Rolling subframe pulsed bias microbolometer integration
View Patent ↗Methods and systems for enabling an approximation of true snapshot integration by lowering total power requirements, total detector bias current, integrated charge per detector and detector impedance while allowing for higher ROIC input noise through the use of microbolometer photodetectors, super-pixels, and techniques for their use are herein provided.
1. An infrared imaging apparatus comprising:
a focal plane array, said focal plan array comprising:
a plurality of pixels, wherein said pixels are grouped into subsets containing equal numbers of pixels, each pixel comprising:
a microbolometer configured to receive electromagnetic energy; and
a readout integrated circuit (ROIC) wherein one microbolometer from each group is integrated by the ROIC simultaneously, and wherein the remaining microbolometers are integrated one at a time, simultaneously with those of all other groups of pixels and wherein the results of each integration is summed to provide a total frame integration value for each pixel and the integrated current is read off of the ROIC.
2. The infrared imaging apparatus of claim 1 wherein the ROIC of each pixel comprises a detector common, a BDI input with low noise bias amp, an integration stop switch, a readout integration capacitor, a comparator with threshold voltage input, a reference/ramp, an integration reset switch, a count reset connection, an enable count latch, a global clock, a readout connection, a data in bus, a count/shift bus, a counter/shift register, and a data out module.
3. The infrared imaging apparatus of claim 1 wherein said ROIC is configured to perform in-pixel single slope analog to digital conversion.
4. The infrared imaging apparatus of claim 1 wherein said ROIC is configured to perform in-pixel two-stage analog to digital conversion.
5. An infrared imaging apparatus comprising:
A focal plane array, said focal plane array comprising:
a plurality of groups of pixels;
wherein each pixel is grouped into subsets containing equal numbers of pixels, and wherein a group of pixels shares a plurality of components with other pixels in said group of pixels,
wherein each pixel comprises a microbolometer photodetector,
wherein each of said groups of pixels is configured to perform in-pixel analog to digital conversion of electromagnetic energy collected by said microbolometers within that group of pixels using a readout integrated circuit (ROIC) common to said group of pixels, and
wherein one microbolometer from each group is integrated by the ROIC simultaneously, and wherein the remaining microbolometers are integrated one at a time, simultaneously with those of all other groups of pixels, with the integration repeated until all the microbolometers for each pixel have been integrated by the ROIC, and wherein the results of each integration is summed to provide a total frame integration value for each pixel and the integrated current is read off the ROIC.
6. The infrared imaging apparatus of claim 5 wherein the ROIC common to each grouping of pixels comprises a detector common, a BDI input with low noise bias amp, an integration stop switch, a readout integration capacitor, a comparator with threshold voltage input, a reference/ramp, an integration reset switch, a count reset connection, an enable count latch, a global clock, a latch connection, a data in bus, a count/shift bus, a charge pump analog multi-value digital counter, and a data out module.
7. The infrared imaging apparatus of claim 5 wherein the ROIC common to each grouping of pixels comprises a detector common, a BDI input with low noise bias amp, an integration stop switch, a readout integration capacitor, a comparator with threshold voltage input, a reference/ramp, an integration reset switch, a count reset connection, an enable count latch, a global clock, a latch connection, a data in bus, a count/shift bus, a counter/latch, and a data out module.
8. The infrared imaging apparatus of claim 7 further comprising a latch module comprising a select latch write and select latch read, wherein said latch module is in operative communication with said counter/latch.
9. The infrared imaging apparatus of claim 8 further comprising a multiplexer disposed between said microbolometer and said bias amp.
10. The infrared imaging apparatus of claim 9 wherein said ROIC is configured to perform in-pixel single slope ADC.
11. The infrared imaging apparatus of claim 9 wherein said ROIC is configured to perform in-pixel two-stage ADC.
12. A rolling subframe pulse bias integration method comprising:
on a focal plane array comprising a plurality of pixels, wherein said pixels are grouped into subsets containing equal numbers of pixels, each pixel comprising a microbolometer photodetector:
using a readout integrated circuit (ROIC), integrating one microbolometer from each group of pixels simultaneously;
integrating the remaining microbolometers in each group, one at a time, simultaneously with those of all other groups of pixels;
summing the results of each integration, thereby providing a total frame integration value for each pixel; and
reading the integrated current off of the ROIC.
13. The method of claim 12 wherein reading the integrated current off of the ROIC comprises:
reading out of coarse data off of the ROIC; and
performing fine conversion of the coarse data.
14. The method of claim 13 further comprising, after performing fine conversion of the coarse data, reading out of said fine data off of the ROIC.
15. The method of claim 12 further comprising repeating the integration of said pixels a plurality of times after each pixel from a group of pixels has been integrated.
16. The method of claim 12 wherein integration of one microbolometer from each group of pixels occurs over a small fraction of a portion of a frame dedicated to readout integration.