A small rugged interferometer was required for measuring the depletion zones generated in a protein crystal growth experiment. The exploration for an optimum solution yielded an instrument that uses solid optical design techniques, where air is removed from the optical path and replaced with 'solid air' or glass. The interferometer is a Mach-Zehnder configuration with the reference and test arms separated as orthogonal polarization states with a polarization beam splitting cube (PBSC), then recombined by another PBSC, maintaining the orthogonality of the reference and test beam polarizations. An off-the-shelf liquid crystal variable phase plate was sufficient to produce the necessary 2(pi) phase shift. The device was built and tested and shoed excellent performance. The spatial resolution of the interferometer is limited only by the 0.011mm pixels at the 5 by 5 mm detector and the imager is operating at telecentric 1:1 conjugates. Phase resolution, using the Hariharan 5-step algorithm, is measured to be better than (lambda) /50. In this paper, calibration test results are presented and future upgrades are outlined.
KEYWORDS: Signal processing, LIDAR, Radar signal processing, Optoelectronics, Digital signal processing, 3D vision, Signal generators, Receivers, Laser systems engineering, Radar
Coherent laser radar receivers often generate electronic signals having very wide information bandwidths. 50 MHz bandwidths are routine and 2 GHz bandwidths are not uncommon. Processing wide bandwidth data to remove noise and to extract the required information can exceed the practical limits of electronic techniques. This paper presents the results of the development of an optoelectronic signal processing system for a coherent laser radar system. The system can accommodate signals up to 500 MHz having a duration as short as 17 microseconds or as long as 143 milliseconds.
KEYWORDS: Signal processing, LIDAR, Radar signal processing, Optoelectronics, Digital signal processing, Signal generators, Acousto-optics, Receivers, Laser systems engineering, Optical signal processing
Coherent laser radar receivers often generate electronic signals having very wide information bandwidths. 50 MHz bandwidths are routine and 2 GHz bandwidths are not uncommon. Processing wide bandwidth data to remove noise and to extract the required information can exceed the practical limits of electronic techniques. This paper presents the results of the development of an optoelectronic signal processing system for a coherent laser radar system. The system can accommodate signals up to 500 MHz having a duration as short as 17 microseconds or as long as 143 milliseconds.
an acousto-optic signal processor (AOSP) has been developed for use with laser-based velocity measurement instruments. It has been demonstrated with Doppler laser radar and laser velocimeter systems. Due to its inherent ability to display information about its entire spectral range without post-processing of data, the AOSP is deemed to be superior to conventional spectrum analyzers for some applications.
KEYWORDS: Sensors, LIDAR, Heterodyning, Oscillators, Signal detection, Wavefronts, Laser applications, Analytical research, Signal to noise ratio, Electric field sensors
A generalized model for the calculation of heterodyne efficiency has been developed. The model permits the calculation of the mixing efficiency for arbitrary amplitude profiles, wave front descriptions, and angles of incidence. The model is used to calculate the heterodyne efficiency of a CO2 coherent laser radar as a function of amplitude profile, image translation, wave front tilt and curvature. Analytical results are used to develop a concise set of selection rules for coherent laser radars.
An internal research and development program at Teledyne Brown Engineering has produced a laser radar device to measure velocities of projectiles as they travel through the barrel of a gun. The technique measures velocities directly via the Doppler shift imposed on a retro- reflected laser beam. The device, called the In-Bore Chronograph (IBC), is believed to be the first coherent laser radar to be offered commercially. The IBC measures in-bore velocities from 5 to 2500 m/sec.
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