What is a TIR optic?
By Luana | 01 March 2023 | 1 Comments

What is a TIR optic?

A TIR (total internal reflection) optic is a compound lens that combines the best of both a reflector and a lens to maximize the beam shaping capabilities. The compound lens consists of a refractive lens inside a reflector. The refractive lens collects and manages the light from an LED package. The use of refractive and reflective elements allows for more optical aberrations to be corrected than is possible with a single element. It's the reflector that processes and shapes the beam. The mechanism behind this has to do with Snell’s law and some important optical principles.
TIR optics are the optimum solution to produce smooth circular beams with small FWHM angular widths, and they are generally injection-molded from polymers such as PMMA (polymethyl methacrylate) acrylic and polycarbonate.
Light is refracted, or turned from its original path, at any place where it reaches an interface between two materials with different refractive indices. If the first material has a higher index of refraction than the second, Snell’s law tells us that the angle of refraction will be more than ninety degrees. Where the angle of incidence is greater than a critical angle, the light will be reflected into the material. We call this total internal reflection. The beam angle depends on the curvature of the TIR surface for your specific lens.
Total internal reflection captures all light radiation leaving a source, and is therefore the most efficient method to reflect light. Providing the ultimate control of light distribution, this type of collimator is ideal for when you need a strong, targeted beam. While a simple reflector can only affect reflected light and not direct light beams, a TIR lens manages both. TIR optics placed over a LED chip will capture and focus all the light.

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