Abstract: A laser beam stabilization module that has a tilt compensation device and a separate displacement compensation device. Each compensation device is coupled to a feedback loop to correct for tilt and displacement errors in a laser beam stabilized by the module. Providing a pure displacement compensation device eliminates the additional tilt error found in two mirror stabilization modules of the prior art.

Abstract: An optical beam scanner. The scanner includes a beam centering device that directs a light beam onto a beam scanning device. The beam centering device can compensate for positioning errors in the light beam. The scanning and centering device may each have feedback loops used to control the scanning and position of the beam, respectively.

Abstract: A system that can track a beam of light onto a target moving on a table. The system may include a table that moves the target and a light source which emits a beam of light that is directed onto the target. The system may further have a beam steering element that is in the optical path to re-direct the beam and track the movement of the target. In one embodiment the system includes a controller which determines an error signal from a desired position of the target and an actual position of the target. The error position is transmitted to the beam steering element to re-direct the beam and track the moving the target.

Abstract: An ultrasound detection system that is relatively insensitive to rough workpiece surfaces, suppresses low frequency noise, and provides high sensitivity without the need for active stabilization. An optical probe beam is reflected and phase modulated by a workpiece surface that is being vibrated by ultrasound. A time-delay interferometer optically interferes the phase modulated probe beam with a time-delayed replica of itself. The optical interference generates optical interference fringes that move in accordance with the workpiece surface velocity. The interference fringes are detected by a non-steady-state photo-electromotive-force (NSS-photo-EMF) detector that generates an output signal when the frequency of fringe motion exceeds a predetermined threshold.

Abstract: A laser-ultrasonic inspection system is provided for on-line and off-line inspection of a workpiece. The system utilizes an optical acoustic wave generation and detection system with relatively high spatial resolution and which appreciably reduces the effects of parasitic acoustic coupling. An array of acoustic waves are generated in the workpiece by a short pulse optical transmitter bee with a beam geometry that is tailored to focus the acoustic waves at an inspection site in the workpiece. The acoustic waves that probe the inspection site are then detected by reflecting an optical read-out beam from a surface of the workpiece and optically interfering it with an optical reference beam. The geometry of the optical read-out beam is chosen such that the read-out beam only detects the acoustic waves that arrive from the inspection site (acoustic waves that arrive from other parasitic acoustic sources are out of phase with respect to each other and cancel out).

Abstract: An optical self-referencing ultrasonic receiver for detecting ultrasonic waves removes wavefront distortions imparted on the optical beams by diffusely reflecting readout surfaces or other sources, compensates for noise induced phase errors on the readout beam, compensates for amplitude noise present on the readout beam, substantially matches the wavefronts of the readout and reference beams, is capable of operating in a heterodyne mode and is self-aligning. In one embodiment, ultrasonic waves are measured by directing a signal beam and a reference beam to a surface of the workpiece so that the signal beam reflects off an area that is being vibrated by the ultrasonic waves, and the reference beam reflects off a different area of the surface. The signal beam gets phase modulated by the ultrasonic wave induced vibrations and also by other noise induced vibrations. The reference beam only gets phase modulated by the noise induced vibrations.

Abstract: A spatial light modulator that is particularly suited for adaptive optics systems includes a charge transfer plate in which accumulated charge is continuously drained from the charge transfer pins, allowing the modulator to be operated in a continuous mode with a very rapid speed of response. Charge is drained through RC circuits that consist of inherent or discrete resistors and inherent capacitances associated with the pins. A lenslet array focuses an input beam onto the curvature bases of pixels in an associated deformable mirror, thereby obtaining reflections from the mirror with generally flat wavefronts and a greatly increased optical efficiency; a companion lenslet array and mirror combination outside the SLM compensates pixel inversions produced by the first lenslet array.