DISTORTIONLESS INTERFEROGRAM RECORDING BY USE OF HOLOGRAPHIC FIELD LENSES FOR FLUID VELOCIMETRY

Two optical systems based on holographic field lenses are presented. T hey have been specifically designed for the CCD camera acquisition of the interferograms obtained from a fluid plane, when one uses holograp hic interferometry to measure fluid velocities. The use of these syste ms allows for easy recording of interferograms, all having the same si ze and position on the CCD, independent of the fluid-plane observation direction. The holographic lenses act as directional field lenses; th ey change the divergent beam that reaches the lens into a convergent b eam that focuses on the camera aperture. These distortionless interfer ogram recording systems have been demonstrated in a Rayleigh-Benard co nvective flow. (C) 1997 Optical Society of America.