Single element radiometric lens

Patent metadata

Field	Value
Publication number	US-9615036-B2
Application number	US-201414208560-A
Country	US
Kind code	B2
Filing date	Mar 13, 2014
Priority date	Mar 14, 2013
Publication date	Apr 4, 2017
Grant date	Apr 4, 2017

Abstract

The disclosure describes systems and apparatuses that include a focusable lens, as well as methods for focusing the optical lens. The focusable lens system includes a single element lens having a concave refractive surface characterized by a first radius of curvature and a convex refractive surface characterized by a second radius of curvature larger than the first radius of curvature. A detector element generates electrical signals representative of infrared rays refracted by the single element lens and incident on the detector element, and an aperture stop is disposed around an optical axis of the optical system and secured in a constant position relative to the detector element, the aperture stop configured to limit a cone angle of rays refracted by the single element lens. They system also includes image processing circuitry configured to generate digital pixilation data based on electrical signals generated by the detector element.

First claim

What is claimed is:

1. A focusable optical system comprising:
a single element lens having a concave refractive surface characterized by a first radius of curvature and a convex refractive surface characterized by a second radius of curvature;
a detector element configured to generate electrical signals representative of infrared rays refracted by the single element lens and incident on the detector element, wherein the single element lens is characterized by:
a far scene focus position a first distance from the detector element; and
a near scene focus position a second distance from the detector element, the second distance being greater than the first distance;

an aperture stop disposed around an optical axis of the optical system and secured in a constant position relative to the detector element, the aperture stop being configured to limit a cone angle of rays refracted by the single element lens; and
image processing circuitry configured to generate digital pixilation data based on electrical signals generated by the detector element.

2. The focusable optical system of claim 1 , wherein the far scene focus position and the near scene focus position are displaced axially with respect to the detector.

3. The focusable optical system of claim 2 , wherein focusing of the single element lens does not alter a distance between the aperture stop and the detector element.

4. The focusable optical system of claim 3 , wherein the detector is operable over a wavelength range of 8 to 14 μm.

5. The focusable optical system of claim 1 , wherein an f-number of the focusable optical system is between 1 and 2.

6. The focusable optical system of claim 1 , wherein the single element lens comprises germanium.

7. The focusable optical system of claim 1 , wherein the single element lens is configured to be moved axially throughout a focusing range, and wherein the focusing range is such that, at multiple focusing positions in the focusing range, the lens protrudes through the aperture stop and a separation distance between a portion of the lens and the detector element is less than a separation distance between the aperture stop and the detector element.

8. A method of operating a focusable optical system, the method comprising:
focusing the optical system on a first scene located a first distance from the optical system, wherein focusing the optical system on the first scene includes axially displacing a single element radiometric lens along an optical axis of the optical system, wherein axially displacing the single element radiometric lens includes moving a portion of the single element radiometric lens through an opening in an aperture stop; and
focusing the optical system on a second scene located a second distance from the optical system, wherein the second distance is greater than the first distance, wherein focusing the optical system on the second scene includes axially displacing the single element radiometric lens along the optical axis such that a portion of the single element radiometric lens:
is moved towards a detector within the optical system; and
is moved through the opening in the aperture stop.

9. The method of claim 8 , wherein focusing the optical system on a first scene is such that, after being displaced axially, all of the single element radiometric lens is located to a first side of the aperture stop, wherein the detector is disposed on a second side of the aperture stop, the first side opposite the second side.

10. The method of claim 8 , wherein axially displacing the single element radiometric lens alters a distance between the aperture stop and the single element radiometric lens.

11. The method of claim 10 , wherein axially displacing the single element radiometric lens alters a distance between the single element radiometric lens and the detector.

12. The method of claim 8 , wherein the detector is operable over a wavelength range of 8 to 14 μm.

13. The method of claim 8 , wherein an f-number of the focusable optical system is between 1 and 2.

14. The method of claim 8 , wherein the single element lens comprises germanium.

Assignees

• Drs Rsta Inc
• Drs Network & Imaging Systems Llc

Inventors

• Southerland Richard L
• Durham Mark E
• Cronkite Patrick J

Classifications

• G02B7/38 Primary

  measured at different points on the optical axis {, e.g. focussing on two or more planes and comparing image data} · CPC title

• H04N23/23

  from thermal infrared radiation · CPC title

• G03B3/00

  Focusing arrangements of general interest for cameras, projectors or printers · CPC title

• H04N5/33 Primary

  Transforming infrared radiation (cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20) · CPC title

• G02B13/14

  for use with infrared or ultraviolet radiation ({G02B13/008, } G02B13/16 take precedence) · CPC title