Replacement of quarter-wave plates by photographic double exposure for controlled density evaluation
Abstract
The paper describes a technique of double exposure with equal exposure times in a plane polariscope and with rotation of the polaroids through 45 deg between exposures for the evaluation of isochromatic fringe orders by boundary or equidensity line techniques. This technique has the following advantages: (1) quarter-wave plates are not required and errors associated with their use are avoided, (2) monochromatic light is not needed and white light may be used with blue-sensitive or orthochromatic film, (3) the same polariscope elements serve for the evaluation of both isoclinics and isochromatics, (4) the fractional orders of the photographic lines can be changed not only by using different exposure times, but also by using different coupling angles between the transmission axes of the polaroids, and (5) a simple and cheap bench without ancillaries can be used for the evaluation of fractional fringe orders.
- Publication:
-
Journal of Strain Analysis and Engineering Design
- Pub Date:
- July 1977
- Bibcode:
- 1977JStA...12..185M
- Keywords:
-
- Density Measurement;
- Diffraction Patterns;
- Imaging Techniques;
- Photoelastic Analysis;
- Exposure;
- Monochromatic Radiation;
- Photographic Film;
- Photographic Plates;
- Instrumentation and Photography