A method for measuring the focal length of lenses using the Talbot effect and the moiré technique is described. The test lens is placed in front of a set of two gratings. The first grating illuminated by the light passing through the test lens produces the magnified Talbot image. The moiré fringe is generated by superimposing this Talbot image on the second grating. The tilt angle of the moiré fringe is a measure of the focal length of the lens. In the experiments, the focal lengths of positive, negative, and power-distributed lenses are measured.
© 1985 Optical Society of America
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