Abstract: An external cavity diode laser may have an output wavelength that is tuned by an end mirror mounted on an element having a flexure hinge. The flexure hinge may be designed to exhibit a stationary pivot point over a desired tuning range, and may allow the external cavity to be tuned without the laser hopping between longitudinal modes. Chromatic dispersion of the laser medium may be accommodated by adjusting a distance between a laser diode and a grating included within the external cavity. The position may be adjusted to find an operating configuration which allows mode-hop-free tuning over the entire desired tuning range.

Abstract: An interferometer comprises a wavelength-variable light source. A reference light and a measurement light are synthesized, and the synthesized light is split into a plurality of split lights. A certain phase difference is provided between the split lights through phase shifting optical members. A plurality of interference fringe images formed by the phase-shifted split lights are captured at an imaging unit. Biases, amplitudes and the amounts of phase shift of the interference fringes formed by the plurality of split lights are calculated, based on interference fringe intensities of the imaged interference fringes, which are obtained by disposing a calibrating substrate instead of the measuring object varying the wavelength of the emitted light to plural values, and operating the imaging unit to capture a plurality of images of interference fringes obtained by the split lights.

Abstract: A method of determining an amount of tilt may include projecting at least two coherent wavefronts toward a target surface, the wavefronts reflecting from the target surface to create an interference fringe pattern on a detector, and transmitting a beam toward the target surface, the transmitted beam reflecting from the target surface to form a beam spot on the detector. A fringe pitch indicative of a distance to the target surface may be determined based on the interference fringe pattern. A displacement on the detector of the beam spot, relative to a nominal location of the beam spot when the target surface is at a nominal angle of incidence relative to the beam, may be determined. The amount of tilt of the target surface relative to the nominal angle of incidence, may be determined based on the displacement of the beam spot and the determined fringe pitch.

Abstract: A wavelength-variable light source is configured to emit a light with a wavelength (?), which is variable within a scan width (??). An interferometer has a coherent length (?L), which is determinable from (??) and (?). A controller determines an appropriate magnitude of the scan width (??) while a CCD camera captures a fringe image in an exposure time (Te), which is set longer than a time for wavelength scanning.

Abstract: An external cavity laser has an external cavity that is formed between a target surface and a laser diode facet located farthest from the target surface. A chromatic dispersive element is disposed in the external cavity, and focuses light from the laser diode such that one wavelength is focused at a focal spot on the target surface. Light reflected from the focal spot on the target surface is the predominant wavelength coupled back into the laser waveguide, which provides a feedback signal that determines the oscillation wavelength of the laser diode. The laser diode therefore outputs a well-defined wavelength of light which corresponds to the distance between the chromatic dispersive element and the target surface.

Abstract: A compact monolithic quadrature detector generates four signals from an input beam including orthogonally polarized object and reference beam components provided by an interferometer. The single input beam may be split into four output beams using a first beam splitting interface between two prisms, reflections at two air interface surfaces of the prisms, and a second beam splitting element. Different respective predetermined phase shifts may be imposed on the respective output beams by coatings on the beam splitting surfaces, which impart a different phase shift to the components of a transmitted beam as compared to a reflected beam. The four relatively phase shifted output beams may be directed through polarizers onto respective detectors to provide four signals usable to eliminate many common mode errors and determine the phase difference between the components of the original input beam with high accuracy.

Abstract: An absolute distance measuring device based on laser interferometry may combine coarse, intermediate, and highest resolution measurement techniques to find the absolute distance to a sample surface with high resolution. The device may provide at least two laser wavelengths simultaneously, to allow reduction or elimination of certain common-mode error components, including dynamic error components. The device may scan at least one of the laser wavelengths over a relatively narrow range and may use quadrature detectors to provide enough signal data to allow certain self-corrections to be performed on the resulting scanned signals and measurements. A novel tunable laser and/or quadrature detector may provide advantages in combination with the device.

Abstract: An external cavity laser has a wavelength of the laser output that is tuned by a rotary tuning element mounted on the axle of a motor. The rotary tuning element includes a variable thickness interference film for wavelength selection, and a variable thickness compensation prism to adjust the cavity length appropriately for the selected wavelength, to stable wavelengths and mode-hop-free tuning ranges as the tuning element is rotated.

Abstract: The invention comprises a liquid crystal Fabry-Perot interferometer tuned external cavity semiconductor laser. The laser oscillates single mode at a discrete set of wavelengths defined by the transmission of an intracavity static Fabry-Perot etalon. The liquid crystal Fabry-Perot interferometer has a free spectral range larger than the gain bandwidth of the laser amplifier so that it selects only one transmission wavelength. Its resolution bandwidth is much greater than the free spectral range of the external cavity. The static intracavity etalon's free spectral range is greater than the resolution bandwidth of the liquid crystal Fabry-Perot interferometer. The static etalon maintains a single mode oscillation by providing a filter narrow enough to select only one external cavity mode.