device and method for non-destructive testing of objects using optical metrology

摘要

Apparatus and methods for inspecting or testing a sample using shearography techniques make use of a laser shearing interferometer including: means for scanning a line of coherent radiation over a sample, means for generating two laterally displaced images of the sample, and means for stepping or ramping the phase of one of the two images. A video camera provides output signals from which an image processor extracts the frame rate of the camera in real time. Signals substantially in phase with the frame rate of the camera are fed to the stepping or ramping means and to the line scanning means, and decoding means perform phase unwrapping or extraction. The interferometer and sample are contained within a vacuum chamber with pressure control.