Photonics/Optics

Modal Filters for Infrared Interferometry

NASA's Jet Propulsion Laboratory, Pasadena, California Modal filters in the ≈10-μm spectral range have been implemented as planar dielectric waveguides in infrared interfero-metric applications such as searching for Earth-like planets. When looking for a small, dim object (“Earth”) in close proximity to a large, bright object (“Sun”), the interferometric technique uses beams from two telescopes combined with a 180° phase shift in order to cancel the light from a brighter object. The interferometer baseline can be adjusted so that, at the same time, the light from the dimmer object arrives at the combiner in phase. This light can be detected and its infrared (IR) optical spectra can be studied. The cancellation of light from the “Sun” to ≈106 is required; this is not possible without special devices — modal filters — that equalize the wavefronts arriving from the two telescopes.

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

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Taming Residual Bulk Image in CCDs

Residual bulk image (RBI) is a phenomenon observed in certain types of front side-illuminated charge-coupled devices (CCDs). A CCD is an electronic light sensor used in digital cameras. In simplest terms, the sensor exhibits a memory of prior exposures resulting in ghost images appearing in subsequent images. This deferred charge can cause a number of problems in cooled long-exposure scientific applications. At a minimum, the ghost images can create the illusion of a non-existent object (Figure 1, left). Equally serious, they can lead to significant errors in quantitative measurements required for photometric applications.

Posted in: Articles, Features, ptb catchall, Photonics

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Shortwave Infrared - The Latest Weapon in the War on Terror

Keeping one step ahead of our adversaries is top priority for security forces with terrorist threats growing daily around the world. Intelligence, surveillance and reconnaissance are the core situational awareness tools for the global war on terrorism (GWOT). Just as night vision equipment has denied terrorists the cover of darkness for more than a couple of decades, emerging shortwave infrared imaging technology is now removing weather and environmental limitations from the ISR equation.

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

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Specialty Fibers Guide Light When the Going Gets Tough

In spectrometry, the more light gathered the better the results. Yet in many applications, both military and commercial, the need to protect instruments or operators from harsh environments, as well as installation constraints, make conventional line-of-sight optics impractical. Specialty fibers can offer the robustness and light-handling characteristics that such applications require.

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Using Vision Sensors to Eliminate Manufacturing Defects

Supplying parts to the world’s leading automotive companies leaves no room for error. That’s why Miniature Precision Components Inc. (MPC) uses three vision sensors to error-proof the automated assembly of oil-caps at its Prairie du Chien, WI facility. With 41 molding machines ranging in size from 25 to 550 tons, this 100,000 square-foot facility employs about 450 people. MPC’s four manufacturing plants generate approximately $167 million per year supplying the automotive and commercial industries with high-quality injection-molded parts and assemblies such as PCV valves, thermostat housings, and quick-connect ports for emission control systems.

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

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Micromachining with Lasers

Laser micromachining involves using light to remove material. Lasers can also be used in many other applications such as welding, marking, additive manufacturing and surface alteration, but these fall outside the definition. As a general rule, laser micromachining involves working on substrates that are less than 1 mm in thickness — usually much less — and feature sizes that are also less than 1 mm, with the lower end on the order of a few microns.

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Measuring LED and Solid State Lighting Performance

Light emitting diodes (LEDs) and solid state lighting (SSL) products that incorporate LEDs pose many measurement challenges compared with other lighting elements, such as traditional tungsten and fluorescent. Advanced optical radiation measurement equipment and new techniques are often required to determine basic photo-metric and colorimetric parameters for LEDs and SSL products. Updated measurement instrumentation, calibration and performance characterization methods have allowed for improvement in the repeatability and reproducibility of measurements of average LED intensity, total luminous flux and colorimetric quantities. Lower uncertainty, detector-based standards provide a convenient transfer and monitoring from primary measurement standards.

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

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