Patent ID: 12248104

Identical or similar components are generally identified in the figures by the same reference numerals.

An optical sensor200according to the prior art will be explained by reference toFIG.1. The optical sensor200has, as basic components, a transmitter S, a receiver E, a measuring core15, a control and evaluation unit formed by a measurement controller16, and an interface94,95.

Via the interface94,95the sensor200can send or communicate data, for example via a bus system.

The sensor200is a sensor according to the time-of-flight principle and works essentially as follows: the transmitter S transmits light pulses12into the monitored region11and these light pulses are radiated back by an object10located in the monitored region11. These radiated-back light pulses13are detected by the receiver E. The time difference between a time of emission of a light pulse12and the timepoint at which the radiated-back light pulse13is detected by the receiver E is measured. The relationship:
d=time difference*speed of light/2
provides the distanced of the object10from the optical sensor200.

In order to obtain information on the components used for the measurement, transmitter S and receiver E, the optical sensor200inFIG.1has an internal test path with a test object. For testing, the transmitter S transmits test light pulses17in a test operation. These are radiated back by the test object18. The radiated-back test light pulses19are then detected by the receiver E and subsequently evaluated via the measuring core15by the measurement controller16. If the detected test light pulses19do not have the expected properties, certain signals, for example error signals, can be output, or certain actions, for example disconnection of the sensor, can be triggered.

Further components of the optical sensor200provided are: a module91for monitoring a front screen, an angle sensor92for a rotor (if the sensor200is a 2D scanner) and a power supply93.

Exemplary embodiments of optical sensors100and300according to the invention, wherein these can be in particular 2D scanners, will be described in association withFIGS.2to5. The optical sensors100and300are sensors according to the time-of-flight principle for detecting objects in a monitored region11. The optical sensor100has, as essential components, firstly a first transmitter S1, a first receiver E1, a second transmitter S2and a second receiver E2. The first transmitter S1is used initially to transmit first light pulses22into the monitored region11. The first receiver E1is used initially to detect light pulses23which are radiated back by an object to be detected10in the monitored region11. The second transmitter S2is used initially to transmit second light pulses32into the monitored region11. The second receiver E2is used initially to detect light pulses33which are radiated back by the object10.

To control the first transmitter S1and read the first receiver E1a first measuring core25and a first measurement controller26are provided. Through the first transmitter S1, the first receiver E1, the first measuring core25and the first measurement controller26, a first channel20is formed.

To control the second transmitter S2and read the second receiver E2, a second measuring core35and a second measurement controller36are provided. Through the second transmitter S2, the second receiver E2, the second measuring core35and the second measurement controller36, a second channel30is formed.

The first measurement controller26and the second measurement controller36can be formed in principle by one and the same microcontroller. The first measurement controller26and the second measurement controller36together form a control and evaluation unit26,36provided according to the invention, which is designed to control the first transmitter S1and to evaluate the first light pulses23detected by the first receiver E1, and to control the second transmitter S2and to evaluate the second light pulses33detected by the second receiver E2.

The control and evaluation unit26,36can receive and send data over an interface94,95in a manner known in itself, for example via a bus system.

In the exemplary embodiment shown inFIG.2the optical axes of the first transmitter S1, the first receiver E1, the second transmitter S2and the second receiver E2point in the same direction.

Also formed in the optical sensor100, but not shown inFIG.2, according to the invention between the first transmitter S1and the second receiver E2, for example and preferably internally, is a first optical reference path, and formed between the second transmitter S2and the first receiver E1, for example and preferably internally, is a second optical reference path.

These reference paths can be realised in the exemplary embodiment ofFIG.2for example through optical fibres between the first transmitter S1and the second receiver E2and between the second transmitter S2and the first receiver E1, as shown inFIG.3for a variant of an optical sensor300according to the invention. In the case of the optical sensor300shown schematically inFIG.3, it can also be a 2D scanner, but wherein, by way of departure from the exemplary embodiment shown inFIG.2, the optical axis of the first transmitter S1and the first receiver E1is orientated counter to that of the second transmitter S2and the second receiver E2. It is also schematically shown inFIG.3that between the first transmitter S1and the second receiver E2a reference path27is formed by an optical fibre and, furthermore, between the second transmitter S2and the first receiver E1a reference path37is also formed by an optical fibre.

The control and evaluation unit26,36is designed according to the invention to trigger the first transmitter S1to transmit first test light pulses42,46, which reach the second receiver E2on the first optical reference path27, and to activate the second receiver E2, in particular at the latest, after a first time offset, the first time offset corresponding to a time of flight of the first test light pulses42,46over the first optical reference path27, and/or to trigger the second transmitter S2to transmit second test light pulses63,67, which reach the first receiver E1on the second optical reference path37, and to activate the first receiver E1, in particular at the latest, after a second time offset, the second time offset corresponding to a time of flight of the second test light pulses63,67over the second optical reference path37.

In principle the second receiver E2can already be activated at the times of emission of the first test light pulses42,46and the first receiver E1can already be activated at the times of emission of the second test light pulses63,67. It is essential that the second receiver E2is activated at the timepoints at which the first test light pulses42,46hit said second receiver E2, and that the first receiver E1is activated at the timepoints at which the second test light pulses63,67hit said first receiver E1.

The first test light pulses42detected by the second receiver E2and/or the second test light pulses63detected by the first receiver E1are evaluated by the control and evaluation unit26,36. In dependence upon this evaluation, certain signals, for example error signals, can be output via error functions or degradations of the transmitters or receivers, or certain actions, for example a disconnection of the sensor, can be initiated.

Operating modes for the optical sensors100and300according to the invention will be explained by reference toFIGS.4and5. These show in each case flowcharts, wherein, with respect to a time axis82, the respective intensity progressions of the transmission powers of the first transmitter S1and the second transmitter S2and also the intensities received by the first receiver E1and the second receiver E2are shown on the vertical axis84.

Corresponding to the temporal course is one respective rotation of the 2D scanner.FIGS.4and5show the progression over a full rotation from 0 to 360 degrees of a rotor of the 2D scanner.

It is essential for the operating mode shown inFIG.4that the test phases are separated from the measuring phases. For example, the first transmitter S1transmits first transmission pulses41,44,45,48and49, which cause in each case, after being radiated back by an object to be detected10in the monitored region11, receiving pulses51,52,54,55,56,58and respectively59in the first receiver E1. The schematically shown broadening of the received pulses in comparison with the transmitted pulses is caused substantially by the properties of the object radiating back said received pulses.

Correspondingly the second transmitter S1transmits second transmission pulses61,62,64,65,66,68and69, which, after being radiated back by an object to be detected in the monitored region11, trigger receiving pulses71,73,74,75,77,78,79in the second receiver E2. The object which radiates back the second transmission pulses can be either the same object to be detected10that has already radiated back the first transmission pulses. This would be the case with a geometry as inFIG.2. It can, however, also be another object to be detected, namely when the optical axis of the first transmitter S1and the first receiver E1is different from the optical axis of the second transmitter S2and the second receiver E2. This is the situation in the exemplary embodiment shown inFIG.3, where the viewing direction of the first transmitter S1and the first receiver E1is counter to the viewing direction of the second transmitter S2and the second receiver E2.

Taking place separately from these measuring operations in the process, or course, shown inFIG.4are the test measurements. For example, the first transmitter S1transmits first test light pulses42,46, which reach the second receiver E2via the first reference path27and cause receiving pulses72and respectively76there. Correspondingly the second transmitter S2transmits second test light pulses63,67, which reach the first receiver E1via the second reference path37and cause receiving pulses53and respectively57there. In the time phases after the times of emission of the first test light pulses42,46, in which test light pulses42,46radiated back from the monitored region11by an object would hit the first receiver E1, the first receiver E1is deactivated by the control and evaluation unit26,36.

Correspondingly the second receiver E2is deactivated by the control and evaluation unit26,36in the time phases after the times of emission of the second test light pulses63,67, in which test light pulses63,67radiated back from the monitored region11hit said second receiver E2.

Since, in the process shown inFIG.4, the measuring and the testing take place completely separately from each other in time, the measurements and the test measurements cannot influence or distort each other.

The important difference of the process shown inFIG.5in comparison with that ofFIG.4is that some of the light pulses transmitted by the first transmitter S1, namely the light pulses42and45, and some of the light pulses transmitted by the second transmitter S2, namely the light pulses63and66, respectively serve both for test measurements and also for the actual distance measurements. For example, a portion of the light pulses42,45reaches the second receiver E2via the first reference path27and causes a receiving pulse72or76there. A further portion of the light pulses42and45is radiated into the monitored region11, radiated back by an object there and then reaches the first receiver E1, causing a receiving pulse52or respectively56there.

Correspondingly a portion of the light pulses63and66reaches the first receiver E1via the second reference path37and causes a receiving pulse54or respectively58there. A further portion of the light pulses63and66is radiated into the monitored region11, radiated back by an object there and then reaches the second receiver E2, causing a receiving pulse74or respectively78there.

The advantage of the process shown inFIG.5is that fewer light pulses are required overall, because at least some of the light pulses are used both for measuring and also for testing. The useful life of the light transmitters used and hence the service life of each of the sensors can therefore be increased.

FIG.6illustrates the concepts of the axis of rotation of a rotor in a 2D scanner and the azimuthal direction. Shown schematically is a coordinate system x, y, z, wherein the axis of rotation of the rotor is orientated collinearly relative to the z axis. For example, in one exemplary embodiment of an optical sensor according to the invention having two transmitters S1, S2and two receivers E1, E2, the optical axes of the first transmitter S1and the first receiver E1can be orientated in the first azimuthal direction φ1, and the optical axes of the second transmitter S2and the second receiver can be orientated in the second azimuthal direction φ2. This would be the case for example in the variant shown inFIG.3. In an embodiment having a total of four transmitters and four receivers, the two further pairs of transmitter and receiver could be orientated in the direction of the azimuthal direction φ3and φ4. The pairs of transmitter and receiver are then positioned in each case at an angle of 90 degrees relative to each other.

With the present invention a novel optical sensor for detecting objects in a monitored region is provided, wherein the testing and measuring are realised particularly effectively. The optical sensor can be formed as a 2D scanner with an angle detection range of 360 degrees. The optical sensor according to the invention can be used in particular as a security scanner for the PL-d (performance level d). Particularly advantageous applications are possible for navigation, for example in floor conveyors.

LIST OF REFERENCE NUMERALS

10Object to be detected11Monitored region12Transmitted light13Light radiated back by the object1015Measuring core16Measurement controller17Test light of a test light path18Test object19Test light radiated back by the test object1920First channel22Transmitted light of the transmitter S123Light radiated back by the object10and detected by the receiver E125Measuring core of the first channel26Measurement controller of the first channel27Light conductor30Second channel32Transmitted light of the transmitter S233Light radiated back by the object10and detected by the receiver E235Measuring core of the second channel36Measurement controller of the second channel37Light conductor41-49Transmitted pulses of the transmitter S151-59Received pulses of the receiver E161-69Transmitted pulses of the transmitter S271-79Received pulses of the receiver E282Time axis84Intensity axis91Window monitoring92Angle sensor93Power supply94Interface95Bi-directional arrow100Optical sensor according to the invention200Optical sensor according to the prior artS TransmitterE ReceiverS1First transmitterE1First receiverS2Second transmitterE2Second receiverz Axis of rotationφ1Azimuthal directionφ2Azimuthal directionφ3Azimuthal directionφ4Azimuthal direction