Ambient infrared detection in solid state sensors
A solid state imaging device includes an array of active pixels and an infrared cut filter formed over the sensor. Optionally, a slot in the infrared cut filter allows infrared illumination to reach the sensor to be detected by pixels covered by a visually opaque filter and surrounded by pixels of special types that limit charge leakage and enable high dynamic range sensing of infrared illumination. A ratio of average infrared signal to average brightness indicates an amount of infrared illumination reaching the imaging device.
1. An image sensor device comprising:
an array of pixels;
an infrared cutoff filter substantially covering a first predetermined area of the array of pixels; and
means for inhibiting both infrared and visible light spectrum substantially covering a second predetermined area of the array of pixels wherein a third predetermined area of the array of pixels remains exposed to both visible and infrared illumination.
2. The device of claim 1 wherein the infrared cutoff filter reduces illumination of the first predetermined area of the array of pixels in the infrared wavelength.
3. The device of claim 1 and further comprising a color filter array formed over the array of pixels.
4. The device of claim 3 wherein the color filter array is formed in a Bayer pattern.
5. The device of claim 1 wherein the means for inhibiting is a layer of metal.
6. The device of claim 1 wherein the means for inhibiting is a black color filter array.
7. The device of claim 1 wherein the third predetermined area substantially encircles the first predetermined area.
8. The device of claim 7 wherein the second predetermined area substantially encircles the third predetermined area.
9. An image sensor device comprising:
a substrate comprising an array of photodiodes;
a color filter array formed over the array of photodiodes such that a different color filter is formed over each photodiode;
an infrared cutoff filter formed over a predetermined area of the array of photodiodes;
an infrared barrier formed substantially around a periphery of the first predetermined area;
a plurality of infrared photodiodes formed substantially around a periphery of the infrared barrier; and
a plurality of black photodiodes formed substantially around a periphery of the plurality of infrared photodiodes.
10. The device of claim 9 wherein the substrate is comprised of p+ silicon and each photodiode is comprised of n− silicon.
11. The device of claim 9 wherein the substrate is comprised of n− silicon and each photodiode is comprised of p+ silicon.
12. The device of claim 9 wherein each of the plurality of infrared diodes comprises a color filter formed to selectively admit predetermined wavelengths of light to the photodiode and all of the plurality of infrared photodiodes is not blocked from exposure to and infrared wavelength of light.
13. The device of claim 12 wherein each of the plurality of black photodiodes comprises a filter that substantially inhibits admittance of all light wavelengths except infrared.
14. A method for fabricating a solid state image sensor device, the method comprising:
forming an array of photodiodes in a substrate;
forming a color filter array over the array of photodiodes;
forming an infrared cutoff filter over a first predetermine area of the array of photodiodes; and
forming a black filter over a second predetermined area of the array of photodiodes such that a third predetermined area of the array of photodiodes is filtered only by the color filter array.
15. The method of claim 14 and further including forming an infrared barrier between the third predetermined area and the first predetermined area.
16. The method of claim 14 wherein the third predetermined area is formed substantially around a periphery of the first predetermined area and the second predetermined area is formed substantially around a periphery of the third predetermined area.
17. The method of claim 14 wherein forming the black filter comprises forming a layer of metal over the second predetermined area.
18. The method of claim 14 and further including forming a lens over the infrared filter.
19. An image system comprising:
control circuitry that generates an image in response to pixel information; and
an image sensor device, coupled to the control circuitry, for generating the pixel information in response to received light, the device comprising:
an array of pixels;
an infrared cutoff filter substantially covering a first predetermined area of the array of pixels; and
means for inhibiting visible light spectrum substantially covering a second predetermined area of the array of pixels wherein a third predetermined area of the array of pixels remains exposed to both visible and infrared illumination.
20. The system of claim 19 wherein the image system is a digital camera.