DISPLAY UNIT

• US 20090085854A1
• Filed: 08/15/2008
• Published: 04/02/2009
• Est. Priority Date: 09/28/2007
• Status: Active Grant

• Current Assignee: Japan Display West Incorporated (Japan Display Incorporated)
• Original Assignee: Epson Imaging Devices Corporation (Seiko Group)
• Inventors: YASUMORI, Masanori, YAMAZAKI, Yasushi, SATO, Takashi, KUNIMORI, Takashi
• Granted Patent: US 8,217,927 B2
• Time in Patent Office: Days
• US Class Current: 345/92
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• 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

Abstract

The invention provides a display unit that has a display area and first and second photodetectors 10a and 10b on a substrate and outputs as a light intensity signal S a light intensity detected by the first and second photodetectors 10a and 10b. The first photodetector 10a includes a first photodetection circuit LS1 outputting a first output signal Sa to an ambient light photosensor reader 20, and the second photodetector 10b includes a light-reducing unit and a second photodetection circuit LS2 outputting a second output signal Sb to an ambient light photosensor reader 20. The ambient light photosensor reader 20 includes a photodegradation factor calculator 21 calculating a photodegradation reparation factor K, a photodegradation rate calculator 22 deriving a photodegradation rate D based on the photodegradation reparation factor K, and a light signal output unit 24 outputting a light intensity signal S based on the photodegradation rate D.

Claims

1. A display unit that has a display area having a switching element for each pixel on a substrate, the display unit comprising:

a light intensity detector that includes a first photodetector having a first ambient light photosensor, a second photodetector having a second ambient light photosensor, and an ambient light photosensor reader, and outputs as a light intensity signal a light intensity detected by the first photodetector and the second photodetector; and

a light-reducing unit formed in a region that overlies at least one of the first ambient light photosensor and the second ambient light photosensor in a plane view, and differentiates the amount of incident light on the first ambient light photosensor and the second ambient light photosensor;

the first photodetector including a first photodetection circuit that outputs a first output signal based on incident light entering the first ambient light photosensor to the ambient light photosensor reader;

the second photodetector including a second photodetection circuit that outputs a second output signal based on incident light entering the second ambient light photosensor to the ambient light photosensor reader; and

the ambient light photosensor reader including;

a photodegradation factor calculator that calculates a measurement ratio that is a ratio between the first output signal and the second output signal, and calculates a photodegradation reparation factor that is a ratio between the above measurement ratio and an initial ratio that is the measurement ratio obtained in a prearranged initial state;

a photodegradation rate calculator that derives a photodegradation rate of the first or second output signal based on the photodegradation reparation factor; and

a light signal output unit that compensates and outputs the first or second output signal to be a light intensity signal in an initial state based on the photodegradation rate.

2. The display unit according to claim 1, further comprising:

a first light-reducing unit that reduces the amount of light incident on the first ambient light photosensor; and

a second light-reducing unit that reduces the amount of light incident on the second ambient light photosensor;

wherein

a reduction rate of incident light by the second light-reducing unit is larger than a reduction rate of incident light by the first light-reducing unit.

3. The display unit according to claim 2, wherein

the first light-reducing unit and the second light-reducing unit have a same relative spectral transmittance.

4. The display unit according to claim 1, wherein

the light-reducing unit includes a light-blocking component that blocks a part of light incident on the first ambient light photosensor or the second ambient light photosensor.

5. The display unit according to claim 4, wherein

the light-reducing unit includes a light-reducing component that reduces light incident on the first ambient light photosensor or the second ambient light photosensor, and the light-blocking component.

6. The display unit according to claim 1, wherein

the photodegradation rate calculator includes a lookup table that associates the photodegradation reparation factor with the photodegradation rate.

7. The display unit according to claim 6, wherein

the photodegradation rate calculator derives the photodegradation rate by an interpolation calculation using the photodegradation reparation factor on the lookup table when the photodegradation reparation factor is not included in the lookup table.

8. The display unit according to claim 1, further comprising:

a capacitor that charges a voltage to be applied across a thin film transistor, where the thin film transistor serves as the first ambient light photosensor and the second ambient light photosensor.

9. The display unit according to claim 8, wherein

the first and second output signals are obtained by a photocurrent or a time taken for a voltage to drop by charging or discharging electric charges to the capacitor.

10. The display unit according to claim 1, wherein

the photodegradation factor calculator calculates the photodegradation reparation factor by transforming the first and second output signals to logarithms;

the photodegradation rate calculator obtains a logarithmically-transformed photodegradation rate from a logarithmically-transformed photodegradation reparation factor output from the photodegradation factor calculator by referring to the lookup table associating the logarithmically-transformed photodegradation reparation factor with the logarithmically-transformed photodegradation rate; and

the light signal output unit compensates the logarithmically-transformed first or second output signal with the logarithmically-transformed photodegradation rate, and outputs the compensated logarithmically-transformed first or second output signal by transforming the signal into an actual number.

11. The display unit according to claim 1, wherein

the display area includes an electrooptic material layer.

12. The display unit according to claim 1, wherein

the first photodetector and the second photodetector are provided in parallel on at least one side along an outer area of the display area respectively.

13. The display unit according to claim 1, wherein

the first photodetector and the second photodetector are provided alternately on at least one side along an outer area of the display area respectively.

14. The display unit according to claim 1, wherein

the first photodetector and the second photodetector are provided in a part of the pixel.

15. The display unit according to claim 12, wherein

the total size of the first ambient light photosensor and the total size of the second ambient light photosensor are equal.

16. The display unit according to claim 1, wherein

the light-reducing unit is a color filter, a polarizing plate, or a phase plate.

17. The display unit according to claim 4, wherein

the light-blocking component is a black matrix.