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EP-4741872-A1 - OPTOELECTRONIC SENSOR FOR DETECTING OBJECTS IN A SURVEILLANCE AREA

EP4741872A1EP 4741872 A1EP4741872 A1EP 4741872A1EP-4741872-A1

Abstract

The invention relates to an optoelectronic sensor, in particular a time-of-flight camera or a LiDAR sensor, for detecting at least one object in a monitoring area, wherein the optoelectronic sensor comprises a light transmitter, a light receiver, and an evaluation unit. The light transmitter is configured to emit light into the monitoring area. The light receiver is configured to receive light reflected from the monitoring area. The evaluation unit is designed to acquire distance data over the monitored area based on the received light, wherein the distance data includes intensity values and associated distance values, to determine a distance to the object, in particular to the edge of the object, for all those data components in the distance data that do not originate from the object, and in particular for all those data components whose intensity value is less than a first intensity limit, based on the distance data, and based on the determined distance of the data component in question to the object, based on a model for the scattered light behavior of the optoelectronic sensor and based on the intensity value of the data component in question, to determine a probability value that the data component in question represents a disturbance, and to recognize as a disturbance all those data components whose determined probability value is equal to or greater than a probability limit.

Inventors

  • Kingston, Michael

Assignees

  • SICK AG

Dates

Publication Date
20260513
Application Date
20251017

Claims (14)

  1. Optoelectronic sensor (100), in particular a time-of-flight camera or a LiDAR sensor, for detecting at least one object (40) in a monitored area, wherein the optoelectronic sensor (100) comprises a light transmitter (10), a light receiver (20) and an evaluation unit (30), wherein the light transmitter (10) is designed to emit transmitting light (11) into the monitoring area, wherein the light receiver (20) is configured to receive received light (12) reflected from the monitoring area, and wherein the evaluation unit (30) is configured to based on the received light (12) to obtain distance data over the monitoring area, wherein the distance data include intensity values and associated distance values, for all those data components (21) in the distance data that do not originate from the object (40), and in particular for all those data components (21) whose intensity value is less than a first intensity limit, to determine a distance to the object (40), in particular to the edge of the object (40), based on the distance data, and in each case based on the determined distance of the relevant data component (21) to the object (40), based on a model (61, 62, 63) for the scattered light behavior of the optoelectronic sensor (100) and based on the intensity value of the relevant data component (21) a probability value to determine that the relevant data segment (21) represents a disturbance, and to identify as disturbances all those data components (21) whose determined probability value is equal to or greater than a probability limit.
  2. Optoelectronic sensor (100) according to claim 1, wherein the evaluation unit (30) is configured to determine a distance, size, intensity and/or remission of the remitting object (40) based on the distance data.
  3. Optoelectronic sensor (100) according to claim 2, wherein the probability value that the relevant data component (21) represents a disturbance is determined as a function of the determined distance of the relevant data component to the object (40), the intensity value of the relevant data component (21), the maximum measurable intensity, and the size of the object (40).
  4. Optoelectronic sensor (100) according to claim 2 or 3, wherein the evaluation unit (30) is configured to determine the size of the remitting object (40) based on those data components in the distance data whose intensity value is equal to or greater than the first intensity limit value.
  5. Optoelectronic sensor (100) according to one of claims 2 to 4, wherein the evaluation unit (30) is configured to perform the detection of those data components (21) in the distance data that represent a disturbance only if the determined size of the object (40) is equal to or greater than a predetermined size limit, or if the determined remission of the object (40) is equal to or greater than a predetermined Remission limit is and/or if the determined intensity of the object (40) is equal to or greater than a second intensity limit.
  6. Optoelectronic sensor (100) according to one of claims 2 to 5, wherein the distance data comprise a plurality of pixels, each with an intensity value and an associated distance value, and wherein the evaluation unit (30) is configured to to determine the size of the object (40) based on those pixels in the distance data whose intensity value is equal to or greater than the first intensity limit, wherein the size of the object (40) is preferably determined as the number of pixels, and for each pixel (21) whose intensity value is less than the first intensity limit, to determine a distance to the nearest pixel of the object (40), wherein the distance to the object (40) is preferably determined as a number of pixels, and to determine the probability value that the relevant pixel (21) represents a disturbance, depending on its intensity value, its determined distance to the nearest pixel of the object (40), the maximum measurable intensity and/or the intensity of the object (40), and the size of the object (40), and to identify all those pixels (21) as disturbances whose probability value is equal to or greater than the probability limit.
  7. Optoelectronic sensor (100) according to one of the preceding claims, wherein the evaluation unit (30) is configured to to determine the distance of the remitting object (40) using the distance data, and to identify as disturbances all those data components (21) whose probability value is equal to or greater than the probability limit and whose associated distance value lies within a tolerance range around the determined distance of the object (40).
  8. Optoelectronic sensor (100) according to claim 7, where the distance data comprise a multitude of pixels, each with an intensity value and an associated distance value, and wherein the evaluation unit (30) is trained to to plot each pixel in the distance data whose intensity value is equal to or greater than the first intensity threshold into a distance histogram, to identify a peak in the distance histogram, wherein the peak is preferably the largest peak in the distance histogram, to determine the size of the object (40) based on the number of pixels under the peak, and to determine the distance of the object (40) based on the position of the peak in the distance histogram.
  9. Optoelectronic sensor (100) according to one of the preceding claims, wherein the data components (21) detected as interference in the distance data, in particular for controlling the movement of a robot, are removed from the distance data, marked as invalid, and/or ignored in a further evaluation of the distance data.
  10. Optoelectronic sensor (100) according to one of the preceding claims, wherein the object (40) comprises a reflector, and preferably a retroreflector.
  11. System comprising at least one optoelectronic sensor (100) according to one of claims 1 to 10 and at least one autonomous robot, wherein the optoelectronic sensor (100) is preferably mounted on the autonomous robot and can be moved by it.
  12. Use of an optoelectronic sensor (100) according to any one of claims 1 to 10 for detecting at least one object (40) in a monitoring area.
  13. Method for detecting at least one object (40), in particular a reflector, preferably a retroreflector, in a monitoring area, wherein transmitted light (11) is emitted into the monitoring area; wherein received light (12) reflected from the monitoring area is received; wherein distance data over the monitored area are obtained based on the received light (12), and in particular are measured using a time-of-flight method, wherein the distance data include intensity values and associated distance values; where for all those data components in the distance data that do not originate from the object (40), and in particular for all those data components (21) whose intensity value is less than a first intensity limit, In each case, a distance to the object (40), in particular to the edge of the object (40), is determined based on the distance data, and In each case, a probability value is determined based on the determined distance of the relevant data component (21) to the object (40), based on a model (61, 62, 63) for the scattered light behavior of the optoelectronic sensor (100), and based on the intensity value of the relevant data component (21), indicating that the relevant data component (21) represents a disturbance; and wherein all those data components (21) in the distance data are identified as disturbances whose determined probability value is equal to or greater than a predetermined probability limit.
  14. Method according to claim 13, where a distance of the remitting object (40) is determined based on the distance data; and wherein all those data components (21) are recognized as disturbances whose probability value is equal to or greater than the probability limit and whose associated distance value lies within a tolerance range around the determined distance of the object (40).

Description

The invention relates to an optoelectronic sensor, in particular a time-of-flight camera or a LiDAR sensor, for detecting at least one object in a monitoring area, wherein the optoelectronic sensor comprises means for recognizing data components in acquired distance data over the monitoring area as disturbances. Optoelectronic sensors can be used for industrial safety applications and enable safe environmental perception of a monitored area, particularly safe three-dimensional environmental perception, thereby increasing the safety and efficiency of industrial processes in industrial plants. Examples of such optoelectronic sensors include Time-of-Flight (ToF) cameras and LiDAR (Light Detection and Ranging) sensors. Optoelectronic sensors can be, for example, stationary within the industrial plant or mounted on robots that can move autonomously within the industrial plant. An industrial plant could be, for example, a production hall, a warehouse, a power plant, a chemical plant, a food processing plant, or an animal husbandry facility. The industrial plant may contain reflectors, especially retroreflectors, which can serve as obstacle marking/highlighting and/or navigation features and can be used by optoelectronic sensors on autonomous mobile robots (e.g. AGVs - Autonomous Guided Vehicles) for controlling, localizing and/or navigating the robots. If highly reflective (especially reflective) objects are present in the monitoring area, such as reflectors and especially retroreflectors, safety vests, metallic or reflective objects, the received light in typical optoelectronic sensor receiving lenses can be partially scattered by lens edges and/or other optical elements. This can occur particularly with optoelectronic sensors that scan an environment simultaneously and therefore not in individual measurements. The scattered light can appear as image distortions around the object, especially against a weakly reflective or distant background, leading to inaccurate distance measurements. These image distortions can unintentionally trigger a warning or protective field configured in the optoelectronic sensor, thus unnecessarily causing a safety stop of an autonomous robot. This reduces the availability of the robots for their intended use and/or can even render the optoelectronic sensor completely unusable for use in the industrial plant, as it repeatedly triggers a safety stop of the robots at the same positions in the industrial plant (i.e. near the retroreflectors). Known optoelectronic sensors attempt to manage or avoid image distortion by using receiving lenses with fewer internal reflections. However, such receiving lenses are complex, expensive, difficult to manufacture, and/or may still only partially prevent image distortion. Other known optoelectronic sensors reduce the intensity of the transmitted light. However, reducing the transmitted light usually results in a reduction in range, a reduction in the field of view, detection losses, and/or loss of accuracy. The invention is based on the objective of providing an improved optoelectronic sensor, particularly with regard to the detection of image distortions. To solve the problem, an optoelectronic sensor with the features of claim 1 is provided. The optoelectronic sensor according to the invention, in particular a time-of-flight camera or a LiDAR sensor, for detecting at least one object in a monitoring area, especially for vehicle navigation, comprises a light transmitter, a light receiver, and an evaluation unit. The light transmitter is configured to emit transmitted light into the monitoring area. The light receiver is configured to receive reflected light from the monitoring area. The evaluation unit is configured to obtain distance data over the monitoring area based on the received light, wherein the distance data includes intensity values and corresponding distance values. The evaluation unit is further designed to determine, for all those data components (e.g., image points or pixels) in the distance data that do not originate from the object, and in particular for all those data components in the distance data whose (obtained) intensity value is less than a (predetermined) first intensity threshold, a distance to the object, especially to the edge of the object, based on the distance data. Based on the determined distance of the respective data component to the object, a model for the scattered light behavior of the optoelectronic sensor, and the intensity value of the respective data component, the evaluation unit determines a probability value that the respective data component represents a disturbance. The evaluation unit is further designed to recognize as disturbances all those data components whose The determined probability value is equal to or greater than a (predetermined) probability limit. In other words, the invention is based on the understanding that for all data components in the distance data that do not originate from a (stron