WO2015156777A1 - Système de mesure optique ayant un élément de réflexion interne intégré et un détecteur de réseau - Google Patents

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

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WO2015156777A1
WO2015156777A1 PCT/US2014/033321 US2014033321W WO2015156777A1 WO 2015156777 A1 WO2015156777 A1 WO 2015156777A1 US 2014033321 W US2014033321 W US 2014033321W WO 2015156777 A1 WO2015156777 A1 WO 2015156777A1
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face
prism
detector
atr
reflectance
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PCT/US2014/033321
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Pandata Research Llc
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Priority to PCT/US2014/033321 priority Critical patent/WO2015156777A1/fr
Publication of WO2015156777A1 publication Critical patent/WO2015156777A1/fr

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    • 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
    • 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
    • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
    • A61B2562/04—Arrangements of multiple sensors of the same type
    • A61B2562/046—Arrangements of multiple sensors of the same type in a matrix array
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
    • A61B5/0075—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy
    • 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.
  • 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 among an ATR face of the prism (which engages the sample under
  • a detector face of the prism and a high-reflectance 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. 2 is a perspective drawing of the prism of FIG. 1 , with examples of additional system components.
  • FIG. 3 is a perspective drawing of the prism of FIGS. 1 and 2, further showing an example of an optical path of a beam propagating within the prism.
  • FIG. 4 is a flowchart of an example 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.
  • 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.
  • 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.
  • 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. 1-3 depict an example system from differing perspectives as identified earlier herein.
  • FIG. 1 is a front- view drawing of an example prism 100, which is in contact with a tissue sample 102.
  • FIG. 1 shows the example prism 100 in cross-section, where the prism 100 extends into and out of the plane of the page in FIG. 1, and has a generally uniform cross-section at each location along its length.
  • FIG. 2 is a perspective drawing of the prism 100 of FIG. 1, with additional system components.
  • FIG. 3 is a perspective drawing of the prism 100 of FIGS. 1 and 2, further showing the optical path of a beam propagating within the prism 100.
  • the prism has five sides, arranged as a pentagon.
  • a sample 102 is placed in contact with one of the five sides, which is referred to herein as an "ATR face" 104.
  • the two opposing faces 110, 112 directly adjacent to the ATR face 104 are angled at approximately ninety degrees to the ATR face 104, although they may be alternatively angled at less than or greater than ninety degrees.
  • the ATR face 104, the detector face 106, and the high-reflectance face 108 have surface normals denoted as SN104, SN106, and SNios, respectively.
  • the ATR face 104, the detector face 106, and the high- reflectance face 108 are angled so that an angle formed between SN106 and SN104 equals an angle formed between SNios and SN104.
  • the pentagonal cross-section is symmetrical around a centerline connecting the midpoint of the ATR face 104 and the intersection of the detector face 106 and the high-reflectance face 108.
  • 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 sa mpie / n P ri S m), where n sa mpie and n P ri S m 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 nsample*
  • 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.
  • an x, y, z coordinate system is established around the ATR face 104 of the prism 100, so that the ATR face 104 is within the x-z plane, and a longitudinal axis of the prism is parallel to the z-axis.
  • the ATR face 104 is parallel to the longitudinal (z) axis 16 of prism 100.
  • the high-reflectance face 108 of prism 100 will be coated with coating
  • 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-reflectance coating is made from a metal, such as gold.
  • the coating may be relatively thick, so that nearly all of the light is reflected, with minimal light being absorbed by the coating and minimal (if any) light being transmitted through the coating.
  • 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 source light beam will enter prism 100 though a selected region 222 of high-reflectance face 108.
  • this light-receiving region 222 for receiving the input light beam will be adapted to maximize transmission of the light, and thus will, in many cases, be uncoated.
  • an end face 228 of prism 100 may be configured to receive the input light beam from a source 232.
  • the high-reflection coating 108A on the high- reflectance face 108 does not extend fully to both longitudinal ends 218, 220, so that beams can be coupled into and out of the prism 100 at the uncoated portions.
  • the longitudinal end 220 of the high-reflectance face 108 opposite the end 218 proximate beam entrance region 222 may include an absorber, which can terminate the beam at the end of its longitudinal "walk” down the length of the prism 100 to minimize reflections back into prism 100.
  • 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 114 that, as noted earlier herein, will be secured in fixed relation to detector face 106.
  • the detector face 106 may also be parallel to the longitudinal (z) axis and will typically be angled with respect to both the ATR face 104 and the high-reflectance face 108.
  • 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 114 will be secured directly to the prism 100.
  • the prism 100 and array detector 114 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 114.
  • the array detector 114 will be not just secured proximate detector face 106, but will be optically bonded to detector face 106. In such configurations, a refractive-index-matching material may be used to minimize any variation of the refractive index between detector face 106 and array detector 114. In other examples, the array detector 114 may not be optically bonded to the detector face 106, and/or no such refractive- index- matching material will be used between the array detector 114 and the detector face 106 of the prism 100. In some examples, the array detector 114 can be fabricated directly onto the prism 100.
  • the array detector 114 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 114 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 array detector 114 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 114 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.
  • the cross-section of the prism 100 is the same at each location along the longitudinal (z) axis.
  • 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 surface normal SN1 0 4 of the ATR face 104, the surface normal SN1 06 of the detector face 106, and the surface normal SNios of the high-reflectance face 108 are all coplanar.
  • these three surface normals SN1 0 4, SN1 06 , and SNios are all oriented in the plane of the page of FIG. 1.
  • the geometry of the prism 100 itself appears straightforward, since the cross-section of the prism 100 is the same at each location along the longitudinal axis, the beam path inside the prism 100 is rather complicated. The beam path is more easily explained using the optical path (P) shown in FIGS. 2 and 3.
  • a light source 232 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 232 and mirrors 234, 236 may collectively be referred to as a beam emitter assembly 230.
  • the beam produced by the beam deflection assembly 230 has a variable orientation within a plane of incidence 224, and has variable insertion angle a, formed with respect to a surface normal 226 from the high-reflectance face 108.
  • the beam enter the prism 100 through roughly the same location on the high-reflectance face 108. It is possible, however, that some systems may be implemented such that the incident beam can "walk" to different locations on the high-reflective face 108 as the angle varies, as long as an edge of the high-reflective face 108 does not clip an edge of the beam. These locations may be disposed within light-receiving region 222 of the high-reflectance face 108, which is devoid of a high- reflectance coating.
  • FIG. 3 shows the optical path (P) of the beam within the prism 100.
  • the beam enters the prism at or near longitudinal end 218 of the prism 100, and propagates within the prism 100, through multiple reflections within the prism 100, toward longitudinal end 220 of the prism 100.
  • the internal beam advanced monotonically from one longitudinal end of the prism 228 to the other longitudinal end with each lateral reflection.
  • the optical path (P) within the prism is shown as a thick, dotted line.
  • the beam enters the prism 100 at a location 302 on the high-reflectance face 108 that is devoid of the high-reflectance coating.
  • the beam propagates to location 304 on the ATR face 104, then to location 306 on the detector face 106, then to location 308 on the ATR face 104, then to location 310 on the high- reflectance face 108, then to location 312 on the ATR face 104, then to location 314 on the detector face 106, then to location 316 on the ATR face 104, then to location 318 on the high-reflectance face 108, then to location 320 on the ATR face 104, then to location 322 on the detector face 106.
  • the optical path (P) may terminate at an absorber disposed at or near longitudinal end 220 of the prism 100.
  • Each reflection off the ATR face 104 such as at locations 304, 308, 312, 316, and 320, may produce useful signal for the detection path. Except for the first 306 and last reflections 322 off the detector face 106, there may be
  • FIG. 3 shows the plane of incidence 224 for the incident beam, with respect to the high-reflectance face 108.
  • the incident angle a of the beam is scanned over its angular range, it is intended that the beam enter the prism 100 through roughly the same location 302 on the high-reflectance face 108. It is also intended that beam remain roughly centered on the detector face 106 and the high-reflectance face 108 for subsequent reflections.
  • the internal beam may be generally centered if the incident beam is confined to lie in the incident plane 224 shown in FIGS. 2 and 3.
  • the incident plane 224 includes both the surface normal SNios to the high-reflectance face 108 and the longitudinal z-axis.
  • the plane that includes the incident beam and first leg of the internal beam is perpendicular to the high-reflectance face 108 and is perpendicular to the plane of the cross- section of FIG. 1.
  • the prism 100 should be configured so that the angle ⁇ is less than the particular desired angle.
  • the angle between a surface normal SNios of the high-reflectance face 108 and a surface normal SN104 of the ATR face 104 is equal to the angle between a surface normal SN1 06 of the detector face 106 and the surface normal SN1 0 4 of the ATR face 104, and both angles are denoted by the value ⁇ with a value typically less than a desired incident angle at the ATR face 104.
  • the desired incident angle at the ATR face 104 is the critical angle.
  • the angle ⁇ may be selected at the design phase of the prism 100 so that the actual incident angle on the ATR face 104 sweeps through a particular desired incident angle, such as the critical angle, for a range of incident angles a.
  • location 304 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 306 on the detector.
  • the intensity at location 306 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 302 can also be used for calibrating a system that uses the prism 100.
  • FIG. 4 is a flow chart of an example method 400 for performing the reflectivity measurement.
  • the example method 400 begins at 402 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 230.
  • the beam emitter assembly 230 generates the beam at the particular wavelength and angular orientation as selected at 404.
  • the beam produced at 406 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 414.
  • each bright spot can be curve-fit to a known beam profile that is emitted by the beam emitter assembly 230.
  • 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 beam emitter assembly 230 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).
  • the desired location may remain the same for all or some of the incident angles, and is typically within an uncoated region 222 near a first longitudinal end of the high- reflectance face 108.
  • a suitable light source 232 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.
  • 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.
  • Snell' s Law applied at location 302 in FIG. 3, determines a propagation direction inside the prism, based on the prism geometry and the prism refractive index. There is an upper limit of the angle of incidence that can be achieved at the ATR face 104, which is determined by the refractive index of the prism and the geometry of the prism. In general, during a design phase of the prism, the prism material is selected so that a desired angle of incidence can be achieved at locations 304, 308, 312, 316, and 320, in FIG. 3.

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  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

Un prisme est conçu pour recevoir un faisceau aligné et propager un faisceau interne qui suit un trajet ayant de multiples réflexions à l'intérieur du prisme. Les multiples réflexions se produisent parmi une face de Réflexion Totale Atténuée (ATR), une face de détecteur, et une face de réflectance élevée du prisme. Un angle entre une normale de surface de la face à forte réflectance et une normale de surface de la face ATR est égal à un angle entre une normale de surface de la face de détecteur et la normale de surface de la face ATR. Les normales de surface de la face ATR, la face de détecteur, et la face à forte réflectance sont toutes coplanaires. Un détecteur de réseau est monté de manière fixe sur le prisme à proximité de la face du détecteur afin de détecter une position interne du faisceau interne et une intensité du faisceau interne pour chaque réflexion du faisceau interne hors de la face du détecteur.
PCT/US2014/033321 2014-04-08 2014-04-08 Système de mesure optique ayant un élément de réflexion interne intégré et un détecteur de réseau WO2015156777A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017207282A1 (fr) * 2016-05-30 2017-12-07 Siemens Aktiengesellschaft Dispositif pour réaliser la spectroscopie d'un échantillon en réflexion totale atténuée

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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
US20110310394A1 (en) * 2010-06-22 2011-12-22 Chian Chiu Li Compact Surface Plasmon Resonance Apparatus And Method
US20120088486A1 (en) 2009-04-07 2012-04-12 Messerchmidt Robert G Peri-critical reflection spectroscopy devices, systems, and methods

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
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
US20120088486A1 (en) 2009-04-07 2012-04-12 Messerchmidt Robert G Peri-critical reflection spectroscopy devices, systems, and methods
US20110310394A1 (en) * 2010-06-22 2011-12-22 Chian Chiu Li Compact Surface Plasmon Resonance Apparatus And Method

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017207282A1 (fr) * 2016-05-30 2017-12-07 Siemens Aktiengesellschaft Dispositif pour réaliser la spectroscopie d'un échantillon en réflexion totale atténuée

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