An overlapping technique to measure the parallelism of surface elements in a large area based on comparison goniometer

Comparison goniometer, precision autocollimator, can be used to measure parallelism or angular error. If the size of the work piece to be measured is larger than the aperture of the objective lens, the measurement can not be carried through, because a part of work piece can't be observed. A new technique, called overlapping measurement technique, is proposed. The work piece will be moved, and two adjacent measurements must have an intercross. The relationship between the readings of the autocollimator and the angular error has been deduced. A program written in VC++6.0 will be used to process the measurement data.