Traditional performance metrics for hyperspectral imaging (HSI) systems include signal-to-noise ratio (SNR), ground sample distance (GSD), ground resolvable distance (GRD), and noise equivalent spectral radiance (NESR). These metrics characterize the sensor system itself, but there is a gap between these metrics and the ability of the system to detect and identify targets in realistic scenes. Three additional metrics, the target size to GRD ratio, target spectral variability and receiver operating characteristic (ROC) curve, are evaluated to quantify HSI system performance with scene and mission conditions considered. Historically, sensor design efforts do not use ROC curves because they are relatively difficult to calculate and depend on scene parameters as well as sensor parameters (e.g., SNR, GSD, GRD, and NESR).
Data from a recent experiment in which an airborne sensor collected data for a variety of targets are used to identify exploit performance factors that need to be included into the model to quantify end-to-end sensor exploit performance. The primary targets consisted of an array of blue tarpaulins cut to sizes less than and greater than one HSI spatial pixel projected to the ground. We designed the experiment to quantify and compare the effects of target size on ROC curves.
One key result of this work is that the radiance of targets in the scene exhibits a large degree of variation among many passes during two days of flight testing. This variability complicates the detection process. Another key result is that detection performance has a strong correlation with target size for subpixel targets. Finally, we demonstrate that in this case, sensor noise has little impact on detection performance.
When characterizing the imaging performance of tactical airborne imagers, one must account for the inherent subjectivity of human operators interpreting objects within a scene. One common approach to measuring imaging performance is the National Imagery Interpretability Rating Scale (NIIRS). However, the ground resolvable distance (GRD) is often a preferred metric because it can more easily be predicted through analysis, measured with field data, and traced to the laboratory measurements of system components. Although GRD is a calculable metric, it ultimately contains some ambiguity when linking it to an operator’s experience. Because of this, the ISR community sometimes utilizes different approaches to modeling and even measuring GRD. This can lead to confusion and disagreements when trying to compare the performance of different sensors. This paper explores different methods for modeling and measuring GRD. Emphasis is placed on airborne hyperspectral imaging (HSI) sensors. The additional spectral information provided by HSI sensors allows one to explore the relative importance of spatial resolution within the framework of HSI target detection capabilities. Modeled HSI performance will be validated against real world measurements performed with different airborne hyperspectral sensors. Different modeling and measurement approaches will be evaluated based on flight imagery, and the relative strengths and weaknesses of these different approaches will be discussed. In particular, a new model is presented, which is based on methods from laser physics of measuring the width of the point spread function.
Hyperspectral Imaging (HSI) is finding utility in many new areas, such as environmental and agricultural monitoring, medicine and food technology, industrial inspection, land management, and defense usage, due to its ability to simultaneously collect both spatial and spectral information. Within the tropical environment the utility of HSI has been demonstrated through various rain forest and coastal environmental programs.
System performance for all HSI systems is influenced by many factors, including environmental conditions, operational usage, internal system composition and the processing chain. Truly optimizing this performance requires an understanding of the operational conditions under which each system will perform. One of the key factors affecting system performance, especially at long stand-off ranges, is the atmospheric effects. This paper presents analytical results demonstrating the effects of atmospheric conditions on long stand-off airborne HSI systems based on a Raytheon developed performance model for estimating System performance.
This end-to-end System Performance Model is especially designed for long stand-off airborne detection with large off-nadir viewing angles. It takes into account most of the components within the entire imaging chain. The model divides the end-to-end imaging chain into three parts: the environmental component, the Concept of Operations (CONOPS), and the imaging system effects. The environmental component includes solar illumination, reflectance of materials on the ground, scattering, and atmospheric transmittance. The system component includes the effects of system noise and throughput. The CONOPS accounts for the various operating conditions best suited for long stand-off detection. The analytical results presented in this paper provide details on the influence of the atmospheric conditions, including tropical conditions, on NESR and SNR performance in a Spot Mode CONOPS for a HSI system based on the end-to-end System Performance Model. These results are based on continued work developed from the “Long stand-off Performance Modelling of HSI Airborne Imaging Systems”.
We describe a compact, multi-sensor design architecture capable of providing both spectral-polarimetric imaging and
adaptive matched filter target detection in real-time. The sensor suite supports airborne broad-area search missions using
multiple large-format, high speed TDI scanning sensors. The technology approach leverages Micro-Electro-Mechanical
System (MEMS) based spectral imaging systems and scanning TDI arrays originally developed for space based remote
sensing. The MEMS spectrometer system can dynamically select and switch linear combinations of single or multiple
VNIR/SWIR spectral bands with 5nm sampling resolution using a programmable MEMS mirror. The MEMS spectral
filter is capable of providing high quality spectral filtering across a large format sensor with > 1MHz optical switching &
update speeds. A dual instrument sensor suite architecture called the "PRISM sensor" has been developed which is based
on this technology and provides simultaneous spectral-polarimetric imaging and matched filter target tracking with
minimal on-board computing requirements. We describe how this technology can simultaneously perform broad-area
imaging and target identification in near real-time with a simple threshold operation. Preliminary results are illustrated
as additional layer of target-discriminate geospatial information that may be fused with geo-referenced imagery.
ITT Industries Space Systems Division and Eastman Kodak Company have developed a scalable, data- and power-efficient imaging spectrometer system with a digitally tunable optical filter capability, which enables the rapid selection of high-quality user-defined optical spectral band(s) of interest. The system utilizes a custom-designed, high-contrast diffractive MEMS device with 50 independent spectral switches at the image plane of a double-pass dispersive/de-dispersive
spectrometer. The custom MEMS device is based on grating electromechanical system (GEMS) display technology, which provides very high image contrast (2000:1), fast optical switching speeds (< 100 ns), and a large active area with a very high fill factor. The system enables the selection of arbitrary, narrow or wide spectral bands of interest across the visible spectrum with a sampling resolution of 5 nm, without any moving mechanical parts. The
resulting optical filter quality and performance is comparable to conventional fixed-band dichroic filters used in current remote sensing systems. The brassboard systems are designed for rapid transition to space-based, electro-optical (EO) remote sensing missions that utilize large format linear TDI scanning sensors and large format area staring arrays in the visible band. This technology addresses numerous capabilities to meet future EO system requirements for rapidly selecting and utilizing a high quality imaging optical bandpass of interest. The system concept provides capability for a
>20X scan rate advantage over conventional hyperspectral imagers as a result of the compatibility with TDI scanning. The image quality is comparable to current MSI and HSI systems.
Brightness and color resolution, wider viewing angles, lower power consumption, and a thin aspect ratio are all well understood physical characteristics of organic light emitting diode (OLED) displays, an up-and-coming flat panel displays. Increasing numbers of applications of flat panel displays are being commercialized with touch screens. This paper will describe the optical characteristics of mating a touch screen with a full-color active matrix OLED display. We will quantify the OLED optical properties with respect to touch screens with matte finishes and anti-reflective topcoats, and with and without the use of a polarizer on the OLEDs top glass.
Organic LED (OLED) technology promises superior performance in brightness and color resolution, wider viewing angles, lower power consumption, thin displays, and robust physical characteristics. These advantages make OLED displays attractive for next-generation flat panel displays. This paper describes the state-of-the-art in OLED technology and addresses some of the benefits and difficulties facing the integration of OLED devices into a range of imaging equipment applications. We will review OLED performance from a systems perspective and will compare it to OLED material and panel properties. We will also describe the competitive attributes of a flat panel display and recent work done at Kodak on interfacing to OLED devices.
The continual need for microelectronic devices that operate under severe electronic and environmental conditions (high temperature, high frequency, high power, and radiation tolerance) has sustained research in wide bandgap semiconductor materials. The properties suggest these wide bandgap semiconductor materials have tremendous potential for military and commercial applications. High frequency bipolar transistors and field effect transistors, diodes, and short wavelength optical devices have been proposed using these materials. Although research efforts involving the study of transport properties in GaN and diamond have made significant advances, much work is still needed to improve the material quality so that the electrophysical behavior of device structures can be further understood and exploited. Electron beam induced current (EBIC) measurements can provide a method of understanding the transport properties in GaN and diamond. This technique basically consists of measuring the current or voltage transient response to the drift and diffusion of carriers created by a short-duration pulse of radiation. This method differs from other experiemental techniques because it is based on a fast transient electron beam created from a high- speed, laser-pulsed photoemission system.
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