Dual band image switching compensation systems and methods

1 . A method comprising:

operating a plurality of infrared detectors in a dual band mode to capture infrared images alternating between a first wavelength range and a second wavelength range, wherein the operating comprises:

capturing a first infrared image corresponding to the first wavelength range,

switching the infrared detectors to respond to the second wavelength range, and

capturing a second infrared image corresponding to the second wavelength range;

determining a correlation between:

differences in pixel values of the first and second infrared images captured in the dual band mode, and

differences in pixel values exhibited by the second infrared image in relation to a third infrared image of the second wavelength range captured by the infrared detectors in a single band mode;

calculating, using the correlation, a correction term to compensate for dual band mode fixed pattern noise (FPN) in the second infrared image associated with the switching; and

applying the correction term to the second infrared image to reduce the dual band mode FPN.

2 . The method of claim 1 , wherein:

the infrared detectors are selectively configurable to operate in the dual band mode or the single band mode; and

the infrared detectors in the single band mode are configured to capture sequential infrared images in one of the first wavelength range or the second wavelength range.

3 . The method of claim 2 , wherein:

the correction term is a first correction term; and

the method further comprises applying a second correction term to the second infrared image to reduce single band mode FPN.

4 . The method of claim 1 , wherein the correction term is a global correction term applied to all pixels of the second infrared image.

5 . The method of claim 1 , wherein the correction term is one of a plurality of pixel-wise correction terms applied to corresponding pixels of the second infrared image.

6 . The method of claim 1 , wherein:

the infrared detectors are diodes comprising P-N junctions; and

the diodes are selectively configurable to pass currents in a first direction responsive to the first wavelength range and in a second direction responsive to the second wavelength range.

7 . The method of claim 1 , wherein the first and second infrared images are captured in sequential first and second integration periods, respectively.

8 . The method of claim 1 , wherein:

the infrared detectors are implemented by a plurality of corresponding unit cells each comprising a sample-hold circuit and an integration circuit; and

the method further comprises storing the first infrared image by the sample-hold circuits while the second infrared image is received by the integration circuits during the capturing of the second infrared image.

9 . A method comprising:

operating a plurality of infrared detectors in a dual band mode to capture infrared images alternating between a first wavelength range and a second wavelength range, wherein the operating comprises:

capturing a first infrared image corresponding to the first wavelength range,

switching the infrared detectors to respond to the second wavelength range, and

capturing a second infrared image corresponding to the second wavelength range;

determining a correlation between dual band mode fixed pattern noise (FPN) in the second infrared image associated with the switching and differences in pixel values of the first and second infrared images by:

operating the infrared detectors in a single band mode to capture a first set of sequential infrared images corresponding to the first wavelength range,

operating the infrared detectors in the single band mode to capture a second set of sequential infrared images corresponding to the second wavelength range,

operating the infrared detectors in the dual band mode to capture a third set of infrared images alternating between the first and second wavelength ranges,

comparing the first and second sets of infrared images to the third set of infrared images to determine offsets in pixel values of the third set of infrared images in relation to the first and second sets of infrared images,

determining differences in pixel values of the first and second wavelength range infrared images of the third set, and

correlating the offsets in pixel values of the third set of infrared images to the differences in the pixel values of the first and second wavelength range infrared images of the third set;

calculating, using the correlation, a correction term to compensate for the dual band mode FPN in the second infrared image associated with the switching, wherein the calculating uses a correlation between the dual band mode FPN and differences in pixel values of the first and second infrared images; and

applying the correction term to the second infrared image to reduce the dual band mode FPN.

10 . The method of claim 9 , wherein the correlation comprises a correlation between:

differences in pixel values of the first and second infrared images captured in the dual band mode, and

differences in pixel values exhibited by the second infrared image in relation to a third infrared image of the second wavelength range captured by the infrared detectors in a single band mode.

11 . A system comprising:

a plurality of infrared detectors configured to:

operate in a dual band mode to capture infrared images alternating between a first wavelength range and a second wavelength range,

capture, in the dual band mode, a first infrared image corresponding to the first wavelength range,

switch, in the dual band mode, to respond to the second wavelength range, and

capture, in the dual band mode, a second infrared image corresponding to the second wavelength range; and

a logic device configured to:

determine a correlation between:

differences in pixel values of the first and second infrared images captured in the dual band mode, and

differences in pixel values exhibited by the second infrared image in relation to a third infrared image of the second wavelength range captured by the infrared detectors in a single band mode,

calculate, using the correlation, a correction term to compensate for dual band mode fixed pattern noise (FPN) in the second infrared image associated with the switch, and

apply the correction term to the second infrared image to reduce the dual band mode FPN.

12 . The system of claim 11 , wherein:

the infrared detectors are selectively configurable to operate in the dual band mode or a single band mode; and

the infrared detectors in the single band mode are configured to capture sequential infrared images in one of the first wavelength range or the second wavelength range.

13 . The system of claim 12 , wherein:

the correction term is a first correction term; and

the logic device is configured to apply a second correction term to the second infrared image to reduce single band mode FPN.

14 . The system of claim 11 , wherein the correction term is a global correction term applied to all pixels of the second infrared image.

15 . The system of claim 11 , wherein the correction term is one of a plurality of pixel-wise correction terms applied to corresponding pixels of the second infrared image.

16 . The system of claim 11 , wherein the correlation comprises a correlation between the dual band mode FPN and the differences in pixel values of the first and second infrared images.

17 . The system of claim 16 , wherein the logic device is configured to:

operate the infrared detectors in a single band mode to capture a first set of sequential infrared images corresponding to the first wavelength range;

operate the infrared detectors in the single band mode to capture a second set of sequential infrared images corresponding to the second wavelength range;

operate the infrared detectors in the dual band mode to capture a third set of infrared images alternating between the first and second wavelength ranges;

compare the first and second sets of infrared images to the third set of infrared images to determine offsets in pixel values of the third set of infrared images in relation to the first and second sets of infrared images;

determine differences in pixel values of the first and second wavelength range infrared images of the third set; and

correlate the offsets in pixel values of the third set of infrared images to the differences in the pixel values of the first and second wavelength range infrared images of the third set.

18 . The system of claim 11 , wherein:

the infrared detectors are diodes comprising P-N junctions; and

the diodes are selectively configurable to pass currents in a first direction responsive to the first wavelength range and in a second direction responsive to the second wavelength range.

19 . The system of claim 11 , wherein the first and second infrared images are captured in sequential first and second integration periods, respectively.

20 . The system of claim 11 , further comprising:

a plurality of unit cells each comprising at least one of the infrared detectors, a sample-hold circuit, and an integration circuit; and

the sample-hold circuits are configured to store the first infrared image while the second infrared image is received by the integration circuits during the capture of the second infrared image.