U.S. patent application number 13/888264 was filed with the patent office on 2015-08-13 for latent fingerprint detectors and fingerprint scanners therefrom.
This patent application is currently assigned to LOCKHEED MARTIN CORPORATION. The applicant listed for this patent is LOCKHEED MARTIN CORPORATION. Invention is credited to V. Edward Gold, JR., Edward Miesak.
Application Number | 20150227773 13/888264 |
Document ID | / |
Family ID | 45996262 |
Filed Date | 2015-08-13 |
United States Patent
Application |
20150227773 |
Kind Code |
A1 |
Miesak; Edward ; et
al. |
August 13, 2015 |
LATENT FINGERPRINT DETECTORS AND FINGERPRINT SCANNERS THEREFROM
Abstract
An automatic fingerprint system includes an optical sensor
having a first light source that provides a collimated beam for
interrogating a first sample surface, and a camera including a lens
and a photodetector array having a camera field of view
(FOV.sub.CAMERA)large enough to image the first sample surface. The
camera is critical angle positioned relative to the first light
source to receive specular reflection (glare) from the first sample
surface to generate image data from the glare. The first light
source and camera have substantially equal and opposite numerical
apertures (NAs), A computer or processor that includes reference
fingerprint templates receives a digitized form of the image data,
and includes data processing software for (i) comparing the image
data to reference fingerprint templates to determine whether the
image data includes at least one fingerprint and (ii) for
generating a fingerprint image if the fingerprint is determined to
be present.
Inventors: |
Miesak; Edward; (Windermere,
FL) ; Gold, JR.; V. Edward; (Oviedo, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LOCKHEED MARTIN CORPORATION; |
|
|
US |
|
|
Assignee: |
LOCKHEED MARTIN CORPORATION
Bethesda
MD
|
Family ID: |
45996262 |
Appl. No.: |
13/888264 |
Filed: |
May 6, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13049351 |
Mar 16, 2011 |
8437517 |
|
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13888264 |
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61409753 |
Nov 3, 2010 |
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Current U.S.
Class: |
382/124 |
Current CPC
Class: |
G01N 2201/10 20130101;
G01N 2201/06113 20130101; G06K 9/00013 20130101; G01N 21/8851
20130101; G06K 9/2036 20130101; G06K 9/00033 20130101; G01N 21/94
20130101 |
International
Class: |
G06K 9/00 20060101
G06K009/00; G01N 21/94 20060101 G01N021/94 |
Goverment Interests
U.S. GOVERNMENT RIGHTS
[0002] The U.S. Government has certain rights to disclosed
embodiments based on Contract No. W91 INF-10-C-0029 between
Lockheed Martin Corporation and the U.S. Army.
Claims
1. A latent fingerprint detection system, comprising: a first light
source that illuminates a sample surface such that the sample
surface produces specular reflection; and an optical detector
arranged at a critical alignment angle relative to the first light
source such that the optical detector captures the specular
reflection from the sample surface and generates image data using
essentially only the specular reflection to generate image data of
the sample surface; and an image processor that: analyzes said
generated image data to determine if said generated image data
includes a fingerprint; and produces image data of the fingerprint
responsive to a determination that said analyzed image data
includes a fingerprint.
2. The system of claim 1, wherein said first light source and said
optical detector have substantially equal and opposite numerical
apertures.
3. The system of claim 1, wherein the optical detector is aligned
relative to said sample surface at an alignment angle that is
substantially equal to an angle of reflection from the sample
surface of the light provided by said first light source.
4.-10. (canceled)
11. The system of claim 1, wherein said image processor analyzes
said image data of the sample surface to determine if said image
data includes a fingerprint by performing slope detection.
12. The system of claim 1, further comprising a second light source
that illuminates a sample surface such that the sample surface
produces diffuse reflection.
13. The system of claim 1, further comprising: at least one scanner
mechanically coupled to said optical detector for scanning said
optical detector across a plurality of regions of interest on said
sample surface.
14.-17. (canceled)
18. A method of detecting surface contaminants using specular
reflection, comprising: illuminating a sample surface with a first
light source such that the sample surface produces specular
reflection; arranging an optical detector at a critical alignment
angle relative to the first light source such that the optical
detector captures the specular reflection from the sample surface
and generates image data using essentially only the specular
reflection to generate image data of the sample surface; analyzing
said generated image data of the sample surface to determine if
said generated image data includes an image of a surface
contaminant; and producing image data of the contaminated area
responsive to a determination that said analyzed image data
includes an image of a surface contaminant.
19. The method of claim 18, wherein said arranging further
comprises configuring said first light source and said optical
detector such that they have substantially equal and opposite
numerical apertures.
20. The method of claim 18, wherein said arranging further
comprises aligning said optical detector relative to said sample
surface at an alignment angle that is substantially equal to an
angle of reflection from the sample surface of the light provided
by said first light source.
21.-27. (canceled)
28. The method of claim 18, wherein said surface contaminant
comprises a fingerprint and said analyzing includes performing
slope detection on said image data of the sample surface.
29. The method of claim 18, further comprising second illuminating
a sample surface with a second light source such that the sample
surface produces diffuse reflection.
30. The method of claim 18, wherein said surface contaminant is a
fracture or physical defect in the sample surface.
31. The method of claim 18, wherein illuminating a sample surface
with a first light source further comprises illuminating said
sample surface with a plurality of parallel aligned fluorescent
tubes aligned fluorescent tubes arranged to collimated light as
well as non-collimated light.
32.-33. (canceled)
34. A latent fingerprint detection system, comprising: a light
source alignment portion configured to align a light source at an
illumination angle relative to a sample surface such that said
light source illuminates said sample surface so that the sample
surface produces specular reflection; and a specular reflection
discriminator configured to direct the produced specular reflection
to an optical detector aligned relative to said sample surface at
an alignment angle that is substantially equal to an angle of
reflection of the produced specular reflection such that the
directed specular reflection does not saturate the optical
detector; and the optical detector captures the specular reflection
from the sample surface and generates image data using essentially
only the specular reflection to generate image data of the sample
surface.
35. The system of claim 34, further comprising an image processor
that: analyzes said image data of the sample surface to determine
if said image data includes a fingerprint; and generates image data
of the fingerprint responsive to a determination that said analyzed
image data includes a fingerprint.
36. The system of claim 35, wherein said image processor analyzes
said image data of the sample surface to determine if said image
data includes a fingerprint by performing slope detection.
37. The system of claim 34, further comprising: at least one
scanner mechanically coupled to said optical detector for scanning
said optical detector across a plurality of regions of interest on
said sample surface, where said scanner is configured to maintain
the critical alignment angle during scanning.
38. The system of claim 34, wherein the discriminator includes an
optical arrangement coupled to the optical detector and where the
optical arrangement has a numerical aperture of zero.
39. The system of claim 34, wherein the numerical apertures of the
light source and the optical detector are substantially equal and
opposite.
40. The system of claim 34, wherein the specular reflection
discriminator includes a partial reflector that is arranged to:
direct a portion of illumination from said light source towards the
sample surface in a direction perpendicular to the sample surface;
and direct a portion of specular reflection from the sample surface
into the optical detector, which is arranged to detect light coming
in a perpendicular direction from the sample surface.
41. The system of claim 1, wherein said first light source
comprises a broadband light source.
42. The system of claim 1, wherein the first light source provides
a collimated beam of light.
43. The system of claim 5, wherein said collimated beam comprises a
narrowband beam.
44. The system of claim 1, wherein said first light source
comprises a narrowband light source including an ultraviolet (UV)
wavelength.
45. The system of claim 1, wherein said first light source
comprises: a broadband light source; and a spectral filter in
optical communication with the broadband light source.
46. The system of claim 1, wherein said first light source is a
laser operating at a wavelength of less than 600 nm.
47. The system of claim 5, wherein the collimated beam is an
infra-red (IR) beam including at least one of a wavelength at 3.42
.mu.m, 5.71 .mu.m, 6.9 .mu.m, or 8.8 .mu.m.
48. The system of claim 1, wherein the first light source is a
plurality of parallel aligned fluorescent tubes arranged to
collimated light as well as non-collimated light.
49. The system of claim 1, wherein said optical detector includes
an optical arrangement that directs and focuses incoming light onto
a detector portion, and where a numerical aperture of said optical
arrangement is zero.
50. The system of claim 1, further comprising: a second light
source that illuminates the sample surface such that the same
surface produces specular reflection; and a third light source that
illuminates the sample surface such that the sample surface
produces specular reflection; wherein the sample surface is thermal
printer dye film; and wherein a wavelength band of at least one
light source substantially matches an absorption spectrum of said
dye film.
51. The system of claim 1, wherein the sample surface is glossy
paper.
52. The method of claim 18, wherein said first light source
comprises a broadband light source.
53. The method of claim 18, wherein said first light source
comprises a broadband light source.
54. The method of claim 22, wherein providing a collimated beam of
light includes providing a narrowband beam.
55. The method of claim 18, wherein said illuminating including
providing narrowband light in an ultraviolet (UV) wavelength.
56. The method of claim 18, wherein said illuminating including
providing broadband light; and spectrally filtering said broadband
light such that said sample surface is illuminated with spectrally
filtered light.
57. The method of claim 18, wherein said illuminating including
illuminating the sample surface with a laser operating at a
wavelength of less than 600 nm.
58. The method of claim 18, wherein said illuminating including
illuminating the sample surface with an infra-red (IR) beam
including at least one of a wavelength at 3.42 .mu.m, 5.71 .mu.m,
6.9 .mu.m, or 8.8 .mu.m.
59. The method of claim 18, wherein said arranging further ding
setting a numerical aperture of said optical detector to zero.
60. A method of detecting latent fingerprints using specular
reflection, comprising: arranging a first light source such that it
illuminates a sample surface so that the sample surface produces
specular reflection; arranging an optical detector at a critical
alignment angle relative to the first light source such that the
optical detector captures the specular reflection from the sample
surface and generates image data using essentially only the
specular reflection to generate image data of the sample surface;
analyzing said generated image data of the sample surface to
determine if said generated image data includes an image of a
fingerprint; and producing image data of the fingerprint responsive
to a determination that said analyzed image data includes an image
of a fingerprint.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. Application No.
13/049,351 filed Mar. 16, 2011 and due to issue May 7, 2013 as U.S.
Pat. No. 8,437,517, which claims the benefit of U.S. Provisional
Application No. 61/409,753 filed Nov. 3, 2010, which are both
herein incorporated by reference in their respective entirety.
FIELD
[0003] Disclosed embodiments relate to non-contact automatic
optical detection of latent fingerprints.
BACKGROUND
[0004] Latent prints are invisible fingerprint impressions left on
solid surfaces following surface contact caused by the perspiration
on the ridges of an individual's skin on their fingers coming in
contact with a surface and leaving perspiration behind, making an
invisible impression on it, Perspiration is known to contain water,
salt, amino acids, and oils, which allows impressions to be made.
The natural oils of the body preserve the fingerprint, which is
utterly distinct so that no two humans have the same
fingerprints.
[0005] Conventional methods for extracting fingerprints usually
involve adding chemicals or powders to the print. Such conventional
methods can present an immediate dilemma in that they force the
investigator to make a decision as to whether to dust for prints
versus swabbing for DNA evidence.
[0006] Automatic non-contact latent fingerprint detection systems
are also known that avoid the need to add chemicals or powders that
can disturb the surface chemicals of the fingerprint. Such systems
generally include a single light source, utilize only diffuse
reflectance (reject specular reflection (glare)), and are generally
limited to fingerprinting the area of one's finger, or an area
about that size.
SUMMARY
[0007] Disclosed embodiments include non-contact automatic optical
fingerprint systems that include a critically aligned optical
sensor comprising a light source critical angle positioned relative
to a camera to utilize specular reflection from an irradiated
sample surface. In contrast, conventional optical fingerprint
systems reject specular reflection (glare) and process only diffuse
reflection. It has been discovered that fingerprint features can be
seen in images enabled by processing glare that cannot be seen in
images generated using conventional diffuse reflected light. When
the optical sensor is critical angle positioned and the camera
exposure time and gain settings are set so that the specular
reflections received do not saturate the camera's photosensor
array, the diffuse reflections from interrogated sample surfaces
will appear (relatively) very dim. In this arrangement, the diffuse
reflections may not be visible at all. The critically aligned
optical sensor and camera settings can therefore act as a filter
discriminating highly against diffuse reflections from scattering
surfaces therefore providing a "geometric filter" that essentially
only accepts glare (i.e., .gtoreq.98% of the photons processed by
the camera are from the glare).
[0008] Discrimination for glare can be further enhanced when the
numerical aperture (NA) of the lens is=0 so that NA.sub.CAMERA=0.
As known in optics, the NA of an optical system is a dimensionless
number that characterizes the range of angles over which an optical
system can accept light (for a light collector, e.g., camera) or
emit light (for a light source). Disclosed embodiments also
recognize that having the light source and the camera have equal
and opposite NAs that are aligned together provides even more
highly discriminating results for glare. As used herein, the light
source and the camera having "substantially equal and opposite NAs"
refers to the respective NAs being within 10%, and typically within
5%, of a magnitude of one another, and being opposite in sign.
Disclosed fingerprint systems comprise a critically aligned optical
sensor that includes a first light source for interrogating a first
sample surface within a region of interest with a collimated beam
that can provide collimated photons that uniformly extend over the
first sample surface. As used herein, "uniformly extended" refers
to an irradiated intensity of the collimated beam that varies
.gtoreq..+-.20% across the area of the first sample surface. The
camera comprises a lens and a photod.etector array optically
coupled to the lens that has a camera field of view
(FOV.sub.CAMERA), wherein the FOV.sub.CAMERA is sufficiently large
to image at least substantially an entire area of the first sample
surface.
[0009] A computer or processor having associated memory that
includes reference fingerprint templates is coupled to receive a
digitized form of the image data from the camera. The computer or
processor includes data processing software for (i) comparing the
digitized form of the image data to the reference fingerprint
templates to determine whether the image data includes at least one
fingerprint, and (ii) for generating a fingerprint image if a
fingerprint is determined to be present.
[0010] Automatic fingerprint scanning systems are also disclosed.
Disclosed automatic fingerprint scanning systems comprise a
disclosed automatic optical fingerprint system together with a
scanner mechanically coupled to the optical sensor for scanning the
optical sensor across a plurality of different surface portions
within the region of interest, and optionally also a wireless
transmitter for transmitting data representing fingerprints
detected by the system to at least one remote site.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1A is a depiction of an example fingerprint system
comprising a critically aligned optical sensor including a camera
and a light source, where the light source provides a uniformly
extended collimated beam for interrogating sample surfaces
including a first sample surface within a region of interest, and a
computer or processor for data processing the glare received by the
camera, according to an example embodiment.
[0012] FIG. 1B illustrates a depiction of NA matching along with NA
alignment between a light source and a camera for the case of
cone-shaped emission and collection NAs, according to an example
embodiment.
[0013] FIG. 1C is a depiction of an example fingerprint system
comprising a critically aligned optical sensor including a camera
and a light source, where the light source provides a uniformly
extended collimated beam for interrogating sample surfaces
including a first sample surface within a region of interest, along
with other non-critically aligned light sources, and a computer or
processor for data processing the glare received by the camera,
according to an example embodiment.
[0014] FIG. 2 is a depiction of an example automatic fingerprint
scanning system comprising the example fingerprint system shown in
FIG. 1A together with at least one scanner mechanically coupled to
the optical sensor for scanning the optical sensor across a
plurality of different surface portions within the region of
interest, and a wireless transmitter for transmitting data
representing fingerprints detected by the system to at least one
remote site according to an example embodiment.
[0015] FIGS. 3A-C each depict different arrangements shown unfolded
around the sample axis that can satisfy the condition that the
entire sample surface be uniformly illuminated using equal and
opposite light source and camera NAs, with the camera imaging the
entire sample, according to example embodiments.
[0016] FIG. 4 is a plot transmission % from the UV to the Long Wave
Infra-Red (LWIR) for fingerprint oil evidencing significantly
enhanced absorption within the UV and the long wave infrared (LWIR)
as compared to an absorption of fingerprint oil in a conventional
wavelength range from visible light range to 3 .mu.m. The UV and
LWIR regions can be used to image fingerprints exploiting
heightened body oil absorption that increases the optical contrast
of the fingerprint oils against sample surfaces,
[0017] FIG. 5A and B show signal to noise ratio (SNR) data from
plots of fingerprint scans showing a ridge profile evidencing about
a 3.times. improvement in SNR using slope detection (FIG. 5A) as
compared to amplitude detection (FIG. 5B), according to an example
embodiment.
[0018] FIG. 5C provides spectral plots of the absorption for
fingerprint oil, fingerprint oil on copy paper, and clean copy
paper, showing an absorption peak at 2925 cm.sup.-1 which
corresponds to a wavelength of 3.418 .mu.m that can be used to
define sloped portions of this peak for slope detection, according
to an example embodiment.
[0019] FIG. 6 is a scanned image of a fingerprint acquired by an
example disclosed fingerprint system configured to be highly
discriminating toward specular reflection from a sample surface
including a critically aligned optical sensor having the light
source and camera have equal and opposite NAs, according to an
example embodiment.
DETAILED DESCRIPTION
[0020] Disclosed embodiments are described with reference to the
attached figures, wherein like reference numerals, are used
throughout the figures to designate similar or equivalent elements.
The figures are not drawn to scale and they are provided merely to
illustrate aspects disclosed herein. Several disclosed aspects are
described below with reference to example applications for
illustration. It should be understood that numerous specific
details, relationships, and methods are set forth to provide a full
understanding of the embodiments disclosed herein. One having
ordinary skill in the relevant art, however, will readily recognize
that the disclosed embodiments can be practiced without one or more
of the specific details or with other methods. In other instances,
well-known structures or operations are not shown in detail to
avoid obscuring aspects disclosed herein. Disclosed embodiments are
not limited by the illustrated ordering of acts or events, as some
acts may occur in different orders and/or concurrently with other
acts or events. Furthermore, not all illustrated acts or events are
required to implement a methodology in accordance with this
Disclosure.
[0021] Disclosed embodiments recognize reflections from a sample
surface includes two distinct kinds of reflection, specular
reflection (glare) and diffuse reflection, and disclosed
embodiments utilize at least the specular reflection component to
optically obtain fingerprints from the sample surface. As known in
the art, for specular reflection imaging the angles of incidence
and reflection are set equal, while for the diffuse reflection case
the reflected intensity may approximately have an effectively
uniform distribution over all directions in a hemisphere. Most
surfaces exhibit both types of reflection. Disclosed embodiments
are in contrast to conventional optical imaging systems including
conventional fingerprint systems that are configured to reject
specular reflection and process only diffuse reflection.
[0022] FIG. 1A is a depiction of an example fingerprint system 100
comprising a critically aligned optical sensor 110 including a
camera 120 comprising a lens 121 and a light source 101, where the
light source 101 provides a uniformly extended collimated beam for
interrogating sample surfaces 107 including a first sample surface
107(a) within a region of interest, and a computer or processor 130
for data processing the glare received by the camera 120, according
to an example embodiment. The collimated beam provided by light
source 101 has a spatial extent .gtoreq.FOV.sub.CAMERA. In one
specific embodiment the interrogation area provided by the
collimated beam is 50 .mu.m.times.50 .mu.m, and the FOV.sub.CAMERA
is .ltoreq.50 .mu.m.times.50 .mu.m.
[0023] As depicted in FIG. 19, the light source 101 and the camera
120 can have substantially equal and opposite NAs that are aligned
together to provide highly discriminating results for specular
reflection. One method for NA alignment is to use the apparatus
itself with a good sample and a set of neutral density optical
filters. Adjustment can be made using bright light until the best
response is obtained. A filter can be added to dim the illuminating
light and the best performance can be obtained again. Another
filter is then added, etc. For instance, if the two NAs are
conically shaped and opposite in sign they can be stacked almost
perfectly one on top of the other as shown in FIG. 1B.
[0024] Optically aligning the light source which provides a
uniformly extended collimated beam over the sample surface and
camera NAs then uniformly filling the camera NA makes the glare
field uniform across the full FOV.sub.CAMERA. The inventor has
recognized that use of a uniform glare field maximizes the dynamic
range of the imaging system, since non-uniformities in the
illumination field serve as a noise floor. A wide dynamic range
with good SNR desirably provides high contrast.
[0025] The light source 101 can comprise a broadband light source.
For example, the broadband light source can comprise a fluorescent
light source, such as a plurality of parallel aligned (i.e.,
stacked) fluorescent tubes. In another embodiment the collimated
beam provided by light source 101 comprises a narrowband beam
defined herein as <1 nm Full Width Half Max (FWHM).
[0026] A narrowband beam can be realized by a narrowband light
source (e.g., laser), or a broadband light source (see below) and a
spectrometer. In some embodiments the collimated beam is at one or
more UV wavelengths or one or more LWIR wavelengths that each
correspond to significantly enhanced absorption for fingerprint
oil, defined herein to be present at wavelengths where absorption
increases by at least 6.5% as compared to the absorption in a
conventional range from visible light range to 3 .mu.m. Increased
absorption has been found to provide an improvement in contrast vs.
the sample surface that provides the background in the image. See
FIG. 4 described below that evidences some UV and IR wavelengths
that provide significantly enhanced absorption. In one embodiment
the UV wavelength is between 100 and 300 nm, and the LWIR
wavelength can be at 3.42 .mu.m, 5.71 .mu.m, 6.9 .mu.m, or 8.8
.mu.m, which all represent significantly enhanced absorption
wavelengths for fingerprint oil.
[0027] Light source 101 can provide either non-polarized or
polarized light. Polarized light may be of advantage when the
sample surface 107 is held at an extreme angle, something analogous
to Brewster's angle (polarization angle). This angle is defined by
the surface material and surface roughness/texture.
[0028] Camera 120 comprises lens 121. Camera 120 can comprise a
variety of different camera types, such a commercial off-the shelf
(COTS) CCD/CMOS digital camera. The lens magnification, camera
sensor size, and pixel count can be designed to produce a minimum
resolution that is compatible with existing requirements. For
example, 500 DPI is the current FBI standard.
[0029] In one embodiment, the camera 120 is sensitive to radiation
including UV radiation in the range from about 100 nm to 300 nm.
This UV imaging capability can be provided by adding a layer of UV
sensitizer material to the sensor associated with the camera 120.
One such material has the commercial name Lumigen (Lumigen, Inc. (a
Beckman Coulter Company Southfield, Mich.). This layer absorbs UV
light and up converts it to a wavelength that photodetectors such
as CCD photodetectors can efficiently detect.
[0030] In one embodiment the lens 121 is selected to provide
NA.sub.CAMERA=0. For example, a double telecentric lens can provide
NA.sub.CAMERA=0 which results in the FOV.sub.CAMERA area of the
lens 121. The camera 120 is coupled to a computer or processor 130
via a frame grabber 125. As known in the art, a frame grabber 125
is an electronic device that captures individual, digital still
frames from an analog video signal or a digital video stream. A
computer or processor 130 includes a controller 131 that can
dynamically control the intensity of light provided by light source
101, and at least one memory 132. The intensity of light source 101
can be set to approach but not reach saturation of the
photodetectors in camera 120.
[0031] The standoff distance during imaging operations is generally
set by the optics of the camera 120. A typical standoff distance
between the optical sensor 110 and sample surface 107 is about 12
inches, but can be at other distances, such as 4 to 20 inches, for
example.
[0032] Light source 101 can be dynamically angle tuned to maintain
critical angle alignment shown as at an angle e with respect to the
camera 120. For example, a movable laser illuminated mirror can be
used to adjust the critical angle lighting condition to produce the
best results. In one embodiment both the light source 101 and the
camera 120 are secured to a fixture to ensure maintaining critical
angle alignment.
[0033] System 100 includes at least one detection filter, shown in
FIG. 1 as Fourier filter 140 and a Rugate notch filter 142. Notch
filter 142 is included for embodiments including a laser (not
shown), such as for critical alignment purposes, or as a diffuse
scatter light source. Fourier filter 140 functions to match
fingerprint features as well as suppress background features, such
as grains in the paper in the case of a paper sample surface, such
as for Raman imaging.
[0034] Disclosed embodiments recognize in order to detect
fingerprints that may be on a wide variety of different surfaces,
such as tools (e.g., wrenches), guns, phones/PDAs and CD cases,
multiple different light sources may be helpful. Each light source
can provides a different kind of light, such as white light and
narrowband light, such as in the UV or IR. Thus light from each
light source will scatter off the interrogated sample surface
differently. The light sources are generally used one at a time,
with each of the light sources producing a different effect on the
latent fingerprint. There is a high probability that every latent
fingerprint on a given sample surface will respond to one or more
of these light sources and become visible to the camera 120
recording the results.
[0035] FIG. 1C is a depiction of an example fingerprint system 160
comprising a critically aligned optical sensor including a camera
and a light source 101, where the light source 101 provides a
uniformly extended collimated beam for interrogating sample
surfaces including a first sample surface within a region of
interest, along with other non-critically aligned light sources 102
and 103, according to an example embodiment. Diffuse scatter from
non-critically aligned light sources 102 and 103 allows the
background to be characterized so that the background can be
subtracted out from the image data, such as text on paper in the
case of certain paper-based samples.
[0036] System 160 includes a computer or processor 130 for data
processing the glare and diffuse refection data received by the
camera 120. In one embodiment light source 102 provides
non-critical angled incandescent light, and light source 103
comprising a non-critical aligned laser. Light sources 101-103 each
can include dynamic intensity adjustment. In typical system
operation, the respective light sources 101-103 individually
illuminate the sample surface 107 for separate interrogations.
[0037] Light from laser 103 can reveal latent fingerprints that the
other two light sources 101 and 102 cannot. The laser 103 is used
to excite the sample surface in a very specific (narrow) spectral
band and time domain, such as at 532 nm. Spectral/temporal
filtering methods can be used to extract the desired information
from the laser illumination of the sample surface. The type of
camera used to record the results depends on the type of optical
filtering required to extract the data. For instance, if Raman
imaging is used the camera exposure time will be approximately the
same value as the length of the laser pulse. This technique can
reduce background noise due to fluorescence.
[0038] FIG. 2 is a depiction of an automatic fingerprint scanning
system 200 comprising the example fingerprint system 100 shown in
FIG. 1A together with at least one scanner 220 shown as a robotic
arm 220 mechanically coupled to the system 100 for scanning the
optical sensor 110 across a plurality of different surface portions
within the region of interest, and a wireless transmitter 230
including an antenna 231 for transmitting data representing
fingerprints detected by the system 100 to at least one remote
site.
[0039] System 200 is shown also including a powered cart 245, such
as a battery powered cart. Robotic arm 220 is affixed to the
powered cart 245. System 200 also includes a remote sensing device
260 for generating a region image (e.g., 3D) across a region of
interest, such as a room. The region image sensed by sensing device
260 is provided to computer or processor 130 and can be used to
guide movements of the robot arm 220 for its movement to image
across the region of interest, such as within a room.
[0040] Results can be stored in a local memory 132 associated with
the computer or processor 130, and can be wirelessly transmitted by
a wireless transmitter 230, such as in an established encoded
protocol form, to one or more remote locations. In one embodiment
the remote sensing device 260 comprises a Light Detection and
Ranging (LIDAR) device. LIDAR may also be referred to as LADAR in
military contexts, and is an optical remote sensing technology that
can measure the distance to, or other properties of a target by
illuminating the target with light, often using pulses from a laser
Like the similar radar technology, which uses radio waves, the
range to an object is determined by measuring the time delay
between transmission of a pulse and detection of the reflected
signal.
[0041] FIGS. 3A-C each depict different conditions shown unfolded
around the sample axis that can satisfy the condition that the
entire sample be uniformly illuminated using equal and opposite
light source and NA.sub.CAMERA, with the camera imaging the entire
sample being irradiated, according to example embodiments. FIG. 3A
shows the case of NA.sub.CAMERA>0. Although the camera lens for
NA.sub.CAMERA>0 is realizable, there may be difficulty obtaining
a light source the provides an equal and opposite NA. FIG. 3B shows
the case of NA.sub.CAMERA=0. In this case the camera lens can be a
double telecentric lens. An example of a light source that provides
a zero NA is a highly collimated light source. FIG. 3C shows the
case of NA.sub.CAMERA<0. Although obtaining a light source that
provides an equal and opposite NA is reasonable, the camera lens
for NA.sub.CAMERA<0 may be difficult to realize.
[0042] FIG. 4 is a plot 400 of UV to NIR transmission for
fingerprint oil evidencing significantly enhanced absorption within
the UV and the LWIR as compared to an absorption of fingerprint oil
in a conventional visible light range (i.e. 500 nm) to 3 .mu.m. The
UV and LWIR can be used to image fingerprints exploiting heightened
absorption to increase the optical contrast of the fingerprint oils
against a sample surface, such as paper. In the UV, 80%
transmission is at about 300 nm (0.3 .mu.m), with the transmission
decreasing (and absorption increasing due to oil absorption.) to
about 40% at 180 nm, with even lower transmission down to below 100
nm (not shown). Several IR absorption peaks are shown.
Significantly enhanced absorption can thus be obtained at UV
wavelength between 100 and 300 nm, and LWIR wavelengths at 3.42
.mu.m, 5.71 .mu.m, 6.9 .mu.m, and 8.8 .mu.m.
[0043] FIGS. 5A and 5B show signal to noise ratio (SNR) data from
plots of fingerprint scans showing a ridge profile evidencing about
a 3.times. improvement in SNR using slope detection (FIG. 5A) as
compared to amplitude detection (FIG. 5B), according to an example
embodiment. The best possible detection would be an idealized
"Matched Detection" where an exact replica of the feature being
sought is compared with the collected signal. Amplitude Detection
looks only for an amplitude change, while slope detection looks for
a part of the feature being detected.
[0044] FIG. 5C is provides spectral plots of the absorption for
fingerprint oil, fingerprint oil on copy paper, and clean copy
paper, showing an absorption peak at 3.418 .mu.m (2925 cm.sup.-1
which corresponds to a wavelength of 3.418 .mu.m) that can be used
to define sloped portions of this peak for slope detection,
according to an example embodiment. In the case of slope detection
the feature being detected can be the sharp slopes on each side of
the peak at 2925 cm.sup.-1.
[0045] FIG. 6 is a scanned image of a fingerprint acquired by an
example disclosed fingerprint system configured to be highly
discriminating toward specular reflection from a sample surface
including a critically aligned optical sensor having the light
source and camera have equal and opposite NAs, according to an
example embodiment. The camera used was a 6M Pixel CCD, the lens
was a double telecentric lens, and the light source was a set of
fluorescent light bulbs held side-by-side closely to each other in
a parallel fashion. The light source, sample and camera plus lens
were set up to satisfy the critical angle condition.
[0046] Disclosed systems, such as systems 100, 160 and 200
described above, automatically generate fingerprint image data from
sample surfaces within an interrogated region, and look for
fingerprints in the fingerprint image data obtained. When a
fingerprint is detected the system can capture the fingerprint,
digitize it into a digital storage format (e.g., using an analog to
digital converter), and can store it in memory, such as the
internal memory 132 of computer 130. Computer 130 can comprise a
laptop computer, personal digital assistants (PDAs) such as an
IPHONE.TM., BLACKBERRY.TM., or other suitable portable computing
device. Software on the portable computing device can then encode
the stored fingerprints into a format usable by the existing AFIS
(automated fingerprint identification system), integrated AFIS
(IAFIS) or other fingerprint processing systems. In one
application, disclosed systems can be used to help investigators
locate latent fingerprints at a crime scene.
[0047] in one embodiment an internal matching algorithm helps the
investigator(s) differentiate fingerprints of interest from those
expected to see at the scene such as family members, co-workers,
etc. Data from expected fingerprints can be loaded into the system
and stored as reference fingerprint templates in local memory 132.
Having the ability to immediately organize prints into
classification groups can significantly benefit the investigators,
helping them better focus their efforts.
[0048] Being automatic and computer controlled, disclosed
embodiments reduce operator workload and minimize the potential for
human error. Disclosed embodiments can also give the field
investigator(s) the ability to immediately know that the data
he/she gathers is valid and usable. Human error includes
overlooking or possibly damaging critical evidence as well as
incorrectly capturing fingerprint evidence. As described above,
fingerprint data can be wireless transmitted to one or more remote
locations using a wireless transmitter.
[0049] Disclosed fingerprint systems can be built into other
systems to add security features to such systems, such as to reduce
theft or unauthorized access. For example, credit or debit card
processing systems can include disclosed fingerprint systems to
provide a fingerprint record associated with each transaction that
is triggered upon insertion of the card. Such fingerprint records
can be used to identify the individual using the card, and if a
fingerprint database is available, a fingerprint database can be
used to determine whether account access will be provided.
[0050] While various disclosed embodiments have been described
above, it should be understood that they have been presented by way
of example only, and not as a limitation. Numerous changes to the
disclosed embodiments can be made in accordance with the Disclosure
herein without departing from the spirit or scope of this
Disclosure. Thus, the breadth and scope of this Disclosure should
not be limited by any of the above-described embodiments. Rather,
the scope of this Disclosure should be defined in accordance with
the following claims and their equivalents.
[0051] Although disclosed embodiments have been illustrated and
described with respect to one or more implementations, equivalent
alterations and modifications will occur to others skilled in the
art upon the reading and understanding of this specification and
the annexed drawings. While a particular feature may have been
disclosed with respect to only one of several implementations, such
a feature may be combined with one or more other features of the
other implementations as may be desired and advantageous for any
given or particular application.
[0052] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting to
this Disclosure. As used herein, the singular forms "a," "an," and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. Furthermore, to the extent
that the terms "including," "includes," "having," "has," "with," or
variants thereof are used in either the detailed description and/or
the claims, such terms are intended to be inclusive in a manner
similar to the term "comprising."
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