Focal-length measurement by multiple-beam shearing interferometry.
The application of multiple-beam shearing interferometry to lens focal-length measurement is described. A coated shearing plate interferometer was used in transmission to produce sharp multiple-beam fringes that rotate as the collimation of the incoming wave front from the lens under test changes. The test lens was used to collimate light from a point source that was translated longitudinally, and the focal length was determined from the rate of rotation of the fringes as the source moved. This method is simple, accurate, and lends itself to automatic determination of focal length.
Matsuda
K
K
Department of Physical Optics, School of Physics, University of Sydney, New South Wales 2006, Australia. kiyo@physics.usyd.edu.au
Barnes
T H
TH
Oreb
B F
BF
Sheppard
C J
CJ