Abstract: Described is a multiple channel interferometric surface contour measurement system. The measurement system includes a multiple channel interferometer projector, a digital camera and a processor. The projector includes two or more interferometer channels. Each channel has an optical axis spatially separate from the optical axes of the other channels. Each channel projects a fringe pattern onto the surface of an object to be measured. Image data for the fringe patterns projected on the object surface are acquired by the digital camera. The processor controls the projection of the fringe patterns of different spatial frequencies, adjusts the phase of each fringe pattern and generates surface contour data in response to the camera image data. The multiple channel interferometric surface contour measurement system provides numerous advantages over conventional single channel interferometric systems, including reduced sensitivity to optical noise, improved stability and increased measurement accuracy.

Abstract: Described is a fringe generator for an interferometric measurement system having improved fringe stability and reproducibility. The fringe generator includes a light source at a characteristic wavelength and a diffractive element to generate a pair of diffracted beams from light received from the light source. The fringe generator also includes a lens to receive the pair of diffracted beams and to image the plane of the diffractive element onto an object to be measured. The generated fringe pattern is substantially independent to a change in the position of the light source relative to the lens and a change in the characteristic wavelength of the light source. A broadband light source can be used and the resulting broadband fringe pattern is substantially independent to a change in the position of the light source relative to the lens and to a change in the spectral distribution of the broadband light source.

Abstract: Described is a fringe generator for an interferometric measurement system having improved fringe stability and reproducibility. The fringe generator includes a light source at a characteristic wavelength and a diffractive element to generate a pair of diffracted beams from light received from the light source. The fringe generator also includes a lens to receive the pair of diffracted beams and to image the plane of the diffractive element onto an object to be measured. The generated fringe pattern is substantially independent to a change in the position of the light source relative to the lens and a change in the characteristic wavelength of the light source. A broadband light source can be used and the resulting broadband fringe pattern is substantially independent to a change in the position of the light source relative to the lens and to a change in the spectral distribution of the broadband light source.

Abstract: The present invention provides a method and apparatus for reducing error in interferometric fringe stability and reproducibility in an interference fringe generator. In one aspect, the method for reducing error in interferometric fringe stability and reproducibility includes providing a light source, positioning a grating to receive light from the light source and positioning a projection lens having a focal length F to receive light from the grating. The projection lens projects the received light upon an object of interest positioned substantially at a distance d1 from the lens. Typically the lens is positioned substantially at a distance d2 from the grating. The values of d1, d2, and F are related by d2 being approximately equal to d1F/(d1?F).