CN-122017790-A - Photoelectric sensor for detecting object in monitoring area

Abstract

The invention relates to a photoelectric sensor, in particular a time-of-flight camera or LiDAR sensor, for detecting at least one object in a monitoring area, wherein the photoelectric sensor comprises a light emitter, a light receiver and an evaluation unit. The light emitter is configured to emit transmitted light to the monitoring area. The light receiver is configured to receive the received light retroreflected by the monitoring area. The evaluation unit is configured to obtain distance data about the monitored area based on the received light, wherein the distance data comprises intensity values and associated distance values, to determine, for all data parts of the distance data that do not originate from the object, in particular data parts of which the intensity values are smaller than a first intensity limit value, in each case based on the distance data, a distance to the object, in particular a distance to an edge of the object, and to determine, in each case based on the determined distances of the respective data parts from the object, based on a scattered light behavior model of the photoelectric sensor, and based on the intensity values of the respective data parts, a probability value that the respective data parts represent disturbances, and to identify all data parts of which the determined probability value is equal to or larger than the probability limit value as disturbances.

Inventors

• Michael. Kingston

Assignees

• 西克股份公司

Dates

Publication Date

20260512

Application Date

20251107

Priority Date

20241108

Claims (20)

1. 1. A photoelectric sensor for detecting at least one object in a monitored area, Wherein the photoelectric sensor comprises a light emitter, a light receiver and an evaluation unit; Wherein the light emitter is configured to emit transmitted light to the monitoring region, Wherein the light receiver is configured to receive the received light retroreflected by the monitoring area, and Wherein the evaluation unit is configured to: Obtaining distance data about the monitored area based on the received light, wherein the distance data comprises an intensity value and an associated distance value; For all data parts of the distance data that do not originate from the object, In each case, determining a distance to the object based on the distance data, and In each case, determining a probability value for the respective data portion representing a disturbance based on the determined distance of the respective data portion from the object, based on a model of scattered light behavior of the photosensor, and based on the intensity values of the respective data portion, and All data portions for which the determined probability value is equal to or greater than the probability limit value are identified as interference.
2. 2. The photoelectric sensor of claim 1, wherein the photoelectric sensor is one of a time-of-flight camera and a lidar sensor.
3. 3. The photoelectric sensor of claim 1, wherein the evaluation unit is further configured to determine, for all data portions having intensity values smaller than a first intensity limit value, a probability value that the respective data portion represents the disturbance.
4. 4. The photoelectric sensor according to claim 1, wherein the evaluation unit is configured to determine a distance to an edge of the object based in each case on the distance data.
5. 5. The photoelectric sensor according to claim 1, wherein the evaluation unit is configured to determine a distance, a size, an intensity, and/or a retroreflectivity of a retroreflective object based on the distance data.
6. 6. The photoelectric sensor of claim 5, wherein the probability value that the respective data portion represents a disturbance is determined as a function of the determined distance of the respective data portion from the object, an intensity value of the respective data portion, a maximum measurable intensity, and a size of the object.
7. 7. The photoelectric sensor according to claim 5, wherein the evaluation unit is configured to determine the size of the retroreflective object based on a data portion of the distance data in which an intensity value is equal to or greater than a first intensity limit value.
8. 8. The photoelectric sensor according to claim 5, wherein the evaluation unit is configured to identify the data portion representing the disturbance in the distance data only in a case where the size of the determined object is equal to or larger than a predetermined size limit value, the retroreflectivity of the determined object is equal to or larger than a predetermined second intensity limit value, and/or the intensity of the determined object is equal to or larger than a predetermined second intensity limit value.
9. 9. The photoelectric sensor according to claim 5, Wherein the distance data comprises a plurality of pixels, each pixel having an intensity value and an associated distance value, and Wherein the evaluation unit is configured to: determining a size of the object based on pixels in the distance data having an intensity value equal to or greater than a first intensity limit, For each pixel having an intensity value less than the first intensity limit, Determining the distance of the nearest pixel to the object, and Determining a probability value for the corresponding pixel representing a disturbance based on the intensity value of the corresponding pixel, the determined distance of the corresponding pixel from the nearest pixel of the object, the maximum measurable intensity and/or the intensity of the object and the size of the object, and All pixels having probability values equal to or greater than the probability limit value are identified as interference.
10. 10. The photoelectric sensor according to claim 9, Wherein the size of the object is determined by the number of pixels.
11. 11. The photosensor according to claim 10, wherein a distance to the object is determined as a number of pixels.
12. 12. The photoelectric sensor of claim 1, wherein the evaluation unit is configured to: determining a distance of the retroreflective object based on the distance data, and All data portions having probability values equal to or greater than the probability limit value and associated distance values within a tolerance range around the determined distance of the object are identified as interference.
13. 13. The photosensor according to claim 12, Wherein the distance data comprises a plurality of pixels, each pixel having an intensity value and an associated distance value, an Wherein the evaluation unit is configured to: Each pixel in the distance data having an intensity value equal to or greater than a first intensity limit is input into a distance histogram, Peaks in the distance histogram are identified, Determining a size of the object based on the number of pixels below the peak, and A distance of the object is determined based on the location of the peak in the distance histogram.
14. 14. The photosensor according to claim 13, Wherein the peak is the largest peak in the distance histogram.
15. 15. The photoelectric sensor of claim 1, wherein the portion of the distance data identified as being noisy is removed from the distance data, marked as invalid and/or ignored in further evaluating the distance data.
16. 16. A photoelectric sensor according to claim 15, wherein the portion of the distance data identified as disturbance is used to control movement of the robot.
17. 17. The photosensor of claim 1, wherein the object includes a reflector.
18. 18. The photosensor of claim 17, wherein the reflector is a retro-reflector.
19. 19. A system comprising at least one photoelectric sensor and at least one autonomous robot, wherein the photoelectric sensor comprises a light emitter, a light receiver and an evaluation unit, Wherein the light emitter is configured to emit transmitted light to a monitoring area, Wherein the light receiver is configured to receive the received light retroreflected by the monitoring area, and Wherein the evaluation unit is configured to: Obtaining distance data about the monitored area based on the received light, wherein the distance data comprises an intensity value and an associated distance value; For all data parts of the distance data that do not originate from the object, In each case, determining a distance to the object based on the distance data, and In each case, determining probability values for the respective data portions representing disturbances based on the determined distances of the respective data portions from the object, based on a model of scattered light behavior of the photosensor, and based on intensity values of the respective data portions, and All data portions having probability values equal to or greater than the probability limit value are identified as interference.
20. 20. The system of claim 19, wherein the photoelectric sensor is attached to and movable with the autonomous robot.

Description

Photoelectric sensor for detecting object in monitoring area Technical Field The invention relates to a photoelectric sensor, in particular a time-of-flight camera or a lidar sensor, for detecting at least one object within a monitoring area, wherein the photoelectric sensor comprises means for recognizing that a data portion of acquired distance data about the monitoring area is a disturbance. Background The photoelectric sensor can be used for industrial safety application, and can realize safety environment perception of a monitoring area, and particularly safety three-dimensional environment perception of the monitoring area, so that safety and efficiency of industrial processes in an industrial factory building can be improved. Examples of such photosensors are ToF (Time-of-Flight) cameras and LiDAR (laser radar) sensors. For example, the photoelectric sensor may be attached in a fixed manner within the industrial plant, or may be attached to a robot that can autonomously move within the industrial plant. For example, the industrial plant may be a production plant, warehouse, power plant, chemical plant, food plant, or livestock facility. Reflectors, particularly retro-reflectors, may be attached in industrial plants and can be used as obstacle marking/obstacle highlighting and/or navigation functions and for use with photosensors on autonomous mobile robots (e.g., agvs—autonomous guided vehicles) to control, position and/or navigate the robots. If there is a high retroreflectivity (particularly reflective) object, such as a reflector (particularly a retro-reflector), an alarm vest, a metal or reflective object, within the monitored area, the received light in typical receiving optics of the photosensor may be partially scattered at the lens edges and/or other optical elements. This occurs particularly on photosensors where the environment is scanned simultaneously rather than being measured separately. Scattered light can appear as image disturbances around objects (especially in front of very weak or remote retroreflective backgrounds) and can cause distortion of distance measurements. Image disturbances may trigger an alarm field or a protection field configured in the photosensor in an undesired manner and thus cause an unnecessary safety stop of the autonomous robot. This reduces the availability of the robot in its intended use and/or may even render the photosensors completely unusable in the industrial plant, as they repeatedly trigger a safe stopping of the robot at the same location in the industrial plant, i.e. near the reflector. Known photosensors attempt to overcome or avoid the occurrence of image disturbances by using receiving lenses with less internal reflection. However, such receiving lenses are complex, expensive, difficult to implement, and/or, if possible, can only prevent the occurrence of image interference to some extent. Other known photosensors may reduce the intensity of the transmitted light. However, the reduction of transmitted light typically results in reduced distance, reduced field angle, detection loss, and/or loss of accuracy. Disclosure of Invention The present invention is based on the object of providing an improved photosensor, in particular with respect to identifying image disturbances. There is provided a photosensor having the features of claim 1 to meet this object. The photoelectric sensor according to the invention, in particular a time-of-flight camera or a lidar sensor, for detecting at least one object within a monitoring area, in particular for vehicle navigation, comprises a light emitter, a light receiver and an evaluation unit. The light emitter is configured to emit transmitted light to the monitoring region. The light receiver is configured to receive the received light retroreflected by the monitoring area. The evaluation unit is configured to obtain distance data about the monitored area based on the received light, wherein the distance data comprises an intensity value and an associated distance value. The evaluation unit is further configured to determine, for all data parts (e.g. pixels) of the distance data that do not originate from the object, in particular for all data parts of the distance data that have intensity values smaller than a (predetermined) first intensity limit value, in each case based on the distance data, a distance to the object, in particular a distance to an edge of the object, and to determine, in each case based on the determined distance of the respective data part to the object, based on a scattered light behavior model of the photoelectric sensor, and based on the intensity values of the respective data part, a probability value that the respective data part represents the disturbance. The evaluation unit is further configured to identify all data parts having the determined probability value equal to or larger than the (predetermined) probability limit value as disturbances. In other words, the invention is base