Apparatus and Method for Analyte Measurement with Improved Detection of the Deflection of a Detection Light Beam

The apparatus (10) of one of the preceding claims, wherein the detection light beam (22) prior to and after reflection at said contact surface (14) 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°, preferably less than 20°.

The apparatus (10) of one of the preceding claims, wherein the detection light source (28) is arranged such that said detection light beam (22) is irradiated into said measurement body (16) at an entrance surface (72), propagates through a portion of said measurement body (16) and exits from the measurement body (16) at an exit surface (74),

• wherein the detection beam (22) impinges—in absence of any deflection due to said local change in refractive index—on the exit surface (74) at an angle of 5° or more, preferably 10° or more and most preferably 15° or more with respect to the normal to the exit surface (74), such that the detection beam (22) is refracted upon exiting from the exit surface (74) of the measurement body (16), wherein the orientation of the exit surface (74) with respect to the detection light beam (22) is such that said deflection of the detection light beam (22) in response to said heat or pressure waves being transferred to said measurement body (16) increases said angle of said detection light beam to the normal to the exit surface.

The apparatus (10) of one of the preceding claims, wherein the detection light source (28) is arranged such that said detection light beam (22) is irradiated into said measurement body (16) at an entrance surface (72), propagates through a portion of said measurement body (16) and exits from the measurement body (16) at an exit surface (74), wherein a focusing lens (76) is formed integrally with the entrance surface (72) for focusing said detection light beam (22) entering into said measurement body (16) in at least one dimension and/or a collimating lens (78) is formed integrally with the exit surface (74) for collimating said detection light beam (22) in at least one dimension.

The apparatus (10) of one of the preceding claims, wherein said detector (30) comprises a position sensitive detector on which said detection light beam (22) impinges, wherein said position sensitive detector (30) is sensitive for detecting shifts in position of the detection light beam (22) impinging thereon in at least one sensing direction,

• wherein said position sensitive detector (30) is arranged such that said deflection of said detection light beam (22) 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 (22) for shaping the profile of the detection light beam (22) and/or the position sensitive detector (30) is arranged at an angle deviating from 90° from the detection light beam (22), such that the diameter of the detection light beam (22) impinging on said position sensitive detector (30) in said sensing direction is at least 1.5 times as large, preferably at least 2.0 times as large as the diameter of the detection light beam (22) in a direction orthogonal to said sensing direction.

The apparatus (10) of one of the preceding claims, further comprising a beam splitter (90) for splitting a source light beam (80) into said detection light beam (22) and a reference light beam (92), wherein said reference light beam (92) is likewise directed to be totally or partially reflected at a surface (14) of said measurement body (16) that is in thermal or pressure-transmitting contact with said material (12), but in a region where any effect of heat or pressure waves received from the material upon absorption of excitation radiation (18) is negligible, and wherein said detection device comprises an additional detection device (96) for detecting a degree of deflection, in particular a deflection angle, of the reference light beam (92) after its reflection at said contact surface (14), wherein said additional detection device preferably comprises a photodetector, in particular a position sensitive photodetector (96).

The apparatus (10) of one of the preceding claims, wherein on said contact surface (14), a protrusion (80) is formed, said protrusion having a front surface (82) facing said material (12) and being in contact with the material when the material is brought in contact with the contact surface, and in that said excitation radiation (18) is irradiated into the material (12) through said front surface (82) of said protrusion (80).

The apparatus (10) of one of the preceding claims, wherein a pressure sensor (86) is provided for measuring a contact pressure between the material (12) and the measurement body.

The apparatus (10) of one of the preceding claims, wherein said apparatus further comprises a clamping device (106), said clamping device (106) comprising a clamping member (108) movable between an open position in which the clamping member (108) is moved away from the contact surface (14) of the measurement body (16), and a closed position, in which it is close to said contact surface (14), said clamping member (108) being biased towards the closed position, wherein said material (12) can be placed on the contact surface (14) when the clamping member is in the open position, and wherein said clamping member (108) is suitable for pressing said material (12) against the contact surface (14) due to the biasing force towards the closed position.

The apparatus (10) of one of the preceding claims, wherein said measurement body (16) is transparent for said excitation radiation (18),

• wherein said excitation radiation source (26) is configured for providing said excitation radiation (18) as an excitation beam, and
• wherein the excitation radiation source (26) is arranged such that said excitation beam is irradiated into said measurement body (16) at an entrance surface (70) thereof, propagates through a portion of said measurement body (16) and exits from the measurement body (16) at said contact surface (14),
• wherein the excitation beam (18) impinges on the entrance surface (70) at an angle of 89.0° or less, preferably 88.0° or less, and most preferably 87.5° or less, and of 82.0° or more, preferably 84.0° or more and most preferably 85.0° or more.

The apparatus (10) of one of the preceding claims, wherein said material (12) is human tissue, in particular human skin, and said analyte is glucose present in the skin, in particular in the interstitial fluid thereof.

The apparatus (10) of one of the preceding claims, wherein said excitation radiation (18) is generated using an array of lasers, in particular quantum cascade lasers, each having a dedicated wavelength.

The apparatus (10) of one of the preceding claims, wherein said excitation radiation (18) is generated using at least one tunable laser, in particular at least one tunable quantum cascade laser.

The apparatus (10) of one of the preceding claims, wherein some or all of said excitation wavelengths are in a range of 5 μm to 13 μm, preferably 8 μm to 11 μm.