Frequency multiplexed, multiple channel heterodyne interferometer
AssigneeThe Boeing Company
InventorSteven E. Muenter
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Abstract
A novel technique using an acousto-optic modulator (AOM) as part of a heterodyne interferometer which measures optical path differences between a test signal and a reference signal is disclosed. An array of distinct frequencies are used to drive the AOM, yielding a spatially dispersed array of frequency-shifted subaperture beams of the test signal which are interfered with the wavefront to be measured and then combined with the dispersed reference signal. The frequency shifting of the AOM allows a single detector to collect the beams for signal processing to determine a measurement of the wavefront.
Claims21
An apparatus for capturing measurement information, comprising:
- a beam splitter for splitting a laser beam into a reference beam and a test beam;
- an acousto-optic modulator (AOM) for spatially separating and modulating the test beam into a subaperture array of distinct frequency-shifted beams, each obtaining a unique frequency shift, for applying across a measured element, the AOM driven by a drive frequency array of signal inputs;
- a beam expander for spatially dispersing the reference beam to at least match the subaperture array of the distinct frequency-shifted beams;
- a beam combiner for interfering the subaperture array of the distinct frequency-shifted beams applied to the measured element with the spatially dispersed reference beam;
- optics for directing the interfered subaperture array of the distinct frequency-shifted beams;
- a photodetector for receiving the interfered subaperture array of the distinct frequency-shifted beams to produce an electrical signal from the photodetector carrying the measurement information of the measured element;
- and
- a processor for comparing an array of reference optical path differences derived from the array of signal inputs with the electrical signal from the photodetector to determine the measurement information of the measured element.
A method for capturing measurement information comprising the steps of:
- splitting a laser beam into a reference beam and a test beam;
- spatially separating and modulating the test beam into a subaperture array of distinct frequency-shifted beams, each obtaining a unique frequency shift, driven by a drive frequency array of signal inputs;
- applying the subaperture array of the distinct frequency-shifted beams across a measured element;
- spatially dispersing the reference beam to at least match the subaperture array of the distinct frequency-shifted beams;
- interfering the subaperture array of the distinct frequency-shifted beams with the spatially dispersed reference beam;
- directing the interfered subaperture array of the distinct frequency-shifted beams onto a photodetector to produce an electrical signal from the photodetector carrying the measurement information of the measured element;
- and
- comparing an array of reference optical path differences derived from the array of signal inputs with the electrical signal from the photodetector to determine the measurement information of the measured element.
An apparatus for capturing measurement information comprising:
- a beam splitting means for splitting a laser beam into a reference beam and a test beam;
- a modulating means for spatially separating and modulating the test beam into a subaperture array of distinct frequency-shifted beams, each obtaining a unique frequency shift, applied across a measured element;
- a dispersing means for spatially dispersing the reference beam to at least match the subaperture array of the distinct frequency-shifted beams;
- a beam combiner means for interfering the subaperture array of the distinct frequency-shifted beams with the spatially dispersed reference beam;
- an optical means for directing the interfered subaperture array of the distinct frequency-shifted beams;
- a photodetecting means for receiving the interfered subaperture array of the distinct frequency-shifted beams to produce an electrical signal from the photodetecting means carrying the measurement information of the measured element;
- and
- a processor means for comparing an array of reference optical path differences derived from the array of signal inputs with the electrical signal from the photodetecting means to determine the measurement information of the measured element.
Dependencies are inferred from the claim text.