OPTOELECTRONIC SENSOR

Description

[0001] The invention relates to a sensor for detecting objects in a surveillance area according to the preamble of claim 1.

[0002] Optoelectronic systems, and especially laser scanners, are suitable for distance measurements that require a large horizontal angular range of the measuring system. In a laser scanner, a light beam generated by a laser periodically sweeps across a monitored area with the aid of a deflection unit. The light is remitted by objects in the monitored area and evaluated in the scanner. The angular position of the deflection unit is used to determine the angular position of the object, and the distance of the object from the laser scanner is determined from the light travel time, using the speed of light.

[0003] The angle and distance information records the location of an object in the surveillance area in two-dimensional polar coordinates. This allows the positions of objects to be determined or, by scanning the same object multiple times at different locations, its contour to be determined. The third spatial coordinate can also be recorded by a relative movement in the transverse direction, for example, by adding another degree of freedom to the deflection unit in the laser scanner or by moving the object relative to the laser scanner. This also allows three-dimensional contours to be measured.

[0004] In addition to such measurement applications, laser scanners are also used in safety technology to monitor a hazard source, such as a dangerous machine. Such a safety laser scanner is known from DE 43 40 756 A1. It monitors a protective field that operating personnel are prohibited from entering while the machine is in operation. If the laser scanner detects an unauthorized intrusion into the protective field, such as an operator's leg, it triggers an emergency stop of the machine. Sensors used in safety technology must be particularly reliable and therefore meet stringent safety requirements, such as the EN13849 standard for machinery safety and the EN61496 device standard for electro-sensitive protective devices (ESPE).

[0005] Scanning the monitoring plane in a laser scanner is typically achieved by directing the transmitted beam onto a rotating deflecting mirror. The light transmitter, light receiver, and associated electronics and optics are permanently mounted in the device and do not rotate. However, it is also known to replace the deflecting mirror with a moving scanning unit. For example, in DE 197 57 849 B4, the entire measuring head, including the light transmitter and light receiver, rotates. EP 2 388 619 A1 also provides a rotating transmit / receive unit. This scanning unit is supplied with energy, for example, by the non-rotating areas of the sensor, using the transformation principle.

[0006] Figure 1shows a schematic sectional view of a conventional laser scanner 100 with such a rotatable scanning unit 102. The rotary movement is generated by the scanning unit 102 being mounted on a shaft 104 of a drive 106. The laser scanner 100 is protected by a housing 108, which is formed in the upper part by a hood 110.

[0007] Due to the multitude of components (housing, cover, drive, scanning unit) and interfaces between the components, assembly and adjustment work is significant, especially when the sensor requires excellent scanning field flatness. For moving scanning units, an additional interface for power and data transmission must be provided on the rotating part of the sensor. This requires additional components or assemblies, which increase the complexity of the sensor as well as its assembly and adjustment.

[0008] From DE 10 2010 060 876 A1, an automatically movable floor dust collector is known, wherein the device is provided with an obstacle detection system consisting of optical transmitter and receiver units and wherein an element for beam deflection is provided, wherein furthermore, for all-round detection, at least a part of the transmitter and receiver unit is rotatable by 180° or more and is preferably arranged on a drivable rotating part.

[0009] US 2010 0 245 801 A1 describes an optical sensor based on the time-of-flight principle, which enables a scanning range of 360°, with a light source, a detector and a concave mirror being arranged on a common rotating device.

[0010] DE 102016 117 093 B3 describes an optoelectronic sensor, in particular a laser scanner, for detecting objects in a monitoring area, wherein the sensor has a housing with a hood which is additionally supported by a support element.

[0011] Therefore, the object of the invention is to provide a generic sensor with a simplified structure.

[0012] This object is achieved by an optoelectronic sensor for detecting objects in a monitoring area according to claim 1 and a method for supporting a scanning unit which is part of an optoelectronic sensor according to claim 1.

[0013] The sensor has a light transmitter and a light receiver for scanning the monitored area, with a drive having a stator and a rotor and a scanning unit moved by the rotor ensuring a periodic scanning movement. The sensor has a base housing with a cover, the base housing and the cover having at least one interface for mechanically connecting them. The cover comprises at least one first bearing for accommodating the scanning unit, with the scanning unit and the rotor being rotatably mounted in the first bearing. The first bearing is arranged on the side of the cover facing the base housing.

[0014] The invention has the advantage that by mounting the scanning unit in the cover, the number of interfaces subject to tolerances is reduced, which leads to simplified assembly and / or adjustment and thus lower manufacturing costs. Furthermore, mounting the scanning unit in the cover results in an optimal bearing arrangement (center of gravity between the bearing points), which leads to a significant improvement in vibration and / or shock requirements. At the same time, the entire sensor becomes more robust in the field, has greater shock and vibration resistance, and thus significantly increases its suitability for outdoor use or its possible applications in demanding environments where the sensor cannot be protected from mechanical stress. Failure due to a defective device becomes significantly less likely.

[0015] In one embodiment of the invention, the light transmitter and light receiver can be arranged in the base housing. The scanning unit then has a deflecting mirror for deflecting the transmitted light into the monitored area and the light reflected by objects in the monitored area onto the light receiver. Along with the light transmitter and light receiver, the associated transmitting and receiving optics, as well as at least part of the transmitting and receiving electronics and possibly the evaluation unit, are preferably also housed in the base housing. This embodiment has the advantage that the moving mass of the system is kept low, since only the deflecting mirror moves with the drive rotor.

[0016] In one embodiment of the invention, the scanning unit can comprise the light transmitter and / or the light receiver. This transforms the scanning unit into a rotating measuring head. Along with the light transmitter and light receiver, the associated transmitting and receiving optics, as well as at least part of the transmitting and receiving electronics and possibly the evaluation unit, are preferably also housed in the scanning unit.

[0017] The drive stator can be located in the base housing or in the cover. If the stator and rotor are located in the cover, tolerances for the mechanical interface between the cover and the base housing, which relate to the alignment of the rotor and stator, are eliminated. The arrangement in the base housing can be advantageous if the scanning unit is designed as a deflection mirror and the other sensor components are located in the base housing, as this eliminates the need for an electrical connection to the cover.

[0018] The cover can have a second bearing for rotatably supporting the scanning unit, with the first bearing located on the side of the cover facing the base housing and the second bearing located on the side of the cover facing away from the base housing. This can improve the sensor's increased shock and vibration resistance. The dimensions of the bearings can optionally be adapted to the shape of the cover. For example, the second bearing can have a smaller diameter than the first bearing.

[0019] The hood can have mechanical mounts for the first and / or second bearings, which are advantageously an integral part of the hood. This virtually eliminates any tolerance between the hood and the scanning unit. The mounts for the first and / or second bearings can be fixed in the hood, for example, during an injection molding process for manufacturing the hood.

[0020] The hood is designed as a rotating body with a side wall and a lid. The side wall can form, for example, a circular cylinder, a truncated cone, or a sphere, but more complex contours, such as a chalice, are also conceivable. At the top, this is then closed off by a lid, which can be circular or curved.

[0021] The hood features a front panel that serves as the exit area for the transmitted light and the entrance area for the remitted light. This front panel is an integral part of the hood's side panel.

[0022] The hood is preferably made of plastic that is transparent to the transmitted light. This transparency naturally also applies to the reflected received light, since it has the same wavelength. This gives the hood the properties to also serve as a front sheath. However, the hood does not have to be transparent to the naked eye; it can be black and opaque, for example, since a spectral range outside the visible range is often used for the transmitted light, particularly infrared light.

[0023] The hood is preferably a single component, not an assembly of multiple elements, to simplify the manufacture of the hood and its handling during sensor assembly.

[0024] A support element can be provided that centrally supports the hood. The support area on the hood is located, in particular, approximately in the center of the lid area. Suitable support elements and arrangements are described, for example, in EP 3 293 546 B1.

[0025] The sensor is preferably a distance-measuring sensor, in which the evaluation unit determines the light propagation time between the emission of the light signal and the reception of the remitted light, thereby determining the distance to an object. This allows significantly more precise object information to be obtained than by simply detecting the presence of objects.

[0026] Preferably, an angle measuring unit is provided to detect the angular position of the scanning unit. Complete two-dimensional position coordinates are then available for detected objects. In the case of a spatially extended monitoring area due to movement of the scanning unit in two axes, the respective tilt angle of the scanning unit is preferably also detected, so that three-dimensional spherical coordinates are obtained, which also completely describe the object position within the monitoring area.

[0027] The sensor is preferably designed as a safety sensor and has a safety output. The evaluation unit is configured to determine whether an object is located in a protective field within the monitoring area and then output a safety-related shutdown signal via the safety output. A safety sensor is safe in the sense of a safety standard, as described in the introduction, and can therefore be used, in particular, to protect people at sources of danger.

[0028] The invention will be explained in more detail below with regard to further features and advantages, using exemplary embodiments and with reference to the accompanying drawings. Like reference numerals denote like or analogous features. The figures of the drawing show: Fig. 1 is a schematic sectional view of a conventional laser scanner; Fig. 2 is a schematic sectional view of an embodiment of a laser scanner according to the invention with a scanning unit designed as a deflection mirror; Fig. 3 is a schematic sectional view of an embodiment of a laser scanner according to the invention similar to Figure 2 ; Fig. 4 a schematic sectional view of another embodiment of a laser scanner according to the invention similar Figure 2 ; Fig. 5 a schematic sectional view of an embodiment of a laser scanner according to the invention with a scanning unit comprising a light transmitter and light receiver; Fig. 6 a schematic sectional view of another embodiment of a laser scanner according to the invention similar Figure 6 ;

[0029] Fig. 2shows a schematic sectional view through an optoelectronic sensor according to the invention in one embodiment as a laser scanner 10. The laser scanner 10 roughly comprises a movable scanning unit 12, a base housing 14, and a hood 16. The base housing 14 and the hood 16 are mechanically connected to one another via at least one interface 18. The hood 16 has a side wall 50, here in the shape of a cylinder, generally as a body of revolution with a suitable contour. The side wall 50 serves as a front pane through which transmitted light 30 emerges, or light 36 remitted from the monitored area 32 enters. Accordingly, it is made of a material that is transparent to the transmitted light 30 generated by a light transmitter 26. The hood 16 is closed at the top by a cover region 52, which is connected to the side wall 50 and is preferably formed jointly therewith.For example, the hood 16 is a single plastic component that can be manufactured using an injection molding process.

[0030] The hood 16 comprises at least one first bearing 20 for accommodating the scanning unit 12. The first bearing 20 is arranged on the side of the hood 16 facing the base housing 14, and the scanning unit 12 is rotatably mounted in the first bearing 20. The scanning unit 12 further comprises at least one rotor 22, by which the scanning unit can be set into an oscillating or rotary motion in conjunction with at least one stator 24 arranged in the base housing 14. The rotor 22 and stator 24 thus jointly form a drive for the scanning unit 12.

[0031] In this embodiment, the scanning unit 12 has a deflecting mirror 25; further components of the laser scanner 10 are arranged in the base housing 14. A light transmitter 26 generates transmitted light 30 with the aid of transmitting optics 28, which is emitted via the deflecting mirror 25 of the scanning unit 12 into a monitoring area 32. If the transmitted light 30 strikes an object 34 in the monitoring area 32, a correspondingly remitted light 36 returns to the laser scanner 10. The remitted light 36 is guided via the deflecting mirror 25 of the scanning unit 12 to receiving optics 38 in the base housing 14, where it is focused onto a light receiver 40, where it is converted into an electrical received signal. The light transmitter 26 and the light receiver 34 are housed together on a circuit board 42.

[0032] A control and evaluation unit 44 controls the stator 24 of the scanning unit drive and the light transmitter 26, evaluates the received signal from the light receiver 40, and receives the signal from an angle measuring unit 46, which determines the respective angular position of the scanning unit 12. The control and evaluation functionality can be distributed largely freely between the circuit board 42 and the evaluation unit 44, but is described as if the evaluation unit 44 were solely responsible for it.

[0033] For evaluation, the distance to the scanned object 34 is preferably measured using a time-of-flight method. For this purpose, the transmitted light of the light transmitter 26 is modulated in a phase-based system, and a phase relationship to the received signal of the light receiver 40 is evaluated. Alternatively, in a pulse-based system, short light pulses are emitted at a transmission time, and their reception time is determined from the received signal. Both single-pulse methods, which determine a distance from a single transmitted pulse, and pulse-averaging methods are conceivable, in which the received signal is collected and statistically evaluated after a plurality of consecutive transmitted pulses. The respective angular position at which the transmitted light 30 was emitted is also known by the angle measuring unit 46.Thus, after each scan period, i.e. rotation of the scanning unit 12, two-dimensional polar coordinates of all object points in a scanning plane are available via the angle and the distance.

[0034] The object positions or contours are thus known and can be output via a sensor interface 48. Conversely, the sensor interface 44 or another connection (not shown) serves as a parameterization interface. In safety technology applications, protective fields that can be configured in the monitoring area 22 are monitored for unauthorized interventions, and if necessary, a safety-related shutdown signal is output via the then safely configured interface 48 (e.g., OSSD, Output Signal Switching Device).

[0035] Figure 3 shows a modification of the embodiment of the laser scanner 10 from Figure 2The hood 16 has a second bearing 54 for rotatably supporting the scanning unit 12 with a stabilizing element 56. The second bearing 54 is arranged on the side of the hood 16 facing away from the base housing 14. The second bearing 54 has a smaller diameter than the first bearing 20.

[0036] Figure 4 shows a further modification of the embodiment of the laser scanner 10 from Figure 2 , whereby in contrast to the embodiment of Figure 2 The cover 16 encompasses both the rotor 22 and the stator 24 of the drive of the scanning unit 12. This eliminates tolerances for the mechanical interface 18 between the cover 16 and the base housing 14, which relate to the alignment of the rotor 22 and the stator 24 relative to each other.

[0037] Figure 5 shows an alternative embodiment of a sensor according to the invention. As in the Figure 2-5In the embodiments shown, the optoelectronic sensor designed as a laser scanner 60 comprises, in rough division, a movable scanning unit 62, a base housing 14, and a hood 16. The base housing 14 and the hood 16 are mechanically connected to one another via at least one interface 18. The hood 16 has a side wall 50, here in the form of a cylinder, generally as a body of revolution with a suitable contour. The side wall 50 serves as a front pane through which transmitted light 30 exits or through which light 36 remitted from the monitored area enters. Accordingly, it is made of a material that is transparent to the transmitted light 30 generated by a light transmitter 26. The hood 16 is closed at the top by a cover region 52, which is connected to the side wall 50 and is preferably formed jointly therewith.For example, the hood 16 is a single plastic component that can be manufactured using an injection molding process. The hood 16 comprises at least one first bearing 20 for receiving the scanning unit 62, wherein the first bearing 20 is arranged on the side of the hood 16 facing the base housing 14, and the scanning unit 12 is rotatably mounted in the first bearing 20. The scanning unit 62 further comprises at least one rotor 22, by which the scanning unit 62, in conjunction with at least one stator 24 arranged in the base housing 14, can be set into an oscillating or rotating motion in order to periodically scan a monitoring area 32. The rotor 22 and stator 24 thus jointly form a drive for the scanning unit 62.

[0038] In contrast to the Figure 2-5In the embodiments shown, the scanning unit 62 is designed as an optical measuring head in which a light transmitter 26 emits transmitted light 30 into the monitoring area 32 with the aid of a transmitting optics 28. If the transmitted light 30 strikes an object 34 in the monitoring area 32, the corresponding remitted light 36 returns to the laser scanner 60. The remitted light 36 is guided by a receiving optics 38 to a light receiver 40, where it is converted into an electrical received signal. The light transmitter 26 and the light receiver 40 are housed together on a first circuit board 42. The scanning unit 62 further comprises a first energy transmission module 64 and a first data transmission module 66.

[0039] The arrangement in the scanning unit 62 is purely exemplary. Thus, the light transmitter 26 and light receiver 40 can each be housed on their own circuit board, and more or fewer circuit boards can be provided in a different arrangement. In principle, any other arrangement known per se from single-beam optoelectronic sensors or laser scanners is possible, such as a double lens with transmitting optics in the center of a receiving lens or the use of a beam splitter mirror. It is not even absolutely necessary to construct a scanning system comprising the light transmitter 26 and light receiver 40; instead, another sensor or a combination of several sensors can rotate, for example to achieve multiple scanning in multiple planes, as described, for example, in DE 10 2013 111 547 A1.

[0040] The base housing 14 of the laser scanner 62 comprises, in addition to the stator 24, a control and evaluation unit 44 and a sensor interface 48, as well as a second energy transmission module 68 and a second data transmission module 70. The scanning unit 62, in particular the light transmitter 26 and the light receiver 40, can be supplied with energy via the first and second energy transmission modules 64, 68. The first and second data transmission modules serve for the wireless, bidirectional data transmission of control signals from the control and evaluation unit 44 to the scanning unit 62 and of electrical received signals from the light receiver 40 to the control and evaluation unit 44. The control and evaluation unit 44 evaluates the received signal, controls the drive 16, and receives the signal from an angle measuring unit 42, which determines the respective angular position of the scanning unit 62.The control and evaluation functionality can be distributed largely freely between the scanning unit 62, in particular the circuit board 42, and the evaluation unit 40. The evaluation of the received signals is carried out analogously to the description in . Figure 2 .

[0041] Figure 6 shows a modification of the embodiment of the laser scanner 60 from Figure 5The hood 16 is supported in the cover region 52, centrally in this embodiment, by a support element 72. The support element 72 can have a simple shape, such as a pin or rod. The connection between the hood 16 and the support element 72 is preferably fixed. A rotatable bearing is not provided and is also not necessary because the support element 72 does not follow the movement of the scanning unit 62. Rather, the support element 72 extends through a recess in the scanning unit 62 to the base housing 14. The hood 16 is thus stably connected to the base housing at the interfaces 18 and additionally in the cover region 52.

Claims

1. Optoelectronic sensor (10, 60), in particular a laser scanner, for detecting objects (34) in a monitoring area (32), the sensor (10, 60) comprising a light transmitter (26) for emitting transmitted light (30), a drive with a stator (24) and a rotor (22), a scanning unit (12, 62) movable with the aid of the rotor (22) for periodically scanning the monitoring area (32) with the transmitted light (30), a light receiver (40) for generating a received signal from light (30) remitted by objects (34) in the monitoring area (32), a control and evaluation unit (44) for detecting information about objects (34) in the monitoring area (32) using the received signal, and a base housing (14) with a hood (16), the base housing (14) and the hood (16) having at least one interface (18) for mechanical connection to one another, and the hood (16) being designed as a body of revolution with a side wall (50) and a cover region (52) and having a front screen (50) as an exit region for the transmitted light (30) and entry region for the remitted light (36), the front screen (50) being an integral component of the side wall (50) of the hood (16), wherein the hood (16) comprises at least one first bearing (20) arranged on the side of the hood (16) facing the base housing (14) for receiving the scanning unit (12, 62), wherein the scanning unit (12, 62) is rotatably mounted with the rotor (22) in the first bearing (20) and the side wall (50) of the hood (16) comprises the first bearing (20).

2. Optoelectronic sensor (10, 60) according to claim 1, characterized in that the stator (24) is arranged in the base housing (14).

3. Optoelectronic sensor (10, 60) according to claim 1, characterized in that the stator (24) is arranged in the hood (16).

4. Optoelectronic sensor (10, 60) according to one of the preceding claims, characterized in that the hood (16) has a second bearing (54) for rotatably mounting the scanning unit (12, 62), the second bearing (54) being arranged on the side of the hood (16) facing away from the base housing (14).

5. Optoelectronic sensor (10, 60) according to one of the preceding claims, characterized in that the hood (16) is made of plastic that is transparent to the transmitted light (30).

6. Optoelectronic sensor (10) according to one of the preceding claims, characterized in that the light transmitter (26) and the light receiver (40) are arranged in the base housing (14), and the scanning unit (12) has a deflecting mirror (25) for deflecting the transmitted light (30) into the monitoring area (32) and the light (36) remitted from objects (34) in the monitoring area (32) onto the light receiver (40).

7. Optoelectronic sensor (60) according to one of claims 1 - 5, characterized in that the sensing unit (62) comprises the light transmitter (26) and / or the light receiver (40).

8. Optoelectronic sensor (60) according to claim 7, characterized in that the sensor (60) has a support element (72) for centrally supporting the hood (16).