IMAGING SYSTEMS AND METHODS INCLUDING OBSCURANT CHARACTERIZATION

• US 20170243079A1
• Filed: 02/17/2017
• Published: 08/24/2017
• Est. Priority Date: 02/18/2016
• Status: Active Grant

• Current Assignee: L3harris Cincinnati Electronics Corporation (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Cincinnati Electronics Corporation (L3Harris Technologies, Inc.)
• Inventors: HIRIYANNAIAH, HARISH P., TANG, NANSHENG
• Granted Patent: US 9,824,295 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 26/008 in the form of devices for effecting sequential colour changes, e.g. colour wheels
• CPC Class Codes: G02B 27/281 used for attenuating light intensity, e.g. comprising rotatable polarising elements
• CPC Class Codes: G02B 27/286 for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34
• CPC Class Codes: G02B 27/288 Filters employing polarising elements, e.g. Lyot or Solc filters G02B5/3016 takes precedence
• CPC Class Codes: G02B 5/201 in the form of arrays
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00
• CPC Class Codes: G06F 18/00 Pattern recognition
• CPC Class Codes: G06F 18/22 Matching criteria, e.g. proximity measures
• CPC Class Codes: G06V 10/141 Control of illumination
• CPC Class Codes: G06V 10/75 Organisation of the matching processes, e.g. simultaneous or sequential comparisons of image or video features; Coarse-fine approaches, e.g. multi-scale approaches; using context analysis; Selection of dictionaries

Abstract

Systems and methods for characterizing an obscurant and imaging a target are disclosed. In one embodiment, a method of imaging a target includes characterizing at least one obscurant present in an environment, and determining, based on the at least one characterized obscurant, one or more of the following: one or more wavelengths corresponding to the at least one obscurant, a polarization state corresponding to the at least one obscurant, and a sensor exposure time corresponding to the at least one obscurant. The method further includes adjusting one or more parameters of an imagining system based at least in part on a characterization of the at least one obscurant.

Claims

1. An imaging system comprising:

a sensor comprising an array of pixels, each individual pixel of the array of pixels configured to detect optical radiation;

a multispectral filter disposed within an optical path of the sensor, the multispectral filter comprising a plurality of filters, wherein each individual filter of the plurality of filters is transmissive to optical radiation having a wavelength within a wavelength range;

a polarizing filter disposed within the optical path of the sensor, wherein the polarizing filter is capable of filtering optical radiation at a plurality of polarization states;

a processor; and

a non-transitory computer-readable medium storing instructions that, when executed by the processor, causes the processor to;

characterize at least one obscurant that is present within an environment; and

based at least on a obscurant characterization, perform one or more of the following;

adjust the multispectral filter;

apply a selected polarization state of the polarizing filter; and

select an exposure time for the sensor.

2. The imaging system of claim 1, wherein the at least one obscurant comprises at least one of snow, rain, fog, clouds, smoke, smog, sand, and dust.

3. The imaging system of claim 1, wherein characterizing the at least one obscurant comprises receiving a user input received by the processor, the user input comprising a selected obscurant.

4. The imaging system of claim 3, wherein the instructions further cause the processor to:

access a database storing a plurality of parameters corresponding to a plurality of obscurant characterizations, wherein each individual obscurant characterization comprises one or more of at least one wavelength parameter, at least one polarization parameter, and at least one exposure time parameter; and

select a selected obscurant characterization corresponding to the selected obscurant.

5. The imaging system of claim 4, wherein, based on the selected obscurant characterization, the instructions further cause the processor to perform one or more of the following:

adjust the multispectral filter such that the multispectral filter applies a selected wavelength parameter of the selected obscurant characterization;

set the selected polarization state in accordance with the at least one polarization parameter of the selected obscurant characterization; and

adjust the exposure time in accordance with the at least one exposure time parameter of the selected obscurant characterization.

6. The imaging system of claim 4, wherein the plurality of obscurant characterizations is based at least in part on historical obscurant data.

7. The imaging system of claim 3, wherein characterizing at least one obscurant further comprises receiving a geolocation, a date, a time of day, a temperature, an atmospheric pressure, and a humidity.

8. The imaging system of claim 1, further comprising a light source, wherein the instructions further cause the processor to characterize the at least one obscurant by:

controlling the light source to emit a beam by sweeping the beam across a plurality of wavelengths;

selectively applying a spectral filter of a plurality of spectral filters to the sensor corresponding to the plurality of wavelengths;

detecting, using a sensor, an optical power of returned optical radiation of the beam for individual wavelengths of the plurality of wavelengths of the beam; and

determining a wavelength of returned optical radiation providing an optimal optical power.

9. The imaging system of claim 8, wherein:

the wavelength of returned optical radiation providing an optimal optical power is determined by individual pixels of the sensor; and

individual pixels of the sensor correspond to individual portions of the at least one obscurant such that individual portions of the at least one obscurant are characterized.

10. The imaging system of claim 1, further comprising a light source, wherein the instructions further cause the processor to characterize the at least one obscurant by:

controlling the light source to emit a beam through the obscurant and onto a target by sweeping the beam across a plurality of wavelengths and selectively applying a spectral filter to the sensor corresponding to the plurality of wavelengths;

for each wavelength of the plurality of wavelengths, generating an image of the target;

for each image of the target, generating an image quality metric; and

selecting the wavelength associated with the image having a highest image quality metric as the wavelength parameter.

11. The imaging system of claim 1, wherein the instructions further cause the processor to characterize the at least one obscurant by:

selectively applying a spectral filter of a plurality of wavelengths to the sensor;

for each wavelength of the plurality of wavelengths, generating an image of a target;

for each image of the target, generating an image quality metric; and

selecting the wavelength associated with the image having a highest image quality metric as the wavelength parameter.

12. The imaging system of claim 1, further comprising a light source, wherein the instructions further cause the processor to characterize the at least one obscurant by:

controlling the light source to emit a beam by changing a polarization state of the beam;

selectively applying a polarization filter of a plurality of polarization filters to the sensor corresponding to the plurality of polarizations;

detecting an optical power of returned optical radiation of the beam for individual polarization states of a plurality of polarization states; and

determining a polarization state providing an optimal optical power.

13. The imaging system of claim 12, wherein:

the polarization state providing an optimal optical power is determined by individual pixels of the sensor; and

individual pixels of the sensor correspond to individual portions of the at least one obscurant such that individual portions of the at least one obscurant are characterized.

14. The imaging system of claim 13, wherein the polarization state of the beam is selected from a group consisting of:

a circular polarization, a linear polarization, and an elliptical polarization.

15. The imaging system of claim 1, further comprising a light source, wherein the instructions further cause the processor to characterize the at least one obscurant by:

controlling the light source to emit a beam through the obscurant and onto a target by changing a polarization state of the beam across a plurality of polarization states and selectively applying a polarization filter to the sensor corresponding to the plurality of polarization states;

for each polarization state of the plurality of polarization states, generating an image of the target;

for each image of the target, generating an image quality metric; and

selecting the polarization state associated with the image having a highest image quality metric as the polarization parameter.

16. The imaging system of claim 1, wherein the instructions further cause the processor to characterize the at least one obscurant by:

selectively applying a polarization filter having a plurality of polarization states to the sensor;

for each polarization state of the plurality of polarization states, generating an image of a target;

for each image of the target, generating an image quality metric; and

selecting the polarization state associated with the image having a highest image quality metric as the polarization parameter.

17. The imaging system of claim 1, further comprising a light source, wherein the instructions further cause the processor to characterize the at least one obscurant by:

controlling the light source to emit a beam;

controlling the sensor to receive returned optical radiation of the beam by sweeping a range of exposure times;

detecting an optical power of returned optical radiation of the beam for an individual exposure time of the plurality of exposure times; and

determining a selected exposure time for one or more regions of interest of a scene providing an optimal optical power.

18. The imaging system of claim 1, further comprising a light source, wherein the instructions further cause the processor to characterize the at least one obscurant by:

controlling the light source to emit a beam;

creating a plurality of images, each image of the plurality of images having a different exposure time;

determining an image quality metric for each image; and

selecting the exposure time associated with the image having a highest image quality metric as an exposure time parameter.

19. The imaging system of claim 1, wherein the instructions further cause the processor to characterize the at least one obscurant by:

creating a plurality of images, each image of the plurality of images having a different exposure time;

determining an image quality metric for each image; and

selecting the exposure time associated with the image having a highest image quality metric as an exposure time parameter.

20. The imaging system of claim 1, further comprising a light source, wherein the instructions further cause the processor to characterize the at least one obscurant by:

controlling the light source to emit a beam by sweeping the beam across a plurality of wavelengths;

detecting, by individual pixels of the sensor, an optical power of returned optical radiation of the beam for individual wavelengths of the plurality of wavelengths of the beam;

determining a wavelength of returned optical radiation providing an optimal optical power among the plurality of wavelengths of the beam;

controlling the light source to emit the beam by sequentially changing a polarization state of the beam;

detecting, by the individual pixels of the sensor, the optical power of returned optical radiation of the beam for individual polarization states of a plurality of polarization states;

determining a polarization state providing an optimal optical power among the plurality of polarization states;

controlling the sensor to receive returned optical radiation by sweeping a range of exposure times;

detecting an optical power of returned optical radiation of the beam for an individual exposure time of the plurality of exposure times; and

determining a selected exposure time for one or more regions of interest of a scene providing an optimal power among the plurality of exposure times.

21. The imaging system of claim 1, wherein:

the instructions further cause the processor to control a light source to emit an illumination beam;

the illumination beam has a polarization state corresponding to a polarization parameter of the obscurant; and

the illumination beam has a wavelength corresponding to a wavelength parameter of the obscurant.

22. The imaging system of claim 21, wherein the instructions further cause the processor to operate the sensor at an exposure time corresponding to an exposure time parameter of the obscurant.

23. The imaging system of claim 22, wherein the instructions further cause the processor to control the light source such that the illumination beam is scanned across a target.

24. The imaging system of claim 22, wherein the instructions further cause the processor to operate the sensor at a plurality of exposure times for a plurality of regions of interest of a scene.

25. The imaging system of claim 1, wherein:

the multispectral filter comprises a plurality of filters; and

the instructions further cause the processor to reposition the multispectral filter such that one or more individual filters of the plurality of filters that are transmissive to one or more wavelengths corresponding to the at least one obscurant are sequentially positioned within the optical path of the sensor.

26. The imaging system of claim 1, wherein:

the polarizing filter comprises a plurality of polarizing filters; and

the instructions further cause the processor to reposition the polarizing filter such that one or more individual polarizing filters of the plurality of polarizing filters having a polarization state corresponding to the at least one obscurant are sequentially positioned within the optical path of the sensor.

27. The imaging system of claim 1, wherein:

a group of six pixels of the sensor defines a pixel group;

the sensor comprises an array of pixel groups;

the polarizing filter is disposed on the array of pixels such that;

a first pixel of the pixel group has a first linear polarization state;

a second pixel of the pixel group has a second linear polarization state that is negative forty-five degrees with respect to the first linear polarization state;

a third pixel of the pixel group has a first circular polarization in a first direction;

a fourth pixel of the pixel group has a third linear polarization state that is positive forty-five degrees with respect to the first linear polarization state;

a fifth pixel of the pixel group has fourth linear polarization state that is orthogonal to the first linear polarization state; and

a sixth pixel of the pixel group has a second circular polarization in a second direction orthogonal to the first direction; and

applying the selected polarization state of the polarizing filter comprises constructing an image based at least in part on data from the polarization states of the array of pixel groups.

28. The system of claim 1, wherein:

the at least one obscurant that is present within the environment by an active characterization process; and

a characterization of the at least one obscurant and environmental data surrounding the characterization of the at least one obscurant are stored in a database as historical characterization data.

29. A method of imaging a target, the method comprising:

characterizing at least one obscurant present in an environment;

determining, based on the at least one characterized obscurant, one or more of the following;

one or more wavelengths corresponding to the at least one obscurant;

a polarization state corresponding to the at least one obscurant; and

a sensor exposure time corresponding to the at least one obscurant; and

adjusting one or more parameters of an imagining system based at least in part on a characterization of the at least one obscurant.

30. The method of claim 29, wherein characterizing at least one obscurant comprises:

controlling a light source to emit a beam by sweeping the beam across a plurality of wavelengths;

detecting, by individual pixels of a sensor, an optical power of returned optical radiation of the beam for individual wavelengths of the plurality of wavelengths of the beam;

determining a wavelength of returned optical radiation providing an optimal optical power among the plurality of wavelengths of the beam;

controlling the light source to emit the beam by sequentially changing a polarization state of the beam;

detecting, by the individual pixels of the sensor, the optical power of returned optical radiation of the beam for individual polarization states of a plurality of polarization states;

determining a polarization state providing an optimal optical power among the plurality of polarization states;

controlling the sensor to receive returned optical radiation by sweeping a range of exposure times;

detecting an optical power of returned optical radiation of the beam for an individual exposure time of the plurality of exposure times; and

determining a selected exposure time for one or more regions of interest of a scene providing an optimal optical power among the plurality of exposure times.