WO1997013448A2 - Device for determining blood glucose level - Google Patents

Device for determining blood glucose level Download PDF

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Publication number
WO1997013448A2
WO1997013448A2 PCT/DE1996/001971 DE9601971W WO9713448A2 WO 1997013448 A2 WO1997013448 A2 WO 1997013448A2 DE 9601971 W DE9601971 W DE 9601971W WO 9713448 A2 WO9713448 A2 WO 9713448A2
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WO
WIPO (PCT)
Prior art keywords
eye
radiation
measuring radiation
concentration
light source
Prior art date
Application number
PCT/DE1996/001971
Other languages
German (de)
French (fr)
Other versions
WO1997013448A3 (en
Inventor
Gerhard Müller
Original Assignee
Laser- Und Medizin-Technologie Gmbh Berlin
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Publication date
Application filed by Laser- Und Medizin-Technologie Gmbh Berlin filed Critical Laser- Und Medizin-Technologie Gmbh Berlin
Priority to DE29623431U priority Critical patent/DE29623431U1/en
Publication of WO1997013448A2 publication Critical patent/WO1997013448A2/en
Publication of WO1997013448A3 publication Critical patent/WO1997013448A3/en

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Classifications

    • 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
    • A61B5/14558—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 by polarisation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B3/00—Apparatus for testing the eyes; Instruments for examining the eyes
    • A61B3/10—Objective types, i.e. instruments for examining the eyes independent of the patients' perceptions or reactions
    • A61B3/14—Arrangements specially adapted for eye photography
    • A61B3/15—Arrangements specially adapted for eye photography with means for aligning, spacing or blocking spurious reflection ; with means for relaxing
    • 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 invention relates to a device for the non-invasive determination of the concentration of a blood component, in particular for the determination of blood glucose, according to the preamble of claim 1.
  • Devices for determining the blood glucose concentration are known which are based on the influence of the blood glucose concentration on the absorption properties of the human body tissue.
  • the known devices therefore have a light source which shines transcutaneously through a part of the body of the person to be examined, for example the earlobe, the fingertip or the inner lip, at glucose-specific wavelengths in the near infrared or medium infrared, the measuring radiation depending on the blood glucose concentration is weakened.
  • a light detector is therefore arranged on the opposite side of the irradiated body part, which detects the transmitted measuring radiation and feeds a corresponding signal to an evaluation unit which uses it to calculate the blood glucose concentration.
  • the problem here is that the blood glucose-specific signal is extremely small compared to underground signals due to water and tissue absorption.
  • the high value of the water absorption changes depending on the temperature, so that practically no meaningful measurement signal can be obtained.
  • Another disadvantage of these devices is that both the so-called tissue glucose concentration and the blood glucose concentration are measured simultaneously and there is practically no possibility of differentiating the two signals. Beyond that Such measurements are falsified in that the light propagation in the tissue is not adequately taken into account as a multiple scattering process.
  • devices for determining blood glucose which are based on the determination of the optical activity, that is to say the change in the direction of polarization by the right-handed glucose, of the irradiated tissue.
  • These devices also have the disadvantage that the propagation of light in the tissue is not adequately taken into account.
  • the optical activity of the irradiated tissue depends not only on the blood glucose concentration, but is also influenced by the concentration of other optically active blood or tissue components.
  • a further disadvantage of these devices is the extreme dependence of the measurement result on the irradiated layer thickness, which must therefore also be determined, which is not possible or is only possible with increased technical effort.
  • the invention is therefore based on the object of creating a device for non-invasive blood glucose determination which enables simple and accurate measurement of the blood glucose concentration and avoids the above-mentioned disadvantages of the known devices.
  • the invention includes the technical teaching of introducing measuring radiation into the anterior chamber of an eye of the test person by means of a light source in order to determine the concentration of a blood component and the intensity of the reflected or backscattered measurement radiation to be detected by a light detector in order to determine the blood concentration of the respective blood component from the concentration-dependent intensity of the reflected or backscattered measurement radiation.
  • this is based on the new and surprising finding that the fluid in the anterior chamber of the human eye is to be regarded as the ultrafiltrate of the blood plasma and therefore has a strict correlation with a glucose content which corresponds to that of the blood plasma.
  • the invention is not limited to determining the blood glucose concentration, but rather can be used to measure the concentration of all blood components in which the concentration in the eye fluid has a predetermined dependence on the blood concentration.
  • the invention is also not limited to humans as a measurement object, but can also be used with animals.
  • a measurement light to be introduced into the anterior chamber by means of a first light source, the wavelength of the measurement radiation for exciting glucose-specific Raman bands preferably being in the near infrared range.
  • emission wavelengths in the range from 650 nm to 2.5 ⁇ m have proven to be advantageous.
  • a light detector is provided, which is arranged in front of the irradiated eye for measuring the measurement radiation reflected or backscattered in the eye fluid.
  • the concentration of the respective blood component is then determined by an evaluation unit which is connected on the input side to the light detector.
  • the evaluation unit preferably subjects the reflected or backscattered measurement radiation to Fourier transform infrared Raman spectroscopy in order to be able to subsequently calculate the blood concentration sought from the spectral intensity distribution.
  • focusing optics are provided which focus the measuring radiation generated by the first light source in the anterior chamber in such a way that the measuring radiation essentially hits the iris diaphragm on the retina side, thereby preventing damage to the retina even at high intensities of the measuring radiation .
  • This focusing optics preferably has a high-aperture, short focal length dark field objective, as is known, for example, from light microscopy.
  • the dark field lens is arranged in front of the subject's eye, the excitation radiation being focused radially symmetrically into the anterior chamber of the eye.
  • the light-filled double cone is focused in such a way that it is already so divergent in the retinal focus area that it does not fall through the pupil onto the retina, but is stopped by the iris diaphragm.
  • a wavelength in the range of strong absorption of water to prevent retina damage by the measuring radiation.
  • This is for protection No separate optics are required for the retina before the measuring radiation, since the measuring radiation is sufficiently attenuated until the retina is reached due to absorption by the eye fluid in order to prevent damage to the retina. Wavelengths above 1.5 ⁇ m have proven to be advantageous.
  • the detection of the reflected or backscattered measurement radiation is then carried out - as already described above - by a light detector and a downstream evaluation unit, preferably using the technologies of the so-called Fourier transform infrared Raman spectroscopy.
  • a further variant of the invention provides for the examined eye to be fixed during the measurement. This is particularly advantageous if, as already described above, a focus is used to prevent the retina from being damaged by the measuring radiation ⁇ rungsoptik is provided, which generates a strongly divergent beam on the retina side, since the effectiveness of such focusing optics is only fully available with a certain spatial position of the eye and decreases when the viewing direction changes.
  • the eye is fixed in that a fixation mark is faded into the field of vision, which is fixed by the test subject and causes the eyes to be immobilized in a defined position.
  • the fixation mark is generated by a second light source with an emission wavelength in the visible wavelength range, the light exit opening of which is arranged spatially fixed in the field of view of the subject.
  • An optical waveguide, one end of which is connected to the second light source, is particularly advantageous for this purpose, while the light outlet opening is arranged in the field of view of the examined eye.
  • an optical filter is provided between the light detector and the examined eye in the beam path of the reflected measuring radiation, which suppresses light in those wavelength ranges in which the intensity of the backscattered or reflected measuring radiation is only slight Depends on the concentration of the blood component to be determined.
  • the proportion of measuring radiation that reaches the light detector has a significantly greater dependence on the concentration to be determined, which simplifies the measurement and increases the accuracy.
  • FIG. 1 shows, as a preferred embodiment of the invention, a device for determining the blood glucose concentration with an illustration of the beam paths
  • Figure 2 shows the arrangement of the device of Figure 1 during the measurement
  • Figure 3 shows an alternative embodiment of the device according to the invention.
  • the device shown in Figure 1 enables a non-invasive determination of the blood glucose concentration by Introducing measuring radiation into the front chamber 1 of an eye 2 and measuring the backscattered or reflected portion.
  • the measuring radiation is generated by a light source 3 and brought to the required beam cross-section by an expansion optics 4.
  • the measuring radiation is then directed with a ring-shaped mirror 5 onto a dark field illumination objective 6, which focuses the measuring radiation in the front chamber 1 of the eye 2 in such a way that after passing through the focal point it falls on the iris diaphragm 7 and thus the sensitive retina behind the Eye lens 8 not at risk.
  • the differently strong Raman radiation which arises in the front chamber 1, depending on the glucose concentration, is bundled by the high-aperture lens 9 and, before it reaches the light detector 10, sent through a filter 11 which suppresses the interfering radiation components.
  • the evaluation unit 12 which first subjects the output signal of the light detector 10 to Fourier transform infrared Raman spectroscopy and calculates the blood glucose concentration from the spectral intensity distribution using a computing unit.
  • the device shown enables the eye 2 to be fixed and the iris 7 to be narrowed in order to prevent damage to the sensitive retina by the measurement radiation.
  • a fixation mark is faded into the field of vision, which is fixed by the test subject, which on the one hand leads to a fixation of the eye 2 and, on the other hand, to a narrowing of the iris diaphragm 7 due to the brightness of the fixation mark, since the eye 2 independently adjusts to the lighting conditions adjusts.
  • the fixing mark is generated by a second light source designed as a fixing mark projector and is faded into the field of view via a light waveguide 13.
  • the light exit opening of the optical waveguide 13 is arranged in front of the high-aperture lens 9 in such a way that the fixation mark only fully reaches the retina when the eye 2 is in the most favorable measuring position.
  • FIG. 2 shows, on the one hand, the arrangement of the device shown only schematically above in a binocular viewing device 14 and, on the other hand, the use of the binocular viewing device 14 by the person 15 to be examined.
  • the device described above is arranged in the tube 16.1 of the binocular viewing device 14, which is placed on the right eye of the subject 15 with an eyepiece 17.1.
  • the other tube 16.2 contains a display 18 which is arranged at the transition point to the associated eyepiece 17.2.
  • This display 18 is controlled by the evaluation unit and shows the measured blood glucose concentration, so that the person 15 to be examined only has to look into the binocular vision device 14 and the blood glucose concentration is immediately displayed.
  • the device according to the invention is thus easy to handle that a diabetic can determine the blood glucose value in a self-test.
  • FIG. 3 finally shows an alternative embodiment of the device according to the invention for determining the blood glucose concentration, measuring radiation being introduced into the front chamber 1 of an eye 2 as in the exemplary embodiment shown in FIG. 1, and the proportion of the reflected or backscattered measuring radiation is measured.
  • the measuring radiation is generated here by a light source 19, the emission wavelength of which is above 1.5 ⁇ m, so that the measuring radiation is strongly absorbed by the eye fluid, which essentially consists of water.
  • a light source 19 the emission wavelength of which is above 1.5 ⁇ m, so that the measuring radiation is strongly absorbed by the eye fluid, which essentially consists of water.
  • This advantageously prevents damage to the sensitive retina from the measuring radiation, since the measuring radiation is sufficiently attenuated after it has passed through the interior of the eye until the eye fluid reaches the retina to prevent damage to the retina.
  • the embodiment shown therefore does not require separate focusing optics in order to prevent direct exposure of the retina.
  • the measuring radiation generated by the light source 19 is faded into the field of view of the eye 2 via the colimation lens 20 and the partially transparent mirror 21 and is focused by the focusing lens 22 in the front chamber 1 of the eye 2.
  • the Raman radiation which is dependent on the glucose concentration, is collected by the high-aperture focusing lens 22 and penetrates the partially transparent mirror 21, which has a high degree of transparency for the spectral intensity distribution of the Raman radiation. Then reached the reflected measuring radiation the light detector 23, which is connected on the output side to the evaluation unit 24.
  • the measurement radiation is first subjected to a Fourier transform Raman spectroscopy by the evaluation unit 24, in order then to be able to calculate the blood glucose concentration as a function of the determined spectrum of the Raman radiation.
  • the embodiment of the invention is not limited to the preferred exemplary embodiments specified above. Rather, a number of variants are conceivable which make use of the solution shown, even in the case of fundamentally different types.

Abstract

The proposed device for determining blood glucose level comprises the following elements: a light source (3) for producing a measurement radiation used to illuminate a part (2) of the body using a wavelength for which the optical properties of the body part (2) depend on the concentration of the blood component in question; a light detector (10) for detecting the measurement radiation which has been attenuated in the body part (2) to a degree dependent on the said concentration; and an evaluation unit (12) for determining the concentration of the blood component as a function of the radiation detected. The illuminated body part is an eye (2) and the light detector (10) for measuring the reflected light is set up in the path of the radiation reflected or back scattered in the anterior chamber (1) of the eye. A focusing system (6) is mounted between the light source (3) and the illuminated eye (2) to prevent damage to the retina by the measurement radiation. The focusing system focuses the measurement radiation in the anterior chamber (1) of the eye in such a way that the radiation nearer to the retina is substantially blocked by the iris (7), and/or the selected wavelength of the measurement radiation lies within the absorption range of the aqueous humour in order to prevent damage to the retina.

Description

Vorrichtung zur Blutglukosebestimmung Device for determining blood glucose
Beschreibungdescription
Die Erfindung betrifft eine Vorrichtung zur nichtinvasiven Bestimmung der Konzentration eines Blutbestandteils, insbe¬ sondere zur Blutglukosebestimmung, gemäß dem Oberbegriff des Anspruchs 1.The invention relates to a device for the non-invasive determination of the concentration of a blood component, in particular for the determination of blood glucose, according to the preamble of claim 1.
Es sind Vorrichtungen zur Bestimmung der Blutglukosekonzen¬ tration bekannt, die auf dem Einfluß der Blutglukosekonzen¬ tration auf die Absorptionseigenschaften des menschlichen Körpergewebes beruhen. Die bekannten Vorrichtungen weisen deshalb eine Lichtquelle auf, die einen Körperteil der zu untersuchenden Person, beispielsweise das Ohrläppchen, die Fingerbeere oder die Innenlippe, transkutan bei glukosespe¬ zifischen Wellenlängen im Nahinfraroten oder mittleren In¬ fraroten durchstrahlt, wobei die Meßstrahlung in Abhängig¬ keit von der Blutglukosekonzentration abgeschwächt wird. Auf der gegenüberliegenden Seite des durchstrahlten Körper¬ teils ist deshalb ein Lichtdetektor angeordnet, der die durchgelassene Meßstrahlung erfaßt und ein entsprechendes Signal einer Auswertungseinheit zuführt, die daraus die Blutglukosekonzentration berechnet.Devices for determining the blood glucose concentration are known which are based on the influence of the blood glucose concentration on the absorption properties of the human body tissue. The known devices therefore have a light source which shines transcutaneously through a part of the body of the person to be examined, for example the earlobe, the fingertip or the inner lip, at glucose-specific wavelengths in the near infrared or medium infrared, the measuring radiation depending on the blood glucose concentration is weakened. A light detector is therefore arranged on the opposite side of the irradiated body part, which detects the transmitted measuring radiation and feeds a corresponding signal to an evaluation unit which uses it to calculate the blood glucose concentration.
Problematisch ist hierbei jedoch, daß das blutglukosespezi- fische Signal außerordentlich klein gegenüber Untergrundsi¬ gnalen durch Wasser- und Gewebeabsorption ist. Insbesondere ändert sich der hohe Wert der Wasserabsorption temperatur¬ abhängig, so daß praktisch kein aussagefähiges Meßsignal gewonnen werden kann. Ein weiterer Nachteil dieser Vorrich¬ tungen ist darin zu sehen, daß gleichzeitig sowohl die so¬ genannte Gewebsglukose- als auch die Blutglukosekonzentra¬ tion gemessen wird und praktisch keine Möglichkeit zur Dif¬ ferenzierung beider Signale besteht. Darüber hinaus sind derartige Messungen dadurch verfälscht, daß die Lichtaus¬ breitung im Gewebe als Vielfachstreuprozeß nicht adäquat berücksichtigt wird.However, the problem here is that the blood glucose-specific signal is extremely small compared to underground signals due to water and tissue absorption. In particular, the high value of the water absorption changes depending on the temperature, so that practically no meaningful measurement signal can be obtained. Another disadvantage of these devices is that both the so-called tissue glucose concentration and the blood glucose concentration are measured simultaneously and there is practically no possibility of differentiating the two signals. Beyond that Such measurements are falsified in that the light propagation in the tissue is not adequately taken into account as a multiple scattering process.
Weiterhin sind Vorrichtungen zur Blutglukosebestimmung be- kannt, die auf der Ermittlung der optischen Aktivität, also der Änderung der Polarisationsrichtung durch die rechtsdre¬ hende Glukose, des durchstrahlten Gewebes beruhen. Auch diese Vorrichtungen haben den Nachteil, daß die Lichtaus¬ breitung im Gewebe nicht in angemessener Weise berücksich- tigt wird. Darüber hinaus hängt die optische Aktivität des durchstrahlten Gewebes nicht nur von der Blutglukosekonzen¬ tration ab, sondern wird auch durch die Konzentration ande¬ rer optisch aktiver Blut- oder Gewebebestandteile beein¬ flußt. Ein weiterer Nachteil dieser Vorrichtungen besteht in der extremen Abhängigkeit des Meßergebnisses von der durchstrahlten Schichtdicke, die somit zusätzlich zu ermit¬ teln ist, was nicht oder nur mit einem erhöhten technischen Aufwand möglich ist.Furthermore, devices for determining blood glucose are known which are based on the determination of the optical activity, that is to say the change in the direction of polarization by the right-handed glucose, of the irradiated tissue. These devices also have the disadvantage that the propagation of light in the tissue is not adequately taken into account. In addition, the optical activity of the irradiated tissue depends not only on the blood glucose concentration, but is also influenced by the concentration of other optically active blood or tissue components. A further disadvantage of these devices is the extreme dependence of the measurement result on the irradiated layer thickness, which must therefore also be determined, which is not possible or is only possible with increased technical effort.
Der Erfindung liegt somit die Aufgabe zugrunde, eine Vor- richtung zur nichtinvasiven Blutglukosebestimmung zu schaf¬ fen, die eine einfache und genaue Messung der Blutglukose¬ konzentration ermöglicht und die vorstehend genannten Nach¬ teile der bekannten Vorrichtungen vermeidet.The invention is therefore based on the object of creating a device for non-invasive blood glucose determination which enables simple and accurate measurement of the blood glucose concentration and avoids the above-mentioned disadvantages of the known devices.
Die Aufgabe wird, ausgehend von einer Vorrichtung gemäß dem Oberbegriff des Anspruchs 1, durch die kennzeichnenden Merkmale des Anspruchs 1 gelöst.Starting from a device according to the preamble of claim 1, the object is achieved by the characterizing features of claim 1.
Die Erfindung schließt die technische Lehre ein, zur Be¬ stimmung der Konzentration eines Blutbestandteils mittels einer Lichtquelle Meßstrahlung in die Augenvorderkammer ei- nes Auges des Probanden einzuleiten und die Intensität der reflektierten bzw. rückgestreuten Meßstrahlung durch einen Lichtdetektor zu erfassen, um aus der konzentrationsabhän¬ gigen Intensität der reflektierten bzw. rückgestreuten Me߬ strahlung die Blutkonzentration des jeweiligen Blutbestand- teils zu ermitteln.The invention includes the technical teaching of introducing measuring radiation into the anterior chamber of an eye of the test person by means of a light source in order to determine the concentration of a blood component and the intensity of the reflected or backscattered measurement radiation to be detected by a light detector in order to determine the blood concentration of the respective blood component from the concentration-dependent intensity of the reflected or backscattered measurement radiation.
Hierbei wird erfindungsgemäß von der neuen und überraschen¬ den Erkenntnis ausgegangen, daß die Flüssigkeit der Vorder¬ kammer des menschlichen Auges als Ultrafiltrat des Blut¬ plasmas zu betrachten ist und daher in strenger Korrelation einen Glukosegehalt aufweist, der dem des Blutplasmas ent¬ spricht.According to the invention, this is based on the new and surprising finding that the fluid in the anterior chamber of the human eye is to be regarded as the ultrafiltrate of the blood plasma and therefore has a strict correlation with a glucose content which corresponds to that of the blood plasma.
Die Erfindung ist jedoch nicht auf die Bestimmung der Blut¬ glukosekonzentration beschränkt, sondern läßt sich vielmehr zur Messung der Konzentration aller Blutbestandteile ver- wenden, bei denen die Konzentration in der Augenflüssigkeit eine vorgegebene Abhängigkeit von der Blutkonzentration aufweist. Auch ist die Erfindung nicht auf Menschen als Meßobjekt beschränkt, sondern auch mit Tieren anwendbar.However, the invention is not limited to determining the blood glucose concentration, but rather can be used to measure the concentration of all blood components in which the concentration in the eye fluid has a predetermined dependence on the blood concentration. The invention is also not limited to humans as a measurement object, but can also be used with animals.
Gemäß der Erfindung ist deshalb vorgesehen, mittels einer ersten Lichtquelle Meßstrahlung in die Augenvorderkammer einzuleiten, wobei die Wellenlänge der Meßstrahlung zur An¬ regung von glukosespezifischen Ramanbanden vorzugsweise im Nahinfrarotbereich liegt. Als vorteilhaft haben sich hier¬ bei Emissionswellenlängen im Bereich 650 nm...2,5 μm erwie- sen.According to the invention, provision is therefore made for a measurement light to be introduced into the anterior chamber by means of a first light source, the wavelength of the measurement radiation for exciting glucose-specific Raman bands preferably being in the near infrared range. In this case, emission wavelengths in the range from 650 nm to 2.5 μm have proven to be advantageous.
Weiterhin ist gemäß der Erfindung ein Lichtdetektor vorge¬ sehen, der zur Messung der in der Augenflüssigkeit reflek¬ tierten bzw. zurückgestreuten Meßstrahlung vor dem be¬ strahlten Auge angeordnet ist. Die Ermittlung der Konzen- tration des jeweiligen Blutbestandteils erfolgt dann durch eine Auswertungseinheit, die eingangsseitig mit dem Licht¬ detektor verbunden ist. Vorzugsweise unterzieht die Auswer¬ tungseinheit die reflektierte bzw. rückgestreute Meßstrah¬ lung einer Fourier-Transform-Infrarot-Raman-Spektroskopie, um anschließend aus der spektralen Intensitätsverteilung die gesuchte Blutkonzentration berechnen zu können.Furthermore, according to the invention, a light detector is provided, which is arranged in front of the irradiated eye for measuring the measurement radiation reflected or backscattered in the eye fluid. The concentration of the respective blood component is then determined by an evaluation unit which is connected on the input side to the light detector. The evaluation unit preferably subjects the reflected or backscattered measurement radiation to Fourier transform infrared Raman spectroscopy in order to be able to subsequently calculate the blood concentration sought from the spectral intensity distribution.
In einer Variante der Erfindung ist darüber hinaus vorgese¬ hen, eine Retinaschadigung durch die Meßstrahlung zu ver¬ hindern, indem eine direkte Belichtung der Retina durch die Meßstrahlung weitgehend verhindert wird. Hierzu ist eine Fokussierungsoptik vorgesehen, welche die von der ersten Lichtquelle erzeugte Meßstrahlung derart in der Augenvor¬ derkammer fokussiert, daß die Meßstrahlung retinaseitig im wesentlichen auf die Irisblende trifft, wodurch eine Schä- digung der Retina auch bei hohen Intensitäten der Meßstrah¬ lung verhindert wird.In a variant of the invention, provision is also made to prevent damage to the retina by the measuring radiation by largely preventing direct exposure of the retina to the measuring radiation. For this purpose, focusing optics are provided which focus the measuring radiation generated by the first light source in the anterior chamber in such a way that the measuring radiation essentially hits the iris diaphragm on the retina side, thereby preventing damage to the retina even at high intensities of the measuring radiation .
Vorzugsweise weist diese Fokussierungsoptik ein hochapertu- riges, kurzbrennweitiges Dunkelfeldobjektiv auf, wie es beispielsweise aus der Lichtmikroskopie bekannt ist. Das Dunkelfeldobjektiv ist hierbei vor dem Auge des Probanden angeordnet, wobei die Erregerstrahlung radial symmetrisch in die Augenvorderkammer fokussiert wird. Dabei wird der lichterfüllte Doppelkonus derart fokussiert, daß er im re- tinaseitigen Fokusbereich bereits wieder soweit divergent ist, daß er nicht durch die Pupille auf die Retina fällt, sondern von der Irisblende aufgehalten wird.This focusing optics preferably has a high-aperture, short focal length dark field objective, as is known, for example, from light microscopy. The dark field lens is arranged in front of the subject's eye, the excitation radiation being focused radially symmetrically into the anterior chamber of the eye. The light-filled double cone is focused in such a way that it is already so divergent in the retinal focus area that it does not fall through the pupil onto the retina, but is stopped by the iris diaphragm.
In einer anderen Variante der Erfindung ist dagegen vorge¬ sehen, zur Verhinderung einer Retinaschadigung durch die Meßstrahlung eine Wellenlänge zu verwenden, die im Bereich starker Absorption von Wasser liegt. Hierbei ist zum Schutz der Retina vor der Meßstrahlung keine separate Optik erfor¬ derlich, da die Meßstrahlung bis zum Erreichen der Retina aufgrund der Absorption durch die Augenflüssigkeit hinrei¬ chend stark abgeschwächt ist, um eine Retinaschadigung aus- zuschließen. Als vorteilhaft haben sich hierbei Wellenlän¬ gen oberhalb von 1,5 um erwiesen. Die Erfassung der reflek¬ tierten bzw. zurückgestreuten Meßstrahlung erfolgt dann - wie bereits vorstehend beschrieben - durch einen Lichtde¬ tektor und eine nachgeschaltete Auswertungseinheit, vor- zugsweise unter Ausnutzung der Technologien der sogenannten Fourier-Transform-Infrarot-Raman-Spektroskopie.In another variant of the invention, on the other hand, provision is made to use a wavelength in the range of strong absorption of water to prevent retina damage by the measuring radiation. This is for protection No separate optics are required for the retina before the measuring radiation, since the measuring radiation is sufficiently attenuated until the retina is reached due to absorption by the eye fluid in order to prevent damage to the retina. Wavelengths above 1.5 μm have proven to be advantageous. The detection of the reflected or backscattered measurement radiation is then carried out - as already described above - by a light detector and a downstream evaluation unit, preferably using the technologies of the so-called Fourier transform infrared Raman spectroscopy.
In einer weiterbildenden Variante der Erfindung ist vorge¬ sehen, das untersuchte Auge während der Messung zu fixie¬ ren. Dies ist insbesondere dann vorteilhaft, wenn - wie be- reits vorstehend beschrieben - zur Verhinderung einer Schä¬ digung der Retina durch die Meßstrahlung eine Fokussie¬ rungsoptik vorgesehen ist, die retinaseitig ein stark di¬ vergentes Strahlenbündel erzeugt, da die Wirksamkeit einer derartigen Fokussierungsoptik nur bei einer bestimmten räumlichen Lage des Auges in vollem Umfang gegeben ist und bei einer Änderung der Blickrichtung abnimmt. Die Fixierung des Auges erfolgt in dieser Variante der Erfindung, indem eine Fixiermarke in das Sichtfeld eingeblendet wird, die von dem Probanden fixiert wird und eine Ruhigstellung der Augen in einer definierten Lage bewirkt. Die Fixiermarke wird durch eine zweite Lichtquelle mit einer im sichtbaren Wellenlängenbereich liegenden Emissionswellenlänge erzeugt, deren Lichtaustrittsöffnung räumlich fixiert im Sichtfeld des Probanden angeordnet ist. Besonders vorteilhaft eignet sich hierfür ein Lichtwellenleiter, dessen eines Ende mit der zweiten Lichtquelle verbunden ist, während die Licht- austrittsöffnung im Sichtfeld des untersuchten Auges ange¬ ordnet ist.A further variant of the invention provides for the examined eye to be fixed during the measurement. This is particularly advantageous if, as already described above, a focus is used to prevent the retina from being damaged by the measuring radiation ¬ rungsoptik is provided, which generates a strongly divergent beam on the retina side, since the effectiveness of such focusing optics is only fully available with a certain spatial position of the eye and decreases when the viewing direction changes. In this variant of the invention, the eye is fixed in that a fixation mark is faded into the field of vision, which is fixed by the test subject and causes the eyes to be immobilized in a defined position. The fixation mark is generated by a second light source with an emission wavelength in the visible wavelength range, the light exit opening of which is arranged spatially fixed in the field of view of the subject. An optical waveguide, one end of which is connected to the second light source, is particularly advantageous for this purpose, while the light outlet opening is arranged in the field of view of the examined eye.
In einer weiteren Variante der Erfindung ist vorgesehen, zwischen dem Lichtdetektor und dem untersuchten Auge im Strahlengang der reflektierten Meßstrahlung ein optisches Filter anzuordnen, das Licht in solchen Wellenlängenberei¬ chen unterdrückt, in denen die Intensität der rückgestreu¬ ten bzw. reflektierten Meßstrahlung nur eine geringe Abhän¬ gigkeit von der Konzentration des zu bestimmenden Blutbe- Standteils aufweist. Hierdurch weist der Anteil der Me߬ strahlung, der den Lichtdetektor erreicht, eine wesentlich größere Abhängigkeit von der zu bestimmenden Konzentration auf, wodurch die Messung vereinfacht und die Genauigkeit gesteigert wird.In a further variant of the invention, an optical filter is provided between the light detector and the examined eye in the beam path of the reflected measuring radiation, which suppresses light in those wavelength ranges in which the intensity of the backscattered or reflected measuring radiation is only slight Depends on the concentration of the blood component to be determined. As a result, the proportion of measuring radiation that reaches the light detector has a significantly greater dependence on the concentration to be determined, which simplifies the measurement and increases the accuracy.
Andere vorteilhafte Weiterbildungen der Erfindung sind in den Unteransprüchen gekennzeichnet bzw. werden nachstehend zusammen mit der Beschreibung der bevorzugten Ausführung der Erfindung anhand der Figuren näher dargestellt. Es zei¬ gen:Other advantageous developments of the invention are characterized in the subclaims or are shown below together with the description of the preferred embodiment of the invention with reference to the figures. It shows:
Figur 1 als bevorzugtes Ausführungsbeispiel der Erfindung eine Vorrichtung zur Bestimmung der Blutglukosekon¬ zentration mit einer Darstellung der Strahlengänge,FIG. 1 shows, as a preferred embodiment of the invention, a device for determining the blood glucose concentration with an illustration of the beam paths,
Figur 2 die Anordnung der Vorrichtung aus Figur 1 während der Messung sowieFigure 2 shows the arrangement of the device of Figure 1 during the measurement and
Figur 3 eine alternative Ausführungsform der erfindungsge¬ mäßen Vorrichtung.Figure 3 shows an alternative embodiment of the device according to the invention.
Die in Figur 1 dargestellte Vorrichtung ermöglicht eine nichtinvasive Bestimmung der Blutglukosekonzentration durch Einleitung von Meßstrahlung in die Vorderkammer 1 eines Au¬ ges 2 und Messung des rückgestreuten bzw. reflektierten An¬ teils.The device shown in Figure 1 enables a non-invasive determination of the blood glucose concentration by Introducing measuring radiation into the front chamber 1 of an eye 2 and measuring the backscattered or reflected portion.
Hierbei wird von der Erkenntnis ausgegangen, daß die Gluko- sekonzentration in der Vorderkammer 1 der Augen 2 die Glu¬ kosekonzentration im Blut sehr genau widerspiegelt, so daß es zur Bestimmung der Blutglukosekonzentration ausreicht, die Glukosekonzentration in einer Augenvorderkammer 1 zu messen und daraus die Blutglukosekonzentration zu berech- nen.This is based on the knowledge that the glucose concentration in the anterior chamber 1 of the eyes 2 reflects the glucose concentration in the blood very precisely, so that it is sufficient to determine the blood glucose concentration by measuring the glucose concentration in an anterior chamber 1 and from this the blood glucose concentration to calculate.
Die Meßstrahlung wird hierbei von einer Lichtquelle 3 er¬ zeugt und durch eine Aufweitungsoptik 4 auf den erforderli¬ chen Strahlquerschnitt gebracht. Anschließend wird die Me߬ strahlung mit einem ringförmigen Spiegel 5 auf ein Dunkel- feldbeleuchtungsobjektiv 6 gelenkt, das die Meßstrahlung in der Vorderkammer 1 des Auges 2 so fokussiert, daß sie nach Durchlaufen des Brennpunkts auf die Irisblende 7 fällt und somit die empfindliche Retina hinter der Augenlinse 8 nicht gefährdet. Die je nach Glukosekonzentration in der Vorder- kammer 1 entstehende unterschiedlich starke Ramanstrahlung wird durch die hochaperturige Linse 9 gebündelt und, bevor sie den Lichtdetektor 10 erreicht, durch ein Filter 11 ge¬ schickt, welches die störenden Strahlungsanteile unter¬ drückt.The measuring radiation is generated by a light source 3 and brought to the required beam cross-section by an expansion optics 4. The measuring radiation is then directed with a ring-shaped mirror 5 onto a dark field illumination objective 6, which focuses the measuring radiation in the front chamber 1 of the eye 2 in such a way that after passing through the focal point it falls on the iris diaphragm 7 and thus the sensitive retina behind the Eye lens 8 not at risk. The differently strong Raman radiation which arises in the front chamber 1, depending on the glucose concentration, is bundled by the high-aperture lens 9 and, before it reaches the light detector 10, sent through a filter 11 which suppresses the interfering radiation components.
Die eigentliche Berechnung der Blutglukosekonzentration er¬ folgt dann durch die Auswertungseinheit 12, die das Aus¬ gangssignal des Lichtdetektors 10 zunächst einer Fourier- Transform-Infrarot-Raman-Spektroskopie unterzieht und aus der spektralen Intensitätsverteilung mittels einer Rechen- einheit die Blutglukosekonzentration errechnet. Darüber hinaus ermöglicht die dargestellte Vorrichtung eine Fixierung des Auges 2 sowie eine Engstellung der Iris 7, um eine Schädigung der empfindlichen Retina durch die Me߬ strahlung zu verhindern. Hierzu wird eine Fixiermarke in das Sichtfeld eingeblendet, die von dem Probanden fixiert wird, was zum einen zu einer Fixierung des Auges 2 und zum anderen aufgrund der Helligkeit der Fixiermarke zu einer Engstellung der Irisblende 7 führt, da sich das Auge 2 selbständig an die Beleuchtungsverhältnisse anpaßt. Die Fi- xiermarke wird durch eine als Fixiermarkenprojektor ausge¬ führte zweite Lichtquelle erzeugt und über einen Lichtwel¬ lenleiter 13 in das Sichtfeld eingeblendet. Die Licht¬ austrittsöffnung des Lichtwellenleiters 13 ist hierbei so vor der hochaperturigen Linse 9 angeordnet, daß die Fixier- marke nur dann die Retina vollständig erreicht, wenn sich das Auge 2 in der günstigsten Meßposition befindet.The actual calculation of the blood glucose concentration is then carried out by the evaluation unit 12, which first subjects the output signal of the light detector 10 to Fourier transform infrared Raman spectroscopy and calculates the blood glucose concentration from the spectral intensity distribution using a computing unit. In addition, the device shown enables the eye 2 to be fixed and the iris 7 to be narrowed in order to prevent damage to the sensitive retina by the measurement radiation. For this purpose, a fixation mark is faded into the field of vision, which is fixed by the test subject, which on the one hand leads to a fixation of the eye 2 and, on the other hand, to a narrowing of the iris diaphragm 7 due to the brightness of the fixation mark, since the eye 2 independently adjusts to the lighting conditions adjusts. The fixing mark is generated by a second light source designed as a fixing mark projector and is faded into the field of view via a light waveguide 13. The light exit opening of the optical waveguide 13 is arranged in front of the high-aperture lens 9 in such a way that the fixation mark only fully reaches the retina when the eye 2 is in the most favorable measuring position.
Figur 2 zeigt zum einen die Anordnung der vorstehend nur schematisch dargestellten Vorrichtung in einem Binokular- Sichtgerät 14 und zum anderen die Benutzung des Binokular- Sichtgerätes 14 durch die zu untersuchende Person 15.FIG. 2 shows, on the one hand, the arrangement of the device shown only schematically above in a binocular viewing device 14 and, on the other hand, the use of the binocular viewing device 14 by the person 15 to be examined.
Die vorstehend beschriebene Vorrichtung ist hierbei in dem Tubus 16.1 des Binokular-Sichtgerätes 14 angeordnet, der mit einem Okular 17.1 auf das rechte Auge des Probanden 15 aufgesetzt wird. Der andere Tubus 16.2 enthält dagegen ein Display 18, das an der Übergangsstelle zu dem zugehörigen Okular 17.2 angeordnet ist. Dieses Display 18 wird von der Auswertungseinheit angesteuert und zeigt die gemessene Blutglukosekonzentration an, so daß die zu untersuchende Person 15 lediglich in das Binokular-Sichtgerät 14 hinein- sehen muß und sofort die Blutglukosekonzentration angezeigt bekommt. Die erfindungsgemäße Vorrichtung ist also so ein- fach handhabbar, daß ein Diabetiker die Ermittlung des Blutglukosewerts im Selbsttest vornehmen kann.The device described above is arranged in the tube 16.1 of the binocular viewing device 14, which is placed on the right eye of the subject 15 with an eyepiece 17.1. The other tube 16.2, on the other hand, contains a display 18 which is arranged at the transition point to the associated eyepiece 17.2. This display 18 is controlled by the evaluation unit and shows the measured blood glucose concentration, so that the person 15 to be examined only has to look into the binocular vision device 14 and the blood glucose concentration is immediately displayed. The device according to the invention is thus easy to handle that a diabetic can determine the blood glucose value in a self-test.
Figur 3 zeigt schließlich eine alternative Ausführungsform der erfindungsgemäßen Vorrichtung zur Bestimmunng der Blut- glukosekonzentration, wobei - wie bei dem in Figur 1 darge¬ stellten Ausführungsbeispiel - Meßstrahlung in die Vorder¬ kammer 1 eines Auges 2 eingeleitet und der Anteil der re¬ flektierten bzw. rückgestreuten Meßstrahlung gemessen wird.FIG. 3 finally shows an alternative embodiment of the device according to the invention for determining the blood glucose concentration, measuring radiation being introduced into the front chamber 1 of an eye 2 as in the exemplary embodiment shown in FIG. 1, and the proportion of the reflected or backscattered measuring radiation is measured.
Die Meßstrahlung wird hierbei durch eine Lichtquelle 19 er- zeugt, deren Emissionswellenlänge oberhalb von 1,5 μm liegt, so daß die Meßstrahlung von der im wesentlichen aus Wasser bestehenden Augenflüssigkeit stark absorbiert wird. Hierdurch wird vorteilhaft eine Schädigung der empfindli¬ chen Retina durch die Meßstrahlung verhindert, da die Meß- Strahlung nach dem Durchlaufen des Augeninnenraums bis zum Erreichen der Retina durch die Augenflüssigkeit hinreichend stark abgeschwächt ist, um eine Schädigung der Retina aus¬ zuschließen. Im Gegensatz zu der in Figur 1 dargestellten Ausführungsform benötigt die dargestellte Ausführungsform deshalb keine separate Fokussierungsoptik, um eine direkte Belichtung der Retina zu verhindern.The measuring radiation is generated here by a light source 19, the emission wavelength of which is above 1.5 μm, so that the measuring radiation is strongly absorbed by the eye fluid, which essentially consists of water. This advantageously prevents damage to the sensitive retina from the measuring radiation, since the measuring radiation is sufficiently attenuated after it has passed through the interior of the eye until the eye fluid reaches the retina to prevent damage to the retina. In contrast to the embodiment shown in FIG. 1, the embodiment shown therefore does not require separate focusing optics in order to prevent direct exposure of the retina.
Die von der Lichtquelle 19 erzeugte Meßstrahlung wird über die Kolimationslinse 20 und den teildurchlässigen Spiegel 21 in das Sichtfeld des Auges 2 eingeblendet und von der Fokussierlinse 22 in der Vorderkammer 1 des Auges 2 fokus¬ siert. Die von der Glukkosekonzentration abhängige Raman¬ strahlung wird durch die hochaperturige Fokussierlinse 22 gesammelt und durchdringt den teildurchlässigen Spiegel 21, der für die spektrale Intensitätsverteilung der Ramanstrah- lung eine hohe Transparenz aufweist. Anschließend erreicht die reflektierte Meßstrahlung den Lichtdetektor 23, der ausgangsseitig mit der Auswertungseinheit 24 verbunden ist. Die Meßstrahlung wird von der Auswertungseinheit 24 zu¬ nächst einer Fourier-Transform-Raman-Spektroskopie unterzo- gen, um anschließend in Abhängigkeit von dem ermittelten Spektrum der Ramanstrahlung die Blutglukosekonzentration berechnen zu können.The measuring radiation generated by the light source 19 is faded into the field of view of the eye 2 via the colimation lens 20 and the partially transparent mirror 21 and is focused by the focusing lens 22 in the front chamber 1 of the eye 2. The Raman radiation, which is dependent on the glucose concentration, is collected by the high-aperture focusing lens 22 and penetrates the partially transparent mirror 21, which has a high degree of transparency for the spectral intensity distribution of the Raman radiation. Then reached the reflected measuring radiation the light detector 23, which is connected on the output side to the evaluation unit 24. The measurement radiation is first subjected to a Fourier transform Raman spectroscopy by the evaluation unit 24, in order then to be able to calculate the blood glucose concentration as a function of the determined spectrum of the Raman radiation.
Die Erfindung beschränkt sich in ihrer Ausführung nicht auf die vorstehend angegebenen bevorzugten Ausführungsbeispie- le. Vielmehr ist eine Anzahl von Varianten denkbar, welche von der dargestellten Lösung auch bei grundsätzlich anders gearteten Ausführungen Gebrauch macht.The embodiment of the invention is not limited to the preferred exemplary embodiments specified above. Rather, a number of variants are conceivable which make use of the solution shown, even in the case of fundamentally different types.
* * * * * * * * * *

Claims

Ansprüche Expectations
1. Vorrichtung zur nichtinvasiven Bestimmung der Konzen¬ tration eines Blutbestandteils, insbesondere zur Blutgluko¬ sebestimmung, mit einer ersten Lichtquelle (3, 19) zur Erzeugung von Meß- Strahlung zur Einstrahlung auf einen Körperteil (2) mit ei¬ ner Wellenlänge, bei der die optischen Eigenschaften des bestrahlten Körperteils (2) von der Konzentration des zu bestimmenden Blutbestandteils in dem bestrahlten Körperteil (2) abhängen, einem Lichtdetektor (10, 23) zur Erfassung der in dem be¬ strahlten Körperteil (2) konzentrationsabhängig abge¬ schwächten Meßstrahlung sowie einer eingangsseitig mit dem Lichtdetektor (10, 23) verbun¬ denen Auswertungseinheit (12, 24) zur Ermittlung der Kon- zentration des Blutbestandteils in Abhängigkeit von der durch den Lichtdetektor (10, 23) erfaßten Meßstrahlung, dadurch gekennzeichnet, daß der bestrahlte Körperteil ein Auge (2) ist, wobei der Lichtdetektor (10, 23) zur Reflexionsmessung im Strahlen- gang der in der Augenvorderkammer (1) reflektierten oder rückgestreuten Meßstrahlung angeordnet ist, daß zwischen der ersten Lichtquelle (3, 19) und dem be¬ strahlten Auge (2) zur Vermeidung einer Retinaschadigung durch die Meßstrahlung eine Fokussierungsoptik (6) angeord- net ist, die die Meßstrahlung derart in der Augenvorderkam¬ mer (1) fokussiert, daß die Meßstrahlung retinaseitig im wesentlichen von der Iris (7) aufgehalten wird und/oder daß die Wellenlänge der Meßstrahlung zur Verhinderung einer Re¬ tinaschadigung durch die Meßstrahlung im Absorptionsbereich der Augenflüssigkeit liegt.1. Device for the non-invasive determination of the concentration of a blood component, in particular for determining blood glucose, with a first light source (3, 19) for generating measuring radiation for irradiation onto a body part (2) with a wavelength at which the optical properties of the irradiated body part (2) depend on the concentration of the blood component to be determined in the irradiated body part (2), a light detector (10, 23) for detecting the measurement radiation attenuated in a concentration-dependent manner in the irradiated body part (2) and an evaluation unit (12, 24) connected on the input side to the light detector (10, 23) for determining the concentration of the blood component as a function of the measurement radiation detected by the light detector (10, 23), characterized in that the irradiated body part is a Is eye (2), the light detector (10, 23) for reflection measurement in the beam path that in the front of the eye arranged (1) reflected or back-scattered measuring radiation that between the first light source (3, 19) and the irradiated eye (2) to avoid retina damage by the measuring radiation, a focusing optics (6) is arranged, which the measuring radiation focused in the anterior chamber (1) in such a way that the measuring radiation on the retinal side is essentially stopped by the iris (7) and / or that the wavelength of the measuring radiation for preventing re-damage by the measuring radiation lies in the absorption area of the eye fluid.
2. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß die Fokussierungsoptik ein hochaperturiges und kurz- brennweitiges Dunkelfeldbeleuchtungsobjektiv (6) ist.2. Device according to claim 1, characterized in that the focusing optics is a high aperture and short focal length dark field illumination lens (6).
3. Vorrichtung nach Anspruch 1 oder 2, dadurch gekenn¬ zeichnet, daß die erste Lichtquelle (3) mit ihrer Lichtaus¬ trittsrichtung quer zur optischen Achse des Dunkelfeld- beleuchtungsobjektivs (6) angeordnet ist und zur Umlenkung der von der ersten Lichtquelle (3) erzeugten Meßstrahlung auf das Dunkelfeldbeleuchtungsobjektiv (6) ein teildurch¬ lässiger oder ringförmiger Spiegel (5) vorgesehen ist.3. Device according to claim 1 or 2, characterized gekenn¬ characterized in that the first light source (3) with its light exit direction is arranged transversely to the optical axis of the dark field illumination lens (6) and for deflecting the from the first light source (3) generated measuring radiation on the dark field illumination objective (6) a partially transparent or ring-shaped mirror (5) is provided.
4. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß zur Fixierung des Auges (2) so¬ wie zur Engstellung der Iris (7) eine zweite Lichtquelle mit einer im sichtbaren Spektralbereich liegenden Emissi¬ onswellenlänge vorgesehen ist, die mit ihrer Licht¬ austrittsöffnung räumlich fixiert vor dem bestrahlten Auge (2) derart angeordnet ist, daß deren Strahlung die Retina des Auges (2) als Fixiermarke erreicht.4. Device according to one of the preceding claims, characterized in that for fixing the eye (2) and for constricting the iris (7) a second light source with an emissi¬ on wavelength in the visible spectral range is provided, which with its Licht¬ exit opening spatially fixed in front of the irradiated eye (2) is arranged such that its radiation reaches the retina of the eye (2) as a fixation mark.
5. Vorrichtung nach Anspruch 4, dadurch gekennzeichnet, daß zur Einblendung der Fixiermarke in das Sichtfeld des bestrahlten Auges (2) ein Lichtwellenleiter (13) vorgesehen ist, der eingangsseitig mit der zweiten Lichtquelle verbun¬ den und ausgangsseitig mit seiner Lichtaustrittsöffnung vor dem bestrahlten Auge (2) und diesem zugewandt angeordnet ist.5. The device according to claim 4, characterized in that for fading in the fixing mark in the field of view of the irradiated eye (2) an optical waveguide (13) is provided, the verbun¬ the input side with the second light source and the output side with its light exit opening the irradiated eye (2) and this is arranged facing.
6. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Wellenlänge der Meßstrah- lung zur Anregung von Ramanbanden im Spektralbereich im we¬ sentlichen zwischen 650 nm und 2,5 um liegt.6. Device according to one of the preceding claims, characterized in that the wavelength of the measuring radiation for exciting Raman bands in the spectral range is substantially between 650 nm and 2.5 µm.
7. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß die Wellenlänge der Meßstrah¬ lung zur Verhinderung einer Retinaschadigung durch Absorp- tion der Meßstrahlung an der Augenflüssigkeit im wesentli¬ chen größer als 1,5 um ist.7. Device according to one of the preceding claims, characterized in that the wavelength of the measuring radiation to prevent retinal damage by absorption of the measuring radiation on the eye fluid is substantially greater than 1.5 µm.
8. Vorrichtung nach einem der vorhergehenden Ansprüche, dadurch gekennzeichnet, daß zwischen dem Lichtdetektor (10) und dem Auge (2) ein optisches Filter (11) angeordnet ist, das Licht in solchen Wellenlängenbereichen unterdrückt, in denen die Intensität der reflektierten oder rückgestreuten Meßstrahlung nur eine geringe Abhängigkeit von der zu be¬ stimmenden Konzentration aufweist.8. Device according to one of the preceding claims, characterized in that an optical filter (11) is arranged between the light detector (10) and the eye (2), which suppresses light in those wavelength ranges in which the intensity of the reflected or backscattered measuring radiation has only a slight dependence on the concentration to be determined.
9. Vorrichtung nach einem der vorhergehenden Ansprüche, gekennzeichnet durch die Anordnung in einem Binokularsicht¬ gerät (14), wobei in dem einem Tubus (16.1) des Binokular¬ sichtgerätes (14) mindestens die erste Lichtquelle (3, 19) und der Lichtdetektor (10, 23) und in dem anderen Tubus9. Device according to one of the preceding claims, characterized by the arrangement in a binocular view device (14), wherein in the one tube (16.1) of the binocular view device (14) at least the first light source (3, 19) and the light detector ( 10, 23) and in the other tube
(16.2) des Binokularsichtgerätes (14) eine eingangsseitig mit der Auswertungseinheit (12, 24) verbundene optische An- Zeigeeinrichtung (18) zur Ausgabe der gemessenen Konzentra¬ tion angeordnet ist. (16.2) of the binocular viewer (14) has an optical input connected to the evaluation unit (12, 24) on the input side. Pointing device (18) is arranged for outputting the measured concentration.
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