Infrared detection system with parallel strip reticle means

• US 4,027,160 A
• Filed: 05/18/1971
• Issued: 05/31/1977
• Est. Priority Date: 05/18/1971
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Kerr, Howard S., Driffield, John B., Penrose, Richard M., Stonell, Anthony C.
• Primary Examiner(s): Nelson, Peter A.
• Application Number:
  US05/144,282
• Time in Patent Office: 2,205 Days
• Field of Search: 250/83.3 R, 250/83.3 H, 73/355 R, 350/1, 350/2
• US Class Current: 250/339.02
• CPC Class Codes: G01S 3/781 Details
• CPC Class Codes: G01S 3/789 using rotating or oscillating beam systems, e.g. using mirrors, prisms
• CPC Class Codes: G02B 23/12 with means for image conversion or intensification
• CPC Class Codes: H01L 31/02164 for shielding light, e.g. light blocking layers, cold shields for infrared detectors

Abstract

Optical detectors are arranged along the focal length of a spherical mirr Signals passed by a lens and reflected by the mirror impinge on the detectors as the system scans the horizon. A reticle means is placed between the mirror and the detector to cause the optical system to discriminate against large radiating areas in the field of view of the lens. The reticle means may be straight or zig-zag opaque lines. The cross-sectional area of the lines and the area therebetween is such that radiation from point sources will impinge the detector in only one area at a time while radiation from large sources will overlap a plurality of areas. The output frequency from the detectors is indicative of the type of the radiation source.

Claims

1. An optical system for infrared detection comprising:

a viewing lens;

a mirror having a focal length, said mirror being positioned to receive the light passed by said viewing lens;

a plurality of detector cells positioned to lie in the focal length of said mirror;

reticle means positioned on said detector cells whereby said optical system differentiates between infrared radiation from large sources and point sources, wherein said mirror is a spherical mirror having an overcoat of silicon monoxide thereby providing maximum reflectivity in the wavelength region of 3 to 5 microns, wherein said viewing lens is an aspheric corrector shaped to correct said optical system for spherical aberration, said lens comprising optical silicon having a cut-on wavelength of approximately one micron thereby excluding radiation of less than one micron from said optical system, and wherein said reticle means is positioned between said mirror and said detector cells, said reticle means comprising a sapphire substrate having a reticle of parallel strips of an opaque material thereon.

2. An optical system as set forth in claim 1 wherein said strips of said opaque material are zig-zags whereby said optical system discriminates between point sources of emission and narrow, vertical band emission.