U.S. patent application number 11/220016 was filed with the patent office on 2006-04-06 for hyperspectral imaging systems.
Invention is credited to Andrew Bodkin, Adam Norton, Andrew I. Sheinis.
Application Number | 20060072109 11/220016 |
Document ID | / |
Family ID | 36125182 |
Filed Date | 2006-04-06 |
United States Patent
Application |
20060072109 |
Kind Code |
A1 |
Bodkin; Andrew ; et
al. |
April 6, 2006 |
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.
Inventors: |
Bodkin; Andrew; (Wellesley,
MA) ; Sheinis; Andrew I.; (Madison, WI) ;
Norton; Adam; (Palo Alto, CA) |
Correspondence
Address: |
LATHROP & GAGE LC
4845 PEARL EAST CIRCLE
SUITE 300
BOULDER
CO
80301
US
|
Family ID: |
36125182 |
Appl. No.: |
11/220016 |
Filed: |
September 6, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60607327 |
Sep 3, 2004 |
|
|
|
Current U.S.
Class: |
356/328 ;
356/326 |
Current CPC
Class: |
G01J 3/0286 20130101;
G02B 3/08 20130101; G02B 5/045 20130101; G01J 3/0294 20130101; G01J
5/061 20130101; G01J 3/0262 20130101; G01J 3/36 20130101; G01J 3/02
20130101; G01J 3/2823 20130101; G01J 3/021 20130101; G01J 3/0235
20130101; G01J 3/14 20130101; G01J 3/2803 20130101; G02B 27/1066
20130101; G01J 3/0229 20130101; G02B 27/143 20130101; G01J 3/0205
20130101; G01J 3/0208 20130101; G01J 3/0256 20130101; G02B 3/0056
20130101; G02B 26/0883 20130101; G02B 27/123 20130101 |
Class at
Publication: |
356/328 ;
356/326 |
International
Class: |
G01J 3/28 20060101
G01J003/28 |
Goverment Interests
U.S. GOVERNMENT RIGHTS
[0002] The U.S. Government has certain rights in this invention as
provided for by the terms of Grant #F19628-03-C-0079 awarded by the
U.S. Air Force.
Claims
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.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. provisional
application Ser. No. 60/607,327, filed Sep. 3, 2004 and
incorporated herein by reference.
BACKGROUND
[0003] Hyperspectral imaging is a technique used for surveillance
and reconnaissance in military, geophysical and marine science
applications. Objects viewed by a hyperspectral imaging system are
often displayed in three-dimensions, x, y (spatial) and .lamda.
(color wavelength). Spatial observations (x, y) allow a person to
observe an image when high contrast is available. However, during
conditions of low contrast, such as fog, smoke, camouflage, and/or
darkness, or when an object is too far away to resolve, spectral
signatures help identify otherwise unobservable objects, for
example to differentiate between friendly and enemy artillery.
[0004] The hyperspectral imaging technique typically employs a
scanning slit spectrometer, although Fourier-transform imaging
spectrometers (FTIS), and scanning filter (Fabry-Perot) imaging
systems have also been used. These devices, however, record only
two-dimensions of a three-dimensional data set at any one time. For
example, the scanning slit spectrometer takes spectral information
over a one-dimensional field of view (FOV) by imaging a scene onto
a slit then passing that collimated image from the slit through a
dispersive element (prism) and re-imaging various wavelength images
of the slit onto a detector array. In order to develop
three-dimensional information, the slit is scanned over the entire
scene producing different images that must be positionally matched
in post-processing. The FTIS and Fabry-Perot techniques also scan;
the former scans in phase space, and the latter scans in
frequency
[0005] Current scanning spectrometer designs have resulted in
large, expensive and unwieldy devices that are unsuitable for
hand-held or vehicle applications. While these spectrometers have
been employed effectively in airborne and satellite applications,
they have inherent design limitations. These limitations arise due
to motion of the associated platform, motion or changes in the
atmosphere, and/or motion of the objects in the image field that
occur during scan sequences. Motion of the platform results in
mismatched and misaligned sub-images, reducing the resolution and
hence the effectiveness of the observations, while a moving object,
such as a missile, may escape detection if the object is moving
faster than the spectrometer scan rate.
SUMMARY
[0006] In one embodiment, a hyperspectral imaging system includes a
focal plane array and a grating-free spectrometer that divides a
field of view into multiple channels and that reimages the multiple
channels as multiple spectral signatures onto the detector
array.
[0007] In one embodiment, a hyperspectral imaging system includes a
lenslet array that divides a field of view into multiple channels,
optics that collimate electromagnetic energy of the multiple
channels from the lenslet array, a grating that disperses the
multiple channels into multiple spectral signatures and that
reflects the electromagnetic energy back through the optics, and a
focal plane array that detects the multiple spectral
signatures.
[0008] In one embodiment, a hyperspectral imaging system includes
imaging optics that form an image of an object, a focal plane
array, a lenslet array that forms multiple images of a pupil of the
imaging optics, and a prism and grating coupled to the lenslet
array, to disperse the multiple images as multiple spectral
signatures onto the focal plane array while blocking, by total
internal reflection within the prism, unwanted spectral orders.
[0009] In one embodiment, a hyperspectral imaging system is
provided. Imaging optics form an image of an object. An image
slicer partitions a field of view of the imaging optics. For each
partitioned part of the field of view, a focal plane array and a
spectrometer divide a portioned field of view into multiple
channels and reimage the multiple channels as multiple spectral
signatures onto the focal plane array.
[0010] In one embodiment, a multiwavelength imager is provided.
Imaging optics form an image of an object. At least one
micromachined optical element (MMO) is located at or near to an
image plane of the imager, providing a spectral signature for use
with a focal plane array.
[0011] In one embodiment, a hyperspectral imaging system includes
imaging optics that form an image of an object. A spectrometer has
an array of pinholes that divide a field of view of the imaging
optics into multiple channels. Dispersive optics reimage the
multiple channels as multiple spectral signatures onto a focal
plane array.
[0012] In one embodiment, a hyperspectral imaging system includes 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 and aligned such that each
lenslet of the lenslet array corresponds to a pinhole of the
pinhole array. The lenslet array is moveable to define where an
object is viewed by the imaging system. A spectrometer reimages
multiple channels from the lenslet array as multiple spectral
signatures onto the detector array.
[0013] In one embodiment, a hyperspectral imager includes the
improvement of 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.
[0014] In one embodiment, a hyperspectral imager of the type that
forms a hyperspectral data cube includes the improvement of at
least one zoom collimating or relay lens that variably adjusts
spectral and spatial resolution of the hyperspectral data cube.
BRIEF DESCRIPTION OF THE FIGURES
[0015] FIG. 1 illustrates a hyperspectral imaging system in accord
with an embodiment.
[0016] FIG. 2 illustrates a hyperspectral imaging system including
crossed prisms that produce minimal dispersion of electromagnetic
energy in accord with an embodiment.
[0017] FIG. 3 illustrates a hyperspectral imaging system including
crossed prisms that produce a large degree of dispersion in accord
with an embodiment.
[0018] FIG. 4 illustrates an intensity pattern from a
two-dimensional lenslet array.
[0019] FIG. 5 illustrates an intensity pattern of spectra spread
from individual channels.
[0020] FIG. 6 illustrates a hyperspectral imaging system including
a micromachined optical (MMO) assembly in accord with an
embodiment.
[0021] FIG. 7 illustrates exemplary MMO's of FIG. 6.
[0022] FIG. 8 illustrates a cross-section of one MMO assembly in
accord with an embodiment.
[0023] FIG. 9 illustrates a hyperspectral imaging system including
a reflective grating in accord with an embodiment.
[0024] FIG. 10 illustrates a hyperspectral imaging system including
an image slicer in accord with an embodiment.
[0025] FIG. 11 illustrates a hyperspectral imaging system including
a pinhole array in accord with an embodiment.
[0026] FIG. 12 illustrates a hyperspectral imaging system including
a lenslet array and a pinhole array in accord with an
embodiment
[0027] FIG. 13 illustrates an assembly wheel incorporating various
MMOs in accord with an embodiment.
DETAILED DESCRIPTION
[0028] A hyperspectral imaging system is disclosed herein which may
achieve high instrument resolution by recording three-dimensions,
two spatial dimensions (x and y) and a spectral or color dimension
(.lamda.), simultaneously. Further, the hyperspectral imager may be
handheld and operate to disperse and refocus an image without using
moving parts. The imaging optics may for example image faster than
at least f/5.
[0029] A hyperspectral imaging system 100 is shown in FIG. 1.
System 100 uses a two-dimensional lenslet array 102 at or near to
an image plane 105 of imaging optics 104, to resample an image
formed by imaging optics 104; lenslet array 102 is part of a
spectrometer 106, discussed in more detail below. Imaging optics
104 are illustratively shown as a Cassegrain telescope but may
instead comprise optical elements (e.g., as in FIG. 6) including
refractive optical elements. Accordingly, imaging optics 104 may be
a camera lens or other optical system that customizes imaging
specifications by modifying f-number, modifying magnification,
providing cold shielding, and/or providing filtering. Imaging
optics 104 are illustratively shown imaging incoming
electromagnetic radiation 103 onto image plane 105.
[0030] Spectrometer 106 divides the image from imaging optics 104
into multiple channels, where each channel forms a pupil image that
is focused as a spot 400 in an image plane 4-4 of lenslet array
102, as shown in FIG. 4. One exemplary channel 107 is shown in FIG.
1. In addition to lenslet array 102, spectrometer 106 includes a
collimating lens 108, a dispersive element 110, and a focusing lens
112. Dispersive element 110 is, for example, a prism that separates
spots 400 into multiple spectral signatures. A second dispersive
element 110(2), as shown in FIGS. 2 and 3, may be used to vary the
diffractive power of the first dispersive element 110; for example,
dispersive elements 110 and 110(2) may form a pair of crossed
prisms where one of the dispersive elements may be rotated relative
to the other in order to increase or decrease dispersion. FIG. 2
illustrates a hyperspectral imaging system having crossed prisms
110, 100(2) that produces minimal dispersion of electromagnetic
energy. FIG. 3 illustrates a hyperspectral imaging system having
crossed prisms 110, 100(2) that produces a large dispersion of
electromagnetic energy.
[0031] Those skilled in the art, upon reading and fully
appreciating this disclosure, will appreciate that elements 108,
112 of FIG. 1 may comprise additional or different types of optical
elements (e.g., mirrors) to form like function, without departing
from the scope hereof.
[0032] As illustrated in FIG. 4, each spectral signature is
associated with a single spot 400 (each spot 400 from a
corresponding lenslet of array 102) and is recorded simultaneously
on a two-dimensional focal plane array 114. In one example, images
are spread into several hundred color bands and about 1,000 spatial
locations on a 100.times.100 CCD detector. A CCD detector may be
used for detection in the visible region, while various other
detectors may be used for detection in other parts of the
electromagnetic spectrum, e.g., ultraviolet (UV), near infrared
(NIR), mid-wave infrared (MWIR), long-wave infrared (LWIR) and/or
microwave regions. Spectrometer 106 may thus be formed of optical
elements that transmit and function in a particular waveband. An
uncooled microbolometer may be used as focal plane array 114 when
the waveband is infrared (e.g., 8-12 microns), for example.
[0033] The images received by focal plane array 114 are captured by
a computer processor 116 and both the location of an image and the
spectral information for that location are processed into a
three-dimensional data set denoted herein as a hyperspectral data
cube 118. The data are collected in parallel and may be saved to
memory and/or viewed in real time in any of the several hundred
wavebands recorded. Data cubes 118 are collected at the speed of
the digital detector array, typically limited by its internal
digital clock. Thus data cubes may be read, for example, at a rate
between 1-1000 data cubes per second with a spectral resolution in
a range of about 1-50 nm, for example.
[0034] As illustrated in FIG. 5, the dispersing direction (i.e.,
angle of dispersive element 110 relative to focal plane 114) may be
rotated about the optical axis to avoid overlap of different
spectra 500 on detector 114. Tilt angle B allows the spectral
images to tilt between each other along the pixel separation
distance A. For example, tilt angle B may range from about 10 to 20
degrees. The length of spectrum 500 is determined by the
diffracting power of dispersive element(s) 110 and/or by a filter
(see, e.g., FIG. 9). Accordingly, spectral resolution may be traded
for spatial resolution and vice versa. For a given detector size,
the number of spectral bands may be doubled, for example, by
increasing the dispersion of the prism and halving the
lenslet-array size (and, hence, halving the number of spatial
lenslet elements). A zoom collimating or relay lens may also be
used to variably adjust spectral and spatial resolution.
[0035] Referring again to FIG. 1, imaging optics 104 may be omitted
from the hyperspectral imager in certain applications; in this
embodiment, therefore, lenslet array 102 and a pinhole array serve
to image the object as the multiple channels through the
spectrometer 106. See, e.g., FIG. 9.
[0036] FIG. 6 shows each optic of lenslet array 102 as a
micromachined optical element ("MMO") 600 that both disperses and
refocuses light. Expanded cross-sectional views of several
exemplary MMO's are shown in FIG. 7. For example, MMO 600(1) may
include a lens 702 coupled to a transmissive grating 704 (although
grating 704 is shown on the back of lens 702, it may instead be on
the front of lens 702). In another example, MMO 600(2) includes a
lens 702 coupled to a prism 706 and a transmissive grating 704.
Prism 706 may be configured to block a selected order by total
internal reflection within the prism, but yet allow other spectral
orders to be transmitted through lens 702 and diffracted by
transmissive grating 704. See, e.g., FIG. 8. In yet another
example, a Fresnel lens 708 is coupled with a transmissive grating
704 as part of MMO 600(3).
[0037] The use of MMO's may reduce the overall size and complexity
of the hyperspectral imaging system, as well as increase the
durability of the instrument using the hyperspectral imaging
system, because there are no moving parts. Since the MMO's are
micromachined they are ideally suited for manufacturing in silicon
for use in infrared imagers. Alternatively, using a low cost
replicating technique, the MMO's may be molded into epoxy on glass,
for use in the visible waveband. Gratings may be applied to the
MMO's during the molding process or by chemical etching,
photolithography and the like.
[0038] FIG. 8 illustrates a cross-section of lenslet array 102
having lenses 702 for receiving and refocusing radiation. Each lens
702 is coupled with a prism 706 (and/or grating) that disperses
radiation into its constituent wavelengths (spectral signature)
onto focal plane array 114.
[0039] FIG. 9 illustrates a hyperspectral imaging system 900
including a reflective grating 902. Electromagnetic energy 903 may
be received directly by lenslet array 102 or transmitted through
imaging optics 104 (not shown). Lenslet array 102 images and
divides a field of view into multiple channels that are transmitted
through spectrometer 106, which illustratively includes both
collimator 108 and focusing lens 112. Spectrometer 106 may, for
example, be an aspheric optical component manufactured of
transmissive germanium, to operate in the infrared. Electromagnetic
energy transmitted through spectrometer 106 is reflected and
diffracted by reflective grating 902, which is for example used in
a Littrow configuration. The reflected electromagnetic energy 903A
is transmitted back through spectrometer 106 and reflected by a
fold mirror 904 through a filter 906 onto a focal plane array 114.
Filter 906 may, for example, limit spectral length A (FIG. 5) and
prevent spectral overlap on detector 114.
[0040] FIG. 10 illustrates a hyperspectral imaging system 1000
including an image slicer 1002. Image slicer 1002 divides an image
received from imaging optics 104. In the embodiment of FIG. 10,
each slice of electromagnetic energy intersects a reflective
element 1004 that transmits its associated energy to a designated
spectrometer and detector combination. For example, the
spectrometer/detector combination may be that of hyperspectral
imaging system 900, although other hyperspectral imaging systems
may be employed. Use of lenslet array 102 in combination with image
slicer 1002 produces a two-dimensional field of view divided into
multiple channels that can be dispersed by a grating without order
overlap.
[0041] FIG. 11 illustrates a hyperspectral imaging system 1100
including a pinhole array 1102. Pinhole array 1102 may be used in
place of, or in addition to, lenslet array 102 to divide the image
into multiple channels through pinholes. Pinhole array 1102 may be
positioned at or near to the image plane of imaging optics 104. In
one embodiment, pinhole array 1102 is moveable so that pinhole
array 1102 is positioned to capture selective field positions of
the object sampled by system 1102. If pinhole array 1102 is
positioned near to, but not at the image plane, then defocus energy
transmits through pinholes of array 1102 such that integration of
field positions occurs through the several channels of system 1100.
Pinhole array 1102 may be reflective to act as a narcissus mirror,
to reduce background radiation in the case of infrared imaging.
Similarly, pinhole array 1102 may be absorbing and cooled to reduce
background radiation, which is particularly beneficial when the
waveband sampled by the spectrometer is in the infrared. A
collimating lens 108, dispersive element 110, and focusing lens 112
may be used in conjunction with pinhole array 1102 to disperse and
refocus multiple channels into multiple spectral signatures on
focal plane array 114.
[0042] FIG. 12 illustrates a hyperspectral imaging system including
lenslet array 102 and pinhole array 1102. Lenslet array 102 may be
located between the object and pinhole array 1102 with each lens
600 of lenslet array 102 aligned with a corresponding pinhole of
pinhole array 1102. The pitch of lenslet array 102 and pinhole
array 1102 are the same when imaging optics 104 is present, i.e.,
each pinhole is located at the optical axis of a lens 600. If
imaging optics 104 is not present within system 1100,
electromagnetic energy 103 may be directly sampled by lenslet array
102 and pinhole array 1102 by differing the pitch between lenslet
array 102 and pinhole array 1102. The pitch between lenslet array
102 and pinhole array 1102 are made to differ by offsetting the
optical axis of one array relative to the other.
[0043] Multiple hyperspectral imagers may be used to cover a large
field of view. For example, the exterior of a surveillance plane
may be covered with multiple hyperspectral imagers. Data from the
multiple imagers may be compiled into one comprehensive data set
for viewing and analysis.
[0044] Alternatively, a large-scale hyperspectral imager may be
fabricated according to the present instrumentalities. For example,
a large-scale imager may be used in aerial or satellite
applications. The costs of fabricating and transporting an imager
as herein disclosed may be less than similar costs associated with
a traditional hyperspectral imaging system due to the decreased
number of optical components and weight thereof.
[0045] A large degree of flexibility is available where, for
example, imaging optics, lenslet arrays, pinhole arrays, detectors,
filters, and the like may be interchanged as necessary for a
desired application of the hyperspectral imaging system. In one
embodiment, illustrated in FIG. 13, a micromachined optical (MMO)
assembly wheel 1300 for positioning multiple MMO's formed into
lenslet arrays 102 within the imaging system is provided. Selection
of any one lenslet array 102 provides differing spectral signatures
from any other lenslet array of MMO wheel 1300. For example,
lenslet arrays 102(1) and 102(2) provide hexagonally packed MMO's
600(4) and 600(5), respectively. However, MMO's 600(5) may include
different optical components, i.e., filters, gratings and/or
prisms, than MMO's 600(4). Lenslet arrays 102(3) and 102(4) provide
close packed hexagonal arrangements of MMO's 600(6) and 600(7),
respectively, and the optical components of MMO's 600(6) and 600(7)
may differ. MMO's 600(4) and 600(5) are larger than MMO's 600(6)
and 600(7). Large MMO's may provide for decreased spatial
resolution, but increased spectral resolution.
[0046] It is also possible that lenses 600, that are not coupled
with gratings 704 or prisms 706, may be utilized in a MMO wheel
1300. It may then be desirable to vary the amount of dispersion to
accommodate various lens sizes. For example, dispersive element(s)
110 may be rotated to increase dispersion when large lenses 600 are
used and decrease dispersion when small lenses 600 are used to
sample an image. Zoom lenses may also be used beneficially with
differing MMOs within the hyperspectral imaging system.
[0047] Object identification, which is more than mere recognition,
may be performed by software to distinguish objects with specific
spatial and spectral signatures. For example, materials from which
objects in the image are made may be spectrally distinguished,
e.g., in the visible range, paint on an enemy tank may be
distinguished from paint on a friendly tank, while in the infrared
region, a water treatment plant may be distinguished from a
chemical weapons factory. The software may be trained to color code
or otherwise highlight elements of the image with particular
spatial and/or spectral signatures.
[0048] Certain changes may be made in the systems and methods
described herein without departing from the scope hereof. It should
thus be noted that the matter contained in the above description or
shown in the accompanying drawings should be interpreted as
illustrative and not in a limiting sense. The following claims are
intended to cover all generic and specific features described
herein, as well as all statements of the scope of the present
method and system, which, as a matter of language, might be said to
fall there between.
* * * * *