DE10005227A1 - Opto-electronic formed as reflection light scanner which receives light pulses whose polarizing direction depends on position of object; uses light pulses from transmitter directed to receivers, which on form difference signal - Google Patents

Abstract

Light pulses (4) from transmitter (2), are directed to a receivers (5,6), which on form a difference signal Ud or signal ratio as a measure for the relative position and/or rotational speed of an object (13).

Description

The invention relates to an optoelectronic device according to the Ober Concept of claim 1.

Such optoelectronic devices can be used in particular as a camera systems, preferably video cameras. The transmitter forms in this case a lighting system, the transmitted light pulses in the form of Flashes of light illuminate the object to be measured. The recipient is in front preferably formed by a matrix-shaped CCD element. The one with the Image information registered in the receiver is stored in an evaluation unit evaluated.

By means of the optoelectronic device, an image of the entire upper area structure recorded and evaluated. In particular, from the off pending image information the position of the object be determined. Continuous detection of the object can also a change in position, in particular a rotation of the object can be detected.

The disadvantage here, however, is the great structural complexity of the optoelectronics cal device as well as a high effort in the evaluation the image information. Finally, such camera systems also require a considerable space requirement, so that objects that are difficult to access, such as for example drive shafts in motors such optoelectronic Vorrich can not be used or only with considerable restrictions.

Another disadvantage is that objects that rotate at high speeds of such camera systems are no longer detectable.  

In principle, you can avoid such restrictions on the object Optical markings are attached, which are then used with the camera system be recorded. However, the disadvantage here is that only one object limited number of optical markings can be attached, so that when determining the angular position of the object only a limited up solution is achievable.

The invention has for its object an optoelectronic device of the type mentioned at the outset so that the opening is as simple as possible construction and small size, the most accurate determination of the speed and / or the angular position of an object can be detected.

The features of claim 1 are provided to achieve this object. Advantageous embodiments and expedient further developments of the Erfin tion are described in the subclaims.

The optoelectronic device according to the invention is a reflection light push button trained, these either two transmitters and a receiver or has a transmitter and two receivers.

The alternating transmission light emitted by the transmitter or transmitters impulses are applied to a reflector with an upstream polarization film ter performed, which are attached to the object. The send reflected on the reflector light impulses hit the receiver or the as received light impulses Receiver.

In the first embodiment of the invention, there are two transmitters each a downstream polarization filter is provided, the polarization Filters have different polarization directions. The recipient is in this case no polarization filter upstream.  

In the second embodiment, a transmitter is provided which is non-polar transmitted light pulses reflected. The emp reflected by the reflector Catch light impulses hit two receivers, each receiver one Polarization filter is arranged upstream. The polarization filters instruct different directions of polarization.

From the transmitted light pulses of the two transmitters, which are guided as received light pulses to the receiver or from the received light pulses, which strike the two receivers, a quotient signal or a differential signal U _d and possibly a sum signal U _{s is} generated, which is a measure of the angular position and / or form the speed of the object.

The basic idea of the invention is that a reflector on the object is arranged with an upstream polarization filter, so that at this reflected received light pulses a certain direction of polarization point. This direction of polarization depends on the current angular position of the Object.

Accordingly, in the first embodiment of the invention for different angular positions of the object the po emitted by the transmitters larized transmitted light pulses with different intensities as reception light pulses reflected, because their polarization directions are different.

Accordingly, in the second embodiment of the invention Outputs of the receivers for different angular positions of the object below receive different amplitudes of the received signals because the polarization fil ter, which are upstream of the receivers, again different polarities have directions.

In any case, the difference signal U _d or the quotient signal gives a measure of the angular position and thus also the speed of the object.

In addition to the difference signal U _d , the sum signal U _s is preferably also formed. A level-independent signal is then preferably obtained by forming the quotient U _d / U _s , which provides a measure of the angle of the object.

An essential advantage of the device according to the invention is that that it has a simple and space-saving structure. In addition, the Evaluation of the received signals to determine the angular position without large Computational effort feasible.

It is also advantageous that the attachment of the reflector to the object as well as the alignment of the optoelectronic device are not major Accuracy requirements must be made. On the one hand, this makes it easier the installation of the device according to the invention. The Vorrich is also robust against angular and positional tolerances, which means a high ver availability of the device is achieved. Finally, with the fiction device not only exactly determines the angular positions of objects be measured, but also high speeds of objects.

The invention is explained below with reference to the drawings. It demonstrate:

Fig. 1: Block diagram of one embodiment of erfindungsge MAESSEN optoelectronic device.

Fig. 2: Structure of the optical components of the apparatus of FIG. 1.

Fig. 3: First example of the waveforms of the pending receive signals at the outputs of the receivers and the resulting ge sum and difference signals U _s and U _d .

Fig. 4: Second example of the waveforms of the pending receive signals at the outputs of the receivers and the resulting ge sum and difference signals U _s and U _d .

. FIG. 5: arrangement of the apparatus of Figure 1 for measuring the speed of a drive shaft.

FIG. 6a:. Arrangement of the apparatus of Figure 1 for measuring the speed of a servo drive.

Fig. 6b: waveform of the difference signal U _d according to the arrangement of Fig. 6a.

FIG. 7 shows arrangement of the apparatus of Figure 1 for determining the position of goods in transit..

Fig. 8: Arrangement of the device of FIG. 1 on a bending spring part.

. FIG. 9: assembly of devices according to Figure 1 for Torsionsmes solution to a drive shaft.

Fig. 10: Arrangement of devices according to Fig. 1 for measuring the slip on a belt drive.

Fig. 1 is a block diagram showing an embodiment of the fiction, modern optoelectronic apparatus 1.

The optoelectronic device 1 is designed as a reflection light scanner and has a transmitter 2 , which emits light pulses 3 with a predetermined pulse-pause ratio. The transmitter 2 is preferably formed by a light emitting diode.

In addition, the optoelectronic device 1 has two receiving light pulses 4 receiving receivers 5 , 6 , each with an upstream polarization filter 7 , 8 .

The transmitted light pulses 3 emitted by the transmitter 2 are guided to a reflector 9 . The reflector 9 consists of a reflective film 10 , which a polarization filter 11 is arranged upstream. In addition, the reflector has a holder 12 in which the reflective film 10 and the polarization filter 11 are mounted. In addition, the holder 12 is used for fastening to the surface of an object 13 , the angular position or the rotational speed of which is to be determined by means of the optoelectronic device 1 .

The reflector 9 can be attached to the object, for example, by means of a permanent magnet. Alternatively, the reflector 9 can be glued to the surface of the object.

The transmitted light pulses 3 are reflected on the reflector 9 and strike the receiver 5 , 6 as received light pulses 4 . As a result, receive signals U _e1 , U _{e2 are} generated at the outputs of the receivers 5 , 6 , which are fed to both a subtractor 14 and an adder 15 . In the subtractor 14 , the difference signal U _{d is formed} from the received signals U _e1 , U _e2 , while in the adder 15 the sum signal U _{s is formed} from the received signals U _e1 , U _e2 .

The sum signals U _s and the difference signal U _d are each fed to a sample and hold element 16 , 17 . The output signals at the sample and hold elements 16 , 17 are each output as analog output signals via a separate output 18 , 19 of the optoelectronic device 1 . The output signals output at these outputs 18 , 19 are output to an external unit, such as a computer unit, for checking or for correction purposes.

In addition, the output signals at the sample and hold elements 16 , 17 are read into an evaluation unit 20 , which is formed, for example, by a microcontroller, via an analog-digital converter (not shown). The instantaneous angular position and / or speed of the object 13 is calculated in the evaluation unit 20 from the sum signals U _s and difference signals U _d . The values determined in this way are displayed on a digital display 21 connected to the evaluation unit 20 .

In addition, input keys 22 and a parameter input 23 are connected to inputs of the evaluation unit 20 , via which parameter values are input into the evaluation unit 20 . The parameter values are stored in a parameter memory 24 . These parameter values can be formed from start values or from threshold values. Using the threshold values, for example, the determined angular positions or speeds, which form analog signals, can be digitized. The digital switching states generated in this way are output via a switching output 25 connected to the evaluation unit 20 .

FIG. 2 shows an example of the structure of the optical components of the optoelectronic device 1 according to FIG. 1.

The transmitter 2 is arranged in a central bore of a lens which forms the receiving optics 26 for the incoming light pulses 4 . The receivers 5 , 6 with the upstream polarization filters 7 , 8 are arranged behind a beam splitter 27 . The optical axes of the receivers 5 , 6 ver run at an angle of 90 ° to each other. This arrangement achieves coaxial beam guidance of the transmitted light pulses 3 and the received light pulses 4 . In the embodiment shown in FIG. 2, the optical axes of the transmit 3 and receive light pulses 4 lie in the axis of rotation D, about which the object 13 rotates with the reflector 9 arranged thereon. Since the reflector 9 is arranged so that the normal vector of its surface lies in this axis of rotation D.

According to the invention, the polarization directions of the polarization filters 7 , 8 arranged upstream of the receivers 5 , 6 are rotated relative to one another. The difference in the angular positions β and γ of the two polarization filters 7 , 8 is preferably in the range 20 ° ≦ | β - γ | ≦ 160 °.

Fig. 3 shows an example of the waveforms of the received signals U _e1 , U _e2 as well as the sum and difference signals U _s , U _d depending on the angular position α of the object 13 and thus the reflective film 10 with the upstream polarization filter 11th

Since the reflective film 10 is arranged upstream of the polarization filter 11 , polarized received light pulses 4 are reflected on the reflector 9 , the polarization direction of which corresponds to the current direction of polarization of the reflective film 10 before the ordered polarization filter 11 .

Polarizers 7 , 8 with angular positions of β = -45 ° and γ = 45 ° are arranged in front of the receivers 5 , 6 , so that their polarization directions are rotated by 90 °. This means that only the correspondingly polarized portions of the received light pulses 4 reach the respective receivers 5 , 6 .

Accordingly, at the outputs of the receivers 5 , 6 , sinusoidal receive signals U _e1 , U _e2 , which are dependent on the angular position α, are obtained, which are 180 ° out of phase with one another. The difference signal U _d formed from the received signals U _e1 , U _e2 also varies sinusoidally, while the sum signal U _{s is} constant.

As can be seen from FIG. 3, the difference signal U _d provides a measure of the angular position α of the object 13 . The difference signal U _d varies in the range between -30 ° ≦ α ≦ 30 ° approximately linearly with the angular position α, so that in this area the difference signal U _d directly indicates the current angular position α of the object 13 .

In this case, the sum signal U _s is expediently regulated to a predetermined setpoint. Level-independent difference signals U _{d are} thus obtained and, in particular, distance-related level changes in the received signals are compensated for.

To determine the speed of the object 13 , an oscillator (not shown) is preferably used in the evaluation unit 20 , which generates a clock cycle with a period T. The speed of the object 13 is determined by determining the number of zero crossings of the difference signal and then dividing by the period T.

FIG. 4 shows a diagram corresponding essentially to the diagram according to FIG. 3 with the signal profiles of U _e1 , U _e2 , U _s , U _d as a function of the angular position α of the object 13 .

In contrast to FIG. 3, the signal curves of U _e1 , U _e2 , U _s , U _d are shown in the diagram according to FIG. 4 in the event that the difference value β - γ is now considerably smaller. In the case shown, the angle difference β - γ lies approximately in the range 20 ° ≦ | β - γ | ≦ 60 °.

In this case, the sum signal US is no longer constant. Since the phase difference between the signal profiles of U _e1 and U _{e2 is} now considerably smaller than 180 °, a difference signal U _{d is} obtained when the difference _{is formed} , which varies linearly with α over a large angular range. Thus, the angular position α of the object 13 can be derived directly from the difference signal U _d in a correspondingly large angular range.

Instead of evaluating the difference signal U _d also the quotient of the difference and sum signal U _d / U _s zoom can be drawn to determine the angular position. The advantage here is that this quotient forms a level-independent signal.

Fig. 5 shows a first application example of the optoe lektronischen device 1 of the invention. The reflector 9 is located on the front side of the drive shaft 28 of a drive 29 and lies in the axis of rotation D of the drive shaft 28 . The optoelectronic device 1 is held in such a way that the transmitted light pulses 3 hit the reflector 9 .

As can be seen from FIG. 5, it is not necessary for the optoelectronic device 1 to be oriented such that the optical axes of the sensor 3 and received light pulses 4 lie exactly in the axis of rotation D of the drive shaft 28 . Detection of the reflector 9 by the optoelectronic device 1 is also ensured if the optical axis of the transmitted 3 and received light pulses 4 is inclined by an angle δ with respect to the axis of rotation D, the angle δ being a maximum of approximately 20 °.

Since the drive shaft 28 typically rotates at a high speed, only the speed, but not the instantaneous angular position of the drive shaft 28, is determined by means of the optoelectronic device 1 . At low speeds, a determination of the angular position can also be useful.

FIG. 6a shows an alternative arrangement of the reflector 9 to a drive 29 for determining the rotational speed and position. In this case, the reflector 9 is seated on the upper side of the drive 29 next to the drive shaft 28 projecting from the center of the upper side of the drive 29 . The optoelectronic device 1 is located above the position of the reflector 9 shown in FIG. 6a. Since the reflector 9 is arranged outside the axis of rotation D of the drive shaft 28 , it is not continuously detected by the optoelectronic device 1 , but instead is guided past the optoelectronic device 1 once per revolution of the drive shaft 28 . Correspondingly, the signal curve of the differential signal U _d shown in FIG. 6b results as a function of the angular position α of the drive shaft 28 . As long as the reflector 9 is not in the beam path of the optoelectronic device 1 , the difference signal U _d assumes the value zero. The reflector 9 is detected by the device 1 only for a limited angular range, so that the difference signal then first rises to values greater than zero and then falls to values less than zero. To determine the rotational speed, the zero crossings of the difference signal U _{d are} counted and divided by the period T of the clock predetermined by the oscillator of the evaluation unit 20 .

FIG. 7 shows an arrangement of the optoelectronic device 1 above a conveyor belt 30 on which transport goods 31 are conveyed. A reflector 9 is attached to the top of each of the goods to be transported 31 . By detecting the reflectors 9 by means of the optoelectronic device 1 , the orientation of a transport item on the conveyor belt 30 is determined in each case.

Fig. 8 shows an arrangement of an optoelectronic device 1 to a bending spring part 32. By exerting a force F on the bending spring part 32 mounted on one side on a holder 33 , the latter is bent in a defined manner. To determine the tilt angle, a reflector 9 is attached to the free end of the bending-spring part 32 , which device 1 is scanned with the optoelectronic device.

FIG. 9 shows a drive shaft 28 'with a rotor 34 and a drive 29 ' which are mounted on the drive shaft 28 'in a rotationally symmetrical manner with respect to the axis of rotation of the drive shaft 28 '. To determine the torsion angle of the drive shaft 28 'sit zen on the front and rear end of each a reflector 9 . Each reflector 9 is scanned by an optoelectronic device 1 to determine the angular position. The differences in the angular positions of the reflectors 9 determined in this way give a direct measure of the torsion of the drive shaft 28 '.

Fig. 10 shows an arrangement for determining the slip on a belt drive. The belt drive has two cylindrical rotors 35 , 36 , on the lateral surfaces of which a belt 37 rotates. On the front end faces of the rotors 35 , 36 , a reflector 9 is arranged lying in the axis of rotation. Each reflector 9 is scanned with an optoelectronic device 1 .

As a result, the speeds and angular positions of the rotors 35 , 36 are averaged, from which the slip of the belt drive can be determined.

Reference list

(

1

) Optoelectronic device
(

2nd

) Channel
(

3rd

) Transmitted light pulses
(

4th

) Received light pulses
(

5

) Receiver
(

6

) Receiver
(

7

) Polarization filter
(

8th

) Polarization filter
(

9

) Reflector
(

10th

) Reflective tape
(

11

) Polarization filter
(

12th

) Holder
(

13

) Object
(

14

) Subtractor
(

15

) Adder
(

16

) Sample & Hold link
(

17th

) Sample & Hold link
(

18th

) Exit
(

19th

) Exit
(

20th

) Evaluation unit
(

21

) Digital display
(

22

) Enter keys
(

23

) Parameter input
(

24th

) Parameter memory
(

25th

) Switching output
(

26

) Receiving optics
(

27

) Beam splitter
(

28

) Drive shaft
(

28

') Drive shaft
(

29

) Drive
(

29

') Drive
(

30th

) Conveyor belt
(

31

) Transport goods
(

32

) Bending spring part
(

33

) Bracket
(

34

) Rotor
(

35

) cylindrical rotor
(

36

) cylindrical rotor
(

37

) Straps

Claims (18)

1. Optoelectronic device with at least one transmitter light-emitting transmitter and one receiver-receiving light pulse receiver, characterized in that a reflector ( 9 ) with an upstream polarization filter ( 11 ) is attached to determine the angle and / or speed of an object ( 13 ) that two transmitters ( 2 ) are provided, each with a downstream polarization filter, which alternately emit transmission light pulses ( 3 ), or that two receivers ( 5 , 6 ) with upstream polarization filters ( 7 , 8 ) are provided, so that the one Transmitter ( 2 ) emitted and reflected on the reflector ( 9 ), transmitted light pulses ( 3 ) as received light pulses ( 4 ) on the receivers ( 5 , 6 ), the transmitters arranged downstream or upstream of the receivers having different polarization directions and that from the transmit light pulses of the two transmitters, which are as receive links chtimpulse are performed on the receiver, or from the received light pulses ( 4 ) that strike the two receivers, a difference signal U _d or quotient signal is formed as a measure of the angular position and / or speed of the object ( 13 ). 2. Optoelectronic device according to claim 1, characterized in that an additional sum signal U _{s is} formed. 3. Optoelectronic device according to claim 2, characterized in that the sum signal U _s and the difference signal U _d each via a sample & hold element ( 16 , 17 ) in an evaluation unit ( 20 ) is sen, in which the sum - And difference signal U _s and U _d the angular position and / or speed of the object ( 13 ) is determined. 4. Optoelectronic device according to one of claims 1 or 3, characterized in that the angular positions β and γ of the polarizers ( 7 , 8 ) arranged downstream of the transmitters ( 2 ) or upstream of the receivers ( 5 , 6 ) by a difference angle β - γ in the range 20 ° ≦ β - γ ≦ 160 ° are rotated against each other. 5. Optoelectronic device according to one of claims 1-4, characterized in that for determining the angular position of the object ( 13 ) the difference signal U _d in the area in which it has an approximately linear dependence on the angular position is used. 6. Optoelectronic device according to claim 5, characterized in that at an angle difference | β - γ | = 90 ° the constant sum signal U _{s is} regulated to a predetermined setpoint. 7. Optoelectronic device according to one of claims 2-4, characterized in that the quotient U _d / U _{s of} the difference and sum signal U _d and U _{s is} formed to determine the angular position of the object ( 13 ). 8. Optoelectronic device according to one of claims 3-7, characterized in that for determining the speed in the evaluation unit ( 20 ) a periodic cycle with a period T is predetermined, and that for determining the speed, the number of zero crossings of the differential signal U _{d is} counted and divided by the period T. 9. Optoelectronic device according to one of claims 1-8, characterized in that the reflector ( 9 ) with the upstream polarization filter ( 11 ) is glued to the object ( 13 ) or fastened by means of a magnet. 10. Optoelectronic device according to one of claims 1-9, characterized in that the object ( 13 ) rotates about an axis of rotation, and that the reflector ( 9 ) with the polarization filter ( 11 ) on the object ( 13 ) is so fastened that the normal vector of its surface runs parallel to the axis of rotation. 11. Optoelectronic device according to claim 10, characterized in that the normal vector of the surface of the reflector ( 9 ) lies in the axis of rotation D of the object ( 13 ). 12. Optoelectronic device according to claim 11, characterized in that the transmitter ( 2 ) and receiver ( 5 , 6 ) have a coaxial optical axis which extends at least approximately in the axis of rotation D of the object ( 13 ). 13. The optoelectronic device according to claim 12, characterized in that its optical axis is inclined by an angle δ in the range 0 ° ≦ δ ≦ 20 ° with respect to the axis of rotation D of the object ( 13 ). 14. Optoelectronic device according to one of claims 1-13, characterized in that it is used to determine the speed or angular position of a drive shaft ( 28 ). 15. Optoelectronic device according to one of claims 1-14, characterized in that it is used for determining the position of transported goods ( 31 ) conveyed on a conveyor belt ( 30 ). 16. Optoelectronic device according to one of claims 1-15, characterized in that it is used for determining the tilt angle of a bending spring part ( 32 ). 17. Optoelectronic device according to one of claims 1-16, characterized in that it is used to determine the torsion of a drive shaft ( 28 '). 18. Optoelectronic device according to one of claims 1-17, there characterized in that this to determine the slip at egg belt drive is used.