Photonics

Robust Mapping of Incoherent Fiber-Optic Bundles

Images scrambled by the bundles can be unscrambled. Marshall Space Flight Center, Alabama A method and apparatus for mapping between the positions of fibers at opposite ends of incoherent fiber-optic bundles have been invented to enable the use of such bundles to transmit images in visible or infrared light. The method is robust in the sense that it provides useful mapping even for a bundle that contains thousands of narrow, irregularly packed fibers, some of which may be defective.

Posted in: Tech Briefs, ptb catchall, Photonics, Briefs

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Compact, Stiff, Lightweight, Quick-Release Clamp

This clamp offers several advantages over a prior toggle-action clamp. The term "COSMOWRAP" denotes a compact, stiff, remotely actuatable, lightweight, quick-release clamp that could be substituted for the larger, heavier, and more-difficult-to-use toggle-action clamp now used in the space shuttle orbiter docking system (ODS) to perform contingency separations. In comparison with prior hand-operated devices designed for the same purpose, the COSMOWRAP is smaller and lighter in weight, yet offers greater capabilities. The COSMOWRAP (see figure) contains no spring and requires no pre-flight calibration or maintenance. The COSMOWRAP is expected to perform well, not only in the space-shuttle application for which it was originally designed, but also in terrestrial applications. Because the design of the COSMOWRAP reduces the force needed for installation or removal and provides for release by the action of one hand, the replacement of the ODS toggle-action clamp by the COSMOWRAP can be expected to contribute to crew safety in the United States space program and on the International Space Station.

Posted in: Tech Briefs, ptb catchall, Photonics, Briefs

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Video-Based Foreign Object Detection

The technique can be applied to any assembly process where inclusion of foreign material can cause harm. The Boeing Company has developed an overhead camera system that can automatically spot small pieces of debris on a work surface that might otherwise go unnoticed. The system automatically analyzes inputs from one or more video cameras to detect undesirable colors representing materials that, if left in place, would degrade part quality. The system uses commercial off-the-shelf hardware and software for low-cost implementation and is currently in use in the Boeing F/A-18 wing production line (see figure). The patent-pending technology, known as foreign-object video detection and alert system and method, is available for license.

Posted in: Tech Briefs, ptb catchall, Photonics, Briefs

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Monolithic Diffraction Grating Arrays Enable Wide-Bandwidth Single-Shot Spectrometers

For the last forty years, manufacturing technology for diffraction gratings has not changed significantly. Mechanical ruling and interferometric (holographic) exposure have been the two predominant approaches used to fabricate gratings. Both approaches provide limited freedom in terms of the complexity of grating lines (spacings and curvatures) that can be written.

Posted in: Features, ptb catchall, Photonics, Articles

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InGaAs SWIR Imagers Optimize Semiconductor Inspection

As the volume of consumer electronics increases, semiconductor fabrication plants are manufacturing larger and larger wafers to handle the demand (e.g., 300 mm substrates). The escalating value of these larger wafers is driving the industry to employ more advanced imaging technologies for quality control. Inspecting the raw material substrate for flaws before processing and detecting defects during processing is critical to keeping costs down. New and improved inspection techniques save the semiconductor manufacturing industry hundreds of millions of dollars each year.

Posted in: ptb catchall, Applications, Photonics, Application Briefs

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Electro-Optical Modulator Bias Control Using Bipolar Pulses

Bias is automatically adjusted to maintain maximum extinction during “off” periods. NASA’s Jet Propulsion Laboratory, Pasadena, California An improved method has been devised for controlling the DC bias applied to an electro-optical crystal that is part of a Mach-Zehnder modulator that generates low-duty-cycle optical pulses for a pulse-position modulation (PPM) optical data-communication system. In such a system, it is desirable to minimize the transmission of light during the intervals between pulses, and for this purpose, it is necessary to maximize the extinction ratio of the modulator (the ratio between the power transmitted during an “on” period and the power transmitted during an “off” period). The present method is related to prior dither error feedback methods, but unlike in those methods, there is no need for an auxiliary modulation subsystem to generate a dithering signal. Instead, as described below, dither is effected through alternation of the polarity of the modulation signal.

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Fiber-Optic Strain Gauge With High Resolution And Update Rate

Changes in strain are correlated with changes in speckle patterns. Stennis Space Center, Mississippi An improved fiber-optic strain gauge is capable of measuring strains in the approximate range of 0 to 50 microstrains with a resolution of 0.1 microstrain. (To some extent, the resolution of the strain gauge can be tailored and may be extensible to 0.01 microstrain.) The total cost of the hardware components of this strain gauge is less than $100 at 2006 prices. In comparison with prior strain gauges capable of measurement of such low strains, this strain gauge is more accurate, more economical, and more robust, and it operates at a higher update rate. Strain gauges like this one are useful mainly for measuring small strains (including those associated with vibrations) in such structures as rocket test stands, buildings, oilrigs, bridges, and dams. The technology was inspired by the need to measure very small strains on structures supporting liquid oxygen tanks, as a way to measure accurately mass of liquid oxygen during rocket engine testing.

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