
Reduced coordinates
The reduced coordinates Hx,Hy,Px,Py
The reduced coordinates allow the specification of a ray in terms of field coordinates relative to the entire field of view, and in terms of pupil coordinates relative to the lens aperture. The reduced field coordinates (Hx,Hy) determine where the ray originates, and the reduced pupil coordinates (Px,Py) determine where the ray is heading. The scale is set by the maximum field radius of the fields specified on the sources window.
Example: Finite object distance
For a lens with object at finite distance, (Hx,Hy) determines the position on the object from which the ray is emitted, with the length scale set by the maximum field point radius specified on the sources window. the lens. If, for example, the field point furthest from the axis is (x,y)=(0,10mm), then the reduced field coordinate (Hx,Hy)=(0.2,0.1) means that ray starts at (x,y)=(2mm,1mm). The reduced pupil coordinates are relative to the lens aperture. If our example lens has a 3mm radius entrance pupil, then (Px,Py)=(0,0.5) corresponds to the ray hitting the entrance pupil at (x,y)=(0,1.5mm).
Example: infinite object distance
For a lens with object at infinite distance, (Hx,Hy) determines the angle of the ray entering the lens. If, for example, the lens has a 10 degree half field of view, then (Hx,Hy)=(0.2,0.1) means that ray is angled at 2 degrees in x and 1 degree in y. The reduced pupil coordinates are relative to the lens aperture. If our example lens has a 3mm radius entrance pupil, then (Px,Py)=(0,0.5) corresponds to the ray hitting the entrance pupil at (x,y)=(0,1.5mm).
