Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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APPARATUS FOR MEASUREM~NT OF
B OOD BILIRUBIN CONCENTR~TION
sackground of the Invention
This invention relates -to testing of blood serum samples
for measuremen-t of bilirubin concentration. More par-ticularLy,
the invention is a novel apparatus for performing such measurement.
The general testing method used herein involves directing
a beam of light through a blood sample, then along parallel
optical paths through a narrow band pass fi:Lter, ~60 nm in one path
and 550 nm in the other path, then to compare the light trans-
mittance or attenuation in the two optical paths as an indication
of bilirubin concentration in the blood sample. This method is
more fully described in United States Patent ~3569721 to Goldberg
and Polanyi.
Goldbery and Polanyi also disclose an apparatus for
performing their test method. I-t is an optical system including
light source and condenser Eor transilluminating a blood sample,
collimating optics for light transmitted by the sample, and a
beam divider to create parallel optical paths. A 461 nm band
pass filter in one path and a 551 nm band pass filter in the other
path transmit light to respective photodetectors which are in
turn connected to a galvonometer to indicate balance or imbalance
of the intensity of light transmitted along the two optical paths.
A variable aperature in the path of light to the 551 nm filter
adjustably attenuates the light transmission in that path. This
variable aperture is calibrated to indicate bilirubin concentration
when its setting is such that the galvonometer is at a null
condition. Adjustment of the variable aperture to reach a null
condition is manual.
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Summary of the Invention
It is an object of the present invention to provide
a bilirubin measurement apparatus to perform ~he general
bilirubin test method described and which operates auto-
matieally to reaeh a null condition for a readout.
Briefly, the present invention can be summarized as
an eleetro-optieal system including light source and condenser
for transilluminating a blood sample, collimating optics for
light transmitted by the sample, and a beam divider to create
parallel optical paths. A 460 nm band pass filter is in one
optieal path whieh then leads to a first photo detector, in turn
operatively eonneeted by suitable eireuitry to a motor. A 550 nm
band pass filter is in the other optical path from the beam
divider whieh path then leads to a second photo detector, in turn
operatively conneeted by suitable circuitry to the same motor.
movable gradient density filter or optical wedge in the path
of the 550 nm filter is operatively eonnected to-the motor and
movable by the motor to a position in the light path to achieve a
null eondition when light intensity at both photo deteetors is in
balance. The null position of the optieal wedge is eorrelated
to a readin~ of bilirubin coneentration in the sample.
In a more specific aspect the invention provides a
system for measuring the concentration of bilirubin in a test
sample of blood serum, including: a light source to direct
light along an optical axis to illuminate a test station, a
sample handling system for presentation of test samples of blood
serum at the test station, the sample holding system ineluding,
a sample holder adapted to hold a blood sample placed thereon
and movable relative to the optical axis in a defined locus
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be~ween a reference position in which the sample is out of the optical axis,
~nd a -test position in which the sample is on the optical axis at the tes-t
station, and the sample holder forming a reference aperture and a test
aperture which are sequentially positioned at the test station when the
sample holder is at its r.eference and test positions respectively, an
objective lens to project light further àlong the optical axis from the test
. station, a beam divider disp~sed on the optical axis to receive light Erom
the objective lens and to partially reflect and partially transmit same along
parallel optical paths, a band pass filter in each of the parallel optical
paths to transmit substantially only light of one wavelength, a photodetector
behind the band pass filter in each of the parallel optical paths to receive.
light trc~nsmitted thereby, an adjustable light attenuator in one oE the
parallel optical paths for adjustably varyin~ the intensity of light trans-
mitted therethrough to the associated ~hotodetector, the photodet.ectors
electrically connected to a carriage motor which is responsive to any i~balance
`. in the signals from the photodetectors to move the li.ght attenuator to a
position at which the photodetector signals to the motor.are in balance, the
resulting position of the light attenuator being correlated to bilirubin
concentration in the test sample.
The det~ils, operation and benefits of the present invention,
will now be described more s~ecifically with reference to the accompanying
drawing.
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Figure 1 is a plan view of the system of this invention, partly
in section.
Figure 2 is a sectional elevation taken along the line II-II
of Figure 1.
Figure 3 is a detail elevation taken along the line III-III of
. Figure 1.
Figure 4 is an eleva-tion view of a detail of the sysbem.
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Figure ~ is a sectional plan view of the dPtail of
Figure 4, taken along the line V-V o~ Figure 4.
Description
Figure t shows the system of this invention, in plan
view, supported on a frame generally indicated at 2. A light
source 4, a condenser lens 6, a ~irst re~lector 8, a second
reflector 10, and an objective lens 12 are disposed on an
optical axis 14. From objective lens 12 onward, the optical
system is best seen with reference also to Figure 2 and in-
cludes a beam divider 16 which divides the optical axis 14
into parallel optical paths 14r and 14t. The term "parallel"
is used herein to describe optical paths in the same sense as
"parallel" electric circuits and the like, and not in the geo-
metric sense to denote spatial parallelism.
Beam divider 16 is shown in Figure 2 supported by, and
depending from, frame 2 which is actually above the system,
all the elements described han0 from frame 2 above. The r~
ected optical path 14r leads ~rom beam divider ~6 through a
460 nm band pass filter 18 to a first photo detector 20. Trans-
mitted optical path 14t leads rom beam divider 16 through a
550 nm band pass filter 22 to a second photo detector 24.
A pair of parallel guide rails 26 are stationarily
mounted to the frame 2 and extend forward and back to slidably
support a carriage member 28 thereon. Carriage member 28 is
mounted for æliding back and forth, in the directions indicated,
on rails 26 by suitable Y-blocks or the like at 30, Carriage
member 28 carries an optical filter wedge 32 for movement of
wedge 32 relative to the optical path 14t. Wedge 32 is, in
essence, a filter elemen. having a gradient density from one
end to the other so that by moving it a~ross the optical path
14t, transmission along path 14t is varied. Wedge 32 is cali-
brated from end to end so that its lateral position relative
to the optical path 14t is correlated to its light attenuation
at that position.
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Carriage 28 is connected at 34 to a drive beltlwhich
in turn is mounted on suitable pulleys 38 and connected by a
drive pulley 39 to a carriage drive motor 40. Motor 40 is a
reversible stepper motor, operatively connected to the elec-
trical outputs from photo detectors 20 and 24 so that an im-
balance in the signals from the two photo detectors 20 and 24
signals the motor 40 to move carriage 28 and optical wedge 32
to a null position in which the equal or balanced signals
from the photo detectors mean that light intensities through
the 460 nm filter and the 550 nm filter are equal~ A normally
closed limit switch 42 is frame-mounted and positioned in the
way of the travel of carriage 28 at each end point of its tra-
vel. As an equipment protective measure, when either switch
42 is abutted by the carriage 28, the drive circuit is broken
and motor and carriage stopped. Switches 42 are electrically
connected to the motor 40 though this is not shown in the
drawing.
A blood sample handling system is also shown in Figure
1 and is mounted to framè 2. A sample drive motor 50, which
is a reversible stepper motor, is operatively connected at its
output shaft 52 to a sample holder shaft 54 which extends
through and is supported for rotation by a housing 56. A sam-
ple holder assembly 58 is fastened for rotation on shaft 54.
Sample holder 58 is shown in detail in Figures 4 and 5. The
end of shaft 54 supports a cam 6Q which is operatively connec-
ted to a limit switch 62 which is in turn electrically connec-
ted to sample drive motor 50. The cam 60, limit switch 62
interaction can be more clearly seen in Figure 3 in which the
switch 62 is open and the sample drive motor 50 therefore op-
erative. Housing 56 includes a pair of apertures 64 to trans-
mit light along the optical axis 14.
The sample holder assembly is shown in a rest or refer-
ence position to receive a blood sample. In this position, a
re~erence aperture 66 in the holder assembl~ is in line with
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apertures 64 of the housing and passes lightr unmodified by
a blood sample, from the light source 4 to the photo detectors
20 and 24~ This permits calibration, or a check on calibra-
tion, of the instrument prior to every actual blood sample
S measurement.
Referring now to Figures 4 and 5 particularly, sample
holder 58 includes a sample insert/re val station 68 in which
a blood sample, typically between two glass plates, is placed
and held by leaf springs 70. The sample holder includes a
sample test aperture 72 positioned to direct light through
the blood sample when it is in place. Sample holder 58 is
rotatable 90 on shaft 54 to move a blood sample rom its
insert/remo~al position shown to its test position in which
the test aperture 72 is where reference aperture 66 is now
lS shown, i.e. on the optical axis 14. Sample drive motor 50
is connected to a detent switch 74 which coacts with the sam-
ple holder 58 to seat (and thereby close the switch) at each
end of the 90 arc travel of the holder 58.
The operation of the system will now be described
with the sample holder 58 at its Figure 1, Figure 4 position
as a starting point. A reference reading is continually made
in the optical system with light passing through reference
~'~ aperture ~ , carriage motor 40 being energized and always at
or seeking a balance position. A blood sample is inserted in
station 68 and sample drive motor 50 actuated as by a manual
switch. Momentary switch actuation starts the rotation of the
sample holder 58. The consequent unseating and opening of the
detent switch 74 de-energizes carriage motor 40 until the hold-
er reaches its test position in which test aperture 72 is
aligned at the optical axis 14 and the detent switch again
s~ats to energize the carriage motor 40 and stops sample motor
50. While the blood sample is thus in the optical axis, light
transmitting through it to the photo detectors 20 and 24 sig-
nals the carriage motor 40 to position the filter wedge 32 in -
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response to any imbalance in photo detector signals until a
null condition is reached. At this point the desired reading
is made. The manual switch again starts motor 50, this time
in the reverse direction, and again detent switch 74 unseats
and opens to de-energize the carriage motor 40 until the ini-
tial position is reached with reference aperture 66 once
again in the optical axis and the sample holder accessible
for removal of the sample. A~ this po:int, motor 50 stops
when cam 60 actuates limit switch 62.
The foregoing speciication describes the concept of
this invention and the best mode presently contemplated for
practicing the same. The scope of the invention is limited
only by the purview of the ollowing claims.
