Abstract: A frequency-scanning interferometer is modified to include a diffuse reference surface. An illuminating system produces an expanding measuring beam, portions of which reflect from a test object surface and the diffuse reference surface on converging paths to an imaging system. Interference patterns between overlapping images of the object and reference surfaces are generated at a plurality of frequencies for measuring the object surface with respect to the reference surface.

Abstract: An expanding measuring beam is inserted into a cavity of a frequency-scanning interferometer. The expanding measuring beam encounters non-specular (diffuse) reference and object surfaces so that the reflected light can be imaged with an imaging system of reduced dimension. The compact interferometer is adaptable to a variety of applications. For example, the compact interferometer can be incorporated into a sensor of a multi-stage measuring instrument or into a handheld imager.

Abstract: A system of frequency-scanning interferometry uses a computer system operating in accordance with a program for measuring distances or range, including measuring topographical information about test object surfaces. Interferometric data is detected using a single point detector or an array of such detectors and recorded (stored) in the computer system, and a series of measurements are taken over a range of illumination frequencies. The interferometric data varies in a sinusoidal manner with a change in illumination frequency at interference frequencies corresponding to particular measures of distance or range. A Fourier transform for locating peak interference frequencies is first limited in frequency space and second divided into stages to save processing time. A coarse spacing between Fourier frequency samples is used for a first approximation, and finer spacing between Fourier frequency samples are used in the vicinity of the first approximation to make a second more accurate approximation.

Abstract: A wavelength tuning system adjusts an external cavity of a laser about two orthogonal axes for aligning features of a diffractive optic with a third orthogonal axis about which the diffractive optic is pivoted for providing selected wavelength feedback to the laser. A laser mount supports the laser, and a mounting arm supports both the diffractive optic and a reflective optic in a fixed orientation with respect to each other. A flexural member forms at least part of a connection between the mounting arm and the laser mount in a relative orientation for optically coupling the diffractive optic to the laser within the external cavity. The mounting arm is pivoted with respect to the laser mount about the pivot axis by an actuator for varying a wavelength of a diffracted portion of the output beam returned to the laser without significantly varying an angular orientation of the output beam with respect to the laser mount as reflected from the reflective optic.