Multiband, single element wide field of view infrared imaging system

• US 20030102435A1
• Filed: 11/20/2001
• Published: 06/05/2003
• Est. Priority Date: 11/20/2001
• Status: Abandoned Application

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Cole, Jeff, Falter, Peter, Myers, Mark
• Application Number:
  US09/988,660
• Publication Number:
  US 20030102435A1
• Time in Patent Office: Days
• US Class Current: 250/352
• CPC Class Codes: G01J 2005/0077 Imaging
• CPC Class Codes: G01J 5/061 by controlling the temperature of the apparatus or parts thereof, e.g. using cooling means or thermostats
• CPC Class Codes: G01J 5/08 Optical arrangements
• CPC Class Codes: G01J 5/0801 Means for wavelength selection or discrimination
• CPC Class Codes: G01J 5/0803 Arrangements for time-dependent attenuation of radiation signals
• CPC Class Codes: G01J 5/0806 Focusing or collimating elements, e.g. lenses or concave mirrors
• CPC Class Codes: G01J 5/0875 Windows; Arrangements for fastening thereof
• CPC Class Codes: G02B 13/14 for use with infrared or ultraviolet radiation G02B13/008, G02B13/16 take precedence
• CPC Class Codes: G02B 23/12 with means for image conversion or intensification
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: H04N 5/33 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

Abstract

A compact, wide field of view, infrared imaging system with two Mid-Wave Infrared (MWIR) and, optionally, an additional one Long-Wave Infrared (LWIR) band, has a single, color corrected lens element embedded within the detector/dewar assembly. The lens element has two aspherical surface profiles and utilizes a holographic optical element to manipulate and detect bands of energy that are harmonic components of each other. The infrared imaging system simplifies and shrinks the MWIR/LWIR imager while maintaining all of the required functionality. An exemplary infrared imaging apparatus performs at an F-stop (F/#) of at least 1.4 with a square field of view of 90×90 degrees.

Claims

1. An infrared imaging apparatus, comprising:

a dewar, having an internal volume that defines a cold space;

an IR transmissive window that seals the cold space to receive IR energy directly from an IR source;

a first lens located within the cold space to receive IR energy directly from the IR transmissive window;

an IR detector located within the cold space in operational communication with the first lens and positioned coincident to the focal plane of at least a first and second wavelength of IR energy; and

an optical stop located within the cold space in front of the single lens.

2. The infrared imaging apparatus of claim 1, wherein the single lens has a first aspheric profile on a first side and a second aspheric profile on a second side, the first side parallel to the second side and the second side facing the detector.

3. The infrared imaging apparatus of claim 2, wherein the second aspheric profile has a holographic optical element.

4. The infrared imaging apparatus of claim 3, wherein the holographic optical element color corrects at least one color band of infrared energy.

5. The infrared imaging apparatus of claim 4, wherein the holographic optical element color corrects a red MWIR band and a blue MWIR band.

6. The infrared imaging apparatus of claim 1, wherein the detector is a hyperspectral detector.

7. The infrared imaging apparatus of claim 1, wherein the detector detects at least three wavelengths of IR energy including at least one LWIR band of energy.

8. The infrared imaging apparatus of claim 1, wherein the LWIR band of energy is preferably an indigo LWIR band.

9. The infrared imaging apparatus of claim 1, wherein the holographic optical element coincidently focuses a MWIR band and a LWIR band of IR energy at a common focal plane.

10. The infrared imaging apparatus of claim 1, wherein the second wavelength of IR energy is a harmonic component of the first wavelength.

11. The infrared imaging apparatus of claim 1, wherein the single lens is made of germanium.

13. The infrared imaging apparatus of claim 1, wherein the single lens is made of silicon.

14. The infrared imaging apparatus of claim 1, wherein the apparatus performs at an F-stop (F/#) of at least 1.4 with a square field of view of 90×

90 degrees.

15. The infrared imaging apparatus of claim 1, wherein the detector concurrently collects radiation from multiple, adjacent spectral radiation bands.

16. The infrared imaging apparatus of claim 3, wherein the first aspheric surface has the following prescription:

radius=−

0.94467;

k=28.345216;

a=−

2.13952;

b=−

69.5274;

c=2342.04;

d=−

56841.9; and

first surface thickness=0.548467.

17. The infrared imaging apparatus of claim 16, wherein the second aspheric surface has the following prescription:

radius=−

0.61281;

k=0.1399;

a=0.033459;

b=−

2.3598;

c=10.889;

d=−

36.331; and

second surface thickness=0.462731.

18. The infrared imaging apparatus of claim 17, wherein the holographic optical element has the following prescription:

−

0.0051393, −

0.10212, 0.91035, −

2.3946.

19. The infrared imaging apparatus of claim 3, wherein the first aspheric surface has the following prescription:

radius=−

1.23508;

k=36.049455;

a=−

1.69104;

b=−

98.6413;

c=5589.83;

d=−

162359; and

first surface thickness=0.761661.

20. The infrared imaging apparatus of claim 19, wherein the second aspheric surface has the following prescription:

radius=−

0.81270;

k=−

0.10748;

a=0.054475;

b=−

0.72423;

c=2.9155;

d=−

7.8939; and

second surface thickness=0.480234.

21. The infrared imaging apparatus of claim 20, wherein the holographic optical element has the following prescription:

−

0.017112, −

0.038991, 0.55069, −

1.6405.