LAKSYMO:
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The target's bar graphic is adapted from a standardized U.S. Air Force chart for testing camera resolution. Numbers on it refer to how many of the black-white cycles fit into one millimeter. For example, in the largest set of bars, labeled 1.0, each black bar is one-half millimeter wide and each white space between bars is another one-half millimeter. One millimeter is about 0.04 inch. Applied Image Inc., Rochester, N.Y., made the portion of the MAHLI calibration target with this chart and other graphics on opal glass. One of the graphics, just above the left edge of the penny, is a tiny cartoon figure called "Joe the Martian."
The penny is from 1909, the first year Lincoln pennies were minted and the centennial of Abraham Lincoln's birth. Including it on the calibration target is a nod to geologists' tradition of placing a coin as a size reference in close-up photographs of rocks. It gives the public a familiar object for perceiving size easily.