Display device control based on integrated ambient light detection and lighting source characteristics

• US 20090152445A1
• Filed: 12/13/2007
• Published: 06/18/2009
• Est. Priority Date: 12/13/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Gardner, W. Bryson JR.
• Granted Patent: US 7,960,682 B2
• Time in Patent Office: Days
• US Class Current: 250/214.AL
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3225 using an active matrix
• 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 3/36 using liquid crystals
• CPC Class Codes: H05B 47/165 following a pre-assigned programmed sequence; Logic control [LC]

Abstract

Systems and methods are provided for a display device including one or more methods for modifying the display brightness by automatically adapting to ambient lighting conditions.

Claims

1. A transmissive display comprising:

an integrated light source for illuminating the transmissive display by emitting light during a first illumination period,

an integrated light sensor for generating a sensor signal based on the amount of light present during a first sensing interval after the first illumination period, and

a processor for receiving the sensor signal and controlling the light source during a second illumination period after the sensing interval based at least in part on the sensor signal.

2. The display of claim 1, wherein the path for the ambient light to reach the light sensor includes a path via the transmissive display.

3. The display of claim 1, wherein an illumination period includes a power period, during which the controller applies power to the integrated light source, and a delay period.

4. The display of claim 3, wherein the delay period is determined based on the illumination decay characteristics of at least one lighting element of the integrated light source.

5. The display of claim 4, wherein the at least one lighting element includes a light emitting diode (LED)

6. The display of claim 5, wherein the illumination decay characteristic of the LED is based on at least one of the physical properties of the LED, the age of the LED, the amount of power applied to the LED during the power interval, and the duration of the power period.

7. The display of claim 6, wherein a delay period associated with the second illumination period is determined based on at least one illumination decay characteristic.

8. The display of claim 3, wherein the delay period associated with an illumination period is preselected.

9. The display of claim 3, wherein the delay period associated with an illumination period is determined based on the amount of time required after the power period of the illumination level to reach a threshold level.

10. The display of claim 3, wherein controlling includes adjusting the duration of the power period of the second illumination period of adjust the illumination intensity of the display.

11. The display of claim 3, wherein controlling includes adjusting the amount of power applied to at least one lighting element of the integrated light source to adjust the illumination intensity of the display.

12. The display of claim 1, wherein the integrated light source includes an array of lighting elements.

13. A method for automatically controlling the level of illumination for a transmissive display comprising:

illuminating the transmissive display by emitting light from a light source during a first illumination period,

generating a sensor signal based on the amount of light present at an integrated light sensor during a first sensing interval after the first illumination period, and

controlling the emitting of light during a second illumination period after the sensing interval based at least in part on the sensor signal, the controlling including adjusting at least one of the duration of a power period and the amount of power applied to the light source.

14. A display device comprising:

a transmissive display assembly including;

a light source of emitting light over a first period of time to illuminate a portion of the display,

a sensor for sensing ambient light over a second period of time, and

a processor for controlling the emitting of light from the light source over the first period of time and the sensing of ambient light over the second period of time.

15. The device of claim 14, wherein the first period of time includes a period when the emitted light is above a predetermined threshold.

16. The device of claim 15, wherein the second period of time includes a period when the emitted light is at or below the predetermined threshold.

17. The device of claim 16, wherein the duration of a subsequent third period of time is determined, at least in part, by the amount of ambient light sensed during the second period of time.

18. The device of claim 17, wherein the duration of the third period of time is determined, at least in part, by the amount of light sensed during the first period of time.

19. The device of claim 14, wherein the transmissive display assembly includes of a liquid crystal display.

20. The device of claim 14, wherein the light source is comprised of an array of white light emitting diodes.

21. The device of claim 14, wherein the light sensor is comprised of one or more photodiodes or phototransistors that are sensitive to white light.

22. The device of claim 14, wherein the light source is comprised of an array of red, blue, and green light emitting diodes.

23. The device of claim 22, wherein the sensor is comprised of one or more groups of photodiodes or phototransistors that are sensitive to the frequencies of red, blue, green light emitted by the light emitting diodes.

24. A transmissive display comprising:

a sensor for generating a sensor signal based on the amount of light present at its receptor,

a light source for illuminating the transmissive display,

a processor for repeatedly performing the following i) applying power to the light source during a first period to time, ii) waiting a second period to time for the emitted light intensity from the light source to decay below a light sensor interference level, and iii) sensing the ambient light passing through the transmissive display during a third period of time.

25. A method for automatically controlling the level of illumination for a transmissive display based on measured ambient light levels comprising the steps of:

A. enabling the light source to emit light and measuring the intensity of the light emitted by the light source during a first time period,

B. inhibiting the light source from emitting light and measuring the intensity of ambient light during a second time period,

C. processing the light measurements from the first time period and second time period to determine the durations of the first time period and second time period for a subsequent iteration of steps A-C, and

D. repeating steps A-C at least once.

26. A method for controlling a display device comprising:

illuminating the display device by emitting light from a light emitting diode (“

LED”

) for a first period of time;

generating a signal with the LED associated with an amount of ambient light present during a second period of time after the first period of time; and

controlling the emitting of light from the LED based on the signal during a third period of time after the second period of time.

27. The method of claim 26, wherein the controlling comprises:

adjusting a duration of time in which power is applied to the LED.

28. The method of claim 26, wherein the controlling comprises:

adjusting an amount of power applied to the LED.

29. The method of claim 26, wherein the generating comprises:

waiting for a delay period to finish; and

generating the signal with the LED after the delay period has finished.

30. The display of claim 29, wherein the duration of the delay period is associated with at least one of a physical property of the LED, an age of the LED, an amount of power applied to the LED during the first period of time, a duration of time in which power is applied to the LED during the first period of time, and an ambient temperature.

31. A system comprising:

a display;

a light emitting diode (“

LED”

) operable to;

emit light to illuminate the display during a first period of time; and

stop emitting light and generate a signal associated with the amount of ambient light present during a second period time after the first period of time; and

a processor operable to control the emitting of the light by the LED based on the generated signal.

32. The system of claim 31, wherein:

the first period of time is a duty-cycle-on period associated with a pulse width modulated signal; and

the second period of time is a duty-cycle-off period associated with the pulse width modulated signal.

33. The system of claim 32, wherein the processor is further operable to control the duration of at least one of the duty-cycle-on period and the duty-cycle-off period based on the generated signal.

34. The system of claim 31, further comprising a plurality of LED'"'"'s, and wherein the processor is further operable to provide power to a subset of the LED'"'"'s based on the generated signal.