Abstract

The problem of determining fluid-flow velocities by observing, from a position outside a flow field, the optical radiation coming from or through the field is considered.

The space filtering provided by a focusing optical system is examined, and it is shown that this space filtering coupled with time filtering of the image-space intensity makes the radiation coming from a small region of the flow distinguishable from the radiation coming from the remainder of the flow. Therefore, local velocities can be determined from measurements of the motion of image-space radiation. Two methods of determining the image-space motion are treated, both of which are related to the correlation of image-space irradiance at different points in space and time.

© 1967 Optical Society of America

Detectability of Coherent Optical Signals in a Heterodyne Receiver

Carl W. Helstrom
J. Opt. Soc. Am. 57(3) 353-361 (1967)

Optical Systems, Singularity Functions, Complex Hankel Transforms

A. Papoulis
J. Opt. Soc. Am. 57(2) 207-213 (1967)

Optical Transfer of the Three-Dimensional Object*†

B. Roy Frieden
J. Opt. Soc. Am. 57(1) 56-66 (1967)

Band-Unlimited Reconstruction of Optical Objects and Spectra*

B. Roy Frieden
J. Opt. Soc. Am. 57(8) 1013-1019 (1967)

Image Restoration by the Method of Least Squares

Carl W. Helstrom
J. Opt. Soc. Am. 57(3) 297-303 (1967)