Geometric Change
Physical changes in the geometry or refractive properties of an optical system alter the length and direction of light travel through the medium. An optical path deformation results from mechanical strain or thermal gradients that perturb the intended alignment of mirrors and lenses. The phenomenon is a primary source of error in high precision interferometers and laser based sensing equipment.
Wavefront Distortion
Phase shifts occur when different parts of a light beam travel through varying thicknesses of a material. The optical path deformation induces shifts that can degrade the interference pattern used to detect motion or distance. Precise measurement of these changes requires high resolution cameras or photodetector arrays that capture the fringe patterns at the output.
If the deformation is non-uniform, it introduces aberrations that cannot be easily corrected by simple focal adjustments.
Thermal Expansion
Expansion coefficients of the substrate determine how much the path will change with fluctuating temperatures. Selecting materials with low expansion, such as Zerodur or fused silica, minimizes the susceptibility of the system to optical path deformation.
Active Compensation
Adaptive optics use deformable mirrors to counteract real-time changes in the environment. Wavefront sensors measure the error and provide feedback to the actuators that reshape the mirror surface.
