Speckle reduction by simulation of partially coherent object illumination in holography.
This method consists of two steps. The first is to illuminate the object with a plurality of point sources each of which is mutually coherent with the reference source. All the points are contained within the pupil of the optical apparatus. The second step takes place after the hologram has been made in the manner mentioned. During the reconstruction, a mask is placed in the plane, conjugate to the plane containing the plurality of object-illuminating sources. An aperture in this mask is then moved to take positions to transmit only the light from one of the plurality of points at a time and to block the light from all the other points. The images thus detected are additive in intensity, simulating the plurality of illuminating point sources to be mutually incoherent.
van Ligten
R F
RF