LIGHT GRID ARRANGEMENT

Description

[0001] The invention relates to a light grid arrangement according to claim 1.

[0002] Relative movement of light transmitters and receivers occurs, for example, in light barrier systems attached to revolving, swinging, or sliding doors, or to moving machine parts. These light barrier systems are used, for instance, to detect people or objects. Compared to fixed light barrier systems, moving light transmitters and receivers require special considerations.

[0003] Changing the angle and distance between light sources and receivers can alter the strength of the received signals emitted by the receivers in an unobstructed monitoring area by several orders of magnitude. The causes for this change in received signal strength are, on the one hand, the spatial intensity distribution (beam shape) of the light sources and, on the other hand, the irradiance, which decreases with the square of the distance according to the inverse square law.

[0004] The large dynamic range of the received signal strength caused by relative movement complicates the evaluation of the received signals. For example, excessively high signal strength overloads the receiver, while excessively low signal strength leads to interference such as noise from the evaluation circuitry, impairing the signal strength assessment. Furthermore, object detection involves comparing the received signals emitted by the light receivers with a switching threshold. This switching threshold is typically defined as a specific portion of the signal strength present in an unobstructed monitoring area. Since this reference value can change by several orders of magnitude in moving light barrier arrangements, as described above, it is difficult to dynamically adjust the switching threshold to the position-dependent received signal strength without knowledge of the movement state, thus ensuring reliable obstacle detection.

[0005] A known cause of malfunctions in photoelectric sensors is reflection, i.e., an indirect light path from the light source to the light receiver via a reflective object. The reflected signal is stronger, making it impossible to determine from the received signal whether an object is within the detection range of the photoelectric sensor. A known method for reducing reflection and increasing the received signal strength is the use of narrow-beam optics, as described, for example, in DIN EN 61496. However, such optics are not applicable when there is a rotational component to the movement. In this case, the light sources and receivers must have a wide-angle design to cover the angular range determined by the movement. Wide-angle light sources and receivers result in lower received signal strengths and therefore shorter detection ranges.

[0006] Furthermore, the transmitting and receiving light beams of conventional light transmitters and receivers have a circular cross-section; as a result, an unnecessarily large solid angle is illuminated or captured. This also reduces the useful signal, increases the risk of receiving foreign interference, and creates a large area susceptible to reflections.

[0007] A light barrier arrangement of the type described above, known from US Patent 6,167,991 B1, serves as a safety device for elevator doors. Several light transmitters and receivers are arranged on the end faces of the doors of an elevator door system. The distance between the light transmitters and receivers is determined based on the distance-dependent illumination of the light receivers. When the elevator doors close, the three-dimensional detection zone for occupant detection is reduced. Simultaneously, the transmission power and / or the signal weighting are changed.

[0008] US Patent 5,886,307 A describes a light curtain arrangement as a safety device for elevator doors, in which the light intensity also decreases as the doors close. This arrangement is used in sliding doors.

[0009] A control system for an automatic swing door system according to US 4,669,218 A incorporates a number of light transmitters and light receivers. As the door moves through its various angled positions, the appropriate light transmitters and transmission energies are selected to achieve the desired personnel monitoring area.

[0010] For monitoring automatic swing doors, it is further disclosed in US Patent 4,467,251 A to use light emitters with diverging light beams and correspondingly wide-angle light receivers. Relatively strong signals are detected by multiple light receivers when objects or people are relatively close. It is described how the light emitters are driven with periodic pulses to cover the monitored area with modulated monitoring signals.

[0011] Light grids for contactless door monitoring in buses and trains are known, for example, from DE 10 2010 005 132 B3. In a design according to EP 2 589 991 A2, the light grid strip is integrated into the door sealing profile. The entry area is monitored with a combination of parallel and crossed light beams. Even the interruption of a single light beam triggers a switching impulse that leads to the door being held open or reversed.

[0012] US 5,698,824 A relates to an elevator device for controlling the movement of sliding doors of an elevator car or elevator car, and US 4,794,248 A relates to a detection system for controlling two opposing sliding doors.

[0013] US 5 057 695 A relates to a method and apparatus for measuring the internal properties of a substance by means of light scattering.

[0014] EP 2 492 714 A1 relates to a method for operating a safety light curtain. The method comprises: emitting light beams from light emitters of a first and / or second optical unit.Receiving light beams with light receivers of the second and / or first optical unit and generating received signals, wherein a light transmitter is assigned opposite a light receiver, so that the light beams of such formed pairs of light transmitters and light receivers form a protective field; evaluating the amplitudes of all received signals and outputting the safety switching signal if, due to an impermissible object interference, at least one of the amplitudes lies within a certain range, wherein a light beam between light transmitters and light receivers is considered interrupted if received light falls below a first lower switching threshold and the safety switching signal can be output if at least one light beam is interrupted, wherein a second lower switching threshold is provided in the evaluation unit, which lies above the first lower switching threshold, the exceeding of which indicates a clear protective field.

[0015] DE 10 2006 053708 A1 relates to a revolving door with two opposing, concentric and partially cylindrical drum walls, with several door leaves rotating around the central axis, and with a floor and ceiling, and has a sensor system with light barriers which detects whether there are objects in the area of ​​the inner surfaces of the revolving door.

[0016] Inward-swinging doors on buses undergo a 90° swing and simultaneously experience a movement with a translational component. Due to the stronger signal closer to the door, a false alarm can occur if someone is standing in the outer beam area. Even with adjustments to the transmit power and receive sensitivity, detection errors can still occur because this application places particularly high demands on adaptation due to the specific movement pattern that the light transmitters and receivers undergo together with their support structure, in this case, the inward-swinging door.

[0017] The invention is based on the objective of creating a light grid arrangement that enables reliable detection of persons and objects in the monitored area and is suitable for use with inward swing doors of buses or folding doors in buses and trains.

[0018] This problem is solved by the invention in a light grid arrangement with the features of claim 1. Advantageous further developments of the light grid arrangement according to the invention are the subject of the dependent claims.

[0019] A light grid arrangement thus comprises one or more light emitters and one or more light receivers, wherein the light emitters and light receivers are mounted on supports, one of which is fixed and the other is rotatably movable; the supports can be the doors themselves. Based on the respective distance between the light emitter(s) and light receiver(s), the transmitted energy and the signal weighting are changed. Specifically, the component of the beam intensity directed towards the light receivers and / or the beam shape of the light emitters and / or the sensitivity and / or the receiving lobe of the light receivers are adjusted depending on the relative position of the supports and the distance between the light emitters and light receivers.

[0020] In the light grid arrangement, the intensity of the light emitters and / or the sensitivity of the light receivers, including signal weighting, are selected based on the state of movement or the respective carrier position. This ensures that a lower intensity and / or sensitivity is assigned to a state of movement with a small distance between light emitters and receivers than to a state of movement (i.e., carrier position) with a large distance between light emitters and receivers. The beam shape of the light emitters and receivers is a key factor in this distance adjustment.By adjusting the intensity of the light emitters, the sensitivity of the light receivers, and the signal weighting, as well as the beam shape of the light emitters and receivers, to the distance between them, fluctuations in the strength of the received signals can be reduced, and signal path overload or interference from extraneous signals and noise can be avoided. Balanced signal weighting improves the intended detection of objects.

[0021] Separate light sources and / or receivers can be assigned to sub-areas of the angular range to be covered by the transmitter and / or receiver. Dividing the angular range to be covered by the transmitter and / or receiver into separate light sources and / or receivers allows for a narrower beam shape across the angular range and, as a result of the tighter focusing, a higher beam intensity from the light sources and / or a higher sensitivity from the light receivers. A further advantage of this division and focusing is the reduction in the number and intensity of reflection paths.

[0022] The beam shape of the light transmitters and receivers offers a particularly simple way to adjust signal strength and sensitivity to the transmission and reception angles, respectively, which depend on the state of motion. Advantages of such optical adjustment include the long range achieved through optical focusing and the direct dependence on the state of motion without the need for electrical determination of that state, thus enabling a cost-effective design.

[0023] In one embodiment of the light grid system, the beam shape of the receivers is adjusted according to changes in the beam intensity and shape of the light emitters. This can be achieved, for example, by providing adjustable or variable-angle light-guiding elements for the light emitters and / or the light receivers. For instance, adjustable lenses or mirrors can be used to change the beam shape during movement of the light emitters or light receivers.

[0024] The intensity of the light emitters and / or the sensitivity of the light receivers, which depend on the state of motion, can be controlled, at least partially, by beam-shaping elements. One embodiment uses mechanical apertures that track the movement. In this way, a dynamic change in beam direction and beam angle is possible.

[0025] In addition to optical adjustment for motion, transmitter and receiver elements can also be used that do not compensate for the distance-dependent signal strength change optically, or only partially, and that adjust for motion at least partially electrically. Electrical control is possible via the drive power of the transmitters and / or the amplification and evaluation of the receiver signals. The amplification of the electrical signals emitted by the light receivers and the evaluation of these signals must be considered as a unit: In terms of their effect on the evaluation of the light signals received by the light receiver, an increase in electrical amplification is equivalent to a corresponding reduction in the reference quantity used for evaluation.

[0026] The intensity of the light emitters can be controlled, at least partially, by varying their drive power and / or the receiver sensitivity, and at least partially by varying the gain of the received signals and / or the switching threshold depending on the state of movement. For electrical tracking by adjusting the drive power, the receiver sensitivity, or the selection of partial angular ranges associated with the light paths, the evaluation circuit requires information about the state of movement. This information can be supplied from outside the light barrier arrangement, for example, by the control system for the drive of the moving parts or by position sensors. Alternatively, determination within the light barrier arrangement is possible by evaluating the received signals of the individual light paths.A particularly advantageous embodiment uses inertial sensors for the reliable determination of the motion state, independent of obstacles in the monitoring area. These sensors can be arranged either inside or outside the housing components of the light barrier assembly. Methods for deriving position and angle information from the raw data of inertial sensors, for example, by single or double integration of gyroscope or acceleration signals, as well as the computational combination of multiple signal sources, are generally known. For example, gyroscopes and / or magnetic field sensors can also be used to detect the motion state. The combination of the aforementioned signal sources, such as the evaluation of the received signals and inertial sensors, improves the accuracy of the motion state determination.

[0027] The tracking of light transmitters and light receivers can be position- or distance-dependent, such that the intensity of the light transmitters and / or the sensitivity of the light receivers, including signal evaluation, which depends on the state of movement, increases with increasing mutual distance between light transmitters and light receivers.

[0028] Beam-shaping optics can be integrated into the light emitters and receivers or implemented separately. A particularly advantageous design for beam-shaping elements is astigmatic optics, such as toric or cylindrical lenses, which widen the beam path in the plane perpendicular to the axis of rotation and achieve a focusing perpendicular to this plane that is desirable for high intensity and reflection resistance. Beam-shaping optics can be manufactured cost-effectively in the form of extruded profiles. Further cost savings can be achieved by designing parts of the housing or mounting as beam-shaping or light-guiding elements; for example, the aforementioned extruded profile is a hollow profile that constitutes a large part of the sensor housing. The optics can also be designed as Fresnel lenses or stepped mirrors, as well as diffractive elements, which allows for a reduced material thickness.

[0029] If the light source and receiver rotate relative to each other due to the rotation of the support, the light source and / or receiver can be mounted on movable brackets or strips to compensate for the altered radiation paths. The brackets, or even the entire strip or strip sections, can then be mechanically adjusted to achieve the required monitoring area and signal characteristics for reliable monitoring.

[0030] In one embodiment of the light grid, the light emitters consist of at least two individual emitters whose main transmitting components point in different directions and have different beam intensities, and / or the light receivers consist of at least two individual receivers whose main receiving orientations point in different directions and which have different sensitivities. That is, at least two sets of emitters and receivers are used: one for when the emitters and receivers are located close to each other, and one for when they are located further apart.In such a configuration, the light transmitters and light receivers can be designed to suit their respective areas of application (range: near or far), for example with different transmission power and reception sensitivity, and the beam shape of light transmitters and light receivers can also be selected accordingly.

[0031] It is also possible to implement the light grid arrangement in which the light emitters consist of at least two individual emitters whose main transmitting components point in different directions and have different beam intensities. The individual emitters transmit with beam intensities and beam shape adapted to the relative position of the supports and the distance between the light emitters and light receivers. This means that the light emitters are dynamically adjusted to the respective conditions, e.g., the distance to the light receivers, during the movement sequence.

[0032] Accordingly, the light receivers can also consist of at least two individual receivers whose main reception orientations point in different directions and have different sensitivities, whereby the individual receivers receive with adjusted sensitivity and reception beam depending on the relative position of the carriers and the distance between light emitters and light receivers. The light receivers are thus dynamically adapted to the respective conditions, e.g., the distance to the light emitters, during the movement sequence.

[0033] It can also be provided that the individual transmitters and receivers transmit and receive, or are switched off, depending on the relative position of the carriers and the distance between light transmitters and receivers. For example, light transmitters and receivers intended for short-range operation are only operated in the short range and, if necessary, in its immediate vicinity to create an overlap with the next light transmitter or receiver, and light transmitters and receivers intended for long-range operation are only operated in the long range and, if necessary, in its immediate vicinity to create an overlap with the next light transmitter or receiver. Intermediate areas can be covered accordingly with light transmitters and receivers that are then switched on.

[0034] Alternatively, depending on the state of movement, i.e., the relative position or distance between the light emitters and light receivers, different subsets of the light paths between light emitters and light receivers can be evaluated for object detection.

[0035] The light emitters can have a wide-angle to spherical radiation pattern, and the light receivers a wide-angle to spherical receiving lobe.

[0036] Depending on the requirements and operating conditions, different combinations of optical and electrical alignment, as well as division into separate angular ranges, are advantageous. Predominantly optical alignment enables long ranges, but the focusing of the light into specific areas can lead to adverse reflections. With predominantly electrical alignment and a wide swivel angle, the low signal intensity or sensitivity of wide-angle light transmitters or receivers limits the achievable range. Division into separate angular ranges allows for long ranges while avoiding reflection problems, but requires more transmitter and / or receiver elements than the aforementioned options.

[0037] In applications involving translational motion or motion with a translational component, it may be possible to evaluate light paths with a beam component perpendicular to the translational direction of motion, where the light source and receiver are offset relative to each other. Optical adaptation to relative motion is also possible and advantageous in predominantly translational relative motions with only a small or no rotational component, as described in the disclosure. In translational motions, an angular change between the light axis and the light source and / or receiver can be achieved by offsetting the light source and receiver relative to each other perpendicular to the direction of motion. This offset results in a larger angular deviation at short distances than at long distances.

[0038] To avoid false signals, it can be provided, for example, that the light transmitters send pulsed and / or coded signals, with the light receivers being designed accordingly.

[0039] The following are examples of implementation. This description serves only for illustrative purposes and is not intended to limit the disclosure to the specifically stated combinations of features. They show Fig. 1 : a schematic top view of a double-leaf inward swing door, equipped with a light grid, in the closed position, Fig. 2 : a schematic top view of a double-leaf inward swing door, equipped with a light grid, in the open position, Fig. 3 : a schematic top view of a leaf of an inward swing door, which is equipped with a light grid with light emitters of different beam shapes, Fig. 4: a schematic top view of a double-leaf inward swing door, illustrating different positions of the door leaves, Fig. 5 : a schematic sectional view of the profile strip of a double-leaf inward swing door, which is provided with a light grid, wherein the profile strip, the light grid strip and the light beam are shown for different positions of the door leaves, Fig. 6 and Fig. 7 : schematic sectional views of the profile strip of a double-leaf inward swing door equipped with a light grid, with one fixed door leaf, showing the profile strip, the light grid strip and the light beam for different positions of the door leaves, Figs. 8 to 10 : schematic top views of a double-leaf inward swing door, equipped with a light grid with light emitters of different beam shapes, in three positions, Figs. 11 to 13Schematic side views of movable door leaves with a translational component, equipped with a light grid, showing the light rays used for evaluation. The embodiments of the Figs. 11 to 13 are not part of the invention.

[0040] Fig. 4 schematically shows the movement sequence and the different positions of the wings of inward-swinging doors, which are used, for example, in public buses.

[0041] Fig. 5 schematically shows a profile strip 32 of a double-leaf inward swing door, which is equipped with a

[0042] The light grid is provided for various door leaf positions. The light grid strip 34, mounted in the profile strip, is shown; furthermore, the currently evaluable light beam 36 between the two door leaves is shown, as well as the light transmitter 1 and light receiver 2 of the light grid.

[0043] Figs. 6 and 7This is shown analogously for the case where only one door leaf is operated, i.e., closed, and the other door leaf remains in the open position.

[0044] The following will be discussed Fig. 1 and Fig. 2 Reference is made to these figures. These show a double-leaf swing door in a top view of the swing axes 4 with the door leaves 3, transmitter unit 1, receiver unit 2 and the beam intensity distribution 5 of the light emitters, shown as an example polar diagram. In Fig. 1 The swing door is closed and the distance between transmitter 1 and receiver 2 is very small. The component of the beam intensity 5 from transmitter 1 pointing towards receiver 2 is correspondingly low. Fig. 2The swing door is shown in the open position. In this position, the distance between transmitter 1 and receiver 2 is large, and the beam intensity 5 from transmitter 1 towards receiver 2 is also high. With a beam shape equivalent to that of the transmitters, the distance and angle-dependent conversion efficiency of the light emitters and receivers largely cancel each other out, and the received signals emitted by the receivers remain largely constant throughout the swinging movement of the door. For clarity, the beam shape of the receivers is not shown in the drawing.

[0045] One disadvantage of the in Fig. 1The beamform shown in 5 with the door closed is characterized by a high proportion of power radiated perpendicular to the door leaves 3, or receiver sensitivity, which means that objects located in this direction, such as item 10, pose a high risk of reflection. This optical solution is therefore only practical if such a risk of reflection is either absent or can be tolerated.

[0046] To reduce the in Fig. 1 In the described reflection problem, while maintaining or even increasing the range, it is particularly advantageous to divide the angular range required by the movement into several sub-ranges, which are assigned to separate transmitter and receiver elements. This is shown in Fig. 3For a door leaf 3 of a swing door, the following is described: Individual or partial transmitters or receivers with beam shape 5a cover the area of ​​the small door opening, whereby light paths assigned to individual or partial transmitters or receivers with beam shape 5b are not used for object detection and therefore do not cause any reflection problems. Partial transmitters or receivers with beam shape 5b cover the area of ​​the large door opening.

[0047] A variant that provides separate light transmitters and light receivers for sub-areas of the angle, but operates them in parallel instead of evaluating them separately, is conceivable and advantageous in order to cover a particularly large angular range.

[0048] Fig. 8 to 10 illustrate the relationships of the monitoring area resulting from the different beam shapes and door positions. Fig. 8 shows analogously Fig. 1A top view of a double-leaf inward-swinging door equipped with a light grid, in the closed position. Light transmitters and receivers with beam shape 5a are used for monitoring near the closed position. Light transmitters and receivers with beam shape 5b are either not activated or the received signals are not used for evaluation. Fig. 9 The figure shows the overlap area of ​​beam shapes 5a and 5b. With the door in this semi-open position, the conditions are such that preferably the light transmitter and light receiver of both beam shapes 5a and 5b are actively switched on and their signals are used. Fig. 10 This illustrates the situation when the door is fully open. Only beam pattern 5b allows monitoring of the area between the door leaves.

[0049] Similar movement patterns to those of inward-swinging doors can be found, for example, in folding doors, which are often used in buses and trains. To avoid repetition, these will not be described again for folding doors. Parts of these movement patterns can also be found in other door types, such as swing-sliding doors.

[0050] Fig. 11 Figure 1 shows a light grid mounted on a sliding door without a rotary motion component. The transmitter unit 1 with the light transmitters 6 is mounted at a different height than the receiver unit 2 with the light receivers 7, resulting in an angular offset that varies with the opening width. This variable angle enables the previously described method of optically adjusting the signal strength and sensitivity to the state of movement.

[0051] It is known that in light grids, in addition to the "straight" beam paths between light emitters and light receivers with the same atomic number, beam paths can also be used that run "obliquely," i.e., from light emitter n to light receiver n+k and / or nk with k>0. In the aforementioned case of predominantly translational movement, an advantageous design feature for light grids is that, in the region of small distances between light emitters and light receivers, the "straight" beam paths, which would then lead to overload, are no longer used, but only the beam paths to the opposite elements at positions n+1 and / or n-1, or even more significantly offset combinations. This arrangement is shown. Fig. 12 and Fig. 13 In the case of overload, the "straight" light paths are no longer used; instead, only the beam paths to the opposite elements at positions n+1 and / or n-1, or even more strongly offset combinations, are used. This arrangement is shown. Fig. 12 and Fig. 13. As opposed to Fig. 11 The light grids are mounted at the same height here; for this purpose, the following are used in the Fig. 12 Due to the small aperture shown, only "oblique" rays 9 were evaluated, whereas in the Fig. 6 The large aperture shown also allows for the evaluation of "straight" rays 8. The methods for determining the state of motion do not differ from those used in the case of rotational movements.

[0052] All specifications also apply to applications where only one side of the light grid arrangement is movable and the other side is fixed.

[0053] For the sake of simplicity, the explanations and drawings are limited to light grids where one side contains only light emitters and the other side only light receivers. The principles mentioned can also be applied to light grids where both emitter and receiver elements are arranged in a single housing, meaning that the beam direction alternates.

[0054] The evaluation circuit is not shown in the figures for the sake of simplicity; it may be located wholly or partially within the housing containing the light transmitters and / or light receivers, or in a separate housing.

Claims

1. A light grid arrangement, comprising: one or more light transmitters (1) and one or more light receivers (2), wherein the light transmitters (1) and light receivers (2) are mounted on supports, one of which is fixedly mounted and the other is rotatably movable, wherein the transmission energy and the signal evaluation are changed, based on the respective distance between the light transmitter(s) (1) and the light receiver(s) (2), wherein the component of the beam intensity in the direction of the light receivers (2) and / or the beam shape of the light transmitters (1) and / or the sensitivity and / or the reception lobe of the light receivers (2) is adapted, depending on the relative position of the supports and the distance between light transmitters (1) and light receivers (2).

2. The light grid arrangement according to claim 1, wherein the beam shape of the receivers (2) is adjusted according to the changes in the beam intensity and beam shape of the light transmitters (1).

3. The light grid arrangement according to claim 1 or 2, wherein the light transmitters (1) and / or light receivers (2) are mounted on movable holders or strips.

4. The light grid arrangement according to claim 1 or 2, wherein tuneable or adjustable light guide elements are provided for the light transmitters and / or light receivers.

5. The light grid arrangement according to any one of claims 1 to 4, wherein the light transmitters (1) consist of at least two individual transmitters, the main transmission components of which point in different directions and have different beam intensities, and / or wherein the light receivers (2) consist of at least two individual receivers, the main reception orientations of which point in different directions and have different sensitivities.

6. The light grid arrangement according to any one of claims 1 to 4, wherein the light transmitters (1) consist of at least two individual transmitters, the main transmission components of which point in different directions and have different beam intensities, wherein the individual transmitters transmit with an adapted beam intensity and beam shape, depending on the relative position of the supports and the distance between the light transmitters and the light receivers (2).

7. The light grid arrangement according to any one of claims 1 to 4, wherein the light receivers (2) consist of at least two individual receivers, the main reception orientations of which point in different directions and have different sensitivities, wherein the individual receivers receive with an adapted sensitivity and reception lobe, depending on the relative position of the supports and the distance between the light transmitters (1) and the light receivers (2).

8. The light grid arrangement according to any one of claims 5 to 7, wherein the individual transmitters and the individual receivers transmit and receive or are switched to inactive depending on the relative position of the supports and the distance between the light transmitters (1) and the light receivers (2).

9. The light grid arrangement according to any one of claims 1 to 8, wherein the light transmitters have a spherical or wide-angle radiation characteristic and the light receivers have a spherical or wide-angle reception lobe.

10. The light grid arrangement according to claim 3, wherein parts of a housing or the holder are configured as light-guiding elements.

11. The light grid arrangement according to any one of claims 1 to 10, wherein the light emitters emit in a pulsed manner.

12. The light grid arrangement according to any one of claims 1 to 11, wherein the light emitters emit in a coded manner.