Optoelectric Sensor and Method for the Detection and Distance Determination of Objects

• US 20150015868A1
• Filed: 06/19/2014
• Published: 01/15/2015
• Est. Priority Date: 07/11/2013
• Status: Active Grant

• Current Assignee: Sick AG (Sick)
• Original Assignee: Sick AG (Sick)
• Inventors: JACHMAN, Fabian, FRANZREB, Simon
• Granted Patent: US 9,383,201 B2
• Time in Patent Office: Days
• US Class Current: 356/5.01
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/486 Receivers

Abstract

An optoelectronic sensor (10) for distance determination comprises a transmitter (12) for transmitting a light beam (14) having a plurality of consecutive individual light pulses, a rotatable deflection unit (16) for deflecting the light beam (14), an angle measuring unit (28) for determining an angular position of the deflection unit (16), a light receiver (24) for generating reception pulses from remitted transmission light, a plurality of histogram memories (34) each associated with an angular position, and an evaluation unit (30) which is configured to accumulate time histograms in the histogram memodes (34) across several periods of the rotational movement of the deflection unit (16) from reception pulses which are each detected at the angular position associated with the respective histogram memory (34), and to determine, from the histograms of the associated histogram memory (34), an object distance for an angular position.

Claims

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,

characterized in that

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

and in that the evaluation unit (30) is configured to accumulate time histograms in the histogram memories (34) across several periods of the rotational movement of the deflection unit (16) from reception pulses which are each detected at the 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 the 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 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,

characterized in that

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

time histograms are accumulated in the histogram memories (34) across several periods of the rotational movement 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.