Infrared Focal Plane Arrays have been developed with reductions in pixel size below the Nyquist limit imposed by the optical systems Point Spread Function (PSF). These smaller sub diffraction limited pixels allows spatial oversampling of the image. We show that oversampling the PSF allows improved fidelity in imaging, resulting in sensitivity improvements due to pixel correlation, reduced false alarm rates, improved detection ranges, and an improved ability to track closely spaced objects.
KEYWORDS: Sensors, Point spread functions, Interference (communication), Target detection, Imaging systems, Modulation, Signal to noise ratio, Monte Carlo methods, Readout integrated circuits, Image resolution
Infrared Focal Plane Arrays have been developed with reductions in pixel size below the Nyquist limit
imposed by the optical systems Point Spread Function (PSF). These smaller sub diffraction limited pixels
allows spatial oversampling of the image. We show that oversampling the PSF allows improved fidelity
in imaging, resulting in sensitivity improvements due to pixel correlation, reduced false alarm rates,
improved detection ranges, and an improved ability to track closely spaced objects.
KEYWORDS: Sensors, Point spread functions, Target detection, Interference (communication), Signal to noise ratio, Modulation, Readout integrated circuits, Infrared sensors, Photons, Monte Carlo methods
Cyan Systems has recently developed an approach to focal plane assembly (FPA) architecture which represent a significant advancement in information extraction from the data as it is being collected. This approach utilizes sub-pixels which achieve a high degree of oversampling of the sensors Point Spread Function (PSF), well beyond the Nyquist limit for a critically sampled sensor. The data contained in an oversampled image has the obvious advantage of readily discriminating between focal plane and object generated artifacts as the first step in false alarm rejection. This effect is particularly useful at identification of radiation events. However there are further advantages that can be exploited through nearest neighbor subpixel correlation, and pooling that achieves significant noise reduction and therefore improved sensitivity. In Cyan’s architecture these processes are accomplished for the first time at the input to the preamp in the ROIC. This approach not only allows improved fidelity in imaging, but further reduces false alarm rates, improves detection ranges, and demonstrates an improved ability to track closely spaced objects. The small pixels that enable this approach also ensure improved radiation hardness reducing the capture cross section. The architecture has been modeled and simulations run which illustrate the dramatic improvements possible.
KEYWORDS: Point spread functions, Sensors, Signal to noise ratio, Interference (communication), Target detection, Imaging systems, Photons, Modulation, Infrared sensors, Monte Carlo methods
Infrared Focal Plane Arrays have been developed with reductions in pixel size below the Nyquist limit imposed by the optical systems Point Spread Function (PSF). These smaller sub diffraction limited pixels allows spatial oversampling of the image. We show that oversampling the PSF allows improved fidelity in imaging, resulting in sensitivity improvements due to pixel correlation, reduced false alarm rates, improved detection ranges, and an improved ability to track closely spaced objects.
This paper describes recent results from the Extremely High Temperature Photonic Crystal
System Technology (XTEMPS) technology program. The XTEMPS program has developed a
Photonic Crystal (PhC) based high efficiency IR emitter array for use in the emerging generation
of wide field of view high performance scene projectors. Cyan's approach provides high
dynamic range, multispectral emission from SWIR to LWIR and is uniquely capable of
accurately simulating very realistic system spectral signatures. The PhC array is fabricated from
refractory materials to provide high radiance and long service lifetime. Cyan is teamed with
Sandia National Laboratories for design and fabrication of the emitter and with Nova sensors to
utilize their advanced Read In Integrated Circuit (RIIC). PhC based emitters show improved inband
output power efficiency when compared to broad band "graybody" emitters due to the
absence of out-of-band emission. Less electrical power is required to achieve high operating
temperature, and non-Lambertian emission pattern puts a large fraction of the emitted energy
into a straight ahead beam. Both effects significantly boost effective radiance output. Cyan has
demonstrated pixel designs compatible with Nova's medium format RIIC, which ensures high
apparent output temperatures with modest drive currents and low operating voltages of less than
five volts. Unit cell pixel structures for high radiative efficiency have been demonstrated and
arrays using PhC optimized for up to four spectral bands have been successfully patterned and
fabricated into high yield wafers.
This paper describes results from the Extremely High Temperature Photonic Crystal System
Technology (XTEMPS) program. The XTEMPS program is developing projector technology
based on photonic crystals capable of high dynamic range, multispectral emission from SWIR to
LWIR, and realistic band widths. These Photonics Crystals (PhC) are fabricated from refractory
materials to provide high radiance and long device lifetime. Cyan is teamed with Sandia
National Laboratories, to develop photonics crystals designed for realistic scene projection
systems and Nova sensors to utilize their advanced Read In Integrated Circuit (RIIC). PhC based
emitters show improved in-band output power efficiency when compared to broad band
"graybody" emitters due to the absence of out-of-band emission. Less electrical power is
required to achieve high operating temperature, and the potential for nonequilibrium pumping
exists. Both effects boost effective radiance output. Cyan has demonstrated pixel designs
compatible with Nova's medium format RIIC, ensuring high apparent output temperatures,
modest drive currents, and low operating voltages of less than five volts. Unit cell pixel
structures with high radiative efficiency have been demonstrated, and arrays using PhC
optimized for up to four spectral bands have been successfully patterned.
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