Abstract: An optical signal transmission circuit for a probe is switched on by an optical switch-on signal comprising a burst 42 of pulses having a predetermined length. This is detected by a circuit which discriminates whether an input signal is a genuine switch-on signal or an interference burst 44, on the basis of the duration of the switch-on signal.

Abstract: The invention is an instrument for sensing the state of polarization (SOP), and for transforming the SOP of a beam of light from an incident continuously-varying arbitrary SOP to a desired exit SOP, using a polarization compensator under feedback control. A polarization sensor uses two or three samples of a beam to sense the Poincare sphere latitude and longitude error in SOP. A polarization controller adjusts the SOP of light, which is then sensed by the polarization sensor, which develops signals to drive the polarization compensator using feedback methods. Unlike prior-art systems, the feedback seeks a mid-point rather than an extremum in the sensed signals, so there is no sign ambiguity in the feedback control. Further, the sensor signals indicate orthogonal displacements in SOP that correspond to specific elements in the polarization controller, so there is no ambiguity as to which element needs adjustment in order to correct a given error in SOP.

Abstract: Apparatus and methods are disclosed for measuring a surface profile and/or a wavefront aberration of a target object. Exemplary target objects include mirrors, lenses, and lens systems. A representative apparatus configuration includes a light source, a light-flux optical system, a phase-state changing device, a detector, and a computer. The light-flux optical system (i) produces, from a light flux produced by the light source, measurement-light and reference-light fluxes, (ii) directs the measurement-light flux to the target object, (iii) provides the reference-light flux with a standard wavefront, and (iv) establishes interference between the two light fluxes. The phase-state changing device changes a phase state of the reference-light flux and/or the measurement-light flux relative to a respective standard. The detector detects interference fringes.

Abstract: An interferometric instrument that includes a radiation generating unit for emitting briefly coherent radiation is used for sensing the surfaces of a test object by determining an interference maximum. Precise determination of the interference maximum, and therefore precise sensing of the test object, are achieved by providing, in the optical path of the first beam component and/or in the optical path of the second beam component, an arrangement which produces a frequency shift between the two interfering beam components and by providing a beam splitting arrangement, located in front of the photodetector arrangement in the optical path of the interfered radiation upstream from the photodetector device, which can be used to split the beams into at least two spectral components and supply them to the photodetector arrangement either directly or via additional elements on the photodetectors assigned to the components.

Abstract: A technique and apparatus for non-contact scanning measuring of the dynamic parameters of micro and macro devices using an acousto optic scanning laser vibrometer are disclosed. The system includes an acousto optic deflector to induce scanning in the laser beam. The apparatus also includes either a heterodyne or homodyne system for laser scanning. The heterodyne detection technique involves two acousto optic deflectors driven by a common signal generator. The invention may include an interference technique in which the measuring scanning beam emitted by the acousto optic deflector interferes with the reference-scanning beam. For some applications, this acts as a second measuring beam. With this technique, the frequency shift induced in the laser beam on scanning with the acousto optic deflector is canceled due to fact that the two acousto optic deflector are of same specification and driven by a common driver. The invention may also include an apparatus and technique for homodyne detection.

Abstract: An interferometric instrument for sensing the surfaces of a test object includes a radiation generating unit for emitting briefly coherent radiation and a first beam splitter for producing a first and second beam component. One beam component is aimed at the surface to be sensed and the other beam component is aimed at a device with a reflective element for periodically changing the light path. The instrument also has an interference element which causes the radiation coming from the surface and the radiation coming from the reflecting device to interfere with one another and a photodetector which receives the radiation. A simple design is used to achieve a highly accurate measurement by providing an arrangement which produces a frequency shift between the two interfering beam components in the optical path of the first beam component and/or in the optical path of the second beam component.

Abstract: An interferometric instrument for sensing the surfaces of a test object includes a radiation generating unit for emitting briefly coherent radiation and a first beam splitter for producing a first beam component and a second beam component. One beam component is aimed at the surface of the test object, and the other beam component is aimed at a device with a reflecting element for periodically changing the light path. The instrument also has an interference element which causes the radiation coming from the surface and the radiation coming from the device to interfere with one another, and a photodetector which receives the radiation. With a simple design, it is possible to increase the measuring accuracy by providing the device for changing the light path with an arrangement producing a parallel shift positioned in the optical path, followed by a stationary reflecting element.

Abstract: Described is a method of interferometric measurement of positions and position changes, as well as physical quantities derived therefrom, of a part to be tested using heterodyne interferometry, with a laser being modulated to change the frequency of the radiation emitted by it using a time-variable pulsating injection current in order to generate the heterodyne frequency, and one portion of the emitted radiation is routed via an optical bypass, while the other portion is routed without the optical bypass to the part and, from there, to a measuring receiver. Improved evaluation of the measurement results is achieved with smaller dimensions due to the fact that the signal shape of the injection current has a rising edge that is steep compared to its pulse length and a subsequent plateau.

Abstract: An interferometer comprises a non-uniform beam splitter (34) which splits an incoming beam (30) of energy into two beams (36, 38). The two beams (36, 38) are taken from parts of the incoming beam (30) which overlap. The two beams (36, 38) are fed spacially separated energy feeds (44, 46) and then fed to a comparator to produce sum and difference channels (54, 58). The sum and difference channels (54, 58) are guided to a means for detecting a difference in phase (60) between the sum and difference channels (54, 58).

Abstract: A spectrum analyzer for producing a first two-dimensional array of time varying spectral analysis image input signals, a reference image generator for producing a second two-dimensional array of spectral analysis image reference signals, and a time-integrative correlator, which can be non-coherent or coherent, or correlating the two groups of image representitive signals to determine the degree of matching between an input image and a library reference image. The spectrum analyzer can include an interferometer, a tunable optical filter, or a time-wavelength-multiplexing holographic lens for viewing the input image. A monolithic non-holographic version provides a rugged, compact and portable image analyzer for examining many types of images.

Abstract: An improved confocal microscope system is provided which images sections of tissue utilizing heterodyne detection. The system has a synthesized light source for producing a single beam of light of multiple, different wavelengths using multiple laser sources. The beam from the synthesized light source is split into an imaging beam and a reference beam. The phase of the reference beam is then modulated, while confocal optics scan and focus the imaging beam below the surface of the tissue and collect from the tissue returned light of the imaging beam. The returned light of the imaging beam and the modulated reference beam are combined into a return beam, such that they spatially overlap and interact to produce heterodyne components. The return beam is detected by a photodetector which converts the amplitude of the return beam into electrical signals in accordance with the heterodyne components. The signals are demodulated and processed to produce an image of the tissue section on a display.