Apparatus and method for improved detection of analyte measurements with detection of deflection of a detection beam

Abstract

Disclosed herein is a device (10) for analyzing a material (12) comprising at least one analyte, the device (10) comprising a measuring body (16) having a contact surface (14) adapted for being in thermal or pressure-transmitting contact with the material (12), an excitation radiation source configured for irradiating excitation radiation into the material (12) to be absorbed therein, and a detection light source for generating a detection light beam (22) travelling through at least a portion of the measuring body (16) or a component comprised in the measuring body (16), wherein the detection light beam is directed to be totally or partially reflected at the contact surface (14), wherein the contact surface (14) of the measuring body is curved in at least one main direction in an area where the detection light beam (22) is reflected.

Description

TECHNICAL FIELD

[0001] The present application relates generally to devices and methods for analyzing a material comprising at least one analyte, e.g. a fluid. In particular, the present application relates to devices and methods for non-invasive measurement of an analyte in a body fluid, such as the glucose concentration in human skin, in particular in the interstitial fluid of human skin. BACKGROUND

[0002] The present application relates to devices and methods for analyzing a material comprising at least one analyte. The device comprises a measurement body having a contact surface adapted for being in thermal or pressure-transferring contact with the material, which thermal or pressure-transferring contact allows for a transfer of heat or pressure waves generated by an excitation radiation absorption in the material to the measurement body.

[0003] The device further comprises an excitation radiation source configured for irradiating excitation radiation into the material for absorption therein, and a detection apparatus for detecting a physical response of the measurement body or a component included therein to heat or pressure waves received from the material upon absorption of the excitation radiation, and for generating a response signal based on the detected physical response. In this context, the response signal is indicative of the degree of absorption of the excitation radiation.

[0004] The present application is not limited to any particular physical response to heat or pressure waves received from the material upon absorption of the excitation radiation, nor to any particular way of detecting this physical response in a way that allows for generating a response signal indicative of the degree of excitation radiation absorption. The applicant has previously proposed various physical responses and corresponding detection methods for these types of analyte measurement procedures, and they are briefly outlined below, and each of them can be applied to the present application.

[0005] For example, the detection apparatus can comprise a light source for generating a detection light beam travelling through at least a portion of the measurement body or a component included in the measurement body, and the physical response of the measurement body to heat or pressure waves received from the material upon absorption of the excitation radiation can be a local change in the refractive index of the measurement body or the component. In this case, the detection apparatus can be configured for detecting one of a change in the optical path or a change in the phase of the detection light beam due to the change in the refractive index of the material of the measurement body or the component included therein.

[0006] For example, in various methods and devices described in detail in two earlier applications of the present applicant, published as WO 2015 / 193310 Al and WO 2017 / 097824 Al (both included by reference herein), the measuring body transmits the detection beam and the detection beam is directed to be totally or partially reflected at the surface of the measuring body in thermal contact with the material. In this case, the detection device can comprise a photodetector, in particular a position sensitive photodetector, able to detect the degree of deflection, in particular the angle of deflection, of the detection beam due to the local variation of the refractive index. In this case, therefore, the physical response of the measuring body to the thermal or pressure wave received from the material after absorption of the excitation radiation is the local variation of the refractive index and the response signal is the detected degree of deflection, which in fact was found to be able to indicate the degree of absorption of the excitation radiation.

[0007] In an alternative variant proposed by the present applicant, disclosed for example in international application PCT / EP2019 / 064356 (included by reference herein), the detection device can comprise an interferometric measurement device to allow the evaluation of the phase variation of the detection beam and the generation of a response signal indicative of the phase variation. In this case, the physical response of the measuring body (or of the components included therein) to the thermal or pressure wave received from the material after absorption of the excitation radiation is again a local variation of the refractive index, while in this case the response signal is an interferometric signal reflecting the phase variation of the detection beam due to the local variation of the refractive index.

[0008] In yet another alternative embodiment, the measuring body or a component of the measuring body can have an electrical property that varies in response to a local variation of the temperature or a change in pressure associated therewith, and the detection device comprises an electrode for capturing an electrical signal representative of the electrical property. Various possible settings are disclosed in WO 2019 / 110597 A2, included by reference herein. For example, the measuring body can comprise a portion having piezoelectric properties and the pressure variation associated with the received heat causes an electrical signal that can be recorded with an electrode. In this case, the change in pressure is similar to the physical response of the measuring body or of the components included therein to the thermal received from the material after absorption of the excitation radiation, which is detected using the piezoelectric properties of the measuring body and the electrode and causes an electrical signal representative of the above-mentioned response signal indicative of the degree of absorption of the excitation radiation. In yet another variant, a very sensitive temperature sensor can be used to directly measure the temperature variation due to the received heat.

[0009] It is noted that in the following description, the physical response of the measuring body to the heat received from the material is described in detail. However, it will be appreciated that in various embodiments of the method and apparatus of the present application, the material is in pressure-transmitting contact with the measuring body, and the physical response of the measuring body is to a pressure wave received from the material. In this context, the expression "pressure-transmitting contact" shall include all relationships which allow a pressure wave to be transmitted from the material to the measuring body, and in particular an acoustically-coupled relationship, wherein the coupling can be established by a gas, a liquid or a solid. All detailed explanations given in connection with thermal contact and the physical response of the measuring body to the heat received from the material shall be understood in connection with scenarios including pressure-transmitting contact and a physical response to a pressure wave, as applicable, without the need for an explicit reference.

[0010] The apparatus can also be configured for performing an analysis step, in which the analysis is performed based at least partly on the response signal. For this purpose, the apparatus can comprise a control system comprising one or more processors programmed to perform the analysis. If, for example, it is of interest to determine the concentration of an analyte in the material, the excitation radiation can be selected to have a characteristic wavelength of the absorption spectrum of the analyte, e.g. in relation to an absorption peak thereof. Since the response signal is indicative of the degree of absorption of the excitation radiation, in this case the response signal is directly related to the concentration of the analyte in the material. The analysis step can thus be based at least partly on a measurement of the concentration of the analyte in the material, and in some non-limiting applications it can in fact amount to determining this concentration.

[0011] For example, the Applicant has employed an apparatus of the above-described type to non-invasively measure the glucose level of a user. In this particular application, the "analyte" is formed by glucose, and the "material" is the skin of the user. It has previously been demonstrated that this method allows to very accurately measure the glucose concentration in the interstitial fluid within the skin of a person, which was found to be directly related to the glucose content in the blood of the patient, and thus to represent the glucose content in the blood of the patient. The method and apparatus of the present application Figure 4 The results of a Clark error grid analysis taken from WO 2017 / 097824 Al are shown, indicating that the above-described apparatus and analysis method allow to very accurately predict the actual glucose concentration of a person.

[0012] However, it is desirable to further improve the accuracy and reliability of the analysis results. SUMMARY

[0014] It is an object of the present application to provide an apparatus and a method for analyzing a material as described above, which allow to improve the accuracy or reliability of the analysis results.

[0015] This problem is solved by the apparatus and method according to the independent claims. Preferred embodiments are defined in the dependent claims.

[0016] According to an aspect of the present application, there is provided a device for analyzing a material comprising at least one analyte, the device comprising,

[0017] a measurement body having a contact surface adapted for being in thermal or pressure-transmitting contact with the material, the thermal or pressure-transmitting contact allowing for a thermal wave or pressure wave generated by absorption of excitation radiation in the material to be transmitted to the measurement body,

[0018] an excitation radiation source configured for irradiating excitation radiation into the material to be absorbed, and

[0019] a detection light source for generating a detection light beam travelling through at least a portion of the measurement body or an assembly comprised in the measurement body. Here, the detection light beam is directed to be totally or partially reflected at the contact surface, wherein the detection light beam is deflected upon a thermal wave or pressure wave generated by absorption of excitation radiation transmitted into the material of the measurement body. The device comprises a detector for detecting the degree of deflection, in particular the deflection angle, of the detection light beam after reflection at the contact surface. Further, the contact surface of the measurement body is curved in at least one main direction in the region where the detection light beam is reflected.

[0020] According to an aspect of the present application, the detection light beam is directed to be totally or partially reflected at the contact surface in thermal or pressure-transmitting contact with the material.

[0021] It is noted that the concept of the detection light beam being "deflected" relates to a total change of the angle at the detector or, in other words, how the detection position of the detection light beam differs from its position without excitation and absorption by the material. This "deflection" is thus a cumulative effect of the local changes of the refractive index on the detection light beam along its optical path. A closer inspection shows that in many cases a part of the deflection of the light beam due to the local changes of the refractive index occurs before the detection light beam is reflected at the surface of the measurement body in thermal or pressure-transmitting contact with the material, in which case this surface is formed by a protruding front surface. The local changes of the refractive index thus also generally lead to a shift of the exact position at which the detection light beam is reflected at the surface.

[0022] In view of this understanding, according to an aspect of the present application, the contact surface is curved in at least one main direction. This curvature implies that the change of the position at which the detection light beam is reflected is also accompanied by a change of the angle of incidence and thus also leads to a corresponding change of the angle of reflection. Thus, using a curved reflection surface, it is possible to increase the total deflection as assessed by the detection device, such as a shift of the position detected with a position sensitive detector.

[0023] In a preferred embodiment, the curvature in the at least one main direction corresponds to a radius curvature of 5-30 mm, preferably 10-20 mm.

[0024] In a preferred embodiment, the curvature in the at least one principal direction is one of concave or convex.

[0025] In a preferred embodiment, the detection light beams define a detection light plane before and after reflection at the front surface, and the at least one principal direction lies within the detection light plane, or forms an angle with the detection light plane of less than 30°, preferably less than 20°. In this way, it is ensured that the main effect of the curvature on the deflection lies in the detection light plane.

[0026] In a preferred embodiment, the detection light source is arranged such that the detection light beam is irradiated into the measurement body at an entrance surface, propagates through a portion of the measurement body, and exits the measurement body at an exit surface, wherein the detection light beam - in the absence of any deflection due to local variations of the refractive index - impinges on the exit surface at an angle of 5° or more, preferably 10° or more, and most preferably 15° or more, relative to a normal of the exit surface, such that the detection light beam is refracted after exiting the exit surface of the measurement body, wherein the exit surface is relative to the direction of the detection light beam such that the deflection of the detection light beam in response to the heat or pressure wave transmitted to the measurement body increases the angle of the detection light beam relative to the normal of the exit surface.

[0027] In the applicant's previous designs, the shape of the measurement body was usually chosen such that the detection light beam was perpendicular to the entrance surface and the exit surface, to avoid losses due to reflection, and to avoid refraction, which at first glance would only complicate the optical setup further. However, according to this embodiment, the detection light source is arranged such that the detection light beam is deliberately refracted at the exit surface in the above-mentioned way. Since the refractive index of the measurement body will typically be higher than the surrounding refractive index, an increase in the angle of the detection light beam perpendicular to the exit surface will lead to an even greater increase in the angle of the refracted light beam, such that the deflection of the light beam detected at the detection device is further increased, resulting in a larger response signal. In this way, the signal-to-noise ratio can be improved. The greater the deviation of the angle of incidence of the detection light beam from the normal of the exit surface, the greater this effect will typically be. However, of course the "critical" angle of total reflection must be avoided. Furthermore, for angles close to this critical angle, the proportion of the light of the detection light beam reflected at the exit surface will increase, thereby attenuating the intensity of the refracted detection light beam that actually reaches the detection device, such as a photodetector. Thus, the optimal choice of the angle of incidence can be a compromise between a greater degree of refraction of the refracted detection light beam and a sufficient intensity. In any case, the deviation of the angle of incidence from the normal should be at least 5°, and preferably at least 10°, and most preferably at least 15°. While this embodiment is advantageously used with a curved contact surface, it can also be employed in embodiments without such a curved contact surface.

[0028] In a preferred embodiment, the arrangement of the detection light source is such that the detection light beam is irradiated into the measurement body at an entrance surface, propagates through a portion of the measurement body, and exits the measurement body at an exit surface, wherein a focusing lens is attached to or integrally shaped with the entrance surface for focusing the detection light beam into the measurement body in at least one dimension, and / or a collimating lens is attached to or integrally shaped with the exit surface for collimating the detection light beam in at least one dimension.

[0029] The inventors have noticed that the measurement quality is improved if the detection light beam is focused when reflected on the contact surface, which is also the area where it will interact with the thermal lens formed in the measurement body. For a crisp feature deflection, it is advantageous if the diameter of the detection light beam in this area is relatively small, which can be achieved with the focusing mirror. In other words, the purpose of the focusing mirror is not necessarily to truly focus the detection light beam on a certain focal point, but to reduce its diameter at least in the area where it interacts with the thermal lens. However, such a focusing means that the detection light beam diverges on its path towards the detection device. This is usually not too important if the detection device, like a position sensitive detector, is arranged directly adjacent or at least close to the exit surface of the detection light beam. However, the inventors found that the signal-to-noise ratio of the measurement can be further increased if the distance between the exit surface and the detector is increased, as this will lead to a larger deflection degree, for example by a larger change in position where the detection light beam hits the position sensitive detector. Note that in this context, the “larger deflection degree” has nothing to do with a larger deflection angle, which is one possible meaning of “deflection degree”, but a larger impact of the deflection detected by the detection device. For example, the distance between the reflection at the contact surface of the measurement body and the detection at the detection device can be at least 4 cm, in some embodiments even 9 cm or more, introducing a certain leverage on the deflection detected by the detection device. However, when the detection device is located at a considerable distance from the exit surface, it is advantageous if the detection light beam is collimated after leaving the measurement body to keep the diameter of the detection light beam constant. However, it is important to emphasize that it is not always necessary to focus and collimate in both dimensions, in many practical applications it can even be desirable to have some spread in one of the directions, which will be explained below. Therefore, the focusing mirror and / or the other collimating lens must be effective in at least one dimension only. In fact, in a preferred embodiment, at least one of the focusing mirror and the collimating lens is a cylindrical lens, which focuses and collimates the detection light beam, respectively, at least mainly in one dimension.

[0030] Furthermore, by attaching the focusing and / or collimating lenses to the measurement body, or even more preferably by forming them integrally with the measurement body, no separate adjustment of these lenses is required during assembly of the device or even during use of the device. While this embodiment is advantageously used with a curved contact surface, it can also be employed in embodiments without such a curved contact surface.

[0031] In a preferred embodiment, the detector comprises a position sensitive detector at which the detection beam impinges, wherein the position sensitive detector is sensitive to changes in position of the detection beam impinging thereon in at least one sensing direction. Furthermore, the position sensitive detector is arranged such that the deflection of the detection beam results in a change in position of the detection beam impinging thereon in the at least one sensing direction. Finally, a cylindrical lens is provided in the optical path of the detection beam for shaping the profile of the detection beam such that the diameter of the detection beam impinging on the position sensitive detector in the sensing direction is at least 1.5 times larger, preferably at least 2.0 times larger than the diameter of the detection beam in a direction perpendicular to the sensing direction. The inventors noticed that when using a position sensitive detector that is sensitive to changes in position of the detection beam impinging thereon in at least one sensing direction, the signal-to-noise ratio can be increased and, in some embodiments, the linearity of the sensor output is increased if the beam profile is such that the light spot formed on the position sensitive detector is elongated in the sensing direction in the above-mentioned way. This is especially true for a position sensitive detector that measures the difference in current of its respective ends. The elongated shape of the light spot according to this aspect of the application is established using such a cylindrical lens. While this embodiment is advantageously used with a curved contact surface, it can also be employed in embodiments without such a curved contact surface.

[0032] In a preferred embodiment, the cylindrical lens is a collimating lens arranged in the optical path of the detection beam between its reflection at the contact surface and the position sensitive detector, wherein the cylindrical lens is arranged to collimate the detection beam at least predominantly, but possibly exclusively, in a dimension perpendicular to the sensing direction of the position sensitive detector, wherein the cylindrical collimating lens is preferably integrally shaped with the exit surface of the measurement body from which the detection beam exits the measurement body.

[0033] Additionally or alternatively, the position sensitive detector can be arranged at an angle of 90° from the detection beam, such that due to this angle an elongated light spot is formed on the position sensitive detector, which light spot has a larger extension in the sensing direction.

[0034] In a preferred embodiment, the device further comprises a beam splitter that splits the light source beam into the detection beam and a reference beam, wherein the reference beam is likewise directed at the surface of the measurement body that is in thermal or pressure-transmitting contact with the material, but in a region where any influence of thermal or pressure waves received from the material upon absorption of the excitation radiation is negligible. Furthermore, the device comprises further detection equipment for detecting a deflection, in particular an angle of deflection, of the reference beam after its reflection at the contact surface, wherein the detection equipment preferably comprises a photodetector, in particular a position-sensitive photodetector.

[0035] The reference beam is exposed to the same type of external influences as the detection beam, except for thermal or pressure waves due to the absorption of the excitation radiation. Thus, by measuring the possible deflection of the reference beam, these external influences can be considered and eliminated from the measurement results obtained with the detection beam. While in the preferred embodiment the additional reference beam is combined with a curved contact surface, it can also be employed in embodiments without such a curved contact surface.

[0036] According to another aspect of the present application, a protrusion is formed on the contact surface, the protrusion having a front surface facing the material, and when the material is in contact with the contact surface, the protrusion is in contact with the material, and the excitation radiation is irradiated into the material through the front surface of the protrusion.

[0037] The inventors have noted that one key aspect of the measurement procedure performed by the device is that the excitation radiation is reliably and consistently transmitted into the material. In some devices described by the present applicant in the above-mentioned prior application, the excitation radiation is directed through the measurement body, such as to enter the material at the interface between the contact surface of the measurement body and the material, and it was observed that at this interface, in practice, the excitation radiation can often be well coupled into the material. It has been found that this is particularly true in applications where the material is formed by a user's fingertip, and the device is used to measure the glucose content in the skin. In this case, the fingertip is firmly placed on the contact surface of the measurement body, establishing sufficient optical coupling to allow the excitation radiation to enter the material through the contact surface of the measurement body.

[0038] However, extensive research has shown that imperfect and particularly unstable optical coupling can be a source of measurement inaccuracies. In particular, the inventors have noticed that the optical coupling can change during a single measurement, i.e. without intentionally moving the fingertip onto or even off the contact surface. If the optical coupling changes during the measurement, this leads to a change in the intensity of the excitation radiation that is actually absorbed by the analyte, and thus to a change in the response signal that is not related to the absorption rate of the analyte at the excitation radiation wavelength or the analyte concentration. In other words, a loss of light coupling during part of the measurement can be misinterpreted as a decrease in the absorption rate at a given excitation wavelength. Evaluating the analyte spectrum typically involves measuring the absorption at a plurality of characteristic wavelengths, e.g. wavelengths corresponding to peaks or local absorption minima of the analyte absorption spectrum, and also involves a mathematical combination of the response signals related to the different wavelengths, e.g. subtracting the response signal obtained at a local minimum of the absorption spectrum from the response signal of an absorption peak. It can thus be understood that in case the light coupling in the material, and thus the effective intensity of the excitation radiation, changes between measurements, or even during a measurement at a particular wavelength, artefacts and inaccuracies can occur in the measurement results.

[0039] It was not obvious to the inventors that unstable optical coupling would be a significant error source, and it was even less clear why the optical coupling between the contact surface and the material would change significantly during a measurement, as the fingertip was not intentionally moved during the measurement. One possible reason can be that the user inadvertently failed to keep the contact pressure between the finger and the contact surface constant. Another possible reason can be that the user inadvertently moved the fingertip slightly on the contact surface, and very small movements can have an unexpectedly large impact. This can be the case, for example, where the fingertip moves between a position where the excitation radiation enters the skin at a ridge of the epidermis of the fingertip and a position where the excitation radiation enters the skin between two ridges of the epidermis, where a decrease in optical coupling can occur.

[0040] Regardless of the exact underlying cause, the inventors have noticed that the optical contact and its consistency can be improved if a protrusion is formed on the contact surface, said protrusion having a front surface facing the material and being in contact with the material when the material is in contact with the contact surface, and if the excitation radiation is irradiated into the material through said front surface of said protrusion. That is, at the front surface of the protrusion, the local contact pressure is found to be significantly higher if the same total force is exerted by the finger on the contact surface than on a flat contact surface. This local increase in contact pressure allows for a better optical coupling, and in particular a more consistent optical coupling during the measurement.

[0041] It is noted that the protrusions not only allow for an improved optical coupling, but also for an improved thermal or pressure transfer coupling. Thus, in many cases, the protrusions will also facilitate an improved transfer of thermal or pressure waves generated by the absorption of the excitation radiation to be transferred into the material of the measurement body. While not an embodiment of the presently claimed invention, it is also contemplated herein to use such protrusions even if the excitation radiation is not irradiated into the material through its front surface. While not an embodiment of the present application, it is also contemplated to use such protrusions even if the excitation radiation is not irradiated into the material through the front surface of the material. In embodiments comprising a curved portion of the contact surface where the detected light beam is reflected, the additional advantages of the protrusions can be utilized as well, independently from the curved portion of the contact surface.

[0042] In preferred embodiments, the front surface is flat. However, the present application is not limited thereto and it can also be advantageous to have a curved front surface, as will be described below, particularly in case the detection relies on a reflected detection light beam. In other words, in some embodiments, the "curved portion of the contact surface" where the detection light beam is reflected can be formed by a curved front surface of the protrusions. In particular, in case the curved portion or part of the contact surface is convex, the curved portion itself can form the protrusion.

[0043] In preferred embodiments, the protrusions have a footprint area of less than 0.3 cm2, preferably less than 0.2 cm2, more preferably less than 0.1 cm2, even more preferably less than 0.05 cm2, and most preferably less than 0.02 cm2.

[0044] In preferred embodiments, the protrusions have a conical shape, wherein one or more sidewalls taper towards the front surface. This conical shape means that the front surface can be smaller than the footprint area and thus leads to even higher local contact pressures. The conical sidewalls also increase the stability of the protrusions. Furthermore, in some embodiments, in case the detection relies on a reflected detection light beam, the conical sidewalls make it easier for the detection light beam to enter the protrusions while keeping the contact surface small, as will be apparent from the description of the detailed embodiments below.

[0045] In some embodiments, the protrusions have a circular, elliptical or square shape of the footprint.

[0046] In particularly preferred embodiments, the protrusions are ridge-shaped, have a longer extension in a first direction and a shorter extension in a second direction perpendicular to the first direction, wherein the longer extension exceeds the shorter extension by at least 1.5 times, preferably by at least 2.0 times, more preferably by at least 2.5 times, and most preferably by at least 3.0 times. In this context, the expression "the longer extension exceeds the shorter extension by at least 1.5 times" will mean that if the shorter extension is 2 mm, the longer extension will be at least 3 mm.

[0047] In a preferred embodiment, a pressure sensor is provided for measuring the contact pressure between the material and the measurement body. In this context, the device preferably further comprises a control system configured to receive a signal from the pressure sensor indicative of the contact pressure between the material and the measurement body, wherein the control system is configured to check whether the contact pressure is below a predetermined threshold. In case the contact pressure is found to be below the threshold, the control system is configured to perform one or more of the following:

[0048] indicating to the user the lack of contact pressure,

[0049] preventing the start of an analyte measurement process, and

[0050] interrupting a current analyte measurement process.

[0051] In other words, while the protrusions help to establish a high contact pressure exactly where it is needed, i.e. at the front surface where the excitation radiation is coupled into the material, the reliability can even be improved further if the contact pressure is monitored and if the user is indicated that the contact pressure is insufficient, which can then be corrected. Furthermore, by preventing the start of an analyte measurement process or interrupting an already ongoing analyte measurement process, incorrect measurement results can be avoided in case of insufficient contact pressure.

[0052] In a preferred embodiment, the device further comprises a clamping device comprising clamping members which are movable between an open position, in which the clamping members are moved away from the contact surface of the measurement body, and a closed position, in which they are close to the contact surface, the clamping members being biased towards the closed position. When the clamping members are in the open position, a material can be placed on the contact surface and due to the biasing force towards the closed position, the clamping members are adapted to press the material against the contact surface. In this way, a predetermined contact pressure can be ensured.

[0053] In a preferred embodiment, the above-mentioned pressure sensor is arranged on the clamping device. While in a preferred embodiment the clamping device is combined with a curved contact surface, the clamping device can also be used in embodiments without such a curved contact surface.

[0054] In a preferred embodiment, the measuring body transmits the excitation radiation, wherein the excitation radiation source is configured for providing the excitation radiation as an excitation light beam. Furthermore, the arrangement of the excitation radiation source is such that the excitation light beam is irradiated into the measuring body at its entrance surface, propagates through a portion of the measuring body, and exits the measuring body at the contact surface. In the previous device, the applicant made sure that the excitation radiation beam hits the entrance surface at an angle of 90°, such as to avoid refraction and excessive reflection of the excitation radiation beam at the entrance surface. However, extensive studies have shown that another reason for unexpected variations of the excitation radiation actually reaching the material is a possible interference of the excitation radiation emitted from the excitation radiation source with the excitation radiation reflected back from the entrance surface of the measuring body. It was found that this interference does indeed cause fluctuations in the intensity of the excitation radiation in the material and thus immediately to variations of the response signal that are independent of the analyte concentration. Furthermore, the inventors found that by slightly tilting the angle of incidence of the excitation light beam, this influence can be suppressed and the precision and reliability of the measurement can be improved. Thus, in this embodiment, the excitation light beam is directed to hit the entrance surface at an angle of 89.0° or less, preferably 88.0° or less, and most preferably 87.5° or less. In this way, the unwanted interference can be reliably prevented. A further advantageous effect of doing so is that the excitation radiation can be prevented from being reflected back into the excitation radiation source, which can be damaged thereby. On the other hand, the angle of incidence should not deviate from 90° too much, such as to avoid losses due to excessive reflection. Thus, in this embodiment, the angle of incidence should be 82.0° or more, preferably 84.0° or more, and most preferably 85.0° or more. While this embodiment is advantageously used together with a protrusion on the contact surface, it can also be employed in embodiments without such a protrusion.

[0055] In a preferred embodiment, the excitation light beam hits the contact surface of the measuring body at an angle of 90° ± 1.5°, in order to thereby minimize losses due to reflection at the contact surface.

[0056] In a preferred embodiment, the entrance surface and the contact surface are tilted relative to each other at an angle of 1.0° or more, preferably 2.0° or more, and most preferably 2.5° or more, and 8.0° or less, preferably 6.0° or less, and most preferably 5.0° or less, at the respective portions of the measuring body where the excitation light beam enters and exits, respectively. Graphically speaking, the measuring body according to this embodiment can have a slightly "wedge-shaped" shape, which allows for establishing a slight tilt of the excitation light beam at the entrance surface and an orthogonal orientation thereof at the contact surface.

[0057] In a preferred embodiment, the material is human tissue, in particular human skin, and the analyte is glucose present in the skin, in particular in the interstitial fluid of the skin.

[0058] In a preferred embodiment, the excitation radiation is generated using a laser array, in particular quantum cascade lasers, each having a dedicated wavelength.

[0059] In an alternative preferred embodiment, the excitation radiation is generated using at least one tunable laser, in particular at least one tunable quantum cascade laser.

[0060] In a preferred embodiment, some or all of the excitation wavelengths are in the range of 5 pm - 13 pm, preferably 8 pm - 11 pm. In an alternative embodiment, some or all of the excitation wavelengths are in the range of 3 pm - 5 pm. This wavelength range can be used, for example, for detecting the absorption of CH2 and CH3 vibrations in fatty acids.

[0061] Another aspect of the present application relates to a method for analyzing a material comprising at least one analyte, the method comprising:

[0062] Bringing a measurement body having a contact surface into thermal or pressure-transmitting contact with the material, the thermal or pressure-transmitting contact allowing the transmission of thermal or pressure waves generated by the absorption of excitation radiation in the material to the measurement body,

[0063] Irradiating excitation radiation into the material for absorption therein, and

[0064] Detecting a physical response of the measurement body or a component comprised therein to the thermal or pressure waves received from the material upon absorption of the excitation radiation, and generating a response signal based on the detected physical response, the response signal being indicative of the degree of absorption of the excitation radiation,

[0065] characterized in that at the contact surface, a protrusion is formed, the protrusion having a front surface which faces towards the material and which comes into contact with the material when the material is in contact with the contact surface, and the excitation radiation is irradiated into the material through the front surface of the protrusion.

[0066] In a preferred embodiment of the method, the front surface is flat.

[0067] In a preferred embodiment of the method, the protrusion has a footprint area of less than 0.3 cm2, preferably less than 0.2 cm2, more preferably less than 0.1 cm2, even more preferably less than 0.05 cm2, and most preferably less than 0.02 cm2.

[0068] In a preferred embodiment of the method, the protrusion has a conical shape, wherein one or more sidewalls taper towards the front surface.

[0069] In a preferred embodiment of the method, the protrusion has a circular, elliptical or square shaped footprint.

[0070] In a preferred embodiment of the method, the protrusions are ridge-shaped, have a longer extension in a first direction and a shorter extension in a second direction perpendicular to the first direction, wherein the longer extension exceeds the shorter extension by at least 1.5 times, preferably by at least 2.0 times, more preferably by at least 2.5 times, and most preferably by at least 3.0 times.

[0071] In a preferred embodiment of the method, the contact pressure between the material and the measurement body is measured.

[0072] Preferably, the method further comprises the step of checking whether the contact pressure is below a predetermined threshold value, and in case the contact pressure is found to be below the threshold value, one or more of the following steps is performed:

[0073] indicating to the user the lack of contact pressure,

[0074] preventing the start of an analyte measurement process, and

[0075] interrupting a current analyte measurement process.

[0076] Preferably, the method further comprises the step of fixing the material to the contact surface using a clamping device, the clamping device comprising a clamping member movable between an open position, in which the clamping member is moved away from the contact surface of the measurement body, and a closed position, in which it is close to the contact surface, the clamping member being biased towards the closed position, wherein the material is placed on the contact surface when the clamping member is in the open position, and wherein the clamping member presses the material against the contact surface due to the biasing force towards the closed position.

[0077] In a preferred embodiment of the method, the pressure sensor is arranged on the clamping device.

[0078] In a preferred embodiment of the method, the measurement body is transmissive for the excitation radiation,

[0079] wherein the excitation radiation source provides the excitation radiation as an excitation light beam, and

[0080] wherein the excitation light beam is irradiated into the measurement body at an entry surface thereof, propagates through a portion of the measurement body, and exits the measurement body at the contact surface,

[0081] wherein the excitation light beam hits the entry surface at an angle of 89.0° or less, preferably 88.0° or less, and most preferably 87.5° or less, and 82.0° or more, preferably 84.0° or more, and most preferably 85.0° or more.

[0082] In a preferred embodiment of the method, the excitation light beam hits the contact surface of the measurement body at an angle of 90° ± 1.5°.

[0083] In a preferred embodiment of the method, the entrance surface and the contact surface are tilted relative to each other at an angle of 1.0° or more, preferably 2.0° or more, and most preferably 2.5° or more, and 8.0° or less, preferably 6.0° or less, and most preferably 5.0° or less, at their respective portions where the excitation light beam enters and leaves the measurement body, respectively.

[0084] In a preferred embodiment of the method, the detecting comprises generating a detection light beam that travels through at least a portion of the measurement body or of a component comprised in the measurement body,

[0085] The physical response of the measurement body to the heat or pressure wave received from the material after absorption of the excitation radiation is a local change of the refractive index of the measurement body or of the component, and

[0086] The detecting comprises one of a change of a detection light path or a change of a phase of the detection light beam due to the change of the refractive index.

[0087] In a preferred embodiment of the method, the measurement body is transparent to the detection light beam, the detection light beam is directed to be fully or partially reflected at a surface of the measurement body in thermal or pressure transfer contact with the material, and wherein the detecting comprises detecting a degree of deflection, in particular an angle of deflection, of the detection light beam after its reflection at the contact surface due to the local change of the refractive index, wherein the detecting is preferably performed using a photodetector, in particular a position sensitive photodetector.

[0088] In a preferred embodiment of the method, the detection light beam is directed to be fully or partially reflected at the front surface of the protrusion in thermal or pressure transfer contact with the material.

[0089] In a preferred embodiment of the method, the front surface of the protrusion is curved in at least one main direction. In this context, the curvature in the at least one main direction corresponds to a radius of curvature of 5-30 mm, preferably 10-20 mm. The curvature in the at least one main direction is one of concave or convex.

[0090] In a preferred embodiment of the method, the detection light beam before and after reflection at the front surface defines a detection light plane, and the at least one main direction lies within the detection light plane, or forms an angle of less than 30°, preferably less than 20°, with the detection light plane.

[0091] In a preferred embodiment of the method, the detection light beam before and after reflection at the front surface defines a detection light plane, and the first direction is parallel to the detection light plane, or forms an angle of less than 30°, preferably less than 20°, with the detection light plane.

[0092] In a preferred embodiment of the method, the detection light source is arranged such that the detection light beam is irradiated into the measurement body at an entrance surface, propagates through a portion of the measurement body, and exits the measurement body at an exit surface, wherein the detection light beam hits - in the absence of any deflection due to the local change in refractive index - the exit surface at an angle of 5° or more, preferably 10° or more, and most preferably 15° or more, relative to a normal of the exit surface, such that the detection light beam is refracted upon exiting the exit surface of the measurement body, wherein the exit surface is relative to the direction of the detection light beam such that the deflection of the detection light beam transmitted into the measurement body in response to the thermal or pressure wave increases the angle of the detection light beam to the normal of the exit surface.

[0093] In a preferred embodiment of the method, the detection light beam is irradiated into the measurement body at an entrance surface, propagates through a portion of the measurement body, and exits the measurement body at an exit surface, wherein a focusing lens is integrally shaped with the entrance surface for focusing the detection light beam into the measurement body in at least one dimension, and / or a collimating lens is integrally shaped with the exit surface for collimating the detection light beam in at least one dimension. Herein, at least one of the focusing lens and the collimating lens is preferably a cylindrical lens focusing and collimating, respectively, the detection light beam at least predominantly in one dimension.

[0094] In a preferred embodiment of the method, the detector comprises a position sensitive detector at which the detection light beam hits, wherein the position sensitive detector detects a change in position of the detection light beam hitting thereon in at least one sensing direction,

[0095] wherein the position sensitive detector is arranged such that the deflection of the detection light beam causes a change in position of the detection light beam hitting thereon in the at least one sensing direction, and

[0096] wherein a cylindrical lens is arranged in the optical path of the detection light beam for shaping the profile of the detection light beam, and / or the position sensitive detector is arranged at an angle of 90° from the detection light beam such that the diameter of the detection light beam hitting on the position sensitive detector in the sensing direction is at least 1.5 times larger, preferably at least 2.0 times larger, than the diameter of the detection light beam in a direction perpendicular to the sensing direction.

[0097] In a preferred embodiment of the method, the cylindrical lens is a collimator lens arranged in the optical path of the detection light beam between its reflection at the contact surface and the position sensitive detector, wherein the cylindrical lens collimates the detection light beam at least predominantly in a dimension perpendicular to the sensing direction of the position sensitive detector, wherein the cylindrical collimator lens is preferably integrally formed with an exit surface of the measurement body, at which the detection light beam exits the measurement body.

[0098] In a preferred embodiment of the method, the light source light beam is split into the detection light beam and a reference light beam, wherein the reference light beam is likewise directed at a surface of the measurement body in thermal or pressure transfer contact with the material, but in an area where any influence of thermal or pressure waves received from the material upon absorption of the excitation radiation is negligible, and wherein the degree of deflection, in particular the angle of deflection, of the reference light beam after its reflection at the contact surface is detected, preferably using a photodetector, in particular a position sensitive photodetector.

[0099] In a preferred embodiment of the method, the detection comprises using an interferometric measuring device which allows to evaluate the change of the phase of the detection light beam and to generate a response signal indicative of the change of the phase.

[0100] In a preferred embodiment of the method, the measurement body or a component in the measurement body has an electrical property which changes in response to a local change of temperature or a change of pressure associated therewith, and wherein the detection device comprises an electrode for capturing an electrical signal representative of the electrical property.

[0101] In a preferred embodiment of the method, an optical fiber is embedded in the measurement body, a detection light source is arranged at one end of the fiber for coupling detection light into the optical fiber, and a mode detector is arranged at the other end of the fiber, wherein using the mode detector, an optical mode of the detection light is detected which changes in response to a change of thermal or pressure waves received by the measurement body from the material, wherein the change of the optical mode preferably comprises a shift or a rotation of an interference pattern of the optical mode at the mode detector.

[0102] In a preferred embodiment of the method, the material is human tissue, in particular human skin, and the analyte is glucose present in the skin, in particular in the interstitial fluid of the skin.

[0103] Preferably, the method further comprises the step of generating the excitation radiation using a laser array, in particular a quantum cascade laser, each having a dedicated wavelength.

[0104] Preferably, the method further comprises the step of generating the excitation radiation using at least one tunable laser, in particular at least one tunable quantum cascade laser.

[0105] In a preferred embodiment of the method, some or all of the excitation wavelengths are in the range 5 pm - 13 pm, preferably 8 pm - 11 pm.

[0106] BRIEF DESCRIPTION OF DRAWINGS

[0107] Figure 1 is a schematic diagram of the measurement principle according to some embodiments of the present application.

[0108] Figure 2 shows the absorption spectrum of glucose in water, minus the water background.

[0109] Figure 3 is a schematic cross-sectional view of a device for analyzing a material, which relies on a response signal based on a deflection of a detection beam.

[0110] Figure 4 shows the Clarke error grid analysis results obtained with a device of the type shown in Figure 3

[0111] Figure 5 is a schematic diagram of a device for analyzing a material, which relies on a response signal based on a piezoelectric response based on a response to thermal and pressure waves received by the material under analysis.

[0112] Figure 6 is a schematic diagram of a device for analyzing a material, which relies on a response signal based on a phase change in interference detection in a detection beam.

[0113] Figure 7 is a schematic cross-sectional side view of a device according to one embodiment.

[0114] Figure 8 is a schematic cross-sectional front view of a device of Figure 7

[0115] is a schematic diagram of a device showing a deflection of a detection beam. Figure 9

[0116] is a schematic diagram of a device similar to Figure 10 Figure 9

[0117] Figure 11 is a schematic diagram showing increased deflection using a curved reflective surface for the detection beam.

[0118] Figure 12 is a schematic diagram of a device similar to Figure 7 ​​​​

[0119] Figure 13 is a schematic top view of an analogous device, in which a reference beam is used in addition to the detection beam. Figure 7

[0120] Figure 14 is a perspective view of the device of Figure 13

[0121] Figure 15 are schematic views of other devices, in which the response signal corresponds to an optical mode change formed in a fiber contained in the measurement body.

[0122] Figure 16 shows the same device as Figure 15 in the case where a thermal gradient is formed in the measurement body.

[0123] Figure 17 shows a device comprising a clamping apparatus.

[0124] Description of preferred embodiments

[0125] It is to be understood that both the foregoing general description and the following description are exemplary and explanatory only and are not restrictive of the methods and apparatus described herein. In this application, the use of the singular includes the plural, unless specifically stated otherwise. Also, the use of "or" means "and / or" as applicable, or is used in the alternative (not both). One of ordinary skill in the art will readily recognize that the description given herein merely illustrates and exemplifies the methods and apparatus and is not intended to limit the methods and apparatus in any way. Other embodiments will readily suggest themselves to such skilled persons having the benefit of this disclosure. Reference will now be made in detail to various implementations of the example embodiments as illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same or like parts.

[0126] Figure 1 is a schematic diagram of the measurement principle of the analyte measurement procedure outlined above and described in detail below. While the methods and devices of the present application are suitable for analyzing a variety of materials comprising at least one analyte, the following description will focus on a specific embodiment in which the material is the skin of a patient and the analyte is glucose in the interstitial fluid of the skin. It is to be understood that all details and explanations given below with specific reference to glucose measurement are also considered to be relevant for other materials and analytes (as applicable), not explicitly mentioned below.

[0127] In Figure 1 ​​In the illustration, the user's fingertip 12 is in thermal contact with the contact surface 14 of the measuring body 16. The fingertip can be acoustically coupled to the measuring body via an acoustic unit, which may include a hollow space filled with a liquid or gas that allows pressure waves to be transmitted to the measuring body. To determine the concentration of glucose in the skin, particularly in the interstitial fluid, various wavelengths of excitation radiation 18 are selected one after another, or at least partially, during absorption measurements, so that the glucose concentration can be determined from the measured absorption values. Figure 2 The image shows the absorption spectra of glucose at different concentrations in water, after subtracting the contribution from water absorption. As can be seen, glucose molecules exhibit several characteristic absorption peaks in the mid-infrared region, with wavenumbers ranging from 993 cm⁻¹. -1 and 1202 cm -1 The values ​​between these two values ​​correspond to wavelengths ranging from 10.07 µm to 8.32 µm. Local absorption minima can be observed between adjacent absorption peaks. Figure 2 The middle is indicated by a vertical arrow without wavenumber. From Figure 2 It is evident that absorption differences, particularly at absorption peaks and local absorption minima, are characteristic of glucose concentration. Therefore, to determine glucose concentration, it is preferable to measure the absorption at some or all absorption peaks and some or all local absorption minima, and possibly also at a point between the maximum and minimum values. These wavelengths are referred to herein as “analyte (glucose) characteristic wavelengths.” While wavelengths precisely at absorption peaks or local absorption minima are preferred for glucose characteristic wavelengths, wavelengths close to the peaks / local minima but at separately defined distances can also be used. Thus, as understood herein, an “analyte characteristic wavelength” is also one where the absorption difference between the absorption at the closest absorption peak or the closest local absorption minima is less than 30% of the absorption difference between the closest absorption peak and the closest local absorption minima, preferably less than 20%.

[0128] The intensity of the excitation beam is time-modulated at a specific frequency f, such that the excitation radiation (in this case, the excitation light) has alternating intervals of high and low intensity, or even fading intensity. It is not desirable to restrict the modulation to any particular waveform; the high-intensity intervals are referred to below as "excitation light pulses." During the excitation light pulse, the excitation light, having the characteristic wavelength of glucose, is absorbed, and thus the radiant energy is converted into heat. Since glucose molecules relax from the excited state in approximately 10⁻¹² s, the generation of the corresponding thermal pulse and / or pressure wave can be considered instantaneous for all practical purposes.

[0129] Thus, together with the excitation light pulse, a local heat pulse is generated at the site of absorption, which results in a temperature field that varies as a function of space and time and which can be referred to as a heat wave. As explained above, the term heat "wave" is somewhat misleading, as the travel of heat through the material is not governed by a wave equation, but by a diffusion equation. However, the concept of a "heat wave" is correct at least to the extent that the heat pulse propagates from within the skin to the surface 14 of the measurement body 16 and into the measurement body 16, which is similar to what one uses from wave propagation. The heat gradient 20 caused by such a heat pulse is schematically shown in Figure 1

[0130] The heat received by the measurement body 16 from the skin of the finger 12 causes a physical response, which can be detected in one of various possible detection devices, which are designed to generate a response signal based on the physical response, wherein the response signal is indicative of the degree of absorption of the excitation light. Various ways of detecting the physical response and generating an appropriate response signal will be described below.

[0131] However, regardless of the precise way in which the physical response is detected, it is noted that the maximum depth under the skin surface where absorption can be detected by means of the heat pulse that travels to the measurement body 16 is found to be limited to the thermal diffusion length of the skin t which is defined as

[0132]

[0133] and which depends on the density p, the specific heat capacity C p and the thermal conductivity k t of the material, as well as the modulation frequency f of the excitation light. In other words, by choosing the modulation frequency f, the depth at which any absorption of the excitation light is reflected in a heat pulse received at the measurement body 16 can be defined.

[0134] Referring again to Figure 1 , in the illustrated embodiment, the physical response to the absorbed heat received from the skin is a change in the refractive index in a region close to the surface 14 of the measurement body 16, in which region the heat gradient 20 temporarily forms. This local change in the refractive index forms something that can be seen as a thermal lens, which can be detected by means of a detection light beam 22. The detection light beam 22 passes through the thermal lens or heat gradient region 20 and is then reflected at the interface of the measurement body 16 and the skin of the finger 12. Each time a heat pulse is received from the skin, a local change in the refractive index occurs, and this causes the detection light beam 22 to be deflected due to the interaction with the measurement body material in the thermal lens region. In Figure 1 ​In this context, reference sign 22b corresponds to the detection beam 22 without deflection, while reference sign 22a corresponds to the detection beam when it is deflected due to the thermal lens formed in the thermal gradient region 20. This deflection can be measured and forms an example of the response signal described above. The degree of deflection is indicative of the received heat, and thus also of the degree of absorption of the excitation light in the skin of the finger 12. In this context, the "degree of deflection" can refer to the deflection angle, but more generally corresponds to any deviation between the detection beams that can be detected by the respective detection device.

[0135] Figure 3 A more detailed cross-sectional view of the apparatus 10 is shown, which relies on the measurement principle as described with reference to Figure 1 The apparatus 10 comprises a housing 24, which comprises the measurement body 16, with a top surface (contact surface) 14 on which the finger 12 is placed. Within the housing 24, an excitation light source 26 is provided, which generates an excitation light beam. In the shown embodiment, the excitation light source 26 comprises an array of quantum cascade lasers, each having a dedicated wavelength. For example, the array of quantum cascade lasers can comprise a single quantum cascade laser element, the wavelength of which corresponds to Figure 2 The shown absorption peaks and local minima (i.e. glucose characteristic wavelengths), as well as other wavelengths that can be used for reference measurements, or for detecting other substances that can interfere with the glucose measurement, such as lactate or albumin. The laser array can directly illuminate the excitation light beam into the measurement body 16 and through the measurement body 16, but it can also be illuminated into an optical waveguide (not shown), which couples the laser array with the measurement body and guides the excitation light beam to the measurement body 16 in a curved or non-curved manner. In case the excitation light beam is generated by a single tunable laser, an optical waveguide can also be used.

[0136] The device 10 further comprises a light source 28, e.g. a laser, for emitting a detection light beam 22, and a position sensitive detector 30 allowing to detect a deflection of the detection light beam 22, which allows to detect a deflection of the detection light beam 22. Note that the term "light beam" as understood in the present context is not limited to light in the visible range, although in a preferred embodiment the detection light beam 22 will indeed be in the visible spectral range. In this case, the measurement body 16 is transparent to both the excitation light beam and the detection light beam 22. In addition, a camera 32 or other imaging device is provided, which allows to capture an image of the contact surface 14 of the optical medium in a direction from inside the measurement body 16 to the finger 12, to thereby record a fingerprint of the finger 12 placed on the contact surface 14. This fingerprint can be processed by a control unit 34, such as to identify a user via his or her fingerprint. The control unit 34 is also used to control the light sources 26 and 28 for the excitation light and the detection light, respectively, and the sensor 30. The control unit 34 is also in wireless connection with an external data processing device 36 for exchanging data. For example, via the wireless connection, the control unit 34 can retrieve user-specific calibration data via a user identified via a fingerprint. The control unit 34 and the external data processing device 36 together form an example of a "control system" as referred to herein. The control system can consist of one or more processors, microcontrollers, computers, ASICs, FPGAs, etc. As Figure 3 indicated, the control system can be distributed, with various components in data communication with each other, or can be formed by a single control unit, like the control unit 34, which would be designed for all control functions described herein. The control system can generally be implemented in hardware, software, or a combination of both.

[0137] As further visible in Figure 3 , the excitation light source 26 and the detection light source 28 as well as the position sensitive detector 30 are all attached to a common carrier structure 38. This means that these components can be precisely pre-assembled on this structure 38, so that no separate adjustment or calibration thereof is required when assembling the device 10. One or more of the excitation light source 26 and / or the detection light source 28 as well as the position sensitive detector 30 can also be mounted directly on the measurement body 16, to avoid additional adjustment or calibration.

[0138] In addition, the device 10 comprises a corneometer 40, which allows to measure the water content of the skin. Corneometers for measuring the water content in the upper layers of the skin are known per se in the art and do not need to be described in detail herein. For example, known corneometers use two interdigitated electrodes to which an AC voltage is applied to measure the impedance, in particular the capacitive impedance, of the skin. When the fingertip 12 is resting on the contact surface 14 of the measurement body 16, Figure 3 the corneometer 40 is in contact with the fingertip 12.

[0139] The device also includes a pH sensor 42 for measuring the pH value of the skin. pH sensors for measuring the pH value of surfaces, including the skin, are known in the prior art and do not require detailed description herein. pH sensors for measuring skin pH values ​​are commercially available for medical purposes but can also be used for cosmetic purposes.

[0140] Figure 4 Showing the use of Figure 3 The results of Clarke error grid analysis obtained by the device of the type shown illustrate that by referring to Figures 1-3 The measurement procedure described can indeed measure blood glucose concentration in a completely non-invasive manner with high reliability. Figure 4 The data shown is taken from WO 2017 / 09782 A1 and does not yet reflect the improvements of this application. This application allows for, and even further improves, the reliability of the method, as described below.

[0141] Figure 5 The device 10 is schematically shown, which depends on and Figure 1 and Figure 3 The same general principle applies to absorbing thermal pulses received by the measuring body 16 from the material 12, but the difference lies in the physical response utilized and the manner in which the corresponding response signal is generated. Such a device 10 and its numerous variations are described in detail in WO 2019 / 11059782, which is incorporated herein by reference, so that a detailed description may be omitted herein. As previously described, the device includes a measuring body 16 having a contact surface 14 that contacts or couples with the skin of the finger 12. Furthermore, a source 26 with a modulated excitation beam is provided, which is irradiated into and absorbed in a region 44 beneath the surface of the skin 12. In this embodiment, the excitation beam passes through an aperture 46 in the measuring body 16, indicated by a dashed line passing through the measuring body 16, such that the material of the measuring body 16 itself does not need to be permeable to it.

[0142] A control unit 48 is provided for modulating the intensity of the excitation beam. This can typically be achieved in various ways, including using a mechanical chopper or an element with electronically controllable transmittance or reflectivity. However, in a preferred embodiment, the intensity is modulated by modulating the on / off time of the excitation source 26 and the operating current during its on time.

[0143] The thermal wave (symbolically represented by arrows 50) caused by the time-varying absorption of the intensity-modulated excitation light beam in the region 44 of the skin 12 enters the measuring body 16, in which it can be detected in a detection region 52 having piezoelectric properties. The pressure variations associated with the received thermal 50 or pressure wave cause an electrical signal in the form of a voltage variation that can be recorded with the electrodes 6a-6d, which are connected via conductive leads 54 with an evaluation device 56 for the analyzed material (the skin of the finger 12), which can be a digital processing device, such as a microcontroller or a processor or a computer. In this case, the variations in pressure are similar to the physical response of the measuring body 16 or other components included therein to the heat received from the material 12 after the absorption of the excitation radiation, which is detected using the piezoelectric properties of the measuring body 16 or a portion thereof or a piezoelectric element embedded in the measuring body and the electrodes 6a-6d, and which causes an electrical signal that generates a response signal indicative of the degree of absorption of the excitation radiation 18.

[0144] In an alternative variant proposed by the present applicant, as disclosed, for example, in the international application PCT / EP2019 / 064356 included by reference herein, the detection device can comprise an interferometric measurement device, which can be embedded in the measuring body, and which allows to evaluate said variations in phase of a first portion of the detection light beam with respect to a second portion of the light beam detected, in which only one portion of the detection light beam of the measurement arm is affected by the effects of the thermal or pressure wave in the measuring body and generates, on the output side of the interferometric measurement device, a response signal indicative of said variations in phase in the measurement arm. In this case, the physical response of the measuring body 16 (or components included therein) to the heat received from the material 12 after the absorption of said excitation radiation 18 is again a local variation in the refractive index, while in this case the response signal is an interference signal that reflects the phase variations of a portion of the detection light beam due to the local variations in the refractive index. This is schematically illustrated in Figure 6 , in which it is shown that the measuring body 16 (such as a finger, Figure 6In this case, the measurement body 16 can be a silicon substrate in which a light guiding structure 58 is provided, which forms an interferometric measurement device 60. The interferometric measurement device 60 forms a Mach-Zehnder interferometer, which has a measurement arm 60a and a reference arm 60b. The detection light generated by the detection light source 28 is fed into the light guiding structure 58 and split by a beam splitter 60c into a part or portion of the detection beam that travels along the measurement arm 60a and a part or portion of the detection beam that travels along the reference arm 60b, which are then combined by a beam combiner 60d. The measurement body 16 is used or arranged such that the reference arm 60a is exposed to heat received from the skin after absorption of the excitation light, and not, or at least to a much smaller extent, the reference arm 60b. Due to the received heat, the refractive index in the measurement arm 60a will change, which in turn causes a phase shift of the detection light traveling along the measurement arm 60a. Since the light traveling along the reference arm 60b is not affected by the received heat, the relative phase of the two parts of the light combined by the beam combiner 60d will change, which results in an interference pattern that can be detected using a detector 62. It should be noted that Figure 3 The camera for detecting and analyzing a fingerprint shown in Figure 5 and 6 can also be combined with the measurement body 16 and the device shown in

[0145] Figure 7 A schematic representation of the device 10 according to an embodiment is shown in a side cross-sectional view. Figure 8 A front cross-sectional view of the same device 10 is shown. In Figure 7 and 8 In the embodiment shown in Figure 7 and Figure 8 The embodiment of Figure 7 and 8 The measurement body 16 shown in Figure 7 and 8 The bottom surface shown in

[0146] The measurement body 16 also has an entrance surface 72 for the detection beam 22, which is Figure 7In the illustration, the incident surface 72 corresponds to the left side wall, and the exit surface 74 corresponds to the right side wall. A focusing lens 76 and a collimating lens 78 are integrally formed with the incident surface 72 and exit surface 74, respectively. In the illustrated embodiment, the focusing and collimating lenses 76 and 78 are integrally formed with the rest of the measuring body 16. In other embodiments, the focusing and collimating lenses 76 and 78 may be formed separately from the measuring body 16, but may be attached to the incident surface 70 and exit surface 74 respectively, so that they do not require separate adjustment.

[0147] Furthermore, a protrusion 80 is formed on the contact surface 14 of the measuring body 16. The protrusion 80 has a front surface 82 that contacts the skin of the finger 12, and through this front surface 82, excitation radiation 18 formed by an excitation beam in the mid-infrared range is radiated into the skin. The protrusion 80 has four sidewalls 84, each gradually narrowing towards the front surface 82. In this way, the area of ​​the front surface 82 is smaller than the area of ​​the footprint of the protrusion 80 on the contact surface 14. (As from...) Figure 7 and 8 The comparison shows that protrusion 80 is ridge-shaped, in the first direction, that is, located... Figure 7 It has a longer extension in the x-direction of the paper, and in the second direction perpendicular to the first direction, i.e., located in... Figure 8 There is a shorter extension in the y direction on the paper.

[0148] Finally, a pressure sensor 86 is disposed on the contact surface 14, which measures the contact pressure between the finger 12 and the contact surface 14. The pressure sensor 86 is connected to the control system, such as... Figure 3 Control unit 34 (not shown).

[0149] Next, we will explain Figure 7 and 8 The functions of the various features shown. For example... Figure 7 As shown, the incident surface 70 of the excitation radiation 18 is not parallel to the contact surface 14 or the front surface 82 of the protrusion 80. Instead, the measuring body is slightly wedge-shaped. Furthermore, the excitation source 26 is arranged such that the excitation beam strikes the incident surface at an angle deviating from 90°.

[0150] This is similar to, for example Figure 3 The arrangements shown are different. Figure 3The excitation light beam is intentionally made to impinge on the entrance surface at an angle of 90°, such as to avoid refraction and excessive reflection of the excitation radiation beam at the entrance surface. However, as explained above, with this arrangement, part of the excitation radiation 18 will be reflected from the entrance surface 70 and can interfere with the excitation radiation 18 emitted from the excitation radiation source 26. The inventors found that this interference can cause fluctuations in the intensity of the excitation radiation 18 in the skin of the finger 12, resulting in artificial variations in the response signal that are completely unrelated to the analyte concentration. However, when the normal incidence of the excitation light beam on the entrance surface 70 is avoided, the interference between the entrance radiation and the reflected radiation 18' can be suppressed and the accuracy and reliability of the overall measurement can be improved. Figure 7 The interference between the entrance radiation and the reflected radiation 18' is illustrated and the accuracy and reliability of the overall measurement can be improved.

[0151] In a preferred embodiment, the angle of incidence should deviate from 90° only by a few degrees, if at all. A favorable angle of incidence can be 89.0° or less, preferably 88.0° or less, and more preferably 87.5° or less. The optimal choice of angle will also depend on the distance between the excitation radiation source 26 and the entrance surface 70. The deviation from 90° should not be chosen larger than necessary to reliably avoid the undesired interference effect. In a preferred embodiment, the angle of incidence is thus 82.0° or more, preferably 84.0° or more, and most preferably 85.0° or more.

[0152] The protrusion 80 has the special technical effect of increasing the local contact pressure between the finger 12 and the measurement body 16. More precisely, the increased contact pressure occurs at the front surface 82 of the protrusion 80, which is where the excitation light beam is coupled from the measurement body 16 into the skin of the finger 12. This increased contact pressure allows to ensure a good and reliable optical coupling between the measurement body 14 and the skin.

[0153] The significant improvement that can be obtained with this protrusion 80 came as a surprise to the inventors, as generally, in the applicant's previous devices, sufficient optical coupling was obtained with a completely flat contact surface 14, so that the additional manufacturing costs and increased complexity involved in providing the protrusion 80 did not appear to be justified.

[0154] However, the inventors found that, although optical coupling with a completely flat contact surface 14 generally appears to be satisfactory, particularly inconsistent or unstable optical coupling can be a source of measurement inaccuracies. As explained in the above summary, the inventors noticed that the optical coupling can change during a single measurement, i.e. without the fingertip being intentionally moved onto or even off the contact surface. In some cases, this was found to result in a change in the intensity of the excitation radiation that is actually absorbed by the analyte, and thus in a change in the response signal that is not related to the absorption rate of the analyte at the excitation radiation wavelength or the analyte concentration. In other words, a loss of light coupling during part of the measurement can be misinterpreted as a decrease in the absorption rate at a given excitation wavelength. As explained above, the evaluation of the analyte spectrum typically involves measuring the absorption at a plurality of characteristic wavelengths, e.g. wavelengths corresponding to peaks or local absorption minima of the analyte absorption spectrum, and also involves a mathematical combination of the response signals associated with the different wavelengths. For example, the response signal obtained at a local minimum of the absorption spectrum can be subtracted from the response signal of an absorption peak to give a value representative of the glucose concentration in the skin. Obviously, any change in the light coupling in the material, and thus in the effective intensity of the excitation radiation, between measurements at different wavelengths, or even during a measurement at a particular wavelength, can lead to artefacts or inaccuracies in the measurement results.

[0155] As explained in the summary of the present application, it is not entirely clear why the optical coupling between the contact surface and the material should change during a measurement, e.g. because the user fails to keep the contact pressure between the fingertip and the contact surface constant, or the user inadvertently moves the fingertip on the contact surface. Regardless of the specific underlying cause, the inventors noticed that using a protrusion 80 such as shown in Figs. 8A and 8B, with a front surface 82 that comes into contact with the skin of the fingertip 12, where the local contact pressure is increased, can significantly stabilize the optical contact. The front surface can have a size of less than 5 mm2, in particular less than 3 mm2, and can be flat or curved in a concave or convex manner. Figure 7 and 8 The front surface 82 can have a size of less than 5 mm2, in particular less than 3 mm2, and can be flat or curved in a concave or convex manner.

[0156] To further ensure a constant contact pressure during the measurement, a pressure sensor 86 is provided. The pressure sensor 86 generates a signal indicative of the contact pressure between the finger 12 and the contact surface 14 of the measurement body 16. This signal is transmitted to a control system (not shown) which is configured to check whether the sensed contact pressure is below a predetermined threshold. If this is found to be the case, the user is indicated of this by means of a suitable output device, such as a display, a light signal, an acoustic signal, etc., so that the user can be prompted to increase the contact pressure. Furthermore, the control system is configured to prevent the analyte measurement process from starting when the contact pressure is below the threshold, so that a measurement to be performed with doubtful quality and possibly having to be repeated is avoided, which can lead to user impatience or frustration. Moreover, if during the measurement it is found that the contact pressure drops below the threshold, the analyte measurement process is interrupted, again giving the user the opportunity to restore the original contact pressure so that the measurement can be completed. The pressure sensor can also be located underneath the protrusion 80 in the measurement body 16 and be implemented as a piezoelectric element (not shown) which is transparent to the excitation light beam.

[0157] It is noted that each of the features and functions explained so far with reference to Figure 7 relate to reliably coupling a consistent amount of excitation radiation into the skin of the finger 12 and are thus independent of the specific type of physical response of the measurement body (or components included therein) to the thermal or pressure waves received from the skin of the finger 12 or the detection device generating the respective response signal. Thus, these features can be used in combination with any of the variants shown in Figure 1 , 3 , 5 and 6.

[0158] In embodiments of Figure 7 , the physical response to the thermal or pressure waves received by the measurement body 16 is a local change in refractive index and this physical response is detected via a deflection of the detection light beam 22 reflected at the front surface 82 of the protrusion 84. As shown in Figure 7 , the detection light beam 22 is generated by a detection light source 28 and the deflection of the detection light beam 22 is detected using a position sensitive detector (PSD) 30 (which can also be referred to as a position sensitive device). As understood herein, the “deflection of the detection light beam 22” denotes the total deviation of the detection light beam at the respective detection device and, with reference to Figure 7 embodiments, it denotes a positional deviation of the detection light beam 22 on the PSD 30. This deviation is a combined effect of all changes in the propagation of the detection light beam 22 along its optical path caused by the local change in refractive index.

[0159] Figure 7 The specific ridge-shaped geometry of the protrusion 80 shown in Figure 8 has been adapted to this detection setup. The detection light beam 22 before and after reflection at the front surface 82 of the protrusion 80 defines a detection light plane, which is perpendicular to the optical axis of the detection light beam 22.Figure 7 and Figure 8 In the implementation scheme, the detection light plane corresponds to the xz plane, i.e. Figure 7 The paper surface, and the position of the detection surface is aligned with the first elongated direction of the ridge protrusion 80. In fact, as from... Figure 7 Clearly visible, this significant extension of the protrusion 80 in the detection light plane is necessary to allow the incident and reflected detection beam 22 to conform into the protrusion 80. Conversely, as from... Figure 8 It is clearly visible that, in the direction perpendicular to the detection light plane, i.e., in the "second direction" of the ridge protrusion 80, the extension can be made much smaller, thereby keeping the surface area of ​​the front surface 82 as a whole smaller and thus increasing the local contact pressure.

[0160] Furthermore, the focusing lens 76 at the incident surface 72 of the detection beam 22 allows the diameter of the detection beam to remain narrow in the area reflected on the front surface 82 of the protrusion 80, which is also where a thermal lens will form. Figure 7 (Not shown in the image). The narrow beam diameter facilitates the clarity and characteristic deflection of the detection beam 22 at the thermal lens, which itself has a relatively small size.

[0161] The collimating lens 78 at the exit surface 74 of the detection beam 22 allows the diameter of the detection beam 22 to remain at least nearly constant during its travel between the exit surface 72 and the PSD 30. This means that any deflection angle obtained by the detection beam 20 will result in a significant shift in the position where the detection beam 22 strikes the PSD 30, thereby increasing the signal-to-noise ratio of the response signal. For example, the distance between the reflective portion at the front surface 82 of the protrusion 80 and the PSD 30 can be 4 cm or more, and in some embodiments even 9 cm or more.

[0162] exist Figure 7 In the illustrated embodiment, both the focusing lens 76 and the collimating lens 78 are shown as spherical lenses with focusing and collimating effects in both principal directions. However, in other embodiments, particularly the collimating lens 78, it may be a cylindrical lens, which only... Figure 7 It has a collimation effect in the y-direction, and with Figure 7 The difference shown is that the detection beam 20 can be in the xz plane, i.e. Figure 7 The light spot is unfolded on the paper. This means that the spot of the detection beam 22 on the PSD 30 will be elliptical, with the longer diameter parallel to the sensing direction of the PSD 30, which is also the direction in which the light spot moves after the detection beam 20 is deflected. This elongated shape of the light spot has also been found to result in a better signal-to-noise ratio and better linearity of the response signal.

[0163] As understood herein, the "deflection" of the detection beam 20 relates to the total deviation of the detection beam 20 from its "unperturbed" optical path, i.e. in the absence of local variations of the refractive index due to thermal or pressure waves received by the measurement body 16, as measured by a detection device such as the PSD 30. This "deflection" is thus the cumulative effect of local variations of the refractive index on the detection beam 20 along its optical path. In practice, the deflection is always intended to be small, and in order to obtain more accurate and reliable measurement results, it is important to improve the signal-to-noise ratio of the response signal. A possible approach has been explained above, i.e. by increasing the distance between the exit surface 74 and the PSD 30. Other approaches to improve the signal-to-noise ratio will be discussed below with reference to Figure 7 Figure 7

[0164] Without wishing to be bound by theory, Figures 9-11 shows the deflection mechanism as presently understood by the inventors, which is fully consistent with the actual measurements. In Figure 9 , the unperturbed detection beam is shown in solid line, with an incident portion and an exit portion 22b. When the excitation radiation pulse is absorbed by the skin, as explained above, a thermal pulse is generated, which travels through the skin and into the measurement body 16, where it causes a local variation of the refractive index, which is referred to herein as a "thermal lens", and is shown schematically in Figure 9 at reference sign 20 in Figure 12 . In this embodiment, the thermal lens 20 is found to be a region of increased refractive index, which leads to refraction as shown by the dashed refracted and reflected detection beam 20a. The deviation of the reflected detection beam 22a from the unperturbed reflected detection beam 22b is referred to herein as the "deflection".

[0165] Note that in Figure 9 , the entrance surface 72 and the exit surface 74 of the measurement body 16 are angled so as to form a right angle with the incident and exit detection beams 22. This orthogonal arrangement of the optical boundaries is a natural choice in the art, as it allows to reduce reflections and also avoid diffraction, which would complicate the optical setup. However, in the embodiment of Figure 9 , at least the exit surface 74 is arranged such as not to be perpendicular to the reflected detection beam 22b. Instead, the detection beam 22b forms an angle a1 with the normal to the exit surface 74, such that the unperturbed detection beam 22b is refracted when exiting the measurement body 16 at an angle b1 larger than a1, because the refractive index of the measurement body 16 is higher than the surrounding refractive index, which in the present embodiment is air.

[0166] The deflected beam 22a is likewise refracted at the exit surface 74. However, due to the interaction with the thermal lens 20, the angle of incidence a 2 ​​The refracted beam 22b is larger than the unaffected detection beam, and according to Snell's law, the refraction angle β2 is significantly larger than β1. In other words, the difference between the refraction angles β2 - β1 is greater than the difference between the incident angles α2 - α1, i.e., β2 - β1 > α2 - α1, thus increasing the refraction angle through PSD 30 ( Figure 10 (Not shown in the image) The deflection of the reflected detection beam 22a is measured. This allows for a further increase in the signal-to-noise ratio.

[0167] Finally, refer to Figure 10 The image shows an embodiment in which the contact surface 14 of the measuring body 16 is curved in the region where the detection beam 22 is reflected. In other words, the measuring body in this region has a concave, curved recess. Figure 11 As schematically illustrated, due to local variations in refractive index, partial deflection of the beam occurs before the detection beam 22 is reflected at the surface of the measuring body in thermal or pressure-transmitting contact with the finger 12. This means that local variations in refractive index also cause a shift in the precise position at which the detection beam 22 is reflected on the surface.

[0168] Given this understanding, in Figure 11 In the illustrated embodiment, the contact surface 14 has a curved portion 88. Due to this curvature, the change in the precise position of the detection beam 22 reflected on the curved portion 88 is accompanied by a change in the angle of incidence, and thus also results in a corresponding change in the reflection angle, such as... Figure 11 This is visible in the image. Therefore, using a curved reflective surface can increase the total deflection assessed by the detection device, such as the positional offset of the impact detection beam 22 detected by the position-sensitive detector 30, thereby further allowing for an increase in the signal-to-noise ratio. Note that in Figure 11 In the diagram, the curved portion 88 is shown as being formed in the otherwise flat contact surface 14, but the curved portion can also be formed in... Figure 11 and Figure 7 In the front surface 82 of the protrusion 80 shown. Furthermore, although in Figure 8 In the embodiment shown, the curved portion 88 is concave, but a similar effect can also be achieved using a convex curved portion (not shown), because in this case, the local change in refractive index will also be accompanied by a change in the position where the detection beam strikes the curved portion, and therefore also by a change in the incident angle.

[0169] In addition, Figure 11In particular, the curved portion 88 is shown to have a spherical shape, i.e. to be curved in both main directions with the same or similar curvature. However, in other embodiments, the curved portion 88 can be curved mainly or even exclusively in only one direction, e.g. having the cross-sectional shape of a cylinder (cross-sectional plane parallel to the cylinder axis). This is particularly advantageous in the case of a concave curved portion 88, in which case the finger 12 can be placed parallel to the longitudinal axis of the concave curved portion, thereby allowing particularly good contact on the curved surface of the curved portion. As mentioned above, in preferred embodiments, the radius of the curved portion 88 in at least one main direction ranges from 5 to 30 mm, more preferably from 10 to 20 mm. In preferred embodiments, the curved region 88 has a width in the main direction of at least 300 pm and at most twice the radius of the curvature.

[0170] As mentioned above, in many embodiments, it is advantageous if the light spot of the detection beam 22 on the PSD 30 has an elongated shape, e.g. and an elliptical shape, with the long axis parallel to the detection direction. For example, such an elongated shape can be obtained by collimating the detection beam 22 only in a direction perpendicular to the detection direction, as explained above with reference to Figure 11 However, additionally or alternatively, the elongated shape of the light spot can be obtained by tilting the PSD 30 with respect to the detection beam 22 in the detection light plane, as Figure 7 shown, so that it hits the PSD 30 at an angle deviating from 90°. For example, the angle of incidence onto the detection surface of the PSD 30 can be less than 80°, preferably less than 70°, and most preferably less than 50°.

[0171] Figure 12 and Figure 13 shows another device 10 similar to Figure 14 the device of Figure 7 , the device of Figure 7 and Figure 13 comprises a detection beam 22 reflected on the contact surface 14 of the measurement body 16 and a detection device, such as a PSD 30, allowing to detect a deflection of the detection beam 22 due to the interaction with the thermal lens indicated at the reference mark 20. In Figure 14 and 14In an embodiment, the detection beam 22 is derived from the source beam 88 by means of a beam splitter 90. The beam splitter 92 transmits a portion of the source beam 88 forming the detection beam 22, and reflects another portion forming a reference beam 92. Using a mirror 94, the reference beam 92 is likewise directed to be fully or partially reflected at the surface 14 of the measurement body 16 at a location close to the reflection location of the detection beam 22, and in particular in the area where the finger 12 (not shown) under operation will contact the contact surface 14. However, the reflection point of the reference beam 92 on the contact surface (or more precisely at the interface between the contact surface 14 and the material, i.e. the finger 12) is sufficiently far away from the area where the excitation beam is absorbed, such that any influence of the heat or pressure waves received from the finger 12 after absorption of the excitation radiation 18 is negligible. This is illustrated in Figure 13 and 14 where it can be seen that the thermal lens 20 does not extend to the area where the reference beam 92 is reflected on the contact surface 14 of the measurement body 16.

[0172] In Figure 13 the reference marks 93 indicate the points of entry and exit of the detection beam 22 and the reference beam 92 into and out of the measurement body 16, and are shown primarily to aid in imaging the three-dimensional structure. Note that in the schematic illustration of Figure 14 the detection beam 22 and the reference beam 92 are not shown refracted at the entry and exit surfaces for simplicity. A further detector 96 is provided for detecting the deflection of the reference beam 92, and in the illustrated embodiment it is formed by a PSD of the same type as the PSD 30.

[0173] It can be seen that the reference beam 92 will be exposed to all or almost all of the same types of noise, vibrations, disturbances or external influences as the detection beam 22, except for the influence of the thermal lens 20, or in other words the heat or pressure waves received due to absorption of the excitation beam. Thus, all or at least a large proportion of the types of external influences that can cause deflection of the detection beam 22, except for those due to absorption in the material, will also affect the reference beam 92, and can be measured by the further detector 96. The measurements of the further detector relative to the reference beam 92 can then be used to correct the measurements of the PSD 30 relative to the detection beam 22 for these influences, in order to thereby improve the quality of the measurement signal.

[0174] Reference Figure 14 and Figure 15, another embodiment of the device is shown, which comprises an optical fiber 98 embedded in the measurement body 16. At one end of the fiber 98 a detection light source 28 is provided for coupling detection light into the fiber 98. At the other end of the fiber 98 a mode detector 100 is provided. The mode detector 100 is adapted to detect a change in the optical mode of the detection light in response to thermal and pressure waves received by the measurement body 16 from the material. For example, the mode detector 100 can comprise a camera adapted to visualize the mode, and more precisely, the interference pattern of the optical mode. In Figure 16 the right-hand side, an image generated by such a mode camera is shown schematically, in which the optical mode 104 can be seen in a certain rotational direction, and more precisely, the interference pattern of the optical mode.

[0175] Figure 15 The same device as in Figure 16 is shown, in which, however, a thermal gradient 20 is formed due to thermal or pressure waves received from the material such as a finger 12 (not shown in Figure 15 and 16 ). This will lead to a transient deformation of the optical fiber 98, as shown in the enlarged portion of Figure 15 , in which the deformation is highly exaggerated for illustrative purposes. This transient deformation of the optical fiber 98 will lead to a change in the optical mode detected by the mode camera 100. In the exemplary embodiment shown in Figure 16 , the change in the mode corresponds to a rotation of the interference pattern of the mode, as can be seen by the comparison of the mode images shown schematically in Figure 16 and Figure 15 . In other embodiments, the change in the mode can for example correspond to a shift of the interference pattern of the mode.

[0176] In the embodiment shown, the mode detector 100 comprises a processor (not shown separately) configured for detecting the change in the mode based on image analysis of the camera images. As mentioned above, the detectable change in the optical mode can comprise a shift or a rotation of the interference pattern of the optical mode within the fiber and on the mode camera 100. The shift distance or the rotation angle is thus a quantitative parameter related to the intensity of the thermal or pressure waves received from the material and thus ultimately indicative of the amount of excitation light absorbed by the material. Figure 16 and Figure 15 The device has the advantage that it is very simple, robust, and requires hardly any adjustment of the optical components. It is particularly suitable for a portable device.

[0177] Figure 16 A side view and a perspective view of a device 10 according to another embodiment are shown. The device 10 is a portable glucose measurement apparatus having dimensions similar to a small smartphone. In Figure 17The top view shows a measuring body 16 with a contact surface 14, in which the measuring body has a contact surface 14 with the contact surface 14. Figure 17 Similar curved sections. On contact surface 14, it is possible to... Figure 11 The finger 12 is positioned as shown, where the finger 12 is schematically represented only by a cylindrical structure. Although Figure 17 and 17 Other details of the device are not shown, but the measurement principle of the device is similar to... Figure 16 Similarly, a detection beam reflected on a curved surface (not shown) is used. See reference... Figure 11 This explains why the measurement beam is deflected particularly large, and therefore the signal-to-noise ratio is particularly high.

[0178] Figure 11 The clamping device 106 is further shown, including a clamping member 108. The clamping member 108 is pivotally mounted at a first end (left end in the figure) and biased by a torsion spring 114. Figure 17 In the closed position shown in the top view, the clamping member 108 is close to the contact surface 14. At the second end of the clamping member 108, a handle member 110 is provided, which allows the clamping member 108 to be gripped and rotated against the biasing force of the torsion spring 114 to the open position, wherein the clamping member 108 moves away from the contact surface 14 of the measuring body 16. When the clamping member 108 is in the open position, the finger 12 can be placed on the contact surface 14, and the clamping member 108 is adapted to press the finger 12 against the contact surface 14 due to the biasing force toward the closed position. This ensures a predetermined contact pressure. A pad 112 is formed near the second end of the clamping member 108 when the finger 12 is clamped by the clamping member 108. Figure 17 When held in the manner shown, the pad 112 rests against the finger 12. In the illustrated embodiment, a pressure sensor (not shown) is provided in the pad 112 to interact with... Figure 17 Figure 7 The pressure sensor 86 shown monitors contact pressure in a similar manner. Note that the clamping mechanism is not limited to use in handheld devices, but can also be installed, for example, in desktop devices or any other variant. Furthermore, the biasing force of the clamping member 108 does not need to be generated by a torsion spring such as torsion spring 114, but can also be provided by the clamping member 108 acting as a leaf spring. Instead of torsion spring 114, there can be an adjustable support that allows adjustment of the rest position of the clamping member 108 (leaf spring), and thus the resulting biasing force.

[0179] This document further discloses the following embodiments:

[0180] Example 1:

[0181] Device for analyzing a material comprising at least one analyte, the device comprising:

[0182] a measurement body having a contact surface adapted for being in thermal or pressure-transmitting contact with the material, the thermal or pressure-transmitting contact allowing thermal or pressure waves generated by an excitation radiation absorbed in the material to be transmitted to the measurement body,

[0183] an excitation radiation source configured for irradiating excitation radiation into the material for absorption therein, and

[0184] a detection apparatus for detecting a physical response of the measurement body or a component comprised therein to thermal or pressure waves received from the material after absorption of the excitation radiation, and for generating a response signal based on the detected physical response, the response signal being indicative of the degree of absorption of the excitation radiation, wherein a pressure sensor is provided for measuring a contact pressure between the material and the measurement body.

[0185] In a preferred embodiment of embodiment 1, the device further comprises a control system configured for receiving a signal from the pressure sensor indicative of the contact pressure between the material and the measurement body, wherein the control system is configured to check whether the contact pressure is below a predetermined threshold value, and in case the contact pressure is found to be below the threshold value, one or more of the following is performed:

[0186] indicating to a user the lack of contact pressure,

[0187] preventing the analyte measurement process from starting, and

[0188] interrupting a current analyte measurement process.

[0189] Embodiment 2:

[0190] Device for analyzing a material comprising at least one analyte, the device comprising:

[0191] a measurement body having a contact surface adapted for being in thermal or pressure-transmitting contact with the material, the thermal or pressure-transmitting contact allowing thermal or pressure waves generated by an excitation radiation absorbed in the material to be transmitted to the measurement body,

[0192] an excitation radiation source configured for irradiating excitation radiation into the material for absorption therein, and

[0193] a detection apparatus for detecting a physical response of the measurement body or a component comprised therein to thermal or pressure waves received from the material after absorption of the excitation radiation, and for generating a response signal based on the detected physical response, the response signal being indicative of the degree of absorption of the excitation radiation,

[0194] wherein the measurement body is transmissive for the excitation radiation,

[0195] wherein the excitation radiation source is configured for providing the excitation radiation as an excitation light beam, and

[0196] wherein the excitation radiation source is arranged such that the excitation light beam is irradiated into the measurement body at an entry surface, propagates through a portion of the measurement body, and exits the measurement body at a contact surface,

[0197] wherein the excitation light beam impinges on the entry surface under an angle of 89.0° or less, preferably 88.0° or less, and most preferably 87.5° or less, and 82.0° or more, preferably 84.0° or more, and most preferably 85.0° or more.

[0198] In a preferred embodiment of embodiment 2, the excitation light beam impinges on the surface of the measurement body under an angle of 90° ± 1.5°.

[0199] In a preferred embodiment of embodiment 2, the entry surface and the contact surface are inclined relative to each other under an angle of 1.0° or more, preferably 2.0° or more, and most preferably 2.5° or more, and 8.0° or less, preferably 6.0° or less, and most preferably 5.0° or less, at their respective portions where the excitation light beam enters and exits the measurement body, respectively.

[0200] Embodiment 3:

[0201] A device for analyzing a material comprising at least one analyte, the device comprising:

[0202] a measurement body having a contact surface adapted for being in thermal or pressure transfer contact with the material, the thermal or pressure transfer contact allowing a heat or pressure wave generated by excitation radiation absorbed in the material to be transferred to the measurement body,

[0203] an excitation radiation source configured for irradiating excitation radiation into the material for absorption therein, and

[0204] a detection light source for generating a detection light beam traveling through at least a portion of the measurement body or a component comprised in the measurement body, wherein the detection light beam is directed to be fully or partially reflected at the contact surface, wherein the detection light beam is deflected in response to the heat or pressure wave generated by the excitation radiation absorbed in the material being transferred to the measurement body, and

[0205] a detector for detecting a degree of deflection, in particular an angle of deflection, of the detection light beam after its reflection at the contact surface,

[0206] wherein the detection light source is arranged such that the detection light beam is irradiated into the measurement body at an entry surface, propagates through a portion of the measurement body, and exits the measurement body at an exit surface,

[0207] wherein the detection light beam impinges on the exit surface at an angle of 5° or more, preferably 10° or more, and most preferably 15° or more, relative to a normal of the exit surface, such that the detection light beam is refracted after leaving the measuring body from an unintended surface, wherein the exit surface is relative to the direction of the detection light beam such that said deflection of the detection light beam increases said angle of the detection light beam to the normal of the exit surface in response to said thermal or pressure wave transmitted to said measuring body.

[0208] Embodiment 4:

[0209] A device for analyzing a material comprising at least one analyte, the device comprising a measuring body having a contact surface adapted for being in thermal or pressure transmission contact with the material, the thermal or pressure transmission contact allowing thermal or pressure waves generated by absorbed excitation radiation in the material to be transmitted to the measuring body,

[0210] an excitation radiation source configured for irradiating excitation radiation into the material for absorption therein, and

[0211] a detection light source for generating a detection light beam traveling through at least a portion of the measuring body or a component comprised in the measuring body, wherein the detection light beam is directed to be fully or partially reflected at the contact surface, wherein the detection light beam is deflected in response to thermal or pressure waves generated by absorbed excitation radiation in the material being transmitted to the measuring body, and

[0212] a detector for detecting a degree of deflection, in particular an angle of deflection, of the detection light beam after its reflection at the contact surface,

[0213] wherein the detection light source is arranged such that the detection light beam is irradiated into the measuring body at an entrance surface, propagates through a portion of the measuring body, and leaves the measuring body at an exit surface, wherein a focusing lens is attached to the entrance surface or integrally formed with the entrance surface for focusing the detection light beam, and / or a collimating lens is attached to the exit surface or integrally formed with the exit surface.

[0214] Embodiment 5:

[0215] A device for analyzing a material comprising at least one analyte, the device comprising:

[0216] a measuring body having a contact surface adapted for being in thermal or pressure transmission contact with the material, the thermal or pressure transmission contact allowing thermal or pressure waves generated by absorbed excitation radiation in the material to be transmitted to the measuring body,

[0217] an excitation radiation source configured for irradiating excitation radiation into the material for absorption therein, and

[0218] a detection light source for generating a detection light beam travelling through at least a portion of the measurement body or an assembly comprised in the measurement body, wherein the detection light beam is directed to be fully or partially reflected at the contact surface, wherein the detection light beam is deflected in response to a heat or pressure wave generated by the excitation radiation absorbed in the material being transmitted to the measurement body, and

[0219] a detector for detecting a degree of deflection, in particular an angle of deflection, of the detection light beam after its reflection at the contact surface,

[0220] wherein the detector comprises a position sensitive detector on which the detection light beam impinges, wherein the position sensitive detector is sensitive to a change in position of the detection light beam impinging thereon in at least one sensing direction, wherein the position sensitive detector is arranged such that the deflection of the detection light beam causes a change in position of the detection light beam impinging thereon in the at least one sensing direction, and wherein a cylindrical lens is arranged in the optical path of the detection light beam for shaping a profile of the detection light beam, and / or the position sensitive detector is arranged at an angle of 90° off the detection light beam such that a diameter of the detection light beam impinging on the position sensitive detector in the sensing direction is at least 1.5 times larger, preferably at least 2.0 times larger, than a diameter of the detection light beam in a direction perpendicular to the sensing direction.

[0221] In a preferred embodiment of embodiment 6, the cylindrical lens is a collimating lens arranged in the optical path of the detection light beam between its reflection at the contact surface and the position sensitive detector, wherein the cylindrical lens is arranged to collimate the detection light beam mainly in a dimension perpendicular to the sensing direction of the position sensitive detector, wherein the cylindrical collimating lens is preferably integrally formed with an exit surface of the measurement body at which the detection light beam exits the measurement body.

[0222] Embodiment 6:

[0223] A device for analyzing a material comprising at least one analyte, the device comprising:

[0224] a measurement body having a contact surface adapted for being in thermal or pressure transfer contact with the material, the thermal or pressure transfer contact allowing a heat or pressure wave generated by the excitation radiation absorbed in the material to be transmitted to the measurement body,

[0225] an excitation radiation source configured for irradiating excitation radiation into the material to be absorbed therein, and

[0226] a detection light source for generating a detection light beam travelling through at least a portion of the measurement body or an assembly comprised in the measurement body, wherein the detection light beam is directed to be fully or partially reflected at the contact surface, wherein the detection light beam is tilted in response to thermal or pressure waves generated by absorbed excitation radiation in the material being transmitted to the measurement body, and

[0227] a detector for detecting a degree of deflection, in particular an angle of deflection, of the detection light beam after its reflection at the contact surface, further comprising a beam splitter for splitting the light source beam into the detection light beam and a reference light beam, wherein the reference light beam is likewise directed at a surface of the measurement body being in thermal or pressure-transmitting contact with the material, but in a region where any influence of thermal or pressure waves received from the material upon absorption of excitation radiation is negligible, and wherein the detection device comprises a further detection device for detecting a degree of deflection, in particular an angle of deflection, of the reference light beam after its reflection at the contact surface, wherein the further detection device preferably comprises a photodetector, in particular a position sensitive photodetector

[0228] Embodiment 8:

[0229] A device for analyzing a material comprising at least one analyte, the device comprising:

[0230] a measurement body having a contact surface adapted for being in thermal or pressure-transmitting contact with the material, the thermal or pressure-transmitting contact allowing thermal or pressure waves generated by absorbed excitation radiation in the material to be transmitted to the measurement body,

[0231] an excitation radiation source configured for irradiating excitation radiation into the material for absorption therein, and

[0232] a detection device for detecting a physical response of the measurement body or an assembly comprised therein to thermal or pressure waves received from the material upon absorption of the excitation radiation, and for generating a response signal based on the detected physical response, the response signal being indicative of a degree of absorption of the excitation radiation, wherein the device comprises a fiber embedded in the measurement body, a detection light source disposed at one end of the fiber for coupling detection light into the fiber, and a mode detector disposed at the other end of the fiber, the mode detector being adapted to detect a change in an optical mode of the detection light in response to thermal or pressure waves received by the measurement body from the material, wherein the change in the optical mode preferably comprises a shift or a rotation of an interference pattern of the optical mode at the mode detector.

[0233] While this application has been described in terms of particular embodiments, it is to be understood that modifications and variations will occur to those skilled in the art, all of which are intended to be within the scope of this application. Thus, only those limitations that are present in the claims should be placed on the application.

Claims

1. An apparatus (10) for analyzing a material (12) comprising at least one analyte, the apparatus (10) comprising: The measuring body (16) has a contact surface (14) suitable for thermal or pressure transmission contact with the material (12), which allows heat waves or pressure waves generated by absorbing excitation radiation in the material (12) to be transmitted to the measuring body (16). An excitation radiation source (26) is configured to irradiate the material (12) with excitation radiation (18) for absorption therein, and A detection light source (28) is used to generate a detection beam (22) traveling through at least a portion of the measuring body (16) or a component included in the measuring body, wherein the detection beam (22) is guided to be totally or partially reflected at the contact surface (14), and wherein the detection beam (22) is deflected as a heat wave or pressure wave generated by absorbing excitation radiation in the material (12) is transmitted to the measuring body (16), and A detector is used to detect the degree of deflection of the detection beam (22) after it is reflected at the contact surface (14). The contact surface (14) of the measuring body is bent in at least one principal direction in the area where the detection beam (22) is reflected. The detection beam (22) before and after reflection at the contact surface (14) defines a detection light plane, wherein the main direction is located within the detection light plane or forms an angle of less than 30° with the detection light plane.

2. The apparatus (10) as claimed in claim 1, wherein, The curvature in at least one principal direction corresponds to a radius of curvature in the range of 5 to 30 mm.

3. The apparatus (10) as claimed in claim 1, wherein The detector is used to detect the deflection angle of the detection beam (22) after the detection beam (22) is reflected at the contact surface (14).

4. The apparatus (10) as claimed in claim 1, wherein, The curvature in the at least one principal direction corresponds to a radius of curvature in the range of 10 to 20 mm.

5. The apparatus (10) as claimed in claim 1 or 2, wherein, The curvature in the main direction is either concave or convex.

6. The apparatus (10) as claimed in claim 1 or 2, wherein the main direction is located within the detection light plane or forms an angle of less than 20° with the detection light plane.

7. The apparatus (10) as claimed in claim 1 or 2, wherein, The detection light source (28) is arranged such that the detection beam (22) is irradiated into the measuring body (16) at the first incident surface, propagates through a portion of the measuring body (16), and exits from the measuring body (16) at the exit surface (74). The detection beam (22) strikes the exit surface (74) at an angle of 5° or greater relative to the normal of the exit surface (74) without any deflection due to local changes in refractive index, such that the detection beam (22) is refracted as it exits the exit surface (74) of the measuring body (16), wherein the orientation of the exit surface (74) relative to the detection beam (22) causes the detection beam (22) to increase the angle of the detection beam relative to the normal of the exit surface in response to the deflection of the heat wave or pressure wave transmitted to the measuring body (16).

8. The apparatus (10) as claimed in claim 7, The detection beam (22) strikes the exit surface (74) at an angle of 10° or greater relative to the normal of the exit surface (74) without any deflection caused by local changes in refractive index.

9. The apparatus (10) as claimed in claim 7, The detection beam (22) strikes the exit surface (74) at an angle of 15° or greater relative to the normal of the exit surface (74) without any deflection caused by local changes in refractive index.

10. The apparatus (10) as claimed in claim 1 or 2, wherein, The detection light source (28) is arranged such that the detection beam (22) is irradiated into the measuring body (16) at a first incident surface, propagates through a portion of the measuring body (16), and exits from the measuring body (16) at an exit surface (74), wherein a focusing lens (76) is integrally formed with the first incident surface for focusing the detection beam (22) entering the measuring body (16) in at least one dimension, and / or a collimating lens (78) is integrally formed with the exit surface (74) for collimating the detection beam (22) in at least one dimension.

11. The apparatus (10) as claimed in claim 10, wherein, At least one of the focusing lens (76) and the collimating lens (78) is a cylindrical lens that focuses and collimates the detection beam (22) at least primarily in one dimension.

12. The apparatus (10) as claimed in claim 1 or 2, wherein, The detector includes a position-sensitive detector to which the detection beam (22) impacts, wherein the position-sensitive detector is sensitive to detecting positional offset of the detection beam (22) impacting the position-sensitive detector in at least one sensing direction. The position-sensitive detector is arranged such that the deflection of the detection beam (22) causes a shift in the position of the detection beam striking the position-sensitive detector in the at least one sensing direction, and A cylindrical lens is provided in the optical path of the detection beam (22) to shape the contour of the detection beam (22), and / or the position-sensitive detector is arranged at an angle deviating from the detection beam (22) by 90°, such that the diameter of the detection beam (22) striking the position-sensitive detector in the sensing direction is at least 1.5 times the diameter of the detection beam (22) in the direction orthogonal to the sensing direction.

13. The apparatus (10) as claimed in claim 12, The diameter of the detection beam (22) striking the position-sensitive detector in the sensing direction is at least 2.0 times the diameter of the detection beam (22) in a direction orthogonal to the sensing direction.

14. The apparatus (10) as claimed in claim 12, wherein, The cylindrical lens is a collimating lens (78) arranged in the optical path of the detection beam (22) between the reflection of the detection beam (22) at the contact surface (14) and the position-sensitive detector, wherein the cylindrical lens is arranged to collimate the detection beam (22) at least primarily in a dimension orthogonal to the sensing direction of the position-sensitive detector.

15. The apparatus (10) as claimed in claim 14, The cylindrical collimating lens is integrally formed with the exit surface (74) of the measuring body from which the detection beam (22) exits from the measuring body (16).

16. The apparatus (10) of claim 1 or 2, further comprising a beam splitter (90) for splitting the source beam into the detection beam (22) and a reference beam (92), wherein the reference beam (92) is also guided at a surface (14) of the measuring body (16) in thermal or pressure-transmitting contact with the material (12), but is totally or partially reflected in a region where any effect of the heat wave or pressure wave received from the material upon absorption of excitation radiation (18) is negligible, and wherein the detection apparatus includes additional detection equipment for detecting the degree of deflection of the reference beam (92) after reflection at the contact surface (14).

17. The apparatus (10) as claimed in claim 16, The additional detection device is used to measure the deflection angle of the detection reference beam (92) after it is reflected at the contact surface (14).

18. The apparatus (10) as claimed in claim 16, The additional detection device mentioned above includes a photodetector.

19. The apparatus (10) as claimed in claim 16, The additional detection device mentioned above includes a position-sensitive photodetector.

20. The apparatus (10) as claimed in claim 1 or 2, wherein, A protrusion (80) is formed on the contact surface (14), the protrusion having a front surface (82) facing the material (12), and when the material contacts the contact surface, the protrusion contacts the material, and the excitation radiation (18) irradiates the material (12) through the front surface (82) of the protrusion (80).

21. The device (10) of claim 20, wherein the protrusion (80) has a diameter of less than 0.3 cm. 2 The coverage area.

22. The device (10) of claim 20, wherein the protrusion (80) has a diameter of less than 0.2 cm. 2 The coverage area.

23. The device (10) of claim 20, wherein the protrusion (80) has a diameter of less than 0.1 cm. 2 The coverage area.

24. The device (10) of claim 20, wherein the protrusion (80) has a diameter of less than 0.05 cm. 2 The coverage area.

25. The device (10) of claim 20, wherein the protrusion (80) has a diameter of less than 0.02 cm. 2 The coverage area.

26. The device (10) of claim 20, wherein the protrusion (80) has a tapered shape having one or more sidewalls (84) that taper toward the front surface (82).

27. The apparatus (10) as claimed in claim 20, wherein, The protrusion (80) has a circular, elliptical, or square coverage area.

28. The apparatus (10) as claimed in claim 20, wherein, The protrusion (80) is ridge-shaped, has a longer extension in a first direction, and a shorter extension in a second direction orthogonal to the first direction, wherein the longer extension is at least 1.5 times longer than the shorter extension.

29. The apparatus (10) as claimed in claim 28, in, The longer extension is at least 2.0 times longer than the shorter extension.

30. The apparatus (10) as claimed in claim 28, in, The longer extension is at least 2.5 times longer than the shorter extension.

31. The apparatus (10) as claimed in claim 28, in, The longer extension is at least 3.0 times longer than the shorter extension.

32. The apparatus (10) as claimed in claim 1 or 2, wherein, A pressure sensor (86) is provided to measure the contact pressure between the material (12) and the measuring body.

33. The apparatus (10) as claimed in claim 32, wherein, The device (10) further includes a control system configured to receive from the pressure sensor (86) a signal indicating the contact pressure between the material (12) and the measuring body (16), wherein the control system is configured to check whether the contact pressure is lower than a predetermined threshold, and if the contact pressure is found to be lower than the threshold, is configured to perform one or more of the following: The indication is a lack of user contact pressure. To prevent the analyte measurement process from starting, and Interrupt the current analyte measurement process.

34. The apparatus (10) as claimed in claim 1 or 2, wherein, The device further includes a clamping device (106) comprising a clamping member (108) movable between an open position and a closed position, wherein in the open position the clamping member (108) is moved away from the contact surface (14) of the measuring body (16), and in the closed position the clamping member (108) is close to the contact surface (14), the clamping member (108) being biased toward the closed position, wherein when the clamping member is in the open position the material (12) can be placed on the contact surface (14), and wherein the clamping member (108) is adapted to press the material (12) against the contact surface (14) due to the biasing force toward the closed position.

35. The apparatus (10) as claimed in claim 34, wherein, A pressure sensor (86) is arranged on a clamping device (106).

36. The apparatus (10) as claimed in claim 32, wherein, A pressure sensor (86) is arranged on a clamping device (106).

37. The apparatus (10) as claimed in claim 1 or 2, wherein, The measuring body (16) is transmissive to the excitation radiation (18). The excitation radiation source (26) is configured to provide the excitation radiation (18) as an excitation beam, and The excitation radiation source (26) is arranged such that the excitation beam is irradiated into the measuring body (16) at the second incident surface of the measuring body (16), propagates through a portion of the measuring body (16), and exits from the measuring body (16) at the contact surface (14). The excitation beam strikes the second incident surface at an angle of 89.0° or less and 82.0° or greater.

38. The apparatus (10) as claimed in claim 37, The excitation beam strikes the second incident surface at an angle of 88.0° or less and 84.0° or greater.

39. The apparatus (10) as claimed in claim 37, The excitation beam strikes the second incident surface at an angle of 87.5° or less and 85.0° or greater.

40. The apparatus (10) of claim 37, wherein the excitation beam strikes the contact surface (14) of the measuring body at an angle of 90° ± 1.5°.

41. The apparatus (10) of claim 37, wherein the second incident surface and the contact surface (14) are inclined relative to each other at angles of 1.0° or greater and 8.0° or less at the respective portions of the second incident surface and the contact surface (14) where the excitation beam enters and exits the measuring body.

42. The apparatus (10) of claim 37, wherein the second incident surface and the contact surface (14) are inclined relative to each other at angles of 2.0° or greater and 6.0° or less at corresponding portions of the second incident surface and the contact surface (14) of the measuring body, respectively, where the excitation beam enters and exits the measuring body.

43. The apparatus (10) of claim 37, wherein the second incident surface and the contact surface (14) are inclined relative to each other at angles of 2.5° or greater and 5.0° or less at the respective portions of the second incident surface and the contact surface (14) where the excitation beam enters and exits the measuring body.

44. The apparatus (10) as claimed in claim 1 or 2, wherein, The material (12) is human tissue, and the analyte is glucose present in the skin.

45. The apparatus (10) as claimed in claim 1 or 2, wherein, The material (12) is human skin.

46. ​​The apparatus (10) as claimed in claim 1 or 2, wherein, The analyte is glucose, which is present in the interstitial fluid of the skin.

47. The apparatus (10) as claimed in claim 1 or 2, wherein, The excitation radiation (18) is generated using an array of lasers, each with a dedicated wavelength.

48. The apparatus (10) as claimed in claim 1 or 2, wherein, The excitation radiation (18) is generated using a quantum cascaded laser array, each laser having a dedicated wavelength.

49. The apparatus (10) as claimed in claim 1 or 2, wherein, The excitation radiation (18) is generated using at least one tunable laser.

50. The apparatus (10) as claimed in claim 1 or 2, wherein, The excitation radiation is generated using at least one tunable quantum cascade laser (18).

51. The apparatus (10) as claimed in claim 1 or 2, wherein, Some or all of the excitation wavelengths are in the range of 5 μm to 13 μm.

52. The apparatus (10) as claimed in claim 1 or 2, wherein, Some or all of the excitation wavelengths are in the range of 8 μm to 11 μm.

53. A method for analyzing a material (12) containing at least one analyte, the method comprising: - The measuring body (16) having a contact surface (14) is brought into thermal or pressure-transmitting contact with the material (12), the thermal or pressure-transmitting contact allowing heat waves or pressure waves generated by absorbing excitation radiation (18) in the material to be transmitted to the measuring body. -Irradiate the material (12) with excitation radiation (18) so that it is absorbed therein. - Generates a detection beam (22) that travels through at least a portion of the measuring body (16) or a component included in the measuring body, wherein the detection beam is totally or partially reflected at the contact surface (14), and wherein the detection beam (22) is deflected as a thermal or pressure wave generated by absorbing excitation radiation in the material (12) is transmitted to the measuring body (16), and -After the detection beam (22) is reflected at the contact surface (14), the degree of deflection of the detection beam (22) is detected. - wherein the contact surface (14) of the measuring body is bent in at least one principal direction in the area where the detection beam (22) is reflected. The detection beam (22) before and after reflection at the contact surface (14) defines a detection light plane, wherein at least one principal direction is located within the detection light plane or forms an angle of less than 30° with the detection light plane.

54. The method as described in claim 53, in, After the detection beam (22) is reflected at the contact surface (14), the deflection angle of the detection beam (22) is detected.

55. The method of claim 53, wherein, The curvature in at least one principal direction corresponds to a radius of curvature in the range of 5 to 30 mm.

56. The method of claim 53, wherein, The curvature in the at least one principal direction corresponds to a radius of curvature in the range of 10 to 20 mm.

57. The method according to any one of claims 53 to 56, wherein, The curvature in the at least one principal direction is either concave or convex.

58. The method of any one of claims 53 to 56, wherein the at least one principal direction is located within the detection light plane or forms an angle of less than 20° with the detection light plane.

59. The method according to any one of claims 53 to 56, wherein, The detection beam (22) is irradiated into the measuring body (16) at the first incident surface, propagates through a portion of the measuring body, and exits from the measuring body at the exit surface (74). The detection beam (22) strikes the exit surface (74) at an angle of 5° or greater relative to the normal of the exit surface (74) without any deflection due to local changes in refractive index, such that the detection beam (22) is refracted as it exits the exit surface (74) of the measuring body (16), wherein the orientation of the exit surface (74) relative to the detection beam (22) causes the detection beam (22) to increase the angle of the detection beam (22) relative to the normal of the exit surface (74) in response to the deflection of the heat wave or pressure wave transmitted to the measuring body (16).

60. The method of claim 59, The detection beam (22) strikes the exit surface (74) at an angle of 10° or greater relative to the normal of the exit surface (74) without any deflection caused by local changes in refractive index.

61. The method of claim 59, The detection beam (22) strikes the exit surface (74) at an angle of 15° or greater relative to the normal of the exit surface (74) without any deflection caused by local changes in refractive index.

62. The method according to any one of claims 53 to 56, wherein, The detection beam (22) is irradiated into the measuring body (16) at the first incident surface, propagates through a portion of the measuring body (16), and exits from the measuring body (16) at the exit surface (74), wherein a focusing lens (76) is integrally formed with the first incident surface for focusing the detection beam (22) entering the measuring body (16) in at least one dimension, and / or a collimating lens (78) is integrally formed with the exit surface (74) for collimating the detection beam (22) in at least one dimension.

63. The method of claim 62, wherein, At least one of the focusing lens (76) and the collimating lens (78) is a cylindrical lens that focuses and collimates the detection beam (22) at least primarily in one dimension.

64. The method according to any one of claims 53 to 56, wherein, The detection beam (22) strikes a position-sensitive detector, wherein the position-sensitive detector detects the positional offset of the detection beam (22) striking the position-sensitive detector in at least one sensing direction. The position-sensitive detector is arranged such that the deflection of the detection beam (22) causes a shift in the position of the detection beam (22) striking the position-sensitive detector in the at least one sensing direction, and A cylindrical lens is provided in the optical path of the detection beam (22) to shape the contour of the detection beam (22) and / or the position sensitive detector is arranged at an angle deviating from the detection beam (22) by 90°, such that the diameter of the detection beam (22) striking the position sensitive detector in the sensing direction is at least 1.5 times the diameter of the detection beam (22) in the direction orthogonal to the sensing direction.

65. The method of claim 64, The diameter of the detection beam (22) striking the position-sensitive detector in the sensing direction is at least 2.0 times the diameter of the detection beam (22) in a direction orthogonal to the sensing direction.

66. The method of claim 64, wherein, The cylindrical lens is a collimating lens (78) arranged in the optical path of the detection beam (22) between the reflection of the detection beam (22) at the contact surface (14) and the position-sensitive detector, wherein the cylindrical lens collimates the detection beam (22) at least primarily in a dimension orthogonal to the sensing direction of the position-sensitive detector.

67. The method of claim 66, The cylindrical collimating lens is integrally formed with the exit surface (74) of the measuring body from which the detection beam (22) exits from the measuring body (16).

68. The method according to any one of claims 53 to 56, wherein, The source beam is split into the detection beam (22) and the reference beam (92), wherein the reference beam (92) is also guided at the surface (14) of the measuring body (16) in thermal or pressure contact with the material (12), but is totally or partially reflected in a region where any influence of the heat wave or pressure wave received from the material when absorbing the excitation radiation (18) is negligible, and the degree of deflection of the reference beam (92) after reflection at the contacting surface (14) is detected.

69. The method of claim 68, A photodetector is used to detect the degree of deflection of the reference beam (92) after it is reflected at the contact surface (14).

70. The method of claim 68, A position-sensitive photodetector is used to detect the deflection angle of the reference beam (92) after it is reflected at the contact surface (14).

71. The method according to any one of claims 53 to 56, wherein, A protrusion (80) is formed on the contact surface (14), the protrusion having a front surface (82) facing the material (12), and when the material contacts the contact surface, the protrusion contacts the material, and the excitation radiation (18) irradiates the material (12) through the front surface (82) of the protrusion (80).

72. The method of claim 71, wherein the protrusion (80) has a diameter of less than 0.3 cm. 2 The coverage area.

73. The method of claim 71, wherein the protrusion (80) has a diameter of less than 0.2 cm. 2 The coverage area.

74. The method of claim 71, wherein the protrusion (80) has a diameter of less than 0.1 cm. 2 The coverage area.

75. The method of claim 71, wherein the protrusion (80) has a diameter of less than 0.05 cm. 2 The coverage area.

76. The method of claim 71, wherein the protrusion (80) has a diameter of less than 0.02 cm. 2 The coverage area.

77. The method of claim 71, wherein, The protrusion (80) has a tapered shape and has one or more sidewalls (84) that taper toward the front surface (82).

78. The method of claim 71, wherein, The protrusion (80) has a circular, elliptical, or square coverage area.

79. The method of claim 71, wherein, The protrusion (80) is ridge-shaped, has a longer extension in a first direction, and a shorter extension in a second direction orthogonal to the first direction, wherein the longer extension is at least 1.5 times longer than the shorter extension.

80. The method of claim 79, in, The longer extension is at least 2.0 times longer than the shorter extension.

81. The method as described in claim 79, in, The longer extension is at least 2.5 times longer than the shorter extension.

82. The method as described in claim 79, in, The longer extension is at least 3.0 times longer than the shorter extension.

83. The method according to any one of claims 53 to 56, wherein, Measure the contact pressure between the material (12) and the measuring body.

84. The method of claim 83, further comprising the step of: Check whether the contact pressure is lower than a predetermined threshold, and if the contact pressure is found to be lower than the threshold, perform one or more of the following steps: Inform the user of the lack of contact pressure. To prevent the analyte measurement process from starting, and Interrupt the current analyte measurement process.

85. The method of any one of claims 53 to 56, further comprising the step of securing the material (12) to the contact surface (14) using a clamping device (106), the clamping device (106) including a clamping member (108) movable between an open position and a closed position, wherein in the open position the clamping member (108) is moved away from the contact surface (14) of the measuring body (16), and in the closed position near the contact surface (14), the clamping member (108) is biased toward the closed position, wherein when the clamping member is in the open position the material (12) is placed on the contact surface (14), and wherein the clamping member (108) presses the material (12) against the contact surface (14) due to the biasing force toward the closed position.

86. The method of claim 85, wherein the pressure sensor (86) is disposed on the clamping device (106).

87. The method according to any one of claims 53 to 56, wherein, The measuring body (16) is transmissive to the excitation radiation (18). The excitation radiation source (26) provides the excitation radiation (18) as the excitation beam, and The excitation beam is irradiated into the measuring body (16) at the second incident surface, propagates through a portion of the measuring body (16), and exits from the measuring body (16) at the contact surface (14). The excitation beam strikes the second incident surface at an angle of 89.0° or less and 82.0° or greater.

88. The method as described in claim 87, The excitation beam strikes the second incident surface at an angle of 88.0° or less and 84.0° or greater.

89. The method of claim 87, The excitation beam strikes the second incident surface at an angle of 87.5° or less and 85.0° or greater.

90. The method of claim 87, wherein the excitation beam strikes the contact surface (14) of the measuring body at an angle of 90° ± 1.5°.

91. The method of claim 87, wherein the second incident surface and the contact surface (14) are inclined relative to each other at corresponding portions of the second incident surface and the contact surface (14) of the measuring body at angles of 1.0° or greater and 8.0° or less.

92. The method of claim 87, wherein the second incident surface and the contact surface (14) are inclined relative to each other at corresponding portions of the second incident surface and the contact surface (14) of the measuring body at angles of 2.0° or greater and 6.0° or less.

93. The method of claim 87, wherein the second incident surface and the contact surface (14) are inclined relative to each other at corresponding portions of the second incident surface and the contact surface (14) of the measuring body at angles of 2.5° or greater and 5.0° or less.

94. The method according to any one of claims 53 to 56, wherein, The detection includes generating a detection beam (22) that travels through at least a portion of the measuring body (16) or a component included in the measuring body (16). When absorbing the excitation radiation (18), the physical response of the measuring body (16) to the thermal or pressure waves received from the material (12) is a local change in the refractive index of the measuring body (16) or the component, and The detection includes either detecting a change in the optical path or a phase change in the detection beam due to a change in refractive index.

95. The method of any one of claims 53 to 56, wherein the material (12) is human tissue and the analyte is glucose present in the skin.

96. The method of any one of claims 53 to 56, wherein the material (12) is human skin.

97. The method according to any one of claims 53 to 56, wherein, The analyte is glucose, which is present in the interstitial fluid of the skin.

98. The method of any one of claims 53 to 56, further comprising the step of generating the excitation radiation (18) using an array of lasers, each laser having a dedicated wavelength.

99. The method of any one of claims 53 to 56, further comprising the step of generating the excitation radiation (18) using a quantum cascaded laser array, each laser having a dedicated wavelength.

100. The method of any one of claims 53 to 56, further comprising the step of generating excitation radiation (18) using at least one tunable laser.

101. The method of any one of claims 53 to 56, further comprising the step of generating excitation radiation (18) using at least one tunable quantum cascade laser.

102. The method according to any one of claims 53 to 56, wherein, Some or all of the excitation wavelengths are between 5 μm and 13 μm.

103. The method according to any one of claims 53 to 56, wherein, Some or all of the excitation wavelengths are between 8 μm and 11 μm.

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