CN111587364A

CN111587364A - Optical sensor module for spectral measurements

Info

Publication number: CN111587364A
Application number: CN201880085890.7A
Authority: CN
Inventors: B·勒泽纳; M·贝德加; V·克劳斯
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-01-08
Filing date: 2018-12-20
Publication date: 2020-08-25
Also published as: WO2019134844A1; DE102018200162A1; KR20200103092A

Abstract

An optical sensor module for analyzing a fluid or an object is disclosed, having at least one beam source for generating an electromagnetic beam of a wavelength range and for emitting the electromagnetic beam in the direction of the fluid or object to be examined; at least one detector for receiving the beam reflected on the fluid or the object and converting the received beam into an electrical measurement signal; at least one pedestal for positioning and orienting the at least one beam source and the at least one detector on a circuit board; at least one signal processing unit for amplifying and processing the electrical measurement signals of the at least one detector, wherein the at least one beam source can be positioned on the circuit board parallel or inclined to the at least one detector by means of the at least one pedestal.

Description

Optical sensor module for spectral measurements

Technical Field

The present invention relates to an optical sensor module for analyzing a fluid or an object according to the preamble of claim 1.

Background

Optical sensors have been put to use in a variety of applications. For example, an NDIR (non-dispersive infra-red) detector can determine the CO in the ambient air₂Content, or moisture content in a gas or other material. Such sensors can be used in particular for detecting specific material properties and mixing ratios of a medium (for example gaseous, solid or liquid) and for performing spectroscopic analysis processes. One of the possible applications of miniaturized optical sensors is the monitoring of washing process parameters or drying process parameters.

The sensor may for example perform a reflection measurement. In such measurement methods, the detector and emitter are typically located on the same side of the measurement section, and the IR radiation produced by the emitter is directed through an optical path that may vary over time, for example because the sensor-to-measurement sample separation may vary.

The basis of the optical sensor spectral analysis process is a uniform spectral response, which may be composed of multiple wavelengths. When building a sensor in one plane (e.g. on a circuit board), in order to obtain a uniform spectral response, challenges such as optimal bunching of radiation are created.

There are also many such applications, particularly in reflectance measurements: during the measurement, the interval between the object and the sensor module may vary. Small deviations in the arrangement of the emitter and detector, and in the emission characteristic of the emitter, can already have a negative effect on the spacing dependence of the sensor, so that the working range of the sensor can be severely limited in high-precision measurement tasks.

Disclosure of Invention

The object on which the invention is based can be seen as providing an optical sensor module which can be produced in a technically simple manner and has improved spectral homogeneity.

This object is achieved by the corresponding subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the respective dependent claims.

According to one aspect of the present invention, an optical sensor module for analyzing a fluid or an object is provided. The sensor module has at least one beam source for generating an electromagnetic beam of a wavelength range and emitting said electromagnetic beam in the direction of the fluid or object to be examined. Furthermore, the sensor module has at least one detector for receiving the beam reflected on the fluid or the object and converting the received beam into an electrical measurement signal. The sensor module has at least one base (socket) for positioning and orienting the at least one beam source and the at least one detector on the circuit board. At least one signal processing unit of the sensor module is used to amplify and process the electrical measurement signals of the at least one detector. According to the invention, the at least one beam source can be positioned on the circuit board parallel to or inclined to the at least one detector by means of the at least one base.

The at least one beam source can be, for example, at least one infrared LED or an infrared laser.

In order to be able to realize the optical sensor design as cost-effectively as possible, it is advantageous to miniaturize it and to design the optical path simply by appropriately selecting the design parameters, material parameters and optical components. SMD mountable parts (SMD Best bar) or parts called through-holes (through-holes) are generally used for through-hole mounting (durchteckmontage) to achieve miniaturization. Thus, all necessary components must be arranged as far as possible in one plane, for example on a circuit board or in a TO unit. With this configuration, the assembly of the components can be performed very quickly and at low cost.

A mechanical structure for accommodating the at least one detector and the at least one beam source can be realized by the base, which mechanical structure can be arranged on the circuit board. Simple and cost-effective beam guidance or beam bunching can therefore be achieved by suitable positioning of the optical components relative to one another. In addition to the precise orientation of the optical components of the sensor module, the sensor module can also be installed or produced in a technically simple manner. Furthermore, the at least one detector can be positioned or oriented relative to the beam source by means of the base such that scattered light is reduced or avoided.

According to an embodiment of the optical sensor module, the detector may be centrally positioned in the at least one base between the at least two beam sources. The spectral homogeneity of the sensor module can be optimized by the opposing arrangement of at least two beam sources having equal wavelength ranges. In particular, deviations in the wavelength range of the beam source can be compensated for thereby. This results in an improved distribution of the spectral components of the generated radiation in the measurement space in which the sample or object is located and a more uniform spectral distribution can be achieved.

According to a further embodiment of the optical sensor module, the beam source may be centrally positioned between the at least two detectors in the at least one base. As an alternative to arranging the detectors between a plurality of beam sources, a broadband beam source or emitter may be used in combination with a plurality of detectors in order to detect a specific spectral range. Deviations of the emission characteristic of the beam source can thereby be compensated for by a larger detectable wavelength range of a plurality of identical or different detectors.

According to a further embodiment of the optical sensor module, the at least one base is rotationally symmetrically shaped, wherein the at least one base has at least one receiving portion (fasung) for receiving the detector and at least one receiving portion for receiving the beam source. By introducing a receptacle (Aufnahmen) or a receptacle in the mount, the optical component can be used in the mount in a form-locking manner. In particular, in the state of use in the receptacle, the at least one beam source and the at least one detector can be optimally oriented optically.

According to a further embodiment of the optical sensor module, the at least one base at least partially shields the at least one detector arranged in the receiving portion from the electromagnetic beam. Undesired cross-talk from the beam source to the at least one detector or scattered light in the housing can thereby be reduced or prevented. The usable dynamic range of the sensor can thus be enlarged. Alternatively or additionally, the base can promote multiple reflections on the respective reflecting surface in the region of the receptacle of the at least one detector, and thus improve the performance of the sensor module.

According to a further embodiment of the optical sensor module, the optical sensor module has at least one spacing sensor for determining the spacing of the at least one detector from the object.

By means of the additional sensor, a distance measurement can be carried out, which can be used to compensate for the existing spacing dependency of the sensor module. The working range of the sensor module can be extended.

According to a further embodiment of the optical sensor module, the at least one signal processing unit has an offset tracking device (offsetnachhufung) of the electrical measurement signal and/or a variable amplification device of the electrical measurement signal. The at least one signal processing unit can thus have signal conditioning means and signal processing means, whereby the sensor module can be adapted to the application-specific requirements.

According to a further embodiment of the optical sensor module, the optical sensor module has a temperature sensor for performing temperature compensation. In this way, the thermal influence on the emission characteristics of the emitter or of the at least one detector and the thermal influence on the material to be examined can be taken into account when the measurement signals of the at least one detector are evaluated by the at least one signal processing unit. Temperature-dependent influences in the context of processing the measurement signal can be compensated in particular by the additional temperature information.

According to a further embodiment of the optical sensor module, the at least one beam source, the at least one detector, the at least one pedestal, the at least one signal processing unit and the at least one energy supply are connected to the at least one beam sourceThe unit is arranged in a housing which can be sealed in a fluid-tight manner (fluidichtverschlie β bar.) preferably, the housing can be sealed by a cover and can be closed off from the environment by sealing means (for example, O-rings)

Or painted metal. The sensor module can therefore also be used in a wet environment, wherein the components of the sensor module are arranged in a protected manner in the housing.

According to a further embodiment of the optical sensor module, the housing has at least one window for transmitting an electromagnetic beam of at least one beam source. Thus, the electromagnetic beam generated by the at least one beam source may be emitted from the housing. In this case, the optical components of the sensor module can be arranged in the housing in a protected manner.

According to a further embodiment of the optical sensor module, the at least one detector can be positioned directly on the at least one window by means of at least one pedestal arranged in the housing. The at least one detector can be positioned in the housing by means of the at least one base such that the detector is arranged directly on the window of the housing. In particular, the detector can be positioned in an extended manner perpendicular to the plane of the window, whereby reflections can be reduced. Depending on the configuration of the at least one base, the receptacle of the detector can shield the detector on the circumferential side (umfangsseiting) with respect to the window and thus protect the detector from scattered light from the housing.

The detector according to the invention is particularly suitable for use in a washing machine or dishwasher.

Drawings

Preferred embodiments of the invention are explained in more detail below on the basis of a highly simplified schematic drawing. Shown here are:

fig. 1a shows an exploded perspective view of a base of a sensor module according to a first embodiment of the invention with a plurality of beam sources and one detector;

fig. 1b shows an exploded perspective view of a base of a sensor module according to a second embodiment of the invention with a plurality of beam sources and one detector;

fig. 2 shows a schematic view of illumination by a sensor module according to a second embodiment;

fig. 3a shows an exploded perspective view of a sensor module according to a first embodiment of the invention;

fig. 3b shows an exploded perspective view of a sensor module according to a second embodiment of the invention;

fig. 4 shows a schematic diagram of a circuit diagram of a signal processing unit of a sensor module according to an embodiment of the invention;

fig. 5 shows a schematic view of a sensor module according to a third embodiment of the invention.

In the figures, identical structural elements have identical reference numerals, respectively.

Detailed Description

Fig. 1a shows an exploded perspective view of a base 1 with a plurality of beam sources 2 and one detector 4 of a sensor module 6 according to a first embodiment of the invention.

The base 1 is rotationally symmetrical and has six receptacles 8 for receiving in each case one beam source 2. The receptacle 8 for receiving the beam source 2 is arranged around the receptacle 10 for receiving the detector 4. Furthermore, the receptacle 10 for receiving the detector 4 is arranged offset from the receptacle 8 of the beam source 2 in the emission direction of the beam source 2.

According to a first embodiment of the sensor module 6, the beam source 2 and the detector 4 can be positioned in parallel orientation to one another in the base 1 or in the

receptacles

8, 10 of the base 1.

The beam source 2 is here, for example, an infrared LED with a diameter of 3mm or 5 mm. The beam source 2 may emit an electromagnetic beam in the wavelength range of 800nm to 1000 nm.

The base 1 is flat on the end opposite the receptacle 10 of the detector 4, so that the base 1 can be arranged on a planar circuit board in a form-fitting manner. The base 1 has a through-opening for the beam source 2 and the contacting of the detector 4, which through-opening is guided through the base 1 in a direction opposite to the beam direction of the beam source 2. The contacts which are guided through the base 1 can therefore be oriented relative to one another and positioned optimally on the circuit board.

Fig. 1b shows an exploded perspective view of a base 1 with a plurality of beam sources 2 and detectors 4 of a sensor module 6 according to a second embodiment of the invention. In contrast to the first exemplary embodiment of the sensor module 6, the beam source 2 is arranged at an angle to the detector 4. The beam source 2 is in particular oriented obliquely or at an angle to the axis of rotation of the rotationally symmetrical base 1. This can be achieved by means of a correspondingly angled receptacle 8 of the beam source 2. As a result, an overlap region of the electromagnetic beams generated by the beam source 2 can be formed, which forms a uniform emission region of the beam source 2 and can compensate for manufacturing tolerances of the beam source 2.

Fig. 2 shows a schematic view of the illumination by the sensor module 6 according to the second embodiment. In particular a cross section through the base 1 is shown. The arrangement of the beam source 2 at an angle to the detector 4 and the course of the connection of the beam source 2 to the detector 4 are shown here.

By the offset arrangement of the detector 4 relative to the beam source 2 in the base 1, the detector 4 can be positioned directly on the window 12 of the sensor module 6. The detector 4 is arranged in the base 1 in such a way that a wall 11, which surrounds the receptacle 10 of the detector 4, can protect and shield the detector 4 from scattered light. Preferably, the base 1 is positioned on the window 12 of the sensor module 6 in such a way that there is no spacing or only a minimal spacing between the wall 11 and the window 12.

The sensor module 6 emits an electromagnetic beam generated by the beam source 2 through the window 12. The overlap region a is generated by a plurality of beam sources 2 and is configured as the sum of the electromagnetic beams generated by all beam sources 2. Thereby, manufacturing tolerances of the beam source 2 can be compensated.

Optionally, it can be provided that the base 1 is configured to be movable, so that it can be directed to at least one individual beam source 2 and/or detector 4. For this purpose, actuators can be provided, which are assigned to the beam source 2 or to the detector. Furthermore, it may optionally be provided that the base 1 is formed in multiple parts, wherein one part of the base 1 can be moved relative to the other part. By means of this multipart configuration, the beam source 2 or the detector 4 can be directed to different elements, respectively. In a special configuration, each part of the multipart configuration of the base 1 is equipped with its own actuator, so that each part can be manipulated and positioned independently of one another. One or more actuators can be controlled by the signal processing unit 26, for example, as a function of the measurement signals of the detector 6.

Fig. 3a and 3b show exploded perspective views of a sensor module 6 according to a first and a second embodiment of the invention. The sensor module 6 has a housing 14, which can be sealed in a fluid-tight manner by a sealing ring 16 by means of a cover 18. For using the window 12, the cover 18 has external insulation means

The generated electromagnetic radiation may be emitted from the housing 14 of the sensor module 6 through the window 12. The window 12 can be positioned on the cover 18 by means of the sealing ring 16. For example, the window 12 may be glued into a recess in the cover 18.

Furthermore, the sensor module 6 has a first printed circuit board 20. The base 1 is fixed to the first circuit board 20 by a screw connection portion 22. In this case, the beam source 2 and the detector 4 can be clamped or soldered to the printed circuit board 20 in an electrically conductive manner.

Furthermore, the sensor module 6 has a second printed circuit board 24, which is electrically conductively connected to the first printed circuit board 20. On the second printed circuit board 20, for example, the current supply of the sensor module 6 and at least one signal processing unit 26 for evaluating the electrical signals of the detector 4 are arranged. The current supply device can be configured, for example, by a battery or an external current connection.

The respective components 18, 1, 24 can be fixed to one another and/or to the housing 14 in a force-fitting manner by means of the threaded connection 28.

Fig. 4 shows a schematic diagram of a circuit diagram of the signal processing unit 26 of the sensor module 6 according to an embodiment of the invention. An exemplary circuit of the signal path of the electrical measurement signal generated by the probe 4 is depicted here, among others.

A detector 4 is shown with a transimpedance amplifier 30 connected downstream. The transimpedance amplifier 30 may be arranged here, for example, on the first printed circuit board 20 and may transmit the amplified measurement signal of the detector 4 via corresponding unnumbered data lines to the second printed circuit board 24.

The differential amplifier 32 may be applied, for example, on the second circuit board 24. By means of the differential amplifier 32, offset corrections can be carried out on the different measurement signals of the different beam sources 2 by means of the digital-to-analog converter 34 of the signal processing unit 26. The measurement signal can thus be converted into the linear region of the subsequent circuit element.

Here, a second operational amplifier 36 is arranged on the second circuit board 24. The second operational amplifier 36 is capable of variably amplifying the signal processed by the signal processing unit 26. The use of offset tracking of the differential amplifier 32 and variable amplification in different detection regions, for example in the case of very weak, humidity-dependent signals, is particularly advantageous. Within the detection region, the measurement signal can be tracked more precisely by means of the digital-to-analog converter 34 and the amplification can be switched to a higher level.

Fig. 5 shows a schematic illustration of a sensor module 6 according to a third embodiment of the invention. Unlike the previously described embodiments of the invention, the sensor module 6 has a temperature sensor 38 and a spacing sensor 40. In a further evaluation by the signal processing unit 26, temperature-defined deviations in the emission characteristics of the object 42, the beam source 2, the detector 4 or the fluid to be examined can be taken into account by the temperature sensor 38.

Here, the spacing sensor 40 may be an optical or ultrasonic-based sensor. The interval dependency of the measurement signal reflected by the object 42 can be compensated for by the interval sensor 40.

Depending on tolerances on the system and on the component plane, incorrect adjustment of the optical elements (fehljusticeng) may occur with respect to one another. These mis-adjustments are important for spectroscopic applications, where at least one wavelength of the measurement channel and a wavelength of the reference channel are usually compared with each other. Since these mis-adjustments may produce sensor-specific interval correlations, the interval correlations may be compensated for by using the interval sensor 40.

Since the distance between the

sensor

4, 6 and the object 42 may change, in particular when the measurement is carried out by the sensor module 6 in the reflection mode, the following possibilities are achieved by integrating the distance sensor 40 for the distance measurement into the sensor module 6: the interval dependence of the measurement signal is compensated.

An overview of all relevant components of the sensor module 6 according to the third embodiment of the invention is also shown in fig. 5.

Another embodiment relates to a method for evaluating the electrical measurement signals received by the detector 4, which method can be carried out, for example, in the signal processing unit 26. The measurement signals are processed in such a way that the signal processing unit 26 displays one or more signals as a function of the intensity of the radiation reflected back (zurr ü ckfallen) from the at least one beam source 2 onto the detector 4. It is also conceivable for the signal of the signal processing unit 26 to be generated as a function of the measured variables of the temperature sensor 38 and/or of the spacing sensor 40.

Claims

1. An optical sensor module (6) for analyzing a fluid or an object (42) has

At least one beam source (2) for generating an electromagnetic beam of a wavelength range and for emitting said electromagnetic beam in the direction of a fluid or object (42) to be examined,

at least one detector (4) for receiving the beam reflected at the fluid or the object (42) and for converting the received beam into electrical measurement signals,

at least one base (1) for positioning and orienting the at least one beam source (2) and the at least one detector (4) on a circuit board (20),

at least one signal processing unit (26) for amplifying and processing the electrical measurement signals of the at least one detector (4),

characterized in that the at least one beam source (2) can be positioned on the circuit board (20) parallel to or inclined to the at least one detector (4) by means of the at least one base (1).

2. Sensor module according to claim 1, wherein the detector (4) is positionable centrally in the at least one base (1) between at least two beam sources (2).

3. Sensor module according to claim 1, wherein the beam source (2) is positionable centrally in the at least one base (1) between at least two detectors (4).

4. Sensor module according to one of claims 1 to 3, wherein the at least one base (1) is shaped rotationally symmetrically, wherein the at least one base (1) has at least one receiving portion (10) for accommodating a detector (4) and at least one receiving portion (8) for accommodating a beam source (2).

5. Sensor module according to one of claims 1 to 4, wherein the at least one base (1) at least partially shields the at least one detector (4) arranged in the receiving portion (10) from electromagnetic beams.

6. The sensor module according to one of claims 1 to 5, wherein the optical sensor module (6) has at least one spacing sensor (40) for determining a spacing of the at least one detector (4) from the object (42).

7. Sensor module according to one of claims 1 to 6, wherein the at least one signal processing unit (26) has an offset tracking device (32) of the electrical measurement signal and/or a variable amplification device (36) of the electrical measurement signal.

8. The sensor module according to any one of claims 1 to 7, wherein the optical sensor module (6) has a temperature sensor (38) for performing temperature compensation.

9. Sensor module according to one of claims 1 to 8, wherein the at least one beam source (2), the at least one detector (4), the at least one base (1), the at least one signal processing unit (26) and the at least one energy supply unit are arranged in a fluid-tight sealable housing (14, 18).

10. Sensor module according to one of claims 1 to 9, wherein the housing (14, 18) has at least one window (12) for transmitting an electromagnetic beam of the at least one beam source (2).

11. The sensor module according to claim 9, wherein the at least one detector (4) is positionable directly on the at least one window (12) through the at least one base (1) arranged in the housing (14, 18).

12. Method for the analytical processing of sensor signals of a sensor module according to one of claims 1 to 11, wherein detector signals of a detector (4) are amplified and processed in dependence on electromagnetic beams generated by at least one beam source (2) and emitted in the direction of a fluid or object (42) to be examined, reflected back to the detector (4).

13. Method according to claim 12, characterized in that the sensor signal is modified as a function of the measured variable of the temperature sensor (38) and/or of the spacing sensor (40).