U.S. patent application number 13/881673 was filed with the patent office on 2013-08-29 for system for sensing a mechanical property of a sample.
The applicant listed for this patent is Roozbeh Ahmadi, Javad Dargahi, Muthukumaran Packirisamy. Invention is credited to Roozbeh Ahmadi, Javad Dargahi, Muthukumaran Packirisamy.
Application Number | 20130220032 13/881673 |
Document ID | / |
Family ID | 45993006 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130220032 |
Kind Code |
A1 |
Packirisamy; Muthukumaran ;
et al. |
August 29, 2013 |
System For Sensing a Mechanical Property of a Sample
Abstract
A sensing element for sensing a mechanical property of a sample
defining a sample surface using a contact force exerted the sample
surface. The sensing element includes: a deformable element
defining a contact surface and a deformable section in register
with the contact surface, the deformable section being deformable
between an undeformed configuration and a deformed configuration; a
deformation sensor operatively coupled to the deformable section
for sensing and quantifying a deformation of the deformable section
between the deformed and undeformed configurations, the deformation
sensor being an optical deformation sensor; and a force sensor
operatively coupled to the deformable element for sensing the
contact force exerted on the contact surface.
Inventors: |
Packirisamy; Muthukumaran;
(Pierrefonds, CA) ; Ahmadi; Roozbeh; (Montreal,
CA) ; Dargahi; Javad; (Lasalle, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Packirisamy; Muthukumaran
Ahmadi; Roozbeh
Dargahi; Javad |
Pierrefonds
Montreal
Lasalle |
|
CA
CA
CA |
|
|
Family ID: |
45993006 |
Appl. No.: |
13/881673 |
Filed: |
October 26, 2011 |
PCT Filed: |
October 26, 2011 |
PCT NO: |
PCT/CA2011/001192 |
371 Date: |
May 2, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61344859 |
Oct 26, 2010 |
|
|
|
Current U.S.
Class: |
73/862.624 |
Current CPC
Class: |
G01B 11/18 20130101;
G01L 1/24 20130101; G01L 1/18 20130101; G01L 1/242 20130101; G01D
5/353 20130101; G01L 1/16 20130101; A61B 34/76 20160201; G01L 1/243
20130101; A61B 2090/065 20160201; G01D 5/268 20130101; G01M 11/085
20130101; A61B 34/30 20160201 |
Class at
Publication: |
73/862.624 |
International
Class: |
G01L 1/24 20060101
G01L001/24 |
Claims
1. A sensing element for sensing a mechanical property of a sample
defining a sample surface using a contact force exerted on said
sensing element by said sample surface, said sensing element
comprising: a deformable element defining a deformable element
first end and a substantially opposed deformable element second
end, said deformable element defining a contact surface and a
deformable section substantially in register with said contact
surface between said deformable element first and second ends, said
deformable section being deformable between an undeformed
configuration and a deformed configuration, wherein said deformable
section is in said undeformed configuration when no external forces
are exerted on said contact surface and said deformable section is
in said deformed configuration when said contact force is exerted
on said contact surface; a deformation sensor operatively coupled
to said deformable section for sensing and quantifying a
deformation of said deformable section between said deformed and
undeformed configurations, said deformation sensor being an optical
deformation sensor; and a force sensor operatively coupled to said
deformable element for sensing said contact force exerted on said
contact surface; whereby, when said contact and sample surfaces are
abutted against each other and biased toward each other said
contact force is created on said contact surface and sensed by said
force sensor; and said deformable section achieves said deformed
configuration, said deformed configuration being sensed and
quantified by said deformation sensor.
2. A sensing element as defined in claim 1, wherein said
deformation sensor includes a deformation sensor interrupted
optical waveguide defining a deformation sensor waveguide first
segment, a deformation sensor waveguide second segment and a
deformation sensor gap extending therebetween, said deformation
sensor gap being provided substantially in register with said
deformable section, said deformation sensor waveguide first and
second segments being optically coupled to each other across said
deformation sensor gap and secured to said deformable element with
said deformation sensor waveguide first and second segments fixed
with respect to said deformable section substantially adjacent said
deformation sensor gap, whereby optical coupling between said
deformation sensor waveguide first and second segments varies as
said deformable section is moved between said undeformed and
deformed configurations.
3. A sensing element as defined in claim 2, wherein said deformable
element defines a waveguide receiving surface opposed to said
contact surface, said deformation sensor interrupted optical
waveguide being secured to said waveguide receiving surface.
4. A sensing element as defined in claim 3, wherein said
deformation sensor interrupted optical waveguide is a deformation
sensor optical fiber, said deformation sensor waveguide first and
second segments being respectively a deformation sensor fiber first
segment and a deformation sensor fiber second segment.
5. A sensing element as defined in claim 4, wherein said waveguide
receiving surface defines a substantially elongated fiber receiving
groove extending thereinto, said deformation sensor fiber first and
second segments being provided in said fiber receiving groove.
6. A sensing element as defined in claim 5, wherein said
deformation sensor waveguide first and second segments are bonded
to said deformable element in said fiber receiving groove.
7. A sensing element as defined in claim 2, wherein said
deformation sensor waveguide first segment extends between said
deformable element first end and said deformation sensor gap; and
said deformation sensor waveguide second segment extends between
said deformable element second end and said deformation sensor
gap.
8. A sensing element as defined in claim 2, wherein said
deformation sensor waveguide first segment extends between said
deformable element first end and said deformation sensor gap, and
said deformation sensor waveguide second segment extends from said
deformation sensor gap towards said deformable element second end
and is provided with a light reflective end surface opposed to said
deformation sensor gap.
9. A sensing element as defined in claim 2, wherein said deformable
element defines an auxiliary light guiding element provided between
said deformation sensor gap and said deformable element second end;
said deformation sensor waveguide first segment extends between
said deformable element first end and said deformation sensor gap;
said deformation sensor waveguide second segment extends between
said deformation sensor gap and said auxiliary light guiding
element; said deformation sensor interrupted optical waveguide
defines a deformation sensor waveguide third segment extending
between said deformable element first end and said auxiliary light
guiding element; said auxiliary light guiding element optically
couples said deformation sensor waveguide second and third
segments.
10. A sensing element as defined in claim 9, wherein said auxiliary
light guiding element includes a mirror.
11. A sensing element as defined in claim 9, wherein said auxiliary
light guiding element includes a pair of mirrors configured for
changing a light direction propagation of light incoming at said
mirrors by about 180 degrees.
12. A sensing element as defined in claim 9, wherein said
deformation sensor waveguide second and third segments are in a
substantially parallel and spaced apart relationship relative to
each other.
13. A sensing element as defined in claim 2, further comprising a
base, said base and said deformable element extending in a
substantially parallel and spaced apart relationship relative to
each other.
14. A sensing element as defined in claim 13, further comprising a
first spacing element extending between said base and said
deformable element substantially adjacent said deformable element
first end.
15. A sensing element as defined in claim 14, wherein said
deformable element second end is movable with respect to said
base.
16. A sensing element as defined in claim 14, further comprising a
second spacing element extending between said base and said
deformable element substantially adjacent said deformable element
second end.
17. A sensing element as defined in claim 2, wherein in said
undeformed configuration, said deformation sensor waveguide first
and second segments have substantially coaxial optical axes.
18. A sensing element as defined in claim 1, wherein said
deformation sensor includes at least two deformation sensor
interrupted optical waveguides each defining a respective
deformation sensor waveguide first segment, a respective
deformation sensor waveguide second segment and a respective
deformation sensor gap extending therebetween, said deformation
sensor gaps being provided substantially in register with said
deformable section, said respective deformation sensor waveguide
first and second segments being optically coupled to each other
across said respective deformation sensor gaps and each secured to
said deformable element with said deformation sensor waveguide
first and second segments fixed with respect to said deformable
section substantially adjacent said deformation sensor gaps,
whereby optical coupling between said deformation sensor waveguide
first and second segments varies as said deformable section is
moved between said undeformed and deformed configurations.
19. A sensing element as defined in claim 18, wherein said
deformation sensor interrupted optical waveguides extend
substantially parallel to each other in a laterally spaced apart
relationship relatively to each other.
20. A sensing element as defined in claim 18, wherein said
deformation sensor gaps are longitudinally offset with respect to
each other.
21. A sensing element as defined in claim 1, further comprising a
base, said base and said deformable element extending in a spaced
apart relationship relative to each other; and a first spacing
element extending between said base and said deformable
element.
22. A sensing element as defined in claim 21, wherein said base and
said deformable element extend in a substantially parallel
relationship relative to each other.
23. A sensing element as defined in claim 21, wherein said force
sensor is an optical force sensor.
24. A sensing element as defined in claim 21, wherein said force
sensor includes a force sensor interrupted optical waveguide
defining a force sensor waveguide first segment, a force sensor
waveguide second segment and a force sensor gap extending
therebetween, said force sensor waveguide first segment extending
through said first spacing element and being fixed relative thereto
substantially adjacent said force sensor gap, said force sensor
waveguide second segment being supported by said base and fixed
relative thereto substantially adjacent said force sensor gap, said
force sensor waveguide first and second segments being optically
coupled to each other across said force sensor gap, said first
spacing element including a first support resiliently deformable
section provided between said base and said force sensor optical
waveguide first segment, whereby, when said first support
resiliently deformable section is compressed, said force sensor
waveguide first segment is moved relative to said force sensor
waveguide second segment, which changes optical coupling between
said force sensor waveguide first and second segments.
25. A sensing element as defined in claim 24, wherein said force
sensor interrupted optical waveguide is a force sensor optical
fiber, said force sensor waveguide first and second segments being
respectively a force sensor fiber first segment and a force sensor
fiber second segment.
26. A sensing element as defined in claim 25, wherein said force
sensor fiber first and second segments are inserted respectively
through a first ferrule and a second ferrule, said first ferrule
extending through said first spacing element and said second
ferrule being supported by said base.
27. A sensing element as defined in claim 24, wherein said first
support resiliently deformable section is made out of a material
selected from the group consisting of Polydimethylsiloxane (PDMS),
silicone rubbers, epoxy, and rubbers.
28. A sensing element as defined in claim 21, wherein said first
spacing element is substantially adjacent said deformable element
first end.
29. A sensing element as defined in claim 21, further comprising a
second spacing element extending between said base and said
deformable element, said first and second spacing elements being
spaced apart from each other and respectively provided
substantially adjacent said deformable element first and second
ends.
30. A sensing element as defined in claim 29, wherein said force
sensor includes a force sensor first interrupted optical waveguide
defining a force sensor first waveguide first segment, a force
sensor first waveguide second segment and a force sensor first gap
extending therebetween, said force sensor first waveguide first
segment extending through said first spacing element and being
fixed relative thereto substantially adjacent said force sensor
first gap, said force sensor first waveguide second segment being
supported by said base and fixed relative thereto substantially
adjacent said force sensor first gap, said force sensor first
waveguide first and second segments being optically coupled to each
other across said force sensor first gap, said first spacing
element including a first support resiliently deformable section
provided between said base and said force sensor first waveguide
first segment; a force sensor second interrupted optical waveguide
defining a force sensor second waveguide first segment, a force
sensor second waveguide second segment and a force sensor second
gap extending therebetween, said force sensor second waveguide
first segment extending through said second spacing element and
being fixed relative thereto substantially adjacent said force
sensor second gap, said force sensor second waveguide second
segment being supported by said base and fixed relative thereto
substantially adjacent said force sensor second gap, said force
sensor second waveguide first and second segments being optically
coupled to each other across said force sensor second gap, said
second spacing element including a second support resiliently
deformable section provided between said base and said force sensor
second waveguide first segment; whereby, when said first support
resiliently deformable section is compressed, said force sensor
first waveguide first segment is moved relative to said force
sensor first waveguide second segment, which changes optical
coupling between said force sensor first waveguide first and second
segments, and when said second support resiliently deformable
section is compressed, said force sensor second waveguide first
segment is moved relative to said force sensor second waveguide
second segment, which changes optical coupling between said force
sensor second waveguide first and second segments.
31. A sensing element as defined in claim 21, wherein said force
sensor includes a piezoresistive or a piezoelectric element
provided between said first spacing element and said base.
32. A system for measuring a mechanical property of a sample
defining a sample surface using a contact force by said sample
surface, said system comprising: a sensing element as defined in
claim 2; a light source optically coupled to said deformation
sensor waveguide first segment opposed to said deformation sensor
gap for emitting a source light in said deformation sensor
waveguide first segment; a light detector optically coupled to said
deformation sensor waveguide second segment opposed to said
deformation sensor gap for detecting an intensity of light received
from said deformation sensor waveguide second segment; a controller
operatively coupled to said light detector for receiving said
intensity of light received from said deformation sensor waveguide
second segment when said source light is emitted in said
deformation sensor waveguide first segment and computing a
deformation of said deformable section using a power loss of said
source light across said sensing element; and an output element for
outputting said deformation.
33. A system for measuring a mechanical property of a sample
defining a sample surface using a contact force exerted on said
sensing element by said sample surface, said system comprising: a
sensing element as defined in claim 2; a light source optically
coupled to said force sensor waveguide first segment opposed to
said force sensor gap for emitting a source light in said force
sensor waveguide first segment; a light detector optically coupled
to said force sensor waveguide second segment opposed to said force
sensor gap for detecting an intensity of light received from said
force sensor waveguide second segment; a controller operatively
coupled to said light detector for receiving said intensity of
light received from said force sensor waveguide second segment when
said source light is emitted in said force sensor waveguide first
segment and computing said contact force exerted on said contact
surface using a power loss of said source light across said sensing
element; and an output element for outputting said contact
force.
34. (canceled)
35. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the art of sensors. More
specifically, the present invention is concerned with systems for a
mechanical property of a sample. In some embodiments of the
invention, the system uses optical components for sensing the
deformation of the sample in response to a force exerted thereonto,
the force being also measured.
BACKGROUND OF THE INVENTION
[0002] In conventional surgery, surgeons use their fingers to
measure the softness/hardness of tissues. Using this type of
palpation, surgeons can investigate hidden anatomical features of
tissues. They can also distinguish between different types of
tissues. For example, they can identify abnormal tissues (such as
tumorous lumps), blood vessels, ureters, and bony or fatty tissues.
However, current commercially available minimally invasive robotic
surgery (MIRS) systems do not provide tactile feedback from the
interaction between surgical tools and tissues.
[0003] Indeed, despite the superiority in many cases of MIRS over
conventional open surgery techniques, it has a few unsolved
shortcomings. One of them is the lack of haptic feedback to
surgeons. Such haptic feedback relies on sensory feedback, which
consists of both the kinesthetic and cutaneous tactile feedback
streams. Haptic feedback, which occurs while surgical instruments
are interacting with tissues, can lead to better MIRS. For
instance, visual force feedback results in reduced suture breakage,
lower forces, and decreased force inconsistencies in the da
Vinci.TM. surgical system. Similarly, experimental tests have
proved that the presence of direct force feedback significantly
reduces the force applied by the da Vinci.TM. graspers to the
grasped tissue. That reduced force was not sustainable after
removing the force feedback.
[0004] Therefore, similarly to a human finger, a tactile sensor is
required to measure: 1) the softness/hardness of contact tissue, 2)
the contact distributed load interacting between surgical tools and
tissues, and 3) the position of a concentrated load interacting
between surgical tools and tissues. Also, surgical tool-tissue
interactions take place in both static and dynamic loading
conditions. In order to avoid tissue damage because of the
excessive force applied to the tissue, and also in order to
maintain contact stability between surgical tools and tissues,
surgeons can use a sensor to measure the static contact force
applied to tissues by surgical tools. In addition, tool-tissue
interaction involves low rate changes because of the viscoelastic
properties of tissues. For example, tissue relaxation happens very
slowly. As a result, the tactile sensor must measure the
above-mentioned parameters in both static and dynamic loading
conditions.
[0005] Finally, minimally invasive robotic surgeries are frequently
performed in the presence of electro-magnetic fields. Magnetic
resonance imaging (MRI) devices induce strong electro-magnetic
fields. Nowadays, during MIRS, these devices are in widespread use
in surgical rooms for various types of applications. For example,
surgeons widely use MRI to investigate the live organs during MIRS.
As another example, in MIRS applications, surgeons also use them to
guide the surgical instruments and to track the position of
surgical tools inside the body. Similarly, radio frequency (RF)
pulses are usually present in the surgical operating rooms. For
example, RF coil of MRI devices is one of the sources for RF
pulses. Therefore, performing tactile measurements with currently
existing tactile sensors, which include electrical wires, are
impossible in many MIRS operations. Electrical wires included in
the conventional sensors, such as piezoelectric sensors, usually
induce eddy current fields which disturb the MRI images. In other
words, in MRI environment, the use of electronics is not practical.
Therefore, the surgical robot as well as its components such as
sensors must be MRI compatible. Thus it is crucial to develop
sensors performing tactile measurements even with the
electromagnetic interference present in the surgical operating
rooms. Hence, there is a need for novel concept of tactile sensor
with components that are insensitive to electromagnetic fields.
This ability allows sensors to work within environments with strong
electromagnetic fields. In addition, for some specific types of
surgeries, the sensor should be electrically passive due to the
safety concerns of introducing electrical currents into the body.
For instance, in intracardiac surgeries, to avoid disrupting normal
electrical activities in the heart, which is an electrically active
environment, the sensor must be electrically passive. As a result,
the tactile sensor must be MRI compatible and electrically
passive.
[0006] Accordingly, there is a need in the industry to provide an
improved system for sensing a mechanical property of a sample. An
object of the present invention is therefore to provide such a
system.
SUMMARY OF THE INVENTION
[0007] In a broad aspect, the invention provides a sensing element
for sensing a mechanical property of a sample defining a sample
surface using a contact force exerted on the sensing element by the
sample surface. The sensing element includes: a deformable element
defining a deformable element first end and a substantially opposed
deformable element second end, the deformable element defining a
contact surface and a deformable section substantially in register
with the contact surface between the deformable element first and
second ends, the deformable section being deformable between an
undeformed configuration and a deformed configuration, wherein the
deformable section is in the undeformed configuration when no
external forces are exerted on the contact surface and the
deformable section is in the deformed configuration when the
contact force is exerted on the contact surface; a deformation
sensor operatively coupled to the deformable section for sensing
and quantifying a deformation of the deformable section between the
deformed and undeformed configurations, the deformation sensor
being an optical deformation sensor; and a force sensor operatively
coupled to the deformable element for sensing the contact forces
exerted on the contact surface. When the contact and sample
surfaces are abutted against each other and biased towards each
other, the contact force is created on the contact surface and
sensed by the force sensor; and the deformable section achieves the
deformed configuration, the deformed configuration being sensed and
quantified by the deformation sensor.
[0008] In a variant, the deformation sensor includes a deformation
sensor interrupted optical waveguide defining a deformation sensor
waveguide first segment, a deformation sensor waveguide second
segment and a deformation sensor gap extending therebetween, the
deformation sensor gap being provided substantially in register
with the deformable section, the deformation sensor waveguide first
and second segments being optically coupled to each other across
the deformation sensor gap and secured to the deformable element
with the deformation sensor waveguide first and second segments
fixed with respect to the deformable section substantially adjacent
the deformation sensor gap. Optical coupling between the
deformation sensor waveguide first and second segments varies as
the deformable section is moved between the undeformed and deformed
configurations.
[0009] For the purpose of this document, an interrupted optical
waveguide is an optical waveguide along which a section has been
removed to create a gap. The light propagates without guidance
across the gap. The reader skilled in the art will appreciate that
in practice, the interrupted waveguide can be assembled using two
waveguide segments that were not necessarily extending from each
other prior to assembly of the sensing element. Also, the waveguide
segments need not be of the same shape or made out of the same
materials.
[0010] In some embodiments of the invention, the deformable element
defines a waveguide receiving surface opposed to the contact
surface, the deformation sensor interrupted optical waveguide being
secured to the waveguide receiving surface.
[0011] In some embodiments of the invention, the deformation sensor
interrupted optical waveguide is a deformation sensor optical
fiber, the deformation sensor waveguide first and second segments
being respectively a deformation sensor fiber first segment and a
deformation sensor fiber second segment. For example, the waveguide
receiving surface defines a substantially elongated fiber receiving
groove extending thereinto, the deformation sensor fiber first and
second segments being provided in the fiber receiving groove. In a
specific example, the deformation sensor waveguide first and second
segments are bonded to the deformable element in the fiber
receiving groove.
[0012] In some embodiments of the invention, the deformation sensor
waveguide first segment extends between the deformable element
first end and the deformation sensor gap and the deformation sensor
waveguide second segment extends between the deformable element
second end and the deformation sensor gap.
[0013] In other embodiments of the invention, the deformation
sensor waveguide first segment extends between the deformable
element first end and the deformation sensor gap, and the
deformation sensor waveguide second segment extends from the
deformation sensor gap towards the deformable element second end
and is provided with a light reflective end surface opposed to said
deformation sensor gap.
[0014] In yet other embodiments of the invention, the deformable
element defines an auxiliary light guiding element provided between
the deformation sensor gap and the deformable element second end;
the deformation sensor waveguide first segment extends between the
deformable element first end and the deformation sensor gap; the
deformation sensor waveguide second segment extends between the
deformation sensor gap and the auxiliary light guiding element; the
deformation sensor interrupted optical waveguide defines a
deformation sensor waveguide third segment extending between the
deformable element first end and the auxiliary light guiding
element; and the auxiliary light guiding element optically couples
the deformation sensor waveguide second and third segments. For
example, the auxiliary light guiding element includes a mirror. In
a specific example, the auxiliary light guiding element includes a
pair of mirrors configured for changing a light direction
propagation of light incoming at the mirrors by about 180 degrees.
Also, for example, the deformation sensor waveguide second and
third segments are in a substantially parallel and spaced apart
relationship relative to each other.
[0015] In a variant, the sensing element further includes a base,
the base and the deformable element extending in a substantially
parallel and spaced apart relationship relative to each other. In
some embodiments of the invention, a first spacing element extends
between the base and the deformable element substantially adjacent
the deformable element first end. For example, the deformable
element second end is movable with respect to the base. In another
example, a second spacing element extends between the base and the
deformable element substantially adjacent the deformable element
second end.
[0016] In some embodiments of the invention, in the undeformed
configuration, the deformation sensor waveguide first and second
segments have substantially coaxial optical axes.
[0017] In a variant, the deformation sensor includes at least two
deformation sensor interrupted optical waveguides each defining a
respective deformation sensor waveguide first segment, a respective
deformation sensor waveguide second segment and a respective
deformation sensor gap extending therebetween, the deformation
sensor gaps being provided substantially in register with the
deformable section, the respective deformation sensor waveguide
first and second segments being optically coupled to each other
across the respective deformation sensor gaps and each secured to
the deformable element with the deformation sensor waveguide first
and second segments fixed with respect to the deformable section
substantially adjacent the deformation sensor gaps. Optical
coupling between the deformation sensor waveguide first and second
segments varies as the deformable section is moved between the
undeformed and deformed configurations.
[0018] In some embodiments of the invention, the deformation sensor
interrupted optical waveguides extend substantially parallel to
each other in a laterally spaced apart relationship relatively to
each other.
[0019] In some embodiments of the invention, the deformation sensor
gaps are longitudinally offset with respect to each other.
[0020] In a variant, the sensing element includes a base, the base
and the deformable element extending in a spaced apart relationship
relative to each other; and a first spacing element extending
between the base and the deformable element. For example, the base
and the deformable element extend in a substantially parallel
relationship relative to each other.
[0021] In a variant, the force sensor is an optical force sensor.
In some embodiments of the invention, the force sensor includes a
force sensor interrupted optical waveguide defining a force sensor
waveguide first segment, a force sensor waveguide second segment
and a force sensor gap extending therebetween, the force sensor
waveguide first segment extending through the first spacing element
and being fixed relative thereto substantially adjacent the force
sensor gap, the force sensor waveguide second segment being
supported by the base and fixed relative thereto substantially
adjacent the force sensor gap, the force sensor waveguide first and
second segments being optically coupled to each other across the
force sensor gap, the first spacing element including a first
support resiliently deformable section provided between the base
and the force sensor optical waveguide first segment. When the
first support resiliently deformable section is compressed, the
force sensor waveguide first segment is moved relative to the force
sensor waveguide second segment, which changes optical coupling
between the force sensor waveguide first and second segments. For
example, the first support resiliently deformable section is made
out of a material selected from the group consisting of
Polydimethylsiloxane (PDMS), silicone rubbers, epoxy, and
rubbers.
[0022] In some embodiments of the invention, the force sensor
interrupted optical waveguide is a force sensor optical fiber, the
force sensor waveguide first and second segments being respectively
a force sensor fiber first segment and a force sensor fiber second
segment. For example, the force sensor fiber first and second
segments are inserted respectively through a first ferrule and a
second ferrule, the first ferrule extending through the first
spacing element and the second ferrule being supported by the base.
Also for example, the first spacing element is substantially
adjacent the deformable element first end.
[0023] In some embodiments of the invention, a second spacing
element extends between the base and the deformable element, the
first and second spacing elements being spaced apart from each
other and respectively provided substantially adjacent the
deformable element first and second ends. For example, in these
embodiments, the force sensor includes a force sensor first
interrupted optical waveguide defining a force sensor first
waveguide first segment, a force sensor first waveguide second
segment and a force sensor first gap extending therebetween, the
force sensor first waveguide first segment extending through the
first spacing element and being fixed relative thereto
substantially adjacent the force sensor first gap, the force sensor
first waveguide second segment being supported by the base and
fixed relative thereto substantially adjacent the force sensor
first gap, the force sensor first waveguide first and second
segments being optically coupled to each other across the force
sensor first gap, the first spacing element including a first
support resiliently deformable section provided between the base
and the force sensor first waveguide first segment; a force sensor
second interrupted optical waveguide defining a force sensor second
waveguide first segment, a force sensor second waveguide second
segment and a force sensor second gap extending therebetween, the
force sensor second waveguide first segment extending through the
second spacing element and being fixed relative thereto
substantially adjacent the force sensor second gap, the force
sensor second waveguide second segment being supported by the base
and fixed relative thereto substantially adjacent the force sensor
second gap, the force sensor second waveguide first and second
segments being optically coupled to each other across the force
sensor second gap, the second spacing element including a second
support resiliently deformable section provided between the base
and the force sensor second waveguide first segment. When the first
support resiliently deformable section is compressed, the force
sensor first waveguide first segment is moved relative to the force
sensor first waveguide second segment, which changes optical
coupling between the force sensor first waveguide first and second
segments, and when the second support resiliently deformable
section is compressed, the force sensor second waveguide first
segment is moved relative to the force sensor second waveguide
second segment, which changes optical coupling between the force
sensor second waveguide first and second segments.
[0024] In a variant, the force sensor includes a piezoresistive
element provided between the first spacing element and the
base.
[0025] In another broad aspect, the invention provides a system for
measuring a mechanical property of a sample defining a sample
surface using a contact force exerted by the sample surface. The
system includes a sensing element as recited above; a light source
optically coupled to the deformation sensor waveguide first segment
opposed to the deformation sensor gap for emitting a source light
in the deformation sensor waveguide first segment; a light detector
optically coupled to the deformation sensor waveguide second
segment opposed to the deformation sensor gap for detecting an
intensity of light received from the deformation sensor waveguide
second segment; a controller operatively coupled to the light
detector for receiving the intensity of light received from the
deformation sensor waveguide second segment when the source light
is emitted in the deformation sensor waveguide first segment and
computing a deformation of the deformable section using a power
loss of the source light across the sensing element; and an output
element for outputting the deformation.
[0026] In yet another broad aspect, the invention provides a system
for measuring a mechanical property of a sample defining a sample
surface using a contact force exerted by the sample surface. The
system includes a sensing element as recited above; a light source
optically coupled to the force sensor waveguide first segment
opposed to the force sensor gap for emitting a source light in the
force sensor waveguide first segment; a light detector optically
coupled to the force sensor waveguide second segment opposed to the
force sensor gap for detecting an intensity of light received from
the force sensor waveguide second segment; a controller operatively
coupled to the light detector for receiving the intensity of light
received from the force sensor waveguide second segment when the
source light is emitted in the force sensor waveguide first segment
and computing the contact force exerted on the contact surface
using a power loss of the source light across the sensing element;
and an output element for outputting the contact force.
[0027] In yet another broad aspect, the invention provides a
deformation detector for detecting a deformation of a deformable
element, the deformation detector including: a deformation sensor
interrupted optical waveguide defining a deformation sensor
waveguide first segment, a deformation sensor waveguide second
segment and a deformation sensor gap extending therebetween, the
deformation sensor waveguide first and second segments being
secured to the deformable element with the deformation sensor
waveguide first and second segments fixed with respect to the
deformable element adjacent the deformation sensor gap; a light
source optically coupled to the deformation sensor waveguide first
segment opposed to the deformation sensor gap for emitting a source
light in the deformation sensor waveguide first segment; a light
detector optically coupled to the deformation sensor waveguide
second segment opposed to the deformation sensor gap for detecting
an intensity of light received from the deformation sensor
waveguide second segment; a controller operatively coupled to the
light detector for receiving the intensity of light received from
the deformation sensor waveguide second segment when the source
light is emitted in the deformation sensor waveguide first segment
and computing a deformation of the deformable element using a power
loss of the source light across the sensing element; and an output
element for outputting the deformation.
[0028] In yet another broad aspect, the invention provides a force
detector for detecting a force, the force detector comprising: a
contact element defining a contact surface for exerting the force
thereagainst; a base; a spacing element extending between the base
and the contact element; a force sensor interrupted optical
waveguide defining a force sensor waveguide first segment, a force
sensor waveguide second segment and a force sensor gap extending
therebetween, the force sensor waveguide first segment extending
through the spacing element, the force sensor waveguide second
segment being supported by the base, the spacing element including
a support resiliently deformable section provided between the base
and the force sensor optical waveguide first segment; a light
source optically coupled to the force sensor waveguide first
segment opposed to the force sensor gap for emitting a source light
in the force sensor waveguide first segment; a light detector
optically coupled to the force sensor waveguide second segment
opposed to the force sensor gap for detecting an intensity of light
received from the force sensor waveguide second segment; a
controller operatively coupled to the light detector for receiving
the intensity of light received from the force sensor waveguide
second segment when the source light is emitted in the force sensor
waveguide first segment and computing the contact force exerted on
the contact surface using a power loss of the source light across
the sensing element; and an output element for outputting the
contact force.
[0029] Advantageously, in some embodiments of the invention, the
proposed sensing element is both MRI compatible and electrically
passive. In some embodiments of the invention, the proposed sensor
measures the biasing force, the position of the biasing force along
the deformable section, and the softness/hardness of contact
objects in both static and dynamic loading conditions while being
MRI-compatible and electrically passive. In addition, it performs
the measurements by having only one single moving part.
[0030] Although the present patent application often makes
reference to applications in the field of robotic surgery, the
devices and methods of the present application also have many other
applications. For example, force and softness sensing systems are
usable in many hostile environmental conditions, such as, for
example, in space exploration. Indeed, tactile feedback is of
paramount importance in the performance of many tasks, but
protective gear often reduces such feedback. Also, in very hostile
environments, robotic systems are used, which could also benefit
greatly from the present invention. Furthermore, the proposed
system can measure other properties of samples, such as
hyperelastic properties, viscoelastic properties, local
discontinuities in the mechanical properties of the sample such as
the degree of softness/hardness, among other possibilities.
[0031] Other objects, advantages and features of the present
invention will become more apparent upon reading of the following
non-restrictive description of preferred embodiments thereof, given
by way of example only and in relation with the following
Figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1, in a schematic view, illustrates a system for
sensing a mechanical property of a sample in accordance with an
embodiment of the present invention, the system including a sensing
element;
[0033] FIG. 2, in a perspective view, illustrates the sensing
element part of the system shown in FIG. 1;
[0034] FIG. 3, in a side elevation view, illustrates the sensing
element shown in FIG. 2;
[0035] FIG. 4, in a perspective view with parts removed,
illustrates the sensing element shown in FIGS. 2 and 3;
[0036] FIG. 5, in a top plan view with parts removed, illustrates
the sensing element shown in FIGS. 2 to 4;
[0037] FIG. 6, in front elevation view, illustrates a deformable
element and a deformation sensor both part of the sensing element
shown in FIGS. 2 to 5;
[0038] FIG. 7, in bottom plan view, illustrates the deformable
element and deformation sensor shown in FIG. 6;
[0039] FIG. 8, in bottom plan view, illustrates an alternative
deformable element and deformation sensor usable in the softness
sensor shown in FIGS. 2 to 5;
[0040] FIG. 9, in a partial perspective view, illustrates the
alternative deformable element shown in FIG. 8;
[0041] FIG. 9a, in a partial perspective view, illustrates another
alternative deformable element;
[0042] FIG. 10, in a perspective view, illustrates an alternative
sensing element usable in the system shown in FIG. 1;
[0043] FIG. 11, in a perspective view with parts removed,
illustrates the sensing element shown in FIG. 10;
[0044] FIG. 12, in bottom plan view, illustrates a deformable
element and deformation sensor part of the sensing element shown in
FIG. 10;
[0045] FIG. 13, in a schematic view, illustrates a system for
sensing a mechanical property of a sample in accordance with an
alternative embodiment of the present invention, the system
including an alternative sensing element;
[0046] FIG. 14, in a perspective view, illustrates the sensing
element part of the system shown in FIG. 13;
[0047] FIGS. 15A and 15B illustrate a deformation of the deformable
element shown in FIG. 7 as a function of an increasing softness of
a sample when the deformation sensor shown in FIGS. 2 to 5 is
biased against the object; and
[0048] FIG. 16, in a front cross-sectional view, illustrates a
simulation of the sensing element shown in FIGS. 2 to 5 abutting
against a sample that includes a hard inclusion.
DETAILED DESCRIPTION
[0049] Referring to FIG. 1, there is shown a system 10 for
measuring a mechanical property of a sample 25, shown in FIGS. 15A
and 15B, defining a sample surface 27 using a contact force exerted
by the sample surface 27. Examples of measurable mechanical
properties include variations in force distributions,
softness/hardness, hyperelastic properties, viscoelastic
properties, and local discontinuities in the mechanical properties
of the sample such as the degree of softness/hardness, among other
possibilities.
[0050] Returning to FIG. 1, the system 10 includes a sensing
element 12. The system also includes a light source 14 and a light
detector 16. Light emitted by the light source 14 is transmitted to
the sensing element 12 through input optical fibres generally
designated by the reference numeral 18. The sensing element 12
transmits partially or totally light received by the input optical
fibres 18 according to the value of the measured mechanical
property of the sample 25. The resulting light is transmitted to
the light detector 16 through output optical fibres generally
designated by reference numeral 20. The light detector 16 detects
the intensity of light incoming from the output optical fibres 20
and transmits this information to a computer 22 that includes a
proper interface 24 for interfacing with the light detector 16.
After suitable processing, the resulting mechanical property
information is either displayed on the computer 22 in a
conventional manner, or transmitted from the computer 22 to a
suitable alternative display, not shown in the drawings. The
computer 22 is therefore a controller operatively coupled to the
light detector 16 for receiving the intensity of light received
from the sensing element 12 when the source light is emitted in the
input optical fibres 18 and computing the mechanical property using
a power loss of the source light across the sensing element 12. The
computer 22 also includes an output element for outputting the
mechanical property, such as a display, a storage medium or a
network interface, among other possibilities.
[0051] The sensing element 12 can be provided on a grasper (not
shown in the drawings), or, in alternative embodiments of the
invention, can be integrated at the tip of a catheter (not shown in
the drawings). In yet other embodiments of the invention, the
sensing element 12 is integrated to any suitable device allowing
positioning of the sensing element 12 at the location at which the
mechanical property is to be measured. Also, in alternative
embodiments of the invention, more than one sensing elements 12 are
integrated to the device allowing positioning of the sensing
elements 12.
[0052] The sensing element 12 is used for sensing the mechanical
property of the sample 25, as seen for example in FIG. 15A, by
abutting the sensing element 12 against the sample 25 and biasing
the sensing element 12 toward the sample 25 with a biasing force
69. In the remainder of this document, the degree of softness of
the sample 25 is used as an example of a mechanical property that
can be measured by the system 10. However, this choice is for
illustrative purpose and other mechanical properties, such as those
mentioned hereinabove, are measurable without departing from the
scope of the invention.
[0053] Referring to FIG. 2, the sensing element 12 includes a
deformable element 26 defining a deformable element first end 31
and a substantially opposed deformable element second end 33, the
deformable element 26 defining a contact surface 35 and a
deformable section 37 substantially in register with the contact
surface between the deformable element first and second ends 31 and
33. The deformable section 37 is deformable between an undeformed
configuration, shown for example in FIG. 2, and a deformed
configuration, shown for example in FIG. 15A. The deformable
section 37 is in the undeformed configuration when no external
forces are exerted on the contact surface 35 and the deformable
section 37 is in the deformed configuration when the contact force
is exerted on the contact surface 35 by the sample 25.
[0054] Returning to FIG. 2, a deformation sensor 28 is operatively
coupled to the deformable section 37 for sensing and quantifying a
deformation of the deformable section 37 between the deformed and
undeformed configurations. The deformation sensor 28 is an optical
deformation sensor that uses changes in a parameter of light that
is propagated in the deformation sensor 28 as a function of the
deformation of the deformable section 37 to sense and quantify the
deformation of the deformable section 37. For example, in the
embodiment shown in the drawings, the parameter is the power of the
light, but other parameters such as phase and polarization, among
other possibilities, are changed in alternative embodiments of the
invention. A force sensor 30 is operatively coupled to the
deformable section 37 for sensing the contact force exerted onto
the contact surface 35 by the sample 25 when the deformable section
37 is biased toward the sample 25 with a biasing force.
[0055] When the contact and sample surfaces 35 and 27 are abutted
against each other and biased toward each other, the contact force
is created on the contact surface 35 and sensed by the force sensor
30 and the deformable section 37 achieves the deformed
configuration, the deformed configuration being sensed and
quantified by the deformation sensor 28.
[0056] Typically, the sensing element 12 includes a base 32 for
supporting the deformable element 26, the deformation sensor 28 and
the force sensor 30. As better seen in FIG. 3, the deformable
element 26 is mechanically coupled to the base 32 and supported in
a spaced apart relationship relatively thereto in a manner such
that the deformable section 37 is deformable with respect to the
base 32. Typically, but not necessarily, the base 32 and the
deformable element 26 extend in a substantially parallel
relationship relative to each other.
[0057] Typically, the sensing element 12 is substantially elongated
and the deformable element 26 is supported substantially adjacent
at two substantially longitudinally opposed ends thereof so as to
allow deformation of its midsection when a force is exerted
thereonto. To that effect, a first spacing element 41 extends
between the base 32 and the deformable element 26. Typically, the
first spacing element 41 extends between the base 32 and the
deformable element 26 substantially adjacent the deformable element
first end 31. In some embodiments of the invention, a second
spacing element 41 extends between the base 32 and the deformable
element 26, typically substantially adjacent the deformable element
second end 33. The first and second spacing elements 41 and 43 link
and mechanically couple the base 32 and the deformable element 26
to each other. However, in alternative embodiments of the invention
(not shown in the drawings), the second spacing element 43 is
omitted and the deformable element second end 33 is movable with
respect to the base 32. In other words, the deformable element 26
is then supported in a cantilevered configuration. In yet other
embodiments of the invention, the base 32 and the deformable
element 26 are coupled to each other in any suitable manner. Also,
sensing elements 12 in which more than one deformable elements 26
are present are also within the scope of the present invention.
[0058] FIGS. 4 and 5 better illustrate the force sensor 30. The
force sensor 30 shown in FIGS. 4 and 5 is configured for sensing
forces at opposed ends of the sensing element 12. However, other
configurations are within the scope of the present invention. For
example, a force sensor could be configured to sense force at only
one end of the sensing element 12. The force sensor 30 is an
optical force sensor that uses changes in a parameter of light that
is propagated in the force sensor 30 as a function of the contact
force exerted of the deformable element 26 to sense and quantify
the contact force exerted on the deformable element 26.
[0059] The force sensor 30 includes a stationary segment 34 and a
pair of mobile segments 36 that are substantially longitudinally
opposed with respect to each other. The stationary segment 34 is
provided between the mobile segments 36. The mobile segments 36 and
the stationary segment 34 all extend from the base 32 substantially
toward the deformable element 26. The stationary segment 34 is
decoupled from the deformable element 26 such that when the
deformable section 37 deforms due to a contact force exerted
thereonto, no force is exerted on the stationary segment 34 toward
the base 32. The mobile segments 36 are, in opposition, operatively
coupled to the deformable element 26 so as to receive forces
exerted on the deformable section 37. Each mobile segment 36 is
part of a respective one of the first and second spacing elements
41 and 43. Therefore, the mobile segments 36 extend between the
base 32 and the deformable element 26 at substantially
longitudinally spaced apart locations along the sensing element
12.
[0060] The first and second spacing elements 41 and 43 each include
a compressible element 38, which defines a spacing element
resiliently deformable element, a mobile optical element support 42
and a pair of ferrules 48. The compressible element 38 is provided
between the base 32 and the deformable element 26 so as to be
compressed when a force is exerted onto the deformable element 26.
The compressible element 38 is typically much more compressible
than either the base 32 or the deformable element 26. Selection of
the compressibility of the compressible element 38 allows for
adjusting the range of forces can be sensed precisely and
effectively by the force sensor 30. In the embodiment of the
invention shown in the drawings, the compressible elements 38 each
extend directly from the base 32 toward the deformable element 26.
It should be noted that in some embodiments of the invention, for
ease of manufacturing reasons, the stationary segments 34 also
includes a compressible element 39 extending from the base 32 that
is made out of the same material used to make the compressible
elements 38. However, since no forces are transmitted to this
compressible element 39 in operation, the stationary segment 34
remains unaffected by the forces exerted onto the deformable
element 26. To achieve this result, the compressible element 39 is
longitudinally spaced apart from the compressible elements 38. The
compressible elements 38 are made out of any suitable material,
such as Polydimethylsiloxane (PDMS), a silicone rubber, an epoxy, a
rubber, or any other suitable material.
[0061] The stationary segment 34 includes a stationary optical
element support 40. Similarly, the first and second spacing
elements 41 and 43 each include one of the mobile optical element
supports 42. The stationary and mobile optical element supports 40
and 42 are made out of material that is typically much less
compressible than the one making up the compressible elements 38
and 39. The stationary and mobile optical element supports 40 and
42 are provided between the compressible elements 38 and 39 and the
deformable element 26. The stationary and mobile optical element
supports 40 and 42 define each a pair of substantially
longitudinally extending support grooves 44 and 46. In each of the
stationary and mobile optical element supports 40 and 42, the
support grooves 44 and 46 are substantially parallel to each other
and extend along the whole length of the stationary and mobile
optical element supports 40 and 42, inwardly toward the base 32.
The stationary and mobile optical element supports 40 and 42 are
usable for supporting optical components that will detect movements
of the stationary and mobile optical element supports 40 and 42 as
forces are exerted onto the deformable element 26. The support
grooves 44 and 46, and all the other grooves described in this
document, are manufactured using any suitable technique, such as,
for example, microelectromechanical system (MEMS) anisotropic
etching.
[0062] One of the ferrules 48 is inserted in each of the support
grooves 46 of the mobile optical element supports 42. A pair of
substantially longitudinally spaced apart ferrules 50 is inserted
in each of the support grooves 44 of the stationary optical element
support 40. Each of the ferrules 48 and 50 is substantially
cylindrical and defines a passageway 52 extending substantially
longitudinally therethrough. The ferrules 48 inserted in the
support grooves 46 of the mobile optical element supports 42 are
substantially similarly dimensioned. Similarly, the ferrules 50
inserted in the support grooves 44 of the stationary optical
element support 40 are substantially similarly dimensioned. The
ferrules 48 and 50 are dimensioned such that when the deformable
element 26 is positioned above the ferrules 48 and 50, the
deformable element 26 abuts against the ferrules 48, but does not
contact the ferrules 50, even when the deformable section 37 is in
the deformed configuration. Also, the ferrules 48 and 50 are
dimensioned so as to be laterally fixed relatively to the support
grooves 46 and 44. Longitudinal immobilization is either provided
through friction, or by fixing with a glue, or by suitable optical
fibre bonding techniques among other possibilities. Each of the
ferrules 48 is substantially axially aligned with and substantially
adjacent to a corresponding ferrule 50. When no force is exerted
onto the deformable element 26 and the base 32, the passageways 52
of substantially adjacent ferrules 48 and 50 are substantially
axially aligned.
[0063] A first force sensor optical fibre 52a extends through all
the passageways 52 of two substantially axially aligned ferrules 48
and their adjacent ferrules 50. A second force sensor optical fibre
52b extends through all the passageways 52 of the other two
substantially axially aligned ferrules 48 and their adjacent
ferrules 50. The first and second force sensing optical fibres 52a
and 52b are secured inside the ferrules 48 and 50 in a conventional
manner. Therefore, two optical paths extending substantially
longitudinally along the sensing element 12 are formed. The two
optical paths are substantially parallel to each other. Each of the
first and second force sensing optical fibres 52a and 52b is
interrupted between a respective one of the mobile segments 36 and
the stationary segment 34, as better seen in FIG. 5. Each of the
first and second force sensing optical fibres 52a and 52b are
optically coupled respectively to one of the input optical fibres
18 at one end thereof and to one of the output optical fibres 20 at
the other end thereof. The force sensing optical fibres 52a and
52b, and all the other optical fibres described in this document
can be single mode or multimode.
[0064] Referring more specifically to FIG. 5, the first force
sensing optical fibre 52a therefore includes a force sensor first
fibre first segment 53a, a force sensor first fibre second segment
55a and a force sensor first gap 57a extending therebetween. The
force sensor first gap 57a is located between the first spacing
element 41 and the stationary segment 34. The force sensor first
fibre first and second segments 53a and 55a are optically coupled
to each other across the force sensor first gap 57a. Similarly, the
second force sensing optical fibre 52b includes a force sensor
second fibre first segment 53b, a force sensor second fibre second
segment 55b and a force sensor second gap 57b extending
therebetween. The force sensor second gap 57b is located between
the second spacing element 43 and the stationary segment 34. The
force sensor second fibre first and second segments 53b and 55b are
optically coupled to each other across the force sensor first gap
57b.
[0065] The force sensor first fibre first segment 53a and the force
sensor second fibre second segment 55b therefore extend
respectively through the first and second spacing elements 41 and
43 and are fixed relative thereto substantially adjacent the
respective force sensor first and second gaps 57a and 57b. The
force sensor second fibre first segment 53b and the force sensor
first fibre second segment 55a are supported by the base 32 and
fixed relative thereto substantially adjacent respectively the
force sensor first and second gaps 57a and 57b.
[0066] In alternative embodiments of the invention, the
above-mentioned optical fibres can be replaced by other types of
optical waveguides that define similar segments, such as waveguides
made of Silicon, Silica, Silicon-On-Insulator (SOI), InP, GaAs,
Polydimethylsiloxane (PDMS), Poly(methyl methacrylate) (PMMA),
other polymer platforms and optically transmitting materials in
their respective wavelength ranges, or a combination of the above
materials, among others, implemented for waveguides. Also, the
optical fibres are any suitable type of optical fibre, such as
single-mode or multi-mode fibres, glass fibres, plastic fibres,
among other possibilities. Also, in alternative embodiments of the
invention, the optical waveguides are not mounted using the
ferrules 48 and 50, but are otherwise attached to the remainder of
the sensing element 12 using other methods known in the art.
[0067] FIGS. 6 and 7 illustrate the deformable element 26. In
addition to the contact surface 35, the deformable section 37
typically defines a waveguide receiving surface 54 opposed to the
contact surface 35 for receiving one or more optical waveguides, as
detailed hereinbelow. However, in alternative embodiments of the
invention, the optical waveguides are coupled to the deformable
element 26 in any other suitable manner, for example by being
embedded therein. The waveguide receiving surface 54 faces toward
the base 32 and the contact surface 35 faces toward the sample 25
for which the mechanical property is to be assessed.
[0068] The waveguide receiving surface 54 is provided with
substantially longitudinally extending support grooves 58 each
positioned, configured and sized for substantially fittingly
receiving thereinto a portion of a pair of substantially axially
aligned ferrules 48. The ferrules 48 are therefore provided between
the deformable element 26 and the mobile optical element supports
42 and transmit forces exerted on the deformable element 26 to the
compressible elements 38.
[0069] The waveguide receiving surface 54 is also provided with
substantially parallel and laterally spaced apart fibre receiving
grooves 60. The fibre receiving grooves 60 each extend
substantially longitudinally along the whole length of the
deformable element 26. Typically, the fibre receiving grooves 60
have a substantially V-shaped transversal cross-sectional
configuration, but other configurations, such as square or circular
configurations, among other possibilities, are within the scope of
the invention. V-shaped cross-sections can be micromachined, for
example by wet anisotropic silicon etching techniques. Also, in
alternative embodiments of the invention, the fibre receiving
grooves 60 have any other suitable configuration.
[0070] The deformable element 26 has any suitable shape, such as an
elongated shape, as in the drawings, but also a substantially
square shape and is made of any suitable material, such as silicon,
a metal or a polymer and combinations thereof, among other
possibilities.
[0071] A deformation sensor optical fibre 62 is inserted in and
along each of the fibre receiving grooves 60 and is secured
thereto. While three deformation sensor optical fibres 62 are shown
in the drawings, any suitable number of deformation sensor optical
fibres 62 can be provided, as long as a corresponding number of
fibre receiving grooves 60 is provided. By using at least three
deformation sensor optical fibres 62 in the shown configuration,
the position of a concentrated force can be measured precisely.
[0072] Each of the deformation sensor optical fibres 62 is
interrupted by a respective deformation sensor gap 64, better seen
in FIG. 7, provided substantially in register with the deformable
section 37. Therefore, each deformation sensor optical fibre 62 is
split into a deformation sensor fibre first segment 65 and a
deformation sensor fibre second segment 67 with the deformation
sensor gap 64 extending therebetween. Each of the deformation
sensor fibre first segments 65 extends between the deformable
element first end 31 and the deformation sensor gap 64 of the
deformation sensor optical fibre 62 to which it belongs and each of
the deformation sensor fibre second segments 67 extends between the
deformable element second end 33 and the deformation sensor gap 64
of the deformation sensor optical fibre 62 to which it belongs.
[0073] The deformation sensor fibre first and second segments 65
and 67 are optically coupled to each other across the deformation
sensor gap 64 and secured to the deformable element 26 with the
deformation sensor fibre first and second segments 65 and 67 fixed
with respect to the deformable section 37 substantially adjacent
the deformation sensor gap 64. In some embodiments of the
invention, the deformation sensor gaps 64 are located at different
longitudinal positions along the deformable section 37, which
allows deformation measurements to be taken at different
longitudinal locations along the deformable section 37. In some
embodiments of the invention, in the undeformed configuration, the
deformation sensor fibre first and second segments 65 and 67 have
substantially coaxial optical axes.
[0074] Each of the deformation sensor optical fibres 62 is
optically coupled to one of the input optical fibres 18 at one end
thereof and to one of the output optical fibres 20 at the other end
thereof. The deformation sensor optical fibres 62 are secured
inside the fibre receiving grooves 60 in a conventional manner, for
example using a glue or optical fibre bonding techniques.
Typically, but not exclusively, the fibre receiving grooves 60 are
provided laterally inwardly with respect to the support grooves 58.
Also, similarly to the force sensor optical fibres 52a and 52b, in
alternative embodiments of the invention, the deformation sensor
optical fibres 62 are replaced by any other suitable optical
waveguide, such as those mentioned hereinabove in the context of
the force sensor optical fibres 52a and 52b.
[0075] In use, the sensing element 12 works as follows. Generally
speaking, optical coupling between the deformation sensor fibre
first and second segments 65 and 67 varies as the deformable
section 37 is moved between the undeformed and deformed
configurations. Measurements of this optical coupling allows
determination of the deformation of the deformable section 37.
Also, when the compressible elements 38 are compressed, the force
sensor fibre first segments 53a and 53b are moved relative to the
force sensor fibre second segments 55a and 55b, which changes
optical coupling between the force sensor waveguide first and
second segments 53a, 53b and 55a, 55b. Measurements of this optical
coupling allows determination of the magnitude of the contact force
exerted on the deformable section 37.
[0076] In greater details, the sensing element 12 is used as
follows, here illustrated in the context of softness/hardness
measurements. First, as seen for example in FIG. 15A, the sensing
element 12 is positioned against the sample 25 and a biasing force
69 is exerted toward the sample 25, for example by exerting a
substantially uniformly distributed biasing force 69 on the base 32
toward the sample 25. This biasing force 69, which produces a
contact force exerted by the sample 25 on the contact surface 35 by
Newton's third law, has two effects on the sensing elements 12.
[0077] The first effect is to compress the compressible elements
38. This compression changes the alignments between the passageways
52 of the ferrules 48 and 50 across the force sensor gaps 57a and
57b. In turn, this changes the transmittance of light emitted by
the light source 14 through the first and second force sensing
optical fibres 52a and 52b. This reduction in transmittance is
detected at the light detector 16. The computer 22 can then use the
measured transmittance to assess the force exerted onto the sensing
element 12. Since two compressible elements 38 are provided, an
average force and its longitudinal gradient can be assessed. These
forces are assessed either by calibrating the sensing element 12,
or by theoretical calculations based on the mechanical properties
of the various components of the sensing element 12.
[0078] The second effect is to deform the deformable section 37 as
the deformable element 26 is pushed into the sample 25. This
deformation changes the alignment between segments of the
deformation sensor optical fibres 62 positioned across the
deformation sensor gaps 64. In turn, this reduces the transmittance
of light emitted by the light source 14 through the deformation
sensor optical fibres 62. This reduction in transmittance is
detected at the light detector 16. The computer 22 can then use the
measured transmittance to assess the deformation of the deformable
section 37. Since many deformation sensor gaps 64 are provided
along the length of the deformable section 37, non-uniform
deformations of the deformable section 37 are detectable.
[0079] As shown in comparing FIGS. 15A and 15B, compared to a hard
sample 25, softer sample 25 result in a greater deformation of the
deformable section 37 for a given same applied force 69. Also, if
the sample 25 is not uniform in mechanical properties, as seen for
example in FIG. 16 in which an alternative sample 125 includes a
hard inclusion 127, the force detected at both ends of the sensing
element 12 will not necessarily be the same. The grey scale in this
Figure indicates the deformation in the sample 125 when the force
69 is exerted on the sensing element 12. In addition, the
deformation of the deformable section 37 will not be longitudinally
uniform. By using finite element modelling, or any other suitable
method, it is possible to compute an approximation of the
softness/hardness distribution in the sample 125.
[0080] FIGS. 8 and 9 illustrate an alternative deformable element
126 and an alternative deformation sensor 128 both usable instead
of the deformable element 26 and deformation sensor 28 in the
sensing element 12. The deformable element 126 defines alternative
fibre receiving grooves 160. Instead of being substantially
elongated and axially open at both ends of the deformable element
126, the alternative fibre receiving grooves 160 are each
substantially U-shaped in the plane of the deformable element 126
and open only at one end thereof. More specifically, each of the
fibre receiving grooves 160 defines a pair of substantially
rectilinear sections 161 (better seen in FIG. 9) provided in a
substantially adjacent and substantially parallel relationship with
respect to each other. The rectilinear sections 161 are axially
open at one end 163 thereof, as seen in FIG. 8, and are linked to
each other at the other end 165 thereof by a linking section 167.
Each of the linking sections 167 defines an auxiliary light guiding
element provided between the deformation sensor gaps 164 and the
deformable element second end 33. To that effect, the linking
section 167 includes a pair of optically reflective surfaces 171,
or mirrors, better seen in FIG. 9, so that light incoming axially
through one of the rectilinear sections 161 is reflected back into
the other rectilinear sections 161 of the same fibre receiving
groove 160. In other words, the optically reflective surfaces 171
are configured for changing a light direction propagation of light
incoming at the optically reflective surfaces 171 by about 180
degrees.
[0081] Deformation sensor optical fibres 162a and 162b are provided
in a respective one of the rectilinear sections 161 of each fibre
receiving groove 160. The deformation sensor optical fibres 162a
are continuous and uninterrupted. The deformation sensor optical
fibres 162b each define a deformation sensor gap 164 therealong.
The deformation sensor gaps 164 are provided at different
longitudinal locations along the deformable section 137.
[0082] In use, light from the input optical fibres 18 is provided
to the deformation sensor optical fibres 162a to propagate
therethrough to the linking section 167, at which point it is
reflected in the deformation sensor optical fibres 162b and fed to
the output optical fibres 20. Determination of the deformation of
the deformable section 137 then proceeds similarly to that made for
deformable section 37.
[0083] In yet other embodiments of the invention, as seen in FIG.
9a the optically reflective surfaces 171 and deformation sensor
optical fibres 162a are omitted in an alternative deformable
element 226 and alternative deformation sensor 228. Instead, only
the deformation sensor optical fibres 262b are provided in a
respective one of the each fibre receiving grooves 60 that extend
rectilinearly. The deformation sensor optical fibres 262b include
an optically reflective coating. For example, the deformation
sensor optical fibres 262b include a gold coated optical fibre
segment 271 substantially adjacent the deformable element second
end 33 and provided with a light reflective end surface 269 opposed
to the deformation sensor gap 164. The gold coated optical fibre
segments 271 reflect the light arriving at the light reflective end
surface 269. Alternatively, the whole deformation sensor optical
fibres 162b are gold coated.
[0084] FIG. 10 illustrates an alternative sensing element 212. This
sensing element 212 functions substantially similarly to the
sensing element 12, but does not require the ferrules 48 and 50.
Instead, all the optical fibres contained in the sensing element
212 are inserted in suitably shaped grooves and the various
components of each the first and second spacing elements 241 and
243 are stacked directly on top of each other.
[0085] More specifically, the sensing element 212 is similar to the
sensing element 12 except that it includes an alternative
deformable element 226, alternative mobile segments 236 and an
alternative stationary segment 234. As seen in FIG. 12, the
deformable element 226 is substantially similar to the deformable
element 26, except that the support grooves 58 are omitted.
Therefore, except for the fibre receiving grooves 60, the fibre
receiving surface 254 of the deformable element 226 is
substantially planar. Otherwise, the deformable element 226 and the
deformation sensor 228 work substantially similarity to the
corresponding structures in the sensing element 12.
[0086] Referring to FIG. 11, the stationary segment 234 and the
mobile segments 236 include stationary and mobile optical element
supports 240 and 242 respectively deprived of the support grooves
44 and 46. Instead, fibre receiving grooves 244 and 246 are
provided respectively in the stationary and mobile optical element
supports 240 and 242. The fibre receiving grooves 244 and 246 are
shaped similarly to the fibre receiving grooves 60 of the
deformable element 226 and are provided substantially in register
therewith. This configuration allows for using a single mask to
manufacture the fibre receiving grooves 244 and 246 and the fibre
receiving grooves 60 when microfabrication techniques are used to
manufacture the sensing element 212. Spacers 270 extend between the
mobile optical element supports 242 and the deformable element 226
and are provided laterally outwardly with respect to the fibre
receiving grooves 244 and 246. Therefore, instead of being
transmitted through the ferrules 48, forces exerted onto the
deformable element 226 are transmitted to the base 32 and the
compressible elements 38 through the spacers 270. Otherwise, the
principle on which the force sensor 230 is based is substantially
similar to the principle on which the force sensor 30 is based and
depends on changes in light transmission of optical fibres when the
compressible elements 38 are compressed.
[0087] Referring to FIG. 13, there is shown an alternative system
310 for sensing and displaying softness and force, or other
mechanical properties of the sample 25. The system 310 is
substantially similar to the system 10 and only the differences
between these two systems are described hereinbelow. The system 310
includes a power supply 372 and an electronic circuit 374. The
power supply 372 provides power to an electrically powered force
sensor 330, shown in FIG. 14, which feeds electrical signals to the
electronic circuit 374. These electrical signals are indicative of
the force exerted onto the force sensor 330 and the electronic
circuit 374 is adapted for conveying this force information to the
computer 22. Otherwise, deformation sensing is performed as been
the system 10.
[0088] As seen in FIG. 14, an alternative sensing element 312
includes a pair of piezoresistive elements 338 that replace the
compressible elements 38. Force sensing is effected by the
piezoresistive elements 338 by measuring changes in resistance
caused by compression of these piezoresistive elements 338.
Therefore, the force sensing optical fibres 52a and 52b, and the
ferrules 48 and 50 are omitted from the force sensor 330. For
clarity reasons, wires that are used to receive the electrical
signals provided by the piezoresistive elements 338 are not shown
in FIG. 14, but the reader skilled in the art will readily
appreciate which configurations wires would provide satisfactory
signal acquisition. Also for example, the piezoresistive element is
made of semiconductive polymer composites such as carbon-filled
polyethylene films. As another alternative, instead of the
piezoresistive element, piezoelectric elements such as
Polyvinylidene Fluoride (PVDF) can be used.
[0089] All the above described deformation sensors 28 and force
sensors 30 can be mixed together in any suitable manner to form the
sensing elements 12. Also, in alternative embodiments of the
invention, either of the deformation sensor 28 and force sensor 30
can be replaced by conventional deformation and force sensors.
[0090] In some embodiments of the invention, the sensing elements
12, 212 and 312 are manufactured using microfabrication technology
and, for example, are mostly made out of silicon, except for the
compressible elements 38 which are made out of a more compressible
material, such as, for example, polydimethylsiloxane (PDMS),
silicone-rubber, rubber, an epoxy, a rubber, or a polymer, among
others.
[0091] The reader skilled in the art will readily appreciate that
the above described force and deformation sensors 30 and 28 are
usable independently from each other in alternative devices.
[0092] Although the present invention has been described
hereinabove by way of preferred embodiments thereof, it can be
modified, without departing from the spirit and nature of the
subject invention as defined in the appended claims.
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