Housing for a sensor and sensor

Abstract

A housing (1) for a sensor (2), comprising a housing upper part (3) and a housing lower part (4) which, when assembled, form a receiving space (5) suitable for receiving a circuit board (6) with at least one LED (15a, 15b) emitting light through the housing lower part (4), wherein several passages (10a, 10b, 10c) are formed in the housing lower part (4), each separated from the other by at least one partition (11a, 11b), and wherein a receiving space or receiving tray (9b) for an optical filter (12) formed in or on the housing lower part (4) is connected to at least one partition (11a, 11b), is characterized, with regard to the task of providing a sensor which receives signals of the light to be detected as reliably and clearly as possible, independent of the angles of incidence of the light reflected from a human or animal body onto the sensor, in that itthat a structure (7) for guiding light is formed or arranged in or on the lower part of the housing (4), which is directed towards the optical filter (12).

Description

[0001] The invention relates to a housing for a sensor according to the preamble of claim 1.

[0002] Such a housing for a sensor is already known from DE 10 2023 104 302 A1. With such a sensor, the function of human or animal organs can be examined by injecting a marker into them.

[0003] The marker typically contains a substance that can be stimulated to fluoresce by exposure to excitation light. The decrease in fluorescence over time can be considered an indicator of how well an organ, particularly a kidney, is breaking down or excreting the marker or substance. The sensor can be worn close to the body to detect the fluorescence.

[0004] DE 10 2016 115 607 A1 discloses a measuring system with a flow-measuring cell device. WO 2022 / 174 277 A1 discloses an optical unit onto which a fluorescent dye is applied. CN 103 411 941 A discloses an imaging technology. DE 20 2010 014 729 U1 discloses a sensor with a grid that tightens skin.

[0005] Against this background, a method for measuring physiological functions is already known from EP 0 966 306 B1. It is proposed to inject a patient with fluorophores or chromophores that fluoresce upon excitation with light and are excreted over time by kidney cells. This allows kidney function to be examined.

[0006] Against this background, EP 2 317 911 B1 discloses a sensor patch comprising an excitation light source and a detector. EP 2 895 073 B1 discloses an adhesive functional strip with a sensor head including LED light and a photodiode.

[0007] The housing of the sensor according to the aforementioned DE 10 2023 104 302 A1 is subject to special requirements. On the one hand, the housing must conduct excitation light from LEDs to the body of humans or animals, and on the other hand, reliably direct fluorescent light, which is reflected back towards the sensor by the excitation light, to a photodiode.

[0008] The aim is to minimize the amount of extraneous light, i.e., light superimposed on the fluorescent light, that falls on the photodiode. Against this background, DE 10 2023 104 302 A1 already discloses an optical filter that rests against a partition wall with as few gaps as possible and allows excitation light from the LEDs to pass through in the direction of emission, but is largely opaque to excitation light reflected back towards the photodiode.

[0009] Naturally, the optical filter should allow fluorescent light to pass through, which is reflected by a marker in the human or animal body, so that the photodiode can detect it.

[0010] Glass filters or thin-film filters are known from the prior art that block blue light from LEDs and allow green light, i.e., fluorescent light, to pass through.

[0011] However, a transmission curve of such a thin-film filter only reflects the optical conditions when light hits the filter perpendicularly.

[0012] In fact, the transmission behavior of a filter can exhibit an angular dependence with respect to the angle of incidence of the light beam. The frequency band to be filtered by the filter can be influenced by the angle of incidence of the incident light. The frequency band can shift towards shorter wavelengths, so that light with shorter wavelengths can penetrate the filter more easily and is blocked less than desired when the light strikes the filter at a larger angle of incidence. The following approximate formula applies to the shift by a wavelength interval: Δλ≈k⋅sin2α

[0013] In this formula, Δλ is the wavelength interval around which the displacement occurs, and α is the angle of incidence.

[0014] During a measurement, blue excitation light reflected from a patient's skin can therefore strike the filter at an angle of incidence other than 90°. As a result, the reflected blue light is blocked less effectively by the filter than it would be at a 90° angle, and thus interferes with the fluorescence light. The photodiode can therefore receive signals even from light it is not intended to detect.

[0015] The invention is therefore based on the objective of providing a sensor that receives reliable and clear signals of the light to be detected, as independently as possible of the angles of incidence of the light reflected from a human or animal body onto the sensor.

[0016] The present invention solves the aforementioned problem through the features of claim 1.

[0017] According to the invention, it was first recognized that only specific types of light may be guided through a structure to a photodiode in order to avoid signal distortion. It was then recognized that an optical filter must be combined with a structure that allows only light rays that have previously struck the optical filter at a small angle of incidence to pass through to the photodiode, while blocking, diverting, or suppressing other light rays. The light rays that strike the optical filter essentially perpendicularly or at a very small angle of incidence are defined and filtered by the optical filter according to the specific application and are then allowed to pass through the structure. In this way, light of a specific frequency range is allowed to pass through, while light of another frequency range is blocked.Furthermore, it has been recognized that the structure must be assigned to the housing in order to achieve a simple and compact housing design and to keep as few components as possible.

[0018] The structure is designed as a grid of holes, with each hole forming or leading into a light channel. This structure mechanically creates a geometric boundary for light potentially reflected onto the photodiode, ensuring that only light that has previously struck the optical filter at a small angle of incidence can reach the photodiode.

[0019] The structure could be designed as a grid of holes, with at least two holes separated by a bridge whose width is in the range of 0.01 to 1 mm. This allows for the creation of a large number of light channels and increases the signal of the reflected light to be detected.

[0020] The structure is designed as a perforated grid, with at least one hole having a diameter or width in the range of 0.01 to 0.8 mm. This perforated grid creates a geometric boundary for reflected light, so that preferably only reflected light that has previously struck the optical filter at an angle of incidence of less than 17° can reach the photodiode. Such light was also correctly filtered by the optical filter in an application-specific manner.

[0021] The structure is designed as a perforated grid, with at least one hole serving as a light channel and having a length in the range of 0.5 to 2 mm. This allows light striking the optical filter at a large angle of incidence to flow into the wall of the light channel and not reach the photodiode. Preferably, the light can be absorbed in the wall of the light channel.

[0022] The structure could be arranged and formed between two opaque partitions, with each partition separating two passages in the lower part of the housing. This prevents excitation light from an LED from falling directly onto the photodiode and ensures that excitation light reflected from a patient's skin, as well as fluorescent light, must first pass through the structure before reaching the photodiode.

[0023] The upper and / or lower housing parts could be made of a glass-free plastic, specifically one that contains no glass fibers. This prevents light from being conducted within the housing components and distorting signals. PA 6 is the preferred plastic material.

[0024] A sensor could comprise a housing of the type described above and a circuit board, the circuit board carrying two LEDs for emitting excitation light and a photodiode for detecting fluorescence light, the LEDs each projecting into a first and a third passage, the photodiode projecting into a second passage which opens into the structure, the passages for the LEDs each being separated from the second passage for the photodiode by an opaque partition, and an optical filter being accommodated in a receiving trough.

[0025] Such a sensor allows for measurements to be taken close to the body, lasting an hour or more. The sensor can be worn close to the body, and the patient being examined can move largely unhindered while wearing it. The recorded measurement data can be read from the sensor after it has been removed by the patient.

[0026] The circuit board could also ideally accommodate a microprocessor or microcontroller capable of processing the data acquired by the photodiode. The microprocessor can be accessed by inserting a connector into a socket on the sensor. This socket can also be used to connect a battery to the circuit board, powering the LEDs and electronics during measurement.

[0027] The optical filter could consist of a glass plate that carries an optical thin-film filter. This makes it possible to use a stable and sufficiently thick glass plate that is only partially coated with a thin layer.

[0028] Preferably, only one-third of the surface of the glass plate that is in contact with the structure is coated. Particularly preferably, only the coated part of the optical filter is in contact with the structure.

[0029] The glass plate is preferably 1 mm thick. The optical filter is preferably designed as a long-pass filter. This allows longer wavelengths to pass through while blocking shorter wavelengths. In this way, blue light from the LEDs can be blocked, and green light can be allowed to pass through to the photodiode as fluorescent light.

[0030] One arrangement could comprise a sensor of the type described here and a light-tight adhesive film attached to the lower part of the housing, with a cutout through which both excitation light and reflected light can pass. This adhesive film allows the sensor to be worn close to the body and also prevents light from being lost through lateral gaps during measurement.

[0031] The sensor is preferably used as an organ function sensor, especially as a kidney function sensor.

[0032] The drawing shows Fig. 1 an exploded view of a sensor, comprising in the plane of the drawing from top to bottom a housing top part, a circuit board, a housing bottom part and an optical filter, wherein a structure, namely a perforated grid, is formed in the housing bottom part, Fig. 2 in a schematic and, in terms of structure, not to scale section view, the sensor according to Fig. 1 in a composite state, showing that only light reflected from the patient's skin falls on the photodiode, which previously fell on the optical filter at an angle of incidence of less than 17°, because the schematically depicted structure geometrically forces this, Fig. 3 the housing according to Fig. 2, which accommodates the circuit board inside and carries the filter, thus forming a sensor, wherein the sensor is attached to the skin of a patient with the filter facing forward, and wherein light is schematically shown which is sent through the LEDs onto the skin of the patient and reflected from there, in order to then pass through the schematically shown structure to the photodiode, and Fig. 4 A schematic representation of the transmission behavior of an optical filter as a function of the wavelength of the incident light.

[0033] Fig. Figure 1 shows an exploded view of a sensor 2 with a housing 1. The housing 1 for the sensor 2 comprises a housing upper part 3 and a housing lower part 4, which in the assembled state form a receiving space 5 suitable for receiving a circuit board 6 with at least one LED 15a, 15b, which emits light through the housing lower part 4.

[0034] The lower housing section 4 has several passages 10a, 10b, 10c, each separated from the other by at least one opaque partition 11a, 11b. Adjoining at least one partition 11a, 11b in the direction of emission of the LEDs 15a, 15b is a receiving tray 9b formed in the lower housing section 4 for an optical filter 12.

[0035] In the lower housing part 4, a structure 7 is formed for guiding light, which can be directed towards the optical filter 12. Specifically, in the lower housing part 4, a structure 7 is formed for guiding light, against which the optical filter 12 can be placed without a gap.

[0036] Structure 7 is formed in one piece and made of the same material as the lower housing part 4. Structure 7 is designed as a sieve-like perforated grid with a plurality of holes 21.

[0037] The housing 1 consists of only two parts, namely the upper housing part 3 and the lower housing part 4.

[0038] Fig. Figure 2 shows schematically, not to scale, especially in relation to Fig. Figure 1, of the illustrated structure 7, shows that the structure 7 is configured as a perforated grid, with each perforation 21 forming a light channel. The structure 7 is configured as a perforated grid, with at least two perforations 21 separated from each other by a web 20, the width 20a of which is at least 0.3 mm. The structure 7 is configured as a perforated grid, with at least one perforation 21 having a diameter or width of 0.3 mm. The structure 7 is configured as a perforated grid, with at least one perforation 21 forming a light channel having a length of 1 mm. Fig. 2 and Fig. Figure 3 shows schematically enlarged only three holes 21.

[0039] Fig. Figure 2 shows specifically that only light which has previously fallen on the optical filter 12 at a small angle of incidence is guided through the structure 7 to fall on the photodiode 16.

[0040] The Fig. Figures 1 to 3 show that the structure 7 is arranged and formed between two opaque partitions 11a, 11b, each partition 11a, 11b separating two passages 10a, 10b, 10c in the lower part of the housing 4.

[0041] The upper housing part 3 and the lower housing part 4 are made of PA6 plastic, which is glass-free, specifically containing no glass fibers or glass particles. Structure 7 is also made of this type of plastic.

[0042] Fig. 2 and Fig. Figure 3 shows a sensor 2 comprising a housing 1 and a circuit board 6, wherein the circuit board 6 carries two LEDs 15a, 15b for emitting excitation light and a photodiode 16 for detecting fluorescence light, wherein the LEDs 15a, 15b each project into a first and a third passage 10a, 10c, wherein the photodiode 16 projects into a second passage 10b, which opens into and transitions into the structure 7, wherein the passages 10a, 10c for the LEDs 15a, 15b are each separated from the second passage 10b for the photodiode 16 by an opaque partition 11a, 11b, and wherein an optical filter 12 is accommodated in the receiving tray 9b, which is formed in the lower part of the housing 4.

[0043] The optical filter 12 is flush with the outer walls of the housing base 4 and can thus be placed flat and flush against the skin 19a of a patient without any lateral gaps. The optical filter 12 rests flush against the structure 7, which is made of an opaque plastic.

[0044] The Fig. Figures 1 to 3 show that the optical filter 12 has a glass plate 13a which carries an optical thin-film filter 13b. Only the middle third of the surface of the glass plate 13a, which faces the LEDs 15a, 15b and the photodiode 16, is coated with the thin-film filter 13b. Specifically, only the area of ​​the surface that is in gap-free contact with the structure 7 is coated.

[0045] Fig. Figure 3 shows an arrangement comprising sensor 2 according to Fig. 2 and a light-tight adhesive film 19, which is arranged on the lower part of the housing 4 and has a recess 22 through which both excitation light and reflected light can pass.

[0046] The Fig. 2 and Fig. Figure 3 shows specifically that a receiving tray 9a with a support base 9 is provided for the circuit board 6 in the lower housing part 4. The support base 9 adjoins the further receiving tray 9b for the optical filter 12, with the further receiving tray 9b for the optical filter 12 being vertically opposite the receiving tray 9a for the circuit board 6. The upper housing part 3 has a closed cover 3a, so that the electronics of the circuit board 6 are protected.

[0047] The circuit board 6 carries two LEDs 15a, 15b for emitting blue excitation light and at least one photodiode 16 for detecting green fluorescent light, wherein the LED 15a projects into a first passage 10a in the mounting base 9, wherein the photodiode 16 projects into a second passage 10b in the mounting base 9, wherein the second LED 15b projects into a third passage 10c in the mounting base 9, wherein the passages 10a, 10b are separated from each other by a first opaque partition 11a and wherein the passages 10b, 10c are laterally separated from each other by a second opaque partition 11b.

[0048] The partitions 11a and 11b rest with their upper ends against the circuit board 6 and form part of the support base 9, or are aligned with it and with each other. The partitions 11a and 11b rest with their lower ends against the optical filter 12 without any gap. The structure 7 also rests without any gap against the optical filter 12.

[0049] A microprocessor 17 is located on circuit board 6, which can evaluate the data acquired by the photodiode 16. The microprocessor 17 can be read by inserting a connector into a socket 18 in the sensor 2.

[0050] The connector 18 can also be used to connect a battery to the circuit board 6, which powers the LEDs 15a, 15b and the rest of the electronics during the measurement.

[0051] Downwards, i.e. in the direction of the excitation light exit, the housing 1 is open at least for light passage through the passages 10a to 10c, but mechanically closed by the optical filter 12, so that no access to the interior of the sensor 2 is possible from below either.

[0052] Only through the opening for connector 18 can a battery plug be electrically and mechanically connected to the circuit board 6. Connector 18 also serves to read data stored in the microprocessor 17 or a memory. Connector 18 is located in Fig. 1 shown.

[0053] Preferably, the width and / or length of the housing 1 is / are less than 1 cm. Furthermore preferably, the height of the housing 1 is less than 1 cm.

[0054] Fig. Figure 4 schematically shows that blue light from the wavelength range of 400 to 500 nm, which is emitted by the LEDs 15a, 15b as excitation light, is almost completely blocked by a long-pass filter, so that the transmission T with respect to this light is almost 0%. Fig.Figure 4 further shows schematically that green light from the wavelength range of 500 to 700 nm, which is reflected back as fluorescence light from a marker in the patient onto the photodiode 16, is predominantly transmitted through a long-pass filter, so that the transmission T with respect to this light is almost 100%, at least above 600 nm.

[0055] The transmission behavior shown assumes that both the blue and green light fall perpendicularly onto the long-pass filter. As soon as blue light falls on the long-pass filter at an angle of incidence other than 0°, it is transmitted more strongly by the long-pass filter because its transmittance with respect to shorter wavelength light increases.

[0056] The structure 7 described here ensures that shorter-wavelength light, which should actually have been filtered out by the long-pass filter, does not reach photodiode 7 as much as possible. Structure 7 ensures that only light which actually falls onto the optical filter 12 at a small angle of incidence and has been filtered according to the specific application reaches photodiode 16. Reference sign 1 case 2 Sensor 3 Housing top of 1 3a Lid of 3 4 Housing lower part of 1 5 recording rooms in 1 6 circuit boards 7 Structure, perforated grid 8a blue light spectrum of an LED for excitation 8b green light from marker 8c Transmission behavior of 12, 13a, 13b 9 support shelf 9a Receiving tray in 4 for 6 9b further receiving tray in 4 for 12 10a first round in 9 10b second round in 9 10c third round in 9 11a first partition wall 11b second partition wall 12 optical filters 13a Glass plate 13b optical thin-film filter 15a first LED 15b second LED 16 Photodiode 17 Microprocessor or microcontroller 18 plug connectors 19 light-tight adhesive films 19a Skin 20 jetties in 7 20a Width of 20 21 holes in 7 22 recess in 19

Claims

Housing (1) for a sensor (2), comprising a housing upper part (3) and a housing lower part (4), which in the assembled state form a receiving space (5) suitable for receiving a circuit board (6) with at least one LED (15a, 15b) emitting light through the housing lower part (4), wherein several passages (10a, 10b, 10c) are formed in the housing lower part (4), each separated from the other by at least one partition (11a, 11b), and wherein a receiving space or receiving tray (9b) for an optical filter (12) is formed in or on the housing lower part (4) adjoins at least one partition (11a, 11b), characterized in that a structure (7) for guiding light is formed or arranged in or on the housing lower part (4), which is oriented towards the optical filter (12), wherein the structure (7) is designed as a perforated grid, wherein each hole (21) forms a light channel or leads into a light channel,wherein at least one hole (21) has a diameter or width in the range of 0.01 to 0.8 mm, and wherein at least one hole (21) as a light channel has a length in the range of 0.5 to 2 mm. Housing (1) according to claim 1, characterized in that the structure (7) is designed as a grid of holes, wherein at least two holes (21) are separated from each other by a bridge (20) whose width (20a) is in the range of 0.01 to 1 mm. Housing (1) according to one of the preceding claims, characterized in that the structure (7) is arranged and formed between two opaque partitions (11a, 11b), each partition (11a, 11b) separating two passages (10a, 10b, 10c) in the lower part of the housing (4) from each other. Housing (1) according to one of the preceding claims, characterized in that the housing upper part (3) and / or the housing lower part (4) is / are made of a plastic which is glass-free, in particular contains no glass fibers. Sensor (2) comprising a housing (1) according to one of the preceding claims and a circuit board (6), wherein the circuit board (6) carries two LEDs (15a, 15b) for emitting excitation light and a photodiode (16) for detecting fluorescence light, wherein the LEDs (15a, 15b) each project into a first and a third passage (10a, 10c), wherein the photodiode (16) projects into a second passage (10b) which opens into the structure (7), wherein the passages (10a, 10c) for the LEDs (15a, 15b) are each separated from the second passage (10b) for the photodiode (16) by an opaque partition (11a, 11b) and wherein an optical filter (12) is accommodated in the receiving tray (9b). Sensor (2) according to claim 5, characterized in that the optical filter (12) has a glass plate (13a) which carries an optical thin-film filter (13b). Arrangement comprising a sensor (2) according to claim 5 or 6 and a light-tight adhesive film (19) which is arranged on the lower part of the housing (4) and has a recess (22) through which both excitation light and reflected light can pass.

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