×

Projection lens

  • US 6,473,244 B1
  • Filed: 10/27/2000
  • Issued: 10/29/2002
  • Est. Priority Date: 10/29/1999
  • Status: Expired due to Fees
First Claim
Patent Images

1. A projection lens comprising:

  • a first lens group, a diaphragm, and a second lens group, which are disposed in that order from a long conjugate side to a short conjugate side;

    wherein the first lens group comprises an aspherical lens disposed at the long conjugate side, and at least one positive lens, so that the first lens group as a whole has a positive refractive power, wherein the second lens group comprises at least one set of combined lenses and an aspherical lens, so that the second lens group as a whole has a positive refractive power, wherein a focusing operation is carried out by moving a gap between predetermined lenses in the first lens group, and conditional expressions (1) and (2) are satisfied;

    1.87<

    BF/F
    Conditional





    expression





    (1)
    0.22<

    HF2/F2<

    0.57
    Conditional





    expression





    (2)
    embedded image

    where F denotes a focal length of the projection lens, BF denotes a distance in air from a last lens surface of the second lens group to a small conjugate point when a projection magnification is a predetermined value, F2 denotes a focal length of the second lens group, and HF2 denotes a location of a front principal point of the second lens group.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×