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Diffraction grating for optical scanning

  • US 5,091,798 A
  • Filed: 06/12/1991
  • Issued: 02/25/1992
  • Est. Priority Date: 03/31/1989
  • Status: Expired due to Fees
First Claim
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1. A diffraction grating system for optical scanning, comprising:

  • a plurality of diffraction gratings arranged on a peripheral edge portion of a disk scanner, each of said plurality of diffraction gratings further comprising;

    a plurality of grating rings disposed concentrically in a plane,said plurality of grating rings being provided at positions such that their radii r are selected so that a function φ

    (r) of r satisfies the following differential equation and initial conditions, ##EQU16## where λ

    is the wavelength of a scanning light beam, f is the focal length of each said diffraction grating, r is the radius from the center of each said diffraction grating, M is the distance from each said diffraction grating to a scanning surface expressed as a multiple of the focal length f, and moreover the relation
    
    
    space="preserve" listing-type="equation">φ

    (r)=n+φ

    (0)
    
    
    space="preserve" listing-type="equation">n=0, 1, 2, 3, . . .
    
    
    space="preserve" listing-type="equation">(n is a non-negative integer) is satisfied.

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