U.S. patent application number 12/763778 was filed with the patent office on 2010-11-25 for raman spectrometry assembly.
This patent application is currently assigned to Ahura Scientific Inc.. Invention is credited to Masud Azimi, Kevin J. Knopp, Steve Mclaughlin.
Application Number | 20100296085 12/763778 |
Document ID | / |
Family ID | 40337769 |
Filed Date | 2010-11-25 |
United States Patent
Application |
20100296085 |
Kind Code |
A1 |
Azimi; Masud ; et
al. |
November 25, 2010 |
RAMAN SPECTROMETRY ASSEMBLY
Abstract
A Raman spectrometry assembly includes a Raman spectrometer
having a laser light source and a Raman signal analyzer, an
interface module comprising a housing which is connectable to and
disconnectable from the spectrometer, and a fiber optic assembly
which is connectable to and disconnectable from the interface
module, the fiber optic assembly including optical fibers and a
probe head at a distal end thereof for disposition adjacent a
specimen to be tested, the optical fibers extending from the probe
head and adapted to extend to the interface module.
Inventors: |
Azimi; Masud; (Belmont,
MA) ; Knopp; Kevin J.; (Newburyport, MA) ;
Mclaughlin; Steve; (Andover, MA) |
Correspondence
Address: |
FISH & RICHARDSON PC
P.O. BOX 1022
MINNEAPOLIS
MN
55440-1022
US
|
Assignee: |
Ahura Scientific Inc.
|
Family ID: |
40337769 |
Appl. No.: |
12/763778 |
Filed: |
April 20, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11894887 |
Aug 22, 2007 |
7701571 |
|
|
12763778 |
|
|
|
|
60839188 |
Aug 22, 2006 |
|
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Current U.S.
Class: |
356/301 |
Current CPC
Class: |
G01J 3/0227 20130101;
G01N 2021/656 20130101; G01J 3/0218 20130101; G01J 3/02 20130101;
G01J 3/0291 20130101; G01J 3/024 20130101; G01N 2201/08 20130101;
G01J 3/44 20130101; G01J 3/021 20130101; G01N 21/65 20130101 |
Class at
Publication: |
356/301 |
International
Class: |
G01J 3/44 20060101
G01J003/44; G01N 21/65 20060101 G01N021/65 |
Claims
1. A Raman spectrometry assembly comprising: a Raman spectrometer
comprising a laser light source and a Raman signal analyzer; an
interface module comprising a housing which is connectable to and
disconnectable from said spectrometer; and a fiber optic assembly
which is connected to and disconnectable from said interface
module, said fiber optic assembly comprising a probe head portion
at a distal end thereof for disposition adjacent a specimen to be
tested, and optical fibers extending from said probe head portion
and adapted to extend to said interface module.
2-26. (canceled)
Description
REFERENCE TO PENDING PRIOR PATENT APPLICATION
[0001] This patent application claims the benefit of U.S.
Provisional Patent Application Ser. No. 60/839,188 filed Aug. 22,
2006, in the names of Masud Azimi, Kevin Knopp and Steve
Mclaughlin.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to apparatus for identifying and
characterizing substances using Raman spectroscopy, which provides
a non-contact and non-invasive technique for investigation and
analysis of chemical substances.
[0004] 2. Description of the Prior Art
[0005] Raman spectroscopy is widely used in the scientific,
commercial and public safety areas.
[0006] Technological advances are making it possible to increase
the range of applications using Raman spectroscopy, through
reductions in costs and size of the equipment. Portable units have
become available for field uses, such as on-site identification of
potentially hazardous materials.
[0007] In applications of Raman spectroscopy, it is generally
desirable to bring an optical probe to a position adjacent a
specimen. This can be a problem in view of the potentially
hazardous materials which are to be analyzed, including explosives,
chemical agents, toxic industrial chemicals, and the like. In some
applications, it is required, for safety reasons, that delivery of
laser light to a specimen under test, and a collection of Raman
signal from the specimen, be done at a location remote from the
Raman spectrometer hardware. Optical fiber, which can serve as a
conduit for laser light and Raman signal light, is a good medium
for achieving this. However, there are some problems in the use of
optical fibers and probes for Raman spectroscopy.
[0008] Firstly, the distal end of the probe can become contaminated
during data collection and it is often desirable, and at times
necessary, to replace the probe head, which is very costly, if it
can be done at all. Accordingly, there is a need for a relatively
inexpensive optical fiber assembly, including optical fiber and a
probe head, which can be disconnected from the spectrometer and
replaced with another optical fiber assembly.
[0009] Secondly, propagation of a high power laser light within an
optical fiber generates unwanted Raman signal from the optical
fiber material itself which adds to the Raman signal collected from
a specimen and, in many cases, is difficult to distinguish from the
specimen signal and difficult to subtract from the Raman signal
generated from the specimen under test.
[0010] Accordingly, there is a further need for means for
preventing Raman signals generated by the material of an excitation
fiber of an optical fiber assembly from reaching the specimen under
test, such that only the excitation laser signal reaches the
specimen and the Raman signals received from the specimen and
conducted to a spectrometer by way of a collection fiber of the
optical fiber assembly are from the specimen only and not from the
excitation fiber.
[0011] Thirdly, the laser light exiting the distal end of the
excitation fiber diverges immediately and does so until the
excitation light reaches the specimen under test. Thus, the portion
of the excitation light which reaches the specimen reduces,
increasingly, as the distance between the excitation fiber and the
specimen increases.
[0012] There is accordingly a still further need for means to focus
the light from the excitation fiber onto a small area of the
specimen. Similarly, Raman signals reflected off the specimen
diverge outwardly from the specimen with only a small portion of
the reflected light reaching an end of a collection fiber.
Accordingly, there is also a need for means to focus Raman light
from a specimen onto the small area of an end of a collection
fiber.
SUMMARY OF THE INVENTION
[0013] Accordingly, an object of the invention is to provide a
Raman Spectrometry Assembly in which a fiber optic assembly,
including a probe head and optical fibers, is detachable from a
Raman spectrometer and readily replaced with the same or another
fiber optic assembly.
[0014] A further object of the invention is to provide such a fiber
optic assembly in which the laser light from the spectrometer
carried by the excitation fiber does not interfere with Raman
signal generated by the material of the excitation fiber, such that
substantially only the excitation laser impinges upon the specimen
and the Raman signal reflected therefrom includes only Raman signal
from the specimen.
[0015] A still further object of the invention is to provide such a
fiber optic assembly in which laser light emanating from the
excitation fiber distal end is focused on a small portion of the
sample under test, and diverging Raman signal light reflected off
the sample is focused so as to enter an end of the collection fiber
for transmission to the Raman signal analyzer.
[0016] With the above and other objects in view, a feature of the
present invention is the provision of a Raman spectrometry
assembly, the assembly including a Raman spectrometer comprising a
laser light source and a Raman signal analyzer, an interface module
comprising a housing which is attachable to and detachable from the
spectrometer, and a fiber optic assembly which is attachable to and
detachable from the interface module, the fiber optic assembly
comprising a probe head portion at a distal end thereof for
disposition adjacent a specimen to be tested, and optical fibers
extending from the probe head and adapted to extend to the
interface module.
[0017] In accordance with a further feature of the invention, there
is provided a Raman spectrometer assembly, the assembly including a
Raman spectrometer comprising a laser light source and a Raman
signal analyzer, a housing for releasable connection to the
spectrometer, and having first and second openings extending
through a wall thereof, first and second sleeves disposed in the
first and second openings, a fiber optic assembly comprising first
and second ferrules adapted for insertion into and withdrawal from
the sleeves, an elongated excitation fiber fixed to and extending
from the first ferrule and an elongated collection fiber fixed to
and extending from the second ferrule, distal ends of the fibers
being fixed in a probe head portion of the fiber optic assembly,
and light manipulating components disposed in the housing and
adapted to guide laser light to the first ferrule and thence to the
excitation fiber, and to guide Raman signature light from a
specimen under test to the second ferrule and thence to the Raman
signal analyzer, wherein the ferrules are readily withdrawable from
the sleeves and replaceable therein or by other ferrules.
[0018] In accordance with a still further feature of the invention,
there is provided a Raman spectrometry assembly, the assembly
including a Raman spectrometer comprising a laser light source and
a Raman signal analyzer, an interface module adapted for connection
to and disconnection from the spectrometer, and having a first
opening extending through a wall thereof, light manipulating
components disposed in the interface module for directing a laser
beam emitted from the laser light source of the spectrometer toward
the first opening, a first focusing lens mounted in the interface
module and aligned with the first opening, and a first sleeve
disposed in the first opening. The spectrometer assembly further
includes a fiber optic assembly comprising a first ferrule adapted
for insertion into the first sleeve and adapted for removal
therefrom, the first ferrule being further adapted to reside in the
sleeve and therein to receive and transmit the laser light emitted
from the laser light source and the laser light directing
components to an excitation fiber proximal end fixed to the first
ferrule, an elongated excitation fiber extending from the proximal
end thereof fixed in the first ferrule to a distal end thereof
fixed in a portion of a probe head, a collection fiber extending
from the probe head to a second ferrule which is removably disposed
in a second sleeve disposed in a second opening in a wall of the
interface module. The interface module further comprises a second
focusing lens aligned with the second opening and adapted to pass
collection fiber light therethrough and toward a portion of the
light directing components to the Raman signal analyzer of the
spectrometer. The ferrules are removable from the sleeves, and the
sleeves are adapted to receive further ferrules of a configuration
substantially identical to the first ferrule and the second
ferrule, wherein the fiber optic assembly may readily be replaced
by another fiber optic assembly.
[0019] In accordance with a still further feature of the invention,
there is provided a Raman spectrometry assembly, the assembly
including a Raman spectrometer comprising a laser light source and
a Raman signal analyzer, an interface module adapted to pass laser
light therethrough and into a flexible excitation fiber connected
to the module, and adapted to pass Raman signal light from a
flexible collection fiber connected to the interface module
therethrough to the Raman signal analyzer, and a fiber optic
assembly comprising the excitation fiber and the collection fiber,
a flexible elongated protective shielding disposed around the
excitation fiber and the collection fiber, and a probe head at a
distal end thereof for disposition adjacent a sample to be tested,
the excitation and collection fibers being adapted to extend from
the probe head to the interface module, and a band pass filter at
the distal end of the excitation fiber to prevent passage of laser
light therethrough, but block passage of Raman signal light in the
excitation fiber derived from the excitation fiber, such that the
Raman signal light generated in the excitation fiber is prevented
from reaching the sample.
[0020] In accordance with a still further feature of the invention,
there is provided a Raman spectrometry assembly, the assembly
including a Raman spectrometer comprising a laser light source and
a Raman signal analyzer, an interface module comprising a housing
which is connectable to and disconnectable from the spectrometer,
and a fiber optic assembly which is connectable to and
disconnectable from the interface module, the fiber optic assembly
comprising a probe head portion at a distal end thereof for
disposition adjacent a specimen to be tested, and optical fibers
extending from the probe head and adapted to extend to the
interface module, the optical fibers including an excitation fiber
for transmitting laser light from the interface module to a
specimen under test, and a collection fiber for transmitting Raman
signal light from the specimen to the interface module, and a lens
aligned distally of the distal ends of the optical fibers, the lens
being adapted to intercept diverging laser light emanating from the
excitation fiber and focus the laser light on a reduced area of the
specimen, and to intercept a Raman signal light reflected from the
specimen and focus the Raman signal light onto the distal end of
the collection fiber.
[0021] In accordance with a still further feature of the invention,
there is provided a method for obtaining an analysis of a specimen,
the method comprising the steps of providing a Raman spectrometer
having a laser light source and a Raman signal analyzer, providing
an interface module which is adapted for attachment to the
spectrometer, the module having therein light manipulating devices
for directing laser light and Raman signal light for effecting
excitation of the specimen and collection and directing of Raman
signal light to the Raman signal analyzer, and providing a fiber
optic assembly comprising an excitation fiber, a collection fiber,
and a probe head, attaching the interface module to the
spectrometer, attaching the fiber optic assembly to the interface
module, placing the probe head adjacent the specimen, and
energizing the laser light source, whereby to cause laser light to
pass from the spectrometer to the interface module and therein to
be directed by the light manipulating devices to the excitation
fiber and the probe head and onto the specimen, and thence to pass
Raman signal light back through the collection fiber to the
interface module wherein the manipulating devices direct the Raman
signal light to the spectrometer Raman light analyzer.
[0022] In accordance with a still further feature of the invention,
there is provided a Raman spectrometry assembly including a Raman
spectrometer comprising a laser light source and a Raman signal
analyzer, an interface module, and a fiber optic assembly
connectable to and disconnectable from the interface module. The
fiber optic assembly includes a probe head at a distal end thereof
for disposition adjacent a specimen to be tested, and optical
fibers extending from the probe head and adapted to extend to the
interface module. The optical fibers include an excitation fiber
for transmitting laser light from the interface module to a
specimen under test, and a collection fiber for transmitting Raman
signal light from the specimen to said interface module. The probe
head assembly includes first and second lenses aligned distally of
distal ends of the optical fibers, the first lens being adapted to
intercept diverging laser light emanating from the excitation fiber
and collimate the laser light, and the second lens being adapted to
intercept a Raman signal light reflected from the specimen and
focus the Raman signal light onto a distal end of the collection
fiber. The assembly further includes a band pass filter at the
distal end of the probe head and adapted to suppress Raman signal
generated by excitation fiber material and prevent such signal from
reaching the specimen, a reflector for redirecting filtered laser
light to a notch filter, wherein the notch filter is disposed in
the probe head and is adapted to transmit Raman signal light
emanating from the specimen and to block laser light reflected back
from the specimen from reaching the distal end of the collection
fiber, and a focusing lens disposed at the distal end of the probe
head, and adapted to focus the laser light on a reduced area of the
specimen, and further adapted to collect Raman signal light
generated and reflected from the sample and direct the reflected
light toward the distal end of the collection fiber. The assembly
still further includes a water-sealed enclosure made of a selected
one of metal, plastic, ceramic material and any chemically inert
material, to house components of the probe head assembly.
[0023] The above and other features of the invention, including
various novel details of construction and combinations of parts and
method steps, will now be more particularly described with
reference to the accompanying drawings and pointed out in the
claims. It will be understood that the particular devices and
method embodying the invention are shown by way of illustration
only and not as limitations of the invention. The principles and
features of this invention may be employed in various and numerous
embodiments without departing from the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Reference is made to the accompanying drawings in which are
shown illustrative embodiments of the invention from which its
novel features and advantages will be apparent.
[0025] In the drawings:
[0026] FIG. 1 is a schematic illustration of one form of
spectrometry assembly illustrative of an embodiment of the
invention;
[0027] FIG. 2 is a diagrammatic perspective view of a probe head
portion of a fiber optic assembly of FIG. 1;
[0028] FIG. 3 is a side elevational of the probe head portion of
FIG. 2;
[0029] FIG. 4 is a schematic illustration of a further portion of
the spectrometry assembly of FIG. 1; and
[0030] FIG. 5 is a schematic illustration of an alternative
embodiment of the probe head portion.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] Referring to FIG. 1, it will be seen that an illustrative
Raman spectroscopy assembly 20 includes a Raman spectrometer 22
including a laser light source LS and a light analyzer LA, as is
known in the art.
[0032] The assembly 20 further includes an interface module 24
comprising a housing 26 which is connectable to, and disconnectable
from, the spectrometer 22, and a fiber optic assembly 27 which is
connectable to, and disconnectable from, the interface module
24.
[0033] Mounted in the housing 26 are light manipulating devices 28
arranged so as to receive laser light 30 from the spectrometer 22
and direct the laser light, finely focused, to a first ferrule 32
of the fiber optic assembly 27. The light manipulating devices 28
are further arranged to receive Raman signal light and direct the
Raman signal light to the light analyzer LA of the spectrometer
22.
[0034] In the embodiment shown in FIG. 1, the particular light
manipulating devices 28 include a notch filter 34 which directs
laser light 30a toward a reflector 36 which directs the laser light
30b through a focusing lens 38 which focuses the light 30b onto a
fine point 40 on an inner end 42 of the ferrule 32.
[0035] In the fiber optic assembly 27, ferrule 32 has fixed thereto
a flexible excitation fiber 44 housed in a flexible protective
shielding 46. A distal end 48 of the laser fiber 44 is held in a
probe head 50.
[0036] The housing 26 is provided with two openings 52, 54
extending through a wall 56 thereof. Flanged sleeves 60, 58 are
fixed in openings 52, 54, respectively. The ferrule 32 of the fiber
optic assembly 27 is insertable into, and removable from the fixed
sleeve 60 of the housing 26. Similarly, a second ferrule 62 of the
fiber optic assembly 27 is insertable into, and removable from, the
fixed sleeve 58 of the housing 26.
[0037] The ferrule 62 has fixed thereto a collection fiber 64 which
is housed in the protective shielding 46, alongside the excitation
fiber 44. A distal end 66 of the collection fiber 64 is held in the
probe head 50.
[0038] A collimating lens 68 is aligned with the collection fiber
ferrule 62 and directs Raman signal light 70 through the notch
filter 34 and into the spectrometer 22, and in particular the light
analyzer LA.
[0039] While a specific arrangement of light manipulating devices
28 has been shown and described, it will be apparent that any
suitable arrangement of light manipulating devices could be used to
direct excitation laser light therethrough to the excitation fiber
and to receive Raman signal light by way of the collection fiber 64
and direct the Raman signal light to the light analyzer of the
spectrometer.
[0040] If, in use, any part of the fiber optic assembly 27, such as
the probe head 50 and/or protective shielding 46 becomes
contaminated, the ferrules 32, 62 may simply be "unplugged" from
the sleeves 60, 58, and replaced with another optical fiber
assembly, including a new probe head.
[0041] Both the fiber optic assembly, and the interface module can
be readily removed from the spectrometer. Any selected releasable
mechanical connection means can be used to attach the interface
module to the spectrometer, including snap-on, clamp-on, screw-on,
slide-and-lock-on arrangements, and the like.
[0042] Referring to FIGS. 2 and 3, it will be seen that the probe
head 50 may be shaped such that the geometry of the area of the
specimen S which is impacted can be predetermined. As shown in
FIGS. 1 and 2, an end facet 74 of the excitation fiber 44 can be at
an angle to the end 66 of the collection fiber 64.
[0043] As shown in FIGS. 2 and 3, the laser light 80 emitted from
the distal end 48 of the excitation fiber 44 is in a cone
configuration 82. Light reflected from the specimen S, that is, the
Raman signal light 70, travels back in a cone-shaped path 84
towards the distal end 66 of the collection fiber 64 and also
disperses outwardly from the path 84 and is lost. The amount of
collected Raman signal depends in large measure on the geometry of
the design of the probe head 50 and particularly on the cone
overlap area 86 effected by the two fibers 44, 64.
[0044] Referring to FIG. 4, it will be seen that the fiber optic
assembly may include a lens 72 disposed adjacent the probe head
distally of the distal ends of the excitation fiber 44 and the
collection fiber 64. Alternatively, the lens 72 may be used as a
separate component spaced from the probe head 50. Emerging from the
distal end 48 of the excitation fiber 44, the laser light 30
diverges. The lens 72 focuses the light 30 on a small area of the
specimen S under test. The reflected Raman signature light 70
similarly diverges, but is focused by the lens 72 onto the distal
end 66 of the collection fiber 64. Thus, relatively little Raman
signal is lost compared to the extensive loss realized in the
arrangement shown in FIG. 2.
[0045] Referring again to FIGS. 1-3, it will be seen that the
distal end 48 of the excitation fiber 44 may be covered with a thin
fiber band pass filter 90 which transmits only laser light and
rejects Raman signals which may be generated by the excitation
fiber. Thus, the Raman signal light 70 includes substantially only
Raman signal from the specimen S and essentially none from the
excitation fiber.
[0046] Referring to FIG. 5, it will be seen that in an alternative
embodiment, the fiber optic assembly probe head 50 includes first
and second lenses 72a and 72b aligned distally of distal ends of
the optical fibers 44, 64, the first 72a of the lenses being
adapted to intercept diverging laser light emanating from the
excitation fiber 44 and collimate the laser, and the second 72b of
the lenses being adapted to intercept a Raman signal light 70
reflected from the specimen S and focus the Raman signal light onto
the distal end 66 of the collection fiber 64. A band pass filter 92
is adapted to suppress Raman signal generated by the excitation
fiber material and prevent such signal from reaching the specimen.
A reflector 94 redirects the filtered laser light to a notch filter
96. The notch filter 96 is disposed in the probe head and is
adapted to transmit Raman signal light emanating from the specimen
and to block laser light reflected back from the specimen from
reaching the distal end 66 of the collection fiber 64. A focusing
lens 98 is disposed at the distal end of the probe head 50, the
focusing lens 98 being adapted to focus the laser light on a
reduced area of the specimen S, and further adapted to collect
Raman signal light generated and reflected from the sample, and
direct the reflected light toward the distal end 66 of the
collection fiber 64. A water-sealed enclosure 100, made of a
selected one of metal, plastic, ceramic material and any chemically
inert material, serves to house components of the probe head
50.
[0047] There is thus provided a spectrometer assembly comprising a
spectrometer, an interface module, and a fiber optic assembly, each
connectable to and disconnectable from another. In the event of
contamination or damage to the fiber optic assembly, it can be
easily withdrawn from the interface module and replaced. The
interface module may similarly be separated from the spectrometer
and the probe head assembly and replaced with a module containing a
different arrangement of light manipulation devices.
[0048] There is further provided a fiber optic assembly in which
the probe head projects substantially only laser light, not mixed
with Raman signature light.
[0049] There is still further provided a fiber optic assembly
having, or in combination with, a lens which accepts diverging
laser light exiting an excitation fiber and focuses the laser light
on a limited area of a specimen under test, and which accepts
diverging Raman signal light from the specimen and focuses the
Raman light on a distal end of a collection fiber.
[0050] The above-described assembly may be used to obtain a Raman
analysis in accordance with a method including the steps of
providing the Raman spectrometer 22 having the laser light source
and the Raman signal analyzer, providing the interface module 24
which is adapted for attachment to the spectrometer 22, the module
24 having therein light manipulating devices 28 for directing laser
light and Raman signal light for effecting excitation of the
specimen and collection and directing of Raman signal light to the
Raman signal analyzer, and providing the fiber optic assembly 27
comprising the excitation fiber 44, the collection fiber 64, and
the probe head 50, attaching the interface module 24 to the
spectrometer 22, attaching the fiber optic assembly to the
interface module 24, placing the probe head 50 adjacent the
specimen S, and energizing the laser light source LS, whereby to
cause laser light to pass from the spectrometer 22 to the interface
module 24 and therein to be directed by the light manipulating
devices 28 to the excitation fiber 44 and the probe head 50 and
onto the specimen S, and thence Raman signal light back through the
collection fiber 64 to the interface module 24 wherein the
manipulating devices 28 direct the Raman signal light to the
spectrometer Raman light analyzer LA.
[0051] The method preferably includes the further step of providing
the focusing lens 72 between the fiber distal ends 48, 66 and the
specimen S, such that Raman signal light from the specimen is
focused on the distal end 66 of the collection fiber 64.
[0052] It is to be understood that the present invention is by no
means limited to the particular construction and method steps
disclosed and/or shown in the drawings, but also comprises any
modification or equivalent within the scope of the claims.
* * * * *