A modification of schlieren optics was explored as a technique for industrial gas-leak detection. A high-contrast pattern on thin reflecting material was imaged with a zoom lens onto a negative of the same pattern as a method of eliminating the ordinary rays. The geometry of the industrial setting determines the useful spatial frequency of the pattern.
© 1996 Optical Society of America
R. E. Peale and P. L. Summers, "Zebra schlieren optics for leak detection," Appl. Opt. 35, 4518-4521 (1996)