Method for determining temperature of an active pixel imager and automatic correcting temperature induced variations in an imager
View Patent ↗An imager temperature sensor and a current correction apparatus are provided which use dark pixel measurements from an imager chip during operation together with a fabrication process constant as well as a chip dependent constant to calculate chip temperature. The chip temperature may be used to generate a current correction signal. The correction signal is used to tune a current on the imager chip to correct for temperature variations.
1. A method of determining temperature of an imager chip, said method comprising:
storing a fabrication process dependent value for an imager chip;
storing at least one chip dependent value representing a measured pixel dark current reference value and a reference temperature at which said chip dependent dark current reference value was measured;
measuring a dark current value of a pixel on said chip; and
determining a chip temperature representation based on said measured dark current value and stored values.
2. A method of claim 1 further comprising storing said fabrication process dependent value and said chip dependent value on said chip.
3. A method of determining temperature of an imager device, said method comprising:
acquiring at least one dark current signal from at least one pixel in a pixel array; and
determining a temperature value using said acquired dark current signal together with a fabrication process value, and at least one other value representing a reference dark current signal of a pixel of said pixel array taken at a reference temperature.
4. A method as in claim 3 wherein said at least one other value is an imager chip dependent value.
5. A method as in claim 3 further comprising storing said dark current signal and said reference temperature at said imager device.
6. A method as in claim 3 wherein said chip dependent value is stored at said imager device.
7. A method of claim 3 further comprising correcting at least one temperature dependent parameter of said imager device using said temperature value.
8. A method of claim 7 wherein said parameter is a current.
9. A method of claim 7 wherein said parameter is aresistance.
10. A method of claim 7 wherein said parameter is a voltage.
11. A method of claim 8 wherein said parameter is an impedance.
12. A method of claim 7 wherein said parameter is a capacitance.
13. A method of determining temperature of an imager chip, said method comprising:
storing a fabrication process dependent value for an imager chip;
acquiring at least one dark current signal at a plurality of locations of a pixel array; and
determining an associated temperature value for each of said locations using a respective said at least one dark current signal and said fabrication process dependent value.
14. A method as in claim 13 further comprising respectively adjusting each of a plurality of temperature dependent parameters of said imager based on an associated said temperature value.
15. A method as in claim 14 wherein said parameters comprise a current.
16. A method as in claim 14 wherein said parameters comprise an impedance.
17. A method as in claim 14 wherein said parameters comprise a resistance.
18. A method as in claim 14 wherein said parameters comprise a voltage.
19. A method as in claim 14 wherein said parameters comprise a capacitance.
20. A method of determining an imager chip temperature comprising:
sampling a dark pixel signal with a first integration time;
sampling a second dark pixel signal with a second integration time;
providing a calibrated dark pixel signal using said first and second sampled dark pixel signals; and
calculating a chip temperature using the calibrated dark pixel signal and a fabrication process dependent value related to dark current and temperature, and a chip dependent value related to dark current and temperature.
21. A method as in claim 20 wherein said fabrication process dependent value is related to temperature dependent dark current behavior of a plurality of imager devices manufactured using the same manufacturing process.
22. A method of determining an imager chip temperature comprising:
sampling a first and second dark pixel signals from each of a plurality of dark pixel clusters, each said cluster sampling comprising:
sampling a first dark pixel signal with a first integration time; and
sampling a second dark pixel signal with a second integration time;
calculating a calibrated dark pixel signal for each dark pixel cluster using said first and second dark pixel signal of each cluster; and
calculating a separate chip temperature for each said dark pixel cluster using a said calibrated dark pixel signal for each said cluster and a fabrication process dependent value related to dark current and temperature, and a chip dependent value.