Multiple Channel Interferometric Surface Contour Measurement System

A method for determining a fringe number for a plurality of pixels for an offset channel in a multiple channel interferometric surface contour measurement system, the method comprising:

• determining a measured fringe number for the offset channel for each pixel;
• adjusting each measured fringe number by a collinear adjustment value for the respective pixel to obtain a collinear fringe number for the respective pixel, the collinear adjustment value being determined in part from a plurality of predetermined linear coefficients for the respective pixel;
• unwrapping the collinear fringe numbers to determine an integer portion of the fringe number for each pixel;
• and
• adjusting each unwrapped collinear fringe number by the collinear adjustment value of the respective pixel to obtain the fringe numbers.

A multiple channel interferometric surface contour measurement system comprising:

• a multiple channel interferometer projector for projecting fringe patterns onto a surface of an object, the multiple channel interferometer projector having an offset channel;
• a digital camera to acquire images of the projected fringe patterns on the surface of the object;
• and
• a processor in communication with the multiple channel interferometer projector and the digital camera, the processor (a) determining, for each of a plurality of pixels, a measured fringe number for the offset channel in response to images received from the digital camera;
• (b) adjusting the measured fringe numbers to generate a collinear fringe number for each pixel;
• (c) unwrapping the collinear fringe numbers;
• and (d) adjusting the unwrapped fringe numbers to obtain the fringe number for each pixel.

A method for determining a fringe number for a point on an object surface, the method comprising:

• (a) projecting a first fringe pattern onto the object surface, the first fringe pattern having a spatial frequency associated with a first source separation distance;
• (b) projecting a second fringe pattern onto the object surface, the second fringe pattern having a spatial frequency associated with a second source separation distance, wherein the first and second source separation distances are integer multiples m1 and m2, respectively, of a common base distance, the integer multiples m1 and m2 being relatively prime and greater than an integer fringe number for the point for the respective fringe pattern;
• and
• (c) determining the integer portions N(INT)1 and N(INT)2 of the fringe numbers for the first and second fringe patterns, respectively, in response to the integer multiples m1 and m2.