Multiple Channel Interferometric Surface Contour Measurement System

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 tube 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.

A method for determining position information for a surface of an object, the method comprising:

• projecting a first fringe pattern of a first spatial frequency along a first axis to irradiate the surface of the object;
• acquiring an image of the irradiated surface of the object;
• phase shifting the first fringe pattern at least two times and acquiring an image of the irradiated surface for each of the phase shifts;
• projecting a second fringe pattern of a second spatial frequency along a second axis to irradiate the surface of the object, wherein the first and second axes are spatially separate;
• acquiring an image of the irradiated surface of the object;
• phase shifting the second fringe pattern at least two times and acquiring an image of the irradiated surface for each of the phase shifts;
• and
• determining the positional information for the surface in response to the acquired images of the first and second fringe patterns.

A surface contour measurement system comprising:

• a multiple channel interferometer projector having a plurality of interferometer channels, each interferometer channel having a spatially separate optical axis and adapted to project a fringe pattern onto a surface of an object;
• a digital camera to acquire images of the fringe patterns projected on the surface of the object;
• and
• a processor in electrical communication with the multiple channel interferometer projector and the digital camera, the processor sending signals to the multiple channel interferometer projector to control the projection of fringe patterns of different spatial frequency and to modify the phase of the fringe patterns, the processor generating surface contour data in response to data received from the digital camera for each of the acquired images.