Method for determining and calibrating spotlight position

Abstract

The invention relates to a method for determining the position of a spotlight (1), which is arranged above a bottom surface (3) and forms an illuminated area (5) on the bottom surface (3), in which a light sensor (2) is arranged on the bottom surface (3), in which the light sensor (2) is designed as a camera, in which the camera comprises a wide-angle lens, preferably a fisheye lens, 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, and wherein the camera creates a video of the spotlight (1), and wherein the position of the spotlight (1) is determined at least approximately on the basis of the video and the position of the light sensor (2).

Description

[0001] The invention relates to a method for determining the position of a spotlight and for calibrating the spotlight.

[0002] In particular, spotlights are known, for example for illuminating stages in theatres and competition technology and for other applications such as sports events, which are arranged above a base surface and form an illuminated, preferably elliptical area on the base surface by means of a light cone.

[0003] In particular, so-called moving heads or head-mounted spotlights are known, which are arranged rotatably / pivotably along two axes. These two axes are a pivot axis extending parallel to the bottom surface, usually referred to as the pitch axis, and a rotation axis extending perpendicular to the bottom surface, usually referred to as the roll axis. The spotlight can usually be rotated up to 540° along the roll axis and pivoted up to 270° along the pitch axis. With such spotlights, it is preferably possible to illuminate any point on the bottom surface by adjusting the roll and pitch values.

[0004] In order to set up the spotlight for computer-assisted (preferably automatic) illumination of a person on the bottom surface, the position and control values ​​of the spotlight must be calibrated.

[0005] In particular, the position of the spotlight in absolute coordinates must be known. Furthermore, for head-mounted spotlights, it must be known which control values ​​of the used protocol lead to the desired rotation of the spotlight, where the pan and pitch values ​​of the spotlight must be mapped to the most commonly used DMX protocol. In practice, however, several problems arise during the calibration process.

[0006] First, the point in three-dimensional space where the spotlight is located must be determined (x-, y-, and z-coordinates). This is usually done by mapping the stage space and the location of the spotlights, and by generating a three-dimensional model with the aid of a computer. This is cumbersome and error-prone - in most cases it is impossible to correctly measure the exact location of the spotlight. There is also the risk of the spotlight position being changed intentionally or accidentally between measurement time and performance time.

[0007] Furthermore, for head-mounted spotlights, the relationship between the pan and tilt values ​​used to control the spotlight and the resulting beam changes on the stage must be determined. In other words, the pan and tilt values ​​required to achieve a certain displacement of the beam on the stage must be determined. This mapping rule is also usually created using a computer-generated 3D model; therefore, the same inaccuracies may occur. It is impossible to reliably assign a computer-generated model to the real conditions in the stage space.

[0008] Finally, a clear positioning of the spotlight also requires the determination of the rotation, i.e. the beam direction of the light beam formed by the spotlight. Here again the problem arises that computer-generated models often do not correspond to reality.

[0009] According to the invention, these and other problems are solved by providing a method according to the characterizing features of claim 1 .

[0010] In the method according to the invention, a spotlight is arranged above the bottom surface and forms an illuminated area on the bottom surface. 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 the roll axis by entering a roll value and can be pivoted about the pitch axis by entering a pitch value.

[0011] The light sensor is arranged on the bottom surface. According to the invention, the light sensor is designed as a camera with a wide-angle lens, preferably a fisheye lens. The viewing angle of the camera is preferably greater than 100°, preferably greater than 140°, particularly preferably about 180°. The camera can be a conventional 2D camera or a stereo camera.

[0012] The light sensor comprises one to three position sensors, preferably ultra-wideband position sensors, designed to determine the position of the light sensor in a three-dimensional coordinate system. The camera and the position sensor may be wirelessly connected to the data processing unit. The spotlight may also be connected to the data processing unit.

[0013] In the method according to the invention, a camera records a video, ie a photo or a video, of the spotlight, and a data processing unit calculates the position of the spotlight at least approximately based on the video and the position of the light sensor.

[0014] In the case of a moving spotlight, provision can be made to rotate and pivot the spotlight by inputting pitch and roll values ​​until a pitch and roll value is reached at which the camera detects the spotlight. Preferably, the camera can clearly detect the light point of the spotlight in this position so that the exact position of the center point of the spotlight can be determined. Subsequently, the position of the spotlight in the coordinate system is at least approximately calculated based on the camera's recording and the camera position determined by the position sensor.

[0015] For example, the two-dimensional position of the spotlight may be determined based on the video recording of the 2D camera, and then the three-dimensional position of the spotlight in the coordinate system may be estimated based on the estimated height of the spotlight above the bottom surface.

[0016] According to the invention, it can also be provided that the light sensor is arranged at at least two different positions on the bottom surface. Optionally, if the spotlight is movable, the spotlight can be rotated and pivoted for each of the two positions by inputting pitch and roll values ​​until pitch and roll values ​​are reached that enable the camera to detect the spotlight. The camera creates a recording of the spotlight in each of the two positions. The position of the spotlight in a three-dimensional coordinate system is then calculated based on the recordings at the two positions and the two measured positions of the camera. Conventional algorithms for superimposing recordings at two positions of a fixed point taken at different but known positions can be used to calculate the position (photogrammetry).

[0017] According to the invention, it can also be provided that the light sensor is designed as a stereo camera with two separate and spaced-apart individual cameras, each of which has a wide-angle lens, preferably a fisheye lens. The individual cameras are at a known distance from one another, for example 10 cm to 20 cm. The viewing angle of the cameras is greater than 100°, preferably greater than 140°, particularly preferably about 180°. The data processing unit knows the distance between the individual cameras.

[0018] If the spotlight is a moving spotlight, rotate and pivot the spotlight by entering the pitch and roll values ​​until a roll and tilt value is reached that allows both cameras to detect the spotlight. When using a stereo camera, both cameras can create a recording of the spotlight simultaneously. In practice, it is usually sufficient for the spotlight to flash on the light sensor, since both cameras can usually record the spotlight due to the large aperture angle of the camera. Thus, the position can be determined very quickly without moving the light sensor.

[0019] The position of the spotlight in the coordinate system is then calculated based on the different recordings of the two cameras, the known distance between the two cameras and the position of the light sensor in the coordinate system, where a traditional algorithm is again used to superimpose the recordings at the two positions of fixed points created at different but known positions (photogrammetry).

[0020] According to the invention, when a movable spotlight is used, provision can be made for determining the mapping rule of the spotlight by rotating and pivoting the spotlight until at least one of the two cameras detects the edge of the illuminated area, thereby moving the illuminated area on the bottom surface. This is possible both in the version with only one 2D camera and in the version with stereo cameras.

[0021] Subsequently, a mapping rule of the pan and / or tilt values ​​of the spotlight to the angular coordinates of the spotlight is determined by rotating and / or pivoting the spotlight and by repeatedly detecting the illuminated area. In particular, the mapping rule can be calculated using the method described in WO 2018 / 154108A1.

[0022] Provision can be made for the illuminated area to be moved across the bottom surface by rotating and pivoting the spotlight until at least one of the two cameras detects an edge of the illuminated area and subsequently determining the size and center of the illuminated area by varying the pan and / or tilt values ​​of the spotlight.

[0023] According to the invention, provision can be made to detect the size of the illuminated area and determine the aperture angle of the light cone according to the calculated mapping rule. In particular, it can be presupposed that the light cone is symmetrical, so that the aperture angle is the same in the roll and pitch axes.

[0024] According to the present invention, it can be provided that, first, a mapping rule of the pan value to the absolute angular coordinate and the aperture angle of the light cone along the plane are determined by measuring the illuminated area along the plane where the adjustment direction of the pan value lies.

[0025] Subsequently, a mapping rule from the pitch value to the absolute angular coordinate may be determined by measuring the illuminated area along a plane where the adjustment direction of the pitch value is located.

[0026] According to the invention, in an embodiment with a stereo camera, provision can be made for each of the two cameras of the light sensor to determine a mapping rule and / or an aperture angle. The determined mapping rules can then be compared and, optionally, if deviations occur, an error signal can be output. Provision can also be made to define an average of the mapping rules determined by the two cameras to determine an average mapping rule.

[0027] According to the invention, provision can be made for the method to be applied sequentially to a plurality of spotlights.

[0028] The invention also relates to a computer-readable storage medium comprising a computer program, such as a smartphone application or a program on a server, which controls the course of the method according to the invention. The computer program can control the spotlight with the necessary pan and tilt values, receive a camera image and calculate the target value of the method.

[0029] The spotlight may operate in any wavelength range, wherein the camera is configured to detect the signal sent by the spotlight. In particular, a wavelength range of 380 nm to 780 nm (visible light) or higher (infrared) may be provided.

[0030] Further features according to the invention emerge from the claims, the description and the drawings.

[0031] In the following, the invention is explained in more detail based on non-exclusive exemplary embodiments.

[0032] Figures 1 to 7The following are the consecutive method steps of an embodiment of the method according to the invention based on a spotlight and a light sensor 2 arranged on a bottom surface. In this embodiment, the light sensor is designed as a stereo camera, comprising two individual cameras about 15 cm apart, each equipped with a fisheye lens with a viewing angle of about 150°.

[0033] Figure 1 A bottom surface 3 (e.g. a theatre stage) and a spotlight 1 mounted above the bottom surface are shown. A mobile light sensor 2 in the form of a stereo camera with two (schematically shown) fisheye lenses is arranged on the bottom surface 3. The light sensor 2 can be controlled wirelessly and connected to an external computer unit. The light sensor is not fixed to the bottom surface 3 but is detachably placed on the bottom surface.

[0034] In addition, there are two ultra-wideband position sensors (not shown) on the optical sensor 2, which can be used to determine the absolute position of the mobile optical sensor 2 in the three-dimensional coordinate system.

[0035] The spotlight 1 is pivotable about two axes perpendicular to each other. The spotlight can be rotated about 540° along a schematically indicated pan axis 7. The spotlight can be pivoted 180° along a schematically indicated tilt axis 8. The spotlight 1 emits a light cone 4 with a light cone axis 6, forming an illuminated area 5 on a bottom surface 3. The illuminated area 5 formed on the bottom surface 3 is generally elliptical.

[0036] By rotating around the roll and pitch axes, the spotlight 1 can illuminate any point on the bottom surface 3. In the embodiment considered, the possible values ​​of the roll and pitch values ​​range from 0 to 2. 16 = 65536 ticks. Therefore, from a roll value of 0 to a roll value of 65536, the spotlight rotates about the roll axis by about 540°. It can be assumed that the mapping of roll values ​​to angle ranges is linear, but the exact mapping rule of roll values ​​to the angle range covered is unknown. The same is true for pitch values.

[0037] In one embodiment of the present invention, the light sensor 2 is first placed on the bottom surface 3, and then the light cone 4 is systematically moved across the bottom surface 3 along a predefined curve until the camera of the light sensor 2 detects the edge of the illuminated area 5. Figure 1 The curve along which the light cone 4 moves is schematically indicated by a dashed line in . As soon as both cameras of the stereo camera detect the illuminated area 5 , the movement of the spotlight 1 stops and the roll value p1 and the pitch value t1 of this position are saved.

[0038] In order to determine the position of the spotlight 1, the two cameras of the light sensor 2 each record a picture of the spotlight 1. Based on the two pictures and the distances between the two cameras and the known position, the position of the spotlight 1 in the coordinate system is determined by photogrammetry.

[0039] In an exemplary embodiment of the invention not shown, the position is determined by a mobile light sensor with only one 2D camera, however, after the first recording, the position of the light sensor must be changed.

[0040] Figure 2 The next step of the method for determining a mapping rule according to the invention is shown. In this step, starting from the edge of the illuminated area 5 initially detected by one of the two cameras, the spotlight 1 is further moved on the roll axis with a constant pitch value 7 to detect the end of the illuminated area 5, i.e. to reduce the received light intensity below a threshold. As soon as this is detected, the movement of the spotlight stops and the roll value p2 is saved. The center in the direction of the roll axis pm is determined by pm=(p1+p2) / 2 and the spotlight moves at this position. In an exemplary embodiment of the method, the roll values ​​p1=30624 and p2=33184 are detected as the edges of the illuminated area, so that the center in the direction of the roll axis pm is calculated to be 31904.

[0041] Figure 3 The next step of this embodiment is shown. In this step, the spotlight is moved back and forth along the pitch axis with a fixed roll value pm until the two edges of the illuminated area are detected. The corresponding pitch values ​​along the roll value pm are saved as t1 and t2, and the average value tm is calculated as tm=(t1+t2) / 2. The center of the illuminated area 5 is set with the roll value and the pitch value by a tuple pt1=(pm,tm) of the two calculated average values.

[0042] exist Figure 4 In the example above, the value of tuple pt1 is used to control spotlight 1 so that the center of illuminated area 5 moves to the exact position of light sensor 2.

[0043] exist Figure 5 In the next step of the method, the roll extension of the illuminated area 5 is determined at the center of the illuminated area.

[0044] To this end, the spotlight 1 is moved back and forth on its roll axis with a fixed pitch value tm and the edges of the illuminated area 5 are detected. This provides the outer delimiting roll values ​​p11 and p12 of the illuminated area 5.

[0045] exist Figure 6 In the example above, the spotlight is rotated through 360° on the roll axis until the illuminated area meets light sensor 2 again.

[0046] If the spotlight at point pt1 has been rotated around the roll axis to the point where it can no longer be rotated 360° further around the roll axis, the spotlight can be rotated 180° around the roll axis and pitch flipped, i.e. the pitch value is mirrored about the vertical axis of the spotlight. This means that at pitch value t1=Y, the new pitch value is set to 65536-Y. However, the pitch value calculated in this way is correct only if the pitch values ​​are symmetrically distributed around the center axis of the spotlight. If this is not the case, the pitch flip may result in incorrect pitch values. Therefore, one embodiment of the present invention provides that the new pitch value after the pitch flip is not set to 65536-Y, but the limits of the illuminated area are re-determined by pivoting the spotlight back and forth along the pitch axis at a fixed roll value, and the new pitch value tm' is calculated based on these limits.

[0047] Then, by adding the roll value, the outer bounding roll values ​​p21 and p22 are remeasured and the average pm is calculated as pm' = (p21 + p22) / 2. The center of the illuminated area 5 is set with the roll and pitch values ​​by the tuple pt1' = (pm', tm').

[0048] When re-detecting the illuminated area, for example, the values ​​p21=52504 and p22=55064 are determined, so that the point pm' takes the value 53784. It is therefore known that the spotlight has rotated by an angle between the first detected roll value 33184 and the second detected roll value 55064, i.e. 360° without a pitch flip, or 180° if a pitch flip is required.

[0049] Now, based on the difference between points pt1 and pt1', the mapping rule for the roll value to the absolute angular coordinate can be determined. If the spotlight only performs 180° rotation and pitch flip, the difference in the roll value must be mapped to a 180° rotation.

[0050] From the two limits of the illuminated area 5 and the mapping rule between roll values ​​and absolute angular coordinates (now known), the next step may be to determine the aperture angle γ of the light cone 4 in the roll plane. The aperture angle γ corresponds to the difference in absolute angular coordinates corresponding to the roll values ​​p21 and p22.

[0051] In accordance with Figure 7 In an optional step, the spotlight is first centered on the center pm' of the roll axis. Then, the limits t1 and t2 of the illuminated area are redefined by pivoting the spotlight back and forth on the pitch axis at a fixed roll value. Based on the difference t1 and t2, the mapping rule of the pitch value to the absolute angular coordinates in the pitch plane can be calculated by comparison with the known aperture angle γ of the light cone 4.

[0052] It is assumed that the aperture angle γ of the light cone 4 is the same in the roll plane and in the pitch plane. In the case of an asymmetric light cone, this can be taken into account in the calculation.

[0053] According to another embodiment of the invention, the illuminated area 5 is measured and the centre pm is determined for a plurality, preferably three different but known positions in the absolute coordinates x, y, z of the light sensor 2. Preferably, this results in a triplet of roll / pitch values ​​pt1, pt2 and pt3.

[0054] From the pitch and roll values ​​of the three light sensors and the known corresponding positions x, y, z of the light sensors, the position of the spotlight 1 can be determined in absolute space by known methods.

[0055] Furthermore, the orientation of the spotlight 1, ie the direction of the light cone emitted by the spotlight, can be determined from these values. To this end, a multidimensional linear system of equations can be established which can be solved by mathematical algorithms known per se (eg 3D solvers).

[0056] In other embodiments of the present invention, a single 2D camera may be used to perform the above steps of determining the mapping rule and measuring the aperture angle and the illuminated area.

Claims

1. A method for determining the position of a spotlight (1), said spotlight being arranged above a bottom surface (3) and forming an illuminated area (5) on said bottom surface (3), Features a. The optical sensor (2) is arranged on the bottom 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 optical sensor (2) has one to three position sensors, preferably ultra-wideband position sensors (8), which are designed to determine the position of the optical sensor (2) in a three-dimensional coordinate system, wherein b. The camera creates a video recording of the spotlight (1), and wherein c. Determining at least approximately the position of the spotlight (1) based on the video recording and the position of the light sensor (2).

2. The method according to claim 1, characterized in that The spotlight (1) can be rotated about a roll axis (7) by inputting a roll value, and can be pivoted about a pitch axis (8) by inputting a pitch value, and wherein a. rotating and pivoting the spotlight by inputting pitch and roll values ​​until a pitch and roll value is reached that enables the camera to detect the spotlight (1), b. The camera creates a video recording of the spotlight (1), and wherein c. Determining at least approximately the position of the spotlight (1) based on the video recording and the position of the light sensor (2).

3. The 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 bottom surface (3), and b. Optionally, for each of the two positions, rotating and pivoting the spotlight by inputting a pitch value and a roll value until a pitch value and a roll value are reached that enables the camera to detect the spotlight (1), c. At these two positions, the camera creates a video recording of the spotlight (1), respectively, and wherein d. Calculating the position of the spotlight (1) in the coordinate system based on the video recordings at two positions and the two positions of the light sensor (2).

4. The method according to claim 1 or 2, characterized in that a. The optical sensor (2) is designed as a stereo camera with two separate cameras, wherein the two cameras each have a wide-angle lens, preferably a fisheye lens, and b. Optionally, rotating and pivoting the spotlight by inputting pitch and roll values ​​until a pitch and roll value is reached that enables both cameras to detect the spotlight (1), and wherein c. The two cameras respectively create a video recording of the spotlight (1), and wherein d. Calculating the position of the spotlight (1) in the coordinate system based on the different videos of the two cameras.

5. The method according to any one of claims 2 to 4, characterized in that The mapping rule of the spotlight (1) is determined by the following operations: a. by rotating and pivoting the spotlight (1), so that the illuminated area (5) moves across the bottom surface (3), b. at least one camera detects the edge of the illuminated area (5), and c. Determine a mapping rule of the roll value and / or the pitch value of the spotlight (1) to the angular coordinates of the spotlight (1) by rotating and / or pivoting the spotlight (1) and by repeatedly detecting the illuminated area (5).

6. The method according to claim 5, characterized in that The illuminated area (5) is moved across the bottom surface (3) by rotating and pivoting the spotlight (1) until at least one camera of the light sensor (2) detects the edge of the illuminated area (5), and the size and center of the illuminated area (5) are then determined by changing the pan value and / or the pitch value of the spotlight (1).

7. The method according to claim 6, characterized in that The size of the illuminated area (5) is detected according to the calculated mapping rule and the aperture angle of the light cone (4) is determined.

8. The method according to any one of claims 5 to 7, characterized in that a. First, by measuring the illuminated area (5) along the plane where the adjustment direction of the pan value is located, a mapping rule of the pan value to the absolute angular coordinate and an aperture angle of the light cone (4) along the plane are determined, and b. Subsequently, the mapping rule from the pitch value to the absolute angular coordinate is determined by measuring the illuminated area (5) along the plane where the adjustment direction of the pitch value lies.

9. The method according to any one of claims 5 to 8 in combination with claim 4, characterized in that: The mapping rule and / or aperture angle is identified for each of the two cameras.

10. The method according to any one of claims 1 to 9, characterized in that The method is applied sequentially to a plurality of spotlights (1).

11. A computer-readable storage medium comprising a computer program for controlling the process of the method according to any one of claims 1 to 10.

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