SENSOR DEVICE AND ALIGNMENT METHOD

Abstract

A sensor device (10) comprising a housing (48a-b), a position sensor (44) for determining an alignment, a display unit (46a-d) for displaying alignment information, and a control and evaluation unit (40) configured to use the position sensor (44) to determine the sensor device's (10) alignment, to compare the alignment with a desired alignment, and to display a comparison result using the display unit (46a-d), wherein the display unit (46a-d) comprises at least three light sources (46a-d) at positions distributed over the housing (48a-b), each light source (46a-d) being configured to assume a first display state for a correct alignment and a second display state for an alignment that is not yet correct, with the control and evaluation unit (40) further being configured to display the comparison result as display states of the light sources (46a-d).

Claims

1. A sensor device (10) comprising a housing (48a-b), a position sensor (44) for determining an alignment, a display unit (46a-d) for displaying alignment information, and a control and evaluation unit (40) configured to use the position sensor (44) to determine the sensor device's (10) alignment, to compare the alignment with a desired alignment, and to display a comparison result using the display unit (46a-d), wherein the display unit (46a-d) comprises at least three light sources (46a-d) at positions distributed over the housing (48a-b), each light source (46a-d) being configured to assume a first display state for a correct alignment and a second display state for an alignment that is not yet correct, with the control and evaluation unit (40) further being configured to display the comparison result as display states of the light sources (46a-d).

2. The sensor device (10) according to claim 1, the sensor device (10) being configured as at least one of a laser scanner and a radar sensor.

3. The sensor device (10) according to claim 1, wherein the display states relate to an axis represented by the position of the displaying light source (46a-d).

4. The sensor device (10) according to claim 1, wherein the light sources (46a-d) are configured to assume three display states, and wherein the control and evaluation unit (40) is configured to display, at a light source (46a-d), the second display state when the alignment is too low and a third display state when the alignment is too high.

5. The sensor device (10) according to claim 1, wherein the light sources (46a-d) are configured to assume display states as different colors.

6. The sensor device (10) according to claim 1, wherein the light sources (46a-d) are configured as multicolor LEDs.

7. The sensor device (10) according to claim 1, wherein the housing (48a-b) comprises a quadrangular cross-sectional area and the light sources (46a-d) are arranged in corners.

8. The sensor device (10) according to claim 7, wherein four light sources (46a-d) are arranged in four corners.

9. The sensor device (10) according to claim 1, comprising an interface (42) for specifying the desired alignment.

10. The sensor device (10) according to claim 1, which is configured as a laser scanner having at least one scanning plane (50) and at least one light transmitter (22) for transmitting transmitted light (26), a movable deflection unit (12) for periodically deflecting the transmitted light (26), and a light receiver (32) for receiving remitted light (28) remitted by objects in the scanning plane (50), the control and evaluation unit (40) being configured to measure distances on the basis of a light time of flight of the transmitted light and the remitted light (26, 28).

11. The sensor device (10) according to claim 10, wherein the position sensor (44) is calibrated with respect to a scanning plane (50).

12. An alignment method for a sensor (10), wherein an actual alignment of the sensor (10) is determined by means of a position sensor (44), the actual alignment is compared with a desired alignment, and a comparison result is displayed, wherein the comparison result is displayed by three light sources (46a-d) arranged at positions distributed over the sensor (10), each of the light sources assuming a first display state for a correct position or a second display state for an alignment that is not yet correct.

13. The alignment method according to claim 12, wherein the sensor (10) comprises a housing (48a-b), the position sensor (44), a display unit (46a-d) having the light sources (46a-b), and a control and evaluation unit (40) configured to execute the method steps.

14. The alignment method according to claim 12, wherein the sensor (10) is configured as a laser scanner having at least one scanning plane (50) that is periodically scanned by a scanning beam (26, 28), wherein the position sensor (44) is calibrated in advance with respect to the scanning plane (50) by guiding the scanning beam (26, 28) to a cooperative target and taking an image of the target and evaluating the image to determine the alignment of the scanning plane (50).

15. The alignment method according to claim 14, wherein the image is taken with an IR camera.

Description

[0033] The invention will be explained in the following also with respect to further advantages and features with reference to exemplary embodiments and the enclosed drawing. The Figures of the drawing show in:

[0034] FIG. 1 a sectional view of a laser scanner;

[0035] FIG. 2a-b a schematic representation of a laser scanner in a desired alignment and with corresponding indication of the correct alignment by several LEDs as a top view or front view;

[0036] FIG. 3a-b a schematic representation according to FIG. 2a-b with a tilt, in this example about a roll angle; and

[0037] FIG. 4a-b a schematic representation corresponding to FIG. 2a-b with another tilt, now about both roll angle and pitch angle.

[0038] FIG. 1 shows a schematic sectional view of an optoelectronic sensor 10 in an embodiment as a multi-layer laser scanner. The alignment according to the invention is particularly advantageous for that kind of laser scanner. However, it is also suitable for a laser scanner having only one scanning plane. Other optoelectronic sensors that operate without periodic scanning motion are also conceivable. Non-optical sensors are possible, in particular a radar whose mode of operation is similar to a laser scanner, in a different range of the electromagnetic spectrum.

[0039] The sensor 10 comprises, in a rough description, a movable deflection unit 12 and a base unit 14. The deflection unit 12 is an optical measuring head, while the base unit 14 accommodates further elements such as a supply, evaluation electronics, connections, and the like. During operation, a drive 16 of the base unit 14 causes the deflection unit 12 to move about an axis of rotation 18 in order to periodically scan a monitoring area 20.

[0040] In the deflection unit 12, a light transmitter 22 having a plurality of light sources 22a, for example LEDs or lasers in the form of edge emitters or VCSELs, generates a plurality of transmitted light beams 26 using a common transmitter optics 24, and the transmitted light beams 26 are transmitted into the monitoring area 20. In the example shown, there are five transmitted light beams 26 for five scanning planes; there may be more, including significantly more, and there may be fewer transmitted light beams 26. Individual optics are possible instead of a common transmitting optics 24. The plurality of transmitted light beams 26 may also be formed by splitting the light from one or more light sources using a beam splitting element, a diffractive optical element, or the like. In a further embodiment, illumination is provided over a wide area or with a line of light, and the transmitted light is divided into scanning beams at the receiving end.

[0041] When the transmitted light beams 26 impinge on an object in the monitoring area 20, corresponding remitted light beams 28 return to the sensor 10. The remitted light beams 28 are guided by a common receiving optics 30 to a light receiver 32 having a plurality of light receiving elements 32a, each of which generates an electrical received signal. The light receiving elements 32a may be separate components or pixels of an integrated matrix array, for example photodiodes, APDs (avalanche diodes) or SPADs (single photon avalanche diodes). The remarks on the transmitting side apply to the receiving side mutatis mutandis. A plurality individual optics may be provided, and a plurality of scanning beams may be detected on a common light-receiving element.

[0042] In this embodiment, light transmitter 22 and light receiver 32 are arranged together on a circuit board 34, which lies on the axis of rotation 18 and is connected to the shaft 36 of the drive 16. This is to be understood only as an example, virtually any number and arrangement of circuit boards are conceivable. The basic optical design with light transmitter 22 and light receiver 32 in a biaxial arrangement side by side is optional and can be replaced by any design known per se from single-beam optoelectronic sensors or laser scanners. An example is a coaxial arrangement with or without beam splitter.

[0043] A contactless supply and data interface 38 connects the movable deflection unit 12 to the stationary base unit 14, where a control and evaluation unit 40 is located. The control and evaluation unit can also be accommodated at least partially on the circuit board 34 or at another location in the deflection unit 12. In particular, it is conceivable to accommodate part of the evaluation already in the light receiver 32, for example by means of an ASIC design (Application-Specific Integrated Circuit), with individual cells directly performing evaluation and other processing. The control and evaluation unit 40 controls the light transmitter 22 and receives the received signals from the light receiver 32 for further evaluation. It also controls the drive 16 and receives the signal from an angle measuring unit, not shown, that is generally known from laser scanners and that determines the respective angular position of the deflection unit 12.

[0044] For evaluation, the distance to a scanned object is measured. Together with the information about the angular position from the angle measuring unit, two-dimensional polar coordinates of all object points in a scanning plane are available after each scanning period in the form of angle and distance. The respective scanning plane, if there is a plurality of scanning planes, is also known via the identity of the respective scanning beam 26, 28, so that a three-dimensional spatial area is scanned in total.

[0045] This means that the object positions or object contours are known and can be output via a sensor interface 42. Conversely, the sensor interface 42 or a further connection, not shown, may be used as a parameterization interface. The sensor 10 can also be configured as a safety sensor for use in safety applications for monitoring a source of danger, as briefly explained in the introduction.

[0046] The sensor 10 shown in FIG. 1 is a laser scanner having a rotating measuring head, namely the deflection unit 12. Alternatively, a periodic deflection by means of a rotating mirror or a facetted mirror wheel is also conceivable. Another alternative embodiment pivots the deflection unit 12 back and forth, either instead of the rotary motion or additionally about a second axis perpendicular to the rotary motion, in order to generate an additional scanning motion in elevation. Furthermore, the scanning motion to generate the scanning plane may instead be generated using other known methods, such as MEMS mirrors, optical phased arrays, or acousto-optic modulators.

[0047] During the movement of the deflection unit 12, a plane is scanned per each of the transmitted light beams 26. Only at a deflection angle of 0°, the middle one of the transmitted light beams 26 shown in FIG. 1, is an actual scanning plane of the monitored area 20 scanned. The other transmitted light beams 26 scan the lateral surface of a cone, which has a different cone angle depending on the deflection angle. If a plurality of transmitted light beams 26 are deflected upwards and downwards at different angles, a kind of nesting of several hourglasses is created as a scanning structure. These surfaces are also referred to as scanning planes for simplicity.

[0048] In a practical application, the sensor 10 must be mounted with correct alignment or orientation. To that end, a position sensor 44 is provided, which can be configured as an IMU (Inertial Measurement Unit). The respective alignment information of the position sensor 44 is read in by the control and evaluation unit 40. At least three light sources 46a-b or LEDs are distributed over the sensor 10, where only two of the light sources 46a-b can be seen in the sectional view of FIG. 1. The light sources 46a-b preferably are as far apart as possible and arranged in a common plane. They are controlled by the control and evaluation unit 40 to indicate whether a desired alignment has been achieved or what deviation exists between the actual alignment according to the position sensor 44 and the desired alignment.

[0049] FIGS. 2a-b show the sensor 10 in a schematic view without its individual elements, where FIG. 2a is a top view and FIG. 2b is a front view. Only a housing with an upper housing part 48a and a lower housing part 48b as well as the light sources 46a-d are shown. The two housing portions 48a-b may correspond to the deflection unit 12 and the base unit 14, but there may also be a transition region where this correspondence does not apply. The upper housing part 48a is at least partially transparent to allow the scanning beams 26, 28 to pass through, and is also referred to as a hood or front window. In FIG. 2b, the single or central scanning plane 50 at elevation 0° is shown with a dashed line for illustration.

[0050] In this embodiment, four light sources 46a-d instead of the minimum number of three light sources are used. They are located at the corners of the square or rectangular cross-section at the top of the lower housing part 48b and thus at the greatest possible distance from each other and in a same plane.

[0051] In FIGS. 2a-b, the desired alignment is a horizontal orientation of the scanning plane 50 and thus an upright position of the sensor 10. This can also be expressed in that the pitch and roll angles should be 0°. Both can be measured by the position sensor 44 with respect to the direction of gravity, but the yaw angle cannot be measured in this orientation of the sensor 10. The yaw angle corresponds to the respective angle of rotation of the deflection unit 12, and its origin can be specified independent of the orientation of the sensor 10 in the field or, for example, can be specified by the user as in EP 2 937 715 B1 mentioned in the introduction. As an alternative to the horizontal plane as the desired alignment, a different roll and pitch angle can be specified via the sensor interface 42 or an optional control element (not shown). With an inclined orientation, the angles that can be measured by the position sensor 44 change and, in particular, the yaw angle can also be measured and displayed.

[0052] The light sources 46a-d can be controlled by the control and evaluation unit 40 with distinguishable light signals. Preferably, the light sources 46a-d are multicolor, in particular multicolor or RGB LEDs. The display of the alignment is described using different colors as an example. This is a particularly intuitive and easily understood display option. However, a different brightness or sequence of a flashing signal would also be conceivable. Multiple display modalities can also be combined, for example in that rapid flashing in a particular color signifies a strong deviation in a direction coded by the color. The different signals of the light sources 46a-d are used as a display.

[0053] The sensor 10 can be set to a corresponding alignment mode for alignment, which is started via the sensor interface 42 or a button on the sensor 10. Outside the alignment mode, the light sources 46a-d preferably are inactive or used for other purposes. For an alignment, the control and evaluation unit 40 performs a comparison, for example cyclically repeated, between the actual alignment detected by the position sensor 44 and the desired alignment that is fixed or specified by the user. At the light sources 46a-d, the control and evaluation unit 40 provides light signals as to whether or not the desired alignment has been achieved on the corresponding axis. Advantageously, the indication for an alignment that is not correct is further differentiated according to the direction. In a specific example, a green indication represents a correct alignment, blue represents too low, and red represents too high. These specific colors can be changed as long as the user knows the meaning. For finer gradations, additional modalities such as brightness can be added to represent the extent of the deviation.

[0054] In the example of FIG. 2a-b, the sensor already is correctly aligned in a horizontal plane. All four light sources 46a-d therefore display the same color, for example green, which represents correct alignment.

[0055] FIGS. 3a-b show another example where the sensor 10 is tilted in roll angle. The definition of roll angle is a convention, chosen in this case so that the roll angle is measured in one vertical plane of symmetry and the pitch angle is measured in the other vertical plane of symmetry. The light sources 46a,d on the left side light up blue, those on the right side light up red, and it is thus indicated that the sensor 10 needs to be raised on the left relative to the right, or conversely lowered on the right relative to the left.

[0056] FIG. 4a-b show another example where the sensor 10 now is tilted in roll angle and pitch angle. Note that in FIG. 4b, the illustration is rotated 90° out of the drawing plane compared to FIGS. 2b and 3b. Since the sensor 10 in this example is tilted with respect to the diagonal to the base plane, the light sources 46b,d show green, since on this axis the alignment is already correct. On the opposite diagonal, corrections need to be made by raising the sensor on the left relative to the right or, conversely, lowering the sensor on the right relative to the left. Thus, in this specific example, roll and pitch angles can be corrected at the same time. In general, the sensor 10 would have different roll and pitch angles, and for this purpose the light sources 46b,d would also light up red and blue, respectively.

[0057] Depending on the shape and size of the sensor 10, the positions and number of light sources 46a-d can be varied, as long as there are more than three light sources that are not arranged collinearly and thus define a plane in space. The display can also be acoustically supported.

[0058] The position sensor 44 is preferably calibrated when shipped from the factory. The calibration does not necessarily have to be performed with reference to a surface of the housing 48a-b. For a laser scanner, the scanning plane is often the better reference since this is where the measured values are acquired. Due to tolerances, it is not guaranteed that the scanning plane is parallel to a housing surface.

[0059] Calibration can be accomplished, for example, by first calibrating the position sensor 44 to one or more known orientations of the laser scanner during manufacturing. The scanning plane is then measured with respect to one of these orientations. One practical way to do this is to place a white target in the scanning plane and, while the laser scanner is scanning, capture an image of that target with an IR camera. In the camera image, the laser scan line can be seen on the target, and image processing algorithms can be used to determine its position as an angle. This can be used to calculate a correction value that references the measurement data from the position sensor 44 to the scanning plane rather than to the housing 48a-b.