ABSTRACT
Stress induced birefringence is a widespread and often unavoidable problem in optical systems which frequently occurs in injection molded plastic optics due to molding processes, and in glass lenses as a result of poor opto-mechanical mounting techniques. Also, optical materials can undergo strain at the molecular level due to various environmental conditions, such as external pressures, vibration, or temperature change. This stress induced retardance is undesirable, changing the wavefront aberration and polarization aberration, and affecting the point spread function of optical systems. It is important to ray trace the effects of stress birefringence to assess its impact. The stress birefringence magnitude and fast axis orientation across the pupil give insight into the stress location, orientation, and magnitude. In most systems, a quarter of a wave of birefringence can cause noticeable image degradation. One quick way to observe birefringence is to use the polariscope which measure the integrated retardance along the ray path in transparent samples. Polariscope images of various plastic and glass samples in different polariscope configurations are shown in this chapter to reveal the magnitude and orientation of induced birefringent. The complex stress distributions are modeled as a varying anisotropic material with spatially varying dielectric tensor. The ray tracing algorithms must simulate a gradient index of birefringence. Further, the optical system can be ray traced with different levels of stress birefringence to tolerance the maximum amount of stress which is acceptable based on the system’s image quality specifications.
