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

• US 8,724,096 B2
• Filed: 12/19/2011
• Issued: 05/13/2014
• Est. Priority Date: 12/21/2010
• Status: Active Grant

• Current Assignee: Sick AG (Sick)
• Original Assignee: Sick AG (Sick)
• Inventors: Feise, Gerold, Albert, Michael, Gosch, Kirsten, Jgel, Matthias
• Primary Examiner(s): RATCLIFFE, LUKE D
• Application Number:
  US13/330,169
• Publication Number:
  US 20120154786A1
• Time in Patent Office: 876 Days
• Field of Search: 356 301- 315, 356 401- 41, 356 501- 515, 356 6- 22, 356/28, 356/28.5
• US Class Current: 356/5.01
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/483 Details of pulse systems
• CPC Class Codes: G01S 7/4861 Circuits for detection, sampling, integration or read-out
• CPC Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection
• CPC Class Codes: G01S 7/4876 by removing unwanted signals G01S7/495 takes precedence

Abstract

An optoelectronic sensor for the detection and distance determination of objects in a monitoring area is provided having a light transmitter for transmitting a plurality of light pulses, a rotatable deflecting unit, an angle detector, a light receiver, and an evaluation unit which is configured to collect a plurality of reception pulses in a time histogram to determine the light time of flight from the sensor to an object. The evaluation unit is configured to select a respective group of reception pulses that is collected in a histogram based on the angular position signal and to assign the measured value for the object distance determined from the histogram of the group to a detection angle identified by the angular position signal.

Claims

1. An optoelectronic sensor (10) comprising:

a laser scanner, for the detection and distance determination of objects in a monitoring area (20);

a light transmitter (12) for transmitting a transmission light beam (16) with a plurality of successive individual light pulses (54);

a rotatable deflecting unit (18) for periodically deflecting the transmission light beam (16) in the monitoring area (20);

an angle encoding unit (30) for generating angular position signals (58) in dependence on an angle position of the deflecting unit (18);

a light receiver (26) for generating reception pulses (102) from the transmission light reflected or remitted by objects in the monitoring area (20); and

an evaluation unit (32) which is configured to collect a plurality of reception pulses (102) in a time histogram (110) and to determine the light time of flight from the sensor (10) to an object from the histogram (110) and, from that, a measured value for the object distance, wherein the evaluation unit (32) is configured to select a respective group (56) of reception pulses (102) that is collected in a histogram (110) based on the angular position signal (58) and to assign the measured value for the object distance determined from the histogram (110) of the group (56) to a detection angle identified by the angular position signal (58), and

wherein the evaluation unit (32) is configured to make the selection of reception pulses (102) to a group (56) with a time delay.

2. The sensor (10) of claim 1,

wherein the angle encoding unit (30) provides angular position signals (58) of a preset angular resolution.

3. The sensor (10) of claim 1,

wherein the evaluation unit (32) is configured to select a preset number of reception pulses (102) for a group (56) to a respective angular position signal (58).

4. The sensor (10) of claim 3,

wherein the number of individual light pulses (54) and the time difference between two respective individual light pulses (54) is small enough to allow a time buffer between the last reception pulse of a group (56) and the subsequent angel position signal (58).

5. The sensor (10) of claim 3,

wherein the evaluation unit (32) is configured to test whether there is an additional angular position signal (58) during the time interval in which the preset number of reception pulses (102) is detected, and to in that case assign the measured value for the object distance determined from the histogram (110) of the group (56) to that angular position signal (58) to which the majority of the reception pulses (102) belong.

6. The sensor (10) of claim 5,

wherein the evaluation unit (32) is configured to assign the measured value for the object distance determined from the histogram (110) of the group (56) to that angular position signal (58) from which the added time differences to the reception pulses (102) of the group (56) are minimal.

7. The sensor (10) of claim 1,

wherein the evaluation unit (32) comprises at least two evaluation channels (32a, 32b) to collect reception pulses in each evaluation channel in its own histogram (110) and to determine the light time of flight from the sensor (10) to an object and from that a measured value for the object distance from the histogram (110).

8. The sensor (10) of claim 7,

wherein the evaluation channels (32a, 32b) are configured for an overlapping evaluation, where the evaluation channels (32a, 32b) alternately select a preset number of reception pulses (102) following an angular position signal (58) for a group (56).

9. The sensor (10) of claim 7,

wherein the evaluation channels (32a, 32b) are configured for a parallel evaluation.

10. The sensor (10) of claim 7,

wherein the evaluation channels (32a, 32b) are configured to use different criteria for the selection of reception pulses (102) of a group (56).

12. The sensor (10) of claim 1,

wherein an analog preprocessor (44) is provided that comprises a filter (48) to convert the reception pulse (102) into a bipolar preprocessed signal (104) which is fed to an A/D converter (52) of the evaluation unit (32).

13. The sensor (10) of claim 12,

wherein the analog preprocessor (44) comprises a limiting amplifier (50) for amplifying the positive component and the negative component of the bipolar preprocessed signal (104) to a saturation value.

14. The sensor (10) of claim 12,

wherein the A/D converter (52) is a binarizer.

15. The sensor (10) of claim 1,

comprising a parameterization unit (34) to set a higher angular resolution at a lower range of the sensor (10) or vice versa.

16. The sensor (10) of claim 1,

wherein the histogram (110) is initialized with initial values even before collecting reception pulses (102).

17. The sensor (10) of claim 16,

wherein the initial values vary in dependence on the detection angle.

18. The sensor (10) of claim 16,

wherein the initial values are determined by a calibration measurement in a reference state of the monitoring area (20).

19. The sensor (10) of claim 18,

wherein the initial values are determined by a calibration measurement to initialize with a front screen reflection and thus compensate for it.

11. An optoelectronic sensor (10) comprising:

a laser scanner, for the detection and distance determination of objects in a monitoring area (20);

a light transmitter (12) for transmitting a transmission light beam (16) with a plurality of successive individual light pulses (54);

a rotatable deflecting unit (18) for periodically deflecting the transmission light beam (16) in the monitoring area (20);

an angle encoding unit (30) for generating angular position signals (58) in dependence on an angle position of the deflecting unit (18);

a light receiver (26) for generating reception pulses (102) from the transmission light reflected or remitted by objects in the monitoring area (20); and

an evaluation unit (32) which is configured to collect a plurality of reception pulses (102) in a time histogram (110) and to determine the light time of flight from the sensor (10) to an object from the histogram (110) and, from that, a measured value for the object distance,

wherein the evaluation unit (32) is configured to select a respective group (56) of reception pulses (102) that is collected in a histogram (110) based on the angular position signal (58) and to assign the measured value for the object distance determined from the histogram (110) of the group (56) to a detection angle identified by the angular position signal (58), and

wherein the evaluation unit (32) is configured to adapt the number of reception pulses (102) in a group (56) in dependence on at least one of the detection angle and an object distance previously determined.

20. A method for the detection and distance determination of objects in a monitoring area (20),

wherein a transmission light beam (16) with a plurality of successive individual light pulses (54) is transmitted, the transmission light beam (16) scans the monitoring area (20) by periodic deflection, and reception pulses (102) are generated from the transmission light reflected or remitted from objects in the monitoring area (20),

wherein the angle of deflection is determined by an angular position signal (58), a plurality of reception pulses (102) is collected in a time histogram (110) and the light time of flight to an object is determined from the histogram (110) and, from that, a measured value for the object distance is determined,

wherein a respective group (56) of reception pulses (102) that is collected in a histogram (110) is selected based on the angular position signal (58), and the measured value for the object distance determined from the histogram (110) of the group (56) is assigned to a detection angle identified by the angular position signal (58), and

wherein an evaluation unit (32) is configured to make the selection of reception pulses (102) to a group (56) with a time delay.

21. A method for the detection and distance determination of objects in a monitoring area (20),

wherein a transmission light beam (16) with a plurality of successive individual light pulses (54) is transmitted, the transmission light beam (16) scans the monitoring area (20) by periodic deflection, and reception pulses (102) are generated from the transmission light reflected or remitted from objects in the monitoring area (20),

wherein the angle of deflection is determined by an angular position signal (58), a plurality of reception pulses (102) is collected in a time histogram (110) and the light time of flight to an object is determined from the histogram (110) and, from that, a measured value for the object distance is determined,

wherein a respective group (56) of reception pulses (102) that is collected in a histogram (110) is selected based on the angular position signal (58), and the measured value for the object distance determined from the histogram (110) of the group (56) is assigned to a detection angle identified by the angular position signal (58), and

wherein an evaluation unit (32) is configured to adapt the number of reception pulses (102) in a group (56) in dependence on at least one of the detection angle and an object distance previously determined.