A camera capable of obtaining single snap-shot, quantitative, polarimetric measurements is investigated to determine
performance characteristics. The camera employs a micropolarizer array with linear polarizers oriented at 0, 45, 90, and,
135 degrees. Micropolarizer arrays with elements as small as 7.4 microns and arrays as large 4 million pixels have been
fabricated for use across the visible spectrum. The pixelated polarization camera acquires the four polarization
orientations in a single video frame, which enables instantaneous measurements of the linear Stokes parameters.
Examples of calibration methods and the results of controlled experiments are presented. Error sources and methods for
minimizing them are discussed and demonstrated. A practical example of measuring stress induced birefringence is
demonstrated.
Spectrally tunable liquid crystal filters provide numerous advantages and several challenges in space applications. We
discuss the tradeoffs in design elements for tunable liquid crystal birefringent filters with the special considerations
required for space exploration applications. In this paper we present a summary of our development of tunable filters for
NASA space exploration. In particular we discuss the application of tunable liquid crystals in guidance navigation and
control in space exploration programs. In conclusion, the current state of the art of several NASA LaRC assembled
filters is presented and their performance compared to the predicted spectra using our PolarTools modeling software.
We present a binary reflective spatial light modulator (SLM) constructed using a patented ferroelectric liquid crystal (FLC) technique. The device is built atop a planarized 0.6 micrometer CMOS SRAM backplane with 15 micrometer pixel pitch and 88% fill factor. The device achieves better than 25% optical throughput when used with collimated laser light and better than 100:1 contrast when oriented for amplitude modulation. When oriented for phase modulation, the device achieves 180 degrees of phase shift between its 2 states. The device can be operated as fast as 5 kHz with complete switching of the liquid crystal. Applications in the fields of optical computing and optical information processing are suggested.
Recent advances in CCD fabrication techniques have brought on the omnipresence of low cost monochrome CCD cameras. Full color cameras are traditionally made in one of the following two ways: subpixelated color or multiple camera schemes. Each system offers a unique set of tradeoffs. Noteworthy among these is the prohibitive expense of high resolution full color image capture systems. We present a novel technqiue for transforming a single (monochrome) high resolution CCD camera into a full color camera via the use of a fast switching ferroelectric four state color filter. Using all off-the-shelf componentry and color balancing software, we present full color images of stationary scenes constructed from their respective RGB space images.
Spatial light modulators (SLMs) form the heart of several current and future optical technologies. These include but are not limited to optical memories, adaptive optics or wavefront correction, active optical elements, femtosecond pulse shaping, neural nets and, of course, optical computing. Over the past 20 years many interestng and technically viable modulators have been developed. However, as none of these areas have yet to breach into high volume consumer markets, affordable high quality SLMs have been euphemistically 'scarce'. The intent of this paper is to assimilate information on a variety of SLM technologies and to explore their advantages and disadvantages, be they real or perceived. We mention several new technolgies; however, the main emphasis is on devices which are currently commercially available.
Miniature optical correlators provide a means of portable real-time pattern recognition. Most of the attention has been given to reducing length with little consideration to system robustness. Although it is recognized that aberrations will limit system performance, more critical limitations are alignment and sensitivity considerations. This paper presents a procedure for the design of a short robust optical correlator. Theoretical limits on system miniaturization are restricted to component availability; however, practical limitations are dictated by physical constraints and alignment tolerances. This paper explores engineering trade-offs among length, alignability, aberrations, and system reliability. In addition, a complete system analysis including performance, aberrations, and sensitivity is presented.
Implementation of a liquid crystal television (LCTV) for a binary phase only converging beam Vander Lugt correlator system is described. The peculiar pixel array structure of the LCTV characterized by diffraction, scaling, and sampling is presented in a generalized form that can be easily adapted to any pixelated spatial light modulator. It is concluded that twisted nematic LCTV has a potential for becoming an effective and inexpensive spatial light modulator. The twisted nematic LCTV is capable of providing both continuous amplitude and phase modulation and can be used for a variety of real-time optical pattern recognition applications.
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