Sensor, magnetic field position measuring system and method for determining position

Abstract

A sensor (10) for a magnetic field position measuring system has at least one transparent substrate (11) that has a first side and a second side which is opposite the first side. At least one photosensor (12) using spatial resolution is arranged on the second side. At least one light source (13a-h) is arranged on at least one side. Diamonds (14) having lattice defects are arranged between the substrate (11) and the photosensor (12) and/or in the substrate (11). Alternatively, the substrate (11) is a diamond having lattice defects.

Claims

1. Sensor (10) for a magnetic field position measuring system, said sensor comprising: at least one transparent substrate (11) having a first side and a second side opposite to the first side, at least one photosensor (12) using spatial resolution arranged on the second side of the least one transparent substrate, at least one light source (13a-h) arranged on at least one side, and diamonds (14) having lattice defects arranged between the substrate (11) and the photosensor (12) and/or diamonds (14) having lattice defects arranged in the substrate (11) and/or the substrate (11) is a diamond having lattice defects.

2. The sensor (10) according to claim 1, wherein the lattice defects are nitrogen vacancy defects.

3. The sensor (10) according to claim 1 wherein the light source (13a-h) is arranged on at least one third side of the substrate (11).

4. The sensor (10) according to claim 3, wherein at least one light source (13a-h) is arranged on each third side.

5. The sensor (10) according to claim 1, wherein an optical reflection layer (15) is arranged on the first side.

6. The sensor (10) according to claim 5, wherein the optical reflection layer (15) is a side of a housing of the sensor (10).

7. The sensor (10) according to claim 6, wherein a direction of irradiation of the light source (13a-h) is angled in the direction of the first side.

8. The sensor (10) according to one of claim 5, wherein a colour filter (16) is arranged between the substrate (10) and the photosensor (12).

9. The sensor (10) according to claim 3, wherein an air gap (17) is arranged between the substrate (10) and the photosensor (12).

10. The sensor (10) according to claim 1, wherein a magnetic field generator (50) is arranged around the substrate (11).

11. The sensor (10) according to claim 1, wherein the photosensor (12) has at least one sensor element, which is selected from a series of at least 8 photodiodes, a PSD (121), a CCD camera and a CMOS camera.

12. The sensor (10) according to claim 11, wherein the photosensor (12) has a sensor element that is equipped to provide each of a first output signal (I.sub.a) and a second output signal (I.sub.b), which have a phase shift to each other which is not 0°, 180° or 360°.

13. The sensor (10) according to claim 11, wherein the photosensor (12) has several sensitive axes.

14. The sensor (10) according to claim 13, wherein the photosensor (12) has two sensor elements that are equipped to provide each of a first output signal (I.sub.a) and a second output signal (I.sub.b), which are phase shifted to each other by 180°, wherein the two first output signals (I.sub.a) have a phase shift to each other which is not 0°, 180° or 360°, wherein the sensor elements form two sensitive axes of the photosensor (12) in parallel.

15. The sensor (10) according to claim 13, wherein the two sensitive axes of the photosensor (12) are arranged orthogonally to each other.

16. The sensor according to claim 1, wherein the sensor is in a magnetic field position measuring system.

17. The sensor according to claim 16, wherein the magnetic field position measuring system has a measuring body (20) magnetised with changing polarity that faces towards the first side of the sensor (10).

18. The sensor according to claim 16, wherein the magnetic field position measuring system has a magnet (33), which is movably arranged opposite the sensor (10), wherein the sensor (10) is immovable.

19. Method for determining position by means of a magnetic field position measuring system having a sensor comprising at least one transparent substrate having a first side and a second side opposite to the first side, at least one photosensor using spatial resolution arranged on the second side of the least one transparent substrate (11), at least one light source arranged on at least one side, and diamonds having lattice defects arranged between the substrate and the photosensor and/or diamonds having lattice defects arranged in the substrate and/or the substrate is a diamond having lattice defects, the method comprising: irradiating light into the substrate (11) by means of the at least one light source (13a-h), converting fluorescent light (Φ) into at least one output signal (I.sub.a, I.sub.b) by means of the photosensor (12), and generating a position signal from the at least one output signal (I.sub.a, I.sub.b).

20. Method according to claim 19, wherein two output signals (I.sub.a, I.sub.b) of a sensor element are each added to generate the position signal.

21. Method according to claim 19, wherein a spacing between a first side of the sensor (10) and a measuring body (20) is determined from an amplitude of the output signal (I.sub.a, I.sub.b).

22. Method according to claim 20, wherein the magnetic field position measuring system has a sensor (10) wherein the two sensitive axes of the photosensor (12) are arranged orthogonally to each other, wherein a position signal is generated along the measuring body (20) from an output signal (I.sub.a, I.sub.b) of its first axis, and a position signal of a transverse offset to the measuring body (20) is generated from an output signal of its second axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Exemplary embodiments of the invention are depicted in the drawings and are explained in more detail in the following description.

[0040] FIG. 1 shows a side view of a sensor in a magnetic field position measuring system according to an exemplary embodiment of the invention.

[0041] FIG. 2 shows a schematic depiction of a PSD of a sensor according to an exemplary embodiment of the invention.

[0042] FIG. 3 shows changes in the fluorescence of a diamond and output signals of a photosensor along a section in a method according to an exemplary embodiment of the invention in two diagrams.

[0043] FIG. 4 shows an overview of two sensors in a magnetic field position measuring system according to an exemplary embodiment of the invention.

[0044] FIG. 5 shows an isometric depiction of a sensor according to an exemplary embodiment of the invention.

[0045] FIG. 6 shows an isometric depiction of a sensor according to an exemplary embodiment of the invention.

[0046] FIG. 7 shows a cross-sectional depiction of a magnetic field position measuring system according to an exemplary embodiment of the invention.

[0047] FIG. 8 shows a cross-sectional depiction of a magnetic field position measuring system according to prior art.

[0048] FIG. 9 shows a cross-sectional depiction of a magnetic field position measuring system according to an exemplary embodiment of the invention.

[0049] FIG. 10 shows a cross-sectional depiction of a magnetic field position measuring system according to another exemplary embodiment of the invention.

[0050] FIG. 11 shows an overview of a sensor according to an exemplary embodiment of the invention.

[0051] FIG. 12a, b show fluorescence spectra of diamonds with and without exposure to a microwave field in two diagrams.

EXEMPLARY EMBODIMENTS OF THE INVENTION

[0052] In a first exemplary embodiment of the invention depicted in FIG. 1, a magnetic field position measuring system that is embodied as a magnetic-coded length measuring system has a sensor 10 and a measuring body 20 magnetised with changing polarity. The sensor 10 comprises a substrate 11 having a length of 1.0 mm, a breadth of 1.0 mm and a height of 0.5 mm. The substrate 11 is a diamond having NV defects. The underside of this rectangular substrate 11 faces towards the measuring body 20 as a first side. The upper side of the substrate 11 faces away from the measuring body 20 as a second side. The four lateral surfaces of the substrate 11 represent its third sides. A photosensor 12 using spatial resolution is arranged on the second side. A light source is arranged on each of the four third sides in each case. This is depicted in FIG. 1 for three of the light sources 13a, 13b, 13c, while the fourth light source is not visible in the selected depiction. Each light source is embodied as an LED having a power of 25 mW, which emit light of a wavelength of 520 nm into the substrate 11.

[0053] The measuring body 20 has magnetisations 21 arranged with changing polarity along a direction of movement of the sensor 10. These alternatingly have a magnetic north pole 211 and a magnetic south pole 212.

[0054] The photosensor 12 is embodied as a PSD 121. This is depicted in FIG. 2. The PSD 121 has photodiodes 122 in an equivalent circuit diagram n. A reference voltage V.sub.REF abuts on these. They are connected in parallel along the direction of movement of the sensor 10 along the magnetic measuring body 20, and thus form a sensitive axis. The photodiodes are connected to two cathodes a, b on the two ends of the PSD 121 via electrical resistances 226. An electrical current I.sub.a on the first cathode a is obtained according to Formula 1:

[00001]$\begin{array}{cc}{I}_a=\underset{i=1}{\overset{n}{.Math.}}\frac{\left(n+1\right)-i}{n}.Math.I_i& \left(\mathrm{Formula}1\right)\end{array}$

[0055] I.sub.i here describes the current of the photodiodes 122 with the number i. The current I.sub.b is obtained according to Formula 2:

[00002]$\begin{array}{cc}{I}_b=\underset{i=1}{\overset{n}{.Math.}}\frac{i}{n}.Math.I_i& \left(\mathrm{Formula}2\right)\end{array}$

[0056] FIG. 3 shows that when light is irradiated into the substrate 11 by means of the light sources 13a, 13b, 13c, depending on the section s which was travelled along the measuring body 20, a fluorescence φ of the diamond results, which is detected by the PSD 121 and converted into two output signals in the form of the electrical currents I.sub.a, I.sub.b. Here the first current 1.sub.a shows a sinusoidal course and the second current I.sub.b shows a co-sinusoidal course. The two currents I.sub.a, I.sub.b are thus phase-shifted by 90°. Each of the output signals is the result of a weighted mean average of the entire light surface of the substrate 11. In this way, it has very little noise. The output signals are evaluated to a position signal by means of a transimpedance amplifier and a digital signal processing, in order thus to determine the position of the sensor 10 along the measuring body 20 and to output this to a user.

[0057] In a second exemplary embodiment of the invention depicted in FIG. 4, the sensor 10 has a substrate 11 that is not completely covered by a single PSD 121. Instead, two PSDs 121a, 121b are arranged next to each other on the substrate 11 in such a way that their sensitive axes run in parallel. The lengths of the PSDs 121a, 121b, for example of 0.7 mm each, are selected such that when the breadth of the magnetisations 21 is 1.0 mm, the two currents I.sub.a, I.sub.b of each of the PSDs 121a, 121b are phase-shifted to each other by 180°, such that in terms of amount they add up to a total current value of I.sub.tot=|I.sub.a|+|I.sub.b|, which has a signal amplitude that is twice as large as a signal amplitude of the currents I.sub.a, I.sub.b alone at every point of the section s. The two PSDs 121a, 121b are shifted against each other along their sensitive axes by a shift v, such that the two total current values I.sub.tot of the two PSDs 121a, 121b are shifted to each other by 90°. Two signal courses can thus be obtained which have the same phase shift as the two signal courses in FIG. 2, but show higher signal intensities.

[0058] The spacing between the second side of the sensor 10 and the measuring body 20 can be more than 100% of the breadth of the magnetisations 21 in all exemplary embodiments, without the functionality of the magnetic field position measuring system being compromised as a result. It is thus superior to other magnetic field position measuring systems embodied as magnetically coded length measuring systems, which use a Hall sensor, for example. In magnetic field position measuring systems of the kind of prior art, the spacing between the Hall sensor and the measuring body may not be more than 50% of the breadth of the magnetisations 21.

[0059] In a third exemplary embodiment of the invention shown in FIG. 5, a sensor 10 has a substrate 11 that consists, for example, of glass. In this exemplary embodiment too, the underside of the substrate 11 represents the first side, which is provided to face towards at least one magnet in a magnetic field position measuring system.

[0060] On the second side opposite the first side, a photosensor 12 using spatial resolution is arranged, which is embodied as a PSD. The substrate 11 is rectangular, and therefore has four further sides that are described as third sides. Four light sources 13a-d are arranged on one of these third sides. Each light source is embodied as an LED having a power of 25 mW, which emits green light of a wavelength of 520 nm into the substrate 11. Each of the light sources is here arranged such that their direction of irradiation into the substrate 11 is angled at 45° to the third side on which the light sources 13a-d are arranged. The light sources 13a-d thus irradiate light in the direction of the second side of the substrate 11 into said substrate. Diamonds 14 having NV defects are arranged in a layer on the upper side of the substrate 11, underneath the photosensor 12. A reflection layer 15 made of a metal, which represents a part of a metal housing of the sensor 10, is arranged on the first side. A colour filter 16 is arranged between the diamonds 14 and the photosensor 12, which absorbs light of a wavelength of 520 nm. It is permeable for red light, however.

[0061] When the sensor 10 is operating, the light sources 13a-d irradiate green light into the substrate 11. This hits the reflection layer 15, and is reflected by the latter in the direction of the second side, and thus in the direction of the diamonds 14. A part of the light induces the diamonds 14 to fluoresce. The remaining light hits the colour filter 16, and is absorbed by the latter. The diamonds 14 emit red fluorescent light, which passes the colour filter 16 unhindered, is received by the photosensor 12 and is converted into an electrical output signal.

[0062] A fourth exemplary embodiment of the sensor 10 according to the invention is depicted in FIG. 6. A substrate 11 that, as in the second exemplary embodiment, can for example consist of glass, also has a first side, a second side and four third sides. Several light sources are arranged on each of the third sides. This is depicted in FIG. 6 for six light sources, wherein four light sources 13a-d are arranged on one of the third sides, and two further light sources 13e-f are arranged on another of the third sides. The light sources on the remaining two third sides cannot be seen in the depiction in FIG. 6. As in the two previous exemplary embodiments of the sensor 10, the substrate 11 has a photosensor 12 using spatial resolution on its second side in the form of a PSD. A layer of diamonds 14 having NV defects is arranged on the second side of the substrate 11 such that it is between the substrate 11 and the photosensor 12. In place of the colour filter 16 according to the first exemplary embodiment of the sensor 10, an air gap 17 is arranged between the photosensor 12 and the diamonds 14.

[0063] All light sources 13a-f, which emit green light of a wavelength of 520 nm as in the first exemplary embodiment, are arranged such that they emit their light into the substrate 11 in parallel to the second side. A part of the light is here directed onto the diamonds 14 via reflections on the third side of the substrate 11. Light that does not induce the diamonds 14 to total fluorescence in the process hits the air gap 17 instead, and is thrown back into the substrate 11 via a total reflection. The fluorescent light of the diamonds 14 passes the air gap 17, however, and hits the photosensor 12. It is converted into an electrical output signal by this photosensor as in the first exemplary embodiment of the sensor 10.

[0064] FIG. 7 shows a magnetic field position measuring system in a fifth exemplary embodiment of the invention. A sensor 10 is arranged above one of the magnetised measuring bodies 20 according to the second or third exemplary embodiment in such a way that the first side of the sensor 10 faces towards the measuring body 20. The measuring body 20 here has a carrier 22 in which four magnets 21a-d are arranged. The magnets 21a-d are embodied as permanent magnets whose north poles each face towards the sensor 10. In the position depicted in FIG. 7, the first magnet 21a is not arranged under the sensor 10, and the following three magnets 21b-d are arranged under the sensor 10. The course of the fluorescence ϕ of the diamonds 14 along the section s of the sensitive axis of the photosensor 12 is depicted in a diagram. It can be seen that the fluorescence ϕ sinks at each of the positions of these three magnets 21b-d due to the influence of the magnetic field of the three magnets 21b-d on the fluorescent behaviour of the diamonds 14. If, for example, the photosensor 12 is embodied as a CMOS camera, and the measuring body 20 has an PRC code (not depicted in FIG. 7) that codifies an absolute position on a side of its material measure, then the PRC code can be read out by means of the sensor 10.

[0065] FIG. 8 shows a pneumatic cylinder 30 of a pneumatic actuator that is equipped with a conventional magnetic field position measuring system 40. The pneumatic cylinder 30 has a cylinder chamber 31 in which a piston 32 can be moved. The piston 32 has a magnet 33 for determining its position. This magnet has a north pole 34 and a south pole 35 along its direction of movement. The conventional sensor 40 is arranged along the entire length of the cylinder chamber. The sensor has 8 Hall sensors 41a-h distributed over this length, by means of which the position of the magnet 33, and thus the position of the piston 32, can be determined. The conventional sensor 40 does not enable a continuous position measurement here, however, but only the recognition of that position of the piston 32 in which one of the Hall sensors 41a-h is located.

[0066] In a sixth exemplary embodiment of the invention, it is provided that the conventional sensor 40 of the magnetic field position measuring system is replaced by a sensor 10 according to the second or third exemplary embodiment. This is depicted in FIG. 9. It is thus possible to continually determine a position of the piston 32. The fluorescent behaviour of the diamonds 14 is influenced by the magnets 33 in characteristic manner as depicted in a diagram in FIG. 9. A reduction of the fluorescence ϕ occurs at the position of the magnet 33 along the section s of the sensitive axis of the photosensor 12. Two local minima here occur, which correspond to the particular position of the north pole 34 and the south pole 35 of the magnet 33.

[0067] In a seventh exemplary embodiment of the invention, it is provided that the polarisation of the magnet 33 is turned by 90° relative to the sixth exemplary embodiment. In this way, only one pole 35 faces towards the sensor 10. In this exemplary embodiment too, it is possible to continually determine the position of the piston 32.

[0068] A sensor 10 according to an eight exemplary embodiment of the invention is depicted in FIG. 11. This sensor has a substrate 11 that consists, for example, of polycarbonate, in which diamonds having a number-average diameter of 25 nm are distributed. The diamonds have NV defects. The first side, the second side and the third sides of the substrate 11 are defined in the same manner as in the previous exemplary embodiments. A photosensor 12 using spatial resolution embodied as a PSD is arranged on the second side, and two LEDs are arranged as light sources 13a-h on each of the third sides in each case. The first side is provided for the purpose of facing towards a magnetic measuring body. The light sources 13a-h are surrounded by a magnetic field generator 50 in the form of a coil. Two interrupted coils 60a, 60b are arranged between the coil 50 and the light sources 13a-h. The coil 50 generates a magnetic field of 7.5 gauss, for example, by generating microwaves having a frequency of 2.87 GHz, for example.

[0069] FIG. 12a shows a fluorescent signal of the substrate 11, which is depicted without influence of an external magnetic field, wherein the fluorescence ϕ is applied over the frequency v. When the microwave source is switched on, a splitting up of the fluorescent signal at 42 MHz occurs such that the fluorescent signal results according to FIG. 12b.