Patent ID: 6853494

Claim:
A zoom system for a microscope, the zoom system comprising a first lens group having lenses ( 11 ) and ( 12 ), a second lens group having lenses ( 13 ) and ( 14 ), a third lens group having lenses ( 15 ) and ( 16 ), and a fourth lens group having lenses ( 17 ) and ( 18 ) arranged in sequence and aligned along an optical axis, the first and fourth lens groups being mirror images of one another, the second and third lens groups being mirror images of one another, a first air gap between the first and second lens groups, a second air gap between the second and third lens groups, and a third air gap between the third and fourth lens groups, each of the second and third lens groups being movable along the optical axis thereby enabling variation of the first, second, and third air gaps, wherein the lenses ( 11 through 18 ) and air gaps have the following geometric and optical properties: Thickness or air gap d 1 (mm) [air gaps Boundary given at first limit, surface or Radius intermediate position, Medium r 1 (mm) and second limit] n d ν d S1 29.48 Lens 11 2.0 1.72342 37.95 S2 18.62 Lens 12 3.5 1.49700 81.63 S3 −176.25 Air Gap 1 31.65 . . . 23.18 . . . 2.00 S4 −123.57 Lens 13 2.0 1.57956 53.87 S5 12.93 Lens 14 3.0 1.76182 26.52 S6 19.69 Air Gap 2 14.70 . . . 2.64 . . . 15.35 S7 −19.69 Lens 15 3.0 1.76182 26.52 S8 −12.93 Lens 16 2.0 1.57956 53.87 S9 123.57 Air Gap 3 2.65 . . . 23.18 . . . 31.65 S10 176.25 Lens 17 3.5 1.49700 81.63 S11 −18.62 Lens 18 2.0 1.72342 37.95 S12 −29.48.