Optical Board - Depth Of Field

Purpose

To illustrate the idea of depth of field of a (camera) lens, and to locate the near and far points.

Equipment

Optical board with three convex lenses.

Setup Time

5 min.

Images

l6-11

Description

The beams passing through lenses 1 and 2 are focussed to produce an object for lens 3, the "camera" lens,which is imaged on a distant screen at the right as a straight line. Adjust the screen position so that the image is as sharp as possible, and mark the object point on the optical board with black tape. By moving lens 2, the position of the object is changed, eventually causing the image to become blurred. Mark the near and far points on the board for an acceptably clear image line. The result as obtained here is somewhat arbitrary, but in fact there is a mathematical definition for what co

References

Alex J. Dragt, Lie Albegraic Theory of Geometrical Optics and Optical Aberrations, Journal of the Optical Society of America 72,372-379.