Abstract:
An opto-electronic sensor for the optical detection of objects in a monitored zone. The sensor is coupled to a position measuring device for the production of at least one position detection signal and to an evaluation and control device for the calculation of an actual spatial position, alignment and/or angular position of the sensor using the position detection signal.

Description:
BACKGROUND OF THE INVENTION 
   The invention relates to an optoelectronic sensor for the optical detection of an object within a monitored zone. Such a sensor typically has a light transmitter for the transmission of a transmitted light beam as well as a light receiver for the generation of received light signals in dependence on an incidence of light. This incidence of light changes depending on the presence or on the position of an object in the monitored zone. An evaluation and control device can thus detect the presence or position of the object by an evaluation of the received light signals in order, for example, to produce a corresponding object detection signal. 
   Such an object can be an article, for example a piece of baggage or a shipped package on a conveyor belt, or a marking applied to an article, for example a barcode or a two-dimensional optical code. 
   For some applications of such sensors, an undesirably complex measurement of the position of the sensor with respect to the monitored zone or with respect to the objects to be detected located therein is necessary. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the invention to simplify and to improve a correct detection of objects and a correct association of object detection signals with the objects in question. 
   This object is satisfied for a sensor of the kind initially named in that the sensor is coupled to a position measuring device for the production of at least one position detection signal as well as to an evaluation and control device for the calculation of an actual spatial position, alignment and/or angular position of the sensor using the position detection signal. 
   The sensor in accordance with the invention is therefore equipped with a position measuring device which determines or receives one or more position detection signals and transmits them to an evaluation and control device. The latter calculates a spatial position of the sensor—for example in X, Y, Z coordinates—, an angular alignment of the sensor — for example within a predetermined plane, in particular the horizontal plane—, or an angular position of the sensor—for example relative to a predetermined plane, in particular the horizontal plane—, from the position detection signals. The position or location of the sensor can be determined in absolute coordinates—that is, with respect to universal reference points or in relative coordinates—that is, with respect to a local reference point. 
   The spatial position, alignment or angular position of the sensor thus calculated can be linked to an object detection signal which is determined in connection with the actual detection function of the sensor. In this manner, a correct spatial association can be established between this object detection signal and the corresponding object such that the object detection signal is not accidentally associated with an incorrect object. It can thus, for example, reliably be avoided that a shipped package transported on a transport belt is sorted out even though a barcode corresponding to this sorting out is not identified on this shipped package, but on a further shipped package. 
   The sensor in accordance with the invention can be connected to the position measuring device directly or indirectly, for example via the evaluation and control device. 
   A substantial advantage of the invention accordingly lies in the fact that, for the installation or the ongoing operation of a sensor, its spatial position, or angular position, can be determined in a simple manner and can be used as a basis for the sensor operation without the user having to make unwanted complex measuring or adjustment measures. Following applications are, for example, possible:
     (a) If a sensor in accordance with the invention is arranged with a barcode reader in a stationary manner in an omni-directional reading station, a read-in barcode can unambiguously be associated with one of a possible plurality of objects in the monitored zone on the basis of the determined spatial position, alignment and angular position of the sensor without a complex measurement of the barcode reader and of the monitored zone as well as a corresponding parameterization of the sensor being required.   (b) For a mobile arrangement of the sensor, a driver-less transport system can, for example, be provided which is equipped with a laser scanner which, for orientation, constantly scans its actual environment and thereby determines distance information. In such an application, the coupling of the laser scanner to the position measuring device and the corresponding calculation of the actual spatial position of the transport system can support its control to avoid incorrect guidings.   (c) Applications are also possible in which volumetric measurements are carried out at objects, for example by means of a laser scanner. For a correct calculation of a measured volume, the spatial position and the angular position of the laser scanner must be known. This information can be obtained in the sensor in accordance with the invention in a simple and reliable manner.   

   A particular advantage of the sensor in accordance with the invention lies in the fact that the sensor can quickly be reconfigured for different applications or positions—even if it is only provided for a stationary operational arrangement—since the new spatial position or angular position can be determined for the subsequent operation simply by pressing a button or automatically in order to be used as the basis for the further sensor control and signal evaluation. 
   A position signal receiver can, for example, be provided as the position measuring device of the sensor in accordance with the invention and is formed for the reception of reference signals of a satellite-aided position signal transmission system. Such a position signal receiver transmits the reference signals—for example after a signal amplification—to the evaluation and control device as position detection signals. The satellite-aided position signal transmission system can, for example, be the global positioning system (GPS) or the future Galileo satellite navigation system. Such systems continuously transmit radio signals via a network of satellites. A position or location value can be calculated—in a known manner—from the temporal association of these reference signals. 
   An advantage of the utilization of such a satellite-aided position signal transmission system lies in the fact that the position signal transmitters and the reference signals transmitted by these are available globally and at no cost. With the exception of the equipping of the sensor with the position signal receivers and with the evaluation and control device, no additional measures thus have to be taken to be able to determine the position of the sensor at any desired point of operation using the reference signals which can be received there. 
   In accordance with another advantageous embodiment, a position signal receiver is provided as the position measuring device and receives the reference signals which are transmitted by at least one local position signal transmitter, that is, a position signal transmitter installed in the environment of the opto-electronic sensor. These reference signals are converted into position detection signals, for example by filtering and amplification. In a similar manner as in the utilization of a satellite-aided position signal transmission system explained above, one or more local position signal transmitters can therefore be installed which transmit reference signals continuously or on call which can be received by the position signal receiver. The position signal transmitters thus serve as reference points with respect to which a relative position, alignment or angular position of the sensor can be calculated using the received reference signals. 
   An advantage of the use of such local position signal transmitters in connection with a position signal receiver coupled to the sensor lies in the fact that a very high precision can be achieved with respect to the spatial position, alignment or angular position to be determined, in particular in comparison with the evaluation of reference signal data of a satellite-aided position signal transmission system. 
   The reference signals transmitted by the position signal transmitters can be radio signals. The determination of the sensor position using the received reference signals can take place according to the principle of a radio beacon. It is preferred for the local position signal transmission system to encode and transmit the reference signals in the same form as in connection with satellite-aided position signal transmission systems. 
   It is in particular of advantage for the position signal receiver to be suitable for the reception of reference signals of both a satellite-aided position signal transmission system and of a local position signal transmitter. The possibility of a particularly precise position determination is thereby linked to an independence of local position signal transmitters and an independence of the local reception conditions of satellite-aided position signal transmitters. 
   With respect to the explained embodiment using local position signal transmitters, the invention also relates to an opto-electronic sensor system which has at least one local position transmitter of this kind as well as an opto-electronic sensor which is coupled to a position signal receiver of this kind for the reception of reference signals of the local position signal transmitter. 
   The position measuring device of the sensor in accordance with the invention can, in accordance with a further advantageous embodiment, have an alignment sensor, in particular a gyroscopic sensor, for example a gyroscopic compass, which produces at least one position detection signal which corresponds to an actual alignment of the sensor within a predetermined plane, for example, the horizontal plane. 
   In accordance with a further advantageous embodiment, an inclination sensor is provided as the position measuring device and produces a position detection signal by means of which the evaluation and control device can calculate an actual angular position of the sensor with respect to the vertical, to the horizontal or to any other reference line or reference plane. The inclination sensor can, for example as a so-called static acceleration sensor, have a semi-conductor component or it can be designed in accordance with the principle of an integrated spirit level. 
   It must be noted with respect to the explained embodiments of the position measuring device that these can be combined in any desired manner. For example, in addition to a position signal receiver for the reception of reference signals of a satellite-aided position signal transmission system, a gyroscopic sensor can be provided so that a plurality of position detection signals can be produced from which the actual spatial position and the actual alignment of the sensor in space can be determined. It is also possible, for example, to couple both a position signal receiver for the reception of reference signals of a local position signal transmitter and an inclination sensor to the opto-electronic sensor in order to be able to calculate an actual spatial position and an actual angular position of the sensor using the respective position detection signals. The gyroscopic sensor and the inclination sensor can also be jointly integrated into an optoelectronic sensor, with or without a position signal receiver. 
   The determination of an actual spatial position, alignment or angular position of the sensor, that is, the calculation of this information using a separate position signal or the last received position signal, can be triggered by means of the evaluation and control device, for example, on the basis of a trigger command entered by the user. For this purpose, the sensor can be equipped with a trigger switch which is optionally actuated by the user. 
   The determination of an actual spatial position or angular position can also be initiated by the evaluation and control device, for example, on the basis of taking the sensor into operation, and indeed on the basis of a first taking into operation by the user or on the basis of a repeat taking into operation, for example after a change of position or after a reconfiguring of the sensor. 
   Furthermore, the evaluation and control device can initiate a re-determination of the actual sensor position or sensor location at regular intervals which can be predetermined or which can be set by the user. 
   Alternatively or additionally, it is possible for the evaluation and control device to trigger a determination of an actual spatial position, alignment and/or angular position of the sensor when the sensor has detected a new object in the monitored zone, for example has read in a barcode. 
   The evaluation and control device is preferably formed such that it can associate an object detection signal of the sensor to a spatial position or an angular position determined on the basis of the received position signals, for example in order to transmit a control signal associated with the object in question. In other words, a spatial position of the sensor determined once or at an actual moment in time should be able to be associated with an object which has been detected by the sensor. This mutual association of object information and of spatial information thus corresponds to a spatial link between the sensor and the object in question in order to be able to separate out that piece of baggage or shipped package which bears an identified barcode on the basis of this link, for example by means of a controlled actuator, with a high reliability. 
   In order to be able to determine the actual spatial position, alignment or angular position of the sensor as immediately as possible when necessary, in particular with mobile sensor applications, it is preferred for the position measuring device to determine the available position detection signals continuously on the basis of a corresponding control by the evaluation and control device and to forward them to the control and evaluation device. 
   It is furthermore preferred for the position measuring device and the associated evaluation and control device to be permanently integrated into the sensor. In particular, the evaluation and control device provided for the calculation of the spatial position, alignment or angular position of the sensor can be part of that evaluation and control device which is provided for the control of the light transmitter and of the light receiver as well as for the evaluation of the received light signals of the opto-electronic sensor. The sensor in accordance with the invention can thus be equipped with the position measuring device as standard in order—as explained—to be able to determine the spatial position or angular position of the sensor with respect to universal spatial coordinates or with respect to predetermined reference positions for the first taking into operation or regularly in application use. 
   The sensor in accordance with the invention can also have an image detection camera, in particular a camera for the detection of two-dimensional codes, for example, instead of a barcode reader or laser scanner. 
   The invention will be explained in the following by way of example with reference to the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows an application of a sensor in accordance with the invention in a stationary operational arrangement; and 
       FIG. 2  shows an application of a sensor in accordance with the invention in a mobile arrangement. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows, in a schematic perspective view, a transport belt  13  moving along a transport direction  11  on whose upper side three shipped packages  15  are arranged. Each shipped package  15  bears a barcode  17 . 
   A sensor  21 , which has a barcode reader  23 , is arranged—as is shown schematically in FIG.  1 —above the transport belt  13  by means of a holder  19 . The barcode reader  23  is equipped—in a manner known per se—with a laser diode as a light transmitter and with a rotating polygon mirror as well as with a photodiode as a light receiver. Furthermore, the sensor  21  has an evaluation and control device for the control of the barcode reader  23  and for the evaluation of the received light signals produced by the barcode reader  23 . 
   The barcode reader  23  is controlled by the evaluation and control device  25  such that it periodically scans a fan-shaped monitored zone  27  by means of the transmitted laser beam. The laser beam appears at the transport belt  13  and at a shipped package  15  located thereon as a scan line  29 . 
   In accordance with the invention, the sensor  21  is equipped with a position signal receiver  31  in the form of a radio antenna unit as well as with an inclination sensor  32  which are connected to the evaluation and control device  25 . The position signal receiver  31  is capable of receiving the reference signals transmitted by a satellite-aided position signal transmission system, of amplifying them and of forwarding them as position detection signals to the evaluation and control device  25 . The inclination sensor  32  transmits an additional position detection signal, which corresponds to the angular position of the sensor  21  with respect to the horizontal, to the evaluation and control device  25 . The evaluation and control device  25  can calculate an absolute spatial position of the position signal receiver  31  in X, Y, Z coordinates, the alignment of the position signal receiver  31  as well as the angular position of the inclination sensor  32  with respect to the horizontal from these position detection signals such that the corresponding position data of the sensor  21  are known. 
   The sensor  21  can also derive the extent and the location of the monitored zone  27  and of the scan line  29  on the basis of these position data. The evaluation and control device  25  can thereby associate an object detection signal of the barcode reader  23 , that is, for example, an identified and a read-in barcode  17 , unambiguously with a spatial position along the transport belt  13 , and thus with a shipped package  15 . The shipped package  15  in question can therefore be subsequently sorted out in accordance with a sorting manner corresponding to the barcode  17  without any confusion arising between the shipped packages  15 . 
   The explained spatial association between an object detection signal of the barcode reader  23  and a barcode  17 , or of a shipped package  15 , can be supported, for example, by incremental transducers which are not shown in FIG.  1  and which deliver a transport position signal representing the transport position or transport speed of the transport belt  13  to the evaluation and control device  25 . 
   The explained embodiment of the sensor  21  with the position signal receiver  31 , the inclination sensor  32  and the evaluation and control device  25  has the advantage that the spatial position and angular position of the sensor  21 , and thus the relative position with respect to the transport belt  13  and to the shipped packages  15  and barcodes  17  located thereon, can be determined in a simple manner without a complex measurement of the sensor  21 , of the monitored zone  27  and of the surrounding space being required for this purpose. 
   This advantageously simple position and location determination can be of particular significance if the sensor  21  should be moved—for example due to a corresponding design of the holder  19 —into different spatial positions or angular positions for different applications. This can be desired, for example, if the transport belt  13  should be reconfigured or if the sensor  21  should monitor an adjacent transport belt at times. 
   In the case of such a position change or location change of the sensor  21 , a spatial association of the monitored zone  2  and of the scan line  29  with the transport belt in question can again be established immediately without problem. For this purpose, the evaluation and control device  25  determines the new spatial position and angular position on the basis of position detection signals which are determined by means of the position signal receiver  31  and of the inclination sensor  32 . The evaluation and control device  25  puts these data into relation with transport position data which represent the transport position of the transport belt  13  or the position of a shipped package  15  located thereon. 
   It must still be noted with respect to the embodiment in accordance with  FIG. 1  that the position signal receiver  31  shown can be formed alternatively or additionally to the reception of reference signals of a satellite-aided transmission system for the reception of corresponding reference signals of a local position signal transmitter. Moreover, it is possible to provide at the sensor  21  only the shown position signal receiver  31  without an inclination sensor  32 , or only the inclination sensor  32  without a position signal receiver. 
     FIG. 2  shows a further application of the sensor in accordance with the invention. A driver-less transport vehicle  33  is shown in a schematic plan view which moves along a corridor between two walls  35  of a warehouse. To allow a collision-free maneuvering, the transport vehicle  33  is equipped with a laser scanner  37  which scans the surroundings—in a known manner—along a monitored zone  27  in the direction of travel by means of a laser beam. The received signals thereby gained on the basis of the light reflection reproduce the actual angular position of the laser scanner and the distance of the respectively reflected object. 
   These received signals are evaluated by means of an evaluation and control device  41  in that the spatial information determined hereby is compared with a spatial data set which represents the plan and design of the warehouse and is stored in a memory device  43  connected to the evaluation and control device  41 . The evaluation and control device  41  delivers an actual direction signal and acceleration/deceleration signal to a drive unit of the transport vehicle  33  (not shown in  FIG. 2 ) on the basis of this comparison. By a constant scanning of the spatial data set stored in the memory device  43 , the transport vehicle  33  can therefore maneuver safely through the warehouse. 
   In accordance with the invention, the laser scanner  37  is coupled via the evaluation and control device  41  to a further evaluation and control device  45  as well as to a position signal receiver  47 , which is connected hereto, and to a gyroscopic sensor  48 . The position signal receiver  47  continuously receives the reference signals of a plurality of local position signal transmitters (not shown) installed inside the warehouse and forwards corresponding position detection signals to the evaluation and control device  45 . The gyroscopic sensor  48  continuously determines its actual alignment within the horizontal plane with respect to a reference alignment determined once and it delivers a corresponding position detection signal to the evaluation and control device  45 . This calculates the actual spatial position and alignment of the transport vehicle  33  with respect to the stored spatial data set from these relative position data. This information is forwarded to the evaluation and control device  41  of the laser scanner  37  so that it can check for control purposes whether the actual position of the transport vehicle  33  was correctly determined on the basis of the data of the laser scanner  37  and of the memory device  43 . 
   This additional control possibility proves to be particularly advantageous, for example, when an obstacle  49 —for example a supervisor—is detected in the monitored zone  39  which is only temporarily located in the warehouse and accordingly is not recorded in the spatial data set stored in the memory device  43 . Whereas such an obstacle  49  can result in a loss of orientation of the transport vehicle  33  under unfavorable circumstances, this danger can be reduced in that additional data on the actual spatial position are made available for comparison purposes on the basis of the position signal receiver  47  coupled to the laser scanner  37 . 
   It must still be remarked with respect to the embodiment in accordance with  FIG. 2  that, alternatively or additionally to the explained position signal receiver  47 , such a receiver can also be provided which receives the reference signals of a satellite-aided position signal transmission system. Furthermore, the gyroscopic sensor  48  is not absolutely necessary. It is also possible to provide only the gyroscopic sensor  48  for the determination of the actual alignment of the transport vehicle  33 , with the position signal receiver  47  being dispensed with.