Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Images of 1951 USAF resolution target, from a single image or from a set of recombined images. Top left: single image. Top right: square pattern. Bottom left: quadrilateral pattern. Bottom right: random pattern. Notice that all elements of group 7 are resolvable in the top right image.
