APPARATUS AND METHOD FOR CALIBRATING IMAGE CAPTURE DEVICES

• US 20090273679A1
• Filed: 09/26/2008
• Published: 11/05/2009
• Est. Priority Date: 05/01/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Bronstein, Chad Andrew, Gere, David S., Chen, Ting
• Granted Patent: US 8,405,727 B2
• Time in Patent Office: Days
• US Class Current: 348/187
• CPC Class Codes: H04N 17/002 for television cameras
• CPC Class Codes: H04N 23/843 Demosaicing, e.g. interpolating colour pixel values
• CPC Class Codes: H04N 25/134 based on three different wavelength filter elements
• CPC Class Codes: H04N 25/136 using complementary colours

Abstract

An apparatus and method are disclosed for calibrating image capture devices, such as the type used in electronic devices. In some embodiments, the electronic device may include at least one array of pixels and a memory coupled to the at least one array of pixels. The electronic device may further include a central processing unit (CPU) coupled to the memory and at least one color filter optically coupled to the at least one array of pixels. The memory may further include one or more storage locations that include a response of the at least one color filter to one or more predetermined wavelengths from a target test source, as well as, one or more storage locations that include a response of one or more baseline color filters.

Claims

1. An electronic image capture device, comprising:

at least one array of pixels;

a central processing unit (CPU) receiving data from the at least one array;

a memory accessible by the CPU and comprising a first storage location storing at least one correction value;

at least one color filter optically coupled to the at least one array of pixels, the color filter influencing the data;

wherein the processor is operative to apply the correction value to the data.

2. The electronic device of claim 1, wherein the correction value is a ratiometric comparison.

3. The electronic device of claim 2, wherein the correction value comprises at least one correction constant.

4. The electronic device of claim 3, wherein at least one of the one or more predetermined wavelengths includes one or more wavelengths in the infrared spectrum.

5. The electronic device of claim 3, wherein at least one of the one or more predetermined wavelengths includes one or more wavelengths near the cut-off wavelength of the infrared blocking filter.

6. The electronic device of claim 4, wherein the at least one instruction is updated when a firmware executed by the CPU is updated.

7. The electronic device of claim 1, wherein a response of the at least one color filter is calculated based on ratios of the wavelengths measured from the plurality of wavelength emanating regions.

8. The electronic device of claim 1, the response of the at least one color filter is stored in one or more memory locations after the electronic device has been manufactured.

9. The electronic device of claim 1, wherein the color filter data is measured in response to the one or more predetermined wavelengths.

14. The method of claim 9, wherein at least one of the one or more predetermined wavelengths of light is in the infrared range.

10. A method for calibrating an electronic image capture device, comprising the operations of:

storing, in a memory within the electronic device, a first color response of one or more baseline filters;

storing, in the memory within the electronic device, a second color response of one or more filters located within the electronic device to a light source having one or more predetermined wavelengths;

comparing the first color response of the one or more baseline filters with the second color response of the one or more filters located within the electronic device; and

based on the comparison, adjusting the second color response of the one or more filters located within the electronic device.

11. The method of claim 10, further comprising the operation of exposing the electronic device to a target test structure after the electronic device has been manufactured.

12. The method of claim 11, wherein the target test structure comprises one or more calibration patterns that include a plurality of wavelength emanating regions.

13. The method of claim 12, further comprising the operation of measuring the ratios of the one or more filters located within the electronic device from at least two of the plurality of wavelength emanating regions.

15. The method of claim 13, wherein the operation of measuring the ratios of color responses is executed in a processor within the electronic device.

16. The method of claim 15, further comprising the operation of updating the first color response of the one or more baseline filters when a firmware executed by the processor is updated.

17. The method of claim 10, further comprising the operation of determining the first color response of the one or more baseline filters based on the light source having one or more predetermined wavelengths.

18. A system for calibrating an image capture device comprising:

at least one color filter that operative to react to a combination of a calibration pattern and a light source that is optically coupled to the at least one color filter;

a memory coupled to the at least one color filter, the memory comprising one or more storage locations; and

a central processing unit (CPU) accessing the memory;

wherein the calibration pattern further comprises two or more regions that emanate a plurality of predetermined wavelengths;

wherein the two or more regions that emanate a plurality of predetermined wavelengths are oriented in substantially close physical proximity within the calibration pattern; and

wherein a comparison between at least two of the two or more regions that emanate a predetermined wavelength is stored in one or more storage locations of the memory.

19. The system of claim 18, wherein a response of one or more baseline color filters to the one or more regions that emanate a predetermined wavelength is stored in the one or more storage locations of the memory.

20. The system of claim 19, wherein the comparisons between at least two of the one or more regions that emanate a predetermined wavelength are ratiometric comparisons.