1951 USAF Resolution Test Chart is a resolution test pattern conforms to MIL-S-150A standard, set by US Air Force in 1951. It is widely accepted to test the resolving power of optical imaging systems such as microscopes and cameras. The pattern consists of groups of three bars with dimensions from big to small. The largest bar the imager cannot discern is the limitation of its resolving power.

Pattern format

The common MIL-S-150A format consists of six "groups" in three layers of patterns. The largest groups, forming the first layer, are located on the outer sides. The smaller layers repeat the same pattern but are progressively smaller toward the center. Each group consists of six elements, numbered from 1 to 6. Within the same layer, the odd-numbered groups appear contiguously from 1 through 6 from the upper right corner. The first element of the even-numbered groups is at the lower right of the layer, with the remaining 2 through 6, at the left. The scales and dimensions of the can be found at the external links.

Problems with the 1951 USAF Chart

The 1951 chart is not well suited for modern lens analysis. The fragmented arrangement makes it difficult for software to automatically determine the maximum resolution and it does not scale well for testing the corners of lenses where abberations are more likely to appear.

External links

• efg's Tech Note: USAF 1951 and Microcopy Resolution Test Charts.

• Koren 2003: Norman Koren's updated resolution chart better suited for computer analysis

Optics