A through-optical bench is the optical equivalent of a folded-optical
system. Folded optics is generally found in cannon launched guided
projectiles and always includes a mirror mounted on a gimbal. Inside the
projectile the optical image is hidden behind the mirror and is not
easily accessible by measurement instrument. In the through-optical bench
the image is repositioned to where it is easily viewed; hence enabling a
much finer process to improve manufacturing accuracy and throughput. The
through-optical bench uses a collimated beam of light which passes
through the seeker nose optical cluster, then through a mask which mimics
the mirror, then through an identical optical cluster which substitutes
for the reflection, and finally onto a screen to form a focused image
directly viewable by a microscope. The clusters and mask simultaneously
step through various yaw angles made possible by a reversing linkage that
moves them as mirror images. A micrometer dial simulates the focusing
shim for the particular seeker nose cluster.