Ld. By the above operation, good visibility can be obtained in the usage environment.

Next, the operation of the second embodiment of the present invention will be described. The structure of the display device is the same as that of the first embodiment. The difference is that all the contents of the storage unit 15 in FIG. 3 are rewritten. This difference in operation will be described with reference to FIG. In FIG. 4, the curve B is the upper limit of the screen brightness, and the curve C is the lower limit of the screen brightness. In the display device of the first embodiment, it is assumed that the curve C is input as the initial setting and the value when the screen illuminance is 50 lx is γ.
Here, under the light environment with the screen illuminance of 50 lx,
It is assumed that a value γ'is set. In this case, the storage unit 15
The curve C is predominant in the stored contents of, and only the value of the screen illuminance 50lx has a value different from the value on the curve C. In the display device thus adjusted, the screen illuminance is 50 l
If x is slightly deviated, there is a problem that the screen brightness changes abruptly. Therefore, the user has to operate the brightness level setting unit 10 every time the light environment with different screen illuminance changes, which is troublesome. In the second embodiment, the curve C ′ having a constant visibility passing through γ ′ in FIG. 4 is interpolated using the equations (2) and (3) shown above for the curve B and the curve C. It is what you ask for.

LogL ′ − (0.139−0.026a) logl ′ = log (18 + 35a) (2) L = (18 + 35a) I ^0.32-0.06a (3) where L ′ is the brightness level setting unit 10. Is a screen brightness value set by, I'is a screen illuminance value measured by the ambient light receiving unit 8 at that time, and a is a coefficient for interpolation.
The coefficient a is determined based on the equation (2), and the screen brightness value L in the entire ambient light illuminance I in the storage unit 15 is determined based on the equation (3).
To obtain a curve C '.

FIG. 5 shows a method of obtaining the coefficient a from the equation (2). In FIG. 5, f (a) = logL '-(0.139-0.026a) logI' ... (10) and g (a) = log (18 + 35a) ... (11). The intersection of these curves, f (a) = g
The point which becomes (a) is calculated | required, and the value of a at that time is a solution of Formula (2). f1 is f (a) when the screen luminance L'is 50 cd / m ² and the screen luminance I'is 100 lx, and at this time, a = 0.26. The screen brightness L'of f2 is 5
F when 0 cd / m ² and screen illuminance I ′ is 300 lx
(A), where a = 0.14. As is clear from the figure, the curve g does not depend on the screen illuminance and screen brightness. By utilizing this property, the solution can be easily obtained, and thus the circuit can be simplified, for example, when the brightness determination unit 11 is configured by an electric circuit.

Next, a third embodiment of the present invention will be described. FIG. 6 is a block diagram showing the outline of the configuration of the display device of the third embodiment. A display superimposing unit 16 superimposes a message on a part of the display of the liquid crystal display screen as to whether or not the light environment is appropriate based on the result from the brightness determining unit 11. The operation of the brightness determination unit 11 utilizes the property that the function g (a) in FIG. 5 is a monotonically increasing function. That is, if f (1)> g (1), the ambient light illuminance is too high to obtain appropriate screen brightness (for example, when a lighting device (not shown) is reflected on the display screen 6). Is shown. In this case, the display superimposing section 16 outputs a message "confirm that there is no reflection of lighting equipment", and the liquid crystal driving section 14 displays it on a part of the display screen 6. It should be noted that this message may be displayed as characters on the edge of the display screen 6, or the message may be displayed as characters, an icon image or the like. Although not shown, it may be transmitted to the user with a light sound,
Any means of transmission may be used.

Next, a fourth embodiment of the present invention will be described. FIG. 7 is a block diagram showing the outline of the configuration of the display device of the fourth embodiment. Reference numeral 17 denotes a backlight usage time integration unit that integrates the usage time of the backlight in the liquid crystal display device and outputs a signal to the display superposition unit 16 only when the preset lifetime of the backlight is exceeded. Reference numeral 18 indicates a display superimposing unit 1 only when the use time of the liquid crystal is integrated and the preset life of the liquid crystal is exceeded.
6 is a liquid crystal use time integration unit that outputs a signal to 6.

Regarding the service life preset in the backlight use time accumulating section 17, when the light source for the back light is a combination of a fluorescent lamp and a reflector, the service life of the backlight is the service life of the fluorescent lamp. This life is 5,000 to 10,000 hours for the cold cathode fluorescent lamp and 2,000 to 5,000 hours for the hot cathode fluorescent lamp, although it depends on the specifications of the lamp and the use environment. This is defined as the value when the amount of emitted light is reduced to 50% of the initial luminous flux. Therefore, if the amount of emitted light may be sufficiently low, it can be used for a period longer than the above life value. Therefore, it is not practicable to judge whether the lifespan has reached the end of the life time by simply integrating the usage time, and it is necessary to determine whether proper screen brightness can be obtained in the lighting environment used. Should be determined from The backlight usage time integration unit 17 presets the lifetime value of the backlight defined as above, integrates the usage time, and displays the signal only when the integration time exceeds the set value. It is output to the superposition unit 16.

Regarding the service life preset in the liquid crystal use time accumulating section 18, the service life of the liquid crystal device is determined by the liquid crystal element itself. This life depends on the type of liquid crystal element and the operating environment, but it is approximately 5000 hours to 10 hours.
It is 000 hours. This is the operating life of the shutter mechanism of the liquid crystal element. The liquid crystal usage time integration unit 18 integrates usage times independently of the backlight usage time integration unit 17, and outputs a signal to the display superposition unit 16 only when the integration time exceeds a preset life. Is.

In the display superimposing section 16, the signal from the brightness level setting section 10 exceeds the upper limit of the range of values shown by the screen brightness calculating section 9, that is, f (1)> g (1), and the backlight. If there is a signal from the usage time integration unit 17 or the liquid crystal usage time integration unit 18, a message indicating "replacement of backlight" or "replacement of liquid crystal" is displayed according to the signal, and the message in the third embodiment is displayed. Display instead of. By doing so, it becomes clear to the user which of the light environment, the backlight, and the liquid crystal should be changed in order to obtain appropriate usage conditions.

Next, a fifth embodiment of the present invention will be described. The present invention relates to addresses in the storage unit 15 of the first and second embodiments of the present invention. The storage content in the storage unit 15 may store the screen brightness value steplessly with respect to the screen illuminance I. However, when recording using a non-volatile memory or the like, the number of addresses should be finite and as small as possible. If so, the device can be simplified. In the fifth embodiment, this address division is performed in steps such that humans do not feel the difference in screen brightness. From equations (7) and (8), the luminance difference discrimination threshold ΔL with respect to the screen luminance L is obtained as shown in equation (4).

ΔL = 0.05936L {(1.639 / L) ^0.4 +1} ^2.5 (4) Further, the left side of the equation (1) yields the equation (5) shown above. L = 18I ^0.139 (5) Equation (8) shows a curve C in FIG. Further, as the inverse function of the equation (5), the equation (6) shown above is obtained.

I = (L / 18) ^7.2 (6) Address division will be described with reference to FIG. Figure 8
Is an example of dividing an address based on the fifth embodiment. Regarding the lower limit I _n of the _nth screen illuminance step,
The n-th screen brightness L _n is calculated using the right side of Expression (5). For this screen brightness L _n , the limit increment at which no brightness difference is felt is found based on equation (4). Step increment Δ
If L _n has a value smaller than the limit increment at which the brightness difference is not felt, it is possible to prevent the user from feeling a change in screen brightness due to a slight change in the light environment. In FIG. 8, half the value calculated from equation (4), which is the limit at which no brightness difference is felt, is set as the increment. (N + 1) th screen luminance L _{n + 1} = L
_{It is} calculated by _n + ΔL _n . The upper limit and the (n + 1) th screen illuminance I _{n + 1} of the lower limit of the n-th screen illuminance I _n is equal, therefore, the (n + 1) th screen illuminance I _{n + 1} by (n + 1) th screen brightness L _{n + 1} It is calculated using the equation (6). By the above operation, it is possible to simplify the calculation unit of the screen brightness and prevent the screen brightness from extremely changing in response to a slight change in the ambient light illuminance.

[0046]

As described above, according to the display device of the present invention, the screen brightness can be automatically controlled under various brightness, and by considering the change of the sensitivity of the human eye,
It is possible to provide a screen in which characters and figures can be easily seen by the user, and thus work efficiency can be improved, eye strain can be reduced, and mental fatigue can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a display device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between screen illuminance and dimming screen brightness, which is a basic concept in a display device according to an embodiment of the present invention.

FIG. 3 is a flowchart showing the operation of the display device according to the embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between screen illuminance and dimming screen brightness, which is a basic concept in a display device according to an embodiment of the present invention.

FIG. 5 is a diagram showing a functional relationship governing basic operations in a display device according to an embodiment of the present invention.

FIG. 6 is a block diagram showing a schematic configuration of a display device according to another embodiment of the present invention.

FIG. 7 is a block diagram showing an outline of a configuration of a display device of still another embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between screen illuminance and dimming screen brightness, which is a basic concept in a display device according to still another embodiment of the present invention.

FIG. 9 is a block diagram showing a schematic configuration of a conventional display device.

[Explanation of symbols]

 6 Display Screen 7 Backlight 8 Ambient Light Receiving Section 9 Screen Brightness Calculation Section 10 Brightness Level Setting Section 11 Brightness Judgment Section 12 Screen Brightness Calculation Section 13 Backlight Power Supply Section 14 Liquid Crystal Driving Section 15 Storage Section 16 Display Superimposition Section 17 Backlight Usage time integration section 18 LCD usage time integration section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuji Takeuchi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. An ambient light receiving portion arranged near the display screen so as to face an observer, and a dimming screen luminance with respect to an ambient light illuminance I shown in (first expression) based on an output signal of the ambient light receiving portion. A screen brightness calculation unit that calculates the range of L, a brightness level setting unit that sets the screen brightness that the user likes, a storage unit that is composed of a rewritable storage medium, the screen brightness calculation unit and the brightness level setting unit. A brightness determining unit that determines a screen brightness value based on the output signal of the storage unit and a storage unit, and a screen brightness control unit that adjusts the screen brightness of the display screen based on the output signal from the brightness determining unit. A display device, wherein stored contents of the storage unit are rewritten based on a signal from a light receiving unit and a signal from a brightness determination unit. (Formula 1) 18I ^0.139 ≤ L ≤ 53I ^0.113 2. The relationship between the ambient light illuminance I'obtained by the signal from the ambient light receiving section, the screen brightness L'set by the brightness level setting section, and (2nd expression) and (3rd expression). 2. The display device according to claim 1, wherein the screen brightness value L over the entire ambient light illuminance I in the storage unit is rewritten. (Formula 2) logL '-(0.139-0.026a) logI' = log (18 + 35a) (Formula 3) L = (18 + 35a) I ^0.139-0.026a where a is a coefficient. 3. When the signal from the brightness level setting unit is within the range of the value indicated by the screen brightness calculating unit, the brightness determining unit rewrites the stored content in the storage unit corresponding to the signal from the ambient light receiving unit. 3. The display superimposing section for outputting a signal indicating a review of the light environment before rewriting the stored content when the value is not within the range is provided on the output side of the brightness determining section. Display device described. 4. The display screen is a liquid crystal, and a backlight integration unit for integrating the usage time of a backlight for illuminating the liquid crystal and a liquid crystal usage time integration unit for integrating the usage time of the liquid crystal are provided. When the signal from the setting section exceeds the upper limit of the range of values indicated by the screen brightness calculation section, and the output signal from any of the usage time integration sections exceeds the preset lifetime of the backlight. Is
4. The display device according to claim 3, wherein a signal warning the maintenance of the backlight or the liquid crystal of the display screen is output to the display superimposing unit before rewriting the stored contents in the storage unit. 5. The relationship between the ambient light illuminance stored in the storage unit and the output signal of the ambient light receiving unit is stepwise, and the step width is calculated by (Equation 5) to calculate the screen luminance L with respect to the ambient light illuminance I. , (4th formula) to calculate the luminance difference discrimination threshold ΔL with respect to the screen luminance L, and (6th formula) to add the luminance difference discrimination threshold ΔL to the screen luminance L to obtain a new ambient light illuminance I for the new screen luminance L. The display device according to claim 1 or 2, wherein the storage address of the storage unit is determined by calculating. (Formula 4) ΔL = 0.05936L {(1.639 / L) ^0.4 +
1} ^2.5 (5th formula) L = 181 ^0.139 (6th formula) I = (L / 18) ^7.2