Radiometric errors due to focusing collecting optics at varying object distances
Abstract
Because the efficiency of radiometers and photometers using collecting optics varies with distance for near objects, causing significant errors, variation in effective collecting area as well as in solid angle with distance must be considered. Errors for a thin lens and a Cassegrainian system are compared, and it is found that (1) moving the secondary for focusing greatly reduces this variation and (2) the ratio of primary to secondary focal length also plays an important role. The proper choice of this ratio can minimize the variation in the field of view, improving the depth of focus.
- Publication:
-
Applied Optics
- Pub Date:
- July 1981
- DOI:
- 10.1364/AO.20.002590
- Bibcode:
- 1981ApOpt..20.2590H
- Keywords:
-
- Cassegrain Optics;
- Error Analysis;
- Focusing;
- Optical Equipment;
- Radiometers;
- Calibrating;
- Field Of View;
- Foci;
- Instrumentation and Photography;
- RADIOMETRY