U.S. patent application number 12/698377 was filed with the patent office on 2010-08-05 for method and apparatus for determining concentration using polarized light.
This patent application is currently assigned to DEKA Products Limited Partnership. Invention is credited to Jacob W. Scarpaci.
Application Number | 20100195101 12/698377 |
Document ID | / |
Family ID | 39365340 |
Filed Date | 2010-08-05 |
United States Patent
Application |
20100195101 |
Kind Code |
A1 |
Scarpaci; Jacob W. |
August 5, 2010 |
Method and Apparatus for Determining Concentration Using Polarized
Light
Abstract
An apparatus and method for determining the concentration of
chiral molecules in a fluid includes a first polarizer configure to
polarize light in substantially a first plane to provide initially
polarized light. A second polarizer is capable of polarizing the
initially polarized light in a plurality of planes, at least one of
the plurality of planes being different from the first plane, to
provide subsequently polarized light. One or more receivers are
included for measuring an intensity of the subsequently polarized
light in one or more of the plurality of planes.
Inventors: |
Scarpaci; Jacob W.;
(Manchester, NH) |
Correspondence
Address: |
Michelle Saquet Temple
DEKA Research & Development Corp., 340 Commercial Street
Manchester
NH
03101-1129
US
|
Assignee: |
DEKA Products Limited
Partnership
Manchester
NH
|
Family ID: |
39365340 |
Appl. No.: |
12/698377 |
Filed: |
February 2, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11936437 |
Nov 7, 2007 |
7656527 |
|
|
12698377 |
|
|
|
|
60857392 |
Nov 7, 2006 |
|
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Current U.S.
Class: |
356/364 |
Current CPC
Class: |
G01N 21/21 20130101;
G01N 2201/0683 20130101 |
Class at
Publication: |
356/364 |
International
Class: |
G01J 4/00 20060101
G01J004/00 |
Claims
1. An apparatus comprising: a first polarizer configured to
polarize light substantially in a first plane; a second polarizer
configured to polarize light in a plurality of planes, at least one
of the plurality of planes being different from the first plane;
and one or more receivers capable of measuring an intensity of
incident light transmitted through the first polarizer and through
the second polarizer.
2. The apparatus of claim 1 further including a light source
capable of providing light incident upon the first polarizer, the
light incident upon the first polarizer being substantially
randomly polarized.
3. The apparatus of claim 1, further including a fluid chamber, at
least a portion of the fluid chamber at least partially disposed
between the first polarizer and the second polarizer.
4. The apparatus of claim 3, wherein the fluid chamber includes an
at least partially transparent fluid line configured to allow a
fluid containing a concentration of chiral molecules to flow
through the fluid chamber.
5. The apparatus of claim 4, wherein the chiral molecules include
glucose molecules.
6. The apparatus of claim 1, wherein the second polarizer includes
a polarizer array including one or more polarizing elements, each
of the one or more polarizing elements configured to polarize light
substantially in a respective single plane, each of the respective
single planes being different from one or more of the other of the
respective single planes.
7. The apparatus of claim 1, wherein the second polarizer includes
a gradient polarizer configured to polarize light in a plurality of
different planes.
8. The apparatus of claim 1, wherein at least one of the one or
more receivers are capable of measuring an intensity of light in
one or more of the plurality of planes.
9. The apparatus of claim 1, wherein the receiver includes a linear
receiver array.
10. The apparatus of claim 1, wherein the receiver includes one or
more individual receivers, at least one individual receiver
associated with each of the plurality of planes.
11. A method comprising: polarizing light in substantially a first
plane to provide initially polarized light; transmitting the
initially polarized light through a fluid chamber; polarizing the
initially polarized light transmitted through the fluid chamber in
a plurality of planes, at least one of the plurality of planes
being different from the first plane, to provide subsequently
polarized light; and measuring an intensity of the subsequently
polarized light in one or more of the plurality of planes.
12. The method of claim 11, further including providing a fluid
capable of containing a concentration of chiral molecules in the
fluid chamber.
13. The method of claim 12, wherein the chiral molecules include
glucose molecules.
14. The method of claim 12, further including measuring an
intensity of the subsequently polarized light when the fluid
chamber does not contain the fluid and measuring an intensity of
the subsequently polarized light when the fluid chamber contains
the fluid.
15. The method of claim 14, further including comparing a measured
intensity of the subsequently polarized light when the fluid
chamber does not contain the fluid and a measured intensity of the
subsequently polarized light when the fluid chamber contains the
fluid.
16. The method of claim 15, further including determining the
concentration of the chiral molecules based upon, at least in part,
a difference in the measured intensity of the subsequently
polarized light when the fluid chamber does not contain the fluid
and the measured intensity of the subsequently polarized light when
the fluid chamber contains the fluid.
17. The method of claim 16, further including providing a visual
indicator of measured intensity of the subsequently polarized light
in one or more of the plurality of planes.
18. The method of claim 17, wherein the visual indicator includes a
curve of measured intensity of the subsequently polarized light in
one or more of the plurality of planes.
Description
RELATED APPLICATION(S)
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/936,437 filed on Nov. 7, 2007, now
Publication No. US 2008-0117420 published on May 22, 2008, and
entitled Method and Apparatus for Determining Concentration Using
Polarized Light (Attorney Docket No. 113067.00012 F57), which
claims priority from U.S. Provisional Patent Application Ser. No.
60/857,392, filed on Nov. 7, 2006, and entitled Apparatus and
Method for Determining Glucose Concentration Using Polarized Light
(Attorney Docket No. DEKA-003XX), all of which are herein
incorporated by reference in their entireties.
FIELD OF THE DISCLOSURE
[0002] The present disclosure relates to determining concentration
of chiral molecules in a fluid, and more particularly to
determining concentration of chiral molecules in a fluid using
polarized light.
BACKGROUND
[0003] There are multiple reasons to detect the concentration of a
compound in a solution. One reason for detecting concentration may
be to ensure proper mixing of multi-component solutions. In order
to increase the shelf life of a solution, in some circumstances,
the various components may, for example, be kept in different
chambers of a multi-chamber solution bag. The seal between the two
chambers is then broken, mixing the various components. The
concentration of the mixed solution can be used as an indicator to
ensure that the chambers have been properly mixed.
[0004] Additionally, online mixing of two concentrations of a
solution may be carried out to achieve a desired concentration.
Automatically detecting the concentrations of solutions as well as
creating and verifying a desired concentration, may allow for
customized concentrations of solutions to be created, for example,
without necessitating a premixed solution having the desired
concentration. The ability to detect the available concentrations
and to mix different concentrations may be used in a number of
different applications.
[0005] In various additional circumstances, the concentration of
glucose in a solution, or determination of the mere presence of
glucose may be desired.
SUMMARY OF DISCLOSURE
[0006] In a first implementation an apparatus includes a first
polarizer configured to polarize light substantially in a first
plane. A second polarizer is configured to polarize light in a
plurality of planes, at least one of the plurality of planes being
different from the first plane. The apparatus further includes one
or more receivers capable of measuring an intensity of incident
light transmitted through the first polarizer and through the
second polarizer.
[0007] One or more of the following features may be included. The
apparatus may include a light source capable of providing light
incident upon the first polarizer, the light incident upon the
first polarizer may be substantially randomly polarized. The
apparatus may also include a fluid chamber, at least a portion of
the fluid chamber may be at least partially disposed between the
first polarizer and the second polarizer. The fluid chamber may
include an at least partially transparent fluid line configured to
allow a fluid containing a concentration of chiral molecules to
flow through the fluid chamber. The chiral molecules may include
glucose molecules.
[0008] The second polarizer may include a polarizer array including
one or more polarizing elements. Each of the one or more polarizing
elements may be configured to polarize light substantially in a
respective single plane. Each of the respective single planes may
be different from one or more of the other of the respective single
planes. The second polarizer may include a gradient polarizer
configured to polarize light in a plurality of different
planes.
[0009] At least one of the one or more receivers may be capable of
measuring an intensity of light in one or more of the plurality of
planes. The receiver may include a linear receiver array.
Additionally/alternatively the receiver may include one or more
individual receivers, at least one individual receiver associated
with each of the plurality of planes.
[0010] According to a second implementation, a method includes
polarizing light in substantially a first plane to provide
initially polarized light, and transmitting the initially polarized
light through a fluid chamber. The initially polarized light
transmitted through the fluid chamber is polarized in a plurality
of planes, at least one of the plurality of planes being different
from the first plane, to provide subsequently polarized light. An
intensity of the subsequently polarized light is measured in one or
more of the plurality of planes.
[0011] One or more of the following features may be included. A
fluid containing a concentration of chiral molecules may be
provided in the fluid chamber. The chiral molecules may include
glucose molecules.
[0012] The method may include measuring an intensity of the
subsequently polarized light when the fluid chamber does not
contain the fluid and measuring an intensity of the subsequently
polarized light when the fluid chamber contains the fluid. A
measured intensity of the subsequently polarized light when the
fluid chamber does not contain the fluid and a measured intensity
of the subsequently polarized light when the fluid chamber contains
the fluid may be compared. The concentration of the chiral
molecules may be determined based upon, at least in part, a
difference in the measured intensity of the subsequently polarized
light when the fluid chamber does not contain the fluid and the
measured intensity of the subsequently polarized light when the
fluid chamber contains the fluid.
[0013] The method may further include providing a visual indicator
of measured intensity of the subsequently polarized light in one or
more of the plurality of planes. The visual indicator may include a
curve of measured intensity of the subsequently polarized light in
one or more of the plurality of planes.
[0014] The details of one or more implementations are set forth in
the accompanying drawings and the description below. Other features
and advantages will become apparent from the description, the
drawings, and the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a diagrammatic view of a concentration determining
apparatus;
[0016] FIG. 2 is a flow chart of a method for determining the
concentration of chiral molecules using the concentration
determining apparatus of FIG. 1;
[0017] FIG. 3 diagrammatically depicts a polarizer array that may
be used in connection with the concentration determining apparatus
of FIG. 1;
[0018] FIG. 4 diagrammatically depicts a gradient polarizer that
may be used in connection with the concentration determining
apparatus of FIG. 1; and
[0019] FIG. 5 shows a plot of relative intensity versus
polarization plane angle for various rotational angles of initially
polarized light.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] Referring to FIG. 1, there is shown concentration
determining apparatus 10 for determining the concentration of
chiral molecules in a fluid using polarized light. Concentration
determining apparatus 10 may include first polarizer 12 configured
to polarize light substantially in a first plane. Concentration
determining apparatus 10 may additionally include second polarizer
14 configured to polarize light in a plurality of planes, with at
least one of the plurality of planes being different from the first
plane. Additionally, concentration determining apparatus 10 may
include one or more receivers (e.g., receiver 16) capable of
measuring an intensity of light transmitted through first polarizer
12 and second polarizer 14.
[0021] Fluid chamber 18 capable of containing a fluid including a
concentration of chiral molecules may be disposed relative to first
polarizer 12 and second polarizer 14, such that at least a portion
of fluid chamber 18 is at least partially disposed between first
polarizer 12 and second polarizer 14. A concentration of the chiral
molecules included within the fluid may be determined based upon,
at least in part, an intensity of the light measured by the one or
more receivers (e.g., receiver 16).
[0022] Light source 20 may be capable of providing generally
randomly polarized light incident upon first polarizer 12.
Continuing with the above-stated example, and referring also to
FIG. 2, first polarizer 12 may polarize 50 light from light source
20 in substantially a first plane (e.g., in the horizontal plane,
as shown in FIG. 1) to provide 52 initially polarized light 22.
First polarizer 12 may include any known linear polarizer, such as
a polarized film, a polarizing filter, or the like. Initially
polarized light 22 transmitted from first polarizer 12 may be
transmitted 54 through at least a portion of fluid chamber 18.
Second polarizer 14 may polarize 56 initially polarized light 22
transmitted 54 through fluid chamber 18, in a plurality of planes.
At least one of the plurality of planes may be different than the
first plane (e.g., may be a plane other than the horizontal plane
of initially polarized light 22). As such, second polarizer 14 may
provide 58 subsequently polarized light 24. Subsequently polarized
light 24 may include light polarized in the plurality of planes.
That is, subsequently polarized light 24 may include components of
initially polarized light 22 oriented in each of the plurality of
planes provided by second polarizer 14. Subsequently polarized
light 24 associated with each of the plurality of planes may be at
least partially spatially separated from subsequently polarized
light 24 associated with each of the other planes of the plurality
of planes.
[0023] Referring also to FIG. 3, second polarizer 14 may include
polarizer array 100. Polarizer array 100 may include one or more
individual polarizing elements (e.g., polarizing elements 102, 104,
106, 108, 110, 112, 114, 116). Each of polarizing elements 102,
104, 106, 108, 110, 112, 114, 116 may be configured to polarize 56
initially polarized light 22 substantially in a respective single
plane. Each of the respective single planes may be different from
one or more of the other respective single planes. For example, as
shown, each of polarizing elements 102, 104, 106, 108, 110, 112,
114, 116 may have a polarization plane (e.g., diagrammatically
indicated by the bisecting line of each polarizing element 102,
104, 106, 108, 110, 112, 114, 116) that is different from each of
the other polarizing elements 102, 104, 106, 108, 110, 112, 114,
116. For example, as shown, polarizing element 102 may have a
generally vertical polarizing plane. The polarizing plane of each
of polarizing elements 104, 106, 108, 110, 112, 114, 116 may be
incrementally rotated 22.5 degrees relative to the angularly
adjacent polarizing elements. Of course other incremental
rotational angles, as well as varying numbers of polarizing
elements may be used depending upon preference and design criteria.
Further, one or more of the polarizing elements may
additionally/alternatively have a polarization plane that is the
same as one or more of the other polarizing elements.
[0024] Referring also to FIG. 4, second polarizer 14 may also
include gradient polarizer 150. Gradient polarizer 150, which may
be formed, e.g., via photolithography, or other suitable
techniques, may be configured to polarize light in a plurality of
different planes, diagrammatically represented by polarizing axes
152, 154, 156, 158, 160, 162, 164, 166, 168. Gradient polarizer 150
may include incremental polarization planes, or may include
continuously varying polarization planes. Gradient polarizer 150
may provide a plurality of polarization planes within a small area,
e.g., which may reduce the size of second polarizer 14.
[0025] As mentioned above, subsequently polarized light 24
associated with each of the plurality of planes may be at least
partially separated from subsequently polarized light 24 associated
with each of the other planes of the plurality of planes. In the
example of polarizer array 100, each polarizing element 102, 104,
106, 108, 110, 112, 114, 116 may provide 58 subsequently polarized
light 24 associated with one of the plurality of planes (e.g.,
having a different plane of polarization). As shown, polarizing
elements 102, 104, 106, 108, 110, 112, 114, 116 are at least
partially spatially separated from one another. Subsequently
polarized light 24 associated with each of polarizing elements 102,
104, 106, 108, 110, 112, 114, 116 may be similarly at least
partially spatially separated from one another. In a similar
manner, gradient polarizer 150 may provide subsequently polarized
light 24 associated with each of the plurality of planes (e.g.,
represented by polarizing axes 152, 154, 156, 158, 160, 162, 164,
166, 168) that may be at least partially linearly separated from
subsequently polarized light 24 associated with each of the other
of the plurality of planes.
[0026] Continuing with the above-stated example, the one or more
receivers (e.g., receiver 16) may measure 60 the intensity of
subsequently polarized light 24 in one or more of the plurality of
planes provided by second polarizer 14. The one or more receivers
(e.g., receiver 16) may include a linear receiver array (e.g., a
CMOS sensor array), in which a respective portion of the linear
receiver array may measure 60 the intensity of subsequently
polarized light 24 corresponding to a specified one (or range) of
the plurality of planes. For example, as discussed above, second
polarizer 14 may polarize initially polarized light 22 in a
plurality of planes. A region of a linear receiver array may
measure the intensity of subsequently polarized light 24 associated
with each of the plurality of planes. In a further embodiment, the
one or more receivers may include a separate receiver for each of
the plurality of planes (or a range of the plurality of planes)
provided by second polarizer 14.
[0027] The intensity of the light measured 60 by the one or more
receivers may be based upon, at least in part, the difference
between the angle of the first plane of initially polarized light
22 and the angles of each of the plurality of planes of
polarization provided by second polarizer 14. Generally, an angular
difference between the first plane and a respective one of the
plurality of planes provided by second polarizer 14 approaching 90
degrees may provide a lower measured 60 intensity associated with
the respective one of the plurality of planes. The intensity of the
measured light 60 associated with one of the plurality of planes
provided by second polarizer 14 may be given by:
M.sub.post=M.sub.prek|cos(.theta. diff)|
[0028] wherein M.sub.pre is the magnitude of the intensity of
initially polarized light 22, M.sub.post is the magnitude of the
intensity of subsequently polarized light 24 associated with the
respective one of the plurality of planes provided by second
polarizer 14, k is an attenuation factor of second polarizer 14,
e.g., which may account for losses during transmission of initially
polarized light 22 through second polarizer 14, and .theta. diff is
the angular difference between the first plane and the respective
one of the plurality of planes provided by second polarizer 14.
Accordingly, a maximum intensity may be measured 60 when .theta.
diff is equal to zero degrees, and a minimum intensity may be
measured 60 when .theta. diff is equal to 90 degrees.
[0029] As mentioned above, at least a portion of fluid chamber 18
may be at least partially disposed between first polarizer 12 and
second polarizer 14. Fluid chamber 18 may include an at least
partially transparent fluid line configured to allow a fluid
containing a concentration of chiral molecules to flow through
fluid chamber 18 (e.g., via inlet 26 and outlet 28). Additionally,
the at least partially transparent fluid line may allow for the
transmission 54 of initially polarized light 22 through fluid
chamber 18 and any at least partially transparent fluid contained
therein. Fluid chamber 18 may be a disposable component, e.g.,
associated with a fluid source (not shown) and/or a fluid delivery
system (also not shown). Concentration determining apparatus may
allow optical detection of the concentration of the chiral
molecules. As such, the concentration of the chiral molecules may
be determined without direct contact with the fluid.
[0030] An example of a chiral molecule may include, but is not
limited to, glucose. For example, the fluid may include a dialysate
including glucose. Based upon, at least in part, the chirality of
glucose, polarized light (e.g., initially polarized light 22)
transmitted 54 through the dialysate may be rotated by the glucose.
The angle of rotation of the polarized light may vary generally
linearly with the length of the path of the polarized light through
the fluid and the concentration of the chiral molecule within the
fluid. As such, the concentration of glucose in the dialysate may
be determined based upon, at least in part, the length of the path
through the dialysate and the angular rotation of polarized light
passing through the dialysate. The relationship between the angle
of rotation, the length of the path of the polarized light and the
concentration of the chiral molecule in the fluid may be given
by:
.phi.=.alpha..sub..lamda.LC
wherein .phi. is the angle of rotation of the polarized light,
.alpha..sub..lamda. is the specific rotation for the chiral
molecule at wavelength .lamda., L is the path length of the
polarized light, and C is the concentration of the chiral molecule
within the fluid. The above equation may be similarly applicable to
other fluids containing chiral molecules.
[0031] Continuing with the above stated example of a dialysate
including glucose, glucose may be dextrorotatory. As such, light
may be rotated in a right-handed direction when passing through a
fluid including glucose. Additionally, the specific rotation may
increase as the wavelength of the light decreases. Therefore light
with shorter wavelengths may be rotated a greater angle for a given
path length through the fluid having a given concentration of
glucose. As an example of the specific rotation of glucose, for a
wavelength of .lamda.=589 nm, .alpha..sub..lamda.=52.6.degree.
ml/(dm g). Accordingly, in one embodiment light source 20 may be,
e.g., an LED providing substantially randomly polarized light
having an approximate wavelength of 589 nm. Of course, other
wavelengths may additionally be used depending upon design criteria
and preference. Specific rotation may be determined for the
wavelength of light source 20, allowing concentration of glucose to
be calculated based upon the specific rotation for the wavelength
used, the path length through the glucose, and the angle of
rotation of polarized light passing through the glucose.
[0032] Based upon, at least in part, the specific rotation of the
chiral molecules included within the fluid, the path length through
the fluid, and an angle of rotation of polarized light passing
through the fluid, the concentration of the chiral molecules
included within the fluid may be determined according to the
above-described relationship. As also discussed above, the angle of
the plane of initially polarized light 22 incident upon second
polarizer 14 (e.g., after being transmitted 54 through fluid
chamber 18) may be determined based upon, at least in part, the
measured 60 intensity of the subsequently polarized light in the
plurality of planes. The angle of rotation of polarized light
passing through the fluid including a concentration of chiral
molecules may be determined, at least in part, by comparing 62 the
intensity of the subsequently polarized light 24 in the plurality
of planes when fluid chamber 18 does not contain the fluid
including a concentration of chiral molecules and the intensity of
the subsequently polarized light 24 when fluid chamber 18 does
contain the fluid including a concentration of chiral molecules
(resulting in rotation of initially polarized light 22 transmitted
through fluid chamber 18).
[0033] Continuing with the above-stated example, measuring 60, by
the one or more receivers, the intensity of subsequently polarized
light 24 in the plurality of planes provided by second polarizer 14
may include measuring 64 the intensity of subsequently polarized
light 24 in the plurality of planes when fluid chamber 18 does not
contain the fluid including a concentration of chiral molecules and
measuring 66 the intensity of subsequently polarized light 24 in
the plurality of planes when fluid chamber 18 does contain the
fluid including a concentration of chiral molecules (e.g., by
causing the fluid to flow through fluid chamber 18 via inlet 26 and
outlet 28).
[0034] The concentration of the chiral molecules may be determined
68 based upon, at least in part, a difference in the measured 64
intensity of subsequently polarized light 24 when fluid chamber 18
does not contain the fluid and the measured 66 intensity of
subsequently polarized light 24 when fluid chamber 18 contains the
fluid. Referring also to FIG. 5, determining 68 the concentration
of the chiral molecules included within the fluid may include
providing a visual indicator of measured 60 intensity of
subsequently polarized light at one or more of the plurality of
planes. For example, plot 200 may correlate the relative intensity
of subsequently polarized light 24 to the angle of each of the
plurality of planes. Curve 202 may be fit to the measured 64
intensity of subsequently polarized light of each of the plurality
of planes when fluid chamber 18 does not include the fluid. The
peak of curve 202 may correspond to the angle of initially
polarized light 22 incident upon second polarizer 14 (e.g., after
passing through fluid chamber 18 when fluid chamber 18 does not
contain the fluid including chiral molecules).
[0035] In a similar manner, curves 204, 206, 208, 210, and 212 may
correspond to rotation angles of 5, 10, 15, 20, and 25 degrees of
initially polarized light 22 relative to second polarizer 14 (e.g.,
as may occur when initially polarized light 22 passes through the
fluid including chiral molecules of increasing concentration, when
fluid chamber 18 does contain the fluid including a concentration
of chiral molecules). As with curve 202, the peak of curves 204,
206, 208, 210, and 212 may correspond to the angle of initially
polarized light 22 incident upon second polarizer 14, e.g., as may
occur after passing through fluid chamber 18 when fluid chamber 18
does contain the fluid including a concentration of chiral
molecules. The offset of curves 204, 206, 208, 210, 212 relative to
curve 202 may indicate the angle of rotation of initially polarized
light 22, for example as may be imparted by the fluid including a
concentration of chiral molecules. As discussed above, the
concentration of chiral molecules included within the fluid may be
calculated based upon the path length of initially polarized light
22 through the fluid including chiral molecules and the angle of
initially polarized light 22 incident upon second polarizer 14
after passing through fluid including a concentration of chiral
molecules (e.g., as compared to the angle of initially polarized
light 22 incident upon second polarizer 14 after passing through
fluid chamber 18 not containing the fluid including a concentration
of chiral molecules).
[0036] According to one aspect, concentration determining apparatus
10 may be calibrated, e.g., to account for any gain associated with
the one or more receivers. For example, un-polarized (e.g.,
randomly polarized) light incident on second polarizer 14 may
produce subsequently polarized light 24 having a generally equal
intensity in each of the plurality of planes. The one or more
receivers (e.g., receiver 16) may measure 60 the intensity of
subsequently polarized light 24 (resulting from non-polarized light
incident on second polarizer 14) in each of the plurality of
planes. A gain factor may be determined for each of the one or more
receivers (e.g., for each of the plurality of planes) so that the
measured intensity for each of the plurality of planes may be
adjusted to provide a generally uniform measured intensity in each
of the plurality of planes. The gain factor determined for each of
the one or more receivers may be applied to measured 60 intensities
for each respective one of the one or more receivers to factor out
the gain associated with each of the one or more receivers.
[0037] A number of implementations have been described.
Nevertheless, it will be understood that various modifications may
be made. Accordingly, other implementations are within the scope of
the following claims.
* * * * *