Method for determining the position of a spotlight and calibrating same

Abstract

A method for determining the position of a spotlight (1) which is arranged above an underlying surface (3) and creates an illuminated region (5) on the underlying surface (3), wherein a light sensor (2) is arranged on the underlying surface (3), wherein the light sensor (2) is designed as a camera, wherein the camera comprises a wide-angle lens, preferably a fisheye lens, and wherein the light sensor (2) comprises one to three position sensors, preferably ultra-wideband position sensors (8), which are designed to determine the position of the light sensor (2) in a three-dimensional coordinate system, wherein the camera creates a recording of the spotlight (1), and wherein the position of the spotlight (1) is at least approximately determined from the recording and the position of the light sensor (2).

Description

[0001] Method for determining the position and calibrating a headlight

[0002] The invention relates to a method for determining the position and calibrating a headlight.

[0003] Spotlights are known, particularly for the lighting of stages in theatre and event technology, but also for other applications, such as sporting events. These spotlights are arranged above a surface and create an illuminated, preferably elliptical area on the surface via a light cone.

[0004] In particular, so-called moving heads or head-moving spotlights are known, which are arranged so that they can rotate or pivot along two axes. These two axes are a pivot axis running parallel to the surface, usually referred to as the tilt axis, and a rotation axis running perpendicular to the surface, usually referred to as the pan axis. The spotlight can usually be rotated by up to 540° along the pan axis and pivoted by up to 270° along the tilt axis. With such spotlights, any point on the surface can be illuminated by adjusting the pan and tilt values. In order to set up spotlights for computer-assisted and preferably automatic illumination of people on the surface, the spotlights must be calibrated with regard to their position and control values.

[0005] In particular, the position of the fixture must be known in absolute coordinates. For moving-head fixtures, it is also necessary to know which control values ​​of the protocol used lead to the desired rotation of the fixture, whereby the fixture's pan and tilt values ​​must be mapped to the most commonly used DMX protocol. However, calibration presents several problems in practice.

[0006] First, the location of the spotlight in three-dimensional space (x, y, and z coordinates) must be determined. This is usually done by measuring the stage area and the position of the spotlights, and by computer-aided generation of a three-dimensional model. This is time-consuming and error-prone – it is usually not possible to measure the exact position of the spotlight correctly. Furthermore, there is a risk that the spotlight's position may change intentionally or inadvertently between the time of measurement and the time of the performance.

[0007] Furthermore, with moving-head spotlights, the relationship between the pan and tilt values ​​used to control the spotlight and the resulting changes in the light beam on the stage must be determined. In other words, it is necessary to determine which pan and tilt values ​​are required to achieve a specific shift of the light beam on the stage. This mapping specification is also usually created using the computer-generated 3D model, so the same inaccuracies can occur. A reliable assignment of the computer-generated model to the actual conditions in the stage space is not possible. Finally, the clear localization of the spotlight also requires the determination of the rotation, i.e. the direction of the light beam produced by the spotlight. Here, too, there is the problem that the computer-generated model usually does not correspond to the actual conditions.

[0008] These and other problems are solved according to the invention by a method according to the characterizing features of claim 1.

[0009] In a method according to the invention, a spotlight is arranged above a surface and creates an illuminated area there. According to the invention, the spotlight can be any lighting fixture. The spotlight can be permanently installed. However, it can also be provided that the spotlight can be rotated about a pan axis by entering pan values ​​and pivoted about a tilt axis by entering tilt values.

[0010] A light sensor is arranged on the substrate. According to the invention, the light sensor is designed as a camera with a wide-angle lens, preferably a fisheye lens. The camera preferably has a field of view of more than 100°, preferably more than 140°, and particularly preferably approximately 180°. The camera can be a conventional 2D camera or a stereo camera.

[0011] The light sensor comprises one to three position sensors, preferably ultra-wideband position sensors, which are designed to determine the position of the light sensor in a three-dimensional coordinate system. The camera and the position sensors can be wirelessly connected to a data processing unit. The headlight can also be connected to this data processing unit.

[0012] In a method according to the invention, the camera takes a recording, i.e. a photo or video, of the headlight, and a data processing unit calculates the position of the headlight at least approximately from the recording and the position of the light sensor. In the case of a movable headlight, it can be provided that the headlight is rotated and pivoted by entering tilt and pan values ​​until a pan and tilt value is reached at which the camera detects the headlight. Preferably, the camera can clearly detect a light exit point of the headlight at this position in order to be able to determine a clear position of the headlight center. The position of the headlight in the coordinate system is then at least approximately calculated from the camera recording and the location of the camera known from the position sensors.

[0013] For example, a two-dimensional position of the headlight can be determined from the image taken by a 2D camera, and then the three-dimensional position of the headlight in the coordinate system can be estimated from the estimated height of the headlight above the ground.

[0014] According to the invention, it can further be provided that the light sensor is arranged at at least two different positions on the ground. If the spotlight is movable, the spotlight can then be rotated and panned for both positions by entering tilt and pan values ​​until a pan and tilt value is reached at which the camera detects the spotlight. The camera takes a picture of the spotlight at each position. The position of the spotlight in the three-dimensional coordinate system is then calculated from the two pictures and the measured camera positions. Conventional algorithms for superimposing two pictures of a fixed point taken at different but known positions (photogrammetry) can be used to calculate the position.

[0015] According to the invention, it can further be provided that the light sensor is designed as a stereo camera with two separate and spaced-apart individual cameras, wherein the cameras each have a wide-angle lens, preferably a fisheye lens. The individual cameras are arranged at a known distance from one another, for example 10 cm to 20 cm. The cameras can have an angle of view of more than 100°, preferably more than 140°, particularly preferably approximately 180°. The distance between the individual cameras is known to the data processing unit. If it is a movable headlight, the headlight is rotated and panned by entering tilt and pan values ​​until a pan and tilt value is reached at which both cameras detect the headlight. Since a stereo camera is used, both cameras can each take a picture of the headlight simultaneously.In practice, it's often sufficient for the headlight to flash at the light sensor, as the wide aperture of the cameras usually allows both cameras to capture the headlight. Consequently, positioning can be determined very quickly and without having to move the light sensor.

[0016] Subsequently, the position of the headlight in the coordinate system is calculated from the different images taken by the two cameras, the known distance between the cameras and the position of the light sensor in the coordinate system, whereby conventional algorithms are again used to superimpose two images of a fixed point taken at different but known positions (photogrammetry).

[0017] According to the invention, when using a movable spotlight, it can be provided that an imaging specification of the spotlight is determined by moving the illuminated area over the ground by rotating and pivoting the spotlight until at least one of the cameras detects the edges of the illuminated area. This is possible both in the version with only one 2D camera and in the version with a stereo camera.

[0018] Subsequently, by rotating and / or pivoting the spotlight and repeatedly detecting the illuminated area, a mapping rule for the spotlight's pan values ​​and / or tilt values ​​to the spotlight's angular coordinates is determined. A method as described in WO 2018 / 154108 A1 can be used, in particular, to calculate the mapping rule. This method can be used to move the illuminated area across the surface by rotating and pivoting the spotlight until at least one of the two cameras detects an edge of the illuminated area, and subsequently, the dimensions and a center point of the illuminated area are determined by varying the spotlight's pan value and / or tilt value.

[0019] According to the invention, the dimensions of the illuminated area can be detected, and the aperture angle of the light cone can be determined from the calculated imaging rule. In particular, it can be assumed that the light cone is symmetrical, so that the aperture angle is identical in the pan and tilt axes.

[0020] According to the invention, it can be provided that firstly, by measuring the illuminated area along the plane spanned by the pan values, a mapping rule of the pan values ​​to absolute angular coordinates and the opening angle of the light cone along this plane is determined.

[0021] Subsequently, by measuring the illuminated area along the plane spanned by the tilt values, a mapping rule of the tilt values ​​to absolute angular coordinates can be determined.

[0022] According to the invention, in the embodiment with a stereo camera, it can be provided that the imaging rule and / or the aperture angle are determined for each of the two cameras of the light sensor. The determined imaging rules can then be compared, and if necessary, an error signal can be output in the event of deviations. It can also be provided that the mean value of the imaging rules determined by the two cameras is determined to determine an average imaging rule.

[0023] According to the invention, the method can be carried out for multiple headlights in sequential order. The invention further extends to a computer-readable storage medium comprising a computer program, for example, a smartphone app or a program on a server, which controls the execution of a method according to the invention. The computer program can control the headlight with the required pan and tilt values, receive the camera images, and calculate the target values ​​of the method.

[0024] The headlight can operate in any wavelength range, with the cameras designed to detect the signals emitted by the headlight. In particular, a wavelength range from 380 nm to 780 nm (visible light) or beyond (infrared) can be provided.

[0025] Further features of the invention emerge from the patent claims, the description of the embodiments and the drawings.

[0026] The invention is explained in more detail below using a non-exclusive embodiment.

[0027] Figs. 1 to 7 show successive method steps of an embodiment of the method according to the invention using a spotlight and a light sensor 2 arranged on the ground. In this embodiment, the light sensor is designed as a stereo camera, which comprises two individual cameras arranged at a distance of approximately 15 cm, each of which is equipped with a fisheye lens with a field of view of approximately 150°.

[0028] Fig. 1 shows a surface 3, for example, a theater stage, and a spotlight 1 mounted above the surface. A mobile light sensor 2 in the form of a stereo camera with two (schematically shown) fisheye lenses is arranged on the surface 3. The light sensor 2 is wirelessly controllable and is connected to an external processing unit. The light sensor is not permanently connected to the surface 3, but is removably placed on the surface. Furthermore, two (not shown) ultra-wideband position sensors are located on the light sensor 2, which can be used to determine the absolute position of the mobile light sensor 2 in a three-dimensional coordinate system.

[0029] The spotlight 1 can be pivoted about two axes perpendicular to one another. Along the schematically indicated pan axis 7, the spotlight can be rotated by approximately 540°. Along the schematically indicated tilt axis 8, the spotlight can be pivoted by 180°. The spotlight 1 emits a light cone 4 with a light cone axis 6, which creates an illuminated area 5 on the surface 3.

[0030] The illuminated area 5 created on the substrate 3 is generally elliptical.

[0031] By rotating the pan and tilt axes, the spotlight 1 can illuminate any point on the surface 3. The possible value range of the pan and tilt values ​​in the embodiment considered is 0 to 2 16= 65536 ticks. From a pan value of 0 to a pan value of 65536, the spotlight rotates approximately 540° around the pan axis. It can be assumed that the mapping of the pan values ​​to the angular range is linear, but the exact mapping rule for the pan values ​​to the covered angular range is unknown. The same applies to the tilt values.

[0032] In one embodiment of the invention, the light sensor 2 is first placed on the substrate 3, and then the light cone 4 is systematically moved along a predefined curve across the substrate 3 until a camera of the light sensor 2 detects the edge of the illuminated area 5. The curve along which the light cone 4 is moved is schematically indicated in Fig. 1 as a dashed line. As soon as both cameras of the stereo camera detect the illuminated area 5, the movement of the spotlight 1 stops, and the pan value p1 and tilt value t1 of this position are saved.

[0033] To determine the position of headlight 1, the two cameras of light sensor 2 each take a photo of headlight 1. From the two photos, the distance between the cameras, and the known position, the position of headlight 1 in the coordinate system is determined using photogrammetry. In an embodiment of the invention (not shown), the position is determined by a mobile light sensor with only one 2D camera, although the position of the light sensor must be changed after the first image is taken.

[0034] Fig. 2 shows the next step of the method according to the invention for determining an imaging specification. In this step, starting from the edge of the illuminated area 5 initially detected by one of the cameras, the spotlight 1 is moved further along the pan axis 7 with the tilt value unchanged in order to detect the end of the illuminated area 5, i.e., a drop in the received light intensity below a threshold value. As soon as this is detected, the movement of the spotlight stops, and the pan value p2 is stored. The center point in the pan direction pm is determined from pm = (p1 + p2) / 2, and the spotlight moves to this position. In an exemplary embodiment of the method, the pan values ​​p1 = 30624 and p2 = 33184 are detected as the edges of the illuminated area, so that the center point in the pan dimension pm is calculated as 31904.

[0035] Fig. 3 shows the next step of this embodiment. In this step, the spotlight is moved back and forth along the tilt axis with the pan value pm fixed until the two edges of the illuminated area are detected. The respective tilt values ​​along the pan value pm are stored as t1 and t2, and the mean value tm is calculated from tm = (t1 + t2) / 2. The center of the illuminated area 5 is determined in pan and tilt values ​​by the tuple of the two calculated mean values ​​pt1 = (pm, tm).

[0036] In Fig. 4, the headlight 1 is controlled with the values ​​of the tuple pt1, so that the center of the illuminated area 5 moves exactly to the position of the light sensor 2.

[0037] In Fig. 5, in the next step of the method, the pan extension of the illuminated area 5 is determined at its center. For this purpose, the spotlight 1 is moved back and forth along its pan axis at a fixed tilt value tm, and the edges of the illuminated area 5 are detected. This provides the outer limiting pan values ​​p11 and p12 of the illuminated area 5.

[0038] In Fig. 6, the spotlight now completes a full 360° rotation in the pan axis until the illuminated area hits the light sensor 2 again.

[0039] If the pan rotation at point pt1 is already so large that a further 360° rotation around the pan axis is no longer possible, the spotlight can perform a 180° rotation around the pan axis and a tilt flip, i.e., a mirroring of the tilt value around the spotlight's vertical axis. This means that for a tilt value t1 = Y, the new tilt value is set to 65536-Y. However, the tilt value calculated in this way is only correct if the tilt values ​​are distributed symmetrically around the spotlight's center axis. If this is not the case, the tilt flip can lead to an incorrect tilt value. Therefore, in one embodiment of the invention, it is provided that after the tilt flip, the new tilt value is not set to 65536-Y, but with a fixed pan value, the boundaries of the illuminated area are redefined by swiveling the spotlight back and forth in the tilt axis, and the new tilt value tm' is calculated from these.

[0040] The outer limiting pan values ​​p21 and p22 are then measured again by increasing the pan value, and the mean value pm is calculated from pm' = (p21 + p22) / 2. The center of the illuminated area 5 is determined in pan and tilt values ​​by the tuple ptT = (pnT, tm').

[0041] For example, when the illuminated area is detected again, the values ​​p21 = 52504 and p22 = 55064 are determined, so that the point pm' now assumes the value 53784. It is therefore known that the spotlight has performed a rotation by a certain angle between the first detected pan value of 33184 and the second detected pan value of 55064, namely either 360° without a tilt flip or 180° if a tilt flip was necessary. From the difference between the points pt1 and pt1', a mapping rule for the pan values ​​to the absolute angular coordinates can now be determined. In the event that the spotlight has only performed a 180° rotation and a tilt flip, the difference between the pan values ​​must be mapped to a 180° rotation.

[0042] From the two boundaries of the illuminated area 5 and the now known mapping rule between the pan values ​​and the absolute angular coordinates, the aperture angle y of the light cone 4 in the pan plane can be determined in the next step. The aperture angle y corresponds to the difference between the absolute angular coordinates corresponding to the pan values ​​p21 and p22.

[0043] In the optional step shown in Fig. 7, the spotlight is first centered on the center point pm' along the pan axis. Then, with a fixed pan value, the boundaries of the illuminated area t1 and t2 are redefined by swiveling the spotlight back and forth along the tilt axis. From the difference between t1 and t2, the mapping rule for the tilt values ​​to the absolute angular coordinates in the tilt plane can be calculated by comparing it with the known aperture angle y of the light cone 4.

[0044] It is assumed that the aperture angle y of the light cone 4 is identical in the pan and tilt planes. In the case of a non-symmetrical light cone, this can be taken into account in the calculation.

[0045] According to a further embodiment of the invention, the measurement of the illuminated area 5 and the determination of the center point pm are carried out for several, preferably three different, but known positions in absolute coordinates x, y, z of the light sensor 2. This preferably results in three pan / tilt value tuples pt1, pt2, and pt3.

[0046] From the tilt and pan values ​​of the three light sensors, together with the known respective positions x, y, and z of the light sensors, the position of spotlight 1 in absolute space can be determined using known methods. These values ​​can also be used to determine the orientation of spotlight 1, i.e., the direction of the light cone emitted by the spotlight. For this purpose, a multidimensional linear system of equations can be set up, which can be solved using a known mathematical algorithm, for example, a 3D solver.

[0047] The above-mentioned steps for determining an imaging rule and for measuring the aperture angle and the illuminated area can be carried out in other embodiments of the invention with a single 2D camera.

Claims

Patent claims 1. A method for determining the position of a spotlight (1) arranged above a surface (3) which creates an illuminated area (5) on the surface (3), characterized in that a. a light sensor (2) is arranged on the surface (3), i. wherein the light sensor (2) is designed as a camera, wherein the camera has a wide-angle lens, preferably a fisheye lens, and wherein ii. the light sensor (2) has one to three position sensors, preferably ultra-wideband position sensors (8), which are designed to determine the position of the light sensor (2) in a three-dimensional coordinate system, wherein b. the camera creates an image of the spotlight (1), and wherein c. the position of the spotlight (1) is determined at least approximately from the image and the position of the light sensor (2).

2. Method according to claim 1, characterized in that the headlight (1 ) is rotatable about a pan axis (7) by inputting pan values ​​and pivotable about a tilt axis (8) by inputting tilt values, and wherein a. the headlight is rotated and pivoted by inputting tilt and pan values ​​until a pan and tilt value is reached at which the camera detects the headlight (1 ), b. the camera creates a recording of the headlight (1 ), and wherein c. the position of the headlight (1 ) is determined at least approximately from the recording and the position of the light sensor (2). A method according to claim 1 or 2, characterized in that a. the light sensor (2) is arranged at at least two different positions on the substrate (3), and b. optionally, for both positions of the headlights, the camera rotates and pivots by inputting tilt and pan values ​​until a pan and tilt value is reached at which the camera detects the headlight (1), c. the camera takes a picture of the headlight (1) in both positions, and wherein d. the position of the headlight (1) in the coordinate system is calculated from the two pictures and the positions of the light sensor (2). A method according to claim 1 or 2, characterized in that a. the light sensor (2) is designed as a stereo camera with two separate cameras, each camera having a wide-angle lens, preferably a fisheye lens, and b.The method according to any one of claims 2 to 4, characterized in that an imaging specification of the headlight (1) is determined by a. moving the illuminated area (5) over the surface (3) by rotating and pivoting the headlight (1), b. detecting at least one camera's edges of the illuminated area (5), and c. each camera takes a picture of the headlight (1), and d. calculating the position of the headlight (1) in the coordinate system from the different pictures taken by the two cameras.by rotating and / or swiveling the spotlight (1 ) and repeatedly detecting the illuminated area (5) a mapping rule of the pan values ​​and / or the tilt values ​​of the spotlight (1 ) onto the angular coordinates of the spotlight (1 ) is determined. A method according to claim 5, characterized in that the illuminated area (5) is moved over the surface (3) by rotating and pivoting the spotlight (1) until at least one camera of the light sensor (2) detects an edge of the illuminated area (5), and subsequently the dimensions and a center point of the illuminated area (5) are determined by varying the pan value and / or the tilt value of the spotlight (1). A method according to claim 6, characterized in that the dimensions of the illuminated area (5) are detected and the opening angle of the light cone (4) is determined from the calculated imaging specification. A method according to any one of claims 5 to 7, characterized in that a.a. First, by measuring the illuminated area (5) along the plane defined by the pan values, a mapping rule for the pan values ​​to absolute angular coordinates and the opening angle of the light cone (4) along this plane is determined; and b. Subsequently, by measuring the illuminated area (5) along the plane defined by the tilt values, a mapping rule for the tilt values ​​to absolute angular coordinates is determined. A method according to any one of claims 5 to 8 in conjunction with claim 4, characterized in that the mapping rule and / or the opening angle is determined for each of the two cameras. A method according to any one of claims 1 to 9, characterized in that the method is carried out for several spotlights (1) in sequential order. A computer-readable storage medium comprising a computer program for controlling the execution of a method according to any one of claims 1 to 10.

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