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Tutorial 12 - Stops and pupils

An optical systems collecting area is defined by the aperture stop - a surface, metal aperture or iris that limits the on axis bundle of rays / light. This aperture stop viewed in different spaces is called a pupil. In the object space it is the entrance pupil. In the image space it is the exit pupil.

The video also shows how to insert a telecentrating lens before the image to make it image side telecentric.... allowing for a more uniform illumination and little image height variation with defocus

Optics homework #12

The intent for the optics homework is to use a pencil and paper... or an excel sheet. One could solve these using Zemax, but there is great utility in doing the computations yourself.... and a lot of the optics problems will be repeated for the Zemax series!!!

1. An aperture stop is placed on an F/5, 100 mm focal length lens (objective). A fast 20 mm focal length lens is placed 120 mm away from the aperture stop (to the “right of the first lens). An eye is placed at the “end” or to the far right. Find the size and location of the exit pupil of the optical system.

Double Gauss is approximated with two perfect lenses surrounding the aperture stop: The set up from left to right is, 52 mm lens, 10 mm away is a 2mm diameter stop, 11 mm away from the stop is a 34 mm lens.
2. Find the location of the entrance pupil
3. Find the size of the entrance pupil
4. Find the location of the exit pupil
5. Find the size of the exit pupil
6. What is the pupil magnification?

7. A perfect lens is placed 12 mm after the last lens (focal length of 32 mm). Solve for this new perfect lens focal length to telecentrate the system (or collimate the chief rays).

Solutions can be found here.

Here is an animation showing a variable aperture stop

Scott Sparrold,
Jun 7, 2014, 5:48 AM