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Eyepiece lens system for endoscopes

  • US 5,305,147 A
  • Filed: 08/19/1991
  • Issued: 04/19/1994
  • Est. Priority Date: 08/20/1990
  • Status: Expired due to Fees
First Claim
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1. An endoscope observation system comprising an image guide and an eyepiece lens system, said eyepiece lens system comprising, in order from the eye side:

  • a first lens unit having a positive refractive power, anda second lens unit having a negative refractive power;

    wherein said second lens unit comprises a concave aspherical surface satisfying the following condition, and said second lens unit satisfies one of the conditions (A) and (B);

    ##EQU7## wherein an optical axis of the eyepiece lens system is taken as the x axis, a direction perpendicular to the optical axis is taken as the y axis, an intersection between the aspherical surface and the optical axis is taken as an origin on a coordinate system, the reference symbol C represents curvature on a spherical surface in contact with the aspherical surface on the optical axis, the reference symbol P designates a conical coefficient, the reference symbols B, E, F, G, . . . denote aspherical surface coefficients of the second order, fourth order, sixth order, eighth order, . . . , the reference symbol N represents a refractive index of a medium located on the eye side of the aspherical surface, the reference symbol N'"'"' designates a refractive index of a medium located on the object side of the aspherical surface, the reference symbol An denotes any one of aspherical surface coefficients of the fourth and higher orders, and the reference symbol Bn represents an aspherical surface coefficient of the second order, the suffix n having a meaning that the aspherical surface coefficient relates to an aspherical surface having a concave shape.

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