DE102016110514A1 - Device and method for monitoring a room area, in particular for securing a danger zone of an automated system - Google Patents

Abstract

Device (10) for monitoring a spatial area (40), in particular for securing a danger zone of an automated system (14). The device comprises a first illumination device (34) which is designed to at least temporarily transmit light signals into the spatial region (40) and an image acquisition unit (32) which is designed to produce an image of the spatial region (40), wherein the An image pickup unit (32) has an image sensor (38) having a plurality of pixels that image a plurality of space area points (44). Furthermore, the device has an evaluation unit (24), which is designed to determine a first distance value (52) for at least one spatial area point (44) by transit time measurement of the light signals, and a control unit (28), which is designed as a function the first distance value (52) to trigger a safety function. The first illumination device (34) and the image acquisition unit (32) are arranged in a defined acquisition geometry (58, 60, B) and the first illumination device (34) is further adapted to convey an optical pattern (54) into the spatial region (40) projecting, wherein the evaluation unit (24) is adapted to determine from the optical pattern (54) and the defined receiving geometry (58, 60, B) a second distance value (74) for the at least one spatial area point (44) and with the first Distance value (52) to correlate, depending on the correlation to generate an error signal.

Description

The present invention relates to a device for monitoring a spatial area, in particular for securing a danger zone of an automated system, comprising a first illumination device, which is designed to at least temporarily transmit light signals into the spatial area, an image acquisition unit, which is adapted to an image of the spatial region, the image acquisition unit having an image sensor with a plurality of image points which image a plurality of spatial area points, an evaluation unit which is designed to determine a first distance value for at least one spatial area point by means of transit time measurement of the light signals, and a control unit, which is designed to trigger a safety function as a function of the first distance value.

Furthermore, the present invention relates to a method for monitoring a spatial area, in particular for securing a danger zone of an automated system, wherein a first illumination device at least temporarily transmits light signals into the spatial area, an image acquisition unit with an image sensor with a plurality of pixels takes an image of the spatial area, wherein by means of travel time measurement a first distance value is determined for a room area point located in the spatial area and a safety function is triggered as a function of the first distance value.

Such a device and such a method are known from DE 10 2005 056 265 A1 known.

The device and the method according to the DE 10 2005 056 265 A1 use camera systems with time-of-flight (TOF) meters to monitor the room area. These are designed to additionally provide depth information of this scene in addition to a two-dimensional image of a recorded scene. Time-of-flight (TOF) cameras capture a scene not just two-dimensionally, but three-dimensionally.

The principle of a time-of-flight measuring device is similar to that of a laser radar. A light pulse or a periodic sequence of light pulses is transmitted by a transmitter into the spatial area and reflected there. A receiving device receives the light pulses and, based on the transit time, determines the distance to the point of reflection. However, compared to a laser radar, a time-of-flight camera has an image sensor with a multiplicity of pixels (also called pixels) and determines the transit time for each of these pixels so that a large number of measurements are performed per unit of time. Thus, a three-dimensional image is generated per time unit, which in addition to or instead of the detection of intensities (brightnesses) and the output of gray values, distance information or transit time information.

The term "mapping" in the sense of this disclosure is thus not to be understood as a perception by the human eye, but a technical description of a scene with data which, in addition to the usual two-dimensional image values, additionally includes the position of a surface of an object in a spatial area. Three-dimensional mapping or a temporal sequence of three-dimensional images can consequently be segmented, categorized and classified by suitable data processing methods, in particular image analysis algorithms, whereby individual objects such as persons and objects can be released, identified and distinguished.

Like in the DE 10 2005 056 265 A1 described, allows a three-dimensional detection of a space area better ways to detect and assess a dangerous situation, such as the intrusion of a person in a danger zone. In addition, monitoring with image acquisition and image evaluation units is more flexible and easier to adapt to new environmental conditions than rigid safety systems permanently mounted on a system, such as light barriers or light grids. It is thus desirable to use systems capable of producing three-dimensional images for monitoring technical equipment and machines.

From the DE 10 2005 056 265 A1 It is also known that in safety-critical applications, high demands are placed on the monitoring sensor and the reliability of the data acquired by the sensor, so that ordinary sensors without additional equipment can not regularly be used for safety-critical applications. This also applies to time-of-flight measuring equipment and distance values recorded by it. In particular, objects may be recognized by ambiguity due to periodic modulation of the light signals or due to detour reflections elsewhere than they are in reality. A faulty distance measurement, however, has the consequence that dangerous situations may arise when, for example, an object located in the danger area is judged by the time-of-flight cameras to be outside the danger zone or to insufficient availability, for example one Machine in the danger area when an object is outside the danger area, but this is from the time-of-flight cameras due to erroneous distance measurement located in the danger area is judged, and the machine is therefore turned off.

In order to address this problem, sensors in the safety-critical environment regularly have facilities with which they can check their own functionality and verify the recorded data. A known means is a redundant design of the essential elements of a sensor in combination with a test device, which compares the data collected by the sensor with those of the redundant components and triggers the safety function in case of deviations. This principle also finds in the DE 10 2005 056 265 A1 Application by recording and evaluating two images of the spatial area, preferably of two separate time-of-flight cameras, in order to exclude or at least master the above-mentioned errors.

However, a redundant design is often expensive, especially if, as in the DE 10 2005 056 265 A1 suggested that the camera unit of the sensor must be designed twice. In addition, not all errors can be detected by a simple redundancy. In particular, common cause failures, called common course failures, can not be ruled out when using identical components. For example, hidden design or manufacturing defects of the redundant components can not be detected.

Against this background, it is an object of the present invention to provide a cost-effective device and a method for securing a danger zone of an automated system, which can also detect common cause errors with little effort.

According to one aspect of the present invention, this object is achieved by a device of the type mentioned above, wherein the first illumination device and the image acquisition unit are arranged in a defined acquisition geometry, the first illumination device is further configured to project an optical pattern into the spatial region, and the Evaluation unit is designed to determine based on the optical pattern and the defined recording geometry, a second distance value for the at least one spatial area point and to correlate with the first distance value to generate an error signal as a function of the correlation.

The object of the invention is also achieved by a method of the type mentioned, in which the first illumination device and the image pickup unit are arranged in a defined recording geometry, the first illumination device projects an optical pattern in the spatial area, and the evaluation unit based on the optical pattern and the defined recording geometry determines a second distance value for the at least one spatial area point and correlated with the first distance value and generates an error signal as a function of the correlation.

The above task is thus completely solved.

It should be noted that for the purposes of the present disclosure, the danger zone of an automated system is to be understood as the area on or in front of a technical system in which a person or an object poses a danger from the system in operation. An automated system may be, for example, a press or an industrial robot. Accordingly, a safety function is understood to mean that the automated system operates in such a way that it can no longer pose a danger to a person or an object, for example by interrupting the power supply of the system. It is understood that in other cases, the safety function can also consist in the system - without switching off - to transfer to a safe state.

A lighting device in the sense of the disclosure is a light source which is designed to emit light beams directly or indirectly in the spatial area. The image recording unit in turn is designed to detect the light emitted by the illumination device which is reflected in the spatial region. The term imaging unit is to be understood generally in the present disclosure. By way of example, an imaging unit can be understood merely as an image sensor with associated optics, such as a digital camera with an optoelectronic image sensor. For the purposes of the present disclosure, the distance value is the distance from a point in the spatial region at which the light from the illumination device is reflected to the image sensor. It is understood that another reference point for the distance measurement, for example the front side of the sensor housing, can also be used by calibration.

The peculiarity of the new device of the new method is that a first and a second distance value are determined for a spatial area point, wherein different measurement methods are used for the determination. On the one hand, the first distance value is determined by means of a transit time measurement. Here, a pulse transit time method or a Phase delay method can be applied. On the other hand, a second distance value is determined by means of an optical pattern and trigonometric calculation. This is also known as a light-section method.

The pulse transit time method and the phase transit time method are both based on the principle that it is determined how long an emitted light beam needs to travel from the illumination device to the object and back to the image sensor.

The distance measurement based on an optical pattern uses the principle of trigonometry. For this purpose, an optical pattern is projected into the spatial area whose image is changed by the image recording unit when the optical pattern is "consumed" by an object in the spatial area. An optical pattern can be generated in various ways. Preferably, however, an optical pattern in the sense of the present disclosure is a pattern formed from individual spots of light. From the distortion of the pattern and with defined acquisition geometries, distance values to a surface of the object located in the spatial area can be determined by trigonometric calculation.

For the purposes of the present disclosure, recording geometry means the arrangement of the illumination device that generates the pattern and the image acquisition unit that images the pattern. For a distance measurement, at least the relative position of the first illumination device with respect to the image acquisition unit and their respective orientation must be known. In other words, the recording geometry designates the location and position of the illumination device and of the image acquisition unit, which must be known to the evaluation device in order to be able to calculate a distance value.

An advantage of the new device and the new method is that a first distance measurement can be verified by a second distance measurement, wherein the second distance measurement is performed by a different method and based on a different principle. In particular, systematic errors in the measurement of the distance value can thus be excluded. The new device is also cheaper, since at least partially dispensed with a redundant design of the essential components of the sensor. Nevertheless, due to the redundant measuring method, the device can advantageously be used in the industrial environment as a non-contact protective device.

In a further preferred embodiment of the device, the first illumination device has at least one first light source for generating the light signals for the propagation time measurement, wherein the at least one first light source is further configured to generate the optical pattern.

By using a single light source both for generating the light signals for transit time measurement and for generating the optical pattern, the new device can be constructed in a particularly simple and cost-effective manner. Both measurement methods can thus be performed and combined with a single illumination device. In particular, the light source determines the structure of the optical pattern. Thus, for example, by the arrangement of the light sources, a structure can be predefined, which is projected via an imaging optics into the spatial region as an optical pattern.

The first illumination device preferably has point light sources arranged in matrix form and is set up such that it illuminates the spatial region directly by means of the point light sources in order to generate the optical pattern.

The matrix-like point light sources thus generate light spots in the spatial region, which correspond to the matrix-like arrangement of the point light sources. The light spots in the form of a matrix correspond in turn to the optical pattern which is used for the second measuring method. In this case, point light sources produce punctiform light spots, which can be used particularly easily for a triangulation measurement, since their center can be determined in a simple manner using conventional image processing methods.

In a further preferred embodiment, the first illumination device is designed to temporarily homogenize the light signals.

By temporarily homogenizing the light signals that are emitted by the first illumination device, the spatial area can be uniformly illuminated, whereby a uniform distance determination for each pixel of the image sensor can be made. Thus, the resolution of the image pickup unit during the uniform illumination can be increased to the maximum resolution determined by the number of pixels.

Particularly preferably, the device has a second illumination device with a transparent diffuser for uniform illumination of the spatial area, the device being set up to illuminate the spatial area optionally with the first or the second illumination device.

The device thus has in this embodiment two modes of operation, a normal mode and a test mode. In normal operation, the room area is illuminated with uniform light, so that a distance value can be determined for all pixels of the image sensor. In test mode, the optical pattern is generated, based on which the distance measurement for selected points is verifiable. In normal operation, a time-of-flight image can thus be generated in full resolution of the image sensor, which can be verified at certain intervals by the test operation.

It further adds to simplification when defining a tolerance range in which the first distance measurement and the second distance measurement are considered equal, i. H. the difference of the first distance value from the second distance value is below a defined threshold value. If the first distance value and the second distance value are equal, a determination of the two values can determine a more precise distance value compared with a single measurement, which can be used for the assessment.

In a further preferred refinement, the evaluation unit is designed to average the first and second distance values if the difference lies in the defined tolerance range, and the control unit is designed to trigger the safety function as a function of the averaged distance value. By averaging the measured distance values, a more precise distance measurement can be achieved in a particularly simple manner.

In a further preferred refinement, the evaluation unit is set up to determine the first and second distance values for a plurality of spatial area points. If the distance values for all room area points or for a certain group of room area points as a whole are greater than or in total smaller than the second distance values, there is a systematic error that can be corrected by the control unit by triggering the safety function as a function of the second distance value. Advantageously, thus systematically caused measurement errors, such as those caused by stray light or temperature effects, can be detected and controlled.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. Show it:

1 : a simplified representation of a preferred field of application of the device according to the invention and of the method according to the invention,

2 : a simplified representation of the new device for monitoring a space area,

3 : a schematic representation of the geometric relationships used according to the invention,

4 : a section of a scene with an object inside,

5 a further preferred embodiment of a sensor part of the new device, and

6 : Another embodiment of the new device.

1 shows a simplified representation of a preferred field of application of the device according to the invention and the method according to the invention. The new device is in its entirety with the reference numeral 10 designated. The device 10 is located here in the ceiling area of an industrial building and monitors a hazardous area 12 , The danger area 12 has a three-dimensional extent and thus extends in an X, Y and Z direction. The danger area 12 is here along a technical facility 14 arranged by an industrial robot 16 is indicated. The industrial robot 16 has an arm 18 , from its movement in the danger area 12 a danger to a person 20 can go out.

The new device 10 is, as will be explained in more detail below, adapted to the entry of a person 20 in the danger area 12 to detect and trigger a safety function. The safety function could consist in that a safety switching device, not shown here, on requests of the device 10 the robot 16 de-energized. It is understood that the safety function could also be the robot arm 18 to turn away from the person without the entire robot 16 is switched off.

In 1 a uniform danger area is shown, which has a substantially cuboidal extent. In other embodiments, the area may also be otherwise extended, structured, or even segmented. There the device 10 is designed to create a three-dimensional image of the danger area 12 By means of efficient data analysis, only interesting areas of the danger area can be extracted from the image by means of an efficient data analysis.

It is thus possible to assign different functions to different areas within the danger area. For example, the safety function could only be triggered as a last resort when a person enters a critical area of the danger zone 12 occurs while entering the areas in front of the critical area only a warning is issued.

In addition, the new device offers the possibility to differentiate between different objects in the danger area, so that, for example, the safety function only when a person enters 20 is triggered, but not by another object, such as another robot, which can not correspond to the surface geometry of a human.

It is understood that in 1 shown application example is to be understood only as an example. Thus, in another embodiment, the device can also be used only for monitoring a small section of a larger installation, for example a press in the reception area. Here, the device may for example also be arranged on a movable part of the press.

2 shows a simplified representation of the new device for monitoring a space area, in their entirety by the reference numeral 10 is designated. The device essentially has a sensor part 22 , an evaluation unit 24 with a testing device 26 , a control unit 28 and a connection unit 30 on. The evaluation unit 24 , the control unit 28 and the connection unit 30 are shown here as examples as separate units. In other embodiments, however, their tasks may also be performed by a single integrated unit.

The sensor part 22 includes an image capture unit 32 and a first illumination device 34 , The image capture unit 32 has an optic 36 and an image sensor 38 with a plurality of pixels (pixels). The optics 36 forms the front of the sensor part 22 lying room area 40 on the image sensor 38 from. The optics 36 may include other optical elements, such as filters and lenses. Preferably, the optics 36 a filter that is only transparent to light of a certain wavelength. Such a filter allows the image of the image acquisition unit 32 to reduce to the essentials.

In 2 is a detection area of the image pickup unit 32 indicated by two dot-dash lines. Within the coverage area is an object 42 , which due to its spatial extent usually on several pixels of the image sensor 38 is shown. In order to simplify the explanations of the procedure according to the invention, it is intended merely to refer to a point of the object which here is referred to as the spatial area point with the reference number 44 is indicated.

Preferably, the device is 10 for easy installation in a housing 45 arranged. The housing 45 can be completely closed for protection against contamination and preferably has exclusively for the optics of the image recording unit 32 and the first lighting device 34 Openings on. Particularly preferred for use in safety-critical applications in industrial environments is the housing 45 a housing which has a degree of protection of IP67.

About a usually multi-pin connector 47 on the housing 45 the device is contacted from the outside, including the power supply. Furthermore, via the connection unit 30 and the connector 47 the safety function is communicated to a safety switching device (not shown here) which implements the safety function, for example by the machine to be monitored 14 off.

About the connection unit 30 In another embodiment, the error signal or that of the sensor part 22 recorded distance values are transmitted, which are evaluated by a higher-level control unit. For example, several sensors according to the invention can cooperate in order to generate a complex monitoring area. Likewise, the device according to the invention can also be operated together in a network with other sensors.

The first lighting device 34 is set to light in the front of the sensor part 22 lying room area 40 to send. Preferably, it is light in a wavelength range not visible to humans, such as infrared light. Infrared light is not visible to humans, but it can be detected well and efficiently for an image sensor using CCD or CMOS technology.

The first lighting device 34 has a light source in the embodiment shown here 46 with matrix-like LEDs 48 on. The LED matrix may include an imaging optics, not shown here. In other exemplary embodiments, the illumination device can also be designed as a slide projector, as a point light source with a facet mirror or as a digital light processing (DLP or DMP) projector. Likewise, the lighting device 34 be designed as a vertical cavity surface emitting laser (VCSEL) array. A VCSEL array has the advantage that it can be arranged on a chip with a very small footprint. Thus, the active area of such an array may comprise a few square millimeters, for example 1.9 mm × 1.75 mm, whereby more than 2000 individual VCSELs may be arranged on this area. By means of a corresponding imaging optics, the VCSELs of the array can be imaged in space.

The first lighting device 34 illuminates the room area 40 and the object in it 42 , It also becomes a light beam 50 at the room area point 44 reflected, wherein a part of the reflected light to the image pickup unit 32 passes through and through the optics 36 on a pixel of the image sensor 38 is shown.

The image capture unit 32 and the evaluation unit 24 determine the individual transit time (pulse duration or phase delay) for each pixel by means of a comparison with the emitted light and calculate therefrom the first distance value which is indicated by the arrow 52 is indicated and the distance between space area point 44 and image sensor 38 equivalent. It is understood that by suitable calibration for the determination of the distance also a different reference point than the image sensor 38 can be selected, for example, the center 55 at the front of the case 45 ,

In addition, the first lighting device 34 so formed an optical pattern 54 in the room area 40 to project. In the embodiment shown here, the optical pattern is 54 from a variety of light spots 56 together, with each light spot 56 here an LED 48 the light source 46 assigned. The light spots 56 of the optical pattern 54 are accordingly arranged in the same way as the LEDs 48 the light source 46 , so here also matrix-like. It is understood that such a pattern 54 also with the alternatively mentioned lighting devices 34 can generate.

Preferably, the optical pattern 54 thus a homogeneous dot pattern, ie the light spots 56 are distributed periodically and evenly along two major axes. The structure of the optical pattern 54 is advantageous only by the arrangement of the light source 46 , So in the present embodiment, the (matrix-like) arrangement of the LEDs 48 , certainly. So can easily a usable matrix-like dot pattern 54 generated and in the space to be monitored 40 be projected. It is understood that in addition an imaging optics for imaging the pattern can be used, wherein the structure of the pattern according to the invention by the light source 46 is determined. In particular, an imaging optics can have one or more converging lenses. According to the invention, however, the same light source 46 for emitting the light beams for transit time measurement and for generating the optical pattern 54 used.

It is understood that in the inhomogeneous illumination of the space area by the optical pattern 54 not for all pixels of the image sensor 38 a transit time measurement can be performed. So is a transit time measurement for the areas between the light spots 56 not possible.

For security applications, however, a pixel-precise resolution and determination of the distance values is not necessary, since as a rule a certain minimum object size of the objects to be monitored is assumed. It is thus sufficient if the optical pattern 54 is designed so that an object 42 with the prescribed minimum object size of at least one light spot 56 is detected. Preferably, the distance between two points is 5 to 10 pixels. In the embodiment according to 2 becomes the object 42 through the optical pattern in the light spot 56 ' illuminated.

To determine a second distance value by triangulation measurement is in addition to the optical pattern 54 an exact knowledge of the recording geometry necessary. The defined recording geometry is at least determined by the relative position of the first illumination device 34 with respect to the image acquisition unit 32 and their respective orientation defined. In 2 is the location of the image acquisition unit 32 in relation to the first lighting device 34 by the base distance B and the alignment by the optical axes 58 . 60 indicated.

The defined receiving geometry is thus described by a set of parameters, by the structure of the sensor part 22 is predetermined. In a rigid arrangement of the image pickup unit 32 and the first illumination device 34 this can be a set of parameters. In a preferred embodiment, however, the parameters can be set and adjusted by a corresponding calibration.

From the defined recording geometry and the recorded image of the optical pattern 54 determines the evaluation unit 24 a second distance value by trigonometry. A preferably in the evaluation unit 24 integrated testing device 26 compares for the room area point 42 the first and the second distance value. If the first and the second distance value are to be regarded as equal within the scope of the measurement accuracy, the first distance value has been confirmed by the second one. If the first distance value and the second distance value deviate from one another, an error signal is generated which reflects the deviation.

Various actions are possible in response to the error signal. In one embodiment, the safety function can be triggered directly by the error signal. In other exemplary embodiments, a further measurement can be based, for example, on further light spots 56 of the optical pattern 54 be made. Furthermore, in another embodiment, the error signal for further evaluation to a higher-level control unit (not shown here) are transmitted, which makes an evaluation of the error signal.

For larger deviations of the measured distance values, a combination of different measurements with the two methods can be used to find an adequate solution for a situation. For example, the distance measurements may be repeated with other possible points of the optical pattern. Furthermore, systematic errors (scattered light, temperature effects, etc.) can also be detected, for example if the determination of the first distance values by the time-of-flight measurement always leads to values which are greater in all or at least in relevant subregions than in the corresponding determination by means of the optical pattern 54 , Advantageously, thus measuring errors can not only be detected, but partially also be corrected.

3 shows a schematic representation of the geometric relationships used in the invention. 3 shows a sensor part 22 with an image capture unit 32 and a lighting device 34 and an optical pattern projected into the space area 54 ,

The optical pattern 54 Here is a homogeneous dot pattern, ie the light spots 56 are single points along two major axes 62 . 64 are distributed periodically and evenly. The main axes 62 . 64 are shown here by way of illustration only and are to be found in the optical pattern projected in practice 54 not again. The two main axes 62 . 64 , which are perpendicular to each other here, give the two directions of the smallest distances of the light spots 56 of the optical pattern 54 at.

In 3 is the optical pattern 54 only partially shown with 25 spots of light. In practice, the optical pattern 54 a significantly higher number of light spots 56 exhibit. The distance of the individual light spots or the centers of the individual light spots is preferably five to ten pixels of the image sensor of the image recording unit 32 ,

It is understood that another pattern may be used. A dot pattern is advantageous because it is easily accessible through the first illumination device 34 can be generated as described above.

In a particularly preferred embodiment, the optical pattern 54 is produced by the usual diffuser is removed by a conventional lighting device of a time-of-flight measuring device with light sources arranged like a matrix. The diffuser in a standard time-of-flight measuring device is used to homogenize the light of a light source to ensure a uniform illumination. By omitting the diffuser and introducing a corresponding imaging optics, the light sources present in the illumination device illuminate the spatial region directly and thereby preferably produce an optical pattern 54 , which can be used for the determination of the second distance value. The optical pattern 54 is very easy to create in this way. The first lighting device 34 in this case corresponds to a commercially available projector for a time-of-flight measuring device with a structured light source that is not homogenized. The structure of the light source determines the structure of the optical pattern 54 , The reduced resolution due to the omission of the diffuser is compensated by a higher range and the possibility of a second distance measurement.

In the 3 becomes a homogeneous dot pattern by the light sources in the first illumination device 34 generated. The optical pattern 54 without it hits an object in the 3 on a flat wall 66 projected. Are the level wall 66 and the plane in which the light sources of the first illumination device extend parallel, so also the illustrated optical pattern is homogeneous. It is understood that for the operation of the new device of the new method, a flat wall 66 is not necessary and is shown here only for clarity.

For the light spots 56 First, their distance to the sensor part 22 determined by a time-of-flight measurement. Examples of the time-of-flight measurement are in 3 the rays of light 68 and 70 highlighted. The first ray of light 68 corresponds to a light beam of the light source of the first illumination means and the second light beam corresponds to a light beam resulting from the reflection of the first light beam 68 on the flat wall 66 at the point 72 results.

The time-of-flight measurement can take place according to a pulse transit time method or a phase transit time method.

In the pulse transit time method, the amplitude of the light wave is modulated in pulse form with a large pulse / pause ratio, ie at a low modulation frequency. This determines the time between the transmission and the return of the light signal ( 68 . 70 ) on the reflected object, here the point 72 on the flat wall 66 , has passed. In principle, it is possible for a far-away object to generate a reflection that is only received at a later measuring interval. This reflection is then erroneously assigned to a shorter distance value and thus leads to ambiguity due to the periodic modulation.

In the phase delay method, the amplitude of the light wave is modulated at a frequency in the high frequency range. The transit time determination of the measurement signal is carried out from the phase comparison of the modulation of the emitted light wave and the modulation of the incoming light wave. Again, due to the maximum phase differences of 360 °, it is possible for a far-away object to produce a reflection associated with a closer point in space. In other words, there are ambiguities in all transit time measurements that can jeopardize a reliable distance determination.

According to the invention, further distance determinations are thus carried out based on a different principle fundamentally different from the time-of-flight measurement. The further distance determination may be for one or more or all light spots 56 of the optical pattern 54 be performed.

For further distance determination according to the principle of triangulation, the evaluation unit 24 the optical pattern projected into the space area 54 and the receiving geometry of the sensor part 22 be known. The defined recording geometry is determined by the base width B, ie the spatial arrangement of the image recording unit 32 to the first lighting unit 34 , and the respective optical axes 58 and 60 the image acquisition unit 32 and the first lighting unit 34 sufficiently determined. Due to the recording geometry are at least three sizes of a triangle consisting of the center of a light spot 56 as well as the starting point of the illuminating light beam and the location of the receiving pixel known, from which the other sizes of this triangle and thus the sought second distance value 74 can be determined by calculation.

4 shows a section of the optical pattern to illustrate the second measuring principle 54 in opposite 3 enlarged scale and with an object located therein 42 , which is simplified here shown as a cuboid.

Four spots of light 56 ' of the optical pattern 54 are now on the surface of the object 42 projected and thus closer to the image acquisition unit 32 as the remaining spots of light 56 of the optical pattern 54 , For the image acquisition unit 32 turns the previously homogeneous dot pattern in the area of light spots 56 ' as distorted dar. Using light-section method can be the distortion of the distance of the respective points 56 ' to the image capture unit 32 be determined. In the illustrated embodiment, for example, set the main axes defined by the points 62 . 64 for the image pickup unit as straight lines while a corresponding line 76 parallel to the main axes passing through the points 56 ' runs according to the principle of stereoscopic vision through the object geometry of the image acquisition unit 32 appear deformed. The deviation from the straightness in the camera image is a measure of the object height, which also results in a second distance value 74 determine.

In combination with the time-of-flight measurement, there are thus a first and a second distance value on the basis of which an assessment of the recorded scene can take place. Preferably, at least for each light spot 56 . 56 ' of the optical pattern 54 separate first and second distance values 52 . 74 certainly.

The evaluation unit determines and verifies from the two distance values whether or not an unexpected object is detected as being in the spatial area and triggers the corresponding safety function, whereby the system to be monitored is transferred to a safe state.

5 shows a further preferred embodiment of the new device, wherein only the sensor part 22 is shown. Otherwise, the device corresponds to the device according to FIG 2 ,

The sensor part 22 differs from the previously described sensor part 22 by an additional second illumination device 68 next to the image acquisition unit 32 and the first illumination device 34 ,

Like the first lighting device 34 has the second illumination device 68 in this embodiment arranged in a matrix LEDs 48 on. It is understood that as a second lighting device 68 Also, the alternatives mentioned in relation to the first lighting device come into consideration.

As before regarding 2 described, the structure of the light source 46 the first illumination device 34 as an optical pattern 54 in the room area 40 projected. The projection takes place here via an imaging optics 79 , which is exemplified here by a condenser lens.

The second lighting device 68 In contrast, has a transparent diffuser in addition 78 on, in front of the light-emitting diodes 48 and thus between the light source 46 the second illumination device 68 and the room area to be illuminated 40 is arranged. The diffuser 78 dampens and diffuses the light from the light source 46 so that the room area 40 is evenly illuminated with diffused light. An optical pattern 54 as determined by the lighting with the first lighting device 34 arises when using the second illumination device 68 not generated. In other words, the structure of the light source, that is, for example, the matrix-like arrangement is not in the spatial area 40 imaged so that no pattern arises. It is understood that in addition to the diffuser 78 likewise a further imaging optics can be provided.

Advantageously, the new device between a lighting with the first illumination device 34 and the second illumination device 68 Change, as shown here schematically by a changeover switch 80 is indicated. It is understood that the control can also be done in other ways, for example by a direct control by the control unit (not shown here).

The different lighting options define two operating modes of the new device. In normal operation, the space area becomes 40 with the second illumination device 68 and diffused light evenly lit. In a test / test mode, the space area becomes 40 by the light source of the first illumination device 34 illuminated directly, so that in the space area the optical pattern 54 arises.

In normal operation, the room area 40 about the optics 36 the image acquisition unit 32 on the image sensor 38 shown, wherein for each pixel of the image sensor 38 a first distance value can be determined. It is thus possible to have a time-of-flight image of the space area 40 in full resolution of the image sensor 38 to create. In the test / test mode, these distance values can be verified in selected areas by determining second distance values.

In test / test mode is the first lighting device 34 disabled and the second illumination device 68 enabled, so in the room area 40 the optical pattern described above 54 is projected. The optical pattern 54 is from the image acquisition unit 32 recorded and second distance value determined by the light section method for selected areas. In the selected areas, the first distance values are thus determined from a transit time measurement and the second distance values are determined by a triangulation measurement from the respective point position. Based on the second distance values can thus be carried out a plausibility check of the first distance values.

In test / test mode, the resolution of the image is on the light spots 56 of the optical pattern 54 limited, while in normal operation, the resolution by the number of pixels of the image sensor 38 is determined. Preferably, therefore, the device is mainly used in normal operation and only occasionally by the with the first illumination device 34 generated optical patterns 54 checked. The check can be carried out, for example, in a specified interval or triggered by the evaluation if a cause from the first measurement is out.

It is understood that in a modification of this embodiment, only one illumination device can be used, wherein the diffuser 78 is designed as a variable element and can be optionally introduced into the light path of a lighting device.

6 shows a further embodiment of the new device, which substantially with the device according to the 2 matches. In addition, the device in this embodiment, however, a further image pickup unit 82 on which also the room area 40 maps. The further image acquisition unit 82 can, as shown here, be a separate entity. Alternatively, the further image acquisition unit 82 but also in the case 45 to be integrated with. The further image acquisition unit 82 is coupled to the device as indicated by the arrow 84 is indicated.

The further image acquisition unit 82 thus represents another illustration of the space area 40 available, which can be used to evaluate the scene. In the other image acquisition unit 82 It can be a standard camera or another ToF camera. Depending on what kind of picture the further image acquisition unit 82 can provide additional distance calculations are performed, further increasing redundancy and diversity. Preferably, the further image acquisition unit 82 in a further specific recording geometry to the first illumination device 34 and / or the first image acquisition unit 32 arranged so that additional parameters for the distance calculation are defined.

Through the further image acquisition unit 82 allows a particularly safe and precise monitoring of the room area 40 respectively.

In addition, it should be noted that the present invention is not limited to the above-described embodiments. Thus, the inventive method and the device according to the invention are not limited to the receiving geometry shown here. Likewise, the optical pattern 54 only as exemplary and, in particular, the optical pattern is not limited to a homogeneous dot pattern as shown here.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102005056265 A1 [0003, 0004, 0007, 0008, 0009, 0010]

Claims (13)

Contraption ( 10 ) for monitoring a room area ( 40 ), in particular for securing a danger zone of an automated system ( 14 ), comprising a first illumination device ( 34 ), which is designed to at least temporarily light signals in the space area ( 40 ), an image acquisition unit ( 32 ), which is designed to be an image of the spatial area ( 40 ), the image acquisition unit ( 32 ) an image sensor ( 38 ) having a plurality of pixels having a plurality of spatial region points ( 44 ), an evaluation unit ( 24 ), which is designed to measure a transit time of the light signals, a first distance value ( 52 ) for at least one room area point ( 44 ), and a control unit ( 28 ), which is designed as a function of the first distance value ( 52 ) trigger a safety function, characterized in that the first illumination device ( 34 ) and the image acquisition unit ( 32 ) in a defined receiving geometry ( 58 . 60 , B), the first illumination device ( 34 ) is further adapted to form an optical pattern ( 54 ) in the room area ( 40 ), and the evaluation unit ( 24 ) is designed to be based on the optical pattern ( 54 ) and the defined recording geometry ( 58 . 60 , B) a second distance value ( 74 ) for the at least one spatial area point ( 44 ) and with the first distance value ( 52 ) to produce an error signal depending on the correlation. Device according to claim 1, characterized in that the first illumination device ( 34 ) at least one first light source ( 46 ) for generating the light signals for the transit time measurement, wherein the at least one first light source ( 46 ) is further adapted to receive the optical pattern ( 54 ) generated. Device according to one of claims 1 or 2, characterized in that the first illumination device ( 34 ) has point light sources arranged in matrix form and is set up in such a way that it covers the spatial area ( 40 ) is illuminated directly by means of the point light sources in order to obtain the optical pattern ( 54 ) to create. Device according to one of claims 1 to 3, characterized in that the first illumination device ( 34 ) is adapted to temporarily homogenize the light signals. Device according to one of claims 1 to 3, characterized in that the device further comprises a second illumination device ( 68 ) with a transparent diffuser ( 78 ) for uniform illumination of the room area ( 40 ), the device being arranged to control the spatial area ( 40 ) optionally with the first or the second illumination device ( 34 . 68 ) to illuminate. Device according to one of claims 1 to 5 characterized by a defined tolerance range and in that the evaluation unit ( 24 ) is formed so that the difference of the first and second distance value ( 52 . 74 ) and to determine if this difference is within the defined tolerance range. Device according to claim 6, characterized in that the evaluation unit ( 24 ) is adapted to the first and second distance value ( 52 . 74 ), if the difference lies within the defined tolerance range, and the control unit ( 28 ) is designed to trigger the safety function as a function of the averaged distance value. Device according to one of claims 1 to 6, characterized in that the evaluation unit ( 24 ) is set up for a plurality of spatial area points ( 44 ) the first and second distance value ( 52 . 74 ), and the control unit ( 28 ) is adapted to the safety function as a function of the second distance value ( 74 ) when in a defined range of spatial area points ( 44 ) the distance values of the plurality of first distance values are larger or smaller than the distance values of the plurality of second distance values. Method for monitoring a room area ( 40 ), in particular for securing a danger zone of an automated system ( 14 ), wherein a first illumination device ( 34 ) at least temporarily light signals in the space area ( 40 ), an image acquisition unit ( 32 ) with an image sensor ( 38 ) with a plurality of pixels an image of the spatial area ( 40 ), whereby a first distance value ( 52 ) for a room area point ( 44 ) and depending on the first distance value ( 52 ) a safety function is triggered, characterized in that the first illumination device ( 34 ) and the image acquisition unit ( 32 ) in a defined receiving geometry ( 58 . 60 , B), the first illumination device ( 34 ) an optical pattern ( 54 ) in the room area ( 40 ), and the evaluation unit ( 24 ) based on the optical pattern ( 54 ) and the defined recording geometry ( 58 . 60 , B) a second distance value ( 74 ) to the at least one space area point ( 44 ) and the first distance value ( 52 ) correlates and generates an error signal as a function of the correlation. Method according to claim 9, characterized by a second illumination device ( 68 ), which homogenize the space ( 40 ), the room area ( 40 ) optionally with the first or the second illumination device ( 34 . 68 ) is illuminated. Method according to claim 10, characterized in that illumination of the spatial area ( 40 ) with the first illumination device ( 34 ) defines a test state and illuminates the spatial region with the second illumination device ( 68 ) Defines a normal state, wherein periodically between the normal state and the test state is changed. A method according to claim 11, characterized in that in one period the duration of the test condition is less than the duration of the normal condition, preferably less than one tenth of the duration of the normal condition. Method according to one of claims 9 to 12, characterized in that the first and the second distance value ( 52 . 74 ) and the safety function is triggered as a function of the averaged distance value.

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