Focal plane arrays (FPA) have eliminated bulky scanning mechanisms. While it is now possible to build more compact and lighter thermal imaging systems, the demand on the performance of the imaging objective has increased. To discuss these higher demands, and to provide some guidance in how to deal with them, is the purpose of this paper.

The advantages of hybrid refractive/diffractive components in medium wave infrared (MWIR) zooms are illustrated through the use of design examples. The examples illustrate that hybrids may be used to simplify the construction of achromatic or athermal zoom groups.

Various means of scene generation are used to test infrared focal plane sensors. At Arnold Engineering Development Center a Direct Write Scene Generator is being developed. A scene is projected onto the focal plane array by scanning a rake of beams across the surface of the sensor. The rake consists of 128 synchronous beams generated by passing a single laser beam through an acousto-optic cell with a complex radio frequency signal input. Each pixel of the focal plane is illuminated by one of the beams in the rake. The beam is blanked as the rake scans from one row of pixels to the next on the focal plane array. The Direct Write Scene Generator is being designed to test focal planes as large as a 512 X 512 pixel array. Scan optics were designed to focus an expanded laser beam to a spot smaller than the focal plane pixel pitch over the entire test area. Several optical configurations are needed to achieve the requirements at various wavelengths.

When designing wide field of view tactical or scientific infrared systems, the performance requirements often demand that a large aperture, diffraction limited telescope be specified. In such cases, it is often difficult to maintain a flat focal plane and to limit the image plane size to match an existing infrared focal plane array technology. In this paper the design of an optical system containing a coherent infrared fiber bundle is described. The advantages of reformatting a curved liner image plane to match a planar 2-D focal plane array are discussed. To validate the design concepts, a 12 channel fluoride fiber was employed to relay the image of a Schmidt Telescope to a remotely located detector array. A comparison of predicted system performance and measured system performance is presented.

The field of infrared micro-spectroscopy chiefly utilizes reflective objective designs due to the broad spectral ranges over which they operate. Some disadvantages of this design methodology are briefly discussed. A technique for the identification of complimentary materials best suited for enhanced achromatic performance over broad spectral regions in the infrared is investigated. This technique is applied to the task of designing refractive microscope objectives capable of diffraction limited performance over the 0.8 (mu) to 12 (mu) spectral range.

Optical design software has been developed which includes the capability to model illumination systems. The software allows one to predict the intensity distribution of radiation at a plane located at some distance from the source. An illumination system comprising an ellipsoidal reflector and a spherical source was modeled and the results of the analysis compared to those achieved experimentally.

Many infrared (IR) imaging systems have been proposed which utilize hybrid refractive/diffractive optical elements; however, examples of their use in wide field-of-view (WFOV) lens assemblies have been noticeably absent. This paper discusses the design and aspects of the fabrication of a high performance WFOV infrared objective which utilizes a hybrid refractive/diffractive optical element.

The use of a commercially available LCD panel of an overhead projector is suggested for coherent optical processing as a low cost SLM in this paper. The LCD panel is used as a spatial light modulator for inputting the image to be processed in real time.

Thermal radiation sources are often used in thermal imaging sensors as reference sources for offset equalization and gain normalization of the infrared detecting elements. For best results, the `t-number' by which the detector elements view these sources must be exactly equal to that with which they view the external scene. If the t-numbers for different detecting elements are not the same, the result will be inaccurate offset equalization and imperfect gain normalization. The relationship between the scene temperature, reference source temperature, and t-number differences are derived. Quantitative values for the errors in gain and level normalization are calculated.

To optimize system performance, several factors must be considered in the design of IR window assemblies. These include -- but are not limited to -- transmission shading and bondline effects. If not properly considered, these factors can easily limit the performance of modern thermal imaging systems. This paper discusses the aforementioned factors in detail and illustrates, by way of examples, how they can be minimized.

The Infrared Instrumentation System (IRIS) is an operational infrared imaging radiometer developed and operated by Automated Sciences Group, Inc. under contracts DASG60-89-C- 0055 and DASG60-92-C-0111 to the U.S. Army Space and Strategic Defense Command in Huntsville, AL. The IRIS operates in calibrated bandpasses from 1.3 to 14 micrometers using three IR staring focal plane arrays and from 0.4 to 0.9 micrometers using an intensified visible camera. The IRIS is located on its own independent pointing and tracking platform on the High Altitude Observatory (HALO), a Gulfstream IIB operated under contact to the U.S. Army by another company. The IRIS has a high-speed digital data recording system for the three IR sensors and an analog video recording capability for all four sensors. This paper discusses the modular design and operational flexibility of the IRIS. A discussion of the theoretical performance predictions and actual sensitivities as measured in the laboratory and from stellar calibrations is included.

As successful as the M1A1 Abrams tank was in the Gulf War, a program has been under way for several years to improve and modernize the M1A1 to keep pace with new threats and to take advantage of new technology. This program has resulted in the M1A2 upgrade program which significantly improves the survivability and lethality of the tank. First, the point-to-point wiring and analog signal processing was replaced with digital processing and control with a modern, aircraft-style digital data bus. Additional command and control aspects of the upgrade greatly improved the situational awareness of the M1A2 commander. Finally, an additional thermal imaging system was added for the commander. This system, the M1A2 Commander's Independent Thermal Viewer (CITV) is the topic of the following paper, which details the design from a system engineering perspective, and a companion paper that presents the optical design perspective.

The M1A2 Commander's Independent Thermal Viewer (CITY) lens design resulted from several years of interaction and tradeoff between optical designers, mechanical engineers, and systems engineers. While the general design concept remained constant throughout the process, important modifications were made to accommodate new performance requirements or to incorporate new fabrication technology.

A new form of three mirror anastigmat (TMA) has emerged in which the primary and tertiary mirrors share a common vertex. This allows the two mirror surfaces to be machined on the same substrate. The literature to date has shown that reimaging forms have been restricted to a moderate field-of-view (< 3 degree(s)). This paper illustrates design forms which achieve excellent performance over a wide field-of-view (3 degree(s) X 7 degree(s)).

The design of a 3D display system that is simultaneously autostereoscopic, look-around, raster-filled, and dynamic and that is enabled by new digital micromirror device technology is discussed.

Multiorder Etalon Sounder (MOES) is an instrument concept investigated by the Space Physics Research Laboratory (SPRL) of The University of Michigan and the ITT Aerospace/Communications Division (ITT/ACD) at Fort Wayne, Indiana as a possible candidate for the next generation operational vertical temperature and moisture sounder. MOES exploits the high throughput, high resolution, and periodic transmission characteristics of the Fabry-Perot interferometer (FPI) and the periodic spectrum of CO₂ to achieve high spectral resolution and high signal to noise. In this paper, we describe the MOES laboratory prototype project carried out by SPRL and ITT/ACD. The detailed design, construction, and laboratory testing of important instrument components are presented. The problems encountered, lesson learned, and the solutions applied to those problems during the laboratory prototype process are discussed.

A wide-field ultraviolet lens was developed under a contract from the Massachusetts Institute of Technology Center For Space Research in support of the NASA High Energy Transient Experiment (HETE). This 35 mm f/2.5 seven element lens operates over a broad portion of the near-ultraviolet spectrum and over a 52 degree field of view. Operation at cryogenic temperatures required that the lens system exhibit minimal change in focus with temperature. Aluminum was selected as the lens barrel material based on athermalization issues and the desire to minimize weight. Elastomeric bonding of elements into subcells was used for assembly along with a single adjustable airspace to compensate for tolerances.

Relations between a spatial distribution of laser pulse energy and a temporal alteration of a pressure of the sound generated in air when laser radiation is absorbed by the solid surface are obtained. The method of energy distribution restoration is proposed. Its efficiency was examined in laboratory experiment.

Under illumination of a solid absorbing target by short laser pulse the acoustic waves are excited both inside the target and in the surrounding air. When the surface of the target is plane the shape of acoustic signal in the air depends on the intensity distribution in the illuminating laser beam. In this report the results of restoration of two-dimensional intensity distribution of pulse laser beam by method of acoustic tomography are presented. As the target a plane metal plate was used. Measurements of acoustic signals were carried out by nine microphones placed around the illuminating beam not far from the target. Two-dimensional intensity distribution of laser beam obtained by acoustic methods are in good agreement with data obtained by usual photometric method.

This paper describes some observations of high pulsed laser damage on optical fiber endfaces (approximately 8 - 9 GW/cm²). In the experimental set-up, the pulse of an Nd-Yag laser (wavelength 1060 nm, pulse duration 10 ns, output energy 0.3 J) is focused upstream from the end surface. Five-hundred-forty micrometers core diameter fibers are used. For a limited number of pulses, transmitted energies can raise 50 to 115 mJ.