Distorted Image - Pincushion And Barrel

Purpose

The fast and simple way to show pincushion and barrel distortion.

Equipment

Bright point source with condenser lens, 10 cm focal length plano-convex lens, fine screen, large diameter 23 cm focal length convex lens in light baffle.◙

Setup Time

5 min.

Images

l6-41

Description

The optical system in the photograph includes the following: bright point source with condenser lens, 10cm foca length plano-convex lens with flat side toward light source, fine wire mesh 10 cm from the lens, and 23 cm convex lens to focus image of mesh on distant screen. Move the lens away from the mesh to see pincushion distortion, and toward the lens to see barrel◙distortion. This demonstration also shows "curvature of field," because the position for the 23 cm lens to focus central and peripheral rays is different. ◙View from within a few feet to see chromatic aberration.

References

Lecture Demonstrations References: Hecht-Zajac, Optics, 184-186, (1973); Pohl, Optik and Und Atomphysik, 40-41, (1967); Sears, Optics 125-127, (1958); Francon, Experiences de Physique, 139-140, (1958).