Multiple channel interferometric surface contour measurement system

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.

1 . A crossbar for improved orientation stability between two system components in an interferometric measurement system, comprising:
 an outer cylindrical tube having a tube axis, an inner surface and two ends;   an inner cylindrical tube having a tube axis collinear with the tube axis of the outer tube and having an outer surface and two ends, the inner cylindrical tube disposed inside the outer tube and extending outside the two ends of the outer cylindrical tube, each end of the inner cylindrical tubes adapted for attaching one of the system components; and   a pair of O-rings disposed between the inner surface of the outer cylindrical tube and the outer surface of the inner cylindrical tube, each O-ring being disposed along a length of the inner cylindrical tube at a predetermined position to reduce changes in the orientation between the two system components as the crossbar is reoriented.   
   
   
       2 . The crossbar of  claim 1  wherein the outer cylindrical tube and the inner cylindrical tube are manufactured from materials having similar coefficients of thermal expansion. 
   
   
       3 . The crossbar of  claim 1  wherein the outer cylindrical tube and the inner cylindrical tube are manufactured from aluminum. 
   
   
       4 . The crossbar of  claim 1  further comprising a mounting plate secured to the outer tube.