OPTOELECTRONIC SENSOR

• US 20120074296A1
• Filed: 08/12/2011
• Published: 03/29/2012
• Est. Priority Date: 09/23/2010
• Status: Active Grant

• Current Assignee: Sick AG (Sick)
• Original Assignee: Sick AG (Sick)
• Inventors: HAMMES, Markus, BRAUNE, Ingolf, MACNAMARA, Shane, SCHMITZ, Stephan
• Granted Patent: US 8,735,792 B2
• Time in Patent Office: Days
• US Class Current: 250/205
• CPC Class Codes: G06V 10/141 Control of illumination

Abstract

An optoelectronic sensor (10) for monitoring a working area (42) is provided, the working area (42) being located within a detection area (20) of the sensor (10) and in a first distance from the sensor (10), wherein the sensor (10) comprises an illumination unit (22) with a light source (24) for at least partially illuminating the working area (42), and an object detection unit (30) for detecting forbidden objects in the working area (42), wherein an illumination control (28) of the illumination unit (22) is configured to, during a startup period,

• • initially activate the illumination unit (28) with a lower power such that a provisional working area (40, 40a-c) in a second distance from the sensor (10) less than the first distance is illuminated at most with a predetermined maximum light output;
  • test whether there is a forbidden object intrusion into the provisional working area (40, 40a-c); and
  • if no forbidden object intrusion is detected, activate the illumination unit (28) with a higher power such that the working area (42) is illuminated at most with the predetermined maximum light output.
    The illumination control (28) comprises a short range object detection unit (39) configured to test the provisional working area (40, 40a-c) in a different way than the object detection unit (30) tests the working area (42).

Claims

1. An optoelectronic sensor (10) for monitoring a working area (42), the working area (42) being located within a detection area (20) of the sensor (10) and in a first distance from the sensor (10), wherein the sensor (10) comprises an illumination unit (22) with a light source (24) for at least partially illuminating the working area (42), and an object detection unit (30) for detecting forbidden objects in the working area (42),

wherein an illumination control (28) of the illumination unit (22) is configured to, during a startup period,

initially activate the illumination unit (28) with a lower power such that a provisional working area (40, 40a-c) in a second distance from the sensor (10) less than the first distance is illuminated at most with a predetermined maximum light output;

test whether there is a forbidden object intrusion into the provisional working area (40, 40a-c); and

if no forbidden object intrusion is detected, activate the illumination unit (28) with a higher power such that the working area (42) is illuminated at most with the predetermined maximum light output,

characterized in that

the illumination control (28) comprises a short range object detection unit (39) configured to test the provisional working area (40, 40a-c) in a different way than the object detection unit (30) tests the working area (42).

2. The sensor (10) of claim 1,

wherein the illumination control (28) is configured to operate the illumination unit (22) as a pulsed illumination and to control the power of the illumination unit (22) by means of at least one of a power of single pulses, a pulse repetition frequency, and a pulse length.

3. The sensor (10) of claim 1,

wherein the short range object detection unit (39) comprises an additional short range detector.

4. The sensor (10) of claim 1,

wherein the short range object detection unit (39) is configured to detect forbidden objects from a saturation of a light receiver (16) of the sensor (10).

5. The sensor (10) of claim 1,

that is made as a distance-measuring optoelectronic sensor, in particular a stepreoscopic 3D-camera, a three dimensional time-of-flight camera, or a laser scanner.

6. The sensor (10) of claim 5,

that is made as a stereoscopic camera with at least two image sensors (16) and a stereoscopic evaluation unit for generating a depth map from images of the image sensors (16).

7. The sensor (10) of claim 6,

wherein the short range object detection unit (39) is configured to detect forbidden objects from gaps in the depth map that affect more than a maximum number of pixels.

8. The sensor (10) of claim 6,

wherein the short range object detection unit (39) is configured to detect forbidden objects from differences between the respective simultaneously generated images of the two image sensors that affect more than a maximum number of pixels.

9. The sensor (10) of claim 1,

wherein the illumination control (28) is configured to de-energize the illumination unit (22) or to restart the startup period if a forbidden object intrusion into the provisional working area (40, 40a-c) is detected.

10. The sensor (10) of claim 1,

wherein the illumination control (28) is configured to increase the second distance up to the first distance in distance increments and to activate the illumination unit (22) with a higher power upon increase of the second distance such that the respective provisional working area (42) in the modified second distance is illuminated at most with the predetermined maximum light output.

11. The sensor (10) of claim 10,

wherein the distance increments are so small that the provisional working area (42) runs through the interval of the original second distance to the first distance virtually continuously.

12. The sensor (10) of claim 10,

wherein the distance increments correspond to a depth dimension of the working area (42).

13. The sensor (10) of claim 1,

wherein a shut down device (36) is provided that is configured to detect forbidden object intrusions into the working area (42) by means of the object detection unit (30) in an operating phase following the startup period and to output a shutdown signal if a forbidden intrusion is detected.

14. The sensor (10) of claim 1,

wherein the illumination unit (22) comprises a laser light source (24) and a pattern generating element (26) for generating a structured light pattern in the provisional working area (40;

40a-c) or the working area (42).

15. A method for monitoring a working area (42), the working area (42) being located within a detection area (20) of an optoelectronic sensor (10) and in a first distance from the sensor (10), wherein the working area is at least partially illuminated by means of an illumination unit (22), and wherein forbidden objects in the working area (42) are detected in an object detection, wherein, during a startup period,

the illumination unit (28) is initially activated with a lower power such that a provisional working area (40, 40a-c) in a second distance from the sensor (10) less than the first distance is illuminated at most with a predetermined maximum light output;

it is tested, in a short range detection, whether there is a forbidden object intrusion into the provisional working area (40, 40a-c); and

if no forbidden object intrusion is detected, the illumination unit (28) is activated with a higher power such that the working area (42) is illuminated at most with the predetermined maximum light output,

characterized in that

the short range object detection uses a different method than the object detection.

16. The method of claim 15,

wherein the illumination unit (22) transmits a pulsed illumination, and wherein the power of the illumination is controlled by means of at least one of a power of single pulses, a pulse repetition frequency, and a pulse length.

17. The method of claim 15,

wherein, in the short range object detection, forbidden objects are detected from a saturation of a light receiver (16) of the sensor (10).

18. The method of claim 15,

wherein two image sensors (16) of the sensor (10) take images of the detection area (20), a depth map is generated from two respective, simultaneously taken images by stereoscopic evaluation, and the short range object detection detects forbidden objects from gaps in the depth map that affect more than a maximum number of pixels or from differences between the two simultaneously taken images that affect more than a maximum number of pixels.

19. The method of claim 15,

wherein the illumination unit (22) is de-energized or the startup period is restarted if a forbidden object intrusion into the provisional working area (40, 40a-c) is detected.

20. The method of claim 15,

wherein the second distance is increased up to the first distance in distance increments, and the illumination unit (22) is activated with a higher power upon increase of the second distance such that the respective provisional working area (42) in the modified second distance is illuminated at most with the predetermined maximum light output, wherein in particular the distance increments are so small that the provisional working area (42) runs through the interval of the original second distance to the first distance virtually continuously or wherein the distance increments correspond to a depth dimension of the working area (42).