Multifocal zone plate
OwnerAllen L. Coheninventor
Life of this patent
Estimating the term…
Abstract
A multifocal Fresnel lens construction suitable for use in optical systems with multifocal requirements. It is designed as a multifocal zone plate to allow an annular ring construction that isn't width limited by diffraction aberrations. This is accomplished by modifying the phase separating annular rings of a zone plate, with curved or inclined optical facets of varying refractive indices, which can then function as Fresnel rings corresponding to the different focal powers desired.
Claims15
A multiple focal power optical device comprising:
- body means having a plurality of alternating odd and even, annular, concentric zones, bounded on the outside of radii r.sub.n, with n=1,3,5, . . . , for the odd zones and n=2,4,6, . . . , for the even zones;
- first focal power means within at least some of the odd zones for directing incident parallel light to a first focal point;
- second focal power means within at least some of the even zones for directing incident parallel light to a second focal point different from said first focal point;
- wherein the radii r.sub.n of said odd and even zones are substantially proportional to square root of n.
A multiple power optical device, using the principle of interleaving annular Fresnel zones corresponding to different optical powers, wherein the radius r.sub.n, bounding the nth Fresnel zone, is set to substantially approximate the formula r.sub.n .perspectiveto..sqroot.nK, where K is an arbitrary but constant length and n=1,2,3, . . . , and wherein for each specific power, all of the corresponding Fresnel zones are bounded on the outside by radii r.sub.n, with n being either odd for all of the zones or even for all of the zones.
Dependencies are inferred from the claim text.