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Modified Zone Plates

IP.com Disclosure Number: IPCOM000094080D
Original Publication Date: 1966-May-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Rottmann, HR: AUTHOR

Abstract

Zone plates comprise alternate transparent and opaque annuli of equal area and ever increasing radii. A zone plate has the properties of a lens and focuses radiation. The incident light from a distant axial source partially passes through the transparent rings and partially scatters at the edges. Any image is generated by rays scattered at the edges of the annuli. The clear zones transmit a substantial amount of light which contributes only to the background illumination, thus reducing the contrast. A number of modifications enhance the contrast through reduction of the background light. Each condition is described.

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Modified Zone Plates

Zone plates comprise alternate transparent and opaque annuli of equal area and ever increasing radii. A zone plate has the properties of a lens and focuses radiation. The incident light from a distant axial source partially passes through the transparent rings and partially scatters at the edges. Any image is generated by rays scattered at the edges of the annuli. The clear zones transmit a substantial amount of light which contributes only to the background illumination, thus reducing the contrast. A number of modifications enhance the contrast through reduction of the background light. Each condition is described.

One arrangement, as in A, involves the placement of opaque rings 21 in some or all of the transparent or clear zones 22. The width of the additional opaque rings are of the order of 1/2 to 9/10 of the width of the original clear zones. The additional opaque rings diminish somewhat the background light, thus improving the contrast.

Another arrangement involves the radii formula for determining the diameter of each ring. The formula is as follows: R(N)/2/ =2F lambda(N+ epsilon+ lambda/2/(N+ epsilon)/2/ where
N =1,2,3.....,
lambda = the wave length of the light,
F = focal length and epsilon = a number of values, such as (a) = -1/2 N gives the ordinary zone plate

(b) = 0 is a new the of a zone plate shown in B

(c) = 0, 1/4, and 3/4 is another new type

of a zone plate shown in C.

Substituting values for epsilon provides different zone pla...