Optical Coherence Measurement Fundamentals for Deep Tooling Cavities
Optical coherence measurement uses broad-bandwidth infrared interference to capture deep cavity topographies without mechanical probe contact or lens clipping.
Fresnel Reflection
Meaning
Physical phenomenon where a portion of light is sent back at the interface between two materials with different refractive indices. In the production of clear optical lenses or light guides, fresnel reflection accounts for the loss of transmission efficiency at the air to polymer boundary. This effect determines the clarity and brightness of the finished transparent part.
Surface Treatment
Losses at the surface reduce the total luminous flux passing through a prismatic lens. Minimizing fresnel reflection often requires the application of anti reflective coatings or specific surface textures during the molding process. These micro structures change how light interacts with the material transition.
Mold Polish
Surface finish on the tool steel directly dictates the optical performance of the molded plastic. High levels of fresnel reflection occur when the tool lacks a mirror finish, leading to diffused scattering that clouds the image. Moulders use diamond polishing to achieve the roughness grades necessary for high precision optics.
A rough surface breaks the uniform wavefront. This scattering adds to the internal losses within the polymer matrix.
Material Selection
Refractive index varies between acrylic and polycarbonate resins. Selection of the grade influences the intensity of fresnel reflection at the first surface. Choosing a material with a lower index reduces the inherent backscatter.