chapter  3
56 Pages

Stray Light Control for Molded Optics

WithEric Fest

Analysis ..............................................................................84 3.4 Basic Stray Light Mechanisms ...................................................................86

3.4.1 Specular Mechanisms .....................................................................86 3.4.1.1 Direct Illumination of the Detector ................................86 3.4.1.2 Specular Mirror Režection .............................................. 87 3.4.1.3 Ghost Režections ...............................................................88 3.4.1.4 Specular Režection from or Transmission

through Mechanical Surfaces ..........................................90 3.4.2 Scattering Mechanisms ................................................................... 91

3.4.2.1 BSDF and RMS Surface Roughness Measurements ................................................................... 91

3.4.2.2 Scattering from Mechanical Surfaces ............................. 92 3.4.2.3 Scattering from Optical Surface Roughness ................. 95

Stray light is generally de„ned as unwanted light that reaches the focal plane of an optical system. A classic stray light problem occurs when photographing a scene in which the sun is just outside the „eld of view (FOV). Light from the sun strikes the camera and, by mechanisms such as ghost režections, surface roughness scatter, and aperture diffraction, reaches the focal plane and creates bright spots that can obscure the subject. An example of this phenomenon is shown in Figure 3.1.