Light sensing device having a color sensor and a clear sensor for infrared rejection

• US 8,536,511 B2
• Filed: 07/02/2012
• Issued: 09/17/2013
• Est. Priority Date: 05/05/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Tam, Ching Yu John
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US13/540,156
• Publication Number:
  US 20130002731A1
• Time in Patent Office: 442 Days
• Field of Search: 250/226, 250/214.1, 250/208.1, 250/239, 250/338.1, 250/216, 455/556.1, 455/566, 257290-292, 257/440
• US Class Current: 250/226
• CPC Class Codes: G01J 1/0488 with spectral filtering
• CPC Class Codes: G01J 1/1626 Arrangements with two photodetectors, the signals of which are compared
• CPC Class Codes: G01J 1/32 adapted for automatic variation of the measured or reference value regulation of light intensity G05D25/00
• CPC Class Codes: G01J 1/4204 with determination of ambient light solar light G01J2001/4266

Abstract

A light sensing device has a first filter to block visible light in a light path. The light sensing device also has a first color sensor and a clear sensor, to detect light in the light path after the first filter. A light intensity calculator computes a measure of the intensity of visible light in the light path, based on a difference between (a) an output signal of the first color sensor, and (b) an output signal of the clear sensor. Other embodiments are also described and claimed.

Claims

1. An ambient visible light sensing device comprising:

a substrate on which there is a visibly opaque coating but through which ambient visible light is to pass;

a first color sensor having a first color filter and a clear sensor having no color filter, to detect the ambient visible light after the substrate; and

a light intensity calculator to compute a measure of the intensity of the ambient visible light, based on a difference between (a) an output signal of the first color sensor and (b) an output signal of the clear sensor.

2. The light sensing device of claim 1 further comprising:

a second color sensor having a second color filter different from the first color filter, wherein the light intensity calculator is to compute the measure of the intensity of light further based on a difference between (a) an output signal of the second color sensor and (b) the output signal of the clear sensor.

3. The light sensing device of claim 2 wherein the first and second color sensors are red and blue sensors, respectively.

4. The light sensing device of claim 3 wherein to compute the measure of the intensity of light, the intensity calculator is to convert a difference between (a) an output signal of the first color sensor and (b) an output signal of the clear sensor, and another difference between (a) an output signal of the second color sensor and (b) the output signal of the clear sensor, which represent cyan and yellow values, into a green value.

5. The light sensing device of claim 2 wherein each of the first and second color sensors comprises a different color filter element that covers a respective photodetector element, and wherein

the respective photodetector elements of the first and second color sensors and a photodetector element of the clear sensor are electrically matched.

6. The light sensing device of claim 2 further comprising:

a third color sensor having a third color filter different from the first and second color filters to detect light in said light path, after the substrate, and wherein

the light intensity calculator is to compute the measure of the intensity light further based on a difference between (a) an output signal of the third color sensor and (b) the output signal of the clear sensor.

7. The light sensing device of claim 6 wherein the first, second and third color sensors are red, blue, and green sensors, respectively.

8. The light sensing device of claim 7 wherein to compute the measure of the intensity of light, the intensity calculator is to convert 1) a difference between (a) an output signal of the first color sensor and (b) an output signal of the clear sensor, 2) another difference between (a) an output signal of the second color sensor and (b) the output signal of the clear sensor, and 3) a further difference between (a) an output signal of the third color sensor and (b) the output signal of the clear sensor, which represent cyan, magenta and yellow values, into red, green and blue values.

9. The light sensing device of claim 8 wherein the light intensity calculator is to compute the measure of the intensity of light as lux, based on the red, green and blue values.

10. An electronic device, comprising:

a housing having integrated therein

a front cover having a light transparent structural layer, the light transparent structural layer having a user-interactive display screen portion and an ambient light sensor portion, the ambient light sensor portion contains a visibly opaque layer that limits visible light outside the device from passing into a light path in the housing,

a processor coupled to control brightness of the display screen portion based on a calculated measure of intensity of ambient light outside the device, and

a first color sensor and a clear sensor, to detect light in said light path after the visibly opaque layer,

wherein the processor is to calculate said measure of ambient light intensity based on a difference between (a) an output signal of the first color sensor and (b) an output signal of the clear sensor.

11. The electronic device of claim 10 wherein the housing has further integrated therein an infrared cut layer that limits infrared light in said light path, wherein the first color sensor and the clear sensor are to detect light in said light path after the visibly opaque and infrared cut layers.

12. The electronic device of claim 10 wherein said difference is based on scaling one or both of (a) the output signal of the first color sensor, and (b) the output signal of the clear sensor.

13. The electronic device of claim 10 wherein the light transparent structural layer comprises a glass substrate on which the visibly opaque layer is formed as a coating of infrared light transmitting visibly opaque ink.

14. The electronic device of claim 10 further comprising a second color sensor to detect light in the light path after the visibly opaque layer, wherein the processor is to compute the measure of the intensity of light further based on a difference between (a) an output signal of the second color sensor and (b) the output signal of the clear sensor.

15. The light sensing device of claim 14 wherein the first and second color sensors are red and blue sensors, respectively.

16. The electronic device of claim 15 wherein to compute the measure of the intensity of light, the processor is to convert a difference between (a) an output signal of the first color sensor and (b) an output signal of the clear sensor, and another difference between (a) an output signal of the second color sensor and (b) the output signal of the clear sensor, which represent cyan and yellow values, into a green value.

17. The electronic device of claim 14 wherein each of the first and second color sensors comprises a different color filter element that covers a respective photodetector element, and wherein

the respective photodetector elements of the first and second color sensors and a photodetector element of the clear sensor are electrically matched.

18. An electronic device comprising:

a first filter which blocks ambient visible light but not infrared light in a light path, so as to give a dark appearance from outside the device that does not allow electronics inside the device to be visible et still allows detection of the visible light;

a first color sensor and a clear sensor, to detect the ambient visible light in said light path after the first filter;

wherein the clear sensor is configured to output a signal indicative of the sensed intensity of light of several visible colors;

wherein the first color sensor is tuned to sense a color of visible light; and

a light intensity calculator to compute a measure of the intensity of the ambient visible light based on a difference between (a) an output signal of the first color sensor and (b) an output signal of the clear sensor.

19. The electronic device of claim 18 wherein the first filter comprises:

a substrate on which there is a coating of infrared light transmitting ink that also blocks visible light.

20. The electronic device of claim 18 further comprising:

a second color sensor, wherein the light intensity calculator is to compute the measure of the intensity of light further based on a difference between (a) an output signal of the second color sensor and (b) the output signal of the clear sensor.

21. The electronic device of claim 20 wherein the first and second color sensors are red and blue sensors, respectively.

22. The electronic device of claim 21 wherein the clear sensor outputs a signal that gives the sensed intensity of light across the entire visible spectrum;

wherein to compute the measure of the intensity of light, the intensity calculator is to convert a difference between (a) an output signal of the first color sensor and (b) an output signal of the clear sensor, and another difference between (a) an output signal of the second color sensor and (b) the output signal of the clear sensor, which represent cyan and yellow values, into a green value.

23. The electronic device of claim 20 wherein each of the first and second color sensors comprises a different color filter element that covers a respective photodetector element, and wherein

the respective photodetector elements of the first and second color sensors and a photodetector element of the clear sensor are electrically matched.

24. The electronic device of claim 20 further comprising:

a third color sensor to detect light in said light path, after the first filter, and wherein

the light intensity calculator is to compute the measure of the intensity of light further based on a difference between (a) an output signal of the third color sensor and (b) the output signal of the clear sensor; and

wherein the clear sensor outputs a signal that gives the sensed intensity of light across the entire visible spectrum

wherein the first, second and third color sensors are red, blue, and green sensors, respectively; and

wherein to compute the measure of the intensity of light, the intensity calculator is to convert a difference between (a) an output signal of the first color sensor and (b) an output signal of the clear sensor, and another difference between (a) an output signal of the second color sensor and (b) the output signal of the clear sensor and a further difference between (a) an output signal of the third color sensor and (b) the output signal of the clear sensor, which represent cyan, magenta and yellow values, into red, green and blue values; and

wherein the light intensity calculator is to compute the measure of the intensity of light as lux, based on the red, green and blue values.