A machine-vision lens has a focal length of 25 mm and is set to
PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Geometrical optics and imaging · Geometrical optics and imaging
What an Instrument Can See, Ch Pupils: the aperture of a linear system
Problem
A machine-vision lens has a focal length of 25 mm and is set to f/2. At the corner of its rectangular sensor the chief ray leaves the exit pupil at a field angle of 24∘ from the axis. The measured illumination at that corner, relative to the centre of the frame, is 0.55.
((a)) Estimate the fraction of the corner illumination accounted for by the cosine-fourth falloff alone.
((b)) Hence estimate the vignetting factor (the unclipped fraction of pupil area) at that field angle.