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DE-102024132664-A1 - Optoelectronic sensor for detecting objects in a monitored area

DE102024132664A1DE 102024132664 A1DE102024132664 A1DE 102024132664A1DE-102024132664-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 transmitted light into the monitoring area. The light receiver is configured to receive reflected light from the monitoring area, and in particular from the object in the monitoring area. The evaluation unit is configured to acquire distance data about the monitoring area, and in particular about the emitting object in the monitoring area, based on the reflected light. The distance data comprises intensity values and corresponding distance values. The evaluation unit uses the distance data to determine the distance of the object and to identify as interference those data components in the distance data where an intensity value is less than a predetermined first intensity limit and the corresponding distance value lies within a tolerance range around the determined distance of the object.

Inventors

  • Wolfram Strepp
  • Joerg Sigmund
  • Govinda Kempermann

Assignees

  • SICK AG

Dates

Publication Date
20260513
Application Date
20241108

Claims (13)

  1. Optoelectronic sensor (100), in particular a time-of-flight camera or a LiDAR sensor, for detecting at least one object (40) in a monitoring area, whereby the optoelectronic sensor (100) comprises a light transmitter (10), a light receiver (20), and an evaluation unit (30), whereby the light transmitter (10) is configured to emit transmitted light (11) into the monitoring area, whereby the light receiver (20) is configured to receive reflected light (12) from the monitoring area, and in particular from the object (40) in the monitoring area, and wherein the evaluation unit (30) is configured to obtain distance data about the monitoring area, and in particular about the reflecting object (40) in the monitoring area, based on the reflected light (12), whereby the distance data comprise intensity values and associated distance values, and, based on the distance data, determine the distance of the object (40) to determine, and to identify as disturbances those data components (21) in the distance data where an intensity value is less than a predetermined first intensity limit (31) and the associated distance value is within a tolerance range (34) around the determined distance of the object (40).
  2. Optoelectronic sensor (100) according to Claim 1 , where the object (40) is a reflector.
  3. Optoelectronic sensor (100) according to Claim 1 or 2 , wherein the evaluation unit (30) is configured to determine a size and/or intensity of the remitting object (40) based on the distance data, and to determine the distance of the object (40) and/or to perform the detection of those data components (21) in the distance data that represent a disturbance if the size of the object (40) is equal to or greater than a predetermined size limit and/or if the intensity of the object (40) is equal to or greater than a predetermined second intensity limit.
  4. Optoelectronic sensor (100) according to Claim 3 , 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 enter each pixel in the distance data whose intensity value is equal to or greater than the second intensity limit value into a distance histogram, to detect 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.
  5. Optoelectronic sensor (100) according to one of the preceding claims, wherein the evaluation unit is configured to compare the distance of the object (40) with a predetermined distance limit value (32), and to perform the detection of those data components (21) that represent a disturbance only if the distance is equal to or less than the distance limit value (32).
  6. Optoelectronic sensor (100) according to one of the preceding claims, whereby the first intensity limit (31) is determined as a function of the distance of the object (40), and/or whereby the first intensity limit (31) is determined based on an intensity of an object to be detected or detectable with the lowest remission, whereby the first intensity limit (31) is preferably limited by a predetermined maximum value (33).
  7. Optoelectronic sensor (100) according to one of the preceding claims, wherein the first intensity limit (31) is determined as a function of a minimum intensity limit at a predetermined distance limit (32), the distance limit (32), and the distance of the object (40), wherein the minimum intensity limit at the predetermined distance limit (32) preferably corresponds to a remission of 2%.
  8. Optoelectronic sensor (100) according to one of the preceding claims, wherein the evaluation unit (30) is configured to detect as disturbance those data components in the distance data where the intensity value is less than a predetermined third intensity limit (35), and preferably those data components in the distance data where the intensity value is less than the predetermined third intensity limit (35) and the the associated distance value lies outside the tolerance range (34) around the determined distance of the object (40), wherein the third intensity limit value is preferably set to a fixed value.
  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. Use of an optoelectronic sensor (100) according to one of the preceding claims for detecting at least one object (40) in a monitoring area.
  11. A method for detecting at least one object (40) in a monitoring area, wherein transmitted light (11) is emitted into the monitoring area; wherein reflected received light (12) is received from the monitoring area, and in particular from the object (40) in the monitoring area, wherein the object (40) is preferably a reflector; wherein distance data about the monitoring area, and in particular about the emitting object (40) in the monitoring area, are obtained based on the received light (12), and are in particular measured by means of a time-of-flight method, wherein the distance data comprise intensity values and associated distance values; wherein a distance of the object (40) is determined on the basis of the distance data; and wherein those data components (21) in the distance data are recognized as disturbances where an intensity value is less than a predetermined first intensity limit (31) and the associated distance value lies within a tolerance range (34) around the determined distance of the object.
  12. Procedure according to Claim 11 , furthermore, based on the distance data, a size and/or intensity of the remitting object (40) is determined, and the distance of the object (40) is determined if the size of the object (40) is equal to or greater than a predetermined size limit and/or if the intensity of the object (40) is equal to or greater than a predetermined second intensity limit.
  13. Procedure according to Claim 11 or 12 , wherein the first intensity limit (31) is determined as a function of the distance of the object (40), and/or wherein the first intensity limit (31) is determined based on an intensity of an object to be detected or detectable with the lowest remission, wherein the first intensity limit (31) is preferably limited by a predetermined maximum value (33).

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 plant. Reflectors can be installed within the plant, which are used by the optoelectronic sensors on the autonomous robots for robot control, localization, and/or navigation. In typical receiving lenses of optoelectronic sensors, multiple reflections from very bright objects in the monitored area, such as reflectors, safety vests, metallic or reflective objects, often lead to ghosting and/or double images, and in particular to so-called ghost objects. The received light from a highly reflecting (i.e., bright) object can be partially scattered within the lens of the optoelectronic sensor by lens edges and/or other optical elements, creating a halo around the object. This scattered light can appear as a ghost object, especially against a less highly reflecting (i.e., dark) background. This ghost object typically appears at the same distance as the bright object, since it is the same received light (except for a small additional path length due to scattering within the lens). Such ghost objects can unintentionally trigger a warning or protection 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 (near the reflectors). Known optoelectronic sensors attempt to mitigate or prevent ghosting and/or double images by using receiving lenses with fewer internal reflections. However, such receiving lenses are complex, expensive, difficult to manufacture, and/or may still only offer limited protection against so-called "toxic" reflector behavior. Other known optoelectronic sensors reduce the intensity of the transmitted light. However, reducing the transmitted light usually results in a reduction in range, a narrower field of view, detection losses, and/or a decrease in accuracy. The invention is based on the objective of providing an improved optoelectronic sensor, particularly with regard to avoiding ghosting and/or double images. 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, 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, and in particular from the object in the monitoring area. The evaluation unit is configured to acquire distance data about the monitoring area, and in particular about the emitting object in the monitoring area, based on the received light (in particular by measuring it using a time-of-flight method), wherein the distance data includes intensity values and associated distance values, to determine the distance of the object based on the distance data, and to recognize those data components (e.g., image points or pixels) in the distance data as disturbances where an intensity value is less than a predetermined first intensity limit and the associated distance value lies within a tolerance range around the determined distance of the object. In other words, the invention is based on the finding that a ghost object usually appears at approximately the same distance from the optoelectronic sensor as the (real) reflecting object. The intensity of the so-called ghost object is often rather low, and In particular, the intensity is usually lower than that of other detectable objects in the monitored area (determined by the technical specifications of the optoelectronic sensor). Based on this, those data components that represent interference or a ghost object can be identified and filtered out. The optoelectronic sensor is preferably a safe sensor, i.e., a safety sensor, and in particular a safety ToF camera or a safety LiDAR sensor. Th