slide
projector and projection lens or document camera
DESCRIPTION
The apparatus consists of a
long-focal-length
convex lens pressed against a flat glass plate. The reflections
off
the two inner air-glass interfaces produce a circular interference
pattern.
NOTES
There are several ways to show
the
pattern:
View with the document
camera, with the apparatus near the lens (shown at right).
Project light of the slide
projector through the apparatus (above).
Reflect light from slide
projector off the apparatus, and through a projection lens. (below)