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US 4,340,283 AGranted
Phase shift multifocal zone plate
OwnerAllen L. Coheninventor
Life of this patent
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Abstract
A multifocal zone plate construction suitable for use in optical systems with multifocal requirements. It is designed as a phase shift multifocal zone plate to provide multiple focii with bright images. This is accomplished by adjusting the zone plate spacings such that some of the zone plate focii actually coincide with some of the multifocal Fresnel lens focii.
Claims9
A multiple focal power optical device comprising:
- body means having a plurality of alternating odd and even, annular, concentric zones, bounded on the outside by 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 the square root of n;
- and wherein the absolute value of r.sub.1 is set equal to .sqroot..lambda.d, with .lambda. equal to the wavelength under consideration, and d is substantially equal to the reciprocal of the absolute value of the difference between the first and second focal powers.
2 more elements
Dependencies are inferred from the claim text.