Asperic Surface Test Fixture.
DEPARTMENT OF THE NAVY WASHINGTON DC
Pagination or Media Count:
An optic surface apparatus capable handling aspheric surfaces uses direct measurement of the blur circle of the image created by the test surface. Direct measurement of the blur circle is obtained by providing a collimated light beam which includes the test surface in its optical path to an ultimate focal point. The focal point is occupied by an apertured screen with apertures of varying diameter. A light detector is placed behind the apertured screen to measure the intensity of light as a function of aperture size. The apertured screen and detector are mounted on a three-axis translator. For apertures equal to or greater than the effective diameter of the blur circle, 100 of the light reaches the light detector. A folding mirror is used in the optical path to permit the device to be physically compact. Different wavelengths of test energy may be employed provided that appropriate adjustments are made to the corrector lens and detector choice.