Objective lens system
AssigneeOlympus Optical Co., Ltd.
InventorToshiyuki Nagaoka
Life of this patent
Estimating the term…
Abstract
An objective lens system consisting of a first lens unit having a negative refractive power and a second lens unit having a positive refractive power wherein the first lens unit or the second lens unit comprises at least one radial type gradient index lens element which has a refractive index distribution in a radial direction from an optical axis. This objective lens system favorably corrects chromatic aberration and other aberrations by adequately selecting a value expressing an Abbe's number and a refractive power of medium for the radial type gradient index lens element.
Claims7
An objective lens system comprising, in order from the object side:
- a first lens unit consisting of a lens element having a homogeneous lens medium and having a negative refracting power, said first lens unit being the most object-side lens unit of said objective system;
- and
- a second lens unit consisting of a lens element having a radial type gradient refractive index and having a positive refractive power, said second lens unit being the second most object-side lens unit of said objective system,
- wherein only one radial type gradient index lens element, which has a refractive index distribution in a radial direction from an optical axis, is disposed in said second lens unit and in the lens system as a whole,
- wherein said radial type gradient index lens element has a planar surface on at least one side, and
- wherein said radial type gradient index lens element satisfies the following condition (6):
- 1/V.sub.10 <0.01 (6)
- wherein the reference symbol V.sub.10 represents a dispersing power of said radial type gradient index lens element which is given by the formula (c) shown below:
- V.sub.10 =N.sub.10d /(N.sub.10F -N.sub.10c)
- wherein the reference symbols N.sub.10d, N.sub.10F and N.sub.10C designate values of a coefficient of a term r.sup.2 for the d-line, F-line and C-line, respectively, when a refractive index of said radial type gradient index lens element is expressed as a polynomial of r.
Dependencies are inferred from the claim text.