Telescope objective system for the infrared range

Patent 4494819 Issued on January 22, 1985. Estimated Expiration Date:

December 29, 2003. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.

Abstract Claims Description Full Text

Patent References

3363962

3778133

3817604

3883214

Achromatic objective lens Patent #: 4190324
Issued on: 02/26/1980
Inventor: Arai

Inventor

Lidwell, Michael O.

Assignee

Barr & Stroud Limited

Application

No. 06/566699 filed on 12/29/1983

US Classes:

359/356, Infrared lens359/748, With less than four components359/785+ - + Arrangement

Examiners

Primary: Corbin, John K.
Assistant: Dzierzynski, Paul M.

Attorney, Agent or Firm

Mason, Fenwick & Lawrence

International Class

G02B 13/14 (20060101)

Foreign Application Priority Data

1980-03-05 GB

Abstract

A telescope objective system (10) is formed by a primary lens having a single lens element (A) aligned on a common optical axis (11) with a secondary lens having two lens elements (B,C) the shape and power distribution of lens elements (A,B,C) being such as to compensate for monochromatic aberration of the system, each lens element (A,B,C) being made of a material which has a useful spectral bandpass in the infrared wavelength region and lens elements (B,C) having refractive surfaces (16, 15, 14, 13) intercepting the optical axis (11) which are substantially spherical, the system having a planar image surface (11) and an effective focal length greater than the axial distance between the image surface (11) and the distal refractive surface (18) formed by the primary lens element (A). Primary lens element (A) is positively powered and made of germanium and at least one of the secondary lens elements (B,C) is made of a Chalcogenidae glass such that the system (10) is achromatic in the infrared wavelength region. Conveniently lens element (B) is made of Chalcogenide glass and is negatively powered. Lens element (C) may be negatively powered and made of germanium, or positively powered and made of a Chalcogenide glass.