SENSOR ARRANGEMENT

Description

[0001] The invention relates to a sensor arrangement according to the preamble of claim 1. State of the art

[0002] The measurement of ingredients using optical spectroscopy, particularly near-infrared spectroscopy, is now an established technology. It is used in many applications, for example, in the food industry and in agriculture, e.g., to examine the condition of plants in a field, the ingredients of harvested plant parts, or the composition of manure (see, for example, WO 01 / 31304 A1). Other optical measurement methods also exist, e.g., Raman spectroscopy, in which (agricultural) materials are analyzed for ingredients or other parameters (EP 3 437 451 A1), or images of the material under investigation are taken using a camera (EP 1 956 361 A2).

[0003] Such optical sensor arrays are installed in housings due to the harsh environmental conditions in which they are used. Electromagnetic waves, whether in the visible wavelength range or short- or long-wave (ultraviolet or (near-) infrared), pass from the sample to be examined, which is positioned outside the housing, through a translucent window into the interior of the housing, where they are received by the detection elements of the sensor array. At the same time, the window protects the interior of the sensor array from the sample penetrating the interior and contaminating or destroying components of the sensor array. Furthermore, the window also serves to illuminate the sample using an electromagnetic wave source located inside the housing. The sensor arrays therefore comprise the detection elements, the light source, and the window as an interface to the sample within the housing.In some sensor arrangements (cf. DE 10 2020 205 708 A1, which is considered to be generic), the window is mounted on a flange which is positioned in front of an opening in the housing and releasably fastened (screwed) there.

[0004] In order to obtain signals with the highest possible information content from the detection elements, it is advisable to take measures that enable the detection elements to receive as little scattered light as possible (i.e. light that does not carry any information beneficial to the measurement or that reaches the detection elements from a direction other than that favorable for the measurement) from the light source or other locations.In the prior art, it was proposed to mount the light source and the detection elements in separate housings in order to provide separate paths of the light from the light source to the window and from the window to the detection elements (WO 01 / 31304 A1), to anti-reflectively coat the window (EP 1 782 046 A1), or to provide toothed scattered light traps arranged adjacent to the beam path of the light from the sample to a spectrometer, which are intended to filter out light of the first diffraction order (DE 10 2014 104 204 U1) or light from an unwanted signal source entering the housing of a spectrometer (US 8 717 561 B2).

[0005] EP 0 952 440 A2 describes a reading head with light-emitting diodes that illuminate a sample, and the light reflected from the sample passes through a channel in which a flat wall is provided with a stair-shaped toothing to reduce scattered light, into a photodetector.

[0006] EP 0 174 186 A2 shows a reflectometer with a light source, a window, and a detector for light that travels from the light source through the window to a sample and is reflected by the sample to the detector. Toothed structures acting as light traps are attached to conical wall sections in the light beam path from the light source to the window and from the window to the detector. Task

[0007] The installation of the light source and detection elements in separate housings according to WO 01 / 31304 A1 means that separate tubes must be routed to the window, resulting in a relatively large sensor arrangement overall, while the anti-reflective coating of the window according to EP 1 782 046 A1 has only a limited effect unless further measures are taken to reduce stray light. DE 10 2014 104 204 U1 and US 8 717 561 B2 refer to spectrometers in whose housing no light source is located. Instead, in the first case, light reflected or transmitted directly from the sample is to be filtered out, and in the second case, light originating from a direction not attributable to the signal source under investigation is to be filtered out. Thus, they cannot eliminate stray light that would fall from the light source into the detection elements. EP 0 952 440 A2 and EP 0 174 186 A2 do not disclose a preferred direction in which scattered light is reflected at the respective gears.

[0008] The invention aims to avoid or at least reduce the disadvantages mentioned. Solution

[0009] This object is achieved according to the invention by the teaching of patent claim 1, which defines the present invention, wherein the further patent claims list features which advantageously further develop the solution.

[0010] A sensor arrangement is equipped with a housing having an opening in which a window transparent to electromagnetic waves is mounted, a light source arranged in the housing for generating electromagnetic waves, and a detector arranged in the housing for detecting electromagnetic waves passing through the window, which waves have passed from the light source through the window onto a sample adjacent to the window and have been reflected by the sample. Arranged within the housing is a toothing configured to reduce scattered light reaching the detector from the light source. In this way, the intensity of the scattered light reaching the detector from the light source that has not traveled via the sample is reduced by being absorbed by the toothing and / or reflected away from the detector.

[0011] The toothing is arranged on the wall of a first chamber arranged between the light source and the window and on the wall of a second chamber arranged between the window or the first chamber and the detector.

[0012] The toothing is arranged in the area between the light source and the window in such a way that it reflects scattered light in the direction of the light source. The toothing is arranged in the area between the window and the detector in such a way that it reflects scattered light in the direction of the window. For this purpose, the toothing comprises a plurality of annular teeth, each of which has a surface oriented transversely to the optical axis of the light source or detector, which faces the light source or window, and a surface extending obliquely outwards, which faces the window or detector.

[0013] Additionally, the teeth can be attached to the inside of a flange that fixes the window to the housing.

[0014] The central axis of the window may be offset from the central axis of the flange and the toothing may be arranged concentrically to a point which lies at least approximately on the optical axis of the light source and the detector.

[0015] The detector can be implemented as a spectrometer array, camera or in any other way. Example

[0016] The drawings illustrate an embodiment of the invention, described in more detail below. They show: Fig. 1 a perspective view of a sensor arrangement, Fig. 2 a section through the sensor arrangement of the Figure 1, Fig. 3 a perspective view of a flange with a window built into it, Fig. 4 a side view of an agricultural machine in the form of a slurry tanker with a sensor arrangement according to Figures 1 to 3 , and Fig. 5 a side view of an agricultural working machine in the form of a combine harvester with a sensor arrangement according to Figures 1 to 3 .

[0017] The Figure 1shows a perspective view of a sensor arrangement 10. It comprises an approximately cuboid-shaped housing 12, which can be provided with lateral cooling fins (not shown), and a front plate 14, to which a flange 16 is attached. The flange 16 surrounds an opening in the housing 12. The flange 16 holds a window 18 that is sufficiently permeable to electromagnetic waves in the wavelength range to be examined. The window 18 is formed by a circular, flat disk attached to the flange 16 (e.g., in the manner described in DE 10 2020 205 708 A1) and serves as a passage for electromagnetic waves from a light source 40 to a sample 38 arranged outside the housing 12 and for the light waves reflected by the sample 38 into the housing 12. There, they are analyzed to determine certain properties of the sample. The sensor arrangement 12 can, as in the Figure 2shown, be designed as a near-infrared spectrometer, or be any other optical sensor, e.g. a camera, a thermometer or a Raman spectrometer.

[0018] The Figure 2 shows a section through the sensor arrangement 10 of the Figure 1, which is suitable for harvesters and other agricultural machinery. The sensor arrangement 10 comprises the housing 12, which has a window 18 on the front panel 14 and contains an illumination source 40, a spectrometer arrangement 28, and optionally one or more standards (not shown) for internal recalibration. Also arranged in the housing 12 are a processor 34 for recording and processing the measured values ​​and an interface 36 to a bus system. Quartz or sapphire glass is preferably used for the window 18 in the housing 12, through which both the illumination radiation and the radiation reflected by the sample 38 pass. Sapphire glass enables a sufficiently long service life of the window 18, even with highly abrasive samples 38 (e.g., samples 38 containing sand).The lamp power of the light source 40, which preferably has a reflector 20, can be automatically controlled in order to adapt the spectrometer arrangement 28 to the different reflection behaviors of a wide variety of samples 38.

[0019] The spectrometer arrangement 28 comprises a dispersion element 26 and a detector 32 with one or more sensitive elements and optionally has imaging optical assemblies 22, 30. The interface 36 to a bus system provided in the housing 12 is preferably designed as a wireless or wired connection for data transmission and / or calibration and / or system diagnostics and can support standards such as CAN, USB, RS232, wireless LAN, etc. However, it is also possible to establish the connection from the sensor arrangement to the bus system via electrical and / or fiber optic cables. In addition, the processor 34 for recording and processing the measured values ​​is arranged in the housing 12. This processor 34 can generate both raw data, i.e. the pre-processing of the data on a spectral basis, and calculated results, which can then be transmitted to a bus system via the existing interface 36.In addition, the processor 34 contains the software for the necessary bus management.

[0020] In arrangements not according to the invention, it would also be conceivable to position the spectrometer arrangement 28 with the dispersion element 26 outside the housing 12. In this case, the reflected light in the housing 12 is detected by an optical arrangement and fed to the external spectrometer arrangement via glass fibers. The other elements, such as the processor 34, etc., are then also arranged externally. The optical arrangement that detects the reflected light would then be considered the detector 32.

[0021] Based on calibrations, the intensity distribution of the reflected radiation can be used to determine different ingredients such as moisture, protein, starch, oil content, and properties such as cutting length, fiber condition, and sample temperature. Both static measurements and measurements of a material flow are possible with the sensor arrangement 10. The sensor arrangement 10 can be used on stationary systems or any machines in which the crop or another sample flows past the measuring head, for example in combine harvesters, forage harvesters, or slurry tankers, or the sensor arrangement 10 is moved past the crop, for example in a swath. In the sensor arrangement 10, the sample 38 to be measured is irradiated with light from the light source 40. The light generated by the light source 40, the wavelength of which does not necessarily have to be in the visible wavelength range, but can also be in the infrared or, if applicable,The radiation, which may be in the ultraviolet range, is concentrated by the reflector 20 and directed to the window 18 through a first tubular, circular-cylindrical chamber 42, which extends from the light source 40 to a dust protection disk 44 at its lower end, adjacent to the window 18. The radiation reflected by the sample 38 passes through the window 18 back into the first chamber 42 and from there into a second, also tubular, circular-cylindrical chamber 46, which branches off from the first chamber 42. The spectrometer arrangement 28 is arranged at the upper end of the second chamber 46. The chambers 42, 46 are arranged within an inner housing 48, which is closed off from the window 18 by the dust protection disk 44. It should also be noted that the second chamber 46 does not have to open into the first chamber 42, but can be arranged separately from it (see WO 01 / 31304 A1).

[0022] It can be seen that the quality of the signals provided by the detector array 32 improves with the higher the ratio of useful signal to background. Part of the background is formed by scattered light that enters the spectrometer array 28 from the light source 40 after multiple reflections on the inner walls of the chambers 42 and 46 or on the inside of the flange 58 without interacting with the sample 38.

[0023] Therefore, a number of measures are taken here to improve the ratio and useful signal by reducing stray light. The dust protection disc 44 is coated on both sides to prevent unwanted reflections, which also applies analogously to at least the inside of the window 18. For the same reason, the optical axis 50 of the light source 40 and the first chamber 42 are arranged at an angle to the plane of the window 18 and the dust protection disc 44, which differs from the angle of the optical axis 52 of the spectrometer arrangement 28 and the second chamber 46 relative to the plane of the window 18.

[0024] Furthermore, the inner walls of the first chamber 42 and the second chamber 46 are equipped with toothings 54, 56. These prevent or at least reduce the likelihood of light generated by the light source 40 entering the spectrometer arrangement 28 by reflecting it off the inner walls of the chambers 42, 46 by being reflected back toward the light source 40 by the toothings 54 of the inner wall of the first chamber 42. Similarly, the toothings 56 reflect any light that does not enter along the optical axis 52 of the spectrometer arrangement 28 back toward the window 18. The toothings 54 are therefore arranged such that the surfaces of the toothings 54 facing the light source 40 are directed approximately radially to the optical axis 50, while the surfaces of the toothings 54 facing the window 18 extend obliquely inward and axially.Similarly, the toothings 56 are arranged such that the surfaces of the toothings 56 facing the window 18 are directed approximately radially to the optical axis 52, while the surfaces of the toothings 56 facing the spectrometer arrangement 28 extend obliquely inward and axially. The toothings 54, 56 can be blackened and / or matte-finished in a conventional manner.

[0025] In other words, the serrations 54, 65 ensure that incident light is always reflected in a direction that, so to speak, extends the path to the detector 32. Furthermore, a portion of the light is absorbed by the serrations 54, 56. Therefore, the scattered light must undergo significantly more reflections before reaching the detector 32. Since light is lost with each reflection due to the matting or the scattered light is reflected back, the overall intensity of the scattered light reaching the detector 32 decreases.

[0026] Another source of potential disruptive reflections is the inside of the flange 16. Since the window 18 has a smaller diameter than the flange 16, the light source 40 illuminates not only the actual window 18, but also the surfaces of the flange 16 adjacent to the window 18. In order to prevent or at least reduce reflections emanating from there into the spectrometer arrangement 28, a toothing 58 is also provided there. There too, the surfaces of the toothing 58 facing the light source 40 or the spectrometer arrangement 28 are aligned transversely to the plane of the window 18, and the radially outward surfaces are inclined outwards and downwards. This ensures that as little light as possible from the light source 40 is reflected directly into the spectrometer arrangement 28 at these surfaces.

[0027] As shown by the Figure 3As can be seen, the window 18 is not arranged exactly centrally in the flange 16. The toothing 58 of the flange 16 is therefore not concentric around the center of the window 18, but around a point 60 which is located approximately where the optical axes 50, 52 intersect the window 18.

[0028] It should also be noted that the dimensioning and positioning of the gears 54, 56, 58 can be carried out by means of a simulation calculation by trying out different dimensions and positions and adopting the configuration leading to the lowest scattered light intensity in the spectrometer arrangement 28.

[0029] In the Figure 52 shows an agricultural machine 240 in the form of a slurry tanker being pulled across a field by a tractor 242 to spread slurry onto a field through a line 244. The output signal of the sensor arrangement 10, which interacts with the slurry flowing in the line 244, is fed to a controller 248, which is also connected to a positioning system 246. The controller 248 controls a valve 250, which specifies the flow rate of the slurry through the line 244 based on a spreading map stored in advance in the controller 248, which specifies how much ingredient (e.g. nitrogen, potassium, etc.) is to be spread per unit area, and based on the output signal to ensure compliance with the values ​​specified in the spreading map.

[0030] Figure 6 shows a further embodiment of a work machine 130 in the form of a self-propelled combine harvester 130, which is equipped with a sensor arrangement 10. The sensor arrangement 10 is mounted on the wall of a cross-conveyor screw 132 and interacts through an opening in the wall with the cleaned crop (grains), which is discharged from a cleaning device 134 and transferred by the cross-conveyor screw 132 to a grain elevator 136, which deposits it in a grain tank 138. The cleaning device 134 receives the crop from a crop receiving device 140, which feeds it to a threshing and separating unit 142.The sensor arrangement 10 provides specific ingredient information such as protein content, starch content, oil content and moisture content of the harvested grain, which is stored in a map by a control unit 144 together with position information provided by a receiving antenna 148 of a satellite-based positioning system.

Claims

1. Sensor arrangement (10) with: a housing (12) with an opening in which a window (18) transparent to electromagnetic waves is mounted, a light source (40), arranged in the housing (12), for generating electromagnetic waves, and a detector (32), arranged in the housing (12), for detecting electromagnetic waves coming in through the window (18), which have fallen from the light source through the window (18) onto a sample adjacent to the window (18) and have been reflected by the sample, wherein a first, circular-cylindrical chamber (42) is arranged between the light source (40) and the window (18) and a second, circular-cylindrical chamber (46) is arranged between the window (18) or the first chamber (42) and the detector (32), characterized in that within the housing (12) on the wall of the first chamber (42) and on the wall of the second chamber (46) a toothing (54, 56) is arranged in each case, which is configured to reduce stray light travelling from the light source (40) to the detector (32), in that the toothing (54) of the first chamber (42) is arranged in such a way that it reflects stray light in the direction of the light source (40), for which purpose the toothing (54) of the first chamber (42) comprises a multiplicity of annular teeth with surfaces which are oriented transversely to the optical axis (50) of the light source (40) and face the light source (40), and surfaces which extend obliquely outward and face the window (18), and in that the toothing (56) of the second chamber (46) is arranged in such a way that it reflects stray light in the direction of the window (18), for which purpose the toothing (56) of the second chamber (46) comprises a multiplicity of annular teeth with surfaces which are oriented transversely to the optical axis (52) of the detector (32) and face the window (18), and surfaces which extend obliquely outward and face the detector (32) .

2. Sensor arrangement according to Claim 1, wherein a toothing (58) is attached to the inside of a flange (16) which fixes the window (18) to the housing (12).

3. Sensor arrangement (10) according to Claim 2, wherein the centre axis of the window (18) is offset from the centre axis of the flange (16) and the toothing (58) of the flange (16) is arranged concentrically to a point (60), which at least approximately lies on the optical axis (50, 52) of the light source (40) and the detector (32).

4. Sensor arrangement (10) according to any of Claims 1 to 3, wherein the detector (32) comprises a spectrometer arrangement (28) and / or a camera.

5. Agricultural work machine (130, 240) with a sensor arrangement (10) according to any of the preceding claims.