Abstract: A system and method that use a fluid gauge proximity sensor. A source of modulated unidirectional or alternating fluid flow travels along at least one path having a nozzle and a flow or pressure sensor. The fluid exists at a gap between the nozzle and a target. The sensor outputs an amplitude modulated signal that varies according to a size of the gap. The amplitude modulated signal is processed either digitally or in analog devices, which can include being filtered (e.g., band pass, band limited, high pass, etc. filter) to include the modulated frequency and sufficient bandwidth on either side of that frequency and/or being demodulated using a demodulator operating at the acoustical driver modulation frequency. Using this system and method can result in only ambient acoustical energy in a desired frequency range of the device actually having the opportunity to interfere with the device operation. This can lower the devices overall sensitivity to external acoustical noise and sensor offset.

Abstract: A gas gauge proximity sensor modulates a gas stream that is used to feed reference and measurement air gauges, respectively, in a reference portion proximate a reference surface and a measurement portion proximate a measurement surface. The gas stream can be modulated at a frequency at which there is minimal acoustical interference energy (e.g., minimal noise) in demodulated output signal. The sensor output can be filtered so that a measurement signal includes only the modulated frequency and side bands of that frequency to include the desired response band of the device as a whole. The filtered signal can be demodulated using a demodulator operating at a same frequency as the modulator to produce the demodulated output signal. In this embodiment, substantially only ambient acoustical energy in the band pass region may interfere with the device operation. Alternatively, the modulation can be introduced through the reference portion. A reference nozzle sets up a pressure field with the reference surface.

Abstract: A linear displacement interferometer system employs glass wedge prisms (71, 73, 75, 76) diposed about the interferometer axis of symmetry to refract the beams (51A, 55A) produced by the interferometer onto a single area (72, 86) approximately the size of the interferometer beam. If only one spot is produced on each of the stage and reference mirrors (72, 86), then any ambiguity concerning the beams (51B, 55B) is eliminated. In the preferred system, the stage (72) and standard (86) mirrors are located where the refracted beam crosses an interferometer axis of symmetry (80).

Abstract: An angular displacement interferometer system capable of measuring accurately changes in angular displacement comprises a source (10) of a frequency stabilized input beam with two linear orthogonally polarized components; a tilted parallel plate or shear place (16) with regions of reflection, antireflection, and polarizing coatings for converting the input beam (12) into two separated, parallel, orthogonally polarized beams (30, 31); a half-wave retardation plate (29) located in one of the separated beams (31) for converting the two separated, parallel, orthogonally polarized beams (30, 31); into first and second beams which are spatially separated parallel, and have the same polarization (30, 33); a polarizing beamsplitter (40) and quarter-wave retardation plate (44) for transmitting the first and second beams (34, 35) to a fixed plano mirror (70) nominally perpendicular to the first and second beams for reflecting the first and second beams back into the quarter-wave retardation plate (44), polarizing beams

Abstract: A system and method that use a fluid gauge proximity sensor. A source of modulated unidirectional or alternating fluid flow travels along at least one path having a nozzle and a flow or pressure sensor. The fluid exists at a gap between the nozzle and a target. The sensor outputs an amplitude modulated signal that varies according to a size of the gap. The amplitude modulated signal is processed either digitally or in analog devices, which can include being filtered (e.g., band pass, band limited, high pass, etc. filter) to include the modulated frequency and sufficient bandwidth on either side of that frequency and/or being demodulated using a demodulator operating at the acoustical driver modulation frequency. Using this system and method can result in only ambient acoustical energy in a desired frequency range of the device actually having the opportunity to interfere with the device operation. This can lower the devices overall sensitivity to external acoustical noise and sensor offset.