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

• US 8,008,613 B2
• Filed: 05/05/2009
• Issued: 08/30/2011
• 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 T
• Application Number:
  US12/435,909
• Publication Number:
  US 20100282953A1
• Time in Patent Office: 847 Days
• Field of Search: 250/226, 250/239, 250/214.AL, 250/214.1, 250/338.1, 250/216, 455/556.1, 455/566, 257/291, 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. A light sensing device comprising:

a first filter to block visible light in a light path;

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

a light intensity calculator to compute a measure of the intensity of visible light in said 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.

2. The light sensing device of claim 1 wherein the first filter comprises:

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

3. The light sensing device of claim 1 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.

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

5. The light sensing device of claim 4 wherein to compute the measure of the intensity of light, the intensity calculator is to convert said two output signal differences, which represent cyan and yellow values, into a green value.

6. The light sensing device of claim 3 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.

7. The light sensing device of claim 3 further comprising:

a third color sensor to detect light in said light path, after the first blocking filter, 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.

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

9. The light sensing device of claim 8 wherein to compute the measure of the intensity of light, the intensity calculator is to convert said three output signal differences, which represent cyan, magenta and yellow values, into red, green and blue values.

10. The light sensing device of claim 9 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.

11. 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 first filter which blocks visible light but not infrared 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 first filter,

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.

12. The electronic device of claim 11 wherein the housing has further integrated therein a second filter to block infrared light but not visible light in said light path, wherein the first color sensor, the second color sensor, and the clear sensor is to detect light in said light path after the first and second colors filters.

13. The electronic device of claim 11 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.

14. The electronic device of claim 11 wherein the first filter comprises a glass substrate on which there is a coating of infrared light transmitting ink that also blocks visible light.

15. The electronic device of claim 11 further comprising a second color sensor to detect light in the light path after the first filter, 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.

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

17. The electronic device of claim 16 wherein to compute the measure of the intensity of light, the processor is to convert said two output signal differences, which represent cyan and yellow values, into a green value.

18. The electronic device of claim 15 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.

19. A light sensing device comprising:

blocking means for blocking visible light in a light path;

first means for producing a signal that is indicative of a sensed intensity of light of a single visible color, in the light after the blocking means;

second means for producing a signal that is indicative of a sensed intensity of light of a plurality of visible colors, including said single visible color, in the light after the blocking means; and

means for computing a measure of the intensity of visible light in the light path, based on a difference between (a) the signal from the first producing means and (b) the signal from the second producing means.