IMAGE NOISE REDUCTION USING MODULATION AND DEMODULATION - DEMODULATION TECHNIQUES
A system, method and device for filtering noise from image data is disclosed. The method includes: (a) obtaining image data based at least in part on a modulated image signal, wherein the modulated image signal is obtained based on modulating an input infrared signal, (b) demodulating the image data to obtain a filtered image signal in which at least part of 1/f n noise is filtered from the image data, and (c) providing the filtered image signal.
1 . A method for filtering noise from image data, comprising:
obtaining image data based at least in part on a modulated image signal, wherein the modulated image signal is obtained based on modulating an input infrared signal;
demodulating the image data to obtain a filtered image signal in which at least part 1/f n noise is filtered from the image data; and
providing the filtered image signal.
2 . The method of claim 1 , wherein obtaining the image data comprises:
generating, by a detector, a transduced optical signal is based at least in part on the modulated image signal.
3 . The method of claim 1 , wherein the demodulation occurs inside each pixel within a read-out integrated circuit (ROIC).
4 . The method of claim 2 , wherein the transduced optical signal is generated as a function of time.
5 . The method of claim 2 , wherein the transduced optical signal comprises a dark current and a current generated by an optics module used to collect the optical image signal.
6 . The method of claim 5 , wherein a temperature of a device used to collect the optical signal causes at least part of the dark current.
7 . The method of claim 1 , further comprising:
at end of an integration period, determining an amount of charge accumulated from a set of currents generated in the collection and processing of the input infrared signal.
8 . The method of claim 6 , wherein the set of current comprises:
a scene current corresponding to a detection of the input infrared signal;
an optics current that is inherent to operation of an optics module used to collect the input infrared signal; and
a dark current generated by a device used to process the collected input infrared signal.
9 . The method of claim 1 , wherein the demodulating the image to obtain the filtered image signal comprises iteratively switching between (i) an accumulating phase in which a charge for scene current detected from the input infrared signal is up-counted, and (ii) a decumulating phase in which the charge for the scene current is down-counted.
10 . The method of claim 9 , wherein the switching between the accumulating phase and the decumulating phase results in obtaining a sum of an optics current and a dark current.
11 . The method of claim 10 , wherein the sum of the optics current and the dark current is subtracted from the image data.
12 . The method of claim 9 , wherein the switching between the accumulating phase and the decumulating phase is performed at a frequency used to modulate the input infrared signal to obtain the modulated image signal.
13 . The method of claim 9 , wherein the switching is performed synchronously with modulation of the input infrared signal captured by an optics module.
14 . The method of claim 1 , wherein modulating the input infrared signal comprises modulating an intensity of the image signal.
15 . The method of claim 14 , wherein the intensity of the image signal is modulated by physically blocking and unblocking the image signal at the predefined frequency.
16 . The method of claim 15 , wherein:
a mechanical chopper is located in an image signal path;
the mechanical chopper comprises a set of open sections and a set of closed sections; and
the physically blocking and unblocking the image signal is caused by rapidly scanning successive open sections and blocked sections through the image signal path.
17 . The method of claim 14 , wherein modulating the intensity of the signal comprises causing a set of polarizing optics to modify a polarization of the image signal as the image signal is incident on the set of polarizing optics.
18 . The method of claim 14 , wherein modulating the intensity of the signal comprises controlling an electro-optical modulator to modify an index of refraction through which the image signal is transmitted.
19 . The method of claim 1 , wherein modulating the input infrared signal comprises modulating a line of sight of the image signal at the predefined frequency.
20 . The method of claim 19 , wherein modulating the line of sight comprises causing a stabilization mechanism for the optical system to dither according to the predefined frequency.
21 . The method of claim 19 , wherein modulating the line of sight comprises causing a stabilization mechanism for the optical system to successively move between a first line of sight angle and a second line of sight angle.
22 . The method of claim 19 , wherein modulating the line of sight comprises driving an acousto-optical modulator to dither pointing of a beam passing through the acousto-optic modulator.
23 . An optical system, comprising:
an optical component configured to obtain image data based at least in part on a modulated image signal, wherein the modulated image signal is obtained based on modulating an input infrared signal;
a sensor processor configured to demodulate the image data to obtain a filtered image signal in which at least part of 1/f n noise is filtered from the image data;
a processor configured to provide the filtered image signal; and
a memory coupled to the processor and configured to provide the processor with instructions.