The goal of this effort was to design, develop, and demonstrate diffractive anti-reflection structures (DARS) on gallium arsenide (GaAs). Structures were designed and fabricated in GaAs intended to reduce the reflectance to infrared radiation from 1-10 microns wavelength. Design trade studies were performed to determine the optimum overall depth and period of the structure. The wafers were coated with UV sensitive photoresist and exposed in our interferometric stepper and our reduction stepper. Patterned areas were approximately 1cm x 1cm square. The wafers were then developed and measured to determine that the appropriate size and shape had been achieved prior to etching the pattern into the substrate. The wafer was etched in a plasma reactor to transfer the developed pattern into the GaAs. The depth and period of the surface was characterized using an atomic force microscope and a Scanning Electron Microscope. Reflectance spectra were measured for several angles of incidence.
This paper describes a multi-view stereoscopic 3-D display. The display technology does not involve goggles, polarized glasses, colored glasses or any other eyewear. It allows parallax, in that as the viewer moves their head left and right, the viewer can 'see around corners.' The method involves a microlens array on top of a liquid crystal display. The microlens is designed to project multiple views to multiple eye positions. The distance between stereo eye positions is the average distance between eyes of 55 mm. As many as eight views are interlaced on the display and fanned out by the microlens array. Thus 4 stereo pairs can be observed, each pair from a unique angular perspective. For this system, since multiple views are available, seeing the 3-D effect is much easier. In addition, the 3-D effect can be seen far off axis; so more than 1 person can view the display at the same time.
The output from a laser diode is not circularly symmetric, the output divergence in one axis is much greater than that in the transverse axis. MEMS Optical has developed a laser diode circularizer1 that can take the elliptical output beam from a laser diode and circularize the beam. Due to it’s operating principle, it has a major advantage in that precise alignment is not required, making assembly operations much simpler and faster. Due to the ability to manufacture this device in wafer scale, it can be economically manufactured. We report here the results of a series of optical performance measurements, including wavefront phase and Strehl ratio. Designed for a wavelength of 650nm, it has less than 0.05 waves of wavefront error, Strehl ratios as high as 98%, efficiency of 89%, and circularity >0.95. The lenses have low aberrations and high throughput with a circular cross section. These lenses are ideal for use in applications such as optical data storage, fiber coupling, and any application in which degraded performance is due to an elliptical beam.
Technological advancements in the field of mixing layer theory have allowed the design and subsequent construction of a Table Top Simulator of Aero-Optic Effects. This experimental facility simulates the supersonic boundary and mixing layers formed by the window coolant gas of an optically guided hypersonic vehicle. This paper discusses the foundations of wave-optic theory applied to model the propagation of optical radiation through such flow. The focus of the calculations is to determine performance quality parameters such as Strehl ratio, jitter, 50 percent contained energy diameter and boresight error. These quality measures will drive the performance requirements of the optical system and focal plane array of the seeker. Comparisons are made between wave-optic model results and actual aero-optic data collected from the Table Top experiment.
Proc. SPIE. 1326, Window and Dome Technologies and Materials II
KEYWORDS: Defense and security, Diffraction, Point spread functions, Error analysis, Computer programming, Ray tracing, Modulation transfer functions, Geometrical optics, Aerodynamics, Systems modeling
Advances made in the field of aero-optical system modeling are applied in the technology of super- or hypersonic
vehicles carrying optical seekers. The fundamentals discussed form a basis for performance predictions of these airborne
optical systems. The focus is the inherent image degradation due to aerodynamic mixing layers.
This paper examines the aero-optic properties of supersonic mixing layers. Recent experimental results on the aerophysics
of supersonic mixing layers is combined with statistical aero-optics theory to create empirical equations governing
the image degradation resulting from light propagating through a classical mixing layer. This model results in simple
expressions for blur circle size, Strehl loss, jitter and boresight error. Expressions for the turbulent Modulation Transfer
Function (MTF) and the Point Spread Function (PSF), assuming a diffraction-limited optical system, can also be