Optical measuring device and method for the three-dimensional optical measurement of objects with a sensor unit for detecting other objects in the corresponding sensor range

Abstract

An optical measuring device (4) for the three-dimensional optical measurement of objects, wherein the optical measuring device (4) has a device housing (5) in which a projection unit (6) for projecting a measuring structure onto the surface of the object to be measured in a projection area (P) and a camera unit (8a, 8b) for capturing images of the object provided with the projected measuring structure are integrated. The device housing (5) also has a sensor unit (9) for detecting persons in a sensor range (11) covered by the sensor unit (9). The optical measuring device (4) is designed to limit the light intensity to a level that is not dangerous for a person located in a danger area (3) of the projection area (P) when the presence of a person in the sensor area (11) or part of the sensor area (11) has been detected.

Description

[0001] OPTICAL MEASURING DEVICE AND METHOD FOR THREE-DIMENSIONAL OPTICAL MEASURING OF OBJECTS WITH A SENSOR UNIT FOR DETECTING OTHER OBJECTS IN THE CORRESPONDING SENSOR AREA

[0002] The invention relates to an optical measuring device for the three-dimensional optical measurement of objects, wherein the optical measuring device has a device housing into which a projection unit for projecting a measuring structure onto the surface of the object to be measured in a projection area and a camera unit for recording images of the object provided with the projected measuring structure are integrated.

[0003] The invention further relates to a method for three-dimensional optical measurement of objects using such an optical measuring device.

[0004] The three-dimensional optical detection of object surfaces using optical sensors based on the principle of triangulation is well known. Patterns, particularly striped patterns, are projected onto the object to be measured. The backscattered pattern is recorded by one or more image acquisition units and subsequently evaluated by an image evaluation unit.

[0005] The patterns projected by the projection unit can be designed in a variety of ways. Typical projected patterns are stochastic patterns as well as regular patterns, such as dot and stripe patterns. Stripe patterns, in particular, have established themselves as common patterns in optical 3D measurement.

[0006] The projected pattern creates an artificial, temporary texture on the object being measured. This texture is captured by the camera unit, which may have one or more cameras (commonly referred to as the image acquisition unit). Based on the artificially generated, generally known a priori texture, 3D points on the object being measured can be uniquely identified in both the projection unit and the camera unit.

[0007] The 3D coordinates can be determined using a triangulation method, generally by forward slicing. This requires measuring the same object point from at least two spatially different recording positions. The projection unit can act as an inverted camera, so that measurement with one camera is sufficient to determine the 3D coordinates. In many cases, however, it can be helpful to use multiple cameras to capture the projected texture.

[0008] DE 102012 113 021 A1 discloses such a measuring device for three-dimensional optical measurement of objects using a topometric sensor, i.e., an optical measuring device within the meaning of the present invention. The sensor has a projection unit and an image recording unit, which are arranged in a fixed position relative to one another on a common device housing. The projection unit has a laser light source for projecting patterns with sufficient brightness.

[0009] Instead of a laser light source, sufficient brightness can also be ensured with other light sources, e.g. halogen lamps, short arc lamps, metal halide lamps and light-emitting diodes.

[0010] This raises the problem of the danger to people who, without protective equipment, in particular safety goggles, may come into contact with the projection beam and be injured, especially if the person looks directly into the light source.

[0011] Therefore, Class 3 optical measuring devices may only be operated in protected areas, such as in separate rooms. Such use generally requires that safety is ensured by a laser safety officer.

[0012] CN 102681312 B discloses a system for protecting the human eye for a laser projector. An ultrasonic sensor measures the time when an object is positioned between the laser projector and a screen to dim or turn off the laser projector. This reduces the light dose to a permissible level.

[0013] CN 105306856 B discloses a security device for a projector, such as a laser microprojector. The security device has a camera with a field of view encompassing the projection area. Pattern recognition determines whether an image of a face appears in the camera's field of view, in which case the light source is switched off to protect the human eye. An additional infrared sensor can be used to check whether an infrared signal in the field of view matches a thermal signature of the face detected by the camera, thus avoiding false alarms. The infrared sensor can be integrated into the camera.

[0014] JP 2014 174 194 A and JP 2014 174 195 A describe a projector with a laser light source for projecting an image onto a screen. A distance sensor detects the distance of an object from the projector's projection aperture to dim or shut down the projector if the detected distance of the object is less than a specified safe distance and the object is therefore located in a hazardous area.

[0015] US 10,837,759 B2 discloses a 3D measuring device with a sensor for detecting a person within a detection zone. The measuring device has a laser light source that projects, for example, a striped light pattern onto an object. If a person is within the sensor zone for detecting a person, the power of the laser beam is limited. The optical measuring device with the projection unit and a camera is mounted on a robot. Independently of this measuring device, the sensor for detecting the presence of a person is positioned outside of this measuring device so that it monitors the space around the robot.

[0016] Based on this, it is the object of the present invention to provide an improved optical measuring device and method for three-dimensional optical measurement of objects.

[0017] The object is achieved by the optical measuring device having the feature of claim 1 and by the method having the features of claim 12. Advantageous embodiments are described in the subclaims.

[0018] It is proposed that the device housing further comprises a sensor unit for detecting persons in a sensor area covered by the sensor unit, and that the optical measuring device is configured to limit the light output to a level that is safe for a person located in a hazard area to be secured within the projection area when the presence of a person in the sensor area or part of the sensor area has been detected.

[0019] By integrating the sensor unit, projection unit, and camera unit into a single device, the sensor area and projection area always remain associated with a hazardous area, even if the optical measuring device moves to perform the measurement task. This makes it possible to use the hazardous area as a static sensor area and partially or fully utilize the sensor area extending beyond it as a dynamic sensor area. This dynamic sensor area then moves with the hazardous area of ​​the projection area to be protected when the optical measuring device changes position.

[0020] The danger zone can be the entire projection area illuminated by the projection unit for projecting a light structure, or just a part of it that needs to be specially secured due to its light intensity.

[0021] Integration into a device housing means that the projection unit, camera unit, and sensor unit are mechanically connected together, for example, via a common support. The projection unit, camera unit, and sensor unit can be mounted in or on the device housing, which at least consists of the support.

[0022] In the context of the present invention, limiting the light output is not only to be understood as dimming the light output to a safe level that is not harmful to a person's eyes. The optical measuring device can also limit the light output by being configured to switch off the projection unit when the presence of a person in the sensor area or part thereof is detected. The illuminants of the projection unit can thus not only be dimmed to a safe level, but can even be switched off completely or partially if necessary, thus safely preventing any danger to users located in the danger area.

[0023] The sensor area is preferably larger than the hazard area to be protected. It not only encompasses the hazard area as the part of the projection area to be protected, but extends beyond it. This means that the sensor not only detects whether a person is located in the potentially dangerous hazard area. Rather, it can also detect whether a potentially hazardous situation arises due to a person moving from the dynamic sensor area surrounding the hazard area into the hazard area.

[0024] The sensor unit can be configured to detect persons located within the projection area by detecting persons in a static sensor area corresponding to the hazard area to be secured. The sensor unit can also be configured to detect persons located outside this hazard area to be secured by detecting persons in a dynamic sensor area that surrounds the hazard area to be secured and corresponds to the dynamic sensor area with the exception of the static sensor area or hazard area to be secured that it encompasses. This is achieved in particular by the stationary integration of the projection unit and sensor unit into a common device and by aligning the sensor such that the sensor area is larger than the projection area and includes the hazard area to be secured.The dynamic sensor range, which extends beyond the edges of the hazard area to be protected, not only protects the user already in the hazard zone, but also protects people moving into it. The dynamic sensor range ensures sufficient reaction time to safely limit the light sources in the projection area when a person moves into the hazard zone.

[0025] The optical measuring device can be configured to change the extent of the dynamic sensor range in relation to the detection speed and / or the movement speed of a person to be detected or detected and / or the movement of the optical measuring device. This allows the size of the dynamic sensor range to be adapted to the speed of persons moving within the measuring space expected for intended use. The extent of the dynamic sensor range can also be adapted to the typical or maximum movement speed of the optical measuring device itself when it is moved to perform its measuring tasks. This allows, for example, a distinction to be made between hand-held and robot-operated optical measuring devices.

[0026] The hazardous area to be protected, i.e., the static sensor area, can be determined by the light cone of the projection unit. This can be, for example, a cone with a circular or oval cross-section, or a polygonal pyramid shape. The dynamic sensor area extending beyond this can have the same shape and a larger area than the static sensor area. However, it is also conceivable that the outer contour of the dynamic sensor area has a different, possibly even asymmetrical, shape.

[0027] The sensor unit can, for example, have a radar sensor, a PIR sensor (passive infrared detector) and / or a ToF sensor (time-of-flight camera with photoelectric mixer detector - PMD).

[0028] Radar sensors are very compact and reliable. They can be easily integrated into an optical measuring device. Radar sensors are particularly sensitive to water-containing bodies and less sensitive to inert objects, such as a target, a measuring backdrop, and auxiliary mechanisms, thus enabling easy differentiation between endangered persons and non-hazardous objects.

[0029] PIR sensors are based on passive infrared sensors and are also easy to integrate. They are available as inexpensive, proven components. With PIR sensors, it is possible to detect heat radiation emitted by living beings up to a distance of several meters. PIR sensors can be used more easily to detect not only heat radiation but also the movement of living beings. An equally readily available and easily integrated sensor option is ToF (Time of Flight) sensors, which detect movement using a time-of-flight method with a 3D camera system. Using an LED or laser diode, a scene is illuminated and briefly illuminated with pulses, and the time-of-flight of the individual pixels is measured. Infrared light is usually used for this purpose. The illuminated scene is projected onto an optical sensor designed to measure the time-of-flight. A so-called photonic mixer detector (PMD sensor) is used for this purpose.To reduce interference from background light, an optical bandpass filter essentially only allows reflected light of the wavelength emitted by the projection unit to pass through. Security can be further enhanced by combining multiple sensors, especially several different sensor types. For example, additional PIR sensors can distinguish moving inanimate objects from a human head.

[0030] The sensor unit can be configured to analyze the movements of detected persons or objects in order to distinguish between endangered persons and non-endangered objects (objects). For example, the sensor unit can be equipped with a Doppler radar, which simultaneously measures the distance of objects and determines the relative speed of an object to the optical measuring device by calculating the frequency shift of the radar signal reflection from the transmitted radar signal.

[0031] It is also conceivable to use a pulsed radar, in which a phase shift of the pulses corresponding to the Doppler effect is used to determine speed. Due to the pulse method, a pulsed radar has very low power consumption and places lower demands on the computing power of the pulse phase analysis compared to the signal frequency analysis of a conventional Doppler radar.

[0032] In a similar way, motion analysis can also be carried out using a ToF sensor, which is also based on the basic principle of pulse phase analysis and at the same time has the advantage of being able to capture an entire scene at once.

[0033] Such motion analysis can distinguish moving, especially living, objects from static ones. Humans can always be detected through motion analysis due to their constant movement, for example, through tremors, breathing, and heart rate. This applies particularly to the frontal head, which is particularly relevant for protecting against hazards caused by excessive light output in the projection area.

[0034] Using such a sensor device together with a motion analysis, measurements can be carried out in scenes where inanimate parts, such as the measuring object, measuring backdrop, auxiliary mechanics, etc., extend into the potential hazard area (hazardous distance).

[0035] The sensor unit can have multiple redundant sensors of the same or different types. The use of a radar sensor, in particular, allows for the parallel use of multiple sensors without mutual interference.

[0036] The invention is explained in more detail below using an exemplary embodiment with the accompanying drawings. They show:

[0037] Figure 1 - Sketch of a light source with projection lens and a potential hazard zone in the projection area;

[0038] Figure 2 - Sketch of an optical measuring device with static and dynamic sensor range;

[0039] Figure 3 - Sketch of an optical measuring device with a conical hazard zone and a radar beam surrounding it as the sensor area;

[0040] Figure 1 shows a sketch of a light source 1 of a projection unit for emitting, for example, laser light or comparatively bright, potentially eye-damaging light (e.g., LEDs, etc.). This light is guided through a projection optics 2 to emit a projection pattern. The projection area P includes a hazardous distance 3, in which the eyes of people can be damaged if the person looks into the light source 1.

[0041] Therefore, users must either wear protective goggles or the light output in hazard zone 3 must be limited so that there is no danger to a person when they are in hazard zone 3.

[0042] Figure 2 shows an optical measuring device 4 with a device housing 5. This can be designed, for example, as a simple carrier or as a housing to which further components of the optical measuring device 4 are installed or attached.

[0043] The optical measuring device 4 has a projection unit 6 with a light source 1 and projection optics 2 for projecting a desired structure onto an object located in a projection area P. The projection area P includes a hazardous area 3 in which the amount of light incident on the user's eyes is so large that the user's eyes are endangered if the user is located in the hazardous area 3 and, in particular, looks into the light source 1.

[0044] The optical measuring device 4 further has a camera unit, which in the illustrated embodiment is formed from two cameras 8a, 8b.

[0045] The camera unit with its cameras 8a, 8b together with the projection unit 6 is connected to the common device housing 5 in such a way that the optical measuring device forms a manageable unit in which the position of the camera unit 8a, 8b and the projection unit 6 relative to one another is fixed, even if the projection area P changes due to changes in the position of the optical measuring device 4.

[0046] The hazardous area 3 forms a static sensor area of ​​a sensor unit (not shown). If a person is located in this hazardous area 3, the light output of the projection unit 6 is limited such that any danger to the person located in the hazardous area 3 is reliably excluded. This hazardous area 3 represents the portion of the projection area P of the projection unit 6 to be secured within the meaning of the present invention, whereby the hazardous area 3 can also correspond to the entire projection area P.

[0047] The area extending beyond this, shown in dashed lines, forms a dynamic sensor area 7. This is monitored with the help of the sensor unit in order to detect a person moving into the danger area 3 and to be able to limit the light output in good time before entering the danger area 3. The extent of the dynamic sensor area 7 can depend on the expected speed at which a person moves into the danger area 3 or the static sensor area. On the other hand, the extent of the dynamic sensor area 7 can also depend on the detection speed. The speed at which a sensor unit detects people within the dynamic sensor area 7 can be taken into account. However, the movement speed of the optical measuring device 4 itself can also be a measure for adjusting the extent of the dynamic sensor area 7.For this purpose, the optical measuring device 4 can have an acceleration and / or motion sensor, the signal output of which is used to adjust the extent of the dynamic sensor range 7.

[0048] Figure 3 shows a sketch of the optical measuring device 4. There, the projection unit 6, together with the camera unit formed from the exemplary embodiment comprising two cameras 8a, 8b, is integrated into a common device housing 5, i.e., on a common support. The projection unit 6, with its projection lens, has a projection area P that encompasses the hazardous area 3 as a particularly vulnerable area that must be secured (hazardous distance). The hazardous area 3 can correspond to the projection area P or be only a part of it.

[0049] The optical measuring device 4 projects a structure, such as a striped pattern, onto an object located in the projection area P, and in particular in the hazard zone 3, with very high brightness, e.g., based on a laser light source. The rays reflected by the object are measured by the cameras 8a, 8b, and the captured image of the object with the projected patterns is evaluated using conventional triangulation methods with an evaluation unit (not shown) to measure the object three-dimensionally.

[0050] In order to detect a person in the danger zone 3 and to reduce the light output to a safe level in the event of a person's presence or entry into this danger zone 3, a sensor unit 9, for example, with radar sensors, is provided. The sensor unit 9 is designed to detect the presence of objects and persons in a sensor area 11 (e.g., radar beam) by emitting radar signals, receiving reflected radar signals, and measuring the time of flight. The sensor unit 9 is integrated into the device housing 5 on a sensor mount 10.

[0051] It is clear that the sensor area 11 encompasses the danger zone 3, i.e. the part to be secured or possibly even the entire projection area P. This danger zone 3 to be secured is completely enclosed by the sensor area 11, i.e. the radar beam. In this way, it is not only possible to detect the presence of people in the static sensor area (i.e. in the danger zone 3) in order to limit the light output to a safe level or to switch off the light source of the projection unit 6 completely if a person is present in this static sensor area (i.e. the projection area to be secured or the danger zone 3). Rather, the surrounding dynamic sensor area 7 also monitors the essentially safe surroundings of the danger zone 3 in order to be able to detect the presence of and the danger of people entering the danger zone 3 at an early stage.

[0052] This means that if a user is in the danger zone 3 or there is a risk of the person entering the danger zone 3, the light output can be limited so that the operation of the optical measuring device 4 is possible in a protection class that is no longer classified as dangerous.

[0053] For example, the optical measuring device 4 can be classified in laser class greater than 2 according to DIN EN 60825 for a laser light source without monitoring the hazardous area 3, or in protection class RG-3 according to DIN EN 62471 for other light sources. By monitoring the presence of persons in the hazardous area 3 and in the surrounding dynamic sensor area 7, together with the inevitable reduction of the light output when a person is detected in the hazardous area 3 and, if necessary, additionally in the dynamic sensor area 7, this optical device 4 can be classified in a lower protection class, e.g. laser class 2 or RG-2, since the light dose specified there is never exceeded due to the reduction of the light output.

[0054] The light output is preferably not limited to zero (switching off), but to a non-critical level so that the light source is still recognizable and it is clear that the sensor is active.

[0055] The sensor area 11, e.g. the radar beam, can be the physical sensor area in which a person can be detected. It is conceivable that this sensor area 11 is still different from the dynamic sensor area 7 that surrounds the danger area 3, i.e. the static sensor area. When evaluating the sensor data for the sensor area 11, only a part of the technically detectable sensor area 11 can be used to detect the presence of potentially endangered persons or objects when assessing the risk situation and regulating the light output of the projection unit 6. The size of this dynamic sensor area 7 to be taken into account can be selected in particular as a function of the detection speed of the sensor unit 9, the actual or expected movement speed of persons and / or the movement speed of the optical measuring device 4 itself.

Claims

Patent claims 1. Optical measuring device (4) for three-dimensional optical measurement of objects, wherein the optical measuring device (4) has a device housing (5) in which a projection unit (6) for projecting a measurement structure onto the surface of the object to be measured into a projection area (P) and a camera unit (8a, 8b) for recording images of the object provided with the projected measurement structure is integrated, characterized in that the device housing (5) further has a sensor unit (9) for detecting persons in a sensor area (11) detected by the sensor unit (9), and that the optical measuring device (4) is configured, upon detection of the presence of a person in the sensor area (11) or a part of the sensor area (11), to limit the light power to a level that is safe for a person located in a danger zone (3) of the projection area (P).

2. Optical measuring device (4) according to claim 1 , characterized in that the optical measuring device (4) is configured to switch off the projection unit (6) or reduce the brightness of the projection unit (6) when the presence of a person in the sensor area (11 ) or a part of the sensor area (11 ) has been detected.

3. Optical measuring device (4) according to claim 1 or 2, characterized in that the sensor area (11 ) is larger than the danger area (3) of the projection area (P) and includes the danger area (3).

4. Optical measuring device (4) according to claim 3, characterized in that the sensor unit (9) is designed to detect persons located in the danger zone (3) of the projection area (P) by detecting persons in a static sensor area corresponding to the danger zone (3), and is set up to detect persons outside the danger zone (3) by detecting persons in a dynamic sensor area (7) which corresponds to the dynamic sensor area (7) except for the danger zone (3) encompassed therein and is within the entire sensor area (11).

5. Optical measuring device (4) according to claim 4, characterized in that the optical measuring device (4) is configured to change the extent of the dynamic sensor area (7) in relation to the detection speed and / or a movement speed of a person to be detected or detected and / or a movement of the optical measuring device (4).

6. Optical measuring device (4) according to claim 5, characterized in that the device housing (5) has a speed and / or acceleration sensor for measuring the speed and / or acceleration of the device housing (5) and is configured to adjust the extent of the dynamic sensor area (7) depending on the detected speed and / or acceleration of the device housing (5).

7. Optical measuring device (4) according to one of the specified claims, characterized in that the projection area (P) and / or the danger area (3) are determined by the light cone of the projection unit (6).

8. Optical measuring device (4) according to one of the preceding claims, characterized in that the sensor unit (9) has a radar sensor, a PIR sensor and / or a time-of-flight sensor (ToF).

9. Optical measuring device (4) according to one of the preceding claims, characterized in that the sensor unit (9) has a radar sensor and is configured to detect movements of a detected person and to detect a person by detecting the presence of an object or person in the sensor area (11) and recording a movement for the detected presence. Optical measuring device (4) according to claim 9, characterized in that the radar sensor is a Doppler radar or a pulsed radar. Optical measuring device (4) according to any one of the preceding claims, characterized in that the sensor unit (9) has several redundant sensors. Method for three-dimensional optical measurement of objects with an optical measuring device (4) according to any one of the preceding claims, characterized by detecting persons in a sensor area (11) detected by the sensor unit (9) and limiting the light power of the projection unit (6) to a level that is harmless to a person located in the danger zone (3) when the presence of a person in the sensor area (11) or a part of the sensor area (11) has been detected.A method according to claim 12, characterized by adjusting the extent of a dynamic sensor area (7) in relation to the detection speed and / or a movement speed of a person to be detected or detected and / or a movement of the optical measuring device (4), wherein the dynamic sensor area (7) corresponds to the dynamic sensor area (7) of the sensor unit (9) with the exception of the danger zone (3) encompassed therein. A method according to claim 12 or 13, characterized by switching off the projection unit (6) when the presence of a person in the sensor area (11) or a part of the sensor area (11), in particular in the dynamic sensor area (7) and / or the danger zone (3), has been detected.

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