CA1127867A

CA1127867A - Ellipsoid radiation collector and method

Info

Publication number: CA1127867A
Application number: CA323,101A
Authority: CA
Inventors: Albert Brunsting; Walter R. Hogg
Original assignee: Coulter Electronics Inc
Current assignee: Coulter Electronics Inc
Priority date: 1978-03-20
Filing date: 1979-03-09
Publication date: 1982-07-20
Also published as: AU4524979A; FR2420751B3; DE2910031A1; JPS54130187A; FR2420751A1; SE7902427L; GB2016735A; ES478807A1; CH629592A5

Abstract

ABSTRACT OF THE DISCLOSURE

Disclosed is a radiation collector apparatus for analyzing particles by irradiating the particles to produce a source of detectable radiation, wherein the radiation collector apparatus comprises a reflector chamber having a half ellipsoidal first reflector surfaces and a second reflector surface in the form of a planar reflector surface or a half ellipsoidal surface. Detectable radiation emanating from a primary focus of the first reflector surface either directly or after one or more reflections proceeds through a window formed in one of the reflector surfaces for subsequent processing. In another embodiment a dichroic second reflector surface is provided.

Description

.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 ~ , 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 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 ~`~

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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 ~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 , 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.

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 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:

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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.

-10- , .

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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

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 :

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.

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 . . .

~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 ....

~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 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 ~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 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 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 -21=

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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 ~: , 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 .

'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 ~ .

~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 ~ -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 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 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, ~ ~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 ------ - .

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 ~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 . :

~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;

\
~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 ~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.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A radiation collector apparatus for analyzing particulate material wherein irradiation of the particulate material produces a source of detectable radiation, said apparatus comprising: a reflector chamber having a first reflector surface and a second reflector surface, said first reflector surface substantially having a configuration of a half portion of an ellipsoid of revolution, said first reflector surface having a primary focus and a secondary focus with one of said foci being positioned within said reflector chamber at the source of detect-able radiation, and a window being formed in one of said reflector surfaces and aligned in intersecting relationship with a symmetry axis defined by said primary focus and said secondary focus, said window being dimensioned and configured to provide for a portion of the detectable radiation to reflect within said reflector chamber more than once, whereby the detectable radiation emanating from the primary focus proceeds either directly or after one or more reflections through said window.

2. The radiation collector apparatus according to claim 1, said second reflector surface having a substantially planar configuration, said second reflector surface being positioned so that any position thereon is substantially disposed in equally spaced relationship to said primary focus and said secondary focus, and said primary focus being interiorly disposed with respect to said first reflector surface and said second reflector surface and having the source of detectable radiation.

3. The radiation collector apparatus according to Claim 2, said window being formed in said first reflector surface.

4. The radiation collector apparatus according to Claim 3, said second reflector surface comprising a dichroic reflector.

5. The radiation collector apparatus according to Claim 4, said dichroic reflector including a dichroic material capable of reflecting fluorescent light, while allowing scattered light to pass therethrough.

6, The radiation collector apparatus according to Claim 2, said window being formed in said second reflector surface.

7, The radiation collector apparatus according to Claim 4, further including a peripheral lens having a center aperture centered on said symmetry axis, and a center lens centered on said symmetry axis.

8. The radiation collector apparatus according to Claim 7, said peripheral lens and said center lens being disposed in coaxial relationship relative to each other adjacent said secondary focus.

9. The radiation collector apparatus according to Claim 7 or 8, said peripheral lens comprising a collimating lens having a focus at said primary focus, and said center lens comprising a collimating lens having a focus at said secondary focus.

10. The radiation collector apparatus according to Claim 1, said second reflector surface having a configuration of a substantially half ellipsoid of revolution, and said first reflector surface and said second reflector surface being confocal with the same eccentricity to define a single ellipsoidal reflector surface.

11. The radiation collector apparatus according to Claim 10, said window being formed in said first reflector surface.

12. The radiation collector apparatus according to Claim 10, said window being formed in said second reflector surface.

13. The radiation collector apparatus according to any one of Claims 10, 11, or 12, the source of detectable radiation being positioned at the more remotely disposed focus of said pair of foci relative to said window.

14. The radiation collector apparatus according to any one of Claims 10, 11, or 12, the source of detectable radiation being positioned at the more adjacently disposed focus of said pair of foci relative to said window.

15. The radiation collector apparatus according to any one of Claims l, 2, or 10, further comprising means for passing the particulate material through said primary focus.

16. The radiation collector apparatus according to any one of Claims l, 2, or 10, further comprising means for irradiating the particulate material with light at said primary focus to produce detectable radiation deviating from the path of the irradiating light, said detectable radiation deviating from the path of the irradiating light defining the source of detectable radiation.

17. The radiation collector apparatus according to any one of Claims 1, 2 or 10, further comprising detector means cooperatively positioned on the symmetry axis for receiving the detectable radiation.

18. A method of collecting detectable radiation produced by the presence of particulate material, comprising the steps of: dividing the detectable radiation emanating from a primary focus of a first reflector surface, having a half portion of an ellipsoid configuration, into at least a first portion of detectable radiation directed toward the first reflector surface and a second portion of detectable radiation directed toward a second reflector surface in a solid angle subtended by the junction of the first reflector surface and the second reflector surface in a plane of all possible positions of a minor axis of the first reflector surface, reflecting from the first reflector surface the first portion of detectable radiation emanating from the primary focus so that the detectable radiation is convergent on a secondary focus of the first reflector surface, reflecting from the second reflector surface the second portion of detectable radiation emanating from the primary focus so that the detectable radiation is convergent on the primary focus of the first reflector surface after two reflections, and passing the reflected detectable radiation which has reflected at least once off of at least one of the reflector surfaces through a window formed in one of the reflector surfaces.

19. The method of Claim 18, further comprising:
directing the second portion of detectable radiation emanating from the primary focus toward a planar configuration of a second reflector surface, reflecting that part of the first portion of the detectable radiation proceeding from the first reflector surface after one reflection and which impinges upon the second reflector surface off of the second reflector surface so that the same is convergent upon the primary focus, and reflecting the second portion of the detectable radiation emanating from the primary focus off of the second reflector surface so that the detectable radiation subsequently reflects from the first reflector surface twice, so as to be convergent upon the secondary focus.

20. The method of Claim 19, further comprising positioning the window so as to be formed in the first reflector surface, passing through the second reflector surface radiation having a predetermined wavelength range, and reflecting radiation of all other wavelengths from the second reflector surface.

21. The method of Claim 19, further comprising positioning the window so as to be formed in the second reflector surface, collimating radiation proceeding through the window from the primary focus, and collimating radiation proceeding through the window toward the secondary focus.

22. The method of Claim 18, further comprising:
dividing the detectable radiation into three portions, reflecting from the first reflector surface the first portion of the detectable radiation emanating from a primary focus of the first reflector surface so that the detectable radiation proceeds toward the second reflector surface having a planar configuration, thereafter reflecting the first portion of the detectable radiation proceeding from the first reflector surface off of the second reflector surface so that the detectable radiation having been twice reflected proceeds toward and passes through the primary focus, reflecting from the second reflector surface detectable radiation comprising the second portion of the detectable radiation emanating from the primary focus so that a substantial part of this detectable radiation subsequently reflects off of the first reflector surface twice, thereafter reflecting the second portion of the detectable radiation which previously was reflected from the first reflector surface twice off of the second reflector surface for a second time so that the detectable radiation having been reflected four times proceeds toward and passes through the primary focus, and passing a third portion of the detectable radiation emanating from the primary focus through the window formed in the first reflector surface without reflection.

23. The method of Claim 22, further comprising, passing through the second reflector surface radiation having a predetermined wavelength range and reflecting radiation of all other wavelengths from the second reflector surface.

24. The method of Claim 18, further comprising:
reflecting from the first reflector surface the first portion of detectable radiation emanating from the primary focus so that the detectable radiation proceeds toward the second reflector surface having a planar configuration, thereafter reflecting that part of the first portion of the detectable radiation proceeding from the first reflector surface after one reflection and impinging upon the second reflector surface off of the second reflector surface so that the detectable radiation having been twice reflected proceeds toward and passes through the primary focus so as to be reflected for a third time off of the first reflector surface, passing the remaining part of the first portion of detectable radiation proceeding from the first reflector surface after one reflection directly through the window formed in the second reflector surface without further reflection, reflecting from the second reflector surface the second portion of detectable radiation emanating from the primary focus so that a substantial part of the second portion of the detectable radiation subsequently reflects of of the first reflector surface twice, and passing the remaining part of the second portion of detectable radiation emanating from the primary focus through the window in the second reflector surface without reflection.

25, The method of Claim 18, further comprising:
directing the second portion of detectable radiation toward the second reflector surface having a half of an ellipsoid of revolution configuration, thereby defining an ellipsoidal reflector surface, reflecting a first part of the detectable radiation comprising most of the detectable radiation emanating from the focus off of the ellipsoidal reflector surface at least once, reflecting a second part of the detectable radiation comprising a part of the remaining detectable radiation emanating from the focus at least three times> and thereafter passing the reflected detectable radiation through the window formed in the ellipsoidal reflector surface in an organized beam.

26. The method of Claim 25, further comprising, passing a third part of the remaining detectable radiation emanating from the focus directly through the window without reflection in an organized beam.

27, The method of Claim 18, further comprising:
directing the second portion of detectable radiation toward the second reflector surface having a half of an ellipsoid of revolution configuration, thereby defining an ellipsoidal reflector surface, reflecting off of the ellipsoidal reflector surface a first part of the detectable radiation emanating from the focus at least once but not more than twice, reflecting off of the ellipsoidal reflector surface a second part of the detectable radiation emanating from the focus by at least one pair of reflections more than the number of reflections of the first part, and passing the first part and second part of the detectable radiation through a window formed in the ellipsoidal reflector surface in an organized beam.

28. The method according to any one of Claims 18, 19, or 22, further comprising, providing a window dimensioned and configured so that no further reflections are required before the detectable radiation exits from the window.

29. The method according to any one of Claims 24, 25, or 27, further comprising, providing a window dimensioned and configured so that no further reflections are required before the detectable radiation exits from the window.

30. The method according to any one of Claims 18, 19, or 22, further comprising, providing a window so that further reflections are required before the detectable radiation exits from the window.

31. The method according to any one of Claims 24, 25, or 27, further comprising, providing a window so that further reflections are required before the detectable radiation exits from the window.

32. The method according to any one of Claims 18, 19, or 22, further comprising, providing a window so that fewer reflections are required before the detectable radiation exits from the window.

33. The method according to any one of Claims 24, 25, or 27, further comprising providing a window so that fewer reflections are required before the detectable radiation exits from the window.