Apparatus and method for analyte measurement with improved detection of the deflection of a detection light beam
Disclosed herein is an apparatus ( 10 ) for analyzing a material ( 12 ) comprising at least one analyte, said apparatus ( 10 ) comprising a measurement body ( 16 ) having a contact surface ( 14 ) suitable to be brought in thermal contact or pressure-transmitting contact with said 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 said measurement body ( 16 ) or a component included in said measurement body, wherein said detection light beam is directed to be totally or partially reflected at said contact surface ( 14 ), wherein said contact surface ( 14 ) of the measurement body is curved in at least one principal direction in the area where the detection light beam ( 22 ) is reflected.
1 . An apparatus for analyzing a material comprising at least one analyte, said apparatus comprising
a measurement body having a contact surface suitable to be brought in thermal contact or pressure-transmitting contact with said material, said thermal or pressure-transmitting contact permitting heat or pressure waves generated by absorption of excitation radiation in the material to be transferred to said measurement body,
an excitation radiation source configured for irradiating excitation radiation into the material to be absorbed therein, and
a detection light source for generating a detection light beam travelling through at least a portion of said measurement body or a component included in said measurement body,
wherein said detection light beam is directed to be totally or partially reflected at said contact surface, wherein said detection light beam is deflected upon heat or pressure waves generated by absorption of excitation radiation in the material being transferred to said measurement body, and
a detector for detecting a degree of deflection of the detection light beam after its reflection at said contact surface,
wherein said contact surface of the measurement body is curved in at least one principal direction in an area where the detection light beam is reflected, wherein the detection light beam prior to and after reflection at said contact surface defines a detection light plane, and wherein said principal direction lies within said detection light plane or forms an angle with the detection light plane that is less than 30°.
2 . The apparatus of claim 1 , wherein a curvature in said at least one principal direction corresponds to a radius of curvature in a range of 5 to 30 mm.
3 . The apparatus of claim 1 , wherein a curvature in said principal direction is one of concave or convex.
4 . The apparatus of claim 1 , wherein the detection light source is arranged such that said detection light beam is irradiated into said measurement body at an entrance surface, propagates through a portion of said measurement body and exits from the measurement body at an exit surface,
wherein the detection beam impinges—in absence of any deflection due to said local change in refractive index—on the exit surface at an angle of 5° or more with respect to the normal to the exit surface, such that the detection beam is refracted upon exiting from the exit surface of the measurement body, wherein the orientation of the exit surface with respect to the detection light beam is such that said deflection of the detection light beam in response to said heat or pressure waves being transferred to said measurement body increases said angle of said detection light beam to the normal to the exit surface.
5 . The apparatus of claim 1 , wherein said detector comprises a position sensitive detector on which said detection light beam impinges, wherein said position sensitive detector is sensitive for detecting shifts in position of the detection light beam impinging thereon in at least one sensing direction,
wherein said position sensitive detector is arranged such that said deflection of said detection light beam leads to a shift of the position of the detection light beam impinging thereon in said at least one sensing direction, and
wherein a cylinder lens is provided in the light path of the detection light beam for shaping the profile of the detection light beam or the position sensitive detector is arranged at an angle deviating from 90° from the detection light beam, such that the diameter of the detection light beam impinging on said position sensitive detector in said sensing direction is at least 1.5 times as large as the diameter of the detection light beam in a direction orthogonal to said sensing direction.
6 . The apparatus of claim 5 , wherein said cylinder lens is a collimating lens arranged in said light path of the detection light beam between its reflection at said contact surface and said position sensitive detector, wherein said cylinder lens is arranged to collimate said detection light beam at least predominantly in a dimension orthogonal to said sensing direction of said position sensitive detector.
7 . The apparatus of claim 1 , further comprising a beam splitter for splitting a source light beam into said detection light beam and a reference light beam, wherein said reference light beam is likewise directed to be totally or partially reflected at a surface of said measurement body that is in thermal or pressure-transmitting contact with said material, but in a region where any effect of heat or pressure waves received from the material upon absorption of excitation radiation is negligible, and wherein said detection device comprises an additional detection device for detecting a degree of deflection of the reference light beam after its reflection at said contact surface.
8 . The apparatus of claim 1 , wherein on said contact surface, a protrusion is formed, said protrusion having a front surface facing said material and being in contact with the material when the material is brought in contact with the contact surface, and in that said excitation radiation is irradiated into the material through said front surface of said protrusion.
9 . The apparatus of claim 8 , wherein said protrusion has a footprint area of less than 0.3 cm 2 .
10 . The apparatus of claim 8 , wherein said protrusion has a tapering shape with one or more sidewalls tapering towards said front surface.
11 . The apparatus of claim 8 , wherein said protrusion has a footprint which is of circular, oval, or square shape.
12 . The apparatus of claim 8 , wherein said protrusion is ridge shaped, having a longer extension in a first direction and a shorter extension in a second direction orthogonal to the first direction, wherein the longer extension exceeds the shorter extension by a factor of at least 1.5.
13 . The apparatus of claim 1 , wherein said material is particular-human skin, and said analyte is glucose present in the interstitial fluid thereof.
14 . The apparatus of claim 1 , wherein said excitation radiation is generated using an array of quantum cascade lasers, each having a dedicated wavelength.
15 . The apparatus of claim 1 , wherein some or all of said excitation wavelengths are in a range of 5 μm to 13 μm.
16 . A method of analyzing a material comprising at least one analyte, said method comprising
bringing a measurement body having a contact surface in thermal contact or pressure-transmitting contact with said material, said thermal or pressure-transmitting contact permitting heat or pressure waves generated by absorption of excitation radiation in the material to be transferred to said measurement body,
irradiating excitation radiation into the material to be absorbed therein,
generating a detection light beam travelling through at least a portion of said measurement body or a component included in said measurement body, wherein said detection light beam is totally or partially reflected at said contact surface, wherein said detection light beam is deflected upon heat or pressure waves generated by absorption of excitation radiation in the material being transferred to said measurement body, and
detecting a degree of deflection of the detection light beam after its reflection at said contact surface,
wherein said contact surface of the measurement body is curved in at least one principal direction in an area where the detection light beam is reflected, wherein the detection light beam prior to and after reflection at said contact surface defines a detection light plane, and wherein said principal direction lies within said detection light plane or forms an angle with the detection light plane that is less than 30°.
17 . The method of claim 16 , wherein a curvature in said at least one principal direction corresponds to a radius of curvature in a range of 5 to 30 mm.
18 . The method of claim 16 , wherein said a curvature in said at least one principal direction is one of concave or convex.
19 . The method of claim 16 , wherein the detection light source is arranged such that said detection light beam is irradiated into said measurement body at an entrance surface, propagates through a portion of said measurement body and exits from the measurement body at an exit surface,
wherein the detection beam impinges—in absence of any deflection due to said local change in refractive index—on the exit surface at an angle of 5° or more, with respect to the normal to the exit surface, such that the detection beam is refracted upon exiting from the exit surface of the measurement body, wherein the orientation of the exit surface with respect to the detection light beam is such that said deflection of the detection light beam in response to said heat or pressure waves being transferred to said measurement body increases said angle of said detection light beam to a normal to the exit surface.
20 . The method of claim 16 , wherein said detector comprises a position sensitive detector on which said detection light beam impinges, wherein said position sensitive detector detects shifts in position of the detection light beam impinging thereon in at least one sensing direction,
wherein said position sensitive detector is arranged such that said deflection of said detection light beam leads to a shift of the position of the detection light beam impinging thereon in said at least one sensing direction, and
wherein a cylinder lens is provided in the light path of the detection light beam for shaping the profile of the detection light beam or the position sensitive detector is arranged at an angle deviating from 90° from the detection light beam, such that the diameter of the detection light beam impinging on said position sensitive detector in said sensing direction is at least 1.5 times as large as the diameter of the detection light beam in a direction orthogonal to said sensing direction.
21 . The method of claim 20 , wherein said cylinder lens is a collimating lens arranged in said light path of the detection light beam between its reflection at said contact surface and said position sensitive detector, wherein said cylinder lens collimates said detection light beam at least predominantly in a dimension orthogonal to said sensing direction of said position sensitive detector, wherein said cylinder collimating lens is formed integrally with an exit surface of said measurement body at which the detection light beam exits from the measurement body.
22 . The method of claim 16 , wherein a source light beam is splitted into said detection light beam and a reference light beam, wherein said reference light beam is likewise directed to be totally or partially reflected at a surface of said measurement body that is in thermal or pressure-transmitting contact with said material, but in a region where any effect of heat or pressure waves received from the material upon absorption of excitation radiation is negligible, and wherein a degree of deflection of the reference light beam after its reflection at said contact surface is detected using a photodetector.
23 . The method of claim 16 , wherein on said contact surface, a protrusion is formed, said protrusion having a front surface facing said material and being in contact with the material when the material is brought in contact with the contact surface, and in that said excitation radiation is irradiated into the material through said front surface of said protrusion.
24 . The method of claim 23 , wherein said protrusion has a footprint area of less than 0.3 cm 2 .
25 . The method of claim 23 , wherein said protrusion has a tapering shape with one or more sidewalls tapering towards said front surface.
26 . The method of claim 23 , wherein said protrusion has a footprint which is of circular, oval, or square shape.
27 . The method of claim 23 , wherein said protrusion is ridge shaped, having a longer extension in a first direction and a shorter extension in a second direction orthogonal to the first direction, wherein the longer extension exceeds the shorter extension by a factor of at least 1.5.
28 . The method of claim 16 , wherein said material is human skin,
and said analyte is glucose present in the skin.
29 . The method of claim 16 , wherein some or all of said excitation wavelengths are in a range of 5 μm to 13 μm.