Multiband, single element wide field of view infrared imaging system

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.

What is claimed is:  
     
         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.