N161-057 TITLE: Short-Wave Polarimetric Imager

TECHNOLOGY AREA(S): Sensors

ACQUISITION PROGRAM: No specific program currently.

OBJECTIVE: Develop and demonstrate a short wave infrared (SWIR) band polarimetric imager consisting of an uncooled indium gallium arsenide (InGaAs) focal plane array with an aligned, pixel pitch-matched micro-grid polarizer (Bayer-type) array. The SWIR InGaAs polarizer camera should be compact, rugged and with sufficient frame rate to enable on-the-move operation.

DESCRIPTION: Multispectral and polarimetric sensors have been used for material imaging (LeMaster, et al; 2013) and target detection (Hubbard, et al; 2008) for improved contrast and lower false-alarm rates with detection and identification. Visual to Near-IR (VNIR) polarization has been successfully used for littoral minefield detection, while polarimetry has been investigated for buried and surface mine detection (Ackenhusen, 2001). A pixel pitch-matched SWIR polarization camera would be an improvement over conventional SWIR polarimetric imaging methods, such as spinning filter wheels or multiple sensor approaches, which are not optimal for on-the-move operation and which often suffer from variable image registration issues that lead to changing polarization artifacts. The Bayer-type array has fixed artifacts that can be undone by standard color interpolation techniques. The polarizer grid approach requires a precision alignment of a micro-grid polarizer in both pitch and angle to the sensor focal plane array. Each "super pixel" of the polarizer array should consist of four sub pixels that produce different pixel polarization states (comprising a representative subset of the Stokes parameters). When a distant object is imaged onto a super pixel, the complete linear polarization state of the incoming light can be measured.

The goals of this project are to develop and demonstrate an uncooled InGaAs camera for actively imaging polarization spectral response between 0.9 �m to 1.7 �m. The SWIR InGaAs micro-grid polarizer camera should be compact (approximate volume of 6 cubic inches) and rugged (functional shock and vibration) and must be usable at ambient temperatures -20 �C and above. The pixel pitch-matched polarizer grid should be attached to a state of the art focal plane array, preferably greater than 640 x 512 pixels, with state of the art noise reduction technology and dynamic range for an uncooled camera. The desired digital output is 12 bits with a minimum 30 frame per second (fps) frame rate. The desired voltage requirements are 8-16 volts DC with a desired power of <5W. Minimization of life cycle costs should be a design consideration.

PHASE I: The company will demonstrate technical feasibility of the concept in meeting Navy needs for an on-the-move polarimetric imaging capability in the short wave infrared. The company will prove the concept of a pixel-matched polarimetric camera in the laboratory by completing and reporting on the following tasks:

� Overall design for pixel pitch matched micro-grid for identified focal plane array

� Identification, development, and/or fabrication of micro-grids consistent with overall design

� Demonstration that the micro-grid meets the design requirement for the focal plane array, e.g., in spatial and polarimetric uniformity, with best possible extinction ratio for the individual elements (goal of 100:1)

PHASE II: Based on the results of Phase I effort, the small business will develop a Phase II prototype camera for evaluation. Expected activities are for the company to:

� Build and demonstrate the pixel pitch matched micro-grid onto an uncooled InGaAs focal plane array of required camera specifications (i.e, rugged, shock/vibration, temperature) with state-of-the-art noise and dynamic range capability. Demonstrate the polarimetric response within the defined spectral range using suitable calibration targets

� Iterate to improve design and performance

� Deliver prototype pixel pitch matched uncooled InGaAs camera of required specifications to the Navy for further evaluation

Naval Surface Warfare Center Panama City Division (NSWC PCD) will consult and provide applicable background information to the camera developer to support development of the prototype. NSWC PCD will collaborate with the awardee in determining the performance of the pixel- pitch matched uncooled InGaAs camera.

PHASE III DUAL USE APPLICATIONS: The small business will apply the knowledge gained in Phase II to build three copies of a prototype camera, suitably packaged for integration with a USMC land platform of the Navy�s choosing. The company will work with the Navy to characterize the camera's performance, integrate the camera on the designated USMC platform, and support field tests to verify the camera operation for various field applications. Market research and analysis shall identify the most promising technology areas and the company shall develop manufacturing plans to facilitate a smooth transition to the Navy. Ultimately, the goal is for the awardee to market such detectors to the infrared sensor community for applications of measurements of natural and man-made materials beyond the capabilities of unaided human vision.

REFERENCES:

1. U.S. patent 3971065, Bryce E. Bayer, "Color imaging array", issued 1976-07-20.

2. LeMaster, D.A., et al. SWIR active polarization imaging for material identification. (2013). Polarization Science and Remote Sensing, Proc. Of SPIE, Vol. 8873.

3. Hubbard, W., et al. Multispectral-Polarimetric Sensing for Detection of Difficult Targets. (2008, Electro-Optical and Infrared Systems: Technology and Applications V, Proc. Of SPIE, Vol 7113.

4. Ackenhusen, J.G. Infrared/Hyperspectral Methods (Paper II): Appendix D. Alternatives for Landmine Detection. 2001.

KEYWORDS: SWIR Camera; polarization; pixel-pitch matched; polarimetric imager

TPOC-1: Lee Mastroianni

Email: [email protected]

TPOC-2: Keith Aliberti

Email: [email protected]

TPOC-3: Jody Wood-Putnam

Email: [email protected]

Questions may also be submitted through DoD SBIR/STTR SITIS website.

** TOPIC AUTHOR (TPOC) **

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