IR fast low light level lens system

• US 5,386,315 A
• Filed: 06/04/1993
• Issued: 01/31/1995
• Est. Priority Date: 08/26/1991
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Martin Marietta Corporation
• Inventors: Tejada, John, Amon, Max
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): NGUYEN, KIET TUAN
• Application Number:
  US08/071,610
• Time in Patent Office: 606 Days
• Field of Search: 359/350, 359/355, 359/356, 359/357, 359/738, 359/739, 359/740
• US Class Current: 359/350
• CPC Class Codes: G02B 13/14 for use with infrared or ultraviolet radiation G02B13/008, G02B13/16 take precedence
• CPC Class Codes: G02B 13/18 with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration G02B13/002 takes precedence

Abstract

A compound lens for use in a low light level system operating in the near-infrared region. The lens system includes a high light-gathering ability requiring both a large aperture and good transmissivity over the wavelengths of interest. A wide field of view (e.g., 50°) without excessive chromatic and geometric aberrations that generally accompanies systems with a large aperture is provided. Space is provided in the lens system for a variable iris and variable density spot subassembly. Desired optical quantities are obtained through the use of zinc selenide as the material for an aspheric lens. The use of this diamond-turnable infrared material as a field lens yields exceptional performance for a fast (e.g., F/1.25) lens with a wide field of view.

Claims

1. A low light level lens system, comprising:

a multiple element lens system designed to operate in the near-infrared region of 0.7 to 0.9 μ

m,

wherein at least one element comprises a zinc selenide lens element, said lens system having a wide field of view, and wherein the multiple element lens system comprises, in order of their appearance on a chief ray, a first negative meniscus lens, a first positive meniscus lens, a null planar window, a positive double convex lens in contact with a negative double concave lens, a positive double convex lens followed by contact with a positive meniscus lens, a second positive meniscus lens, and a second negative meniscus lens.

2. The low light level lens system according to claim 1 further comprising a concentric dome window as a tenth element.

3. A low light level lens system for operating in the near-infrared region of 0.7 to 0.9 μ

m, comprising;

a multiple element lens system wherein at least one element comprises a zinc selenide lens element, said lens system having a wide field of view; and

a variable transmission obstruction including an auto-iris and level lens system according to claim 1 wherein the variable transmission obstruction a variable density spot at the center of a lens element near an aperture stop.

4. A low light level lens system for Operating in the near-infrared region of 0.7 to 0.9 μ

m, comprising;

a multiple element lens system wherein at least one element comprises a zinc selenide lens element, said lens system having a wide field of view, wherein the multiple element lens system comprises the following basic lens data;

space="preserve" listing-type="tabular">__________________________________________________________________________SURFACE REFRACTIVE DISPERSION NUMBER RADIUS THICKNESS MEDIUM INDEX FACTOR __________________________________________________________________________ 0 0.00000000 1.00000000E+10 AIR 1 0.00000000 -1.33962709 AIR 2 3.02950000 0.16000000 MATL SILICA 1.453322 39.466 3 2.86950000 0.28000000 AIR 4 1.38248000 0.15748000 SCHOTT LAK9 1.681792 0.001 5 0.70122000 0.46961500 AIR 6 1.25596000 0.15527559 SCHOTT SF56 1.764913 1.061 7 3.68400000 0.23918300 AIR 8 0.00000000 0.08000000 SCHOTT BK7 1.510780 0.384 9 0.00000000 0.12085600 AIR 10 0.00000000 0.11600000 AIR 11 0.81102000 0.27559055 SCHOTT LAK9 1.681792 0.001 12 -0.81103000 0.08415354 SCHOTT SF56 1.764913 1.061 13 0.64814000 0.10478000 AIR 14 0.81103000 0.21653543 SCHOTT LAK9 1.681792 0.001 15 -1.37150000 0.00500000 AIR 16 0.45857000 0.14025590 SCHOTT LAK9 1.681792 0.001 17 0.40457000 0.10000000 AIR 18 0.77580000 0.09842520 MATL RZNSE 2.524186 2.427 19 1.08952000 0.03937008 AIR 20 1.38248000 0.06889764 MATL RZNSE 2.524186 2.427 21 0.70122000 0.11811023 AIR 22 0.00000000 0.22047244 MATL SILICA 1.453322 39.466 23 0.00000000 -0.88487939 AIR 24 0.00000000 0.88487939 AIR 25 0.00000000 0.00000000 AIR __________________________________________________________________________

5. A low light level lens system comprising:

a single-band multiple element lens system designed to operate in the near-infrared region of 0.7 to 0.9 μ

m,

wherein at least one element comprises a high index, diamond turnable lens, said lens system having a wide field of view and wherein the multiple element lens system comprises, in order of their appearance on a chief ray, a first negative meniscus lens, a first positive meniscus lens, a null planar window, a positive double convex lens in contact with a negative double concave lens, a positive double convex lens followed by contact with a positive meniscus lens, a second positive meniscus lens, and a second negative meniscus lens.

6. A low light level lens system comprising:

a single-band multiple element lens system designed to operate in the near-infrared region of 0.7 to 0.9 μ

m,

wherein at least one element comprises a high index, diamond turnable lens, said lens system having a wide field of view; and

a variable transmission obstruction,

wherein the variable transmission obstruction further comprises a variable density spot at the center of a lens element near an aperture stop.