Stray Light Analysis Using TracePro Data Sheet

Stray light occurs in all optical and illumination systems. Stray light includes ghost images in lens systems, single and multiple scatter from optical and mechanical surfaces, as well as narcissus and self-emission in infrared systems. Ghost images occur when light rays reflect from lens surfaces and reach the image plane in an unwanted location. At any surface boundary, reflection, refraction, absorption, reflective scatter, and transmissive scatter all may occur, each contributing to stray light.

Stray light resulting from each phenomenon can be accurately predicted and analyzed using TracePro. TracePro’s advanced features provide insight into determining problematic stray light paths. You can visualize and quantify any individual stray light path, and use Boolean filters to group similar paths together. Rays from the paths can be displayed, as well as 2D and 3D irradiance maps resulting from the selected paths. The Flux Report details how much light is incident and absorbed on each surface and object. TracePro’s strong interoperability enables import of lens design files, and import and export of standard CAD file formats.

With TracePro’s ray splitting feature, a parent ray can be split into child rays (reflection, refraction, transmissive and reflective scatter, and absorption). Ray splitting enables efficient sampling of rays reflected from lens surfaces and is essential for ghost analysis.

TracePro’s Monte Carlo ray tracing engine provides a powerful, general-purpose tool for simulation of optical phenomena as probability distributions, and uses pseudo-random numbers to sample these distributions. Variance reduction techniques are employed to improve simulation efficiency by orders of magnitude over crude Monte Carlo.

Importance sampling is a variance reduction method used to increase sampling in low-probability scattered paths that would otherwise be under-sampled. A scatter distribution function is used to determine probability density and apportion a fraction of the scattered ray flux into a desired direction. Importance sampling can speed convergence of the simulation by orders of magnitude.