A less expensive, abbreviated version omits the two tiniest groups at the center of the pattern (groups number 8 and 9), since the lithography at that scale is costly, and the group elements represent resolution beyond the design of many imaging applications. Slides are available as photographic positive or negative prints to best fit the illumination technique used in various testing methods. The slide is printed in metallic chromium by photolithography with the standard pattern, photographically reduced from a large master plot. The series of elements spans the range of resolution of the unaided eye, down to the diffraction limits of conventional light microscopy.Ĭommercially produced devices typically consist of a transparent square glass slide, 2 inches or 50 mm in dimension.
These 54 elements are provided in a standardized series of logarithmic steps in the spatial frequency range from 0.250 to 912.3 line pairs per millimeter (lp/mm). Each element consists of three bars which form a minimal Ronchi ruling. The full standard pattern consists of 9 groups, with each group consisting of 6 elements thus there are 54 target elements provided in the full series.
It is widely used in optical engineering laboratory work to analyze and validate imaging systems such as microscopes, cameras and image scanners. The design provides numerous small target shapes exhibiting a stepped assortment of precise spatial frequency specimens. A 1951 USAF resolution test chart is a microscopic optical resolution test device originally defined by the U.S.
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