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Diffraction bifocal with adjusted chromaticity

  • US 5,117,306 A
  • Filed: 07/17/1990
  • Issued: 05/26/1992
  • Est. Priority Date: 07/17/1990
  • Status: Expired due to Fees
First Claim
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1. An optical lens comprising;

  • (a) a first profiled surface or interface, for diffracting light to two adjacent non negative focal orders m and (m+1), m=0, 1, 2,. . . , comprising a plurality of annular concentric zones spaced according to the formula
    
    
    space="preserve" listing-type="equation">r.sub.k =√

    (k dλ

    ) k=1, 2, 3, where λ

    is the design wavelength, d is the primary focal length of the surface or interface. k is a zone, and rk is the zone radius, and(b) a second profiled surface or interface, for diffracting light to a negative focal order -M, M=1, 2, 3, . . . , comprising a plurality of annular concentric zones spaced according to the formula
    
    
    space="preserve" listing-type="equation">R.sub.k =√

    (kDλ

    ) k=1, 2, 3, where D is the primary focal length of the surface or interface, and Rk is the zone radius,said surfaces aligned such that their optical axes are coincident, and such that (m+1)/d >

    M/D >

    m/d thereby providing for positive chromatic aberration to be associated with a first focal point and negative chromatic aberration to be associated with a second focal point.

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