Optoelectric sensor and method for the detection and distance determination of objects

1. An optoelectronic sensor ( 10 ) for the detection and distance determination of objects in a monitoring area ( 18 ), the sensor ( 10 ) comprising:

a light transmitter ( 12 ) for transmitting a transmission light beam ( 14 ) having a plurality of consecutive individual light pulses;

a rotatable deflection unit ( 16 ) for a periodic deflection of the transmission light beam ( 14 ) in the monitoring area ( 18 );

an angle measuring unit ( 28 ) for determining an angular position of the deflection unit ( 16 );

a light receiver ( 24 ) for generating reception pulses from transmission light remitted or reflected by objects in the monitoring area ( 18 );

at least one histogram memory ( 34 ); and

an evaluation unit ( 30 ) which is configured to accumulate a time histogram from a plurality of reception pulses in the histogram memory ( 34 ) and to determine, from the histogram, a light time of flight from the sensor ( 10 ) to an object and therefrom an object distance,

wherein a plurality of histogram memories ( 34 ) is provided, each associated with an angular position,

and the evaluation unit ( 30 ) is configured to intermittently accumulate time histograms in the histogram memories ( 34 ) across several rotations of the deflection unit ( 16 ) from reception pulses which are each detected at the same angular position associated with the respective histogram memory ( 34 ), and to determine the object distance for an angular position from the histogram of the associated histogram memory ( 34 ).

2. The sensor ( 10 ) according to claim 1 ,

wherein the optoelectronic sensor is a laser scanner.

3. The sensor ( 10 ) according to claim 1 ,

wherein the evaluation unit ( 30 ) is configured to add one and only one reception pulse to the histograms per period of the rotational movement of the deflection unit ( 16 ).

4. The sensor ( 10 ) according to claim 1 ,

wherein the evaluation unit ( 30 ) is configured to add several consecutive reception pulses to the histograms per period of the rotational movement of the deflection unit ( 16 ).

5. The sensor ( 10 ) according to claim 1 ,

wherein the evaluation unit ( 30 ) is configured to add a reception pulse to several histograms in histogram memories ( 34 ) associated with adjacent angular positions.

6. The sensor ( 10 ) according to claim 1 ,

wherein the evaluation unit ( 30 ) is configured to divide the histogram memories ( 34 ) into a plurality of groups and to evaluate the histograms accumulated in the histogram memories ( 34 ) in a staggered manner over a corresponding number of periods of the rotational movement of the deflection unit ( 16 ) by determining the light time of flight from histograms of histogram memories ( 34 ) of one group in one period.

7. The sensor ( 10 ) according to claim 1 ,

wherein the deflection unit ( 16 ) has a rotational speed of at least 10,000 revolutions per minute.

8. The sensor ( 10 ) according to claim 1 ,

wherein the histogram memories ( 34 ) are FIFO memories so that when the most recent reception pulse is added the oldest reception pulse is deleted.

9. The sensor ( 10 ) according to claim 1 ,

wherein the evaluation unit ( 30 ) is configured to periodically let values in the histogram memories ( 34 ) fade and to increase the values for a new reception pulse to be added.

10. The sensor ( 10 ) according to claim 1 ,

wherein the evaluation unit ( 30 ) is configured to determine a light time of flight from the histograms with an evaluation period shorter than the period required to accumulate a complete histogram.

11. The sensor according to claim 1 ,

wherein the evaluation unit ( 30 ) is configured to determine a light time of flight form the histogram once per period of the rotational movement of the deflection unit ( 16 ).

12. The sensor ( 10 ) according to claim 1 ,

wherein the reception pulses are accumulated in the histograms following a binarization.

13. The sensor ( 10 ) according to claim 1 ,

wherein the evaluation unit ( 30 ) is configured to compare the object distances determined in dependence on angular positions with predefined protection zones in order to detect an object intrusion into a protection zone and to then output a safety-related shutdown signal.

14. A method for the detection and distance determination of objects in a monitoring area ( 18 ), wherein

a transmission light beam ( 14 ) having a plurality of consecutive individual light pulses is transmitted and periodically scans the monitoring area ( 18 ) by means of a rotatable deflection unit ( 16 ) whose respective angular position is measured,

reception pulses are generated from transmission light remitted or reflected by objects in the monitoring area ( 18 ),

a time histogram is intermittently accumulated from a plurality of reception pulses in at least one histogram memory ( 34 ), and

a light time of flight to an object and therefrom an object distance is determined,

wherein time histograms are intermittently accumulated in a plurality of histogram memories ( 34 ) each associated with an angular position,

time histograms are intermittently accumulated in the histogram memories ( 34 ) across several rotations of the deflection unit ( 16 ) from reception pulses which are each detected at the angular position associated with the respective histogram memory ( 34 ), and

the object distance for an angular position is determined from the histogram of the associated histogram memory ( 34 ).

15. The method of claim 14 ,

wherein several consecutive reception pulses are added to a histogram.

16. The method of claim 14 ,

wherein the histograms are accumulated and evaluated in a moving window.

17. The method of claim 14 ,

wherein the object distances determined in dependence on angular positions are compared with predefined protection zones in order to detect an object intrusion into a protection zone and in that case a safety-related shutdown signal is output.