Aberration reduction in acoustical holography.

This paper examines the aberrations in holographic systems characterized by a ratio of reconstruction wavelength to recording wavelength of the order of 10(-3). The study is restricted to those systems using a plane reference beam and with the hologram scaled by a factor greater than the wavelength ratio. An inline hologram geometry is examined where the reconstruction beam is placed such that the image of a selected object point on the optical axis has zero aberrations. The aberrations for object points off axis then are calculated. For off-axis holograms, a technique for balancing spherical aberration and astigmatism has been modified to apply to scaled holograms. Some general rules for the optimum recording geometry are developed. The aberrations for the balanced off-axis system are calculated and compared to those of the in-line system.