42 Matching Results

Search Results

Advanced search parameters have been applied.

Automated coregistration of MTI spectral bands.

Description: In the focal plane of a pushbroom imager, a linear array of pixels is scanned across the scene, building up the image one row at a time. For the Multispectral Thermal Imager (MTI), each of fifteen different spectral bands has its own linear array. These arrays are pushed across the scene together, but since each band's array is at a different position on the focal plane, a separate image is produced for each band. The standard MTI data products resample these separate images to a common grid and produce coregistered multispectral image cubes. The coregistration software employs a direct 'dead reckoning' approach. Every pixel in the calibrated image is mapped to an absolute position on the surface of the earth, and these are resampled to produce an undistorted coregistered image of the scene. To do this requires extensive information regarding the satellite position and pointing as a function of time, the precise configuration of the focal plane, and the distortion due to the optics. These must be combined with knowledge about the position and altitude of the target on the rotating ellipsoidal earth. We will discuss the direct approach to MTI coregistration, as well as more recent attempts to 'tweak' the precision of the band-to-band registration using correlations in the imagery itself.
Date: January 1, 2002
Creator: Theiler, J. P. (James P.); Galbraith, A. E. (Amy E.); Pope, P. A. (Paul A.); Ramsey, K. A. (Keri A.) & Szymanski, J. J. (John J.)
Partner: UNT Libraries Government Documents Department

MOVING INTERACTIVE THEMATIC MAPPING FROM MAINFRAME TO MINI: SOME DISIGN POSSIBILITIES AND DEVELOPMENT EXPERIENCE

Description: The analysis, interpretation and assimilation of geographically referenced data often requires that it be presented in the form of maps and other graphic displays. CARTE is a thematic mapping program which produces annotated choropleth, line or point-symbol displays of socio-economic, energy, or other data on a variety of interactive terminals or hardcopy plotters. CARTE is desigend primarily for interactive use and provides both simplicity for the novice and a wide range of options for the advanced user. Script or command files provide a convenient facility for setting defaults and other parameters from a monitor program as well as providing for non-interactive operation. CARTE has the ability to write a script which will reproduce the current map display. This frees the interactive user to concetrate on the map design without concern for keeping track of the commands issued, and also allows him to produce a series of similar maps with a common layout. The goal of CARTE is to provide thematic maps to a broad user community. This software is a part of SEEDIS (Socio-Economic-Environmental-Demographic Information System), a broadly-based set of data bases and software which includes 100 million data items and a wide variety of analytic and display tools. We know that displays such as CARTE are indispensable to our users and we feel that as the state of the art is advanced it will become possible and economical to supply the general public with these kinds of graphic displays. This will allow citizens to participate in decision-making with the same access to data that only a few lucky administrators now have.
Date: November 1, 1979
Creator: Yen, Albert; Holmes, Harvard & Wood, Peter
Partner: UNT Libraries Government Documents Department

Tangential Velocity Measurement Using Interferometric MTI Radar

Description: An Interferometric Moving Target Indicator radar can be used to measure the tangential velocity component of a moving target. Multiple baselines, along with the conventional radial velocity measurement, allow estimating the true 3-D velocity vector of a target.
Date: November 1, 2002
Creator: DOERRY, ARMIN W.; MILESHOSKY, BRIAN P. & BICKEL, DOUGLAS L.
Partner: UNT Libraries Government Documents Department

Anomaly detection using simulated MTI data cubes derived from HYDICE data

Description: The US Department of Energy is funding the development of the Multi-spectral Thermal Imager (MTI), a satellite-based multi-spectral (MS) thermal imaging sensor scheduled for launch in October 1999. MTI is a research and development (R and D) platform to test the applicability of multispectral and thermal imaging technology for detecting and monitoring signs of proliferation of weapons of mass destruction. During its three-year mission, MTI will periodically record images of participating government, industrial and natural sites in fifteen visible and infrared spectral bands to provide a variety of image data associated with weapons production activities. The MTI satellite will have spatial resolution in the visible bands that is five times better than LANDSAT TM in each dimension and will have five thermal bands. In this work, the authors quantify the separability between specific materials and the natural background by applying Receiver Operating Curve (ROC) analysis to the residual errors from a linear unmixing. The authors apply the ROC analysis to quantify performance of the MTI. They describe the MTI imager and simulate its data by filtering HYDICE hyperspectral imagery both spatially and spectrally and by introducing atmospheric effects corresponding to the MTI satellite altitude. They compare and contrast the individual effects on performance of spectral resolution, spatial resolution, atmospheric corrections, and varying atmospheric conditions.
Date: July 1, 1998
Creator: Moya, M.M.; Taylor, J.G.; Stallard, B.R. & Motomatsu, S.E.
Partner: UNT Libraries Government Documents Department

Optical assembly of a visible through thermal infrared multispectral imaging system

Description: The Optical Assembly (OA) for the Multispectral Thermal Imager (MTI) program has been fabricated, assembled, and successfully tested for its performance. It represents a major milestone achieved towards completion of this earth observing E-O imaging sensor that is to be operated in low earth orbit. Along with its wide-field-of-view (WFOV), 1.82{degree} along-track and 1.38{degree} cross-track, and comprehensive on-board calibration system, the pushbroom imaging sensor employs a single mechanically cooled focal plane with 15 spectral bands covering a wavelength range from 0.45 to 10.7 {micro}m. The OA has an off-axis three-mirror anastigmatic (TMA) telescope with a 36-cm unobscured clear aperture. The two key performance criteria, 80% enpixeled energy in the visible and radiometric stability of 1% 1{sigma} in the visible/near-infrared (VNIR) and short wavelength infrared (SWIR), of 1.45% 1{sigma} in the medium wavelength infrared (MWIR), and of 0.53% 1{sigma} long wavelength infrared (LWIR), as well as its low weight (less than 49 kg) and volume constraint (89 cm x 44 cm x 127 cm) drive the overall design configuration of the OA and fabrication requirements.
Date: June 1, 1998
Creator: Henson, T.; Bender, S.; Byrd, D.; Rappoport, W. & Shen, G.Y.
Partner: UNT Libraries Government Documents Department

Design Considerations, Modeling and Analysis for the Multispectral Thermal Imager

Description: The design of remote sensing systems is driven by the need to provide cost-effective, substantive answers to questions posed by our customers. This is especially important for space-based systems, which tend to be expensive, and which generally cannot be changed after they are launched. We report here on the approach we employed in developing the desired attributes of a satellite mission, namely the Multispectral Thermal Imager. After an initial scoping study, we applied a procedure which we call: "End-to-end modeling and analysis (EEM)." We began with target attributes, translated to observable signatures and then propagated the signatures through the atmosphere to the sensor location. We modeled the sensor attributes to yield a simulated data stream, which was then analyzed to retrieve information about the original target. The retrieved signature was then compared to the original to obtain a figure of merit: hence the term "end-to-end modeling and analysis." We base the EEM in physics to ensure high fidelity and to permit scaling. As the actual design of the payload evolves, and as real hardware is tested, we can update the EEM to facilitate trade studies, and to judge, for example, whether components that deviate from specifications are acceptable.
Date: February 1, 1999
Creator: Borel, C.C.; Clodius, W.B.; Cooke, B.J.; Smith, B.W. & Weber, P.G.
Partner: UNT Libraries Government Documents Department

Using Multispectral Imaging to Measure Temperature Profiles and Emissivity of Large Thermionic Dispenser, Cathodes

Description: Thermionic dispenser cathodes are widely used in modern high-power microwave tubes. Use of these cathodes has led to significant improvement in performance. In recent years these cathodes have been used in electron linear accelerators (LINACs), particularly in induction LINACs, such as the Experimental Test Accelerator at Lawrence Livermore National Laboratory and the Relativistic Test Accelerator at Lawrence Berkeley National Laboratory. For induction LINACs, the thermionic dispenser cathode provides greater reproducibility, longer pulse lengths, and lower emittance beams than does a field emission cathode. Los Alamos National Laboratory is fabricating a dual-axis X-ray radiography machine called dual-axis radiograph hydrodynamic test (DARHT). The second axis of DARHT consists of a 2-kA, 20-MeV induction LINAC that uses a 3.2-MeV electron gun with a tungsten thermionic-dispenser cathode. Typically the DARHT cathode current density is 10 A/cm{sup 2} at 1050 C. Under these conditions current density is space-charge limited, which is desirable since current density is independent of temperature. At lower temperature (the temperature-limited regime) there are variations in the local current density due to a nonuniform temperature profile. To obtain the desired uniform current density associated with space-charge limited operation, the coolest area on the cathode must be at a sufficiently high temperature so that the emission is space-charge limited. Consequently, the rest of the cathode is emitting at the same space-charge-limited current density but is at a higher temperature than necessary. Because cathode lifetime is such a strong function of cathode temperature, there is a severe penalty for nonuniformity in the cathode temperature. For example, a temperature increase of 50 C means cathode lifetime will decrease by a factor of at least four. Therefore, we are motivated to measure the temperature profiles of our large-area cathodes.
Date: September 2001
Creator: Simmons, D. F.; Fortgang, C. M. & Holtkamp, D. B.
Partner: UNT Libraries Government Documents Department

MULTISPECTRAL THERMAL IMAGER - OVERVIEW

Description: The Multispectral Thermal Imager satellite fills a new and important role in advancing the state of the art in remote sensing sciences. Initial results with the full calibration system operating indicate that the system was already close to achieving the very ambitious goals which we laid out in 1993, and we are confident of reaching all of these goals as we continue our research and improve our analyses. In addition to the DOE interests, the satellite is tasked about one-third of the time with requests from other users supporting research ranging from volcanology to atmospheric sciences.
Date: March 1, 2001
Creator: WEBER, P.
Partner: UNT Libraries Government Documents Department

RECIPES FOR WRITING ALGORITHMS FOR ATMOSPHERIC CORRECTIONS AND TEMPERATURE/EMISSIVITY SEPARATIONS IN THE THERMAL REGIME FOR A MULTI-SPECTRAL SENSOR

Description: This paper discusses the algorithms created for the Multi-spectral Thermal Imager (MTI) to retrieve temperatures and emissivities. Recipes to create the physics based water temperature retrieval, emissivity of water surfaces are described. A simple radiative transfer model for multi-spectral sensors is developed. A method to create look-up-tables and the criterion of finding the optimum water temperature are covered. Practical aspects such as conversion from band-averaged radiances to brightness temperatures and effects of variations in the spectral response on the atmospheric transmission are discussed. A recipe for a temperature/emissivity separation algorithm when water surfaces are present is given. Results of retrievals of skin water temperatures are compared with in-situ measurements of the bulk water temperature at two locations are shown.
Date: April 1, 2001
Creator: BOREL, C. & CLODIUS, W.
Partner: UNT Libraries Government Documents Department

Neural network identifications of spectral signatures

Description: We have investigated the application of neural nets to the determination of fundamental leaf canopy parameters from synthetic spectra. We describe some preliminary runs in which we separately determine leaf chemistry, leaf structure, leaf area index, and soil characteristics, and then we perform a simultaneous determination of all these parameters in a single neural network run with synthetic six-band Landsat data. We find that neural nets offer considerable promise in the determination of fundamental parameters of agricultural and environmental interest from broad-band multispectral data. The determination of the quantities of interest is frequently performed with accuracies of 5% or better, though as expected, the accuracy of determination in any one parameter depends to some extent on the value of other parameters, most importantly the leaf area index. Soil characterization, for example, is best done at low lai, while leaf chemistry is most reliably done at high lai. We believe that these techniques, particularly when implemented in fast parallel hardware and mounted directly on remote sensing platforms, will be useful for various agricultural and environmental applications.
Date: February 1, 1996
Creator: Gisler, G. & Borel, C.
Partner: UNT Libraries Government Documents Department

MTI Focal Plane Assembly Design and Performance

Description: The focal plane assembly for the Multispectral Thermal Imager (MTI) consists of sensor chip assemblies, optical filters, and a vacuum enclosure. Sensor chip assemblies, composed of linear detector arrays and readout integrated circuits, provide spatial resolution in the cross-track direction for the pushbroom imager. Optical filters define 15 spectral bands in a range from 0.45 {micro}m to 10.7 {micro}m. All the detector arrays are mounted on a single focal plane and are designed to operate at 75 K. Three pairs of sensor chip assemblies (SCAs) are required to provide cross-track coverage in all 15 spectral bands. Each pair of SCAs includes detector arrays made from silicon, iridium antimonide, and mercury cadmium telluride. Read out integrated circuits multiplex the signals from the detectors to 18 separate video channels. Optical filter assemblies defining the spectral bands are mounted over the linear detector arrays. Each filter assembly consists of several filter strips bonded together side-by-side. The MTI focal plane assembly has been integrated with the rest of the payload and has undergone detailed testing and calibration. This paper includes representative test data for the various spectral bands and the overall performance of the focal plane assembly.
Date: June 17, 1999
Creator: Ballard, M. & Rienstra, J.L.
Partner: UNT Libraries Government Documents Department

Multispectral Thermal Imager (MTI) Payload Overview

Description: MTI is a comprehensive research and development project that includes up-front modeling and analysis, satellite system design, fabrication, assembly and testing, on-orbit operations, and experimentation and data analysis. The satellite is designed to collect radiometrically calibrated, medium resolution imagery in 15 spectral bands ranging from 0.45 to 10.70 pm. The payload portion of the satellite includes the imaging system components, associated electronics boxes, and payload support structure. The imaging system includes a three-mirror anastigmatic off-axis telescope, a single cryogenically cooled focal plane assembly, a mechanical cooler, and an onboard calibration system. Payload electronic subsystems include image digitizers, real-time image compressors, a solid state recorder, calibration source drivers, and cooler temperature and vibration controllers. The payload support structure mechanically integrates all payload components and provides a simple four point interface to the spacecraft bus. All payload components have been fabricated and tested, and integrated.
Date: July 7, 1999
Creator: Bender, S.C.; Brock, B.C.; Bullington, D.M.; Byrd, D.A.; Claassen, P.J.; Decker, M.L. et al.
Partner: UNT Libraries Government Documents Department

Assessment of Ivanpah Playa as a Site for Thermal Vicarious Calibration for the MTI Satellite

Description: The Savannah River Technology Center conducted four vicarious reflectance calibrations at Ivanpah Playa, California since July 2000 in support of the MTI satellite. The potential of the playa as a thermal calibration site was also investigated in the campaigns with a mobile Fourier transform infrared spectrometer. The multi-year study shows time and spatial variability in the spectral emissivity. The ground truth temperature and emissivity correlate quite well with the data from the MTI satellite imagery. The research paper will show the time-dependent emissivities measured during our ground truth campaigns and the corresponding satellite imagery.
Date: March 14, 2003
Creator: Villa-Aleman, E.
Partner: UNT Libraries Government Documents Department

Temperature and Emissivity Measurements with the Multispectral Thermal Imager Satellite at Ivanpah Playa

Description: The Multispectral Thermal Imager (MTI) is a research and development satellite sponsored by the Department of Energy (DOE) for accurate water surface temperature retrieval. MTI uses five thermal spectral bands to retrieve ground temperatures. The application of MTI for land-based temperature and emissivity retrieval has been limited. Savannah River Technology Center conducted several ground truth campaigns at Ivanpah Playa to measure reflectance, temperature and emissivity. The results of MTI temperature and emissivity retrievals and material identification will be discussed in context with the ground truth data.
Date: January 6, 2003
Creator: Villa-Aleman, E.
Partner: UNT Libraries Government Documents Department

Assessment of MTI Water Temperature Thermal Discharge Retrievals with Ground Truth

Description: Surface water temperatures calculated from Multispectral Thermal Imager (MTI) brightness temperatures and the robust retrieval algorithm, developed by the Los Alamos National Laboratory (LANL), are compared with ground truth measurements at a mid-latitude cold-water site along the Atlantic coast near Plymouth, MA. In contrast to the relative uniformity of the sea-surface temperature in the open ocean the water temperature near Pilgrim exhibits strong spatial gradients and temporal variability. This made it critical that all images be accurately registered in order to extract temperature values at the six buoy locations. Sixteen images during a one-year period from August 2000 to July 2001 were selected for the study. The RMS error of Pilgrim water temperature is about 3.5 C for the 4 buoys located in open water. The RMS error of the combined temperatures from 3 of the open-water buoys is 2.8 C. The RMS error includes errors in the ground truth. The magnitude of this error is estimated to range between 0.8 and 2.3 C. The two main components of this error are warm-layer effect and spatial variability. The actual error in the MTI retrievals for Pilgrim daytime conditions is estimated to be between 2.7 and 3.4 C for individual buoys and between 1.7 and 2.7 C for the combined open-water buoys.
Date: December 6, 2002
Creator: Kurzeja, R.J.
Partner: UNT Libraries Government Documents Department

RECIPES FOR WRITING ALGORITHMS TO RETRIEVE COLUMNAR WATER VAPOR FOR 3-BAND MULTI-SPECTRAL DATA.

Description: Many papers have considered the theory of retrieving columnar water vapor using the continuum interpolated band ratio (CIBR) and a few the atmospherically pre-corrected differential absorption (APDA) methods. In this paper we aim at giving recipes to actually implement CIBR and APDA for the Multi-spectral Thermal Imager (MTI) with the hope that they can be easily adapted to other sensors such as MODIS, AVIRIS and HYDICE. The algorithms have the four following steps in common: (1) running a radiative transfer (RT) algorithm for a range of water vapor values and a particular observation geometry, (2) computation of sensor band-averaged radiances, (3) computation of a non-linear fit of channel ratios (CIBR or APDA) as a function of water vapor, (4) application of the inverse fit to retrieve columnar water vapor as a function of channel ratio.
Date: January 1, 2001
Creator: Borel, C. C. (Christoph C.); Hirsch, K. L. (Karen L.) & Balick, L. K. (Lee K.)
Partner: UNT Libraries Government Documents Department

MTI Ground Truth Collection Ivanpah Dry Lake Bed, California, May, July, and August 2002

Description: A multi-agency collaboration successfully completed a series of ground truth measurements at the Ivanpah Dry Lake bed during FY 2002. Four collection attempts were made: two in May, one in July, and one in August. The objective was to collect ground-based measurements and airborne data during Multispectral Thermal Imager satellite overpasses. The measurements were to aid in the calibration of the satellite data and in algorithm validation. The Remote Sensing Laboratory, Las Vegas, Nevada; the National Aeronautics and Space Administration; Los Alamos National Laboratory; and the University of Arizona participated in the effort. Field instrumentation included a sun photometer on loan from the University of Arizona and the Remote Sensing Laboratory's radiosonde weather balloon, weather station, thermal infrared radiometers, and spectral radiometer. In addition, three reflectance panels were deployed; certain tests used water baths set at two different temperatures. Local weather data as well as sky photography were collected. May presented several excellent days; however, it was later learned that tasking for the satellite was not available. A combination of cloud cover, wind, and dusty conditions limited useful data collections to two days, August 28 and 29. Despite less-than- ideal weather conditions, the data for the Multispectral Thermal Imager calibration were obtained. A unique set of circumstances also allowed data collection during overpasses of the LANDSAT7 and ASTER satellites.
Date: October 1, 2002
Creator: Hawley, David L.
Partner: UNT Libraries Government Documents Department

Capturing the Green River -- Multispectral airborne videography to evaluate the environmental impacts of hydropower operations

Description: The 500-mile long Green River is the largest tributary of the Colorado River. From its origin in the Wind River Range mountains of western Wyoming to its confluence with the Colorado River in southeastern Utah, the Green River is vital to the arid region through which it flows. Large portions of the area remain near-wilderness with the river providing a source of recreation in the form of fishing and rafting, irrigation for farming and ranching, and hydroelectric power. In the late 1950`s and early 1960`s hydroelectric facilities were built on the river. One of these, Flaming Gorge Dam, is located just south of the Utah-Wyoming border near the town of Dutch John, Utah. Hydropower operations result in hourly and daily fluctuations in the releases of water from the dam that alter the natural stream flow below the dam and affect natural resources in and along the river corridor. In the present study, the authors were interested in evaluating the potential impacts of hydropower operations at Flaming Gorge Dam on the downstream natural resources. Considering the size of the area affected by the daily pattern of water release at the dam as well as the difficult terrain and limited accessibility of many reaches of the river, evaluating these impacts using standard field study methods was virtually impossible. Instead an approach was developed that used multispectral aerial videography to determine changes in the affected parameters at different flows, hydrologic modeling to predict flow conditions for various hydropower operating scenarios, and ecological information on the biological resources of concern to assign impacts.
Date: February 1, 1996
Creator: Snider, M.A.; Hayse, J.W.; Hlohowskyj, I. & LaGory, K.E.
Partner: UNT Libraries Government Documents Department

Multispectral Focal Plane Assembly for Satellite Remote Sensing

Description: Sandia National Laboratories and several subsystem contractors are developing technologies applicable to multispectral remote sensing from space. A proof of concept multispectral sensor system is under development. The objective of building this sensor is to demonstrate and evaluate multispectral imaging technologies for various applications. The three major subsystems making up the sensor are the focal plane assembly (FPA), the cryocooler, and the telescope. This paper covers the focal plane assembly, which is the basis of the sensor system. The focal plane assembly includes sensor chip assemblies, optical filters, and a vacuum enclosure with cold shielding. Linear detector arrays provide spatial resolution in the cross-track direction for a pushbroom imager configuration. The optical filters define 15 spectral bands in a range from 0.45 microns to 10.7 microns. All the detector arrays are mounted on a single focal plane and are designed to operate at 75 K. No beam splitters are used. The four spectral bands covering the visible to near infrared have roughly 2400 pixels each, and the remaining 11 spectral bands have roughly 600 pixels each. The average total rate of multispectral data from the FPA is approximately 15.4 megapixels per second. At the time this paper is being written, the multispectral focal plane assembly is in the fabrication phase. A thermal/mechanical mockup has been built and tested for the vibration environment and to determine the thermal load. Some of the sensor chip assemblies and filters have been built and tested. Several notable features of the design are covered in the paper as well as preliminary test data.
Date: December 31, 1997
Creator: Rienstra, J. & Ballard, M.
Partner: UNT Libraries Government Documents Department

Construction of filter vectors for the information-efficient spectral imaging sensor

Description: The information-efficient spectral imaging sensor (ISIS) seeks to improve system performance by processing hyperspectral information in the optical hardware. Its output may be a gray scale image in which one attempts to maximize the contrast between a given target and the background. Alternatively, its output may be a small number of images, rather than a full data cube, that retain the essential information required in the application. The principal advantage of ISIS is that it offers the discrimination of hyperspectral imaging while achieving the signal-to-noise ratio of multispectral imaging. The paper focuses on construction of the filter vectors that are needed to program ISIS. The instrument produces an image which is essentially a dot product of the scene and the filter vector. Both single vector and multiple vector approaches are considered. Also, they discuss some subtle points related to optimizing the filter vectors.
Date: December 1, 1998
Creator: Stallard, B.R. & Gentry, S.M.
Partner: UNT Libraries Government Documents Department

USING BLOCKS OF SKEWERS FOR FASTER COMPUTATION OF PIXEL PURITY INDEX

Description: The pixel purity index (PPI) algorithm proposed by Boardman, et al.1 identifies potential endmember pixels in multispectral imagery. The algorithm generates a large number of skewers (unit vectors in random directions), and then computes the dot product of each skewer with each pixel. The PPI is incremented for those pixels associated with the extreme values of the dot products. A small number of pixels (a subset of those with the largest PPI values) are selected as pure and the rest of the pixels in the image are expressed as linear mixtures of these pure endmembers. This provides a convenient and physically-motivated decomposition of the image in terms of a relatively few components. We report on a variant of the PPI algorithm in which blocks of B skewers are considered at a time. From the computation of B dot products, one can produce a much larger set of derived dot products that are associated with skewers that are linear combinations of the original B skewers. Since the derived dot products involve only scalar operations, instead of full vector dot products, they can be very cheaply computed. We will also discuss a hardware implementation on a field programmable gate array (FPGA) processor both of the original PPI algorithm and of the block-skewer approach. We will furthermore discuss the use of fast PPI as a front-end to more sophisticated algorithms for selecting the actual endmembers.
Date: October 1, 2000
Creator: THEILER, J.; LAVENIER, D. & AL, ET
Partner: UNT Libraries Government Documents Department

Material characterization using a hyperspectral infrared imaging spectrometer

Description: Fourier transform spectroscopy has found application in many areas including chemometrics, biomedical and biochemical studies, and atmospheric chemistry. This paper describes an investigation into the application of the LLNL Hyperspectral Infrared Imaging Spectrometer (HIRIS) to the non-destructive evaluation of man-made and natural materials. We begin by describing the HIRIS system and the objects studied in the investigation. Next, we describe the technique used to collect the hyperspec- tral imagery, and discuss the processing required to transform the data into usable form. We then describe a technique to analyze the data, and provide some preliminary results.
Date: October 30, 1998
Creator: Aimonetti, W D; Bixler, J V & Roberts, R S
Partner: UNT Libraries Government Documents Department

Transformation of filter transmission data for f-number and chief ray angle

Description: This paper describes a method for transforming measured optical and infrared filter data for use with optical systems of arbitrary f-number and angle of incidence. Although it is generally desirable to have normal incidence at the filter (i.e., collimated light where an optical filter is used), other system design considerations may take precedence. In the case of a multispectral sensor under development at Sandia National Laboratories, system constraints require optical filter placement very near the focal plane. The light rays incident on the filters are therefore converging as determined by the system f-number while the chief ray of each ray bundle varies with focal plane position. To analyze the system`s spectral response at different points on the focal plane, a method was devised to transform the filter vendor`s measured data to account for the optical system design. The key to the transformation is the determination of weighting factors and shift factors for each angle of incidence making up a ray bundle. A computer worksheet was developed using a popular mathematical software package which performs this transformation for 75 key points on the focal plane.
Date: March 1, 1998
Creator: Rienstra, J.L.
Partner: UNT Libraries Government Documents Department