Abstract: A method and apparatus for a photoinduced electromotive force sensor. The sensor has an active substrate formed of a semi-insulating photoconductor with sufficient carrier trap density to form an effective charge grating and pairs of electrodes disposed on the active substrate, where the sensor is configured to reduce the photovoltaic effect caused by the incident light in the vicinity of the electrodes. The shape or composition of the electrodes may be selected to reduce the photovoltaic effect or the electrodes may be disposed on the substrate to average out the photovoltaic effect arising from each one of the electrodes.

Abstract: A method and apparatus for a photoinduced electromotive force sensor. The sensor has an active substrate formed of a semi-insulating photoconductor with sufficient carrier trap density to form an effective charge grating and pairs of electrodes disposed on the active substrate, where the sensor is configured to reduce the photovoltaic effect caused by the incident light in the vicinity of the electrodes. The shape or composition of the electrodes may be selected to reduce the photovoltaic effect or the electrodes may be disposed on the substrate to average out the photovoltaic effect arising from each one of the electrodes.

Abstract: An apparatus and a method for detecting surface motion of an object subject to ultrasound are disclosed. The method comprises generating a laser beam, dividing the laser beam into a reference beam and an object beam to be directed onto the surface, thereby producing a scattered object beam, introducing a frequency shift between the reference beam and the scattered object beam, wherein the frequency shift is smaller than the ultrasonic frequency, detecting the interference between the scattered object beam and the frequency shifted reference beam using a plurality of detecting elements to generate a plurality of electrical interference signals, wherein the electrical interference signals each comprise a wanted signal component indicative of the surface motion and a noise signal component, and processing the electrical interference signals to determine the surface motion of the object.

Abstract: Dynamic vibration monitoring of a cutting tool or workpiece is provided by propagating an ultrasonic carrier beam in a stream of fluid flowing from a probe chamber, which includes a transducer, to the cutting tool or workpiece target area. The modulated ultrasonic beam reflected from the target is detected via a transducer in the chamber, and is demodulated to provide measurements of vibrational surface displacement and velocity. The method is insensitive to the target surface roughness and can be used for dynamic characterization prior to machining, and for monitoring during the machining operation. The device is inexpensive and robust to the machining environment, and can be applied to small cutting tools.

Abstract: Dynamic vibration monitoring of a cutting tool or workpiece is provided by propagating an ultrasonic carrier beam in a stream of fluid flowing from a probe chamber, which includes a transducer, to the cutting tool or workpiece target area. The modulated ultrasonic beam reflected from the target is detected via a transducer in the chamber, and is demodulated to provide measurements of vibrational surface displacement and velocity. The method is insensitive to the target surface roughness and can be used for dynamic characterization prior to machining, and for monitoring during the machining operation. The device is inexpensive and robust to the machining environment, and can be applied to small cutting tools.

Abstract: A laser-based technique to determine glass thickness employs a pulsed laser to induce an ultrasonic wave between the surfaces of a region of glass, causing the surfaces to move in and out at a characteristic frequency. The surface motion is monitored to determine the characteristic frequency, which is proportional to the thickness of the glass in the region of the ultrasonic wave. The pulsed laser produces a short duration pulse that illuminates a surface of the glass, which is absorbed within the glass to cause a rapid thermal expansion that generates the ultrasonic wave. The surface motion induced by the ultrasonic wave is preferably detected with a laser interferometer system, the output of which is analyzed to determine the surface motion's characteristic frequency.