Monitoring method and optoelectronic sensor

• US 6,940,060 B2
• Filed: 09/04/2002
• Issued: 09/06/2005
• Est. Priority Date: 09/05/2001
• Status: Expired due to Term

• Current Assignee: Sick AG (Sick)
• Original Assignee: Sick AG (Sick)
• Inventors: Henkel, Olaf, Braune, Ingolf
• Primary Examiner(s): Allen, Stephone B.
• Assistant Examiner(s): MONBLEAU, DAVIENNE N
• Application Number:
  US10/235,250
• Publication Number:
  US 20030075675A1
• Time in Patent Office: 1,098 Days
• Field of Search: 250/221, 250/222.1, 250/559.31, 250/559.39, 250/559.4, 340/541, 340555-557
• US Class Current: 250/222.1
• CPC Class Codes: G01S 17/04 Systems determining the presence of a target
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating
• CPC Class Codes: G08B 13/194 using image scanning and comparing systems

Abstract

A zone is monitored with an optoelectronic sensor. Light is transmitted in accordance with a structured light pattern in the direction of the monitored zone and is received from the monitored zone. The received light is converted into received signals and the received signals are evaluated with respect to the presence of an object, or with respect to a movement of an object, in the monitored zone. The light is transmitted and/or received in accordance with at least two different light patterns.

Claims

1. A method of monitoring a monitored zone by means of an optoelectronic sensor, wherein

in accordance with a structured light pattern, transmitted light is transmitted in the direction of the monitored zone and is received from the monitored zone by a reception device;

the received light is converted into received signals; and

the received signals are evaluated with respect to the presence of an object, or with respect to a movement of an object, in the monitored zone,

wherein the transmitted light is transmitted and/or received in accordance with at least two different light patterns, the light patterns being structured in a complementary manner to each other so that, when the monitored zone is object-free, all regions of the reception device are acted upon by the received light.

2. A method in accordance with claim 1, characterized in that the light patterns have a regular structure, with the light patterns being equi-distantly alternating patterns.

3. A method in accordance with claim 1, characterized in that the light patterns are phase-shifted by 180°

with respect to one another.

4. A method in accordance with claim 1, characterized in that the light patterns are linear or of matrix shape.

5. A method in accordance with claim 1, characterized in that the light patterns are light/dark patterns, with the transitions between light and dark regions being continuous or discontinuous.

6. A method in accordance with claim 1, characterized in that the at least two different light patterns are alternatively transmitted and/or received.

7. A method in accordance with claim 1, characterized in that the different light patterns are each produced by an associated transmission device.

8. A method in accordance with claim 1, characterized in that the different light patterns are produced by the use of different optical transmission systems.

9. A method in accordance with claim 1, characterized in that the transmitted light beam and/or a bundle of rays of the received light is deflected, shifted or tilted to produce the different light patterns.

10. A method in accordance with claim 1, characterized in that at least one light pattern is produced by the use of a diffractive optical element.

11. A method in accordance with claim 1, characterized in that transmitted light is received and evaluated which has been reflected or remitted from the monitored zone, or which has substantially passed through the monitored zone in a straight line.

12. A method in accordance with claim 1, characterized in that the transmitted light is transmitted in transmitted pulses, with the reception of the light from the monitored zone taking place in synchronization with the emitting of the transmitted pulses.

13. A method in accordance with claim 1, characterized in that, for the evaluation of the received light, the received signals determined for a specific light pattern, or the data processed from these received signals, are compared with received signals or data which were determined for the same light pattern at a previous time.

14. A method in accordance with claim 13, characterized in that the monitored zone was in an object-free calibration state at the previous time;

or in that the previous time is the time of the directly preceding transmission and/or reception of the same light pattern.

15. A method in accordance with claim 1, characterized in that a test of an error-free reception of light is carried out by comparing the received signals with the transmitted light, wherein the received signals are compared with one another and/or with received signals which were generated when no transmitted light has been transmitted.

16. A method in accordance with claim 15, characterized in that the test is carried out for all different light patterns.

17. A method in accordance with claim 15, characterized in that the reception device has a plurality of reception elements, the received signals are compared with one another by a respective one of the reception elements;

and/or in that a defective reception is detected if the respective reception signals do not differ from one another or differ from one another by less than a predetermined threshold.

18. A method in accordance with claim 15, characterized in that the test is carried out before the start of a subsequent monitoring operation of the optoelectronic sensor;

and/or in that the test is carried out during a monitoring operation of the optoelectronic sensor at regular intervals.

19. A method in accordance with claim 1, characterized in that the method of securing the monitored zone against unauthorized intervention is used;

and in that a switching off signal or a warning signal is produced if the presence of an object, or a movement of an object, in the monitored zone was detected as the result of an evaluation of the received signals.

20. A method in accordance with claim 1, characterized in that the received signals are additionally evaluated with respect to the distance of an object located within the monitored zone by taking into account a beam path which diverges due to a triangulation arrangement.

21. A method in accordance with claim 1, wherein the light patterns have an irregular structure.

22. An optoelectronic sensor for the monitoring of a monitored zone comprising

at least one transmission device for the transmission of a structured transmitted light pattern in the direction of the monitored zone;

at least one reception device defining a plurality of regions for the conversion of light received from the monitored zone into received signals; and

an evaluation device for the evaluation of the received signals with respect to the presence of an object, or a movement of an object, in the monitored zone,

wherein at least one transmission device and/or the at least one reception device is formed for the transmission or reception of at least two different light patterns, and wherein the light patterns are structured in a complementary manner to each other so that, when the monitored zone is object-free, all regions of the reception device are acted upon by the received light.

23. A sensor in accordance with claim 22, characterized in that the transmission device and/or the reception device is formed for the alternating transmission or reception, respectively, of the different light patterns.

24. A sensor in accordance with claim 22, characterized in that a separate transmission device is provided for each light pattern.

25. A sensor in accordance with claim 22, characterized in that a respective separate transmission device is provided for the transmission of the different light patterns.

26. A sensor in accordance with claim 22, characterized in that the reception device has a plurality of reception elements.

27. A sensor in accordance with claim 22, characterized in that a displaceable or tiltable transmission device and/or reception device is provided.

28. A sensor in accordance with claim 22, characterized in that the transmission device and/or the reception device has at least one diffractive optical element.

29. A sensor in accordance with claim 22, characterized in that the transmission device and the reception device are arranged in a reflection arrangement or in a transmission arrangement.

30. A sensor in accordance with claim 22, characterized in that the received signals which are determined for a specific light pattern can be compared by the evaluation device with received signals which were determined at a previous time for the same light pattern.

31. A sensor in accordance with claim 22, characterized in that, for a test of an error-free reception of light, the received signals light are compared by the evaluation device with reception signals which are determined when no transmitted light was transmitted.