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TITLE OF THE INVENTION
PORTABLE APPARATUS FOR DETECTING THE
TRANSMITTANCE AND LUMINESCENCE OF A SAMPLE
FIELD OF THE INVENTION
The present invention relates to apparatuses for detecting
transmittance and luminescence of samples. More specifically, the present
10 invention is concerned with such an apparatus that is portable.
BACKGROUND OF THE INVENTION
The quantization of a particular material is useful in diverse
field of technology such as biology, biochemistry, chemistry and material
science. Two of the more well known techniques for material quantization
are photometry and fluorometry.
In photometry, a beam of light is directed toward a sample
of the material to be quantified, and the amount of light absorbed by the
material as the light passes through it is measured to quantify the material.
Fluorimetry, in contrast to photometry is based on the
phenomena whereby a material emits the light of a characteristic
25 wavelength when it is properly excited. A fluorometer must be able to
clearly differentiate the light which is emitted as fluorescence by the
sample material from the light which is used to excite the material into its
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fluorescence. Photometers and fluorometers do have some
commonalities.
An example of an apparatus for testing biological samples
is described in the United States Patent No. 5,925,884, issued on
July 20, 1999 and naming Robinson ef al. as the inventors.
A first drawback of such apparatuses is that they are
relatively bulky. Moreover, their overall design and, more specifically, their
optical assemblies are often complex and breakable. These two
drawbacks prevent such apparatuses from being readily portable.
BRIEF DESCRIPTION OF THE DRAWINGS
In the appended drawings:
Figure 1 is a perspective view of a portable apparatus for
detecting the fluorescence and the transmittance of a biological sample,
according to an embodiment of the present invention, illustrated with a
20 sample dish;
Figure 2 is an exploded view of the apparatus of Figure 1;
Figure 3 is a front elevational view of one of the two
symmetrical portions of the apparatus of Figure 1; and
Figure 4 is a sectional view taken along line 4-4 of Figure 1.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Figures 1 to 4 of the appended drawings, a
portable apparatus 8 for detecting the fluorescence and the transmittance
of a sample contained in a sample dish 12, according to a preferred
embodiment of the present invention, will be described.
The apparatus comprises a body 10, two light emitters in the
form of two LEDs (Light Emitting Diodes) 14 and 16, two fluorescence
detectors 18 (see Figure 4) and a transmittance detector 20. The device
8 is to be connected to a controller (not shown), an input means (not
shown), and a display device (not shown).
The body 10 includes a central bore 22 for receiving a
sample dish 12 in a snuggly manner. A portion of the bore 22, near its
distal end 24, has an H-shaped cross-section. The rest of the bore 22 has
a rectangular cross-section.
The central bore 22 allows to receive either a sample dish
12 having a portion with an H-shaped cross-section (as illustrated in
Figures 2 to 4), or a sample dish having a continuous rectangular cross-
section.
It is to be noted that the shape and size of the bore 22 may
be modified to accommodate sample dishes having other geometry,
without departing from the spirit and nature of the present invention.
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The body 10 further includes two recesses 26 and 28
configured to receive the two LEDs 14 and 16. Each of the two recesses
26 and 28 has a section advantageously complementary to LEDs 14 and
16 respectively. This allows to secure the LEDs 14 and 16 in the recesses
26 and 28 without requiring any securing means.
The two recesses 26 and 28 are so advantageously
positioned as to orient the two LEDs 14 and 16 in a direction pointing
towards a virtual point 30 (see Figures 3-4) located in the middle of the
bore, facing the two emitters 14 and 16.
Each of the two recesses 26 and 28 terminates in a small
passage 32 that provides a window for the light to be emitted by the two
LEDs towards the virtual point 30.
The body 10 also comprises two lateral detector receptacles
34 in the form of two facing recesses in the body 10, and a central
detector receptacle 36, also in the form of a recess in the body 10.
The two lateral detector receptacles 34 and the central
receptacles 36 terminate in small respective passages 38 and 40 that
allow the detectors 18 and 20 to collect photons from the sample in the
sample dish 12 along a preferred axis intersecting the virtual point 30.
Moreover, the receptacles 34 and 36 are also so positioned
to advantageously yield the same distance from the detectors 18 and 20
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to the virtual point 30.
The body 10 is preferably made of a light material such as
DeIrinT"". Obviously, other materials, such as aluminium may also be
5 used.
The body 10 advantageously comprises two symmetrical
portions 42 and 42' that are removably secured together using screws (not
shown). For that purpose, the portions 42-42' include three opposite
apertures 44 for receiving the screws. Alternatively, other securing means
such as cement may also be used to secure the two portions 42-42'
together.
The fact that the body 10 comprises two parts is
advantageous, since it allows opening of the body 10 for easy access for
maintenance to the emitters 14 and16 and to the detectors 18 and 20. It
also allows for easy assembly of the apparatus 8.
Optionally, the apparatus 8 may include a cover (not
shown) to protect the emitters 14 and 16 and the detectors 18 and 20
during transportation of the apparatus 8. For that purpose, the body 10
advantageously includes two shoulders 46 on which a box-like cover (not
shown) may rest.
The two LEDs 14 and 16 are so advantageously chosen as
to provide incident light having a wavelength that allows to excite a sample
containing natural pigments or doped with a dye such as rhodamine,
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fluorescein and Texas RedT"" .
According to a preferred embodiment of the present
invention, the DELs 14 and 16 emit between 325 nm and 800 nm lights.
For example, the following DELs may be used:
~ No. LNG992CFBW by Panasonic (AID 30 nm, 1500
mcd); and
~ No. E903 by GiIwayT'"' (~I~ 25 nm, 4000 mcd).
As will be explained below, input means, preferably in the
form of selector switches, allows to select one of the two emitters 14-16,
or no emitter (for luminescence measurement).
Obviously, other light emitters may also be used depending
on the application.
In order to allow sufficient light onto the sample, the body 10
has been configured so as to allow the emitters 14 and 16 to be positioned
very closely to the sample when the sample dish 12 is correctly positioned.
The controller, to which the emitters 14 and 16 are advantageously
connected, is also configured so as to provide sufficient input current to
the emitters 14 and 16 depending on the desired sensitivity.
The two fluorescence detectors 18 are advantageously in
the form of photodiodes, such as Burr-Brown's No. OPT21. This particular
diode has the following specifications:
~ Sensitivity of 0.45 A/W (400-1100 nm);
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~ Detection area of 5,2 mm2; and
~ Conversion rate of 2x108 V/A.
Such a detector has a sensitivity of 5.5x10' photons/s/mm2 with a
saturation of 1.1x10'°photons/s/mm2for a wavelength of 520 nm.
The use of two fluorescence detectors advantageously
allows to increase the sensitivity by a factor of 2. Indeed, according to a
preferred embodiment of the present invention, the controller includes an
adder function that allows average readings from the two detectors 18. For
that purpose, the two fluorescence detectors 18 are positioned at an equal
distance from the emitters 14 and 16 and also from the virtual point 30.
Alternatively, a single fluorescence detector may be used.
The two fluorescence detectors 18 are advantageously
positioned relative to the emitters 14 and 16 so as to maximize the
fluorescence light input to the sample, while rejecting the excitation signal,
without requiring the use of a colored filter or a monochromator. This is
advantageous since it allows to simplify the apparatus and also minimize
its size.
The transmittance detector 20 is advantageously in the form
of a photodiode. Again, a Burr-Brown's No. OPT21 is used with the same
specifications as listed above but with a conversion rate of 5x105 V/A.
Such a detector has a sensitivity of 2.2x10'° photons/s/mm2
with a saturation of 4.5x10'2photons/s/mm2for a wavelength of 520 nm.
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Alternatively, other transmittance detectors may also be
used without departing from the spirit and nature of the present invention.
The transmittance detector 20 is advantageously positioned
at 180 degrees from the incident light coming from the emitters 14 or 16.
It is advantageous to use sample dishes 12 that minimize
the reflection of light onto their wall, such as those made of quartz, glass
and polystyrene. Also, it has been found that the use of dishes made of
methacrylate allows minimization of the reflection of aqueous samples.
Dishes made of quartz, glass and polystyrene also allow minimization of
the reflection.
The controller (not shown) may be in the form of a
programmed chip or electronic circuits. A conventional personal
computer, to which the detectors 18 and 20 and the emitters 14 and 16
are to be connected, may also be used to control the operation of the
apparatus 8.
The controller is so programmed to activate the emitters 14
and 16 and to selectively collect signals from the detectors 18 and 20.
The emitters 14 and 16 and the detectors 18 and 20 are
connected to the controller via cables or other connecting means.
The controller is further configured to allow detection of
inhomogeneities in the sample. Indeed, the controller is configured to
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calculate the difference between the signals coming from the two
fluorescence detectors 18, to use this difference to search for
inhomogeneities in a sample, and to trigger an alarm if such an
inhomogeneity is detected. Alternatively, the dish containing the sample
may be rotated if there is only one fluorescence detector. A further step
could the characterization of a detected inhomogeneity.
The controller is also further configured to detect saturation
in the signals coming from one of the detectors 18 and 20, and to trigger
an alarm accordingly.
The display device (not shown) may take many forms
including: a dot matrix LED display, a digit display, a liquid crystal
display,
or a computer monitor. The display device allows to visualize the
measurement of any one of detectors 18 and 20, or of a value computed
by the controller using one of the measurements. The selection is made
by the user via the input means (not shown).
The apparatus 8 further comprises a portable electrical
source (not shown), advantageously in the form of rechargeable batteries.
Alternatively or additionally, the controller may be provided with a power
adapter allowing to connect the apparatus 8 to a power network.
In the case where the apparatus 8 includes a portable
electrical source, the controller may advantageously be so configured with
a timer function that would automatically deactivate the apparatus 8 after
predetermined inactivity period. The controller can also be equipped with
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a monitor to allow detecting power failures or power variations.
An apparatus, according to the present invention, allows to
measure luminescence, transmittance and fluorescence of a biological
5 sample.
The controller is further configured to use the measured
luminescence, transmittance and/or fluorescence and known algorithms
to determine an approximate account of the concentration of a
10 predetermined biological agent in a biological sample.
The sensitivity of the apparatus 8 is, for example, in the
range of 5 ng/ml for rhodamine 6G. This sensitivity is obtained through a
900 Hz modulation, band-pass filtering (54 dB/decade) and demodulation
via an RMS function. The controller is configured to provide the above-
described mode of operation.
The sensitivity may be increased by using avalanche
photodiodes as detectors 16 or 18.
It is believed to be within the reach of a person skilled in the
art to modify the configuration and geometry of the body 10 so as to allow
for its utilization with dishes having other geometry.
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
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