Field Test Unit for Windscreen Optical Evaluation

摘要

The invention is directed to an optical apparatus used to analyze the deleterious optical effects of a windscreen or other transparent body when it is inserted into the path of observation. Optical distortion is measured by noting its effect on a precision pattern projected through the transparent body. The multiple imaging phenomenon appears in the same projected pattern and is generally characterized by asymmetrically distributed images of the fundamental pattern. By polarizing an unpatterned beam of light, and projecting it through the same transparent body, the optical sensor in the apparatus records the birefringence characteristics of the body. To analyze distortion and multiple imaging a beam of light, with the pattern of interest superimposed, is projected through the transparent body to a focus on a retro-reflective screen. A segment of the returning beam is redirected after it again passes through the transparent body, with the new direction being substantially aligned to the axis of an optical sensor. Pattern images and variations in the pattern shape correspond directly to the characteristics of th transparent body. Birefringence is analyzed by polarizing the light beam prior to its first pass through the transparent body. The retro-reflected beam reaching the optical sensor contains a spatial distribution of color corresponding to the birefringence characteristics of the transparent body.