F-Theta | OptoWiki Knowledge Base

F-Theta lenses are a class of Fisheye lenses

F-Theta lenses are also called “equidistant“, “linear scaled“, “äquidistant” or “angular”

F-Theta lenses use an image mapping function of type
$r = f \theta$

Non distortion 180° F-Theta lenses have an image circle or $\pi * FocalLength$ mm

A non distortion F-Theta lens of 1.37mm focal length has an image circle of $d = \pi 1.37$ mm = $4.30$ mm
Therefor a f=3.17mm F-Theata lens with an image diameter for 180° of 4.15mm has a distortion of (4.15/4.3)-1 = 0.965-1 = -3.5%

maintains angular distances

see
Fisheye Types