Interferometric laser profilometer including a multimode laser d

Details Interferometric laser profilometer including a multimode laser d Interferometric laser profilometer including a multimode laser d

1992-08-07

1994-09-20

Turner, Samuel A.

Optics: measuring and testing

By particle light scattering

With photocell detection

356357, 356360, G01B 902

Patent

active

053494407

ABSTRACT:
Metrology method and apparatus (10) for determining a characteristic of an object's surface. The apparatus includes a multiple wavelength source (12) having an optical output. The source is comprised of a multimode laser diode (18) for simultaneously providing a plurality of wavelengths from which a synthetic wavelength is derived for metrology purposes. The apparatus further includes a beamsplitter (30), preferably a polarizing beam splitter, coupled to the optical output for providing a reference beam (32) and a measurement beam (34), the measurement beam impinging on the surface and the reference beam being phase modulated. The apparatus also includes optical elements and devices for detecting a phase difference between the reference beam and a reflected measurement beam for determining the characteristic of the surface. A diffraction grating (60) is blazed for a nominal characteristic output of the laser diode, such as 785 nanometers, and spatially resolves the various wavelengths of the returned laser light. The resolved wavelengths are provided as two beams by a lens system (62) and are detected by a pair of photodetectors (64, 66). A data processor ( 68) coupled to an output of the photodetectors determines an interferometric phase at the two wavelengths and the surface characteristic.

REFERENCES:
patent: 5153669 (1992-10-01), DeGroot
"Two-Wavelength Speckle Interferometry on Rough Surfaces Using a More Hopping Diode Laser", Fercher, Optics & Lasers in Engineering, 1989, 271-279.
"Absolute Optical Ranging with 200-nm Resolution", Williams et al, Optics Letters, Jun. 1989, 542-544.

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