Hyperspectral imaging systems

Abstract

Hyperspectral imaging systems that may be used for imaging objects in three-dimensions with no moving parts are disclosed. A lenslet array and/or a pinhole array may be used to reimage and divide the field of view into multiple channels. The multiple channels are dispersed into multiple spectral signatures and observed on a two-dimensional focal plane array in real time. The entire hyperspectral datacube is collected simultaneously.

1 . A hyperspectral imaging system, comprising: 
 a focal plane array; and    a grating-free spectrometer for dividing a field of view into multiple channels and for reimaging the multiple channels as multiple spectral signatures onto the focal plane array.    
   
   
       2 . The system of  claim 1 , further comprising imaging optics for forming an image of an object within the field of view.  
   
   
       3 . The system of  claim 2 , wherein the grating-free spectrometer comprises an array of pinholes dividing the field of view of the imaging optics to form the multiple channels, the pinholes being positioned adjacent to an image formed by the imaging optics, to blur energy from the image of the object into at least one of the channels.  
   
   
       4 . The system of  claim 2 , wherein the grating-free spectrometer comprises a lenslet array and an array of pinholes to sample the image.  
   
   
       5 . The system of  claim 4 , wherein the imaging optics image faster than at least f/5.  
   
   
       6 . The system of  claim 2 , wherein the grating-free spectrometer comprises an array of pinholes dividing the field of view of the imaging optics to form the multiple channels.  
   
   
       7 . The system of  claim 6 , the pinholes formed by a narcissus mirror with an array of apertures, to reduce background radiation onto the focal plane array.  
   
   
       8 . The system of  claim 6 , the pinholes formed by an optically absorbing material with an array of aperatures, the absorbing material being cooled to reduce background radiation onto the focal plane array.  
   
   
       9 . The system of  claim 1 , the grating-free spectrometer comprising: (a) a lenslet array, to form the multiple channels; (b) optics, to collimate electromagnetic energy of the multiple channels from the lenslet array; (c) a prism, to disperse the electromagnetic energy of the multiple channels into multiple spectral signatures; and (d) optics to image the spectral signatures onto the focal plane array.  
   
   
       10 . The system of  claim 9 , wherein the grating-free spectrometer comprises an array of pinholes dividing the field of view of the imaging optics to form the multiple channels.  
   
   
       11 . The system of  claim 10 , the pinholes formed by a narcissus mirror with an array of apertures, to reduce background radiation onto the focal plane array.  
   
   
       12 . The system of  claim 10 , the pinholes formed by an optically absorbing material with an array of aperatures, the absorbing material being cooled to reduce background radiation onto the focal plane array.  
   
   
       13 . The system of  claim 1 , further comprising a processor connected with the focal plane array for forming a hyperspectral data cube from the multiple spectral signatures, wherein objects may be identified from the hyperspectral data cube.  
   
   
       14 . The system of  claim 1 , the grating-free spectrometer comprising: first optics for collimating electromagnetic energy of an object along an optical axis; a first prism for dispersing the electromagnetic energy; a second prism for redirecting the spectra of the first prism along the optical axis; second optics for focusing electromagnetic energy along the optical axis from the second prism and onto the focal plane array.  
   
   
       15 . A hyperspectral imaging system, comprising: 
 a lenslet array for dividing a field of view into multiple channels;    optics for collimating electromagnetic energy of the multiple channels from the lenslet array;    a grating for dispersing the multiple channels into multiple spectral signatures and for reflecting the electromagnetic energy back through the optics; and    a focal plane array for detecting the multiple spectral signatures.    
   
   
       16 . The system of  claim 15 , further comprising imaging optics for forming an image of an object within the field of view.  
   
   
       17 . A hyperspectral imaging system, comprising: 
 imaging optics for forming an image of an object;    a focal plane array;    a lenslet array for forming multiple images of a pupil of the imaging optics; and    a prism and grating coupled to the lenslet array, for dispersing the multiple images as multiple spectral signatures onto the focal plane array while blocking, by total internal reflection within the prism, unwanted spectral orders.    
   
   
       18 . A hyperspectral imaging system, comprising: 
 imaging optics for forming an image of an object;    an image slicer for partitioning a field of view of the imaging optics; and, for each partitioned part of the field of view:    a focal plane array; and a spectrometer for dividing a portioned field of view into multiple channels and for reimaging the multiple channels as multiple spectral signatures onto the focal plane array.    
   
   
       19 . The system of  claim 18 , further comprising an array of pinholes configured to sample the image and divide the field of view to form the multiple channels.  
   
   
       20 . The system of  claim 19 , further comprising a lenslet array, wherein each lenslet of the lenslet array is aligned with a corresponding pinhole of the pinhole array.  
   
   
       21 . The system of  claim 18 , the spectrometer comprising: (a) a lenslet array, to form the multiple channels; (b) optics, to collimate electromagnetic energy of the multiple channels from the lenslet array; and (c) a reflection grating, to disperse the multiple spectral signatures back through optics and to the focal plane array.  
   
   
       22 . The system of  claim 18 , the spectrometer comprising: (a) a lenslet array oriented such that a two dimensional segment of the partitioned field of view images onto a two dimensional portion of the lenslet array; (b) optics, to collimate electromagnetic energy of the multiple channels from the lenslet array; and (c) a reflection grating oriented such that at least one spectrum images back through the optics and onto the focal plane array along a direction of dispersion.  
   
   
       23 . A multiwavelength imager, comprising: 
 imaging optics for forming an image of an object;    a focal plane array; and    at least one micromachined optical element (MMO) located at or near to an image plane of the imager, for providing a spectral signature for use with the focal plane array.    
   
   
       24 . The imager of  claim 23 , the MMO comprising a lenslet array and grating to image the pupil and divide it into wavelengths.  
   
   
       25 . The imager of  claim 23 , further comprising an assembly wheel for positioning multiple MMOs within the imager wherein selection of any one MMO provides differing spectral signatures from any other MMO of the assembly wheel.  
   
   
       26 . A hyperspectral imaging system, comprising: 
 imaging optics for forming an image of an object;    a focal plane array; and    a spectrometer having an array of pinholes that divide a field of view of the imaging optics into multiple channels and dispersive optics for reimaging the multiple channels as multiple spectral signatures onto the focal plane array.    
   
   
       27 . A hyperspectral imaging system, comprising: 
 a lenslet array;    a focal plane array;    a pinhole array between the detector array and the lenslet array, the pinhole array having a different pitch than the lenslet array, the lenslet array moveable to define where an object is viewed by the imaging system, wherein each lenslet of the lenslet array is aligned with a corresponding pinhole of the pinhole array; and    a spectrometer for reimaging multiple channels from the lenslet array as multiple spectral signatures onto the detector array.    
   
   
       28 . In a hyperspectral imager, the improvement comprising: 
 at least one zoom lens for selecting a variable field of view of the imager; and    a variable dispersion element for selecting dispersion for spectral signatures for the imager.    
   
   
       29 . A hyperspectral imager of  claim 28 , wherein the variable dispersion element is a pair of crossed prisms.  
   
   
       30 . In a hyperspectral imager of the type that forms a hyperspectral data cube, the improvement comprising: 
 at least one zoom collimating or relay lens that variably adjusts spectral and spatial resolution of the hyperspectral data cube.