Electrooptic device, driving circuit, and electronic device

• US 20070188439A1
• Filed: 01/09/2007
• Published: 08/16/2007
• Est. Priority Date: 02/16/2006
• Status: Active Grant

• Current Assignee: Epson Imaging Devices Corporation (Seiko Group)
• Original Assignee: Sanyo Epson Imaging Devices Corporation (Seiko Group)
• Inventors: Kimura, Fusashi, Tsuda, Atsunari, Takahashi, Masaki
• Granted Patent: US 8,018,450 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: G09G 2300/0456 with a reflective area and a transmissive area combined in one pixel, such as in transflectance pixels
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

An electrooptic device includes: a display panel; an illuminating unit that emits light onto the display panel; an ambient-light measuring unit that measures the illuminance of ambient light; a luminance control unit including a light control profile for obtaining the optimum surface luminance of the display panel, the luminance control unit obtaining the optimum surface luminance on the basis of the measured illuminance of the ambient light using the light control profile, and controlling the luminance of the light to be emitted from the illuminating unit to provide the display panel with the optimum surface luminance; a display-mode switching unit that switches the display panel to a transmission display mode when the illuminance of the ambient light measured by the ambient-light measuring unit is lower than a predetermined illuminance, and switches the display panel to a reflection display mode when the illuminance of the ambient light is higher than the predetermined illuminance; and a storage unit that stores a gamma value for the transmission display for the transmission display mode and a gamma value for the reflection display for the reflection display mode as a plurality of tables. When the display panel is switched to the transmission display mode by the display-mode switching unit, the gamma value for the transmission display is obtained from the plurality of tables stored in the storage unit, and the gamma value for the transmission display is applied. When the display panel is switched to the reflection display mode by the display-mode switching unit, the gamma value for the reflection display is obtained from the plurality of tables stored in the storage unit, and the gamma value for the reflection display is applied.

Claims

1. An electrooptic device comprising:

a display panel;

an illuminating unit that emits light onto the display panel;

an ambient-light measuring unit that measures the illuminance of ambient light;

a luminance control unit including a light control profile for obtaining the optimum surface luminance of the display panel, the luminance control unit obtaining the optimum surface luminance on the basis of the measured illuminance of the ambient light using the light control profile, and controlling the luminance of the light to be emitted from the illuminating unit to provide the display panel with the optimum surface luminance;

a display-mode switching unit that switches the display panel to a transmission display mode when the illuminance of the ambient light measured by the ambient-light measuring unit is lower than a predetermined illuminance, and switches the display panel to a reflection display mode when the illuminance of the ambient light is higher than the predetermined illuminance; and

a storage unit that stores a gamma value for the transmission display for the transmission display mode and a gamma value for the reflection display for the reflection display mode as a plurality of tables;

wherein when the display panel is switched to the transmission display mode by the display-mode switching unit, the gamma value for the transmission display is obtained from the plurality of tables stored in the storage unit, and the gamma value for the transmission display is applied;

when the display panel is switched to the reflection display mode by the display-mode switching unit, the gamma value for the reflection display is obtained from the plurality of tables stored in the storage unit, and the gamma value for the reflection display is applied.

2. The electrooptic device according to claim 1, wherein:

when the illuminance of the ambient light measured by the ambient-light measuring unit is 1,000 1×

or lower, the display-mode switching unit switches the display panel to the transmission display mode, and when the illuminance of the ambient light is higher than 1,000 1×

, the display-mode switching unit switches the display panel to the reflection display mode; and

the predetermined illuminance is 1,000 1×

.

3. The electrooptic device according to claim 1, wherein:

the storage unit includes a plurality of tables in which the relationship between the logarithm of the illuminance of the ambient light and the contrast of the display panel is stored for each luminance of the light of the illuminating unit; and

the luminance control unit obtains a table for setting the display panel to a predetermined contrast from the plurality of tables stored in the storage unit so as to provide the display panel with the predetermined contrast, and controls the luminance of the light of the illuminating unit according to the table.

4. The electrooptic device according to claim 1, wherein:

the storage unit has a plurality of tables in which the relationship between the logarithm of the illuminance of the ambient light and the color reproduction range based on an NTSC standard ratio of the display panel is stored for each luminance of the light of the illuminating unit; and

the luminance control unit obtains a table for setting the display panel to a predetermined color reproduction range based on an NTSC standard ratio from the plurality of tables stored in the storage unit so as to provide the display panel with the color reproduction range based on the NTSC standard ratio, and controls the luminance of the light of the illuminating unit according to the table.

5. The electrooptic device according to claim 1, wherein:

the illuminating unit includes a plurality of light sources having semiconductor light-emitting elements that emit three or more colors of light, respectively;

the electrooptic device further includes a photosensor disposed in the position to detect mixed light generated by the plurality of light sources of the illuminating unit, the photosensor detecting the mixed light and conducting spectral analysis of it to thereby calculate the luminances of the light sources; and

the luminance control unit includes a driving unit that supplies current to the plurality of light sources, and regulates the white balance of the display panel by controlling the current to be supplied to a light source that emits a predetermined color of light out of the light sources.

6. The electrooptic device according to claim 1, wherein

the light control profile has the relationship in which the optimum surface luminance forms a concave quadratic curve with respect to the logarithm of the illuminance of the ambient light, and provided that the illuminance of the ambient light when the luminance of the light incident on the display panel and reflected in the display panel and exits from the display panel and the luminance of the light emitted from the illuminating unit and transmitted through the display panel are equal to each other is the maximum illuminance environment, the optimum surface luminance becomes the maximum under the maximum illuminance environment, and the maximum value of the optimum surface luminance becomes 90% or more of the maximum luminance of the display panel.

7. The electrooptic device according to claim 1, wherein the maximum value of the optimum surface luminance is the maximum luminance of the display panel.

8. The electrooptic device according to claim 1, wherein provided that the illuminance of the ambient light when the luminances of the reflected light and transmitted light from the display panel are equal to each other is 8,000 1×

or higher, the maximum illuminance environment is set to 8,000 1×

.

9. The electrooptic device according to claim 1, wherein when the illuminance of the ambient light measured by the ambient-light measuring unit becomes higher than the maximum illuminance environment, the luminance control unit stops the light emission to the display panel by the illuminating unit.

10. An electronic device comprising an electrooptic device according to claim 1 applied to a display.

11. The electronic device according to claim 10, comprising:

a light-emitting section other than the illuminating unit;

wherein the luminance control unit has a light control profile for obtaining the optimum surface luminance of the light-emitting section, the luminance control unit obtaining the optimum surface luminance on the basis of the illuminance of the ambient light measured by the ambient-light measuring unit using the light control profile, and controlling the luminance of the light-emitting section to provide the light-emitting section with the optimum surface luminance.

12. A driving circuit that automatically controls the light of an illuminating unit that emits light onto a display panel, the driving circuit comprising:

an ambient-light measuring unit that measures the illuminance of ambient light;

a luminance control unit including a light control profile for obtaining the optimum surface luminance of the display panel, the luminance control unit obtaining the optimum surface luminance on the basis of the measured illuminance of the ambient light using the light control profile, and controlling the luminance of the illuminating unit to provide the display panel with the optimum surface luminance;

a display-mode switching unit that switches the display panel to a transmission display mode when the illuminance of the ambient light measured by the ambient-light measuring unit is lower than a predetermined illuminance, and switches the display panel to a reflection display mode when the illuminance of the ambient light is higher than the predetermined illuminance; and

a storage unit that stores a gamma value for the transmission display for the transmission display mode and a gamma value for the reflection display for the reflection display mode as a plurality of tables;

wherein when the display panel is switched to the transmission display mode by the display-mode switching unit, the gamma value for the transmission display is obtained from the plurality of tables stored in the storage unit, and the gamma value for the transmission display is applied;

when the display panel is switched to the reflection display mode by the display-mode switching unit, the gamma value for the reflection display is obtained from the plurality of tables stored in the storage unit, and the gamma value for the reflection display is applied.