WO1994005984A1

WO1994005984A1 - Method and apparatus for use of polarized light vectors in evaluating constituent compounds in a specimen

Info

Publication number: WO1994005984A1
Application number: PCT/US1993/008319
Authority: WO
Inventors: Milton R. Kaplan; John D. Cernosek
Original assignee: Micro Research, Inc.
Priority date: 1992-09-03
Filing date: 1993-09-03
Publication date: 1994-03-17
Also published as: EP0721575A4; AU5101193A; EP0721575A1; CA2143836A1

Abstract

A device and method for determining the identity and concentration of constituent compounds of a test specimen (14) based on polarization effect when the specimen (14) is subjected to randomly or partially polarized light (12). The polarization effect will cause the intensity of light passing through the specimen (14) at one angle of polarization to be different than the intensity of light exiting the specimen (14) at a second angle at a specific wavelength and will result in an elliptically polarized light. The intensity of light exiting the specimen (14) in various planes of polarization is measured by irradiating the specimen (14) with randomly or partially polarized light and then polarizing the light reflected from or passing through the specimen (14) in different planes of polarization angles and measuring (24) the intensity of light in each of the these polarization planes at one or more wavelenghts of light (Fig. 3).

Description

METHOD AND APPARATUS FOR USE OF POLARIZED LIGHT VECTORS IN EVALUATING CONSTITUENT COMPOUNDS IN A SPECIMEN

BACKGROUND OF THE INVENTION 1. Field of The Invention Applicant's invention relates to the field o spectroscopic analysis of test specimens to determine t identity and concentration of the constituent elements o compounds of the test specimen. The invention relates mo specifically to an apparatus and method for utilizing spectra transmission signatures involving polarization analysis f known compounds to identify and quantify those compounds i unknown test specimens.

2. Background Information Presently, there are several different methods employe for identifying constituent compounds in a test specimen an determining the concentration of each compound. Chemica analysis of a specimen is frequently undertaken and usuall yields excellent results. However, certain specimens including internal bodily fluids, are not particularly suite for chemical analysis, because such specimens can only b chemically analyzed by undertaking an invasive procedure—suc as drawing blood—that may be painful and entail a risk o infection. For this reason, an accurate, non-invasiv analytical method is needed for determining the identity an concentration of various compounds, such as glucose, alcoho or narcotic substances, in internal bodily fluids, such as blood. Among the most promising tools for performing a non- invasive analytical procedure is by using spectrophotometric analysis. Spectrophotometric analysis relies on the principle that every compound has a unique "pattern" determined by the amount of light absorbed (or transmitted) by the compound at different wavelengths. Typically, analytical spectro- photometric methods target the specimen with light of known intensity, and measure the absorption of light by the specimen, at various wavelengths, or conversely, measure the intensity of light passing through the specimen, at various wavelengths, and then compare this "pattern" of absorption (or intensity) at different wavelengths with the known pattern of absorption per wavelength of various compounds. Unfortunately, typical spectrophotometric analysis of a specimen is only of limited usefulness when the specimen is complex, (i.e. contains several compounds or elements), or if the density of the specimen is unknown, because absorption of light (or intensity of transmitted light) may be directly affected by these variable factors. Thus, relying solely on the absorption of light at various wavelengths does not yield a sufficiently accurate non-invasive method for analysis of bodily fluids. Certainly, the detection and measurement of other optical factors, which are unique for each compound, in addition to measurement of the absorption of light by the specimen per wavelength, would greatly improve the efficiency and accuracy of any spectroscopic technique used for determining the identity and concentration of constituent elements in a specimen. In an attempt to provide a more accurate test and overcome other limitations of conventional spectrophotometric analysis of a specimen, several procedures have been developed using polarimetric analysis. Polarimetric analysis uses polarized light rather than randomly polarized light to irradiate the specimen and relies on the principle that specimens containing an optically active compound, such as glucose, will rotate the plane of polarized light, thereby causing a measurable "shift" in the plane of polarization. The degree and direction of the polarization shift that is caused by a compound is unique for each compound. In addition, certain compounds "depolarize" polarized light in a unique manner. Thus, by irradiating a test specimen with light that is polarized in a predetermined plane and then measuring the polarization shift and/or the degree of depolarization of the light caused by the constituent components of the specimen at various wavelengths, the identity of the components in a specimen as well as the respective concentrations of the components theoretically can be more readily determined than by measuring only the absorption of light per wavelength. Examples of prior-issued patents that are known to Applicant, which relate to the use of polarized light in performing a spectroscopic analysis of a specimen, include the following: U.S. Patent No. 3,724,952 issued to Vossberg on April 3, 1973, describes an apparatus and method for polarimetric analysis of a specimen, comprising the use of light that is polarized in one plane prior to passage of the light through the specimen. After the polarized light passes through the specimen, it passes through an analyzer and detector, which determine the "polarization shift" caused by the components of the specimen, as well as the degree of depolarization and the absorption of light by the specimen. U.S. Patent No. 4,901,728 and U.S. Patent No. 5,009,230 issued to Hutchinson on February 20, 1990 and April 23, 1991, respectively, describe a device for non-invasive determination of blood glucose of a patient, by passing two orthogonal and equally polarized states of infrared light of the same intensity through a specimen and then passing the light through a polarizer to determine the rotation of the polarized light caused by the glucose in the specimen. The polarization shift is measured by calculating the difference in intensity of the two states of polarized light exiting the polarizer. U.S. Patent No. 4,011,014 issued to Tanton on March 8, 1977 describes a machine for testing the rotation of polarized light by translucent specimens, that includes a polarizer to polarize light prior to the light contacting the specimen, and then measuring the polarization shift and other optical factors, that are caused by the specimen. Each of the above-described methods and apparatuses for polarimetric analysis relies exclusively upon the principle of irradiating the specimen with light that is already polarized in a predetermined plane, and then measuring the polarization shift or other variables caused by the rotation of the polarized light by optically active compounds in the specimen. Although using polarized light to measure the "polarization" shift and/or other data dependent on the rotation of polarized light by the specimen, does provide certain information that can be objectively measured, in addition to the factors presented by standard spectrophotometric analysis, the use of light that already is polarized to irradiate the specimen has severe drawbacks. For example, polarizing the light prior to irradiating the specimen significantly decreases the amount of light actually reaching the specimen, because a percentage of the light will be reflected or absorbed by the polarizing means before the light reaches the specimen. Obviously, when the specimen is dense, this loss of light could dramatically impact the amount of light actually passing through the specimen and capable of being measured. In addition, polarizing the light in a particular plane of polarization before the light reaches the specimen, effectively eliminates all other planes of polarization in which the light travels, thereby drastically reducing the potential data that could be gathered if the light targeted on the specimen was randomly polarized light. In essence, trying to identify a compound in a complex specimen, by considering only the optical factors of light traveling through the specimen in a single plane of polarization is analogous to trying to formulate an accurate voter opinion poll by considering the opinion of only one or two persons. Obviously, the more voters that are considered, the more accurate will be the poll. The inadequacy of the limited information obtained by using polarized light to irradiate a specimen is especially evident when the specimen contains two or more compounds, because the compounds may cause similar polarization shifts in the specific polarization plane in which the light is polarized, thereby making it very difficult to determine the identity and concentration of the different compounds in the specimen. The presence of more than one compound in the specimen may also "mask" the polarization shift that is actually caused by the targeted compound sought to be identified, because the presence of other compounds in the specimen may cause an enhancement or decrease in the polarization shift at the specific polarization plane in which the light is polarized. This masking effect on the polarization shift may cause either the identity or the concentration of the targeted compound to be incorrectly determined. Measuring the polarization "shift" of light also requires that a polarizer be physically placed upstream from the specimen, to polarize the light in a specific plane of polarization prior to irradiating the specimen, and a separate polarizer/analyzer be physically placed downstream of the specimen through which light exiting the specimen is passed. This required use of two polarizers clearly causes the device to be more cumbersome and expensive than an invention that only requires the use of one polarizer. Additionally, practicing certain inventions, such as the inventions disclosed in the Hutchinson patents, that use two beams of polarized light to measure the polarization shift and other factors related to rotation of the polarized light caused by optically active elements in the specimen, complicates matters considerably, because dual mechanisms are necessary to control the optical variables for each beam, such as the intensity of light and angle of polarization. As briefly shown by the foregoing, both conventional spectrophotometric analysis and polarimetric analysis of a test specimen are severely hampered by the limited amount of data that can be obtained by merely measuring the absorption of light per wavelength by the specimen or by using polarized light to irradiate the specimen. Clearly, a method and apparatus is needed that would identify and accurately measure a wider range of optical factors than is possible by using standard spectrophotometric analysis orpolarimetric analysis. A starting point to the solution of the problem lies in the well developed electro-optical probe technologies currently in use in university, industrial, and government laboratories. The sensitivity of such probes may be increased enormously by taking advantage of the wavelength dependence of the polarized light. All wavelength components of polychromatic light are polarized, but not in the same way, and each must be examined separately. Each wavelength responds differently to a specific optically active medium. After adding the analysis of wavelength it is advantageous to add the more complex analysis of the polarization rotational characteristics that result from the irradiation of many substances, especially organic. In general, organic molecules are structured in spiraled form and have a definite helicity or handedness. It is this helicity which gives a molecule its ability to rotate the polarization of the incident light. For example, dextrose (d-glucose) is, by convention, right-handed since, when viewed from the perspective of light emerging from the sample, the polarization axis has rotated in a clockwise direction. On the other hand, levulose (fruit sugar) is left-handed since it rotates the polarization axis in a counter clockwise direction. Molecules or material which exhibit this kind of optical activity are said to possess optical rotary power. In particular, these are termed dextrorotary or levorotator respectively depending upon the action on the polarization o the incident light. The magnitude of the angle, through whic the polarization direction rotates is, in simple theory proportional to the inverse of the wavelength of the inciden light squared. Sometimes called a dispersion function, thi relationship has a weak dependence on wavelength but i strongly a function of the type of material or molecula structure being irradiated. This functional dependence on th physical properties of the medium manifests itself in th difference of the indices of refraction for right- and left handed polarized light. Two circularly polarized waves o opposite helicity form a set of basic fields for th description of any general state of polarization. As result, for example, if the polarization of the ligh irradiating the sample were purely elliptical not only woul the ellipse rotate by about an axis parallel to the directio of propagation of the light, but the ellipse also distorts its eccentricity changes. This latter phenomenon is calle circular dichroism. It is due to the different absorptio between right- and left-handed circularly polarized light. In a fluid, where there is no long-range order, th molecules are randomly oriented. Nevertheless, the effect o rotary power is not averaged out to zero. Since th constituent molecules all have a definite helicity which i the same, they cannot be brought into coincidence with thei mirror images - they are enantiomorhpous. Thus, the effect o the rotary power of an individual molecule is enhanced in fluid state. Substances which exhibit both optical rotar power and circular dichroism are referred to as chiral media. A glucose solution is an isotropic chiral substance. When plane-polarized light impinges normally on glucose th vibration ellipse of the transmitted light is different fro the vibration ellipse of the incident light. The difference is characterized by two quantities: (i) Optical rotation (OR) , which is the angle by which the transmission ellipse rotates with respect to the incidence ellipse; (ii) Circular dichrois (CD) , which is a measure of the difference in the eccentricities of the two ellipses. Profiles of the OR and the CD of an isotropic chiral substance with respect to frequency are sufficiently unique that they can be used as a component in the signature of a substance to be identified. Because the OR and the CD of any substance have been shown to be Kramers-Kronig-consistent, complete knowledge of either of the two quantities as a function of the frequency is sufficient to determine the other; therefore, the more easily measured OR is often used to characterize isotropic chiral substances. A first issue that must be addressed is that of polarization of the light incident on the biological sample whose glucose content has to be monitored. Let us suppose that the incident light is a planewave traveling in the +z direction (of a cartesian coordinate system) at a frequency f. The electric field phasor associated with this planewave may be adequately set up as

E_lnc(Z,t) = [A, U, + A-. U,] β-ⁱ**<*-^/%>, (1)

where t is time and c₀ - 3xl0⁸ m/s is the speed of light in free space; i = **(-l); (u-,, U_y, u are the unit cartesian vectors; and A, and A_y are complex amplitudes with units of V/m. Let the complex amplitudes be independent of time t. In general, Eq. (1) then represents an elliptically polarized planewave whose vibration ellipse does not change with time t. When either A » 0 or A_y « 0, the planewave is said to be linearly polarized. When A_z ■ ±iA-,, the planewave is circularly polarized. Suppose now that A, and A_y are functions of time t. Then Eq. (1) should be rewritten as

E_lnc(Z,t) = [ (t)U_x + A_y(t) U_y] _β-^l*«*-'^eo>. (2)

It still denotes a planewave, but one whose vibration ellipse changes with time t. Complicated sources have to be utilized in order to deliver specific A--(t) and A-.(t) . Indeed, the prior art devices utilize a complicated light source that yields A--(t) and A_y(t) as controllable functions of time t. The present invention, however, utilizes a source base on Quartz-Tungsten-Halogen (QTH) lamp whose output in th focal region is partially polarized. To understand the ter "partially polarized", it is best to begin by thinking abou "totally unpolarized" planewaves. The functions A,(t) an A_y(t) are continuously random functions of time for a totall unpolarized planewave, therefore the rotation of a totall unpolarized planewave by a glucose cell cannot be measured an even the concept is of no meaning. A partially polarized planewave can be thought of as combination of a totally unpolarized planewave and a elliptically polarized planewave. The second component of th partially polarized polarized wave suffers a definite rotatio on passage through a glucose cell, therefore can be used fo OR measurements. The present invention has a source that delivers a slightly polarised planewave, thus its rotation by the glucose cell is meaningful. A second issue that must be addressed is that of chromaticity. The devices described in the prior art ideally need monochromatic sources, i.e., sources whose outputs are fixed at precisely one frequency. Practical monochromatic sources cannot be ideal, instead their frequency range is very small. Suppose f_c is the center-frequency of a source and it 3-db bandwidth is denoted byΔ f; then, we can define a qualit factor

Q = f L f . (3)

The QTH lamp used in the preferred embodimentof th present invention is a white-light lamp operating from 400 t 2000 nm with a peak at 900 n ; thus, its useful frequenc spectrum ranges from 1.5x10" Hz to 7.5x10" Hz with its pea intensity at 3.3x10" Hz. As the QTH output is roughl independent of the frequency over the operating range, we ca estimate its Q = 3.3/(7.5-1.5) = 0.55. Thus, the QTH lamp i definitely a polychromatic source. The present invention also utilizes a polarization preserving analyzer whose response is flat over the 2.3x10" H to 4.3x10" Hz range, and it uses a compensated polychromati detector to measure the intensity of the beam transmitted b the analyzer. In sum, the present invention is polychromati (low-Q) , while the devices described in the prior art ar monochromatic (high-Q) . Polychromaticity has a definite advantage ove monochromaticity for such things as blood glucos measurements. The OR spectrum of a chiral solute in a non chiral solvent depends on the concentration of the solute. The amount of glucose in a (diabetic) biological sample varie with time and from sample to sample. This means that the O spectrum of a diabetic sample shifts with time. polychromatic system therefore has a much better chance o monitoring a continuously varying non-normoglycemic sampl than a monochromatic one.

SUMMARY OF THE INVENTION It is an object of the present invention to provide novel apparatus and method for accurately determining th identity and concentration of compounds contained in a tes specimen. It is another object of the present invention to provid a non-invasive apparatus and method for accurately determinin the identity and concentration of compounds contained in test specimen. it is a further object of the present invention t provide an apparatus and method for spectroscopic analysis o a specimen that is able to identify and accurately measure wider range of optical factors than is possible by usin standard spectrophotometric analysis orpolarimetric analysis. It is another object of the present invention to provid an apparatus and method that permit accurate, non-invasiv detection and concentration measurement of substances carrie in the inner bodily fluids of a test subject. It is another object of the present invention to us randomly polarized light in irradiating a test specimen i spectroscopic analysis, so as to maximize the emission o light from such specimen. It is a further object of the present invention t provide a non-invasive apparatus and method which maximize the emission of light from a test specimen undergoin spectroscopic analysis, so as to provide useful dat concerning light emissions from the specimen at multipl planes of polarized light. It is another object of the present invention to provid a non-invasive apparatus and method for accurately determinin the identity and concentration of compounds contained in test specimen, by using randomly polarized light to irradiat the test specimen and determining the extent to which th randomly polarized light is naturally polarized by th constituent components of the test specimen. It is another object of the present invention to provid an apparatus and method for accurately determining th identity and concentration of constituent compounds of a tes specimen, by irradiating the specimen with randomly polarize light and calculating the intensity of light passing throug or reflected from the specimen at various degrees o polarization and at various wavelengths. In satisfaction of these and related objectives, Applicant's present invention teaches a novel non-invasiv method and apparatus for identifying compounds in a tes specimen, such as blood, by irradiating the test specimen wit randomly polarized light and then measuring the intensity o light passing through or reflected from the specimen a various degrees of polarization and at various wavelengths. Unlike the methods and apparatuses used for standar spectrophotometric or polarimetric analysis, applicant' invention relies on the heretofore unrecognized principle tha each element or compound has a recognizable and unique patter determined by the intensity of light that it transmits o reflects at various angles of polarization and at variou wavelengths. Thus, the identity and concentration of compound can be accurately determined by determining th intensity of light passing through or reflected by th compound per degree (or smaller unit) of polarization pe wavelength. Applicant's invention permits its practitioner t more accurately determine the constituent compounds of specimen than is possible using conventiona spectrophotometric analysis or by irradiating the specime with polarized light.

BRIEF DESCRIPTION OF THE DRAWINGS Applicant's invention may be further understood from description of the accompanying drawings wherein, unles otherwise specified, like reference numbers are intended t depict like components in the various views. Fig. 1 is a perspective view of a preferred componen composition of the optical path of Applicant's invention. Fig. 2 is a graphic depiction of white light transmissio intensity along a continuum of angularly distinguishe polarization planes. Fig. 3 is a graphic depiction of the transmissio intensity of three discrete wave length bands along continuum of angularly distinguished polarization planes. Figs. 4a-b and 5a-b are graphic representations of th rotation of plane polarized light. Figs. 6a-b and 7a-b are graphic representations o circular dichroism of pure elliptically polarized light. Figs. 8a-b and 9a-b are graphic representations o circular dichroism of partially polarized light.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figure 1, utilization of Applicant' invention involves configuring an optical path (10) . Th preferred embodiment of Applicant's invention will involve th components of optical path (10) being incorporated into small, hand-held unit (not shown in the drawings) . Optica path (10) includes a light source (12). The light source (12 in the preferred embodiment of Applicant's invention is tungsten halogen lamp, but the light source (12) may be an suitably energized radiation source that creates appropriatel polarized radiation. The peak radiance of the light source i the preferred embodiment, when directed towards the detectio of glucose occurs at a value of approximately 900 nm. Th spectral range of relevance for the glucose measurements is 800 nm - 1000 nm, thus making this an ideal source. The emitted light of this source is partially polarized, but wit a dominant elliptical character due to its internal elliptically contoured reflecting mirror. In addition, randomly or partiallly polarized radiation, limited to specific range(s) of wavelengths, can be utilized through use of a light source, such as a laser source, or by the use of a monochrometer. Such a modification would be advantageous in particular applications, when a narrow frequency band of light is desired (most likely because of the particular light transmission properties of the analyzed specimens) . The second element in the set-up is an optical filter housing (13) . In the preferred embodiment, laser line filters are employed - separately - with spectral transmissions at 850 n. ; 905 nm; and 1064 nm. The next item in the optical path (10) is a test specimen (14) . The test specimen (14) may be a vial of blood or other bodily fluids or tissues or, in non-invasive tests, may be a patient's ear lobe, finger, etc. (not shown in the drawings). The sample is placed directly after the optical filter housing (13) . For in-vitro testing, the sample solution is placed in a cuvett which in turn is mounted in a cuvette holder. Within the spectral region of concern, the cuvettes should produce literally no reflection and possess greater than 98% transmission. For in-vivo testing, a rectangular finger mount is utilized and should be highly reflective to background radiation and source generated noise. A circular aperture of diameter 6.50 mm through the full width of the mount is centered on the rectangular faces allowing for the entrance and exit of light. A cylindrical finger port perpendicular to and intersecting the aperture is positioned on one side of the mount. The design of the mount should be such that there will be a constant optical path length per individual for various measurements. The constituent compounds of the test specimen (14) will naturally polarize and rotate the polarization of the beam of light passing therethrough, thereby causing the intensity value of light exiting from the test specimen (14) in a first plane of polarization to differ from the intensity value of light exiting from the test specimen (14) in a second plane of polarization and will effect a circular dichroism for the partially polarized light as described in Figs. 6a-b, 7a-b, 8a-b, and 9a-b. Conversely, in the absence of a test specimen (14) , the intensity value of light at a specific wavelength in each plane of polarization would be substantially identical and no circular dichroism would be seen. The next component of the optical path in Applicant's preferred embodiment is a convex BK-7 lens (16) Lens (16) merely serves to focus the light originating from the light source (12) and transmitted through the test specimen (14) onto an adjustable polarizer (18) . Polarizer (18) polarize the light as is transmitted through the test specimen (12) an emits the light along one or more specified polarizatio planes (20). The preferred embodiment of Applicant' invention includes a Glan Thompson polarizer as polarize (18) , because such a polarizer absorbs or reflects relatively small portion of the light passing through it an can be easily adjusted between zero and 180 degrees o rotation to coincide with any polarization plane of light a exits the test specimen (14) . An acceptable substitute for a mechanical polarizer (18) , such as the Glan Thompson polarizer, would be a electromagnetic field capable of effecting polarization of th light as exits the specimen (14) . A second convex BK-7 lens (22) is placed after th polarizer (18) to focus the light exiting the polarizer (18) onto a detector panel (24) , such as an ORIEL silicon detecto (available from ORIEL Corp.; 250 Long Beach Blvd; Stratford, CT 06497) . The detector (24) is linked to an analyzer (not shown i the drawings) , such as a standard spectrophotometric analyze or other means, to measure and analyze the intensity of th polarized light at one or more wavelengths. A preferre analyzer for this purpose is a Merlin Optical Radiatio Measuring System (also available from ORIEL Corp) . In addition to the analyzer, an oscilloscope (not show in the drawings) such as a Tech 2438 oscilloscope, may b linked to the detector (24) in the preferred embodiment o Applicant's invention, to allow a visual observation of th relative magnitude of the intensity of light being detected b the detector (24) in each of the analyzed polarization planes When the light source (12) is activated, the ligh travels the optical path and the intensity value of the ligh in a first plane of polarization is detected by the detecto (24) and is measured at one or more wavelengths by th analyzer. After this first measurement, the polarizer (18) i rotated to change the plane of polarization of the ligh emitted from the polarizer (18) to a second polarization plan and the intensity value of the light in this secon polarization plane is measured at one or more wavelengths This process of rotating the polarizer (18) to distinguish an measure the intensity of light in each of several polarizatio planes, at one or more wavelengths, is continued unti sufficient intensity values have been measured and plotted s as to establish a pattern of such intensities and of th circular dichroism relative to the particular specimen (14 under analysis. Such a pattern can be compared (preferably b computer) against known "signature curves" of polarizatio transmittance of known substances at known concentrations t make possible the identification of substance(s) in the tes specimen (14) . It should be readily apparent that certain elements o the preferred embodiment as illustrated in Figure 1, such as the BK-7 lenses (16 and 22) and the Tech 2438 oscilloscope, are not essential components of Applicant's invention, bu merely provide greater efficiency in focusing the light and i gathering and analyzing information. Previous measurements that have relied only upon linearly polarized monochromatic light, which yields a single rotational angle, have had difficulty indicating the presence of a particular substance or molecule in the host material o solution. The apparatus of the present invention approaches the problem with partially polarized polychromatic light - chromatic polarization. Each wavelength possesses a dominant polarization character; in general, elliptical. However, du to the nature of the partially polarized light, the envelop of the dominant polarization is inscribed with a series of spike-like peaks (See Figs. 8a-b and 9a-b) . If the intensity of this light is plotted as a function of the polarization angle, there would be a maximum primary peak, plus a series of secondary peaks displaced at various angles relative to the primary peak. These secondary peaks act as markers increasing the sensitivity of the apparatus of the present invention. When the light is transmitted through a chiral medium, the primary peak shifts by an angular displacement (Figs. 9a-b) . However, each secondary peak possesses its own rotational dynamic, and relative to the primary peak the secondary peaks are now displaced at different angles than before the ligh entered the chiral medium. Figures 4a-b/5a-b, 6a-b/7a-b, an 8a-b/9a-b illustrate in a step-by-step fashion the effects o optical rotary power, circular dichroism, and partia polarization. The subscript naught on the angles in thes figures indicates they are fixed. The circular dichrois distorts the shape of the ellipse and thus changes th eccentricity.

Figure 2 graphically illustrates the distribution of light intensity values (y-axis) of specimen-transmitted white light along a continuum of angularly distinguished polarization planes (x-axis) . Such plotting of the polarization plane-specific transmission intensity values at each of a plurality of polarization planes will yield a graphic pattern which is unique for that compound. As demonstrated by Figure 2, as the planes of polarization at which the light intensity value is measured increase in number, and are plotted, a pattern will emerge, one which can be compared with known patterns for identification purposes. In addition, as demonstrated by Figure 3, a different, more detailed pattern is shown in the distribution of light intensity values (y-axis) along a continuum of angularly distinguished polarization planes (x-axis) relative to wavelength-specific bands of light. Similar patterns based upon the circular dichroism effect of various compounds can be accumulated as shown in Figs. 6b, 7b, 8b, and 9b. Combining all of these various effects creates a more complex signature but results in a more accurate identification and quantification because more signature data provides a greater ability to distinguish minor variations in the composition of the test specimen. Use of any or all of these patterns allows identification of a compound in even a complex sample containing multiple compounds. This is true even though certain compounds may exhibit similar polarization patterns at specific wavelength of light, because no two compounds will exhibit identica transmission patterns at all wavelengths and in al polarization planes, nor do they exhibit the same circula dichroism. Accordingly, even though one component in a sampl may "mask" the distribution or characteristics of anothe component at one or more specific wavelengths, and/or in a fe specific polarization planes, there is little chance that thi masking effect will effectively skew an analysis involvin numerous polarization planes at several specific band width of light. it is important to further note that although the gros intensity of light passing through a specimen may var depending on density of the specimen or the concentration o the compound in the test specimen, the proportional relativ values of light transmission intensity at each of numerou polarization planes will remain substantially constant for an given compound. In other words, each birefringent compoun yields a "signature curve" of light intensity values a varying polarization planes which curve shifts in tot relative to the y-axis (non-relative, gross light intensity) depending on concentration or density of the sample. Thi shift of the "signature curve" can, in fact, be used to deriv the concentration of a constituent compound once standards fo measured compounds are known. Although the invention has been described with referenc to specific embodiments, this description is not meant to b construed in a limited sense. Various modifications of th disclosed embodiments, as well as alternative embodiments o the inventions, will become apparent to persons skilled in th art upon the reference to the description of the invention. It is, therefore, contemplated that the appended claims wil cover such modifications that fall within the scope of th invention.

Claims

We claim: 1. A device for spectroscopic analysis of a tes specimen, comprising: irradiating means for irradiating a spectroscopic test specimen with randomly polarized primary radiation, said irradiating means being placed at a first position; polarizing means located at a second position spatially separated from said first position, and oriented for receiving, as a specimen-polarized/specimen- reflected first radiation subset, that portion of said primary radiation as is reflected and polarized by said spectroscopic test specimen, and for selectively transmitting, as a second radiation subset of said primary radiation, that portion of said specimen-polarized/specimen-reflected first radiation subset as resides in one or more first polarizing means primary polarization planes; and first radiation intensity measuring means operably positioned relative to said polarizing means for receiving and measuring the radiation intensity of said second radiation subset in each of said polarizing means primary polarization planes.

2. A device for spectroscopic analysis of a test specimen, comprising: irradiating means for irradiating a spectroscopic test specimen with randomly polarized primary radiation, said irradiating means being placed at a first position; first polarizing means located at a second position spatially separated from said first position, and oriented for receiving, as a specimen- polarized/specimen-transmitted first radiation subset, that portion of said primary radiation as is transmitted and polarized by said spectroscopic test specimen, and for selectively transmitting, as a second radiation subset of said primary radiation, that portion of said specimen- polarized/specimen-transmitted first radiation subset as resides in one or more first polarizing means primary polarization planes; and first radiation intensity measuring means operably positioned relative to said first polarizing means for receiving and measuring the radiation intensity of said second radiation subset in each of said first polarizing means primary polarization planes.

3. The device of claim 1, wherein said polarizing means is user adjustable between said polarizing means primary polarization planes to polarizing means secondary polarization planes, said polarizing means secondary polarization planes being angularly distinct from said polarizing means primary polarization planes.

4. The device of claim 2, wherein said first polarizing means is user adjustable between said first polarizing means primary polarization planes to first polarizing means secondary polarization planes, said first polarizing means secondary polarization planes being angularly distinct from said first polarizing means primary polarization planes.

5. The device of claim 1 further comprising a monochrometer located at a fourth position and oriented for intercepting said randomly polarized primary radiation emitted by said irradiating means prior to irradiation of said spectroscopic test specimen and transmitting a subset of said randomly polarized primary radiation having a narrower wavelength band.

6. A method for performing a spectroscopic analysis o st specimen, comprising the steps of: selecting a spectroscopic test specimen to be analyzed; selecting a device, comprising: irradiating means for irradiating a spectroscopi test specimen with randomly polarized primar radiation, said irradiating means being placed at a first position; first polarizing means located at a second position spatially separated from said first position, and oriented for receiving, as a specimen- polarized/specimen-transmitted firstradiation subset, that portion of said primary radiation as is transmitted and polarized by said spectroscopic test specimen, and for selectively transmitting, as a second radiation subset of said primary radiation, that portion of said specimen- polarized/specimen-transmitted first radiation subset as resides in one or more first polarizing means primary polarization planes; and first radiation intensity measuring means operably positioned relative to said first polarizing means for receiving and measuring the radiation intensity of said second radiation subset in each of said first polarizing means primary polarization planes; operably placing said spectroscopic test specimen in the path of irradiation of said irradiating means; dnergizing said irradiating means, causing said irradiating means to emit said randomly polarized primary radiation; and measuring the intensity of said second radiation subset in each of said first polarizing means primary polarization planes.

7. The method of claim 6, wherein said first polarizing means is user adjustable between said first polarizing means primary polarization planes to first polarizing means secondary polarization planes, said first polarizing means secondary polarization planes being angularly distinct from said first polarizing means primary polarization planes.

8. The method of Claim 6 wherein said device further comprises: a monochromater located at a fourth position and oriented for intercepting said randomly polarized primary radiation emitted by said irradiating means prior to irradiation of said spectroscopic test specimen and transmitting a 1 subset of said randomly polarized primary

2 radiation having a narrower wavelength band. 3

4 9. The method of claim 7 further comprising the step

5 of measuring the intensity of said second radiation

6 subset in each of said first polarizing means

7 secondary polarization planes. 8

9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 10. A device for spectroscopic analysis of a test specimen, comprising: irradiating means for irradiating a spectroscopic test specimen with partially polarized primary radiation, said irradiating means being placed at a first position; polarizing means located at a second position spatially separated from said first position, and oriented for receiving, as a specimen-polarized/specimen- reflected first radiation subset, that portion of said primary radiation polarized and rotated by said spectroscopic test specimen, and for selectively transmitting, as a second radiation subset of said primary radiation, that portion of said specimen-polarized/specimen-reflected first radiation subset as resides in one or more first polarizing means primary polarization planes; and first radiation intensity measuring means operably positioned relative to said polarizing means for receiving and measuring the radiation intensity of said second radiation subset in each of said polarizing means primary polarization planes.

11. A device for spectroscopic analysis of a test specimen, comprising: irradiating means for irradiating a spectroscopic test specimen with partially polarized primary radiation, said irradiating means being placed at a first position; first polarizing means located at a second position spatially separated from said first position, and oriented for receiving, as a specimen- polarized/specimen-transmitted first radiation subset, that portion of said primary radiation as is transmitted and polarized by said spectroscopic test specimen, and for selectively transmitting, as a second radiation subset of said primary radiation, that portion of said specimen- polarized/specimen-transmitted first radiation subset as resides in one or more first polarizing means primary polarization planes; and first radiation intensity measuring means operably positioned relative to said first polarizing means for receiving and measuring the radiation intensity of said second radiation subset in each of said first polarizing means primary polarization planes.