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Objective lens system for endoscopes

  • US 4,662,725 A
  • Filed: 02/12/1985
  • Issued: 05/05/1987
  • Est. Priority Date: 02/15/1984
  • Status: Expired due to Term
First Claim
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1. A retrofocus-type objective for endoscopes comprising a front lens group having negative refractive power, a rear lens group having positive refractive power in the order from object side, and a stop arranged between said front and rear lens groups, said front lens group comprising a negative lens element having a concave surface having a selected curvature which is strong and a positive lens element, and said rear lens group having at least two positive lens components, one of said positive lens components being a cemented doublet having a positive lens element and negative lens element the cemented surface of which is convexed to the image side, and at least one of the lens components in said front lens group having an aspherical surface on the object side thereof including portions whose curvature is gradually increased as the distance thereof increases from the optical axis.

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