Laser speckle tomography measurement of the refractive index distribution of the acetone vapor

Abstract EN

Laser speckle photography is a well-established optical method which can be app- lied to measure the refractive index of phase object.

In this technique, laser light ray is used to illuminate aground glass (diffuser).

After its transmission it, scatters randomly.

Interference of these scattered rays are imaged on a high resolution photographic plate, called after developing specklegram.

Two exposures were recorded on the same photo- graphic plate, one without acetone vapor and the second with it .

The doubly exposed specklegram was developed.

The point-bypoint analysis was used with illuminating a narrow laser beam to obtain fringes similar to Young's fringes produced by multi-pinhole pairs.

The distribution of the refractive index at different cross sections is measured from the data available in the doubly-exposed specklegrams