Note: Descriptions are shown in the official language in which they were submitted.
.2~h~ 36r7
3 The present invention is directed to the collec-
4 -tion of detectable light sisnals radiating from individually
isolated particulate material, such detectable light signals
6 belng used for the countiny and analysis of particulate
7 materials.
The guantitative measurement, counting and analysis
il o cells and like particulate material have become very
12 'mportan~ parts of biomedical research. Various flow
13 cytometers exlst in the prior art and have been devised to
14 measure a range of cellular substances and properties, with
some of these properties having to be measured on a cell by
16 cell basis. The flow cytometers were improved by incorpo-
17 rating a laminar sheath-flow terhnique, which confines cells
18 to the center of a flow stream, and a laser beam for inter-
19 secting the cell flow, which produces scattered light from
the laser beam and/or fluorescent light from stained cells
21 when the laser beam is at the proper wave lengths. Prior to
22 ~.S. Patent No. 3,946,239, to Salzman et al, the cytometers
23 were inefficient in collecting the scattered and fluorescent
24 light, which made it difficult or impossible, in some cases,
to investigate weakly fluorescing dyes bound to cells and
26 fluorescence from small particles. More specifically, when
27 there is inefficient collection of light, measurements of
28 weak signals are made difficult due to the poor signal to
29
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7~3~,7
1 noise ratio. TAe efficiency of light collection was
2 improved by the ellips~oidal reflection chamber of U.S.
3 Patent ~o. 3,946,239. As disclosed in "The Journal of
4 Histochemistry and Cytochemistry", Volume 25, No. 7, page
784, the flow chamber of U.S. Patent No. 3,946,239 collects
6 about sixty percent of the total cell fluorescence.
7 Although this particular device made an improvement in
8 efficiency of collecting scattered light and fluorescence,
g there are several inherent problems still remaining with the
prior art as it has progressed up to and through U.S. Patent
11 No. 3,946,239, as will be discussed below.
12 First, in ~.S. Patent No. 3,946,239, most of the
13 light that proceeds past the second focal point of the
14 ellipsoidal flow chamber without any reflection off the
ellipsoidal surface is lost for the purposes of collection.
16 More specifically, the utilization of the end of the ellip-
17 soid flow chamber for the placement of the conical re-
18 flector decreases the total elliptical surface available
19 for reflection and therefore decreases the collection angle
and efficiency of the chamber. In addition, light reflect-
21 ing off of the end of the ellipsoidal chamber converges at
22 an extremely wide angle relationship relative to the center
23 axis of the conical reflector, resulting in extremely
24 inefficient use of the reflected light. Part of this
inefficient use of light is due to multiple reflections of
'~ the light within the conical reflector~ The decrease in
~i collection angle and efficiency in turn makes the chamber
28 more sensitive to asymmetric particle orientation in the
29
--3--
1 ~low system, as well as lessening the ability to analyze
2 weak fluorescent particles.
3 Secondly, in U.S. Patent No. 3,946,239, when the
4 light that is converged at the second focal point of the
ellipsoid chamber is collected by the conical reflector,
6 the collected light is neither focused nor collimated and
7 therefore arrives at the photosensitive measuring device in
~ a disorganized manner at many different angles. The non-
g orthogonal approach of the collected light to the photo-
sensitive measuring device reduces the efficiency of the
11 photosensitive device and its filters in that such devices
12 are best suited to light impinging orthogonally on their
13 surfaces. ~loreover, due to the light being disorganized,
14 conventional means, such as lenses, for creating more ortho-
gonal light cannot be used with the device of U.S. Patent
16 No. 3,946,237.
17 Thirdly, the orifice of the conical reflector of
18 U.S. Patent No. 3,946,239, which collect the light is suffi-
19 ciently large to allow stray light to be gathered. This
orifice must be larger than the sensing zone ~intersection
21 of stream of particles and the laser beam). Additional
22 width to the orifice is required by the wide angle conver-
23 gence of the light at the second focal point and the extreme
29 eccentricity of the ellipsoidal chamber. In U.S. Patent No
3,946,239 a pinhole orifice would be extremely inefficient,
26 in that positioning would be critical in three dimensions
27 and, if it were not perfectly positioned, practically no
28 light would pass therethrough. This is due primarily to
29
~`~
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B~
1 the light approaching the ~inhole at angles widely different
2 from the normal.
3 The cytometer of U.S. Patent No. 3,946,239,
4 although having a relatively good efficiency, can be
described as being partially "blind". In other words, if
6 light emanating from a particle is hlghly concentrated in
7 some preferred solid half-angle, there is a possibility that
8 it could be missed entirely even though this collector is
g efficient. More specifically, many particles are not
spherical, but behave as combinations of oddly shaped
11 mirrors and lenses, and hence cause "hot spots'' in which
12 large percentages of available light are directed in pre-
13 ferred directions. Consequently, in that this prior art
~ cytometer does not collect light from all possible direc-
tions and collects light extremely inefficienctly in other
16 directions, there exists the possibility of "hot spots"
17 being aimed at a "blind" region. The net result is that
1 a some of the particles will cause some unpredictable percen
19 tage of the light emanating from them to be collected. This
will smear a histogram generated by plotting the number of
21 particles of a ~iven intensity versus that intensity to the
22 left, since many of the particles will appear dimmer than
2~ they actually are. Discrepancies of this magnitude are
24 important. For instance, it is desirable to distinguish
cells with X chromosomes from those ~ith Y chromosomes, but
26 at the present state of the art this is not possible.
27 ` It should also be noted that with the more effi
28 cient gathering of fluorescence and scattered light, the
29
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~7~7
1 less ~vwerful the laser beam needs to be, therefore leading
2 to cos-t savings.
3 Other relevant prior art in_ludes U.S. Patent No.
4 ~,494,693 to Elmer which te~ches the use of coincident axis
for reflecting means in the emission of heat. In addition,
6 U.S. Patent No. 3,989,381 discloses an inefficient light
7 collector.
8 It can readily be seen that there is~
g a need in the industry for a cytometer which is more effi-
cient in collecting scattered light and fluorescence, and is
11 more efficient in impin~ing the collected light on the
12 photosensitive detectors. This increase in efficiency can
13 result in being able to detect signals not previously
1~ detectable above the noise, decreasing the impact of the
shape and orientation of particulate matter in the flow
16 stream by elimlnating "blind" regions, and allowing for
17 lower powered lasers.
1~ According to a first aspect of the invention there
19 is provided:a radiation collector apparatus for analyzing
particulate material wherein irradiation of the particulate
21 material produces a source of detectable radiation,
22 characterized by a reflector chamber having a first reflector
23 surface and a second reflector surface, said first reflector
24 surface substantially having a configuration of a half
portion of an ellipsoid of revolution, said first reflector
26 surface having a primary focus and a secondary focus with
27 one of s'aid foci being positioned within said reflector
28 chamber at the source of detectable radiation, said second
29
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,
1~27i~7
1 reflector surface having any one of a substantially planar configuration
2 and a substantially half portion of an ellipsoid of revolution configuration,
3 a window formed in one of said reflector surfaces and aligned in intersecting
4 relationship with a symmetry axis defined by ~aid primary focus and said
5 secondary focus, said window being dimensioned and configured to provide for
6 a portion of the detectable radia~ion to reflect within said reflector
7 chamber more than once, whereby the detectable radiation emanating from the
8 primary focus proceeds either directly or af-ter one or more reElections
9 through said window.
According to a second aspect of the invention
11 there is provided: a m~thod of collecting detectable
1~ radiation produced by the presence of particulate material,
13 comprising the steps of dividing the detectable radiation
14 emanating from a primary focus o:E a first reflector surface,
having a half portion of an ellipsoid configuration, into at
16 least a first portion of detectable radiation directed
17 toward the first reflector surface and a second portion OL
18 detectable radiation directed toward a second reflector
19 surface in a solid angle subtended by the junction of the
~irst reflector surface and the second reflector surface in
21 a plane of all possible positions of a minor axis of the
~2 first reflector surface, reflecting from the first reflector
23 surfaca the first portion of detectable radiation emanating
24 from the primary focus so that the detectable radiation is
convergent on a secondary focus of the first reflector
26 surface, reflecting from the second reflector surface the
27 second portion of detectable xadiation emanating from the
28 primary focus so that the detectable radiation is convergent
29 on the primary focus of the first reflector surface after
~` ~
~2~37
1 two reflection~, passing the reflected detectable
2 radiation which has reflected at least once off of at
3 least one of the reflector surfaces through a window
4 formed in one of the reflector surfaces.
11
12
13
14
16
17
18 The shortly to be described embodiments of the
19 invention are directed toward a radiation collector
apparatus and method wherein irradiation of particles
21 produces a source of detectable radiation. The radiation
22 collec~or apparatus comprises a reflector chamber having a
23 half ellipsoidal first reflector surface and a second
24 reflector surface. The second reflector surface can take
~he form of a planar reflector sur~ace or a half ellipsoidal
26 reflector surface.
27 In the planar surface embodiments, the first
28 reflector surface has a primary focus and a secundary focus
29
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B6'7
1 defining a symmetry axis with the primary focus being
2 positioned at the source of detectable radiation. The
3 secondary reflector surface is disposed between the primary
4 focus and the secondary focus so that any poin~ on the
second reflector surface is equally spaced from the primary
6 focus and the secondary focus. A window is formed in one
7 of the reflector surfaces and is aligned in intersecting
8 relationship with the sym~etry axis. In operation the
9 detectable radiation emanating from the primary focus
proceeds, either directly or after one or more reflections
11 off of the first reflector surface and/or the second
12 reflector surface, through the window for subsequent
13 processing and analysis. In another embodiment of the
14 present invention a dichroic second reflector surface is
provided. In the embodiments having a second reflector
16 surface in the form of a half ellipsoidal surface, the
17 reflector chamber comprises a stlbstantially ellipsoidal
18 reflector surface with a primary focus and a secondary
19 focus defining a symmetry axis. Centrally positioned on the
symmetry axis is a window formed in the reflector chamber.
21 A source of detectable radiation produced by irradiatin~ the
22 par~icles is disposed at one of the foci o~ the ellipsoidal
23 reflector sur~ace. In operation, the detectable radiation
2~ emanating from one of the foci proceeds either directly or
after one or more reflections through the window in an
26 organized beam to be subsequently analyzed.
27 By way of example only~ illustrative embodiments
28 of the invention will now be described with reference to the
29 accompanying drawings, in which:
7i~
1 FIGURE 1 is a cross-sectional view of the
2 radiation collector apparatus of the present invention
3 taken along a plane passing through the primary focus of the
4 ellipsoidal first reflector surface as depicted by the
sectional lines 1-1 of FIGURE 2.
6 FIGURE 2 is a cross-sectional view of the
7 radiation collector apparatus of the present invention
8 taken along a plane passing through the primary focus of the
9 ellipsoidal first reflector surface as depicted by section
line 2-2 in FIGURE 1.
11 FIGURE 3 is a cross-sectional view of an
12 alternative embodiment of the radiation collector apparatus
13 of the present invention with a dichroic planar second
14 reflector surface taken along a plane passing through the
major axis of the ellipsoidal first reflector surface.
16 FIGURE 4 is a cross-sectional view of another
17 alternative embodiment of the present invention with a
18 window formed in the second re1ector surface taken along a
19 plane passing through the major axis of the ellipsoidal
first reflector surface.
21 FIGURE 5 is a cross-sectional view of another~
22 embodiment of the radiation collector apparatus of the
23 present invention taken along a plane passing through the
24 major axis of the ellipsoidal reflector sur~ace.
26 FIGURE 6 is a cross-sectional view of an ~.
27 alternative embodiment of the present invention taken along
28 a plane passing through the major a~is o the ellipsoidal
29 reflector surface.
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.
6~
2 Referring to FIGURE 1, there is shown a radiation
3 collector apparatus, ~enerally represented by numeral 10,
4 for collecting detectable radiation produced by irradiating
individually isolated particulate material. The radiation
6 collector apparatus 10 comprises a reflector chamber 12
7 having an internal first reflector sùrface 14 and an in-
8 ternal second reflector surface 16. As illustrated in
g FIGURE 1, the first reflector surface 14 has the configu-
ration of a half portion of an ellipsoid of revolution about
11 the major axis. More specifically, every ellipse has a
12 major axis and a minor axis. When the ellipse is tenninated
13 at its minor axis the resulting half ellipse portion defines
14 an elliptical curve. The revolution of this elliptical
curve about the major axis generates a half portion of an
16 ellipsoid o~ revolution or, to describe it in another way,
17 an ellipsoid of revolution truncated in a plane formed by
18 all possible positions of the minor axis. Referring to
19 FIGURE 1, the first reflector surface 14 may be viewed as
being truncated by or terminated with the second reflector
21 surface 16. In that the second reflector surface 16 has a
22 planar configuration, the same is substantially disposed in
23 the plane formed by all possible positions of the minor
24 axis.
Referring to FIGURE 1, as with all ellipsoids of
26 revolution or portions thereof, reflector surface 14 has a
27 primary'focus 18 and a conjugate secondary focus 20.
28 Although the secondary focus 20 is not illustrated in FIGURE
29
ii7
1 1, it is clearly shown in ~IG~RE 3. The primary and secon-
2 dary foci 18 and 20 define a symmetry axis 22. The symmetry
3 a~is 22 is substantially perpendicular to the second
4 reflector surface 16 which i~3 substantially equall~ spac~d from
the two foci 18 and 20. The reflector surfaces 14 and 16
6 enclose the primary focus 18, while the secondary focus 20
7 is situated e~teriorly to the reflector chamber 12.
8 Generally, radiation emanating ~rom one focus of
g an ellipsoid of revolution is reflected so as to converge
toward the second focus. By placing the planar reflector
11 surface 16 in a plane perpendicular to the major a~is and
12 containi~ny the minor axis, the design of the reflector
13 chamber 12 retains half of an ellipsoid of revolution and
1~ discards the remaining half. By virtue of this arrangement,
the impact of the second reflector surface on the above
16 described ray paths for an ellipsoid of revolution may be
17 visualized as creating a mirror image of the first reflector
18 surface so as to create an equivalently complete ellipsoid
19 cf revolution. More specifically, a ray reflected from the :~
second reflector surface 16, proceeds within the half o, the
21 ellipsoid of revolution represented by the first reflector
22 surface as if it was proceeding within the previously
23 described discarded half of the ellipsoid of revolution.
24 Consequently, a ray convergent upon the secondary focus 20,
upon reflection from the secondary reflector surface 16, is
26 conver~3en~ upon the primary focus 18. On the other hand, a
27 ray proceeding toward a point of intersection on the pre-
28 viously descri~ed discarded half and which is not convergent
29
:
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8~7
1 upon the secondary focus 20, upon reflection from the second
2 reflector surface 16, ~roceeds to impinge upon the first
3 reflector surface at a point corresponding in position to
4 the previously described point of intersection on the
discarded half. Unless this ray passes through an opening
6 or window 24, to be described hereinafter, the xay is
7 reflected from the first reflector surface 14 so as to be
8 convergent upon the primary focus 18. The specific ray
g patterns of the preferred embodiment will be clarified
hereinafter.
11 AS depicted in FIGURE 1, the window 2~ is formed
12 in the first reflector surface 14 so ~s to provide an exit
13 for radiation. The window 24 is preferably aligned to be
14 centered on the symmetry axis 22. In the preferred embodi-
ment a confining window glass 25, preferably having a
16 spherical configuration, retains the fluid in the reflector
17 chamber 12. Depending upon the usage of the reflector ;~
1~ chamber 12 with aerosols or hydrosols, it may or may not be
19 desirable to have the window glass 25. Preferably, the
window glass 25 has an inner and outer radii thereof having
21 a center at the primary focus 18 so as to allow the
22 exiting radiation to pass orthogonally through its surfaces.
23 Referring to FIGURE 2, means for entraining the
24 particulate material through the primary focus 18 of the
first reflector surface 14 is generally represented by
~6 reference numeral 26. The entraining means 26 provides for
27 fluid t~ansport of individually isolated particulate
28 material in suspension through a measurement region 28.
29
3~27~6~
1 ~ore specifically, in the preferred embodiment entraining
2 means 26 includes an entrallce tube 30 which ideally provides
3 a stream of sequential particulate material and an outer
4 sheath tube 32 which encompasses the entrance tube 30 and
provides sheathillg fluid. Likewise, on the other end of the
6 measurement region 28, there is normally positioned an exit
7 tube 34 having an orifice for receiving the stream of par-
8 ticulate material. Laminar fluid flow is maintained through
g the measurement region 28 by the introduction of the sheath-
ing fluid, along with the creation of a differential pres-
11 surc betweell the quiescent volume and the sheathing fluid
12 and the sample cell flow. In the preferred embodiment the
13 reflector chamber 12 is filled with a particulate-free
1~ liquid medium, although a chamber using a gaseous medium
could be used with the present invention. The specific
16 construction of the entraining means 26 which provides
17 passage of the particulate material through the measurement
18 28 is of conventional design.
19 As depicted in FIGURE 2, means for irradiating the .
particulate material with preferably a high intensity light
21 beam, such as a laser excitation beam, is generally indi-
22 cated by numeral 36. Irradiating means 36 includes a beam
23- entrance orifice 38 and a beam exit orifice ~0O Exteriorly
24 positioned relative to the orifices 38 and 40 are, respec-
tively, a beam source (not shown) and a beam dump (not
26 shown) for emitting and disposing of the light beam. The
27 two orif'ices 38 and 40 are aligned with each other so as to
28 preferably, but not necessarily, allow the light beam
~9
.
1 passing therebetweell to intersect orthogonally the flow of
2 particulate material i~n the measurement region 28. As will
3 become apparent hereinafter the light beam must approxi-
4 mately intersect the flow of particulate material at the
primary focus 18 of the first reflector surface 14. It
6 should be appreciated that although laser light is used to
7 illustrate the operation of the preferred embodiments of the
8 present invention, the particulate material could be
g impinged upon by other forms of radiant energy as will
become moxe apparent hereinafter.
11 ~lthough scattered light and fluorescent light are `
12 commonly collected, it should be understood that the present
13 invention may also be used to collect other forms of radiant
14 energy from particulate material. Consequently, the term
"detectable radiation" may include any radiant energy which
16 propagates in straight lines and undergoes specular reflec-
17 tion, such as light, infrared radiation and ultraviolet
18 radiation. However, for the purposes of describing the
19 preferred embodiments, scattered light and fluorescent light
will be used as examples of detectable radiation.
21 In one type of analysis, the laser excitation beam
22 is scattered by the particles so that most of the scattered
23 light will deviate from and not be received by the beam exit
24 orifice 40. Another analysis commonly used in the industry
is to excite fluorescence as biological cells traverse the
26 laser excitation beam. Fluorescent excitation is normally
27 accomplished by staining the cells with a fluorescent dye
28 and dispersing the cells into a suspension sufficiently
29
. . .
~7~3~7
1 dflute that the cells proceed one by one throu~h the primary
2 focus 18. In either case, there is typically scattered
3 laser light and/or relatively weak fluorescent light, both
4 which hereinafter will be termed "detectable radiation".
Consequently, the interaction of the irradiating means 36
6 with the particulate material defines a source 42 of de-
7 tectable radiation at the primary focus 18. The above
8 described procedure of having a laser excitation beam
g intersect a sample stream of particulate material, possibly
stained, at one of the foci of the ellipsoid is a well known
11 procedure in the art.
12 Referring to FIGURE 1, in operation the radiation
13 collector apparatus 10 irradiates the particulate material
14 stream to produce detectable radiation which emanates out-
ward from the primary focus 18. The detectable radiation
16 either proceeds directly through the window 24 as illu-
17 strated by ray Rl or is reflected one or more times off of
18 the first reflector surfacè 14 and/or the second reflector
19 surface 16 as illustrated by rays R2 and R3. As to the
reflected detecta~le radiation, the number of reflections of
21 a given ray will depend on which of the two reflector
22 surfaces 14 or 16 the ray initially impinges upon after
23 emanating from the primary focus 18, the position of the
24 initial intersection of the given ray with the reflector
surfaces 14 or 16~ and the solid angle subtended by the
26 window 24 relative to the primary focus 18.
27 Except for an insigniEicant amount of radiation to
28 be discussed hereinafter, all rays exit directly or after an
29
....
~Z~B167
1 even number of reflections from the window 24 in such a
2 direction that they seem to ernanate from the primary focus
3 18. In the preferred embodiment of FIGURE 1 the solid
4 angles subtended by the second reflector surface 16 and the
window 24 at the primary focus 18 are ideally but not
6 necessarily equal. As illustrated by ray R2, almost all of
7 the detectable radiation initially im~inging upon the second
8 reflector surface 16 after emanating from the primary focus
9 18 is reflected four times in the following sequence:
reflected off the second reflector surface 16 once, then
11 reflected off the first reflector surface 14 twice on
12 opposed portions thereof, and finally reflected off the
13 second reflector surface 16 for a second time to pass
14 through primary focus 18 and exit through the window 24. As
illustrated by ray R3, any ray which initially impinges upon
16 the first reflector surface 14 is subsequently reflected off .
17 of the second reflector surface 16 so as to pass through the
18 primary focus 18 and exit through the window 24. In sum- :
19 mary, with the above described equal solid angles, rays
initially impinging upon the first reflector surface 14 exit
21 through the window 24 after two reflections and rays ini- :
22 tially impinging upon the second reflector surface 16 are
23 reflected four times before exiting through the window 24 in
24 an organized manner. This organi~ed radiation permits the
use o' techniques commonly used with convergent, divergent
26 or collimated radiation, such as filtering out stray radi-
27 ation with a pinhole, or the concentration of radiation in a
28 collimated beam for more efficient use of the same by
29
-17
1 detector means. As previously referred to as an e~ception,
2 there is an insignificant amount of reflected detectable
3 radiation which impinges near the center of the second
4 reflector surface 16 after emanating from the primary focus
18 which is reflected only once so as to bounce back to and
6 exit out of the window 24 without further reflection and
7 without proceeding through the primary focus 18.
8 ~t should be noted that in the preferred embodi-
g ment the window 24 subtending a solid angle equal to that of
the second reflector surface 16 is merely a matter of design
11 preference. There are certain design preferences which may
12 suggest a larger or smaller window 24. For instance, if the
13 window 24 is dimensioned to have a solid angle smaller than
14 the solid angle of the second reflector surface 16, then
some of the detectable radiation impinging initially on the
16 first reflector surface 14 will be reflected more than twice
17 while some of the detectable radiation impinging initially
18 upon the second reflector surface 16 will be reflected more
19 than four times. As illustrative of some factors to be
considered, the disadvantage of more reflections, and
21 therefore decrease in radiation intensity, must be weighed
22 against the advantages of having a smaller collection angle
23 for a lens 44 and a smaller center cone of disorganized
24 radiation. Generally, too small of a window 24 would be
undesirable due to the number of reflections. On the other
26 hand, too large of a window is undesirable even though there
27 are less~ reflections due to the radiation having to be
28 collected over too wide of an angle relative to the primary
29
~7~3~7
1 focus 18. Lenses with f-numbers below approximately 0.7 are
2 not easily available commercially. Consequently, the design
3 considerations of loss of radiation intensity by reflection,
4 the angle of collection of detectable radiation passing
through the window 24 which desireably determines the
6 eccentricity of the ellipsoid for a maximum of four re-
7 flections and other similar factors all dictate the size of
8 the window 24, such sizing being considered to be merely a
g matter of design performance. Accordingly, variations in
the si2e of the window 24 are considered to be within the
11 scope of this invention.
12 In the practical application of the radiation
13 collector apparatus 10, the foci 18 and 20 are actually
14 focal zones and not theoretical points. In the preferred
embodiments the intersection of the particulate material,
16 which may be the width of several particles, with the laser
17 beam may create a "sensing zone" of radiating radiation at
18 the primary ocus 18 having a volume of up to 10,000 cubic
19 microns in the preferred embodiment. ~ore specifically, the
finite dimensions and somewhat diffused (Gaussian) distri-
21 bution of radiation, convolved with the path of the parti-
22 culate suspension, gives rise to this "sensing zone". This
23 zone at the primary focus 18 is centered around a mathe-
24 matical, infinitesimally small focal point and i5 repre-
sented in the drawings as a single point. As is well known .
26 in the art, a zone centered at the first focal point of the
27 ellipso~d creates a corresponding zone of radiation centered
28 at the second focal point of the ellipsoid~ Although
29
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7~3~7
1 identified as a geome-trical point for the purposes of
2 illustration in the drawinys, the term "focus" refers to a
3 focal zone generally centered about an infinitisimally small
4 focal point.
A distortion to the configuration of the first
6 reflector surface 14 can be introduced and compensated for
7 by correspondingly modifying the second reflector surface 16
8 with the use of numerical techniques to provide the same
g results of returning the reflected detectable radiation to
the primary focus 18. Consequently, with the introduction
11 of such distortions, both the first reflector surface 14 and
12 the second reflector surface 16 would deviate from a precise
13 ellipsoidal conic section configuration and planar confi-
14 guration, respectively, but in combination would accomplish
the same result. ~lso, the introduction of a relatively
16 small distortion to the second reflector surface 16 produces
17 a lar~er zone for the reflected detectable radiation at the
18 primary focus 18. Such a largex zone is not particularly
19 desirable, but in certain applications is tolerable. It
should be understood that such mere changes in configuration
21 as described in this paragraph are considered to be within
22 the scope of this invention, and for this reason the claims
23 of this application use the term "substantially" when
24 referring to the configuration of the reflector surfaces 14
~5 and 16.
26 ~ Detector means 4~ (partially shown) is ordinarily
27 positioned exterior to the reflector chamber 12 along the
28 symmetxy axis 22 for the conversion of detectable signals to
29
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78~7
1 electrical signals so as to provide subsequent data acquisi-
2 tion. The specific co~nstruction of the detector means with
3 its associated optics for the preferred embodi~ents may be
4 of many conventional desisns well known to those s~illed in
the art. The detector means ~5receives the detecta~le radi-
6 ation and converts the detectable radiation into electrical `
7 signals to be used in a conventional pulse height analyzer
8 or similar well known data acquisition device. For the
g preferred embodiments in which the detectable radiation
comprises light the typical detector means would normally
11 comprise a well known photosensitive detector, preferably in
12 the form of photomultiplier tubes, vacuum photodiodes or
13 solid state photodiodes and the like. ~ormally, although
14 not necessarily, the detector means would include the
collimating lens ~4 for providing normal light to the
16 photosensitive surfaces of the photosensitive detector as
17 shown in ~IGURE 1. The more orthogonally that the organized
18 beam arrives at the photosensitive surface of the photo-
19 sensitive detector, the more efficiently the photosensitive
detector will operate. In addition, an optional light color
21 filter 46 may be included to separate fluorescent and
22 scattered light which also operates more efficiently with
23 normal light. In summary the collection of almost all of
24 the detectable radiation into an organized diverging beam
proceeding from the primary focus 18 allows for the more
26 efficient use of optional light color filters, such as the
27 filter 46, and the photosensitive detector. ~dditionally,
28 this organized light also allows for the use of other
29
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. . , ~',,:
.. . .. ..
~7~
1 optical techniques available for collimated~ divergent, and
2 convergent light, such as the incorporation of a pinhole
3 aperture for filtering out stray light.
4 The present invention is useful if the detectable
radiation comes from a source which is so small that it has
6 negligible self-shadowing effects as the light passes
7 through the primary focus 18 after the second or fourth (or
8 other multiples of 2) re1ection. It should be noted that
9 with the analysis of particulate material, the particles
normally are sufficiently small so ~hat blockage of
11 radiation passing through the primary focus 18 is
12 relatively insignificant as in U.S. Patent 3,989,381.
13 With reference to FIGURE 3, an optional
14 variation of the present invention is to make the second
lS reflector surface 16 a dichroic reflector 48 ideally
16 comprising a mirror coated with a well known dichroic
17 coating. This dichroic coating defines an inwardly facing
18 dichroic surface 50, preferably on the front surface of
19 the mirror which passes through only certain wavelengths
of radiation. Ideally, for some applications in
21 particle analysis, dichroic reflector 48 reflects
22 incident fluorescent light rays, such as R4, and
23 passes through incident scattered laser light rays, such
24 as R5 and R6. However, the selection of those
wavelengths to be passed through and those to be
26 reflected are matters of design preference which will be
27 dictated by the particular application for which the present
29
-22 -
~: ,
7~
1 inverltion is used. In the preferred embodiment of this
2 variation, such an arrangement wouid permit most of the
3 scattered laser light to converge toward the secondary focus
4 20. In that the scattered light forms an organi~ed beam,
various optical techniques which are usable with organized
6 light may be optionally included. For instance, a wall 52
7 with a pinhole 54 may be optionally provided for filtering
8 out stray light. In addition, a second collimating lens 56
g may be included to provide normal light for a second detec-
tor means (not shown). Consequently, the scattered light
11 and the fluorescent light are collected at opposed ends of
12 the reflector chamber 12. By virtue of this design, various
13 analyses commonly conducted in the industry which require `~
1~ the separation light of different wavelengths may be con-
ducted. Although laser light and fluorescent light are the
16 two types of light separated in the preferred use of the
17 present invention, it should be understood that any two
18 types of radiation capable of being separated by a dichroic
19 coating are within the scope of this invention.
As shown in FIGVRE 4, an alternative embodiment of
21 the radiation collector 10 of the present invention is
22 provided with a window 58 formed in the second reflector
23 surface 16 so as to provide an exit for the detectable
24 radiation. The window 58 is aligned in intersecting rela-
tionship ~ith the symmetry a~is 22, and in the preferred
26 embodiment is centered thereon. In the preferred embodiment
27 a confininy window glass 60, preferably having a spherical
28 configuration, retains the fluid in the reflector
29
-23-
.
'7~
1 chamber 12. Depending upon the usage of the reflector
2 chamber 12 with hydrosols or aerosols, it may or may not he
3 desirable to have the window glass 60. Preferably, the
4 window glass 60 has an inner and outer radii thereof having
a center at the secondary focus 20 so as to allow most of
6 the exiting radiation to pass orthogonally.through its
7 surfaces, minimizing intensity losses and refractive bending.
8 Referring to FIGURE 4, in operation the radiation
g collector apparatus 10 provides for the detectable radiation
to exit through the window 58 either directly as illustrated
11 by ray ~7 or after being reflected one or more times off of
12 the second reflector surface 16 and/or the first reflector
13 surface 1~ as illustrated by rays R8, R9 and R10. As to the
14 reflected dete~table radiation, the number of reflections of
a given ray will depend upon which of the two reflector
16 surfaces 14 or 16 the ray initially impinges upon after
17 emanating from the primary focus 18, the position of the
18 initial intersection of the given ray with the reflector
19 surface 14 or 16, and the solid angle subtended by the
window 58 relative to the primary focus 18.
21 with reference to FIGURE 4, except for a small
22 amount of radiation to be discussed hereinafter, all rays
23 exit after an odd number of reflections from the window
24 58 and in such a direction that they converge on the
secondary focus 20. The small amount of radiation pre-
26 viously referred to exits from the window 58 after emanating
27 from the primary focus 18 without reflection. This
28 ~ .
29
-24-
~7~6~
1 small amount of detectable radiation comprises a cone
2 centered on the symmetry a~is 22 which forms a solid angle
3 at the prlmary focus 18 that is dependent upon the size of
4 the window 58. As illustrated by ray R8, a portion of -the
de.ectable radiation which ini,ially impinges upon the first
6 reflector surface 14 passes through the wlndow 58 after one
7 reflection. As illustrated by ray R9, the remaining portion
8 of the detectable radiation which emanates from the primary
g focus 18 and impinges upon the first reflector surface 14
passes through the window 58 after three reflections. As
11 illustrated by ray R10, the detectable radiation which
12 emana~es from the primary focus 18 and impinges upon the
13 second reflector surface 16 is reflected three times prior
14 to passing through the window e~it 58. The amount of
detec~able radiation which is reflected one time versus
16 the amount that is reflected three times is dependent
17 UpOII the size of the window 58. Moreover, if the window
18 is made sufficiently smaller than that illustrated in
19 FIG~RE 9, then some of the detectable radiation is reflected
at least five times. Consequently the size of the window 58
21 as illustrated in FIG~RE 4 is merely a matter of design
22 preference. For instance, a smaller window 58 provides
23 for a narrower beam exiting from the same, but on the other
24 hand, results in portions of the detectable radiation
being reflected more times with its associated decrease
26 in radiation intensity. This embodiment is particularly
- 27 advantagèous in that the window 58 can be dimensioned
28 and configured such that a relatively narrow beam of
29
~ -25-
~786 '~
1 radiation exits ~rom the same. As previously described with
2 the embodiment illustrated in FIGURE 1, the organized
3 radiation which converges on the secondary focus 20 permits
4 the use of techniques commonly used with organized radia-
5 tion.
6 As illustrated in FIGURE 4, a lens arrangement
7 62 is optionally provided for the organization of substan-
S tially all of the detectable radiation exiting through the
g window 5~. As previously described, there is a cone of
detectable radiation which emanates directly through the
11 window 58 which is not convergent upon the secondary focus
12 20, as illustrated by ray R7. The remainder of the detect-
13 able radiation converges on the secondary focus 20. The
14 lens arrangement 62 comprises a pair of coaxial lenses,
center lens 64 and peripheral lens 66 having a center aper-
16 ture 68. In the preferred embodiment illustrated in FIGURE
17 q, these two lenses 6q and 66 are offset relative to each
18 other along the symmetry axis 22 while maintaining a coaxial
19 relationship. However, the two lenses could have concentric
centers with both lenses being located downstream relative
21 to the secondary focus 20. Additionally, the lenses 62 and
22 64 which are incorporated in the present invention are
23 ideally utilized to organize the radiation into a collimated
24 beam. However, for some applications, it might be de-
sira~le to use such lenses so as to create a convergent
2~ or divergent beam on a common focus. But for the purpose of
27 collecting light with photosensitive surfaces, orthogonal
28 radiation is desirable. In the preferred embodiment of
29 FIGURE q, to create the collimated beam, the peripheral
-26-
3~27~3~i7
1 lens 66 would have a focus at the primary focus 18, while
2 the cente~ lens 64 would have a focus at the secondary
3 focus 20. However, it should be understood that any pair
4 of coaxial lenses having foci, either actual or ~irtual,
which results in the production of an organized beam of
6 radiation from the radiation emanating from the primary
7 focus 18 and also from radiation converging toward the
8 secondary focus 20 is within the scope of the present
9 invention. It should also be appreciated that in ~his
embodiment, the detectable radiation enters the lenses 64
11 and 66 or any other lens substituted therefor at an angle
12 not far from`the normal.
13 Referring to FIGURE 5, there is shown yet
14 another embodiment of the radiation collector apparatus 10
for collecting detectable radiat:ion produced by irradia~ing
16 individually isolated particulat:e material. The radiation
17 collector apparatus 10 comprises the reflector chamber 12
18 having an internal ellipsoidal reflector surface 70 defined
19 by a housing 72. The ellipsoidal reflector surface 70 has
the configuration of an ellipsoid of revolution about the
21 major axis, or, to describe the configuration in another
22 way, a spheroid. More specifically, e~ery ellipse has a
23 major axis and a minor axis. The revolution of this ellipse
24 about the major axis generates an ellipsoid of revolution.
As with all ellipsoids of revolution, the ellipsoidal
26 reflector surface 70 has the primary focus 18 and the
27 conjugate secondary focus 20. The primary and secondary
28 foci 18 and 20 define a symmetry axis 22. The reflector
29
67
1 chamber 12 can also be viewed as being formed by two half
2 ellipsoids of revolution 74 and 76.
3 As depicted in FIGURE 5, the opening or window
4 24 is formed in the ellipsoidal reflector surface 70 so as
to provide an exit for radiation. The window 24 is
6 aligned to be preferably centered on symmetry axis 22. In
7 this embodiment, the confining window glass 25 retains the
8 fluid in the reflector chamber 12.
9 Referring to FIGURE S, in operation the
radiation collector apparatus 10 illuminates the
11 particulate material stream to produce de~ectable
12 radiation which emanates outward from the primary focus 18.
13 In this embodiment of the present invention illustrated in
14 FIGURE 5, the window 24 is posit:ioned adjacent the source
of detectable radiation 42. In the embodiment of FIGU~E 5,
16 the detectable radiation either proceeds directly through
17 the window 24 as illustrated by ray Rl or is reflected two
18 or more times off of the ellipsoidal reflector surface 70
l9 before exiting through window 24 as illustrated by rays R2
and ~3. As to the reflected dctectable radiation, the
21 number of reflections of a given ray will depend on the
22 position of the initial intersection of the ray with the
23 ellipsoidal reflector surface 70 after emanating from the
24 primary focus 18 and the solid angle subtended by the
window 24 relative to the primary focus 18. With an
26 exception of an insignificant amount of detectable
27 radiation all reflected ra,vs exit after two or more
28 reflections from the window 24 regardless of the size of
29 window 24,
-28-
~ ~7~6~
1 As illustrated in FIGURE 5, a plane perpendicular
2 to the symmetry axis 22 containing all possible orientations
3 of the minor axis of the ellipsoidal reflector surface 70
4 will hereinafter be ter~ed "bisecting plane 78". In the
embodiment of FIGURE 5, the intersection of the bisecting
6 plane 78 with the ellipsoidal reflector surface 70 subtends
7 a solid angle at the primary focus 18 which is equal to the
8 solid angle subtended by the window 24 at the primary focus
9 18. The bisecting plane 78 may be ~iewed as dividing the
ellipsoidal reflector surface 70 into two e~ual halves.
11 With this solid angle of the window 24, almost all of the
12 re~lected detectable radiation is reflected either two or
13 four times. More specifically, the vastly greater amount
14 of reflected detectable radiation is reflected twice prior
to passing through the primary i--ocus 18 and subsequently
16 exiting through the window 2~, as illustrated by ray R3.
17 Additionally, a small amount of the reflected detectable
18 radiation which e~anates in a cone centered on the symmetry
19 axis 22 is reflected four times prior to passing through
the primary focus 18 and subsequently exiting through window
21 24, as illustrated by ray R2. This cone intersects the :
22 ellipsoidal reflector surface 70 in an area having a solid
23 an~le, with respect to the secondary focus 20, equal to the
24 solid angle formed by the bisecting plane 78 with respect to
the secondary focus 20. Only for the purposes of a complete
26 explanation, it should be noted that a miniscule amount of
27 detectable radiation centered about the symmetry axis 22 is
28 reflected only once before exiting ~rom the window 24. With
29 the exception of the abo~e described miniscule amount, the
.. .. .. . . . . . . . . . . _ . . . _ . .. . .. . .. .
. . . .
. . . . . . .. . . . . _ . _ _ _ . _ ... . . _ . .. .
. 29
.. .. . . . . . ... .
1 detectable radiation exiting from the window 24 is
2 organized in that such radiation passes through and
3 proceeds from the primary focus 18. This permits the use
4 of techniques commonly used with convergent, divergent or
collimated radiation, such as filtering oUL stray
6 radiation with a pinhole, or the concentration of
7 radiation in a narrow beam for more efficient use of the
8 same by detector means 45.
9 An alternative embodiment of ~he present
invention is illustrated in FIGURE 6. As previously
11 described, the embodiment of FIGURE 5 has the source 42
12 of detectable radiation positioned at the primary focus 18
13 so that the source 42 is adjacent the window 24. In the
14 alternative embodiment of FIGURE 6, the source 42 of
detectable radiation, and therefore the entraining means 26
16 and irradiating means 36, are positioned at the secondary
17 ~ocus 20. The signi.~icance of t:his embodiment is that the
18 source 42 is now positioned at t:he most remote focus
19 relative to the window 24. With reference to the drawings,
the embodiment of FIGURE 6 could have been shown just as
21 well by leaving the source 42 at the primary focus 1~ and
22 moving the window 24 to the other end of the reflector
23 chamber 12. In summary, the embodiment of FIGURE 6 has the
24 source 42 positioned at the most remote focus relative to
the window 24, while the embodiment o~ FIGURE 5 has the
26 source 42 positioned at the ~ocus adjacently disposed
27 relative to the window 24. Consequently, identical elements
28 which have merely been transferred from one ~ocus to the
29 other focus, such as irradiating means 36 and entraining
------ - .
-30-
i 127B~7
1 means 26, retain the same reference numerals in the drawings
2 for all ~mbodiments.
3 In the embodiment of FIGURE 6, most of the
4 detectable radiation is reflected one or more times off of
the ellipsoidal reflector surface 70 before exiting through
6 window 24 as illustrated by rays R4 and R5. As to the
7 reflected detectable radiation, the number of reflections
8 of a given ray w:ill depend on the position of the initial
9 intersection of the ray with the ellipsoidal reflector
surface 14 after emanating from the secondary focus 20 and
11 the solid angle subtended by the window 24 relative to the
12 primary focus 18, Generally, all reflected rays exit after
13 one or more reflections through the window 24 regardless of
14 the size of window 24.
As with the embodiment of FIGURE 5, in the
16 embodiment of FIGURE 6 the inter'section of the bisecting
17 plane 78 with the ellipsoidal re.flector surface 70 subtends
18 a solid an~le at t~e primary focus 18 which is equal to the
lg solid angle subtended by the window 24 at the primary focus
18. With this solid angle of the window 24 almost all o~
21 the re1ected detectable radiation is reflected either once
22 or three times. More specifically~ the detectable radia~ion
23 emanating from the secondary focus 20 which initially
24 impinges upon the near half portion of the ellipsoidal
reflector surface 70 defined by the bisecting plane 78 is
26 reflected once before exiting through the window 24 as
27 illustrated by ray R4. This constitutes the vast majority
28 of the detectable radiation. The detectable radiation
29
~L~2~7~
1 emanating rom the secondary focus 20 which initially
2 impinges upon the remote half portion of the ellipsoid
3 reflector surface 70 defined by the bisecting plane 78 is
4 reflected three times before exiting through the window 24
as illustrated by ray R5. Only for the purposes of a
6 complete explanation it should be noted that a miniscule
7 amount of the detectable radiation passes through the
8 window 24 without reflection and without passing through
9 the primary focus 18. With the exception of the above
described miniscule amount, the detectable radiation
11 exiting from the window 24 is organized in that such
12 radiation passes throu~h and proceeds from the primary
13 focus 18. This permits the use o~ techniques
14 commonly used with convergent, divergent or collimated
radiation, such as filtering oul: stray radiation with a
16 pinhole, or the concentration of radiation in a narrow beam
17 for more efficient use of the same by the detector means 45.
18 It should be noted that in the embodiments of
19 FIGURES 5 and 6, the window 24 subtending a solid angle
equal to that of the bisecting plane 78 is merely a matter
21 of design preference. There are certain design preferences
22 which may suggest a larger or smaller window 24. For
23 instance, if the window 24 is dimensioned to have a smaller
24 solid angle than previously described, then portions of the
detectable radiation will be reflected more than the number
26 of times previously described. More specifically, in the
27 embodiment of FIGU~E 5, if the previously described solid
28 angle of the window varies from that shown in the drawings,
29 the previously described areas of four reflections and two
. :
-32-
~27~67
1 reflections will no longer be valid. Likewise, in the
2 embodiment of FIGURE 6 the areas of one reflection and
3 three reflections would no longer be valid.
4 A distortion to the configuration of the first
half of the ellipsoidal reflector surface 70 relative to the
6 bisecting plane 78 may be introduced and compensated for by
7 correspcndingly modifying the second half of the ellipsoidal
8 reflector surface 70 by the use of numerical techniques to
9 provide the same results of returning the reflected
detectable radiation to the primary focus 18. Consequently,
ll with the introduction of such distortions, the ellipsoidal
12 reflector surface 70 would deviate from a precise
13 ellipsoidal conic section configuration but the two
14 described halves 74 and 76 in combination would accomplish
the same result. Also, the introduction of a relatively
16 small distortion to one of the halves produces larger zones
17 for the reflected detectable racliation at the foci 18 and
18 20. Such ~arger ~ones are not particularly desirable, but
l9 in certain applications are ~olerable. It should be
understood that such mere changes in configuration as
~l described in this paragraph are considered to be within the
22 scope of this invention, and for this reason the claims of
23 this application use the term "substantially" when referring
24 to the configuration of the ellipsoidal reflector surface
70.
26 As pre~iously described, in par~icle analysis
27 detectable radiation, commonly either scattered light or
28 fluorescent light, emanates outward from the primary focus
29 18 or the secondary focus 20, depending upon the embodiment;
-33-
\
~7~7
1 in distribution patterns known to those skilled in the art.
2 Using the first embodiment of FIGURE 1 as an example, the
3 radiation which emanates outward from the primary focus 18
4 may take any radial direction in an imaginary sphere
centered about the primary focus 18. The solid angle
6 subtended will be utilized in this application to relate to
7 the reflector surface area which is lost for reflection of
8 radiation which emanates from the primary focus 18. The
9 collection angle therefore is the total possible angle of
radiation 4~ steradians, minus the solid angles of lost
11 radiation collection. As examples o~ items that result in
12 loss o~ collection angle, the following items are exemplary,
13 but not exclusive. First, the outer sheath tube and e~it
14 tube 32 and 34 respectively, along with beam entrance and
exit orifices 38 and 40 respectively, create four
16 relatively small solid angles oi. loss. In the prior art
17 devices, the largest solid angle of lost radiation created
18 is with the conical light collector or its equivalent.
19 However, there is no signifi~ant solid angle of lost
radiation collection formed with any substantial portion of
21 the ellipsoidal reflector surface 14 o~ the present
22 invention. In the present invention the formation of a
23 larger collection solid angle relative to those existing in
24 the prior art ellipsoidal chambers, creates a greater
radiation collection efficiency and insensiti~ity to
particle orientation.
27 The design of th~ radiation apparatus 10 provides
28 for greater collection efficiency for detectable radiation
29 than the prior ar~ collectors. This improved e~ficiency is
primarily due to a substantially 4~ steradian collection
-34-
~27~67
l angle combined with the efficient usage of the radiation
2 collected. Part of this efficient usage of the radlation
3 collected lies in collecting radiation ~ith the previously
4 described wide angle relationship with a minimum of
reflections and therefore lessening intensity losses. Yet
6 another part of this efficient usage of the radiation
7 collected includes maintaining an organized beam of collected
8 radiation during the collection process so as to permit the
9 utilization of conventional techniques co~monly used with
organized radiation. Examples of such techniques include
11 providing a relatively orthogonal approach for the rays to
12 the detector means 45 and its associated light color filter
13 46 for more efficient operation of the same. Additionally,
14 organized radiation allows for the incorporation of a pinhole
aperture for filtering out stray radiation. ~oreover, it
16 should be appreciated that light has a very broad spectrum;
17 hence, reflectors are better than lenses which act as
18 refractors of the collected light and therefore cause
19 chromatic abberation. Also, the design of the present
invention permits re~atively small eccentricities so that the
21 magnification from the primary focus 18 to the secondary
22 focus 20, or vice versa, is not excessive.
23 The present invention is useful i~ the detectable
24 radiation comes from a source which is so small that it has
negli~ible self-shadowing effects as the light passes through
26 the focus containing the source after one or multiple
27 reflections. It should be noted that wi~h the analysis of
28 particulate material, the particles normally are sufficiently
29 small so that blockage of radiation passing through the
focus containing the particles is relatively insignificant.
-35-
