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OPTRA is currently developing a Risley Prism Universal Pointing System (RPUPS): a highly customizable cued beamsteering system. The RPUPS consists of a visible or infrared cueing imager co-aligned with an optical beam steering system’s pointing-field-of-regard. The cueing imager is used to identify a region-of-interest within its wide field-of-view, via a wireless tablet device. The tablet user can choose to manually or automatically, identify and track regions-of-interest. The optical beam steering system uses a matched pair of Risley Prisms to direct an interrogating optical system’s instantaneous-field-of-view onto the identified region-of-interest. The tablet updates the user with real time information from both the cueing imager and the interrogating optical system. Risley prism material and geometry choices provide operating wavelength, aperture size, and field-of-regard flexibility for this front-end pointing component. Back-end components may be receive-only, transmit-only, or transmit/receive combinations. The flexibility of the RPUPS allows for mission specific customization where applications include but are not limited to: synthetic foveated imaging, spectroscopic probes and laser (LIDAR) ranging and tracking. This paper will focus on the design and anticipated applications of the RPUPS.

We report on our current status towards the development of a prototype Fourier transform infrared phase shift cavity ring down spectrometer (FTIR-PS-CRDS) system under a U.S. EPA SBIR contract. Our system uses the inherent wavelength-dependent modulation imposed by the FTIR on a broadband thermal source for the phase shift measurement. This spectrally-dependent phase shift is proportional to the spectrally-dependent ring down time, which is proportional to the losses of the cavity including those due to molecular absorption. Our approach is a broadband and spectral range enhancement to conventional CRDS which is typically done in the near IR at a single wavelength; at the same time our approach is a sensitivity enhancement to traditional FTIR owing to the long effective path of the resonant cavity. In this paper we present a summary of the theory including performance projections and the design details of the prototype FTIR-PS-CRDS system.

A hyperspectral Fourier transform spectrometer (HS-FTS) has been developed to study biological material binding to surfaces through spatially resolved, spectral self-interference fluorescence microscopy and also label-free white light reflectance spectroscopy. Spectral self-interference fluorescence microscopy yields the height of fluorescent tags bound to a specific location on biomolecules tethered to a surface, and from this the biomolecule conformation can be predicted; white light reflectance spectroscopy yields the average height of an ensemble of biomolecules relative to the surface. The HS-FTS is composed of a small, step scanning Michelson interferometer made by Optra, Inc., a series of commercial off the shelf imaging lenses, and a 12-bit thermoelectrically-cooled CCD camera. The system operates over the 500 to 900 nm spectral range with user defined spectral resolution, thereby supporting use of a host of fluorescent tags or white light spectral windows. The system also supports near real-time hyperspectral cube acquisition via undersampling with the use of a spectral filter and user defined interferometer step increments. The overall approach offers flexible yet sensitive measurement capability for a variety of biological studies. Preliminary results are presented of both spectral self-interference fluorescence microscopy and white light reflectance spectroscopy measurements of artificial, photographically etched surfaces with feature heights on the order of 10 nm. Planned future work includes spectral self-interference fluorescence microscopy measurements of biomolecule conformation as manipulated by external electrical and magnetic fields as well as label-free white light reflectance spectroscopy measurements of DNA microarrays.

Lasers for defense applications continue to grow in power and fill in new portions of the spectrum, expanding the laser eye safety hazard, particularly to aircrew and aviation safety. The Laser Event Recorder Program within Naval Air Systems Command (NAVAIR) seeks to develop a low cost, self-contained laser sensor able to detect, warn and record laser exposures that hazard aircrew vision. The spectral and temporal range of hazardous lasers (400 to 1600 nm and pulsed to continuous) has presented a challenge in the past. However, diffractive optics and imaging technologies have enabled a solution to this growing threat. This paper will describe the technical requirements for the Laser Event Recorder, which are based on ANSI Z136.1 laser safety standards and common to its use on any platform. To support medical and operational laser eye protection, the LER extracts and records laser wavelength, radiant exposure, exposure duration, pulse structure, latitude, longitude, altitude and time of laser exposure. Specific performance and design issues of the LER prototype will be presented in a companion paper. In this paper, fundamental challenges to the requirements encountered during the first two years of research, development and successful outdoor testing will be reviewed. These include discrimination against all outdoor light levels and the impact of atmospheric beam propagation on accuracy of the radiant exposure determination. Required accuracy and response time of the determination of whether a laser exposure exceeds the maximum permissible exposure (MPE) will be described. Ongoing efforts to coordinate laser exposure reporting and medical management will also be discussed.

The primary objective of this effort is to develop a low-cost, self-powered, and compact laser event recorder and warning sensor for the measurement of laser events. Previously we reported on the technology and design of the Laser Event Recorder. In this paper we describe results from a series of ground and airborne tests of the Laser Event Recorder.

Radio pulses emitted in the Atmosphere during the air shower development of high-energy primary cosmic rays were measured during the late 1960ies in the frequency range from 2 MHz to 520 MHz. Mainly due to difficulties with radio interference these measurements ceased in the late 1970ies. LOFAR (Low Frequency Array) is a new digital radio interferometer under development. Using high bandwidth ADCs and fast data processing it it will be able to filter out most of the interference. By storing the whole waveform information in digital form one can analyze transient events like air showers even after they have been recorded. To test this new technology and to demonstrate its ability to measure air showers a "LOFAR Prototype Station" (LOPES) is set up to operate in conjunction with an existing air shower array (KASCADE-Grande). The first phase consisting of 10 antennas is already running. It operates in the frequency range of 40 to 80 MHz, using simple short dipole antennas and direct 2nd Nyquist sampling of the incoming wave. It has proven to be able to do simple astronomical measurements, like imaging of a solar burst. It has also demonstrated how digital interference suppression and beamforming can overcome the problem of radio interference and pick out air shower events.

The primary objective of this effort is to develop a low-cost, self-powered, and compact laser event recorder and warning sensor for the measurement of laser events. The target requirements are to measure the wavelength, irradiance, pulse length, pulse repetition frequency, duration and scenery image for each event and save the information in a time and location stamped downloadable file. The sensor design is based on a diffraction grating, low-cost optics, CCD array technology, photodiodes, integral global positioning sensor, and signal processing electronics. The sensor has applications in laser safety, video surveillance and pattern recognition.

OPTRA has developed a low-cost, extremely compact, rugged open-path Fourier transform infrared (OP-FTIR) spectrometer for workplace air quality monitoring. This research was funded under a United States Air Force ABIR Phase II contract. The goal of the program has been to identify and alleviate all aspects of currently available OP-FTIR systems which result in high-cost and complex user requirements. This low-resolution ssytem (Δσ = 8 cm-1) employs an uncooled DLATGS detector and a novel encoder-based reference metrology. Other design economies include a plastic injection-molded retroreflector array to return the open-path beam. This effort has included the development of a set of algorithms based on artificial neural networks (ANNs) and partial least squares (PLS) by the University of Idaho; these algorithms are specifically tailored to low-resolution systems applied to multi-component analysis of large, organic molecules characterized by broad infrared resonance bands. The algorithms, coupled with our OP-FTIR, are designed to autonomously identify and quantify a list of 105 common industrial organic molecules in the presence of varying humidity levels. Our system includes two PCI boards which host all OP-FTIR processing and servo electronics; the boards reside in a small suit-case PC along with a user-friendly Graphical User Interface.

This paper describes the evolution and capabilities of our Fourier transform infrared (FTIR) modulator in multiple configurations for various applications concerning Homeland Security. The heart of our system is the extremely compact and rugged Michelson interferometer we originally developed during our involvement with the JSLSCAD program. (1) Our "J-Series" modulator is capable of resolving the 7 to 14 μm spectral region to 4 or 16 cm -1 with a measured radiometric sensitivity of 2x10 -9 W/(cm 2 ster·cm -1 ). This system has successfully undergone rigorous testing for operation over a temperature range of -40 to +65°C and vibration levels associated with a spectrum of military ground, air, and water vehicles. The following describes the design and characterization of our J-Series modulator as well as the subsequent evolutions of the instrument in the forms of an active open-path FTIR and an imaging (hyperspectral) FTIR. We present this system in passive and active configurations with cooled, uncooled, and imaging detectors. We also project sensitivity limits for each configuration and measurement for some common chemical agents as well as industrial compounds.

We present a new hyperspectral imaging system for the long wave infrared (LWIR) based on a tunable first-order Fabry-Perot Scanning Spectrometer (FPSS). The FPSS operates over 8 O 12 micrometers with a spectral resolution of 1% of the wavelength. The FPSS has a 22 degree field of view and a spatial resolution of 0.11 degrees. The key components of the FPSS system are the collection optics, a tunable Fabry-Perot etalon, optical position sensors, a closed-loop positioning system, an uncooled microbolometer focal plane array, a digital frame grabber card, and a user-friendly Graphical User Interface (GUI).

Interferant spectral features that are stable in both time and optical frequency oftentimes can be made negligible with respect to spectral features of interest by simple data processing techniques such as absorbance subtraction. With varying degrees of success more sophisticated processing of these same spectra can reject these interferant spectral features even when not stable in time. Beyond this, a classic approach to rejecting spectral interferants is to operate at higher and higher spectral resolutions so that ultimately the interferant feature separates from the feature of interest so that it is of negligible effect as an interferant. For a given observation time this approach results in a loss of radiometric sensitivity. A further reduction in radiometric sensitivity may occur since the maximum allowed etendue in a fixed parameter system must also be decreased to accommodate the higher resolution. (This reduction in etendue is more likely in the instance of a process control application as opposed to an open path monitoring application). The use of offset scanning and field widening as techniques for regaining this lost sensitivity are discussed.

Over the past two decades major advances in FTS have allowed process control engineers to more readily consider the use of this measurement technique. The most striking advance has been in the area of data processing facilitated by extraordinary increases in computing power. The development of improved optical fibers has provided a means for bringing the measurement to the factory floor while providing a remote `laboratory environment' site for the less-than-robust spectrometer optical systems. Recent advances in auto-aligned systems again permit consideration of moving the spectrometer system to locations in close proximity to the process itself. Generally, these systems are based on the use of HeNe lasers for the reference and auto-align mechanism. This results in large and expensive measurement heads to again argue against placement of the spectrometers proximate to the process. This paper describes the successful use of a solid state light source in place of the HeNe laser in an auto- aligned and referenced FTS system which allows consideration of small and inexpensive process control spectrometers. A review of a spectrometer system utilizing a combination of auto-align and referencing technologies utilizing diode sources is presented. DOD and NASA support enabled this dual-use technology to be developed.

A common application of digital imaging colposcopy in cervical examinations is the measurement of lesion dimensions and areas. Typically this is done by interactively marking the region of interest on a cervix image, calculating the corresponding pixel dimensions and then scaling to the colposcope optics. Until now no one has suggested a solution to the effects of the cervical surface slant on these measurements. Away from the cervical os the surface slant is large and lesion dimensions there will be underestimated, possibly leading to a misinterpretation of the lesion's progression. In this paper we discuss a noninvasive method for determining the surface geometry of the cervix using digital imaging colposcopy. The method is an application of shape-from-shading techniques used to determine the surface slant at all points in the cervix image. From the surface slant we can calculate area corrections to measurements made on the image. In our initial investigations we have applied this method to area measurements of circular regions drawn on spherical test targets. Our results indicate that we can obtain improvements in area measurement errors of factors between 3 and 6, resulting in relative errors of a few percent.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Dynamic alignment has been demonstrated as a practical approach to alignment maintenance for systems in the infrared region of the spectrum. On the basis of work done by OPTRA, this technique was introduced in commercial Fourier transform spectrometer systems in 1982 and in various forms is now available from a number of manufacturers. This paper reports on work by OPTRA to extend the basic technique to systems operating in the ultraviolet. In addition, this paper reports the preliminary results of the development of an alignment system using a laser diode in place of a gas laser normally found in dynamic alignment systems. A unique optical system and spatial heterodyne technique allows for achievement of a metrology system with characteristics that fully satisfy the requirements of an ultraviolet spectrometer system.

Polarimeter design often involves the use of the Mueller matrix formalism. For relatively simple, idealized optical systems this formalism provides elegant results. However, when polarimeters have several optical components and their imperfections are considered, the Mueller calculus can become complex. With the computing power readily available today it is possible to perform the Mueller calculus in software, both symbolically and numerically. This capability makes it feasible to design and operate polarimeters having complicated intensity functions due to non-ideal optical components. Using a generalized linear least squares method it is possible to recover source polarization from intensity measurements even if a polarimeter has imperfect components. What this requires is a determination of the polarimeter's modulation functions, either by computer modelling or by direct measurement using a known Stokes source. We discuss our work implementing computer-aided polarimetry using the Mueller calculus and application of this methodology for doing polarimetry with non-ideal optical components. In particular, we present results of a computer simulation of an imaging polarimeter which has a quarter-wave plate with nonuniform retardance. Our results indicate that by the polarimetry approach discussed here this retardance `imperfection' will not prevent the polarimeter from accurately measuring the source polarization.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We are developing an interactive computer program which includes many of the possible options available for the design of a polarimeter, for the analysis of the output signal, and for the computation of the polarization of the source under investigation. The software is being implemented on a microcomputer and is operated interactively. It utilizes pull-down menus, dialog boxes, graphics and mouse-driven point and click techniques to ease user interaction. We have addressed the issue of how to represent the polarimetric model in software by manipulating optical element transformation matrices (Mueller matrices) to produce the resultant polarimeter matrix. To keep the polarimetric model general and to facilitate analytic evaluations of polarimeter designs we represent these matrices in symbolic form in the software. The software tool will have wide ranging applications in areas of engineering, research and education dealing with polarimetry. It can be used as a design tool for polarimeters in laboratories, remote sensing, or both ground- and space-based astronomy. It can also be used as a simulation tool for polarimetric measurements which will be useful for evaluating polarimeter designs or for educational purposes. The software contains a data reduction tool which can be used to evaluate intensity measurements made by a specified polarimeter.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have developed a microcomputer based system with an application specific software package which permits the direct digitization and analysis of transrectal ultrasound (TRUS) images. The system is highly flexible and enables access to a wide range of image analysis tools through relatively simple software modifications which cannot. be implemented using a standard ultrasound instrument. We have demonstrated the capability of the system by an analysis of a number of morphometric parameters and by a correlation of these measurements with the presence of prostatic cancer. We found that the measurement of the ratio of the anterior-posterior axis to transverse axis (ATR) and the presumed circular area ratio (PCAR) were significant predictors of prostatic cancer. The sensitivity of the PCAR measurement was 93 the specificity was 50 the positive predictive value was 57 and the negative predictive value was 91. This system provides researchers with an efficient economical and flexible method to aid in the analysis of ThUS images in a quantitative manner. 1.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have developed a practical digital imaging colposcope for use in research on early detection of cancerous and pre-cancerous tissue in the cervix. Several copies of the system have now been used in a variety of clinical and research environments. Two issues of considerable interest which emerged early in our work involved the roles of color and spatial resolution as they applied to digital imaging colposcopy. In each instance these qualities potentially have a significant impact on the diagnostic efficacy of the system. In order to evaluate the role of these parameters we devised and conducted a receiver operating characteristic (ROC) evaluation of the system. It is apparent from these tests that a spatial resolution of 512 x 480 pixel with 7 or 8 bits of contrast is adequate for the task. The more interesting result arises from the study of the use of color in these examinations; it appears that in general, contrary to the widely held perception of the physicians involved, color apparently provides the clinician with little or no diagnostic information. Indeed, in some instances, access to color seemed to confuse the physician and resulted in an elevated rate of false positives. Results of the ROC tests are presented in this paper along with their implications for further development of this imaging modality.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We have developed a prototype digital imaging colposcope system for use in clinical, research and teaching environments. A goal of this system is to aid in earlier detection of cervical pathology and to assist in more precise site directed biopsies. The system is expected to provide a valuable research and teaching tool, as well as a mechanism for including colposcopic images in proposed medical Picture Archiving and Communications Systems (PACS). The system consists of a charge coupled device (CCD) imager attached to the camera port of a conventional photocolposcope, a microcomputer host and a software package for processing of the resultant digital images. It is envisioned that this basic system could eventually be reconfigured to accommodate advantages to be derived from an integrated expert system. We discuss the hardware and software system, review some of the analysis algorithms used for this application and present preliminary results of clinical use of the system.

We have developed a unique prototype solid state digital imaging system for use in the analysis of one dimensional deoxyribonucleic acid (DNA) sequencing gels. The system can be used to digitize, interpret and store DNA sequence information directly from an autoradiogram. The system consists of a two dimensional charge coupled device (CCD) imager, a multiplexing optical front end for reformatting of the gel image, a microcomputer host and a software package for reconstruction of the gel image and analysis of the DNA sequence.

We have developed a prototype microcomputer based gel reader for the digitization and semi-automatic analysis of two dimensional polyacrylamide electrophoretic gels. The system uses a 2D charge coupled device (CCD) detector and operates as a peripheral to an IBM PC XT/AT type host computer. The system incorporates a comprehensive software package which lends itself to highly structured clinical applications as well as a wide range of image processing functions for use in the research laboratory. The system is undergoing further development in order to arrive at a comprehensive, low cost, early disease screening device. Electrophoretic gel samples of protein components obtained from subject patients are digitized and searched for anomalous features. These features are located using a digital reference library of disease related protein features and a probability of detection of the disease related protein is computed. The system then presents the physician with a report advising him of the results of the analysis. We describe the hardware and software system and present results of a sample gel analysis.