DE10130227A1 - Materials handling optical sensor filters out background items - Google Patents

Abstract

An optical sensor detects the presence of objects within a given area. The sensor has a sensor module with a sender, a near-distance receiver, a far-distance receiver, and an electronic circuit which evaluates the signals received. The evaluation circuit compares the difference between the near-range and far-range signals, generating a third difference signal. The evaluation circuit further determines whether an object is in the monitoring area and whether it is moving or static.

Description

The invention relates to an optical sensor.

Such optical sensors are in particular as light barriers, reflection light barriers or light sensors.

These optical sensors have a sensor that emits light rays and a receiver receiving receiving light beams. The of monitoring area detected by the sensors for the detection of objects predetermined by the course of the optical axis of the transmitted light beams.

In the case of light barriers and retro-reflective sensors, the transmission light rays are with free beam path as receiving light beams unimpeded on the emp led catcher. An object is in the beam path of such a Sen sors, the beam path of the transmitted light beams is at least partially below broken, so that a significantly reduced amount of received light at the receiver ger is registered. In an evaluation unit downstream of the receiver when registering the reduced amount of received light, an object Detection signal generated and output via a switching output.

With a light barrier, the transmitter and the receiver are on both sides of the Monitoring area arranged opposite. With a reflection The transmitter and the receiver are on one side of the light barrier surveillance area, while the other side of the surveillance area of a reflector is limited, on which the transmitted light beams are free Striking the beam path.  

The monitoring area is so for a large number of applications formed that this is not on both sides of the optical components of a Light barrier or a reflection light barrier can be limited. at For example, in complex systems, such as machine lines or conveyor lines, the installation space may be limited such that an attachment light barrier systems is not possible.

In these cases, optical sensors designed as light sensors are preferred Sensors used. These have a transmitter and a receiver, the are arranged side by side in a housing.

If the beam path is clear, no received light rays hit the receiver ger. Only when there is an object in the surveillance area, who which the transmitted light rays from the object as received light rays onto the Reflected back receiver, so that in the downstream of the receiver Evaluation unit an object detection signal is generated. The Ge Object detection signal is in turn output via a switching output give.

The problem with such light sensors is that the monitoring area cannot be delimited exactly. The range of the sensor within which objects are detectable, in particular by the reflectivity of the surfaces dependent on these objects.

Another disadvantage is that based on the output via the switching output Item detection signal received only information about it whether an object exists or not. More information about the Object status are not preserved.

The invention is based, an optical sensor with poss extremely high detection sensitivity and expanded functionality put.  

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 optical sensor according to the invention is used to detect objects in a monitoring area and has at least one sensor module from at least one transmitter, a short-range receiver arrangement for Detection of objects in the surveillance area, a long-range Receiver arrangement for the detection of background objects and an off value unit for evaluating the short-range signals at the output of the near-end Reichs-Receiver arrangement Furthermore, the opti according to the invention Long-range signals at the output of the long-range Receiver arrangement, wherein in the evaluation unit by difference a difference sig from the short-range signal and the long-range signal nal is formed. The difference signal is used in the evaluation unit Item detection signal generated, which indicates whether an object in the Surveillance area is present and a motion detection signal, which indicates whether an object is within the surveillance area moved.

There is a significant advantage of the optical sensor according to the invention in that by forming the difference between the Receiver arrangement obtained short-range signals and those with the Fernbe long-range signals obtained by the Reichs receiver arrangement are safe Object detection in a limited surveillance area is made possible, without background signals leading to incorrect switching.

Another significant advantage of the sensor according to the invention is in that it can not only be used to determine whether an object is in excess area, but also whether there is an object within the area guard area moved.  

Thus, in particular, with the optical sensor according to the invention dynamic processes detectable. In particular, the optical sensor is Kon trolls of funding processes can be used.

In a particularly advantageous embodiment of the invention, the opti cal sensor on a plurality of preferably identical sensor modules. By means of these sensor modules, a flat monitoring area will be left behind los monitored, the length of the surveillance area essentially is determined by the number of sensor modules.

The optical sensor according to the invention is particularly advantageous for monitoring Chung bottles used, which transported on a conveyor line become. The conveyor line comprises several conveyors located next to each other belts on which bottles are transported standing one after the other. With the optical sensor, jams on the conveyor line in particular can be avoided are recognized, the traffic jam detection both by means of a static ob object detection as well as in a dynamic measurement.

Static object detection is selective using the optical sensor a section of a conveyor belt is monitored, on which only bottles are arranged when there is a jam during bottle conveying. With that lies with an object detection of the sensor and a related delivery an object detection signal before a jam while not of an object detection signal there is no jam.

It is essential that background signals elimi with the optical sensor can be renated, so that by bottles, which are attached to conveyor belts which are behind the monitored conveyor belt are not wrong conduct detections.  

With dynamic measurement, the optical sensor can directly different states of motion of the bottles are recorded. At ord In accordance with the operation, the bottles pass the optical sensor guided. By detecting the bottle movement, the movement Detection signal triggered. In the event of a jam, the bottles are in the monitoring area detected by the optical sensor, so that the movement detection signal is absent.

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

Fig. 1: conveyor line with an arrangement of conveyor belts for the trans port of bottles monitored by optical sensors in error-free transport operation.

Fig. 2: conveyor line according to Fig. 1 with a bottle jam present.

Fig. 3: Schematic representation of the optical components of a Sensormo duls for the optical sensor shown in FIG. 1 and 2.

FIG. 4 shows a multiple arrangement of sensor modules according to Fig. 3.

Fig. 5: Block diagram of the optical sensor according to Fig. 1 and 2.

In Figs. 1 and 2, a typical application for the erfindungsge MAESSEN optical sensor 1 is shown, with its possible use is not limited to this application. The optical sensor 1 is generally suitable for static and dynamic object detection, this taking place within delimitable monitoring areas.

Figs. 1 and 2 show a section of a conveying path 2 for the transport of bottles 3. The conveyor section 2 runs along a curve and has a plurality of conveyor belts 4 a-e lying next to one another. The conveyor belts of the 4 a-e adjoin each other without delimitation and preferably run at different speeds. The conveyor belt 4 a on the inner track runs at the highest speed. The speeds of the adjacent conveyor belts 4 b-e decrease continuously towards the outer track, so that the conveyor belt 4 e has the lowest speed on the outer track.

The bottles 3 are conveyed one behind the other at a small distance from one another on the individual conveyor belts 4 a-e. In this case, all conveyor belts 4 a-e are tightly filled with bottles 3 on the straight section of the conveyor section 2 before the curve.

Fig. 1 shows the case that the bottles 3 v without jamming at different speeds to run <0 by the curve of the conveying path 2. Since the speed on the conveyor belt 4 a of the inner track is greatest and the speeds of the conveyor belts 4 b-e adjoining the outer track decrease continuously, in the curve the bottles 3 are moved from the conveyor belts 4 a-e running on the inner tracks to the outer conveyor belts of FIG. 4 ae pushed away. Thus, at the exit of the curve, the conveyor belts 4 a-e are filled with bottles 3 the more they are on the outer track.

Fig. 2 shows the case of a jam during bottle transport. The speeds of the conveyor belts 4 a-e are no longer sufficient to transport the bottles 3 through the curves, so that the conveyor belts 4 a-e of the inner tracks are completely occupied with bottles 3 at the exit from the curve of the conveyor section 2 .

To detect such congestion, the optical sensor 1 according to the invention is used, which can in principle be attached in two different installation positions A, B, which are identified by A and B in FIGS. 1 and 2.

In the installation position designated A, the movement of the bottles 3 transported on the conveyor belt 4 a-e on the inner track is detected with the optical sensor 1 . The optical sensor 1 detects the various movement states of the bottles 3 , whereby a jam of the bottles 3 is detected.

With the optical sensor 1 arranged in the installation position B there is against a traffic jam detection with a static signal evaluation.

This takes advantage of the fact that in the area of the installation positions A, B, the conveyor belts 4 a, b on the inner track of the conveyor section 2 are not filled with bottles 3 in error-free operation, while in the event of a jam also bottles 4 a, b on the inner conveyor belts 3 are arranged.

The surveillance region detected with the optical sensor 1 according to the invention is dimensioned such that only the occupancy of the conveyor belts of FIGS. 4 a, b is checked on the inner tracks. Preferably only the internal conveyor belt 4 a is checked. A static congestion control within this monitoring area can reliably detect a traffic jam.

Fig. 3 shows the optical components of a sensor module for the optical sensor 1 rule. The sensor module has a transmitter S ₁ which emits light rays, the transmitter S _{1 being formed} by a light-emitting diode or the like.

Furthermore, the sensor module has a short-range receiver arrangement and a long-range receiver arrangement. The short-range receiver arrangement has two receivers E _N1 , the optical axes A _{N1 of which} converge at an acute angle, so that they intersect at an intersection which lies on the optical axis A _{S1 of} the transmitter S ₁ .

The position of the intersection essentially defines the limit of the overshoot area within which objects can be detected by means of the sensor module are.

The long-range receiver arrangement also has two receivers E _F1 , the optical axes A _{F1 of which} run parallel to the optical axis A _{S1 of} the transmitter S ₁ . These receivers E _F1 serve to receive background signals, which originate from objects which are arranged at great distances from the sensor 1 , lying outside the monitoring area.

As can be seen from FIG. 3, the transmitter S ₁ and the receivers E _N1 , E _{F1 of} the sensor module are arranged lying along a straight line. The Emp catchers E _N1 , E _{F1 are arranged} symmetrically with respect to the transmitter S ₁ .

Fig. 4 shows an array of sensor modules for an optical sensor 1. Four identical sensor modules are provided, the structure of which corresponds to the arrangement according to FIG. 3.

Accordingly, four transmitters S _i (i = 1,... 4) with optical axes A _Si (i = 1,... 4) are provided for the sensor modules.

Each of the sensor modules has a short-range receiver arrangement, each with two receivers E _Ni (i = 1,... 4), whose optical axes A _i (i = 1,... 4) converge at an acute angle.

Furthermore, each sensor module has a long-range receiver arrangement, each with two receivers E _Fi (i = 1,... 4), whose optical axes A _Fi (i = 1,... 4) parallel to the optical axes A _{Si of} the transmitters S _i run.

As can be seen from FIG. 4, all of the optical components of the sensor modules are arranged along a straight line, analogous to the embodiment according to FIG. 3, the optical components of adjacent sensor modules being partially nested inside one another. This ensures a seamless coverage of a large monitoring area.

FIG. 5 shows a basic circuit diagram of an evaluation unit for an optical sensor 1 , which has an object arrangement according to FIG. 4.

The transmitters S _i (i = 1,... 4) are operated in pulse mode and each emit transmitted light pulses with a predetermined pulse-pause ratio. The transmitters S _i are each connected via a multiplex unit 5 to an input of a flip-flop 6 a-d. The flip-flops 6 a-d are each designed as D flip-flops. The transmitters S _i are activated cyclically one after the other via the multiplex unit 5 .

The receivers E _{Ni of} the short-range receiver arrangement and the receivers E _{Fi of} the long-range receiver arrangement are each connected in parallel for each sensor module. These pairs of receivers connected in parallel are connected antiparallel via a resistor 7 a-d.

With this circuit arrangement, the sum signals of the receiver pairs of the short-range receiver arrangement and the long-range receiver arrangement are first formed for each sensor module, which signals form the short-range signals and the long-range signals of the respective sensor module. From the short-range and long-range signal, a differential signal is formed by the anti-parallel circuit, which is fed via a threshold unit 8 a-d to the flip-flop 6 a-d, to which the transmitter S _{i of} the corresponding sensor module is also connected.

The outputs of the flip-flops 6 a-d are guided to an adding unit, which is formed by an arrangement of resistors 9 a-d, 10-13 and an operational amplifier 14 . A resistor 12 is used to specify a reference voltage for the operational amplifier 14 .

A response delay unit 15 and subsequently a drop delay unit 16 are connected to the output of the adding unit. The output from the dropout delay unit 16 is routed via a first driver circuit 17 to a first switching output 18 .

The response delay unit 15 preferably consists of an RC element or the like. The drop delay unit 16 consists, for example, of a parallel connection of a diode with a resistor.

The outputs of the flip-flops 6 a-d are also led to a motion detection circuit 20 via an arrangement of diodes 19 a-d. Their output and the output of the drop-out delay unit 16 are guided via an AND gate 21 to a second driver circuit 22 and a second switching output 23 .

The motion detection circuit 20 consists of a further response delay unit 24 , which is followed by a first trigger unit 25 . This is dynamically coupled via a capacitor 26 to a further waste delay unit 27 , the output of which is routed to a further trigger unit 28 .

By forming the difference between the short-range and long-range signals and the subsequent threshold value evaluation of the differential signals is guaranteed, that only signals from objects located in the surveillance area, not however, be evaluated by objects in the background.

The signal pulses generated at the outputs of the threshold value units 8 a-d are fed on the one hand to the adder unit for generating an object detection signal. A static signal evaluation takes place, by means of which it is detected whether an object is in the monitoring area or not. Such a static signal evaluation takes place in particular in the case of the optical sensor 1 arranged in the installation position B according to FIGS. 1 and 2.

A prerequisite for object detection is that a predetermined number of signal pulses is registered in the adding unit, this number being adjustable by a suitable specification of the reference voltage on the operational amplifier 14 .

In the downstream response delay unit 15 , short-term signal fluctuations are filtered out so that they do not lead to false detections.

In the detection of successively conveyed bottles 3 on the conveyor line 2, there would be a continuous change of the binary output signal at the first switching output 18 , since when a bottle 3 was detected an object detection signal (first switching state of the switching output 18 ) would be generated and upon detection a gap between two bottles 3, the object detection signal would remain (second switching state of the switching output 18 ). In order to avoid such a brief change in the switching state of the first switching output 18 , the drop-out delay unit 16 is provided, by means of which the object detection signal is retained even when a gap between two bottles 3 is detected in the meantime. The object detection signal therefore only remains off if no bottle 3 has been detected over a longer period of time.

The signal pulses generated at the outputs of the threshold value units 8 a-d are further fed to the motion detection circuit 20 , which is used to generate a motion detection signal.

In the motion detection circuit 20 there is a dynamic evaluation of the signal pulses. Such a dynamic signal evaluation takes place in particular in the case of the optical sensor 1 according to FIGS. 1 and 2 arranged in the installation position A. The motion detection circuit 20 detects whether objects are moving within the monitoring area or not. This takes advantage of the fact that a continuous change in the temporal sequence of the signal pulses is obtained when an object moves. The edges of the changing signal pulses are detected in the movement detection circuit 20 and converted into a continuous movement detection signal, which is output via the second switching output 23 . If there is no object movement within the monitoring area, the movement detection signal remains off.

LIST OF REFERENCE NUMBERS

1

Optical sensor

2

conveyor line

3

bottle

4

ae conveyor belts

5

multiplex unit

6

ad flip-flop

7

ad resistors

8th

ad threshold unit

9

ad resistors

10

resistance

11

resistance

12

resistance

13

resistance

14

operational amplifiers

15

Ansprechverzögerungseinheit

16

Waste delay unit

17

first driver circuit

18

first switching output

19

ad diodes

20

Motion detection circuit

21

AND gate

22

second driver circuit

23

second switching output

24

Ansprechverzögerungseinheit

25

trigger unit

26

capacitor

27

Waste delay unit

28

trigger unit
A installation position
B installation position
A _Fi

optical axis of the receiver E _Fi

A _Ni

optical axes of the receivers E _Ni

A _S1

optical axis of the transmitter S _i

E _Fi

receiver
E _Ni

receiver
S _i

Channel

Claims (17)

1. Optical sensor for detecting objects in a surveillance area rich with at least one sensor module consisting of at least one egg nem transmitter, a short-range receiver arrangement for the detection of Objects in the surveillance area, a long-range receiver Arrangement for the detection of background objects and an evaluation Unit for evaluating the short-range signals at the output of the near-end Reich receiver arrangement and the long-range signals at the output the long-range receiver arrangement, wherein in the evaluation unit by forming the difference between the short-range signal and the Fernbe Reichssignal a difference signal is formed, and being in the Auswer a unit detection signal from the difference signal, which indicates whether there is an object in the surveillance area, and a motion detection signal indicating whether an Ob object within the monitored area is generated. 2. Optical sensor according to claim 1, characterized in that the long-range receiver arrangement has two receivers (E _Fi ) lying on both sides of the transmitter (S _i ), the optical axes (A _Fi ) of which are parallel to the optical axis (A _Si ) of the transmitter (S _i ) run, and that the Nahbe range receiver arrangement has two receivers (E _Ni ) lying on both sides of the transmitter (S _i ), the optical axes (A _Ni ) of which converge at an acute angle, the intersection of the optical axes (A _Ni ) on the optical axis (A _Si ) of the transmitter (S _i ). 3. Optical sensor according to claim 2, characterized in that the receiver (E _Ni , E _Fi ) of the short-range receiver arrangement and the long-range receiver arrangement lying along a straight line are arranged symmetrically to the transmitter (S _i ). 4. Optical sensor according to one of claims 1-3, characterized net that this has several identically designed sensor modules. 5. Optical sensor according to claim 4, characterized in that the transmitter (S _i ) and receiver (E _Ni , E _Fi ) of the sensor modules are arranged along a straight line. 6. Optical sensor according to one of claims 4 or 5, characterized in that the transmitters (S _i ) and receivers (E _Ni , E _Fi ) of adjacent sensor modules are arranged nested one inside the other. 7. Optical sensor according to one of claims 4-6, characterized in that the transmitters (S _i ) of the sensor modules each emit transmitted light pulses with a predetermined pulse-pause ratio. 8. Optical sensor according to claim 7, characterized in that the evaluation unit has a multiplex unit ( 5 ), by means of which the dif ferential signals of the individual sensor modules are evaluated cyclically one after the other. 9. Optical sensor according to one of claims 7 or 8, characterized in that the evaluation unit has threshold value units ( 8 a-d) by means of which the differential signals of a sensor module are converted into a binary sequence of signal pulses. 10. Optical sensor according to one of claims 1-9, characterized in that the objects are formed by bottles ( 3 ) transported on a conveyor line ( 2 ), the conveyor line ( 2 ) having a plurality transverse to the conveying direction of the bottles ( 3 ) has adjacent conveyor belts ( 4 a-e) on which bottles ( 3 ) are arranged one behind the other at a distance. 11. Optical sensor according to claim 10, characterized in that it is mounted on the side of the conveyor line ( 2 ), so that the monitoring area extends only to the nearest conveyor belt ( 4 a). 12. Optical sensor according to claim 11, characterized in that it is used to detect whether the nearest conveyor belt ( 4 a) is filled with bottles ( 3 ). 13. Optical sensor according to claim 11, characterized in that it is used to detect whether the bottles ( 3 ) are conveyed on the nearest conveyor belt ( 4 a). 14. Optical sensor according to one of claims 10-13, characterized in that the evaluation unit for generating the object detection signal has an adding unit, a response delay unit ( 15 ) and a drop-out delay unit ( 16 ), wherein an object detection signal is only generated , if a predetermined number of signal pulses is registered in the adder unit, with short-term signal interference being eliminated in the response delay unit ( 15 ), and with a brief drop in the object detection signal in the drop-out delay unit ( 16 ) upon detection of gaps between two the nearest conveyor belt ( 4 a) moving bottles ( 3 ) is avoided. 15. Optical sensor according to claim 14, characterized in that the object detection signal is output via a first switching output ( 18 ). 16. Optical sensor according to one of claims 10-15, characterized in that the evaluation unit for generating the motion detection signal has a motion detection circuit ( 20 ), in which a continuous motion detection signal is derived from a time-varying sequence of signal pulses, and wherein if there is no or no time-constant sequence of signal pulses, no motion detection signal is generated. 17. Optical sensor according to claim 16, characterized in that the outputs of the motion detection circuit ( 20 ) and the waste delay unit ( 16 ) via an AND gate ( 21 ) are fed to a second switching output ( 23 ) for outputting the motion detection signal.