WO2016137317A1

WO2016137317A1 - An infrared sensor unit, a method and a computer program product

Info

Publication number: WO2016137317A1
Application number: PCT/NL2016/050121
Authority: WO
Inventors: Frits Johan OUKES
Original assignee: Tree Of Knowledge Patents B.V.
Priority date: 2015-02-23
Filing date: 2016-02-19
Publication date: 2016-09-01
Also published as: NL2014335B1

Abstract

The invention relates to an infrared sensor unit for performing an infrared measurement on an agricultural or horticultural sample. The sensor unit comprises an illumination unit for generating infrared light propagating towards the sample, and a spectrometer for sensing the generated infrared light after interaction with the sample. The illumination unit includes a control unit for tuning the amount of infrared light generated by the illumination unit.

Description

AN INFRARED SENSOR UNIT, A METHOD AND A

Title: COMPUTER PROGRAM PRODUCT

The invention relates to an infrared sensor unit for performing an infrared measurement on an agricultural or horticultural sample, comprising an illumination unit for generating infrared light propagating towards the sample, and a spectrometer for sensing the generated infrared light after interaction with the sample.

Such infrared sensor units are known for performing infrared measurements on samples so that values of physical, chemical and/or biological parameters can be determined in a reliable and quick manner.

However, it appears in practice that a specific infrared sensor unit is merely applicable to a limited number of sample types, due to limitations of the measurement range of the spectrometer.

It is an object of the invention to provide an infrared sensor according to the preamble that is applicable to a wider number of sample types. Thereto, according to an aspect of the invention, an infrared sensor unit according to the preamble is provided, wherein the illumination unit includes a control unit for tuning the amount of infrared light generated by the illumination unit.

By tuning the amount of infrared light generated by the illumination unit the amount of light sensed by the spectrometer can be set to fall within a measurement range of the spectrometer, thereby enabhng a the infrared sensor unit to carry out an accurate measurement to a wide variety of sample types. Further, a wide variety of characteristics of the sample can thus be analyzed.

The invention is at least partly based on the insight that the amount of infrared light, after interaction with the sample, may be strongly dependent on the type of the sample. Then, by adjusting the infrared light energy, the infrared sensor unit is apt to perform measurements on samples having a relatively weak or a relatively strong response to the infrared signal interrogating the sample.

It is noted that patent publication DE 102011 115717 discloses a handheld binocular including optics in a housing for visuahzation of an optic image. The binocular also comprises a spectrometer attached outside the housing and a light source. It is further noted that patent publication US 2008/0291455 discloses an apparatus for remotely sensing the reflectance characteristics of plants and soil. The apparatus includes LEDs for illuminating the object to be probed, and photodetectors for sensing the reflected light. It is also noted that patent publication WO 2013/148656 discloses an optical analyser for identification of materials using near- infrared transmission spectroscopy combined with multivariate calibration methods for analysis of the spectral data.

The invention also relates to a method.

Further, the invention relates to a computer program product. A computer program product may comprise a set of computer executable instructions stored on a data carrier, such as a flash memory, a CD or a DVD. The set of computer executable instructions, which allow a

programmable computer to carry out the method as defined above, may also be available for downloading from a remote server, for example via the Internet, e.g. as an app.

Other advantageous embodiments according to the invention are described in the following claims.

By way of example only, embodiments of the present invention will now be described with reference to the accompanying figures in which

Fig. la shows a cross sectional schematic side view of an infrared sensor unit according to the invention;

Fig. lb shows a schematic bottom view of the unit of Fig. la; Fig. 2 shows a diagram illustrating levels of generated infrared light, and

Fig. 3 shows a cross sectional schematic side view of another infrared sensor unit according to the invention;

Fig. 4 shows a flow chart of an embodiment of a method according to the invention.

The figures merely illustrate a preferred embodiment according to the invention. In the figures, the same reference numbers refer to equal or corresponding parts.

Figure la shows a cross sectional schematic side view of an infrared sensor unit 1 according to the invention, while Figure lb shows a schematic bottom view of the unit 1. The unit 1 is arranged for performing an infrared measurement on an agricultural or horticultural sample 2.

The infrared sensor unit 1 has a number of components including an illumination unit and a spectrometer 11. Further, the infrared sensor unit 1 includes a collimator 4 and a fiber 6a interconnecting the collimator 4 to the spectrometer 11. The illumination unit is provided with a multiple number of infrared illuminator elements 3a-f for generating infrared light propagating towards the sample 2. After interaction with the sample 2, the infrared light is received by the collimator 4, forwarded via the fiber 6a to the spectrometer, and sensed by the spectrometer 11, i.e. converted into an electronic signal representative of the sensed infrared light.

The illumination unit also includes a control unit 5 for tuning the amount of infrared light generated by the illumination unit. The control unit 5 is connected to the individual infrared illuminator elements 3a-f via control lines 5a-f. Further, the infrared sensor unit 1 is provided with a communication unit 10 connected to the spectrometer 11 via a data hne 6b, such as a serial digital data channel, for communicating the sensed data with other devices. In addition, the infrared sensor unit 1 includes a processor unit 7 for controlling the operation of the sensor unit 1. The infrared sensor unit 1 includes a housing 8 for

accommodating the components therein or thereon, e.g. functioning as a handheld device.

During operation, the amount of infrared light that is generated by the illumination unit can be tuned thereby indirectly tuning the amount of infrared light that is sensed by the spectrometer 11. By setting the amount of sensed infrared light, the measurement range of the spectrometer 11 can effectively be exploited. If the amount of infrared light is relatively high after interaction with the sample, the infrared light level of the illumination unit can be set relatively low thereby counteracting that the spectrometer 11 is over exposed. On the other hand, if the amount of infrared light is relatively low after interaction with the sample, the infrared light level of the illumination unit can be set relatively high thereby facilitating that the spectrometer 11 senses a signal having an energy level that is sufficiently high above a sensitivity level of the spectrometer 11. Then, the amount of infrared light sensed by the

spectrometer 11 is within a measurement range of the spectrometer 11.

Preferably, the control unit 5 is arranged for switching the amount of infrared light between a pre-defined multiple number of discrete infrared light levels. As an example, the amount of infrared light can be selected from three, five or ten discrete levels, including a level wherein no hght is generated. Alternatively, the amount of infrared light can be set in a continuous range.

In a very advantageous embodiment, the amount of infrared light is adjusted to a pre-defined level that is associated with a selected

agricultural or horticultural sample class. Then, the amount of infrared hght can be set to a level that is pre-programmed in association with a particular sample class. As an example, different sample types can each be associated with a respective amount of infrared light to be generated by the illumination unit. Fig. 2 shows a diagram illustrating levels of generated infrared light. A vertical axis in the diagram denotes an intensity of infrared light / generated by the illumination unit. Along a horizontal axis C in the diagram a number of sample classes Ci, C2, C3 are shown. Each of the sample classes is related to a specific type of agricultural or horticultural sample such as sand, grass or corn. Further, each of the sample classes Ci, C2, C3 is related to a pre-defined discrete infrared light level , , /e.Then, each sample class may be coupled to a unique amount of infrared light to be generated by the illumination unit.

During operation of an advantageous embodiment of the unit 1 an agricultural or horticultural sample class C is selected, preferably by entering commands in a user-interface of the infrared sensor unit 1. Then, the control unit tunes the amount of infrared light by adjusting the amount of light to a pre-defined level , , h associated with the selected

agricultural or horticultural sample class Ci, C2, C3.

It is noted that the step of selecting an agricultural or horticultural sample class C can in principle be executed in another way, e.g. automatically or semi-automatically including a step of performing an automated classifying step, e.g. based on an image taken by a camera.

Optionally, the infrared sensor unit 1 is provided with a user interface arranged to receive user-specified instructions regarding the sample to be analyzed. As an example, the user may select a specific sample type from a pre-programmed list of sample types, each associated with a specific amount of infrared light to be generated. In principle, the list can be defined or extended by the user, e.g. based on actual test data. Alternatively or additionally, the infrared sensor unit 1 can be provided with a sensor for determining the sample type so that the amount of infrared light is adjusted automatically, depending on the outcome of the determined sample type, even without a user interaction. In a specific embodiment, the control unit 5 is arranged for varying the amount of infrared light of a subset of infrared illuminator elements 3 for tuning the overall amount of infrared light generated by all infrared illuminator elements 3. Applying this principle to the infrared sensor unit 1 as shown in Fig. 1, the subset of infrared illuminator elements 3 may include three elements generating a variable amount of infrared light, while another three elements generate a fixed amount of infrared light. However, also another distribution of illuminator elements 3

generating a variable and fixed amount of light, respectively, can be applied, e.g. four elements generating a variable amount of infrared light and two elements generating a fixed amount of infrared light.

In the shown embodiment, the collimator 4 is surrounded by the multiple number of infrared illuminator elements 3a-f on a circumscribing contour SC to obtain a focused infrared light beam on the sample 2. Further, the illuminator elements 3a-f are mainly evenly distributed on the

surrounding contour SC in a circumferential direction C relative to the collimator 4 to obtain a more or less evenly distributed infrared light beam on the sample 2. Alternative arrangements of the infrared illuminator elements can be implemented, e.g. by arranging the infrared illuminator elements in a one -dimensional or two-dimensional array.

Further, in the shown embodiment, the infrared illuminator elements 3 and the collimator 4 are arranged in or on a concave side of a dome-shaped bottom surface 9 of the housing 8 of the infrared sensor unit 1 to optimize enlightening conditions on the sample 2. In another

embodiment, the infrared illuminator elements 3 and the collimator 4 are arranged in another geometry, e.g. a plane surface.

It is noted that the geometry of the infrared sensor unit, especially regarding illuminating aspects of the illumination unit, such as the dome shaped bottom surface of the infrared sensor unit and the arrangement of illuminator elements on a circumscribing contour around the collimator, preferably evenly distributed, can not only be applied to the infrared sensor unit as defined in claim 1, but also more generally to an infrared sensor unit for performing an infrared measurement on an agricultural or horticultural sample, comprising an illumination unit for generating infrared light propagating towards the sample, and a

spectrometer for sensing the generated infrared light after interaction with the sample.

The infrared light propagates from the individual infrared illuminator elements 3 as transmission beams Ti, T2 towards the sample 2. After interaction with the sample 2, a reflection infrared light beam R propagates towards the spectrometer 11 of the infrared sensor unit 1. Here, the spectrometer 11 is of a diffused reflection type. Alternatively, the infrared sensor unit 1 is arranged for performing a transmission type infrared measurement. Further, a single number or a multiple number of spectrometer 11 is applied, e.g. for analyzing distinct spectra of the sensed light beam.

Advantageously, the illuminator unit includes a near infrared NIR and/or a mid infrared MIR illuminator element. NIR infrared light is within a range between circa 1200 and 2500 mm. Further, illuminator unit may include illuminator elements that are mutually identical or nearly identical. However, the infrared illuminator elements may also be different, e.g. including a first set of NIR illuminator elements and a second set of MIR illuminator elements or a single NIR or MIR illuminator element. In addition, the illuminator unit may include an additional illuminator element of another type, e.g. a visible light illuminator element such as a laser unit, e.g. for performing a raman spectroscopy measurement, and/or a source generating an X-ray beam, e.g. for performing an X-ray fluorescence measurement XRF. In principle, any source generating a beam of the electromagnetic spectrum might be included in the illuminator unit.

Further, the infrared sensor unit may include an additional sensor for receiving a reflection from the sample, after illuminating with the additional illuminator. As an example, a sensor receiving visible light and/or a sensor receiving an X-ray beam can be included, e.g. in the area surrounded by the contour of illuminator elements, e.g. close to the collimator 4.

Upon sensing the infrared signal, after interaction with the sample 2, the spectrometer 11 generates a sensor signal. Controlled by the processor 7, the sensor signal can be transmitted via the communication unit 10 as a data signal Si to a further device, e.g. for further analysis.

Optionally, the sensor unit 1 may receive, via the communication unit 10, a response signal S2, e.g. including a conformation message and/or feedback information. The data signal Si and/or S2 can be transmitted using a wired or a wireless channel.

Figure 3 shows a cross sectional schematic side view of another infrared sensor unit 1 according to the invention. Here, the infrared sensor unit 1 is provided with a front unit 20 mounted on the housing 8 of the sensor unit 1. As described above, the housing 8 accommodates various components of the sensor unit 1 such as the control unit 5, the processor unit 7, the spectrometer 11 and the communication unit 10. The front unit 20 is designed to define a sensor chamber 21 wherein the infrared

illuminator elements 3a-f and the collimator 4 are arranged.

The front unit includes a side wall 22 having a geometry and dimensions in accordance with the structure of the sensor unit housing 8, such as a cylindrical shape. A proximal end 22a of the side wall 22 is mounted to the sensor unit housing 8, preferably in a sealing manner to counteract any contamination that may occur in the sensor chamber 21.

Further, in a preferred embodiment, the front unit 20 can be removed from the housing 8, e.g. for the purpose of inspection and/or maintenance of the infrared illuminator elements 3a-f. The front unit 20 also includes a transparent window 23 mounted at a distal end 22b of the side wall 22, again preferably in a sealing manner. The transparent window 23 allows propagation of the infrared light inwardly and outwardly from and to the sensor chamber, respectively. Generally, the window 23 enables propagation of electromagnetic waves, at least in the spectra of the sensed infrared light, from the infrared illuminator elements 3a-f towards the sample and from the sample back towards the collimator 4. Further, the transparent window 23 serves as a support structure supporting the sample.

In the shown embodiment, the window 23 includes a transparent plate 24, e.g. made from a glass or transparent plastic material. As an example, the transparent plate 24 is made from borosilicate. The plate 24 may be disc-shaped or may have another shape to match with the shape and geometry of the sidewall distal end 22b. Further, the window 23 includes a scratch-resistant and transparent top layer 25 covering the exterior side of the transparent plate 24. By providing a scratch -resist ant top layer the performance of the infrared sensor unit 1 increases significantly, e.g. in terms of accuracy and reproducibility. The top layer 25 is preferably formed from a ceramic material that is extremely durable and highly transparent. By maintaining a scratch-free window 23, infrared measurements and spectroscopy in general remain accurate, also when using the infrared sensor unit 1 in less clean conditions. Alternatively, another top layer 25 is applied or the window 23 is implemented without top layer.

Preferably, the transparence of the top layer material is more than 70%, more preferably more than 85%. Further, the hardness of the top layer 25 may be more than 10 HV, Vickers Pyramic Number, preferably even more than 14 HV. As an example, the top layer material may include a ceramic such as magnesium aluminum spinel MGAI2O4.

During use of the infrared sensor unit 1, a sample 2 is placed against the exterior side of the window 23 facing away from the sensor chamber 21. Optionally, the front unit 20 is provided with a sample holder for localizing the sample 2 against the window 23. Then, measurement conditions including a measuring distance between illuminator elements 3 and collimator 4, respectively, relative to the sample 2 is defined in a reproducible manner. In the measurement configuration setup described in more detail below, an offset distance OD between the illuminator elements 3 and the sample 2 can be relatively small, e.g. smaller than 5 cm, preferably smaller than 2 cm, such as circa 15 mm or circa 10 mm or even smaller than 10 mm.

In the shown embodiment, the infrared illuminator elements 3a-f are arranged on a circumscribing contour SC around the collimator 4, such as a circle having a center point on a symmetry axis Ax of the illuminator unit. The collimator 4 is coaxially placed on the symmetry axis Ax and aligned therewith. Further, also the orientation of the infrared illuminator elements 3 is symmetrically with respect to the symmetry axis Ax. Each infrared beam B generated by the individual infrared illuminator elements 3 is focused to a sample area, also called central area C that is traversed by the symmetry axis Ax, on the exterior side of the window 23, in order to optimize the amount of infrared light illuminating the sample 2. The exterior side of the window 23 faces away from the sensor chamber 21.

The infrared illuminator elements have a source element 31 and a reflector element 32. The source element 31 is localized on a concave side of the reflector element 32, preferably in or close to a focus point thereof, so that the reflector element 32 directs the infrared light generated by the source element 31 into a focused beam B that can be a parallel or nearly parallel beam. The reflector element 32 may have an elliptic or parabolic profile, or another tapered profile. Further, the reflector elements 32 have a tilted orientation with respect to the symmetry axis Ax of the illuminator unit.

Preferably, the orientation of the symmetry axis of the reflector elements 32 that mainly coincides with the bundle axis Bx of the focused beam B is such that a maximum amount of infrared light is directed to the central area C while the collimator 4 receives a minimum amount of so- called mirror reflection. Preferably, the measurement setup has been arranged such that a maximum amount of secondary reflected infrared light is received by the collimator, i.e. infrared light that has been reflected by the sample but is no mirror reflection. The secondary reflected infrared light generally has a scattered or diffused character and may propagate in various directions, i.e. the angle of incidence is not necessary equal to the angle of reflection.

In Fig. 3 an incident beam B having a direction Bx is shown generating a mirror reflection beam MB having a direction MBx that is symmetric with respect to the symmetry axis Ax of the illuminator unit, and generating a secondary reflected beam SB having various directions SBx. When propagating through the window 23 the infrared light is refracted depending on the refraction index profile of the material in the window 23.

In practice, the illuminator elements can be oriented such that an angle 6 between the symmetry axis of the reflector elements 32, mainly coinciding with the incident beam axis Bx, with respect to the axis of symmetry Ax of the illuminator unit is set in a range between circa

45° - 50 °, e.g. 48 °.

The collimator 4 has an aperture or opening angle defining a cone CC wherein reflection beams from different directions can be received. The aperture a is e.g. 45°. In the shown embodiment, the illuminator elements 3 are located close to but outside the cone CC in order to maximize

illumination of the sample while minimizing any interaction with reflected beams to be received by the collimator 4.

Optionally, the angular position of the infrared illuminators on the surrounding contour is selected such that a first illuminator element is not centered in a mirror reflection beam MB of second illuminator element.

By providing an optimized location and orientation of the illuminator elements the offset distance between the illuminator elements 3 and the sample 2 can be extremely small, also contributing in optimizing the amount of infrared light that illuminates the sample 2. Further, a relatively compact infrared sensor unit can be obtained.

Optionally, other sensor elements are integrated in or on the infrared sensor unit 1, such as an EC sensor or a temperature sensor.

Sensor probes of an EC sensor can e.g. be mounted near the periphery of the window. By performing simultaneous measurements of various parameters with a single device, a more reliable and reproducible measurement data set is obtained, because obtained from a sample under the same circumstances.

Figure 4 shows a flow chart of an embodiment of a method according to the invention. The method is used for performing an infrared measurement on an agricultural or horticultural sample such as plants e.g. as grass or corn, or soil. The method comprises a step of providing 110 an infrared sensor unit 1 according to any of the claims 1-10, and a step of tuning 120 the amount of infrared light generated by the illumination unit such that an amount of infrared light sensed by the spectrometer 11 is within a measurement range of the spectrometer.

The method of performing an infrared measurement can be facilitated using dedicated hardware structures, such as computer servers. Otherwise, the method can also at least partially be performed using a computer program product comprising instructions for causing a processor of a computer system or a control unit to perform a process including at least one of the method steps defined above. All (sub)steps can in principle be performed on a single processor. However, it is noted that at least one step can be performed on a separate processor. A processor can be loaded with a specific software module. Dedicated software modules can be provided, e.g. from the Internet.

The invention is not restricted to the embodiments described herein. It will be understood that many variants are possible.

In principle, also another number of infrared illuminator elements can be applied, e.g. four or ten infrared illuminator elements. Alternatively, a single infrared illuminator element can be applied, the element being controlled so as to tune the amount of generated infrared light.

In order to operate properly, the infrared sensor unit may function as an autonomous device including additional components such as a power supply, or as a supplementary device operating in concert with another device such as a mobile electronic communication device.

In addition, the illumination unit may be calibrated, preferably periodically, e.g. using a calibration reflection measurement. Then, the amount of infrared light that is generated by the illumination unit can accurately be set.

Further, the infrared sensor unit can be applied for measuring physical, chemical and/or biological parameters for analysing agricultural and/or horticultural sample types or other sample types, including plastic material, oil and/or gas, pharmaceutical substances and biomaterial, e.g. in health care applications.

These and other embodiments will be apparent for the person skilled in the art and are considered to fall within the scope of the invention as defined in the following claims. For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments. However, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.

Claims

1. An infrared sensor unit for performing an infrared measurement on an agricultural or horticultural sample, comprising an illumination unit for generating infrared light propagating towards the sample, a collimator for receiving the generated infrared light after interaction with the sample, and a spectrometer sensing said received infrared light, the collimator forwarding the sensed infrared light towards the spectrometer, wherein the illumination unit includes a multiple number of infrared illuminator elements and a control unit for tuning the amount of infrared light generated by the infrared illuminator elements,

the infrared sensor unit further comprising a housing for accommodating the illumination unit and the spectrometer therein or thereon,

the infrared sensor unit also comprising a front unit mounted on the housing defining a sensor chamber wherein the infrared illuminator elements and the collimator are arranged, the front unit including a transparent window allowing propagation of infrared light inwardly and outwardly from and to the sensor chamber, respectively,

wherein the infrared illuminator elements are arranged on a circumscribing contour around the collimator, each infrared illuminator element including a source element and a reflector element directing infrared light from the source element as a focused beam towards a sample area on the exterior side of the window,

wherein the control unit is arranged to tune the amount of generated infrared light such that an amount of infrared light sensed by the

spectrometer is within a measurement range of the spectrometer.

2. An infrared sensor unit according to claim 1, wherein the control unit is arranged for switching the amount of infrared light between a predefined multiple number of discrete infrared light levels.

3. An infrared sensor unit according to claim 2, wherein a pre-defined discrete infrared light level is associated with a selected agricultural or horticultural sample class.

4. An infrared sensor unit according to claim 1, 2 or 3, wherein the illumination unit includes a multiple number of infrared illuminator elements.

5. An infrared sensor unit according to claim 4, wherein the control unit is arranged for varying the amount of infrared light of a subset of infrared illuminator elements for tuning the overall amount of infrared light generated by all infrared illuminator elements.

6. An infrared sensor unit according to claim 4 or 5, wherein the collimator is surrounded by the multiple number of infrared illuminator elements and wherein the illuminator elements are mainly evenly

distributed in a circumferential direction.

7. An infrared sensor unit according to any of the preceding claims, wherein the measurement is of a diffused reflection type.

8. An infrared sensor unit according to any of the preceding claims, wherein the illuminator unit includes a near infrared and/or mid infrared illuminator element.

9. An infrared sensor unit according to any of the preceding claims, wherein the illuminator unit includes a visible light illuminator, a laser type illuminator element and/or an X-ray source.

10. An infrared sensor unit according to any of the preceding claims, further comprising a transmission unit for transmitting measurement data to a further unit.

11. An infrared sensor unit according to any of the preceding claims, wherein the window is provided with a scratch-resistant top layer formed from a ceramic material that is extremely durable and highly transparent.

12. An infrared sensor unit according to claim 11, wherein the top layer includes magnesium aluminum spinel MGAI2O4.

13. An infrared sensor unit according to any of the preceding claims, wherein the reflector elements are directed such that a maximum amount of infrared light is directed to the sample area while the collimator receives a minimum amount of mirror reflection.

14. An infrared sensor unit according to any of the preceding claims, wherein a maximum amount of secondary reflected infrared light is received by the collimator.

15. An infrared sensor unit according to any of the preceding claims, wherein the infrared illuminator elements on the circumscribing contour are arranged symmetric with respect to a symmetry axis and wherein the reflector elements are tilted with respect to said symmetry axis.

16. An infrared sensor unit according to any of the preceding claims, comprising other sensor elements such as an EC sensor and/or a

temperature sensor.

17. A method of performing an infrared measurement on an

agricultural or horticultural sample, comprising the steps of:

- providing an infrared sensor unit according to any of the preceding claims 1- 16,

- positioning a sample in the sample area on the exterior side of the window, and

- tuning the amount of infrared light generated by the illumination unit such that an amount of infrared light sensed by the spectrometer is within a measurement range of the spectrometer.

18. A method according to claim 17, further including a step of selecting an agricultural or horticultural sample class.

19. A method according to claim 17 or 18, wherein the step of tuning the amount of infrared light includes adjusting the amount of light to a predefined level associated with the selected agricultural or horticultural sample class.

20. A computer program product for controlling an infrared sensor unit according to any of the preceding claims 1-16 for performing an infrared measurement on an agricultural or horticultural sample, the computer program product comprising computer readable code for causing a processor to perform a process including the step of: