Depth-of-focus reduction for digital in-line holography of particle fields.
Poor axial precision caused, in part, by large depth of focus (tau) has been a vexing problem in extraction of particle position from digital in-line holograms. A simple method is proposed to combat this depth-of-focus difficulty. The method is based on decoupling of size and position information. With d, Delta, and lambda being particle diameter, CCD pixel size, and the wavelength, respectively, our main theoretical result is the reduction of tau from tau - d2/lambda to tau - Delta2/lambda for particles of known size. This result is confirmed in laboratory experiments with holograms of calibrated glass spheres.
Yang
Weidong
W
Department of Physics, Michigan Technological University, 1400 Townsend Drive, Houghton, Michigan 49931, USA. weyang@mtu.edu
Kostinski
Alexander B
AB
Shaw
Raymond A
RA