Infrared Scene Projector Research Articles

Dynamic infrared scene projection: a review

Since the early 1990s, there has been major progress in the developing field of dynamic infrared scene projection, driven principally by the need for hardware-in-the-loop simulation of the oncoming generation of imaging infrared missile seekers and more recently by the needs for realistic simulation of the new generation of thermal imagers and forward-looking infrared systems. In this paper the current status of the dynamic infrared projection field is reviewed, commencing with an outline of its history. The requirements for dynamic infrared scene projection are examined, allowing a set of validity criteria to be developed. Each class of infrared projector that has been investigated—emissive, transmissive, reflective, laser scanner and phosphor—together with the specific technology initiatives within the class is described and examined against the validity criteria. In this way the leading dynamic infrared scene projection technologies are identified.

Multilayer Coatings and Optical Materials for Tuned Infrared Emittance and Thermal Control

AbstractMany thermal control applications require thin film coatings that emit or absorb strongly at near infrared and infrared wavelengths. One of the primary applications for these coatings is thermal control for surfaces and structures of spacecraft, which are exposed to solar radiation during at least 60% of their orbit, causing wide temperature fluctuations. Another recent application for this type of coating is infrared emissive imaging employing a fiber optic infrared scene projector. While single layer coatings can provide high emissivity in a broad wavelength band, multilayer coatings can be used to obtain higher emissivities over a narrow wavelength band. This band can be tuned to a specific range of temperatures and wavelengths. Coatings developed for thermal control have a reflective base layer, either ZrN or a refractory metal boride or silicide. These materials have increased durability compared to metal layers. The multilayer coating deposited over the based layer consists of an A1203/SiO2 stack with high emittance at 300 K (9.8 μm), and solar reflectance near 0.6. Multilayer tuned infrared absorber/emitter coatings are applied to fiber optic infrared scene projectors. The coatings consists of a three layer Si3N4/Cr/Si3N4 absorber tuned at the 1.06 μtm laser wavelength, and a six layer Cr/dielectric/Cr/dielectric/Cr/dielectric coating which emits strongly in either the 3 - 5 jim or the 8 - 12 μm infrared wavelength bands. Absorption bands of the coatings are independently tunable. All coatings are deposited by reactive DC and RF magnetron sputtering onto 2.5-in fiber optic faceplates. Either Si3N4, Si, or ZnS thin film dielectric materials were used in the emitter coatings. With an input laser power of 15 W, the coatings emit at a black body temperature 529 K, which compared well with predicted performance.

Thermal crosstalk modelling of thin film resistor arrays

This paper describes the thermal modelling results for a thin film resistor array which can have applications in infrared scene projection. In this design, the array consists of two parallel rows of resistor elements. A central aluminium busbar which forms a common electrical connection for all resistor elements, also provides thermal isolation between the two rows through thermal connection to the array substrate. It is shown that the thickness of the aluminium busbar of the order of 2 μm is sufficient to provide good thermal isolation, thus allowing an increase in the pixel fill factor.

Applications of negative luminescence

The application of non-equilibrium transport techniques to narrow-gap semiconductor materials has produced practical, negative luminescent devices. These structures contravene Kirchhoff's law because they will absorb infrared radiation in a limited band without emitting it. They have many potentially important applications which include toxic gas sensing, cold shields for IR detectors, radiometric reference sources and dynamic infrared scene projectors.

Review of infrared scene projector technology-1993

The importance of testing IR imagers and missile seekers with realistic IR scenes warrants a review of the current technologies used in dynamic infrared scene projection. These technologies include resistive arrays, deformable mirror arrays, mirror membrane devices, liquid crystal light valves, laser writers, laser diode arrays, and CRTs. Other methods include frustrated total internal reflection, thermoelectric devices, galvanic cells, Bly cells, and vanadium dioxide. A description of each technology is presented along with a discussion of their relative benefits and disadvantages. The current state of each methodology is also summarized. Finally, the methods are compared and contrasted in terms of their performance parameters.

Laser scophony infrared scene project

A scophony infrared scene projector (IRSP) was developed by AURA Systems Inc. for use in evaluating thermal imaging guidance systems. The IRSP is a laser-scanned projector system incorporating scophony modulation with acousto-optical (AO) devices to produce multiband 96 x 96 image frames. A description of the system and preliminary test results with the Seeker Endo/Exo Demonstration Development (SEEDD) breadboard interceptor are addressed.

Crosstalk model of a deformable-mirror-based infrared scene projector

An analytical model for crosstalk is developed for an infrared scene projector that utilizes a deformable-mirror device as an infrared spatial light modulator. Partial-coherence effects that result from the physical layout of the projection system are included. Crosstalk is determined by defining a crosstalk ratio in the projected image. Crosstalk-ratio calculations are carried out for monochromatic and blackbody projection sources over the 3- to 5-μm wavelength band. The results predict crosstalk ratios of 260:1, 1200:1, and 2400:1 for deformable-mirror pixels of 50, 100, and 150 μm when a blackbody source is used in the projection system. Crosstalk performance is improved at shorter wavelengths and for larger deformable-mirror pixels. The results of a proof-of-principle experiment are included to verify the feasibility of a deformable-mirror device in the projection system.

Electron-beam-addressed membrane mirror light modulator for projection display

The performance of a prototype, reflection-mode projection display based on an electron-beam-addressed membrane mirror light modulator (e-MLM) is described. The e-MLM converts electronic video information into a two-dimensional phase object, that is then schlieren imaged onto a screen. High-contrast dynamic projection of images is demonstrated over a broad range of wavelengths, from the visible to the midinfrared. As such this device is expected to find applications in large-screen visible displays and dynamic infrared scene projectors.

Modulation transfer function characterization and modeling of a Scophony infrared scene projector

A Scophony-configuration infrared scene projector, consisting of a raster-scanned CO₂ laser and an acousto-optic (AO) modulator, was characterized for modulation transfer function (MTF) performance. The MTF components considered in the model were the Gaussian beam input to the AO cell, the finite aperture of the scan mirror, the width of the detector in the image plane, the transfer function of the amplifier electronics, and a term caused by Bragg-angle detuning over the bandwidth of the amplitude modulation (AM) video signal driving the AO cell. The finite bandwidth of the input video signal caused a spread in the Bragg angle required for maximum diffraction efficiency. In the Scophony configuration, a collimated laser beam enters the AO cell at only one particular angle, so a falloff of diffraction efficiency (and hence MTF) resulted as the modulation frequency was increased. The Bragg-angle detuning term was found to dominate the measured system MTF.