Multifocal diffractive lens

A multifocal diffractive lens is a diffractive optical element (DOE) that allows a single incident beam to be focused simultaneously at several positions along the propagation axis.

Example of multifocal peak intensity distribution along optical axis.(Courtesy of Holo/Or)

Intensity distribution of multifocal lens 5 foci in Z-X plane

Principle of operation

An incident laser beam deflected by grooved diffraction pattern into axial diffraction orders along optical axis. The foci positions appear around far field position. In a case of using additional focusing lens, foci from mutifocal lens will appear in certain distance from focal distance of the lens.

Theory

The multifocal spots location is a function of refractive focal length f_Refractive and predetermined diffractive focal length f_Diffractive The focal spot at the "zero" order refers to the refractive focal length of the lens being used.

The distance between the focal spots can be described by the equation

{\frac {1}{f_{m}}}={\frac {1}{f_{\mathrm {Refractive} }}}+{\frac {m}{f_{\mathrm {Diffractive} }}},\ \mathrm {for} \ m=\pm 1,\pm 2,\pm 3...

where f_m is the focal Length for the mth diffractive order,

f_Refractive is the focal length of the refractive lens, and

f_Diffractive is the focal length of the diffractive lens.

Applications

External links

This article is issued from Wikipedia - version of the 9/6/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.