Accurate radiometric calibration of IR sources can be challenging, but is required for advanced sensors being used today. Santa Barbara Infrared has developed a new test facility to provide spectro-radiometric calibration of extended area sources. The station comprises a Bruker Invenio Fourier transform infrared spectrometer or FTIR, a NIST-traceable, high-emissivity DB-04 blackbody reference and an automated stage for switching between the reference source and unit under test. The system uses a series of differential measurements to perform the radiometric calibration. The first output of the calibration is a spectral emissivity that can be used to calculate output radiance based on the temperature as measured in the well of the blackbody source. The second output of the calibration is a derived gradient term allowing the calculation of the temperature of the surface of the source based on the temperature of the thermometric measurement well and the temperature of the ambient environment. The additional gradient term allows for improved radiometric accuracy when operating at source and environment temperatures different from those at which the source was calibrated.
The development of very-large format infrared detector arrays has challenged the IR scene projector community to develop larger-format infrared emitter arrays. Many scene projector applications also require much higher simulated temperatures than can be generated with current technology. This paper will present an overview of resistive emitterbased (broadband) IR scene projector system development, as well as describe recent progress in emitter materials and pixel designs applicable for legacy MIRAGE XL Systems to achieve apparent temperatures >1000K in the MWIR. These new high temperature MIRAGE XL (LFRA) Digital Emitter Engines (DEE) will be “plug and play” equivalent with legacy MIRAGE XL DEEs, the rest of the system is reusable. Under the High Temperature Dynamic Resistive Array (HDRA) development program, Santa Barbara Infrared Inc. (SBIR) is developing a new infrared scene projector architecture capable of producing both very large format (>2k x 2k) resistive emitter arrays and improved emitter pixel technology capable of simulating very high apparent temperatures. During earlier phases of the program, SBIR demonstrated materials with MWIR apparent temperatures in excess of 1500 K. These new emitter materials can be utilized with legacy RIICs to produce pixels that can achieve 7X the radiance of the legacy systems with low cost and low risk. A 'scalable' Read-In Integrated Circuit (RIIC) is also being developed under the same HDRA program to drive the high temperature pixels. This RIIC will utilize through-silicon via (TSV) and Quilt Packaging (QP) technologies to allow seamless tiling of multiple chips to fabricate very large arrays, and thus overcome the yield limitations inherent in large-scale integrated circuits. These quilted arrays can be fabricated in any N x M size in 512 steps.
Many existing and emerging remote sensing applications in the UV, Visible, NIR, SWIR, MWIR and LWIR regions are challenging the conventional thinking of radiance and temperature calibration techniques. While the relationship between blackbody temperature and optical radiation is well understood, often there is an “invisible” dividing line between treatments of these values as either optical radiance or temperature. It is difficult to perform seamless temperature and radiance calibrations across the point of 2.5um. Spectrum above 2.5um is typically related in temperature terms and below 2.5um may be either spoken of in terms of temperature or optical radiance. There is also a natural unit “convergence” issue at 2.5um, due to the crossover of significant levels of emissivity, reflectance and temperature at this point. NMI traceability in the spectral region of 2.5-14.0um can also be a problem especially for spectral radiance. This paper will outline a possible turn-key test bench solution that provides traceable solutions for both temperature and radiance value in these regimes. The intent of this paper is to offer a possible solution and challenge the infrastructure that exists today over the 0.3-14um range in order to obtain a valid spectral radiance or temperature value, or both, to support emerging sensor fusion technology.
The rapid development of very-large format infrared detector arrays has challenged the IR scene projector community
to also develop larger-format infrared emitter arrays to support the testing of systems incorporating these detectors.
In addition to larger formats, many scene projector users require much higher simulated temperatures than can be
generated with current technology in order to fully evaluate the performance of their systems and associated processing
algorithms.
Under the Ultra High Temperature (UHT) development program, Santa Barbara Infrared Inc. (SBIR) is developing a
new infrared scene projector architecture capable of producing both very large format (>1024 x 1024) resistive emitter
arrays and improved emitter pixel technology capable of simulating very high apparent temperatures. During earlier
phases of the program, SBIR demonstrated materials with MWIR apparent temperatures in excess of 1400 K. New
emitter materials have subsequently been selected to produce pixels that achieve even higher apparent temperatures.
Test results from pixels fabricated using the new material set will be presented and discussed. A 'scalable' Read In
Integrated Circuit (RIIC) is also being developed under the same UHT program to drive the high temperature pixels.
This RIIC will utilize through-silicon via (TSV) and Quilt Packaging (QP) technologies to allow seamless tiling of
multiple chips to fabricate very large arrays, and thus overcome the yield limitations inherent in large-scale integrated
circuits. Results of design verification testing of the completed RIIC will be presented and discussed.
Next-generation Infrared Focal Plane Arrays (IRFPAs) are demonstrating ever increasing frame rates, dynamic range,
and format size, while moving to smaller pitch arrays.1 These improvements in IRFPA performance and array format
have challenged the IRFPA test community to accurately and reliably test them in a Hardware-In-the-Loop environment
utilizing Infrared Scene Projector (IRSP) systems. The rapidly-evolving IR seeker and sensor technology has, in some
cases, surpassed the capabilities of existing IRSP technology.
To meet the demands of future IRFPA testing, Santa Barbara Infrared Inc. is developing an Infrared Light Emitting
Diode IRSP system. Design goals of the system include a peak radiance >2.0W/cm2/sr within the 3.0-5.0μm waveband,
maximum frame rates >240Hz, and >4million pixels within a form factor supported by pixel pitches ≤32μm. This paper
provides an overview of our current phase of development, system design considerations, and future development work.
Santa Barbara Infrared (SBIR) is continually developing improved methods for non-uniformity correction (NUC) of its Infrared Scene Projectors (IRSPs) as part of its comprehensive efforts to achieve the best possible projector performance. The most recent step forward, Advanced Iterative NUC (AI-NUC), improves upon previous NUC approaches in several ways. The key to NUC performance is achieving the most accurate possible input drive-to-radiance output mapping for each emitter pixel. This requires many highly-accurate radiance measurements of emitter output, as well as sophisticated manipulation of the resulting data set. AI-NUC expands the available radiance data set to include all measurements made of emitter output at any point. In addition, it allows the user to efficiently manage that data for use in the construction of a new NUC table that is generated from an improved fit of the emitter response curve. Not only does this improve the overall NUC by offering more statistics for interpolation than previous approaches, it also simplifies the removal of erroneous data from the set so that it does not propagate into the correction tables. AI-NUC is implemented by SBIR’s IRWindows4 automated test software as part its advanced turnkey IRSP product (the Calibration Radiometry System or CRS), which incorporates all necessary measurement, calibration and NUC table generation capabilities. By employing AI-NUC on the CRS, SBIR has demonstrated the best uniformity results on resistive emitter arrays to date.
Infrared scene projectors (IRSPs) are a key part of performing dynamic testing of infrared (IR) imaging systems. Two important properties of an IRSP system are apparent temperature and thermal resolution. Infrared scene projector technology continues to progress, with several systems capable of producing high apparent temperatures currently available or under development. These systems use different emitter pixel technologies, including resistive arrays, digital micro-mirror devices (DMDs), liquid crystals and LEDs to produce dynamic infrared scenes. A common theme amongst these systems is the specification of the bit depth of the read-in integrated circuit (RIIC) or projector engine , as opposed to specifying the desired thermal resolution as a function of radiance (or apparent temperature). For IRSPs, producing an accurate simulation of a realistic scene or scenario may require simulating radiance values that range over multiple orders of magnitude. Under these conditions, the necessary resolution or “step size” at low temperature values may be much smaller than what is acceptable at very high temperature values. A single bit depth value specified at the RIIC, especially when combined with variable transfer functions between commanded input and radiance output, may not offer the best representation of a customer’s desired radiance resolution. In this paper, we discuss some of the various factors that affect thermal resolution of a scene projector system, and propose some specification guidelines regarding thermal resolution to help better define the real needs of an IR scene projector system.
The rapid development of very-large format infrared detector arrays has challenged the IR scene projector community to develop correspondingly larger-format infrared emitter arrays to support the testing needs of systems incorporating these detectors. As with most integrated circuits, fabrication yields for the read-in integrated circuit (RIIC) that drives the emitter pixel array are expected to drop dramatically with increasing size, making monolithic RIICs larger than the current 1024x1024 format impractical and unaffordable. Additionally, many scene projector users require much higher simulated temperatures than current technology can generate to fully evaluate the performance of their systems and associated processing algorithms. Under the Ultra High Temperature (UHT) development program, Santa Barbara Infrared Inc. (SBIR) is developing a new infrared scene projector architecture capable of producing both very large format (>1024x1024) resistive emitter arrays and improved emitter pixel technology capable of simulating very high apparent temperatures. During an earlier phase of the program, SBIR demonstrated materials with MWIR apparent temperatures in excess of 1000K. New emitter materials have subsequently been selected to produce pixels that achieve even higher apparent temperatures. Test results from pixels fabricated using the new material set will be presented and discussed. Also in development under the same UHT program is a 'scalable' RIIC that will be used to drive the high temperature pixels. This RIIC will utilize through-silicon vias (TSVs) and quilt packaging (QP) technologies to allow seamless tiling of multiple chips to fabricate very large arrays, and thus overcome the inherent yield limitations of very-large-scale integrated circuits. Current status of the RIIC development effort will also be presented.
High pixel temperatures for IR scene projector arrays face materials challenges of oxidation, diffusion, and recrystallization. For cost effective development of new high-temperature materials, we have designed and fabricated simplified pixels for testing. These consist of resistive elements, traces, and bond pads sandwiched between dielectric layers on Si wafers. Processing involves a pad exposure etch, a pixel outline etch, and an undercut etch to thermally isolate the resistive element from the substrate. Test pixels were successfully fabricated by electron-beam lithography using a combination of wet and dry etching.
To meet the needs of high fidelity infrared sensors, under the Ultra High Temperature (UHT) development program, Santa Barbara Infrared Inc. (SBIR) has developed new infrared emitter materials capable of achieving extremely high temperatures. The current state of the art arrays based on the MIRAGE-XL generation of scene projectors is capable of producing imagery with mid-wave infrared (MWIR) apparent temperatures up to 700K with response times of 5 ms. The Test Resource Management Center (TRMC) Test and Evaluation/Science and Technology (TandE/SandT) Program through the U.S. Army Program Executive Office for Simulation, Training and Instrumentations (PEO STRI) has contracted with SBIR and its partners to develop a new resistive array based on these new materials, using a high current Read-In Integrated Circuit (RIIC) capable of achieving higher temperatures as well as faster frame rates. The status of that development will be detailed within this paper, including performance data from prototype pixels.
Several new technologies have been developed over recent years that make a fundamental change in the scene projection for infrared hardware in the loop test. Namely many of the innovations are in Read In Integrated Circuit (RIIC) architecture, which can lead to an operational and cost effective solution for producing large emitter arrays based on the assembly of smaller sub-arrays. Array sizes of 2048x2048 and larger are required to meet the high fidelity test needs of today’s modern infrared sensors. The Test Resource Management Center (TRMC) Test and Evaluation/Science and Technology (T and E/S and T) Program through the U.S. Army Program Executive Office for Simulation, Training and Instrumentations (PEO STRI) has contracted with SBIR and its partners to investigate integrating new technologies in order to achieve array sizes much larger than are available today. SBIR and its partners have undertaken several proof-of-concept experiments that provide the groundwork for producing a tiled emitter array. Herein we will report on the results of these experiments, including the demonstration of edge connections formed between different ICs with a gap of less than 10µm.
We report on the design and testing of a 2-color dynamic scene projector system based on the MIRAGE-XL infrared scene projector. The system is based on the optical combination of two 1024x1024 MIRAGE-XL resistive arrays. Algorithms derived for 2-color operation are discussed and system performance data is presented, including radiometric performance, sub-pixel spatial co-registration and compensation for spectral cross-talk.
SBIR is developing an enhanced blackbody for improved radiometric testing. The main feature of the blackbody is an improved coating with higher emissivity than the standard coating used. Comparative measurements of the standard and improved coatings are reported, including reflectance. The coatings were also tested with infrared imagers and a broadband emissivity estimate derived from the imagery data. In addition, a control algorithm for constant slew rate has been implemented, primarily for use in minimum resolvable temperature measurements. The system was tested over a range of slew rates from 0.05 K/min to 10 K/min and its performance reported.
The Ultra High Temperature (UHT) development program will develop, package, and deliver high temperature scene
projectors for the U.S. Government. The Infrared Scene Projector (IRSP) systems goals are to be capable of extremely
high temperatures, in excess of 2000K, as well as fast frame rates, 500 Hz, and 2 ms rise times. The current status of the
pixel design will be discussed with an emphasis on the models developed to facilitate these designs and estimate
performance prior to fabrication.
Non-uniformity correction (NUC) of emitter arrays is an important part of the calibration of an infrared scene
projector (IRSP), necessary to provide precise and artifact-free simulations. Producing an accurate and cost effective
NUC of an IRSP is a challenge due to the complexity of the NUC process and the expense of high performance, large
format infrared cameras. Previous NUC methods have typically fallen into either the sparse grid method or the flood
method. The sparse grid method gives independent measurements of each emitter pixel, however, it is time consuming
and becomes impractical for accurate measurements at low radiance levels, especially with lower performance but less
expensive cameras such as microbolometers. Flood measurements are fast and can be applied at lower radiance, but
do not allow precise measurement of the output of an individual pixel. Santa Barbara Infrared (SBIR) has developed a
hybrid approach that makes use of both methods. Sparse grid methods are used at higher radiance levels to perform an
initial NUC of the array. Then, a combination of flood and sparse grid data is used to extend the NUC to lower
radiance levels and improve the high radiance NUC through iteration. Details of the approach and results from its
application to an emitter array are presented.
KEYWORDS: Nonuniformity corrections, Projection systems, High dynamic range imaging, Mid-IR, Temperature metrology, Optical resolution, Resistance, Infrared radiation, Light emitting diodes, Control systems
Achieving very high apparent temperatures is a persistent goal in infrared scene projector (IRSP) design. Several
programs are currently under way to develop technologies for producing high apparent temperatures. Producing a
useful system capable of reproducing high fidelity scenes across a large range of apparent temperatures requires more
than just a high temperature source. The entire scene projection system must support the extended dynamic range of
the desired scenarios. Supporting this extended range places requirements on the rest of the system. System
resolution and non-uniformity correction (NUC) are two areas of concern in the development of a high dynamic range
IRSP. We report the results of some initial investigations into the resolution required for acceptable system
performance and the effects of moving to a higher dynamic range may put on existing NUC procedures.
Santa Barbara Infrared (SBIR) produces high performance resistive emitter arrays for its line of IR Scene Projector
(IRSP) products. These arrays operate in modes supporting up to 400 hertz frame rates. The physical properties of the
microelectromechanical emitter pixel structures cause the transition times for temperature slewing to be well over the
2.5 milliseconds required to support 400 hertz operation. This paper expands on a study previously conducted by
SBIR to determine the maximum capability of a technique in which the pixel drive of the first frame of a commanded
transition is modified to improve transition time. This technique is referred to as overdrive and in this study it was
effective in reducing rise and fall times from as much as 6 milliseconds to 2 milliseconds.
Performing a good non-uniformity correction is a key part of achieving optimal performance from an infrared scene
projector, and the best NUC is performed in the band of interest for the sensor being tested. While cooled, large format
MWIR cameras are readily available and have been successfully used to perform NUC, similar cooled, large format
LWIR cameras are not as common and are prohibitively expensive. Large format uncooled cameras are far more
available and affordable, but present a range of challenges in practical use for performing NUC on an IRSP. Some of
these challenges were discussed in a previous paper. In this discussion, we report results from a continuing development
program to use a microbolometer camera to perform LWIR NUC on an IRSP. Camera instability and temporal response
and thermal resolution were the main problems, and have been solved by the implementation of several compensation
strategies as well as hardware used to stabilize the camera. In addition, other processes have been developed to allow
iterative improvement as well as supporting changes of the post-NUC lookup table without requiring re-collection of the
pre-NUC data with the new LUT in use.
Usage of image intensified (I2) and other low light level devices have grown considerably over the past decade1,2 As the
systems have become more common place, the demand for production line test equipment has also grown. Accurate
measurements of device response are a key part of determining acceptable system operation. However, differences in the
spectral response of the unit under test (UUT) devices and the control detector; and the spectral distribution of the
source, can lead to errors in test accuracy. These errors can be compounded by spectral variation in the source (or color
temperature shifts) as a function of attenuation. These issues are often further confused by test system requirements that
are not consistent with the desired parameter to be measured. For example, source requirements are often specified in
illuminance while the UUT actually measures irradiance. We report on the calibration of a large dynamic range light
source test system (> 7 orders), and discuss output compensation approaches for systems which control in a band
different than the UUT being tested.
Test Program Set (TPS) software development for Electro-Optical (EO) testing has traditionally been an expensive and
lengthy process. A major cause of this has been the development of new test executive software on an ad hoc basis for
each program. Furthermore, there have typically been different needs for production versus lab environments with
production needing a set of standard tests, while users in a lab environment requiring the capability to modify certain
aspects of their tests as needed. At Santa Barbara Infrared, a new architecture for TPS development has been engineered
that addresses these concerns. The new architecture can host a complete TPS development environment that eliminates
the need for a separate test executive. It supports EO testing in both engineering development and production testing
through the use of user editable test scripts along with distinct user accounts and privileges. The new architecture is unit
under test (UUT) centric, allowing a user to define UUT parameters once and easily share the results between tests. In
this article we will review the new architecture and give examples of TPS development under that architecture.
Performing a good non-uniformity correction is a key part of achieving optimal performance from an infrared scene
projector. Ideally, NUC will be performed in the same band in which the scene projector will be used. Cooled, large
format MWIR cameras are readily available and have been successfully used to perform NUC, however, cooled large
format LWIR cameras are not as common and are prohibitively expensive. Large format uncooled cameras are far more
available and affordable, but present a range of challenges in practical use for performing NUC on an IRSP. Santa
Barbara Infrared, Inc. reports progress on a continuing development program to use a microbolometer camera to perform
LWIR NUC on an IRSP. Camera instability and temporal response and thermal resolution are the main difficulties. A
discussion of processes developed to mitigate these issues follows.
Electro Optical technology continues to advance, incorporating developments in infrared and laser technology into
smaller, more tightly-integrated systems that can see and discriminate military targets at ever-increasing distances. New
systems incorporate laser illumination and ranging with gated sensors that allow unparalleled vision at a distance. These
new capabilities augment existing all-weather performance in the mid-wave infrared (MWIR) and long-wave infrared
(LWIR), as well as low light level visible and near infrared (VNIR), giving the user multiple means of looking at targets
of interest. There is a need in the test industry to generate imagery in the relevant spectral bands, and to provide
temporal stimulus for testing range-gated systems. Santa Barbara Infrared (SBIR) has developed a new means of
combining a uniform infrared source with uniform laser and visible sources for electro-optics (EO) testing. The source
has been designed to allow laboratory testing of surveillance systems incorporating an infrared imager and a range-gated
camera; and for field testing of emerging multi-spectral/fused sensor systems. A description of the source will be
presented along with performance data relating to EO testing, including output in pertinent spectral bands, stability and
resolution.
The modulation transfer function (MTF) of optical systems is often derived by taking the Fourier transform (FT) of a
measured line spread function. Recently, methods of performing Fourier transforms that are common in infrared
spectroscopy have been applied to MTF calculations. Proper apodization and phase correction have been shown to
improve MTF calculations in optical systems. In this paper these methods as well as another filtering algorithm based
on phase are applied to under-sampled optical systems. Results, both with and without the additional processing are
presented and the differences are discussed.
Santa Barbara Infrared (SBIR) produces high performance resistive emitter arrays for its line of IR
Scene Projectors (IRSPs). These arrays operate at frame rates up to 200 hertz. The inherent
properties of the pixels can result in transitions between two temperatures that are more than the 5
millisecond frame time. Modifying the pixel drive level on a frame by frame basis can lead to
improvements in the measured rise times. This paper describes a new capability developed by SBIR
that improves the rise time of the pixels. It discusses the process by which array drive levels are
modified to achieve quicker transitions together with test results showing improved rise time. In an
example transition cited here, the risetime is reduced by more than a factor of two from 8.3 ms to 3.7
ms.
MIRAGE WF is the latest high definition version of the MIRAGE infrared scene projector product line from Santa
Barbara Infrared Inc. (SBIR). MIRAGE WF is being developed under the Wide Format Resistive Array (WFRA)
program. The WFRA development is one of several efforts within the Infrared Sensor Simulator - Preplanned Product
Improvement (IRSS P3I) umbrella funded by the Central Test and Evaluation Investment Program (CTEIP) and led by
the US Navy at Patuxent River, MD. Three MIRAGE WF infrared scene projection systems are being delivered as part
of the WFRA program. The main differences between the MIRAGE XL (1024x1024) and MIRAGE WF are a 1536x768
emitter array and 100Hz true raster capability. The key emitter requirements that have been measured and will be
discussed include: Operability, Maximum Apparent Temperature, Rise Time and Array Uniformity. Key System
specifications are: 1536x768 pixels, maximum apparent temperature of 600K, maximum frame rate of 100Hz, raster and
snap shot updating, radiance rise and fall time less than 5 ms and windowed mode (1024x768) operation at up to 200 Hz.
Polarization is increasingly being considered as a method of discrimination in passive sensing applications. In this paper
the degree of polarization of the thermal emission from the emitter arrays of two new Santa Barbara Infrared (SBIR)
micro-bolometer resistor array scene projectors was characterized at ambient temperature and at 77 K. The emitter
arrays characterized were from the Large Format Resistive Array (LFRA) and the Optimized Arrays for Space-Background Infrared Simulation (OASIS) scene projectors. This paper reports the results of this testing.
KEYWORDS: Modulation transfer functions, Apodization, Fourier transforms, Optical transfer functions, Signal to noise ratio, Phase shift keying, Sensors, Systems modeling, Infrared spectroscopy, Algorithm development
Fourier transform methods common in infrared spectroscopy were applied to the problem of calculating the modulation
transfer function (MTF) from a system's measured line spread function (LSF). Algorithms, including apodization and
phase correction, are discussed in their application to remove unwanted noise from the higher frequency portion of the
MTF curve. In general, these methods were found to significantly improve the calculated MTF. Apodization reduces
the proportion of noise by discarding areas of the LSF where there is no appreciable signal. Phase correction
significantly reduces the rectification of noise that occurs when the MTF is calculated by taking the power spectrum of
the complex optical transfer function (OTF).
Santa Barbara InfraRed (SBIR) is producing high performance 1,024 x 1,024 Large Format Resistive emitter Arrays
(LFRA) for use in the next generation of IR Scene Projectors (IRSPs). The demands of testing modern infrared imaging
systems require higher temperatures and faster frame rates. New emitter pixel designs, rise time enhancement techniques
and a new process for annealing arrays are being applied to continually improve performance. This paper will discuss the
advances in pixel design, rise time enhancement techniques and also the process by which arrays are annealed. Test
results will be discussed highlighting improvements in rise time, uniformity and reduced numbers of defective pixels.
SBIR has passed the midpoint of delivering ten 1024x1024 IR Scene Projector Systems (IRSPs) to the Government. Six systems have been installed at Redstone Technical Test Center (RTTC), Patuxent River, and Edwards Air Force Base. Four more systems are in production and will be shipped by the end of this year. The commercial name of the LFRA IRSP is Mirage XL. This ground breaking projector technology is being leveraged on the Wide Format Resistive Array (WFRA) program and on the Mirage II product. The WFRA IRSP, also known as Mirage HD, features an even larger 1536x768 emitter array and will be in system integration by the end of the year. Mirage II, which also leverages LFRA, is being readied as the next generation 512x512 projector system.
Additional signal processing capabilities have been installed in the LFRA systems. Each system now has full Translation/Rotation Processing (TRP) capability. Systems also have image convolution and 400Hz 1024x512 windowing capabilities.
KEYWORDS: Cryogenics, Analog electronics, Electronics, Prototyping, Packaging, Interfaces, Mid-IR, Digital electronics, Microelectromechanical systems, Temperature metrology
SBIR has completed the development of the first lot of OASIS emitter arrays and custom packaging for cryogenic IR scene projection applications. OASIS performance requirements include a maximum MWIR apparent temperature of greater than 600 K, with 10-90% radiance rise time of less than 6.5 ms. Four (4) arrays have been packaged, integrated, tested and delivered.
This paper will report on the first measurements taken of the OASIS resistive emitter arrays at both ambient and cryogenic temperatures. This paper will also provide a discussion of the OASIS cryogenic projector/electronics module (Cryo-PEM) design. We will also describe the novel thermal design employed within the array package and Cryo-PEM assemblies, which allows OASIS to produce radiometrically accurate imagery with reduced thermal lag/gradient artifacts compared to legacy Honeywell cryogenic IRSP assemblies. As OASIS supports both analog and digital input, we will discuss the differences between the two modes in terms of system integration, support electronics and overall array performance.
SBIR has completed development of the Large Format Resistive Array (LFRA) Infrared Scene Projector (IRSP) and shipped the first production system. Nine more systems are in production and will be shipped to several US Government customers on approximately six week centers. The commercial name of the LFRA IRSP is Mirage XL. System performance meets a broad range of program requirements and SBIR has been extremely successful in producing this ground breaking projector. Tests performed on System #1 reveal broad compliance to the specification and, in particular, outstanding emitter array performance. Key emitter requirements that have been met or exceeded include Operability, Maximum Apparent Temperature, and Array Uniformity. Key System specifications are:
Large-format emitter array (1024x1024);
High maximum apparent temperature (>700K);
200 Hz full-frame operation;
400 Hz static window mode (1024x512);
Non Uniformity (uncorrected) <10%.
SBIR has completed design and development of prototype emitter arrays and is completing custom cryogenic vacuum device packaging and support electronics for the Optimized Arrays for Space-background Infrared Simulation (OASIS) program. The OASIS array is a 512 x 512 device featuring high output dynamic range, a selectable analog/digital scene data interface, and the capability to operate from cryogenic to ambient substrate temperatures - thereby providing an enabling technology for projection of simulated radiance of space-background scenes. Prototype emitter production has been completed at RTI International in support of initial deliveries. The OASIS array package incorporates novel electrical bussing schemes optimized for the OASIS RIIC and a modular architecture to allow user re-configuration of both window and emitter shield. The OASIS package leverages LFRA operation features, and supports both ambient and cryogenic chamber-based operation with a minimum of mechanical and electrical re-configuration. The OASIS close support electronics (CSE) supports both analog and digital input data modes, while providing easy electronic connection between arrays installed in the cryogenic chamber and the external control and scene-generation systems. We present a technical overview of the OASIS array/package and CSE designs, and will report on measured radiometric performance from prototype OASIS arrays.
SpecTIR Corporation has constructed a second copy of their HyperSpecTIR (HST) instrument, with modifications made to various mechanical, electrical, and optical systems. The first instrument (HST1) has been operating for several years aboard multiple platforms, and a sizable archive of imagery has been generated. Using this archive as a baseline, HST2 data have been evaluated to measure expected performance gains versus actual gains. The basic instrument specifications remain unchanged: 227 unique spectral channels from 450 - 2450nm with 8-12nm FWHM, 1 milliradian IFOV, 256 element cross-track scanning, up to 14 bit digitization, and beam steering optics for image stabilization. Notable changes in HST2 include AR coating of the SWIR FPA, miniaturization of the electronics, and integration of control and data processing computers within the sensor so that it may be used in a pod or UAV. Sufficiently clear data over a single study area does not exist, so data from the spectrally similar areas of Cuprite and Goldfield, Nevada are used to compare the performance of the two instruments. While AR coating of the SWIR focal plane and other improvements to HST2 have improved signal-to-noise performance, these gains are traded off for a shorter integration time allowing for faster and a greater volume of data collection. An attempt to objectively measure spectral image data quality using spectral similarity values and determining the inherent dimensionality of the data reveal similar spectral performance of the instruments under present operational modes.
The scan mechanism of the HyperSpecTIR hyperspectral instrument has been modified to allow BRDF measurements from an airborne platform. The HyperSpecTIR is a flexible, airborne hyperspectral imager capable of on-the-fly programmability. Such measurements afford the opportunity to study geometric and spectral properties of natural scenes such as fields and canopies, as well as man-made substances such as composite materials and paints. As a proof of concept study for the BRDF measurement method, data was collected during flight operations near Phoenix Arizona. The measurements were performed in the principle plane and included the solar hot-spot. Detailed descriptions of the instrument and data collection methods are presented. The collected data is analyzed and compared to BRDF models of the solar hot-spot.
The identification of terrestrial objects using hyperspectral measurements is confounded by the influence of the intervening atmosphere that can obscure spectral features through gaseous line absorption and reduce contrast as a result of scattering by aerosols. Although hyperspectral measurements provide an effective source for the estimation of the amount of water vapor the estimate of aerosol properties using spectral radiances is much more uncertain. This
deficiency can be remedied by making polarimetric measurements which allow a more accurate and complete retrieval of aerosol properties over land than simple radiance measurements. As a proof of this concept we have made measurements of known ground targets with the HyperSpecTIR (HST), a flexible, airborne hyperspectral imager capable
of on-the-fly programmability and the Research Scanning Polarimeter (RSP). Measurements were made both in the mountains near Santa Barbara and at lower altitude near Buellton. The collected data is analyzed, atmospherically corrected and compared to the known spectral reflectance of the ground targets. The capabilities and deficiencies of the measurements, analysis and atmospheric correction technique are discussed.
Accurate multi-spectral, multi-angle polarimetric measurements are a key remote sensing tool for the determination of the burden and microphysical properties of atmospheric aerosols and, as an adjunct, for the correction of these atmospheric effects in spectroradiometric remote sensing applications. This paper describes the performance of the Research Scanning Polarimeter (RSP), provides examples of using the RSP for aerosol remote sensing, and assesses the potential synergy between spectroradiometric and polarimetric measurements.
In this paper tradeoffs between speed and accuracy for the atmospheric correction of hyperspectral imagery are examined. Among the issues addressed are: the use of scattering calculations on a sparse spectral grid and consequent accuracy and speed tradeoffs; methods of minimizing the required number quadrature points in multiple scattering calculations; effects of the vertical profiles of aerosols and absorbing gases on atmospheric correction; and efficient approaches from including the effects of sensor variability, or imperfections, on atmospheric correction.
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