Optoelectronic sensor

• US 8,050,570 B2
• Filed: 07/08/2008
• Issued: 11/01/2011
• Est. Priority Date: 07/10/2007
• Status: Active Grant

• Current Assignee: Sick AG (Sick)
• Original Assignee: Sick AG (Sick)
• Inventors: Kohler, Markus, Geiler, Martin, Szerbakowski, Boris, Schmitz, Stephan, Hammes, Markus
• Primary Examiner(s): Bello; Agustin
• Application Number:
  US12/216,626
• Publication Number:
  US 20090016735A1
• Time in Patent Office: 1,211 Days
• Field of Search: 398118-131
• US Class Current: 398/130
• CPC Class Codes: G01V 8/12 using one transmitter and one receiver

Abstract

An optoelectronic sensor includes at least one light transmitter for the transmission of light signals into a monitored zone, at least one light receiver for the reception of light signals transmitted from the light transmitter and a control device for the generation and/or influencing of the light signals and for the generation of an object detection signal in the case of the presence of an object in the monitored region in dependence on the output signals of the light receiver. In this connection, the light signals transmitted into the monitored zone by the light transmitter are each generated by an output signal modulated in accordance with the spread spectrum method using a random pseudo-noise code.

Claims

1. An optoelectronic sensor having at least one light transmitter for the transmission of light signals into a monitored zone, at least one light receiver for the reception of light signals transmitted by the light transmitter and a control device for the generation and/or influencing of the light signals and for the generation of an object detection signal in the case of the presence of an object in the monitored zone in dependence on the output signals of the light receiver,

characterized in that

the light signals transmitted into the monitored zone by the light transmitter are each generated by an output signal modulated in accordance with a the spread spectrum method using a random pseudo-noise code,

the light signal received by the light receiver can be acted on by the random pseudo-noise code associated with the respective light transmitter for the identification of the output signal associated with a respective light transmitter,

the control device includes means to form an autocorrelation function between the received light signal and the respective random pseudo-noise code for the identification of the output signal associated with a respective light transmitter, and

the control device includes means to set a variable time offset between the random pseudo-noise code and the received light signal acted on by it such that a maximum value results for the autocorrelation function.

2. An optoelectronic sensor in accordance with claim 1, characterized in that the random pseudo-noise code is generated via a so-called primitive polynomial.

3. An optoelectronic sensor in accordance with claim 1, characterized in that the random pseudo-noise code includes an M sequence.

4. An optoelectronic sensor in accordance with claim 1, characterized in that the random pseudo-noise code includes a Gold sequence.

5. An optoelectronic sensor in accordance with claim 1, characterized in that the random pseudo-noise code includes a Kasami sequence.

6. An optoelectronic sensor in accordance with claim 1, characterized in that the random pseudo-noise code includes a Hadamard-Walsh sequence.

7. An optoelectronic sensor in accordance with claim 1, characterized in that the random pseudo-noise code includes a Barker sequence.

8. An optoelectronic sensor in accordance with claim 1, characterized in that the light signals transmitted into the monitored zone by the light transmitter are each generated by an output signal modulated in accordance with a direct sequence spread spectrum (DSSS) method using the random pseudo-noise code.

9. An optoelectronic sensor in accordance with claim 1, characterized in that the light signals transmitted into the monitored zone by the light transmitter are each generated by at least one light pulse mixed using the random pseudo-noise code.

10. An optoelectronic sensor in accordance with claim 1, characterized in that different random pseudo-noise codes are associated with different light transmitters.

11. An optoelectronic sensor in accordance with claim 1, characterized in that a common light receiver is associated with a respective at least two light transmitters.

12. An optoelectronic sensor in accordance with claim 1, characterized in that a common light receiver is associated with a respective at least three light transmitters.

13. An optoelectronic sensor in accordance with claim 1, characterized in that a common light receiver is associated with different light transmitters with which different random pseudo-noise codes are associated;

and in that the light signals received by the common light receiver and/or a signal formed therefrom for the identification of the output signals associated with the respective light transmitters are acted on by the random pseudo-noise codes associated with the respective light transmitters.

14. An optoelectronic sensor in accordance with claim 1, characterized in that the light transmitters and the light receivers are arranged on mutually oppositely disposed sides of the monitored zone.

15. An optoelectronic sensor in accordance with claim 1, characterized in that the light transmitters and the light receivers are arranged on one side of the monitored zone and a retroreflector is arranged on the oppositely disposed side of the monitored zone.

16. An optoelectronic sensor in accordance with claim 1, characterized in that a plurality of light transmitters and light receivers are provided in a light grid arrangement.

17. An optoelectronic sensor in accordance with claim 1, characterized in that a common light receiver is associated with a respective plurality of light transmitters and the number of light receivers is correspondingly less than the number of light transmitters.

18. An optoelectronic sensor in accordance with claim 1, characterized in that it includes at least one camera, in particular a secure and/or reliable camera, with which at least one light transmitter is associated for the active illumination of the monitored zone with the light signals of said light transmitter transmitted into the monitored zone being generated by an output signal modulated in accordance with the spread spectrum method using a random pseudo-noise code.

19. An optoelectronic sensor in accordance with claim 18, characterized in that the light transmitter associated with the camera and/or the camera are controlled by the associated control device such that the active illumination takes place synchronously with the lighting of the sensitive surface of the camera.

20. An optoelectronic sensor in accordance with claim 18, characterized in that a 3D stereoscopic camera is provided as the camera.

21. An optoelectronic sensor in accordance with claim 18, characterized in that a structured pattern, in particular a high-contrast pattern, is generated in the illuminated monitored zone by means of the light transmitter associated with the camera.

22. An optoelectronic sensor in accordance with claim 1, characterized in that the control device is designed such that at least one respective two-fold evaluation of output signals of the light receiver takes place for the generation of a respective object detection signal.

23. An optoelectronic sensor in accordance with claim 22, characterized in that the control device is made such that a respective object detection signal is only generated when it was found at least twice sequentially in time that no light signal was received by the light receiver which can be associated with the respective light transmitter.

24. An optoelectronic sensor in accordance with claim 23, characterized in that the control device includes means to form the autocorrelation function between the respective received light signal and the respective random pseudo-noise code at least twice sequentially in time for the identification of a respective output signal associated with the respective light transmitter.

25. An optoelectronic sensor in accordance with claim 24, characterized in that the at least two light signals transmitted by the respective light transmitter for the at least two-fold evaluation sequentially in time are offset in time such that a different time offset results between the random pseudo-noise code and the respective received light signals acted on by this random pseudo-noise code.

26. An optoelectronic sensor in accordance with claim 22, characterized in that different chip periods for the respective random pseudo-noise code are selected for the at least two evaluations.

27. An optoelectronic sensor in accordance with claim 22, characterized in that, at the reception side, a defined detection threshold is provided for each light signal transmitted by the light transmitter.

28. An optoelectronic sensor in accordance with claim 22, characterized in that the length of the random pseudo-noise code sequence is selected in dependence on the number of non-overlapping transmitted light signals activated at the same time.

29. An optoelectronic sensor in accordance with claim 22, characterized in that the random pseudo-noise code is split into at least two chip sequences for the realization of a combined TDMA and CDMA system.