WO2015167417A1 - Système de mesure optique présentant un détecteur de réseau et élément de réflexion interne intégré - Google Patents

Système de mesure optique présentant un détecteur de réseau et élément de réflexion interne intégré Download PDF

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Publication number
WO2015167417A1
WO2015167417A1 PCT/US2014/033322 US2014033322W WO2015167417A1 WO 2015167417 A1 WO2015167417 A1 WO 2015167417A1 US 2014033322 W US2014033322 W US 2014033322W WO 2015167417 A1 WO2015167417 A1 WO 2015167417A1
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WIPO (PCT)
Prior art keywords
face
prism
incident
detector
atr
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PCT/US2014/033322
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English (en)
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Pandata Research Llc
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Priority to PCT/US2014/033322 priority Critical patent/WO2015167417A1/fr
Publication of WO2015167417A1 publication Critical patent/WO2015167417A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/55—Specular reflectivity
    • G01N21/552—Attenuated total reflection
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/02—Details of sensors specially adapted for in-vivo measurements
    • A61B2562/0233—Special features of optical sensors or probes classified in A61B5/00
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
    • A61B5/14532—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue for measuring glucose, e.g. by tissue impedance measurement

Definitions

  • the present disclosure relates generally to methods and apparatus for spectroscopic evaluation of a sample, and more particularly relates to internal reflection element assemblies comprising an integrated array detector, and further to optical measurement systems including such assemblies.
  • optical techniques are known for characterizing a sample, several of which involve launching a beam of electromagnetic radiation at the sample under a particular set of conditions, and measuring radiation reflected from the sample. Some techniques tailor the set of conditions toward measuring a particular structure. For instance, ellipsometry makes use of polarization state to perform measurements, and is particularly useful for measuring the refractive indices and the layer thicknesses for thin film structures. As another example, interferometry makes use of coherent light interference to perform
  • a spectrometer In order to detect the composition of a sample, or the presence of a particular constituent in that composition of a sample, or to measure a concentration of such a particular constituent in a sample, a spectrometer may be used.
  • power reflectivity is measured from the sample at a plurality of different wavelengths, at least one of which is sensitive to the presence of the selected constituent. The ratio of the measured reflectivity between at least two such wavelengths, yields information about the presence and/or concentration of the constituent.
  • a measurement of a particular analyte in a human or animal bloodstream typically requires that the electromagnetic radiation penetrate into the sample a threshold distance, interact with the analyte in the blood, return to the surface, and be collected by a measurement apparatus.
  • the electromagnetic radiation can penetrate a wrapper or a surface coating.
  • the electromagnetic radiation employed for such detection/measurement will be in the infrared (IR) spectrum.
  • IR infrared
  • Attenuated total reflection (ATR) spectroscopy is especially well-suited for many forms of sample analysis, and methods have been proposed for implementing operational processes to obtain measurements at varying depths below the surface of a sample.
  • electromagnetic radiation such as in the IR band
  • this radiation penetrates into the sample to depths substantially greater than would be achieved by launching the electromagnetic radiation at lesser (or greater) angles further removed from the critical angle.
  • This disclosure addresses methods and apparatus for measuring optical properties of a sample through attenuated total reflection (ATR) spectroscopy which are particularly well-adapted for use with ATR conducted at a plurality of incident angles relative to the sample under investigation, though their applicability is not limited to such use.
  • ATR attenuated total reflection
  • a beam of electromagnetic radiation is directed to an interface between an internal reflection element and a sample, and the amount of optical power reflected from the interface is measured.
  • the beam is directed at the interface at an incident angle greater than the critical angle, most of the beam is reflected due to total internal reflection at the interface, a small fraction of the beam is absorbed by the sample, and the absorbed fraction provides information that can characterize the sample.
  • the internal reflection element is configured to receive an at-least- partially- collimated input radiation beam which will propagate within the internal reflection element as an internal beam.
  • the internal beam follows a path having multiple reflections inside the internal reflection element, which occur between an ATR face of the prism (which engages the sample under investigation) and a detector face of the prism.
  • a detector comprising a spatial array of pixels (i.e. an "array detector") is secured in fixed relation proximate the detector face to sense, for each reflection of the internal beam off the detector face, both the position of incidence of the internal beam at the detector face and the intensity of the internal beam.
  • FIG. 1 is a side-view drawing of an example of a prism depicted in contact with a tissue sample, in combination with examples of additional system components.
  • FIG. 2 is a perspective drawing of the prism of FIG. 1 , with an example of an optical path traced therethrough.
  • FIG. 3 is a flowchart of an example of a measurement process.
  • ATR attenuated total reflection
  • the example methods and apparatus disclosed herein are configured to facilitate directing an electromagnetic beam to intersect a sample at a plurality of incident angles.
  • measurements will be made through use of a plurality of radiation wavelengths.
  • the measurements typically involve directing the electromagnetic beam at an incident angle toward the sample, capturing the light reflected from the sample, and recording the reflected light value as a power reflectivity.
  • Power reflectivity values can vary between 0% and 100%.
  • the output of such measurements is typically a power reflectivity as a function of angle.
  • the measurements are typically repeated for a range of incident angles and/or a range of wavelengths. It will be understood that the device and method discussed herein may be used at various incident angles, both near the critical angle and away from the critical angle.
  • the measured values may be used to determine the presence and/or the concentration level of a particular analyte in the blood, such as alcohol or glucose. It is assumed that the lookup and calculation processes may be performed in a manner known to those of ordinary skill in the art.
  • the present application discusses configurations of the internal reflection element that contacts a sample, and the associated detection elements.
  • a “prism” is used in this disclosure synonymously with the term “internal reflection element”; and the term is not used to imply any particular number of surfaces or other configuration to the structure, which is in accordance with well-known usage within the art. Both terms describe a solid object having one or more flat surfaces, which is generally transparent in a particular wavelength region. Therefore, a “prism,” as described herein, may be formed in any suitable shape, so that the surfaces may have a suitable size and orientation with respect to each other to define and
  • Prisms are typically formed as singular elements, although they may optionally be formed as discrete elements that are joined together. In some examples, the discrete elements may be formed from different optical materials.
  • a sample is placed into contact with a designated surface of the prism.
  • the sample will be human or animal tissue.
  • the applicability of the described methods and apparatus are, however, in no way limited to this type of application, and may be used for virtually any application where spectroscopy may be used, and where investigation beneath the surface of a sample is desired.
  • the sample will be placed in contact with a measurement face of the prism. In many applications, this will be by a patient placing a particular location of the patient's body into contact with the measurement face on the prism; a measurement will be made; and the patient will be able to freely remove the body part when the measurement is completed. Because there is no penetration of the patient's skin, such as to draw blood, the measurement is non-invasive.
  • the electromagnetic radiation will be delivered to and from the measurement face from within the prism.
  • many systems will employ IR radiation, though the described techniques are not limited to such wavelengths.
  • the material being evaluated and the constituents of interest will influence the wavelengths of radiation to be chosen for a particular measurement. Because the current examples are referring to radiation in the IR wavelengths, the radiation will also be referred to here as "light” or as a "beam" for convenience of reference.
  • an example system will include a prism in integrated relationship with an array detector, with a light source and with one or more processing units to receive and/or process the obtained measurements.
  • light will be provided by the light source to the prism, and will be coupled into the prism by transmission through one of the prism faces.
  • the light from the source will therefore be communicated from a location external to the prism to an entry location on such prism, and from there will propagate as an internal beam within the prism.
  • the system will be configured to provide angular adjustment between the identified location external to the prism and the entry location on the prism.
  • This angular adjustment may be achieved through use of one or more of various mechanisms, including rotating (or otherwise moveable) stages for changing position of either the prism or the source relative to the other; or, in many examples, use of a rotatable mirror or other beam deflection mechanism to deflect the light beam from the source relative to the identified location on the prism where the beam enters the prism.
  • the light will undergo one or more reflections off particular prism surfaces. Some of the reflections may be partial reflections, with a corresponding partial transmission of the light onto an array detector. In addition, there may optionally be multiple reflections off particular surfaces of the prism, possibly with several partial transmissions onto the array detector.
  • the light inside the prism is partially transmitted onto the array detector at least twice, including one transmission before the light reflects off the measurement face, and one transmission after reflection off the measurement face.
  • the transmissions onto the array detector may be referred to herein as "imprints.” For example, if a particular beam strikes the array detector three times at three different locations on the detector, the beam may be said to form three "imprints" on the array detector at the respective locations at which the beam strikes the detector. It will be preferable to have some spatial separation for different imprints on the array detector in order to tell one imprint from another, and the example configurations described later herein facilitate such spatial separation of the imprints.
  • directing the light to form two (or more) imprints on the array detector provides two pieces of information.
  • a total reflectance off the measurement face may be calculated, by summing separately the intensities on the pixels from the first and second imprints (i.e., the imprints before and after a reflection off the measurement face), and dividing the sum of the intensities on the pixels from the second imprint (i.e., the imprint after reflection off the measurement face) by the sum of the intensities on the pixels from the first imprint (i.e., the imprint before the reflection off the measurement face).
  • the result is a ratio that falls between 0 and 1, or between 0% and 100%.
  • an incident angle on the measurement face may be calculated, by finding the beam locations for each imprint, and using the geometry of the prism to calculate an incident angle on the measurement face. Calculation of the incident angle in this manner may be more accurate than attempting to measure the incident angle based on movement of the optical elements located upstream.
  • Each measurement may therefore yield a reflectance and a corresponding incident angle.
  • the incident angle at the sample may be varied. In many examples, by repeating the reflectance measurements, with each measurement
  • the device may obtain a portion of a curve of reflectance versus incident angle. This curve can be used to identify the critical angle measurement, and therefore the measurement with the greatest depth of penetration into the sample. The reflectance measurement at the greatest depth of penetration may then be compared to a reference value or measurement to identify a particular analyte at a relative depth in the tissue sample and/or the concentration of such analyte.
  • FIGS. 1 and 2 depict an example system from differing perspectives as identified earlier herein.
  • FIG. 1 is a cross-sectional representation of an example prism 100, which is in contact with a tissue sample 102, in combination with other system components.
  • FIG. 2 depicts a perspective view of the prism 100 of FIG. 1, with a highlighted optical path (P) within the prism 100.
  • the prism 100 for use with the systems and methods described herein has a cross-section, taken in the plane of the page in FIG. 1, that includes four sides arranged as a trapezoid, as shown in FIG. 1.
  • a sample 102 is placed in contact with one of the four sides, which is referred to herein as an "ATR face” 104.
  • a second of the four sides is a “detector face” 106, which is disposed opposite the ATR face 104, and is generally parallel to the ATR face 104 to within typical manufacturing tolerances.
  • a longitudinal axis of the prism 100, denoted as "A" is parallel to both the ATR face 104 and the detector face 106.
  • the remaining two faces of the prism are disposed at opposite longitudinal ends of the prism, and include an incident face 110 and an absorbing face 112.
  • both the incident face 110 and the absorbing face 112 are angled, with respect to the ATR face 104 and the detector face 106, with the angling occurring within the plane of the page of FIG. 1.
  • a cross-section of the prism may have more than four sides.
  • the ATR face 104, the detector face 106, the incident face 110, and the absorbing face 112 have surface normals denoted as SN1 0 4, SN1 06 , SNno, and SN112, respectively.
  • the surface normals SN104, SN106, SNno, and SNm are all coplanar, and are all disposed within the plane of the page of FIG. 1.
  • the plane of the page is an incident plane that includes the longitudinal axis (A) and is perpendicular to the ATR face 104.
  • one or more of the surface normals extend out of the plane of the page of FIG. 1.
  • the ATR face 104 is capable of sustaining attenuated total reflectance with the sample material. During the measurement, when the sample 102 is in contact with the ATR face 104, light strikes the ATR face 104 at a particular incident angle determined by the geometry of the prism 100 and the entrance angle of the incident beam.
  • the critical angle is given by the numerical value of sin "1 (n samp i e / n pr i S m), where n samp i e and n pr ism are the refractive indices of the sample 102 and prism 100, respectively.
  • the precise angles used may vary as a function of the wavelengths used and the nature of the investigation. In some systems, the utilized angles of incidence may be at a desired increment within a range of up to approximately two degrees to one side, or to both sides, of the critical angle.
  • the range of angles may be substantially less, for example, less than a degree (or even half-degree) to one side, or to both sides, of the critical angle, and potentially in increments as small as milli-degree increments through at least a portion of that range.
  • an "expected" value for the refractive index of the sample will preferably be determined, either specifically in reference to that sample, or by prior experimental evaluation of a plurality of comparable samples.
  • the expected value may be included within a range of possible measured values.
  • Such determination of an approximate refractive index can in some cases, if it is sufficiently accurate, narrow the range of angles of incidence that must be examined.
  • the prism material will be selected to have a refractive index n pr i S m greater than the expected value of the refractive index of the sample nsampie*
  • a series of measurements is taken for a variety of incident angles, each of which measures the amount of light reflected at the ATR face 104.
  • the quantity being measured is the power reflectivity, which is sometimes referred to as a power reflectance.
  • the power reflectivity can vary between 0 and 1, or 0% and 100%. In most examples, the values measured will be close to 100%, with the difference between the measured value and 100% corresponding to the amount of light absorbed by the sample.
  • the incident face 110 of the prism 100 is configured to receive an incident beam from upstream optical components, to allow the incident beam to refract through the incident face 110, and to allow the refracted incident beam to propagate within the prism 100 as an internal beam.
  • the optical paths of the incident beam and the internal beam are collectively denoted as P in FIGS. 1 and 2.
  • an anti-reflection coating 110A on an exterior surface of the incident face 110 is achieved by an anti-reflection coating 110A on an exterior surface of the incident face 110.
  • the precise coating used will typically be dependent on the wavelengths of the light contemplated to be used, the incident angles a at which the incident light strikes the incident face 110, and in some cases the
  • composition of prism 100 includes one or more dielectric materials.
  • the incident face 110 is uncoated.
  • the incident face 110 is angled so that the surface normal to the incident face, SNno, extending into the prism 100, intersects the ATR face 104. (The intersection is not shown explicitly in FIG. 1, but would occur if the surface normal to the incident face, SNno were extended further inside the prism 100.)
  • the angling of the incident face 110 is selected to allow upstream optical components, such as the components that produce and position an incident light beam on the incident face 110, to be disposed within a convenient location within a packaged system.
  • an incident beam on the prism 100 is roughly perpendicular to the ATR face 104 (allowing for a pivoting of the incident beam during operation by a few degrees in either or both directions away from perpendicularity to the ATR face 104).
  • Such an example orientation may allow the optical components of the system to be packaged in a relatively compact footprint underneath the ATR face 104 (e.g., having a relatively small left-to-right extent in the view of FIG. 1).
  • the incident face 110 may be angled in the opposite direction; such an orientation may allow the incident beam to have an angular orientation relatively close to the longitudinal axis (A), which may be useful if it is desired that the packaged optical system be relatively thin (e.g., having a relatively small top-to- bottom extent in the view of FIG. 1).
  • the detector face 106 of prism 100 reflects a fraction of the incident light back toward the ATR face 104 and transmits a fraction of the incident light to an array detector 108 that, as noted earlier herein, will be secured in fixed relation to the detector face 106 of the prism 100.
  • the detector face 106 may also be parallel to ATR face 104.
  • the detector face 106 may also have a thin coating 106A thereon to facilitate the identified partial transmissivity and partial reflectivity.
  • the precise coating used will typically be dependent on the wavelengths of the light contemplated to be used, the incident angle at which the internal beam strikes the detector face 106, and in some cases the composition of prism 100.
  • the coating on the detector face may be made from a metal, such as gold.
  • the coating may include one or more dielectric materials, and/or may include alternating layers of relatively high and relatively low refractive index materials. The coating 106 A does not overcome any conditions of total internal reflection, but merely can adjust the fraction of light directed toward the detector.
  • the coating 106A can be a graded coating, which has a reflectivity that decreases over the length of the prism. Such a graded coating can keep the imprints on the detector relatively close in intensity, which can more effectively use the dynamic range of the detector.
  • the detector face 106 coating may transmit a relatively small fraction of the incident light.
  • Such a low transmissivity may be desirable for either of two reasons: first, the low transmissivity may reduce the effects of light that reflects off the detector surface, and may prevent such reflected light from entering back into the prism 100; and second, the low transmissivity may be beneficial for particular detectors that operate best at relatively low light levels.
  • the array detector 108 will be secured directly to the prism 100.
  • the prism 100 and array detector 108 might be coupled to a common structure that will support the two components in a desired, fixed relation to one another. Regardless of the specifics of how the array detector is secured in fixed relation to the detector face, by virtue of such fixed relation the two components are integrated into an assembly in which the detector can consistently measure both the intensity of the light beam at each imprint at the detector and the position of each imprint.
  • the partially transmissive coating will extend along the detector face 106 at least where the beam is contemplated to imprint on the array detector 108.
  • the array detector 108 is optically bonded to detector face 106.
  • the array detector 108 is immersed in refractive index-matching material that has a refractive index greater than or equal to that of the sample 102; this condition can allow light to overcome the condition of total internal reflection and exit the prism 100 at the detector face 106, for all ranges of the incident angles at the ATR face 104.
  • the array detector 108 can be fabricated directly onto the prism 100.
  • the array detector 108 may be a commercially available model, or a straightforward modification to a commercially available unit. For instance, there are some commercially available sensors that use mercury cadmium telluride (“MCT”), or HgCdTe. These are cooled detectors that work in the infrared spectrum discussed herein. The sensors are available off-the-shelf in a 640 pixel by 480 pixel design, with a 12 ⁇ pixel-to-pixel pitch; and also in a 1000 pixel by 720 pixel design, having a 500 Hz scanning frequency with a either a 5 or 10 ⁇ pixel-to-pixel pitch. It is straightforward to use the sensor technology of these MCT sensors with a custom size and shape for the array detector. While array detector 108 will beneficially be formed as a single detector, in some cases, it may be formed from multiple smaller array detectors (for example, from multiple discrete semiconductor devices) cooperatively both physically coupled and electrically configured to effectively form a single detector.
  • MCT mercury cadmium telluri
  • the senor may be made as a one-dimensional array, with each pixel in the sensor having its long dimension in the x-y plane and having its short dimension along the longitudinal z-axis.
  • Such a 1-by-N array of pixels would be able to record the intensity and location along the longitudinal z-axis of each bounce of the internal beam off the detector face 106.
  • the array detector 108 will receive a light imprint from each bounce off the detector face 106. As noted earlier herein, it is preferable that the light imprints on array detector 108 be spatially separated. From adjacent light imprints, the location information, along with a predetermined geometry of the prism 100, may be used to provide a calculated value of incident angle off the ATR face 104. Likewise, from adjacent light imprints, the intensity information may be used to calculate a power reflectivity from the ATR face 104.
  • FIG. 2 shows the optical path P for the internal beam inside the prism
  • the beam enters the prism 100 at the incident face 110, then alternately reflects off the ATR face 104 and the detector face 106, then terminates at the absorbing face 112.
  • the internal beam reflects off the ATR face 104 at locations 206, 208, and 210.
  • the internal beam reflects off the detector face 106 at locations 202 and 204; which are representative of the location of the "imprints" on the array detector 108. As noted earlier herein, it is preferable that the light imprints on array detector 108, at locations 202 and 204, be spatially separated.
  • the location information may be used to provide a calculated value of incident angle off the ATR face 104.
  • the intensity information may be used to calculate a power reflectivity from the ATR face 104.
  • the optical path (P) remains in a single plane, including both the beam incident on the incident face 110 and the internal beam propagating inside the prism 100.
  • Such a single plane may include the plane of incidence, which is parallel to the longitudinal axis (A) and is perpendicular to the ATR face 104.
  • prism and beam geometries may also include more or fewer than three reflections off the ATR face 104, and/or more than two reflections off the detector face 106.
  • the cross-section of the prism 100 taken perpendicular to the longitudinal axis (A), is the same at each location along the longitudinal extent of the prism 100 between the incident face 110 and the absorbing face 112.
  • the cross-section may be referred to as generally uniform, meaning that the prism 100 may have typical manufacturing tolerances on the sizes and orientations of the various faces. It is intended that the cross-section be truly uniform at each point along the longitudinal axis, even if real parts may vary slightly from part- to-part due to manufacturing tolerances.
  • the prism 100 has a rectangular cross section, taken perpendicular to the longitudinal axis (A).
  • the prism 100 may have a cross-section that is square, hexagonal, trapezoidal, polygonal, or is another suitable shape.
  • the location 122 at which the beam enters the prism 100 may translate across the incident face 110, provided that the beam does not become clipped upon entry into the prism 100 or during its propagation along the optical path P, and provided that the beam does not translate off the sample at the ATR face 104. It is intended that the beam remain roughly in a single plane during propagation through the prism 100.
  • the internal beam After reflecting alternately between the ATR face 104 and the detector face 106, the internal beam strikes the absorbing face 112 in the prism 100, which is at the opposite longitudinal end of the prism 100 from the incident face 110.
  • the absorbing face 112 is intended to completely absorb the internal beam, so that reflections from the absorbing face 112 are minimized. In many examples, this high absorption will be achieved by a coating on the exterior surface 112A of the absorbing face 112. As will be apparent to those skilled in the art, the precise coating used will typically be dependent on the wavelengths of the light contemplated to be used, and in some cases the composition of prism 100.
  • the high- absorption coating may have a relatively thick metallic portion, and an anti-reflection portion disposed between the metallic portion and the prism material.
  • the metallic portion absorbs the light, so that essentially no light transmits through the metallic portion, and the anti-reflection portion minimizes any reflections that would have otherwise arisen at the interface between the prism material and the metallic material.
  • other suitable absorbing materials and structures may be used.
  • the absorbing face 112 may direct all or a portion of the internal light out of the prism 100, which can prevent internal reflections within the prism from directing stray light onto the detector.
  • an absorber can be disposed on any or all of the faces of the prism proximate absorbing face 112.
  • location 206 on the ATR face 104 can be coating with a high-reflection coating.
  • a high-reflection coating can direct all or nearly all of the incident light onto location 202 on the detector.
  • the intensity at location 202 can therefore provide a reference signal for the beam intensity, which is independent of a presence or absence of a sample, and of any properties of such a sample.
  • Such a high-reflection coating at location 206 can also be used for calibrating a system that uses the prism 100.
  • a light source 132 produces a collimated light beam that propagates along an optical path (P).
  • Suitable light sources can include one or more semiconductor lasers, one or more light emitting diode, a combination of semiconductor lasers and light emitting diodes, and suitable collimating optics.
  • one or more mirrors and/or one or more lenses can also be used to direct the collimated light into the prism at the specified location, and with the specified range of incident angles.
  • the light source 132 and mirrors 134, 136 may collectively be referred to as a beam emitter assembly 130.
  • the beam produced by the beam deflection assembly 130 has variable insertion angle a, formed with respect to a surface normal SNno from the incident face 108 of the prism 100.
  • An example processing unit 120 controls the light source 132 and the repositionable mirrors 134, 136.
  • the processing unit 120 can also receive and process measurements from the array detector 108.
  • the processing unit 120 can include one or more processors, in combination with additional hardware as needed (volatile and/or no n- volatile memory; communication ports; I/O device(s) and ports; etc.) to provide the control functionality as described herein, such as incrementally incrementing the angle of beam deflection assembly 130 to vary the insertion angle a of the incident beam on prism 100; and also to process the measurements from the array detector 108.
  • Such processing will include performing the identified correlations to determine the presence and/or concentration of constituents in the sample (such as analytes in the blood in the described examples). These functions may be implemented by separate processing units, as desired, and additional functions may be performed by such one or more processing units.
  • a system can include one or more lenses that image the ATR face onto the array detector.
  • a lens can be disposed between the prism and the array detector.
  • the lens can be made separately from the prism and attached to the prism.
  • the lens can be made integral with the prism, or made integral with the array detector.
  • FIGS. 1 and 2 it is worthwhile to describe use of the prism 100 in an example method that can measure the reflectance at the ATR face 104 as a function of incident angle. Once the reflectance data as a function of incident angle has been obtained, an analysis for the presence and/or concentration of a particular analyte may be performed.
  • FIG. 3 is a flow chart of an example method 300 for performing the reflectivity measurement.
  • the method provides for the interrogation of the sample with multiple wavelengths of light and multiple angles of incidence.
  • either only a single series of measurements might be performed at a single wavelength but at different angles of incidence.
  • measurements can be made at a plurality of wavelengths, and these will be made in two discrete series (i.e., a series of measurements will be made at a plurality of angles of incidence with a first wavelength of light, followed by a similar series with a second wavelength of light).
  • the example method 300 begins at 302 with a sample being placed in contact with the ATR face 104 of the prism 100.
  • the example method continues by selecting an initial wavelength and an angular orientation for a beam produced by the beam emitter assembly 130.
  • the beam emitter assembly 130 generates the beam at the particular wavelength and angular orientation as selected at 304.
  • the beam produced at 306 is directed into the prism 100.
  • the incident angle and the power reflectance are measured from the sample.
  • the spacing of imprints of the beam on the detector may be used to determine the incident angle of the beam at the ATR face.
  • the reflectance curve resulting from the plurality of power reflectance measurements may be used to determine the presence and/or concentration of a constituent in the sample (in the examples, a blood analyte).
  • the wavelength and the angular orientation of the beam are iterated, so that the wavelength and/or the angular orientation may subtend a predetermined range. As noted above, either the wavelength or the angular orientation may be iterated first, while the other quantity is held constant or is also iterated.
  • the beam is generated with the iterated quantities. Once the full ranges of wavelengths and angular orientations have been covered, and measurements taken at each wavelength and angular orientation, the sample may be removed at 314.
  • the pixels can be summed for each bright spot to arrive at intensity value before and after reflection off the ATR face 104.
  • the reflected intensity after reflection can be divided by the reflected intensity before reflection to arrive at a power reflectivity value, which lies between 0% and 100%.
  • the pixel values may be first fit to a smooth curve, and the smooth curve may be used to provide the intensity values.
  • each bright spot can be curve-fit to a known beam profile that is emitted by the beam emitter assembly 130.
  • the known beam profile is a Gaussian distribution, in some examples with the same width in both directions, and in other examples with differing widths in different directions.
  • the known beam profile is a Gaussian distribution along one axis, and is a Lorentzian distribution along the opposite axis.
  • a smooth curve can be curve-fit, without any expected distribution, to find a good approximation of the intensity profile.
  • the angle of incidence may found from simple trigonometry. In general, the angle of incidence is found by taking one half the bounce-to- bounce spacing, dividing it by the detector-to-ATR face spacing, and taking the inverse tangent of the resulting quantity. For more complicated prism geometries, similar trigonometric relationships hold.
  • the beam emitter assembly 130 which can produce a collimated beam at a desired wavelength, and can inject the collimated beam into the prism 100 at a desired location with a desired incident angle. While an essentially fully collimated beam may be desirable for many measurements, for other measurements, the collimation may be less than essentially total (within practical limits) and still provide satisfactory results.
  • the described "light” will be understood to be an at least partially collimated beam of radiation (in these examples, in the IR band). In general, the desired location may remain the same for all or some of the incident angles.
  • a suitable light source 132 may be a quantum cascade laser. Such lasers typically operate at room temperature.
  • the output of a quantum cascade laser is typically collimated with a finite and well-defined beam profile.
  • the beam may be elongated, with different diameters along different axes.
  • an at least partially collimated beam from the laser is produced, it is straightforward to divert the beam using one or more electrically controllable pivotable mirrors 134, 136 (or other deflection assembly that can include one or more lenses) to achieve a desired range of incident angles on the prism 100.
  • Such mirrors will be moveable relative to at least one axis, and for many systems, preferably relative to multiple axes.
  • the beam movement may be controlled by positioning the pivotable mirrors 134, 136 in such a manner to minimize or eliminate movement of the beam as the incident angles are varied.
  • the example prism 100 and disclosed example system are particularly well-suited to detecting analytes that do not lie at the surface of the skin or of a tissue sample, but are present at some shallow depth below the surface, typically within several wavelength of the incident light. For instance, detection of blood alcohol or blood glucose concentration may be addressed by the prism 100 and system, which can direct suitable evanescent waves to the depth of suitable blood vessels for the appropriate measurements.
  • blood alcohol and blood glucose measurements are mentioned herein as examples; it will be understood that other analytes and/or their concentrations may be detected in a similar manner, using a suitable portion of the spectrum, and using optical materials and geometry that accommodate those wavelengths.
  • the prism 100 In order to achieve total internal reflection at the interface between the prism 100 and the sample 102, the prism 100 should have a refractive index greater than that of the sample.
  • the refractive index is typically between about 1.15 and about 1.7 over a wide range of wavelengths, from about 0.2 ⁇ to about 11 ⁇ . At wavelengths in the mid-infrared spectrum (about 2.5 ⁇ to about 25 ⁇ ), a reasonable
  • suitable materials for the prism 100 can include zinc selenide (ZnSe), having a refractive index of about 2.43 at wavelength of 5 ⁇ , germanium (Ge), having a refractive index of about 4.0 at a wavelength of 5 ⁇ , CVD diamond, having a refractive index of 2.38 at a wavelength of 10 ⁇ , or
  • PMP polymethylpentene
  • Other common materials used for the prism 100 in the mid-IR spectrum are synthetic sapphire, having a refractive index of about 1.6 at a wavelength of 5 ⁇ , and cubic zirconia stabilized with yttria ( ⁇ 0 2 - ⁇ 2 0 3 ), having a refractive index of about 2.0 at a wavelength of 5 ⁇ .
  • yttria ⁇ 0 2 - ⁇ 2 0 3
  • refractive index of about 2.0 at a wavelength of 5 ⁇ For wavelengths in the visible spectrum (about 400 nm to about 700 nm) or near- infrared spectrum (about 1.5 ⁇ to about 2.5 ⁇ ), more common optical glasses may be used, many of which have relatively high refractive indices of about 1.5 to about 1.9.

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Abstract

La présente invention concerne un prisme qui est conçu pour recevoir un faisceau collimaté et pour propager un faisceau interne qui suit un chemin présentant de multiples réflexions à l'intérieur du prisme. Les multiples réflexions se produisent entre une face ATR et une face de détecteur du prisme. Un détecteur de réseau est attaché dans une relation fixe au prisme à proximité de la face de détecteur, afin de détecter une position interne du faisceau interne et une intensité du faisceau interne pour chaque réflexion du faisceau interne depuis la face de détecteur.
PCT/US2014/033322 2014-04-08 2014-04-08 Système de mesure optique présentant un détecteur de réseau et élément de réflexion interne intégré WO2015167417A1 (fr)

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WO2018123169A1 (fr) * 2016-12-26 2018-07-05 三菱電機株式会社 Dispositif et procédé pour mesurer la matière biologique
JP2019130283A (ja) * 2018-09-07 2019-08-08 三菱電機株式会社 生体物質測定装置
WO2020068256A1 (fr) * 2018-09-30 2020-04-02 Agilent Technologies, Inc. Système d'étalonnage de spectrométrie de réflexion totale atténuée

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WO2006079797A2 (fr) * 2005-01-28 2006-08-03 Melys Diagnostics Limited Dispositif permettant de mesurer la concentration d'un melange a analyser
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US20010030288A1 (en) * 2000-03-10 2001-10-18 Wilks Enterprise, Inc. Spectroscopy analyzer using a detector array
WO2006079797A2 (fr) * 2005-01-28 2006-08-03 Melys Diagnostics Limited Dispositif permettant de mesurer la concentration d'un melange a analyser
US20110001965A1 (en) 2008-02-01 2011-01-06 Messerschmidt Robert G Methods, devices and kits for peri-critical reflectance spectroscopy
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018123169A1 (fr) * 2016-12-26 2018-07-05 三菱電機株式会社 Dispositif et procédé pour mesurer la matière biologique
JPWO2018123169A1 (ja) * 2016-12-26 2019-10-31 三菱電機株式会社 生体物質測定装置および生体物質測定方法
US11197614B2 (en) 2016-12-26 2021-12-14 Mitsubishi Electric Corporation Biological material measuring apparatus and method of measuring biological material
JP2019130283A (ja) * 2018-09-07 2019-08-08 三菱電機株式会社 生体物質測定装置
WO2020068256A1 (fr) * 2018-09-30 2020-04-02 Agilent Technologies, Inc. Système d'étalonnage de spectrométrie de réflexion totale atténuée
CN112771369A (zh) * 2018-09-30 2021-05-07 安捷伦科技有限公司 用于衰减全反射光谱的校准系统
US11060914B2 (en) 2018-09-30 2021-07-13 Agilent Technologies, Inc. Calibration system for attenuated total reflection spectrometry
JP2022503975A (ja) * 2018-09-30 2022-01-12 アジレント・テクノロジーズ・インク 減衰全反射分光測定のための較正システム
JP7407179B2 (ja) 2018-09-30 2023-12-28 アジレント・テクノロジーズ・インク 減衰全反射分光測定のための較正システム

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