Photonics & Imaging

A combination of pulsed-source interferometry and acoustic diffraction has been proposed for use in imaging subsurface microscopic defects and other features in such diverse objects as integrated-circuit chips, specimens of materials, and mechanical parts. A specimen to be inspected by this technique...

A method of measuring the fraction of bacterial spores in a sample that remain viable exploits DPA-triggered luminescence of Tb3+ and is based partly on the same principles as those described in the immediately preceding article. Unlike prior methods for performing such live/dead...

Digital signal fanout is a very common requirement in testing, experimentation, and systems integration. Unlike radio frequency signals, high-speed digital signals cannot be simply split or "teed" off to multiple destinations. Even with a matched-impedance splitter, the resulting amplitude loss...

Reversible, colorimetric fiber-optic sensors are undergoing development for use in measuring concentrations of ammonia in air at levels relevant to human health [0 to 50 parts per million (ppm)]. A sensor of this type includes an optical fiber that has been modified by replacing a portion of its cladding with a polymer...

Laser Ranging Simulation Program (LRSP) is a computer program that predicts selected aspects of the performances of a laser altimeter or other laser ranging or remote-sensing systems and is especially applicable to a laser-based system used to map terrain from a distance of several kilometers. Designed to run in a...

The simple addition of a charge-coupled-device (CCD) camera to a theodolite makes it safe to measure the pointing direction of a laser beam. The present state of the art requires this to be a custom addition because theodolites are manufactured without CCD cameras as standard or...

An electronic system based on long-wavelength infrared (LWIR) sensors is being developed to detect aircraft flying near an upward-aimed, high-power laser beam. In the intended application, the system would alert a human laser operator and/or generate a signal to turn off the laser whenever...

A rugged laser-diode oxygen sensor is being developed for detecting leaks of oxygen from diverse systems, including rocket engines, cryogenic systems, and medical equipment. The sensor is required to have a range of 250 to 250,000 parts per million, to be accurate within 5 percent, to be capable of operating at any...

A method of characterization of growing of protein crystals involves the utilization of an optical imaging technique known as spatial phase imaging. The methods used heretofore have been, variously, invasive (e.g., adding a dye that is absorbed by the protein of interest), destructive (e.g.,...