摘要:
An apparatus is provided for detecting flaws in a threaded bore having at least one thread with a helical root is provided. The apparatus may include a thread engagement member configured to engage the at least one thread of the threaded bore. The apparatus may also include a probe coupled with the thread engagement member. The probe may be configured to direct light onto the helical root of the threaded bore. The probe and the thread engagement member may be adapted to rotate relative to the bore while the probe continually directs light onto the helical thread so that the light sweeps along a section of the helical root.
摘要:
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.
摘要:
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). A wavefront compensation system improves acoustic clutter rejection and also improves the signal-to-noise by compensating for phase and amplitude aberrations induced on the optical read-out beam by the optically rough surface of the workpiece.
摘要:
Associative holography memory apparatus is disclosed which employs a hologram and two phase conjugate mirrors. The mirrors are arranged to form a conjugate resonator whereby the output image from the apparatus tends to converge to that stored image most closely associated with an input image. Alternate embodiments are described which employ a multiple storage and erasure hologram, and which employ only a single phase conjugate mirror.
摘要:
A phase conjugate resonator (PCR) (2) employing a phase conjugate mirror (PCM) (4) provides high resolution spatial detection of individual locations in a two-dimensional optical array which exceed or fall below a threshold level. The optical intensity profile under investigation is imposed onto an input erase beam (18) to the PCM (4). The erase beam (18) is directed parallel to the PCR axis (16), thereby preventing walkoff. The PCR (2) oscillates at those locations where the erase beam's optical intensity is below a threshold level. The spatially modulated optical output may be read out with multiple detectors or an imaging system, or the cumulative area output of the PCR can be read out with a single detector (28) to characterize the intensity profile relative to the threshold.
摘要:
A photo-EMF sensor and a method of making same has a substrate with a semiconducting layer; a plurality of sensing regions in the layer, each sensing region including (i) a pair of electrodes disposed in, on or above the layer and (ii) an active region in the layer disposed adjacent said pair of electrodes; and a plurality of inactive regions in said the arranged between adjacent sensing regions. The inactive regions and the sensing regions are dosed with a desensitizing agent, the inactive regions receiving a relatively higher dose of the desensitizing agent and the sensing regions receiving a relatively lower dose of the desensitizing agent. The active layer is preferably placed in a monolithic Fabry-Perot cavity to enhance the optical efficiency and performance of the sensor.
摘要:
Faults, dimensions and other characteristics of a material or structure are sensed by a coherent beam's reflection from the material during ultrasonic or very fast vibration. The reflected beam acquires a phase substantially different from its original phase and from the phase of a reference beam split from the common source beam. The reflected beam and the reference beam are superimposed by diffraction in a multiple quantum well adaptive holographic beamsplitter, and the superimposed beams are detected by a photodetector capable of detecting small interference changes from ultrasonic surface displacements or perturbations. An apparatus and method defining an improved homodyne interferometer for performing the method is described.
摘要:
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.
摘要:
Optical devices are disclosed which rely upon Stark-induced resonant, tunable, and saturable birefringence and dichroism to provide both digital and linear amplitude optical modulators, optical shutters, tunable optical filters, and optical cutoff limiters. A Stark cell is disposed along a light beam path between two crossed polarizers with its electric field direction at 45.degree. to the polarizer pass directions. The Stark cell contains a medium exhibiting a dichroic absorption resonance at a predetermined frequency as well as birefringence at frequencies slightly above and slightly below the frequency of the absorption resonance. By applying an appropriate control voltage between the Stark cell electrodes, an electric field is generated within the Stark cell to tune the absorption resonance to overlap the frequency of an input laser beam and thereby vary the transmission through the device from maximum near resonance to zero at frequencies far away from resonance.
摘要:
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.