Optical system for monitor cameras to be mounted on vehicles

  • US 5,648,835 A
  • Filed: 04/07/1995
  • Issued: 07/15/1997
  • Est. Priority Date: 09/22/1992
  • Status: Expired due to Term
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First Claim
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1. A photographic lens system comprising, in order from the object side:

  • a first lens component having a negative refractive power and a second lens component having a positive refractive power;

    wherein said first lens component consists only of a single negative lens element, and said second lens component consists of a negative meniscus lens element and a biconvex lens element disposed in this order or the reverse order, and wherein said photographic lens system satisfies the following conditions (2), (3) and (4);

    
    
    space="preserve" listing-type="equation">ν

    .sub.1 >

    40 (2)
    
    
    space="preserve" listing-type="equation">ν

    .sub.2p -ν

    .sub.2n >

    10 (3)
    
    
    space="preserve" listing-type="equation">(n.sub.2n -n.sub.2p)×

    {2/(|r.sub.2n +|r.sub.2p |)}×

    f>

    0.48 (4)wherein the reference symbol ν

    1 represents an Abbe'"'"'s number of the negative lens element of said first lens component, the reference symbols ν

    2p and ν

    2n designate Abbe'"'"'s numbers of the positive lens element and the negative lens element of said second lens component respectively, the reference symbols n2p and n2n represent refractive indices of the positive lens element and the negative lens element, respectively, of the second lens component, the reference symbols r1p and [r2n denote radii of curvature on surfaces of the positive lens element and the negative lens element respectively of said second lens component which are opposed to each other (a radius of curvature r1p =[r2n on a cemented surface in a case where said second lens component is configured as a cemented doublet), and the reference symbol f represents a focal length of said photographic lens system as a whole.

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