Video Applications to Moiré Metrology

Abstract

Video technology is applied to the problem of moiré metrology. In the past, moiré metrology seemed a promising yet limited method in the measurement and comparison of surface shape. The use of video technology has widened the area of application of moiré metrology by reducing the complexity of the optical set up and providing real time information on surface shape and deformation. A continuously variable grating projector and analog video circuitry are used to generate real time additive (bright line) and transmissive (dark line) moiré patterns. These patterns are used to compare a test object against a “perfect” reference object. This is done in both real time and through the use of computer image processing. Depth resolutions on the order of 0.3 mm are obtained on a cone 25.4 mm high and 50.8 mm wide. The projection system allows easy expansion to large objects. Because of the use of video technology moiré metrology can now be more readily applied to robotic vision and factory assembly line quality control over a wide range of scales.