METHOD FOR SPATIAL CHARACTERIZATION OF THE OPTICAL EMBARGO OF LIGHT AND RADIATION SOURCES

Description

[0001] The invention relates to a method for spatially characterizing the optical radiation behavior of a light source that is fixedly clamped in a positioning device, using a luminance measuring camera that is fixedly arranged relative to a world coordinate system, wherein the light source is moved between a first actual measurement position and at least one further actual measurement position along a kinematic chain of the positioning device in the world coordinate system. Furthermore, the invention relates to the application of such a method for the photometric measurement of headlights.

[0002] For the characterization of the optical properties of light sources, especially lamps and luminaires, their radiation behavior is of interest, in particular the luminous intensity distribution, also known as the luminous intensity distribution body or luminous intensity distribution curve (LVK).

[0003] When measuring the LDC of headlights, particularly high demands are placed on the spatial resolution of the measuring technology, since large gradients in the LDC require a very precise positioning of the object of usually 0.01° in order to record the measuring points with sufficient precision in the object coordinate system.

[0004] Spotlights are used in many areas of lighting technology. These include vehicle headlights, stage spotlights, street lights, signal lights for rail and road traffic, and even beacons and position lights for aviation and naval applications.

[0005] Various procedures have been established here, which have been incorporated into the standards EN 13032 Part 1 and Part 4, CIE 121 and, for the field of vehicle technology, into the ECE regulations R1 and others, as well as into the Federal Motor Vehicle Safety Standard and CCC based on Guobiao standards.

[0006] For direct photometric or photometric measurement of headlights, goniophotometers are used. These include a photosensor (photometer head) positioned at a defined distance from the headlight and receiving the light. To spatially record the beam pattern, the headlight is rotated about at least one axis of rotation. With a goniophotometer designed as a luminaire tilter, the headlight is rotated about two mutually orthogonal axes of rotation that intersect at a center of rotation during photometric measurement.

[0007] In a goniophotometer designed in this way, an object coordinate system, which is always defined here and in the following with respect to the object to be measured, for example with respect to the headlight or generally to a lamp held by the goniophotometer, is moved relative to the world coordinate system when the object is rotated about at least one axis of rotation.

[0008] The dimensions and weight of headlights, for example vehicle headlights, including the necessary rigid mounts in combination with the high positioning accuracy result in very high demands on the mechanical accuracy and resilience, for example the bending and torsional rigidity, of such goniophotometers.

[0009] In indirect photometric measurement, the radiation emitted by the headlight is captured by a medium positioned at a sufficiently large distance in the beam path of the headlight. Such media are diffusely reflective or scattering and preferably spectrally neutral. With this indirect photometric measurement method, the diffusely reflecting or scattering medium can be captured using an imaging process in a single exposure step. This enables a faster measurement compared to the point-by-point, sequential detection of a light distribution using a goniophotometer.

[0010] A luminance measuring camera records a partial luminous flux from the spotlight on the irradiated medium. The medium can be arranged in a transmitted-light beam path, i.e., transmitting between the luminance measuring camera and the spotlight, or in a reflected-light beam path, i.e., reflecting the spotlight's light. The medium can be a curved or flat surface.

[0011] The LDC can be determined from the luminance distribution recorded by the luminance measuring camera and scattered or reflected on the irradiated medium by evaluating the geometric relationships between the luminance measuring camera, the medium and the spotlight.

[0012] Incremental methods are also known, in which several partial LDCs are recorded at different angular positions of the spotlight relative to the medium, and a total LDC is determined from them. This requires both a geometric transformation to correct, for example, distortion, rectification, and / or coordinate transformation, as well as a photometric transformation to convert luminance values ​​into illuminance or luminous intensity values.

[0013] Measurement setups and methods are also known in which the spotlight is pivoted relative to the medium around one or more axes using a goniometer. Such goniometers are also subject to high accuracy requirements, since the angular position of the measurement object (spotlight) adjusted on the goniometer is incorporated into the determined LDC via geometric and / or photometric transformation.

[0014] Document DE 10 2014 430 A1 describes a method and a gonioradiometer for the direction-dependent measurement of at least one photometric or radiometric parameter of an optical radiation source. The radiation direction of the photometric or radiometric parameter is described using a plane system whose planes intersect in a straight line passing through the radiation center of the radiation source, and using a radiation angle that specifies the radiation direction within a considered plane. During the measurement, a sensor or the radiation source is moved in such a way that the sensor records measured values ​​that indicate the photometric or radiometric parameter on a spherical surface around the radiation center of the radiation source.It is intended that the sensor or the radiation source is attached to a multi-axis swivel arm robot and that the robot is swiveled about only exactly one of its axes during a measurement process in which measured values ​​are acquired that relate to different radiation angles within a considered plane of the plane system or different planes at a considered radiation angle.

[0015] Document DE 2018 208 203 A1 describes target bodies comprising a plurality of markers that together form a target for optical detection and for determining a position and / or an orientation of the target body from the detected markers, in particular for determining a position and / or an orientation of a movable part of a coordinate measuring machine, a robot, a material application machine, or a machine tool. The target body has a plurality of surface regions, the surface regions being oriented in different directions, and at least one of the markers being arranged in each of the surface regions. Document DE 2018 208 203 A1 further describes an arrangement comprising such a target body and a method for determining a position and / or an orientation of a target body.

[0016] Document DE 10 2015 201 093 A1 describes a method and gonioradiometer for the direction-dependent measurement of at least one photometric or radiometric parameter of an optical radiation source. It is proposed that at least two permanently installed sensors be used, which provide measured values ​​simultaneously during a measurement.

[0017] The publication Chr. Schwanengel: "Comparison of measurement techniques for measuring luminous intensity distributions and luminous intensity distribution sections", available online at URL: https: / / www.technoteam.de / e6009 / e6311 / e5983 / pb_download5985 / LVK _ Measurement technology_ger.pdf describes devices and methods for measuring luminous intensity with a luminance measuring camera.

[0018] Document US 2019 / 0362519 A1 describes measuring mark bodies with a plurality of measuring marks configured for optical detection and for determining the position and / or orientation, in particular of a movable part on a coordinate measuring machine, a robot, a material processing machine, or a machine tool. The document further describes a device comprising such a measuring mark body and a method for determining the position and / or orientation thereof.

[0019] The publication Lindemann et al.: "Robot goniophotometry at PTB", Metrologia, Institute OfPhysics Publishing, Bristol, UK, Vol. 52, No. 2, 5 February 2015, pages 167-194 DOI: 10.1088 / 0026-1394 / 52 / 2 / 167 describes a device and a method for photometric measurement using robots, wherein a first robot carries a light source to be measured and two further robots each carry a photometer, with which a luminous intensity emitted by the light source is measured simultaneously.

[0020] Document DE 10 2015 201 093 A1 describes a method and gonioradiometer for the direction-dependent measurement of at least one photometric or radiometric parameter of an optical radiation source. It is proposed that at least two permanently installed sensors be used, which provide measured values ​​simultaneously during a measurement.

[0021] The invention is based on the object of providing an improved method for the spatial characterization of the radiation behavior of a light source moved by means of a positioning device relative to a world coordinate system.

[0022] The object is achieved according to the invention by a method having the features of claim 1.

[0023] Furthermore, the invention is based on the object of specifying the application of such a method for improved photometric measurement of a headlight. This object is specified according to the invention by the features of claim 15.

[0024] Advantageous embodiments of the invention are the subject of the subclaims.

[0025] In a method for photometric measurement of a light source, the light source is clamped in a positioning device. The positioning device is configured to move the light source between actual measurement positions specified relative to a world coordinate system. Preferably, the positioning device is configured to pivot the light source about pivot axes that may intersect at a center of rotation.

[0026] An object coordinate system is defined that is fixed to the clamped light source.

[0027] The photometric measurement is performed using a luminance measuring camera fixed to the world coordinate system. Instead of a luminance measuring camera, a point-measuring sensor, such as a photometer, can also be used for photometric measurement. For example, the light source is scanned relative to the point-measuring sensor, maintaining sufficiently close measurement distances between the measurement points.

[0028] A reflecting and / or scattering medium can be arranged in the beam path from the light source to the luminance measuring camera in such a way that the medium is illuminated by the light source, and the light reflected and / or scattered by the medium is captured by the luminance measuring camera. In other words, the photometric measurement can be performed indirectly.

[0029] However, it is also possible that the luminance measuring camera is directly illuminated by the light source or that the luminance measuring camera directly records the luminance distribution of the light source.

[0030] The light source is moved between a first actual measurement position and at least one further actual measurement position along a kinematic chain of the positioning device in the world coordinate system. The kinematic chain extends from an element of the positioning device that is fixed relative to the world coordinate system, for example, a base, to an element in which the light source is clamped in a rigid position and which is designed, for example, as a holding device.

[0031] The positioning device may comprise a plurality of machine coordinate systems that can be moved (displaced and / or rotated) relative to one another according to the kinematic chain. In particular, the positioning device comprises a holding coordinate system that is related to the holding device located at the end of the kinematic chain.

[0032] For a mechanically rigid fixture in which the light source is sufficiently stably fixed during the measurement, the object coordinate system (related to the light source) and the holding coordinate system (related to the fixture) are linked by a constant transformation, which can be described as a constant pose of the object coordinate system relative to the holding coordinate system.

[0033] However, it is also possible that, for example due to elastic deformation of the holding device, the position and / or orientation of the object coordinate system, i.e. the pose, vary relative to the holding coordinate system during the measurement.

[0034] At each actual measurement position, a luminance measurement image is recorded using the luminance measurement camera with the light source switched on. The luminance measurement image describes the spatial distribution of a photometric parameter within a measurement area. A measurement area can be formed, for example, by the collecting plane of a flat, diffusely reflecting or diffusely scattering medium illuminated by the light source. However, a measurement area can also be curved, for example, spherically curved.

[0035] When recording a luminance measurement image in an actual measurement position of the light source, the position and / or orientation of the object coordinate system relative to the world coordinate system are recorded in direct relation to the world coordinate system without reference to the kinematic chain of the positioning device.

[0036] Position is the three-dimensional spatial offset between the object coordinate system and the world coordinate system. Orientation is the rotation of the object coordinate system relative to the world coordinate system. Position and orientation together are referred to as pose. Each actual measurement position is determined by the pose of the object coordinate system relative to the world coordinate system at the time of the measurement.

[0037] A detection of the position and / or orientation of the object coordinate system is referred to as direct and without reference to the kinematic chain of the positioning device if it is carried out independently of the detection of parameters of the relative movement between individual elements of the kinematic chain.

[0038] An advantage of the method is that the position and especially the orientation can be determined cost-effectively in direct reference, i.e. without complex sensors along the kinematic chain of the positioning device.

[0039] A further advantage of the method is that mechanical and / or sensory characteristics along the kinematic chain, such as bending or torsion of not completely rigid links, play or inaccuracies of sensors, do not affect the accuracy of determining an actual measuring position.

[0040] This is particularly advantageous because the characteristic mechanical properties of the kinematic chain are influenced by the moments occurring in the measurement object. These moments depend on the pose and mass distribution of the measurement object. With knowledge of the moment distribution, the characteristic deviations can be compensated for, but this requires additional effort to determine them first. This additional effort is eliminated with this method of directly determining the pose of the object coordinate system in the world coordinate system.

[0041] A further advantage of the method is that it is not necessary to approach a predefined target measurement position with high accuracy. Rather, it is sufficient to approach a target measurement position with low accuracy, but to measure the actual measurement position with high accuracy by direct reference in the world coordinate system. This makes it possible to position the light source even with less precise and less costly positioning devices.

[0042] A positioning device has a guaranteed positioning tolerance, which specifies the maximum deviation of an actually approached actual measurement position from a specified (to be approached) target measurement position. In contrast, the detection of the position and / or orientation of the object coordinate system relative to the world coordinate system has a guaranteed detection tolerance, which specifies the maximum deviation of the actual position and / or orientation of the object coordinate system from the detected position and / or orientation of the object coordinate system relative to the world coordinate system.

[0043] The detection of the position and / or orientation of the object coordinate system relative to the world coordinate system has a guaranteed detection tolerance which is smaller than the guaranteed positioning tolerance of the positioning device with respect to at least one parameter.

[0044] In other words: the position and / or orientation of the object coordinate system relative to the world coordinate system is detected in each actual measuring position in direct relation to the world coordinate system without reference to the kinematic chain of the positioning device with a detection tolerance that is smaller than the assured positioning tolerance of the positioning device with regard to at least one parameter.

[0045] An advantage of the method is that a cost-effective positioning device with a higher positioning tolerance is used without compromising the accuracy of the photometric measurement of the light source.

[0046] In the method, a required positioning tolerance of the positioning device is determined which is sufficient so that a sequence of target measuring positions can be arranged and approached in such a way that a complete recording of the photometric characteristic in the measuring area is possible with the assigned sequence of actually reached actual measuring positions, each lying within the positioning tolerance around a target measuring position.

[0047] A positioning device with a positioning tolerance is selected and used to clamp the light source, which is smaller or preferably equal to the required positioning tolerance thus determined.

[0048] In other words: a required positioning tolerance of the positioning device is determined and a positioning device with a positioning tolerance is selected which is smaller or preferably equal to the determined required positioning tolerance, wherein the required positioning tolerance is determined in such a way that a sequence of target measuring positions can be arranged and approached in such a way that with the assigned sequence of actually achieved actual measuring positions, each lying within the positioning tolerance around a target measuring position, a complete recording of the photometric characteristic in the measuring area is possible.

[0049] An advantage of the method is that a cost-effective positioning device with a high positioning tolerance is used without compromising the accuracy of the photometric measurement of the light source.

[0050] In one embodiment, a positioning device is selected which has a positioning tolerance of at least ±1 millimeter, preferably of at least ±5 millimeters.

[0051] An advantage of this embodiment is that a cost-effective positioning device with a high positioning tolerance is used without compromising the accuracy of the photometric measurement of the light source.

[0052] In one embodiment of the method, a medium configured for diffuse reflection and / or scattering of the light emitted by the light source is arranged in a fixed position and orientation relative to the world coordinate system. For example, such a medium can be designed as a diffusely reflecting screen or a diffusing disk.

[0053] The medium is arranged so that it is illuminated by the light source and the diffusely reflected and / or scattered light is recorded by the luminance measurement camera in a luminance measurement image.

[0054] The advantage of such an indirect photometric measurement is that a relatively large segment of the light distribution can be captured with a single measurement. The size of the segment depends on the realized size of the medium.

[0055] In one embodiment of the invention, the luminance measuring camera can detect the light source directly, i.e., without the use of a medium. In this embodiment, the measuring surface is arranged on a surface of the light source facing the luminance measuring camera.

[0056] In the illumination beam path from the light source to the medium (for indirect photometric measurement) or from the light source to the luminance measuring camera (for direct photometric measurement), imaging optical components, such as lenses and / or mirrors, can also be arranged for beam steering or beam shaping.

[0057] In one embodiment of the method, the light source is pivoted around at least one axis passing through a center of rotation during photometric measurement. This allows for a particularly simple assessment of the light source, since the coordinate origin of the object coordinate system related to the light source coincides with the center of rotation, thus eliminating the need for an additional coordinate transformation to obtain a LDC.

[0058] In one embodiment of the method, in a first step, the position of the object coordinate system relative to the world coordinate system is determined by directly probing at least one measuring mark. In a second step, the orientation of the object coordinate system relative to the world coordinate system is determined.

[0059] An advantage of this embodiment of the method is that, for assessing the light source, a position determination with low accuracy, for example, with a permissible positioning accuracy of one millimeter, is sufficient and possible using cost-effective methods. In contrast, a determination of the orientation with high accuracy, for example, with a permissible angular deviation of 1 / 100 of a degree, is required. By separating the determination of the positioning from the determination of the orientation, an overall cost-effective and sufficiently accurate determination of the pose and thus an improved photometric measurement of the light source can be achieved.

[0060] In one embodiment of the method, the position and / or orientation of the object coordinate system are determined by detecting at least one measuring mark by means of at least one referencing camera.

[0061] Measuring marks and referencing cameras are available at low cost and can be easily arranged and operated on a positioning device and / or in a surrounding space. Furthermore, the acquisition of measuring marks with referencing cameras is particularly fast, almost instantaneous.

[0062] In one embodiment of the method, at least one referencing camera is arranged stationary relative to the world coordinate system, and at least one measuring mark is arranged stationary relative to the object coordinate system. Since a measuring mark is small and lightweight and can be easily attached and removed, a particularly simple, cost-effective, and precise measurement is possible.

[0063] In one embodiment of the method, at least one referencing camera is arranged stationary relative to the object coordinate system, and at least one measurement mark is arranged stationary relative to the world coordinate system. Preferably, at least one measurement mark is formed from spatial features arranged stationary in the world coordinate system, for example, installation equipment or architectural features. This enables particularly easy and flexible detection of the pose of the world coordinate system.

[0064] In one embodiment of the method, at least one measurement mark is configured as an active measurement mark for emitting radiation that can be detected by at least one referencing camera associated with this measurement mark. Active measurement marks are particularly easy to detect and localize in images from a referencing camera. Radiation emitted by different active measurement marks can be spectrally and / or temporally distinguishable. This can improve the reliability of detection of measurement marks.

[0065] In one embodiment of the method, at least one collecting plane is arranged in a fixed position in the world coordinate system. When approaching an actual measurement position, the position of the object coordinate system is determined, and the orientation of the object coordinate system is determined from the measurement of a modulated illumination, i.e., a illumination that varies depending on location or solid angle, emitted from a known direction relative to the object coordinate system and captured on the at least one collecting plane.

[0066] An advantage of this method is that by measuring the distortion of a known modulated illumination, an angle relative to the collecting plane can be determined very precisely and easily.

[0067] In one embodiment of the method, the modulated illumination is generated by means of a diffractive optical element (DOE) as a projection matrix comprising at least one projection structure. Each projection structure is projected along a respective pilot beam onto a collecting plane.

[0068] The projection matrix can be designed as a point matrix, with projection structures designed as projection points being arranged at intervals.

[0069] Such projection matrices are particularly easy to generate and can be evaluated with great accuracy by capturing the projection matrix captured on the capture plane using a camera and locating at least one projection structure in the camera image.

[0070] The projection points can be arranged at regular intervals, for example, equal distances. Using such projection matrices, a change in the position of the point matrix projected onto the capture plane and / or a change in the projection direction within a range dependent on the point spacing can be determined with high accuracy.

[0071] The at least one projection structure can also be spatially modulated (structured) in an irregular manner. For example, a projection structure can be selected such that it generates a two-dimensional, aperiodically shaped brightness distribution whose two-dimensional autocorrelation function preferably has only one maximum and is particularly preferably shaped similarly to a Dirac pulse. With projection structures shaped in this way, a change in the position of a projection onto the capture plane can be unambiguously determined over a particularly large area.

[0072] In other embodiments, the modulated illumination is configured as a stripe or grating projection. Methods are known from the prior art with which the inclination of an optical axis along which a stripe or grating projection is projected onto a collecting plane can be determined relative to the surface normal of the collecting plane.

[0073] In one embodiment of the method, the modulated illumination is emitted by the light source and projected directly onto the luminance measuring camera or indirectly recorded by the luminance measuring camera as luminance projected onto a medium or a collecting plane.

[0074] Actual measuring positions are approached, each of which is within a predetermined distance of a target measuring position, with at least one luminance measurement image being recorded in each actual measuring position.

[0075] The target measurement positions are selected such that at least two luminance measurement images overlap, whereby the offset between overlapping luminance measurement images is determined by means of an image registration method and the respective orientation of the object coordinate system is determined from this and from the actual measurement positions assigned to the luminance measurement images.

[0076] An advantage of this embodiment is that the direction of the object coordinate system can be determined using the existing luminance measuring camera and thus without additional effort.

[0077] In one embodiment of the method, a target measurement position is determined for each actual measurement position by evaluating parameters of the positioning device. The position and orientation of the object coordinate system are recorded based on the target measurement position.

[0078] An advantage of this design is that the target measurement position allows for an approximate determination of the actual measurement position. This allows for a reduction in the measuring range required for precise acquisition of the actual measurement position in direct reference (without reference to the kinematic chain). This allows for simpler and more accurate acquisition of the actual measurement position, and thus also enables simpler and more accurate photometric measurement.

[0079] In one embodiment of the method, the positioning device is controlled for approaching a target measuring position in such a way that an actual measuring position is reached within a predetermined distance from the respectively assigned target measuring position. The control can be performed iteratively, for example, by gradually reducing the distance between the actual measuring position and the target measuring position.

[0080] An advantage of this design is that it achieves particularly high accuracy in positioning the light source. This enables particularly precise photometric measurements.

[0081] The described method can be used for the photometric measurement of a headlight. Headlights are subject to particularly high accuracy requirements for photometric measurement. Advantageously, these particularly high accuracy requirements can be achieved with the proposed method even if the positioning device exhibits a higher inaccuracy when approaching target measurement positions than would be permissible with state-of-the-art methods.

[0082] This allows for reduced equipment and process complexity. For example, positioning devices with greater mechanical play and lower bending and torsional rigidity of the elements of the kinematic chain can be used than would be possible with state-of-the-art photometric measurement methods.

[0083] In particular, the described method can be applied to the photometric measurement of a vehicle headlight. For the photometric measurement of vehicle headlights, a simple measurement procedure that can be implemented using cost-effective positioning devices, as well as high accuracy and reproducibility, are particularly important.

[0084] Embodiments of the invention are explained in more detail below with reference to the drawings, in which: Figure 1 schematically shows a positioning device designed as a goniometer for positioning a light source according to the prior art, Figure 2 schematically shows a positioning device designed as an industrial robot with measuring marks arranged thereon, Figure 3 schematically shows a positioning device designed as an industrial robot with marking discs arranged thereon, Figure 4 schematically shows a positioning device designed as an industrial robot with referencing cameras arranged thereon, Figure 5 schematically shows a positioning device with a pilot light source for projecting a dot matrix, Figure 6 schematically shows an optical capture device for partially capturing a projected dot matrix, Figure 7 schematically shows a holding device with a vehicle headlight in various actual measurement positions and Figure 8 schematically shows luminance measurement images of a vehicle headlight taken from various actual measurement positions.

[0085] Corresponding parts are provided with the same reference numerals in all figures.

[0086] Figure 1 shows a positioning device 1 for positioning a light source Q according to the prior art. The positioning device 1 is embodied, for example, as a goniometer 10. A base 10.F of the goniometer 10 is stationary in a Cartesian world coordinate system W and supports a tripod 10.S. The world coordinate system is determined by the world x-axis Wx, the world y-axis Wy, and the world z-axis Wz, which intersect at a coordinate origin.

[0087] The goniometer 10 has a holding device 2 configured to receive and releasably secure a light source Q. For example, the holding device 2 can be designed as a holding plate 10.2, preferably as a perforated plate. The holding plate 10.2 is connected to the stand 10.S via a stand arm 10.1.

[0088] The stand arm 10.1 is pivotable about a vertical rotation axis 10.V relative to the stand 10.S. Furthermore, the stand arm 10.1 has a rotating device (not shown in detail), by means of which the holding plate 10.2 arranged thereon can be rotated about a horizontal rotation axis 10.H fixed to the stand arm 10.1, which is oriented orthogonally to the vertical rotation axis 10.V and intersects it at a rotation center 10.D.

[0089] The holding plate 10.2 is also displaceable along three mutually orthogonal translation axes 10.X, 10.Y and 10.Z relative to the stand arm 10.1 such that an optical center or another reference point of a light source held by the holding plate 10.2 is brought into the rotation center 10.D.

[0090] This allows the light source Q to be pivoted about the rotation axes 10.H, 10.V in the rotation center 10.D. The light source Q is pivoted such that the luminous flux emitted by the light source Q falls at least partially onto a medium M, which may be diffusely reflective or scattering. There, the luminous flux generates an illuminance, resulting in a luminance of the medium M, which can be measured with image resolution using a luminance measuring camera 4.

[0091] The position and orientation of the luminance measuring camera 4 and also of the medium M are known relative to each other and to the world coordinate system W and are fixed during the measurement of the light source Q. If the position and orientation of the light source Q in the world coordinate system W are also known, a partial luminous intensity distribution body can be determined from the image-resolved measured luminance of the medium M, which indicates the luminous intensity distribution emitted by the light source Q as a function of a radiation angle.

[0092] The determination of the partial luminous intensity distribution body is limited to the solid angle range under which light emitted by the light source Q hits the medium M.

[0093] By rotating the light source Q around the rotation axes 10.H, 10.V in the rotation center 10.D, a plurality of partial luminous intensity distribution bodies can be recorded and from this a luminous intensity distribution body can be determined which covers a larger solid angle range for the radiation angles than the individual partial luminous intensity distribution bodies.

[0094] According to the state of the art, the determination of the position and orientation of the light source Q is limited by the positioning and orientation errors propagating along the kinematic chain from the base 10.F to the support plate 10.2 with the rigidly connected light source Q. Furthermore, the determination of the position and orientation of the light source Q is limited by unknown deviations from the model assumption, for example, due to insufficient mechanical rigidity of the stand arm 10.2.

[0095] Therefore, a determination of the position and orientation of the light source Q according to the state of the art requires high-precision sensors along the kinematic chain, in this case high-precision sensors for detecting the displacement of the holding plate 10.2 relative to the tripod arm 10.1 along the translation axes 10.X, 10.Y, 10.Z and for detecting the angles of rotation about the rotation axes 10.V and 10.H and even then is only possible with limited accuracy, for example due to the deflection of the tripod boom coaxial with the first translation axis 10.X.

[0096] Therefore, there is a need for a device and a method with which a luminous intensity distribution body of a light source Q can be determined, which is movable along a kinematic chain relative to the world coordinate system W, without disturbances and measurement errors along the kinematic chain limiting the accuracy and reliability of the determined luminous intensity distribution body.

[0097] Figure 2 shows a further positioning device 1, which is designed, for example, as an industrial robot 100. The industrial robot 100 has a holding device 2 arranged at the free end of an arm segment 100.1.

[0098] The holding device 2 is preferably designed as a platform with various fastening options, for example, a perforated grid plate or as a mounting frame, and is configured to receive and hold an object, preferably a light source Q. Particularly preferably, the holding device 2 is configured to receive a spotlight 3.

[0099] Relative to the object held by the holding device 2, a Cartesian object coordinate system T is defined, which is determined by the object x-axis Tx, the object y-axis Ty, and the object z-axis Tz, which intersect at an object coordinate system origin TO. For example, if the held object is a light source Q, the object coordinate system T can be determined by a lighting reference point and a lighting reference axis.

[0100] The industrial robot 100 has a plurality of joint axes G around which a single arm segment 100.1 rotates or around which two interconnected arm segments 100.1 can be rotated relative to one another. By rotating around the joint axes G, the holding device 2 can be moved in a Cartesian world coordinate system W. Furthermore, by rotating around the joint axes G, the holding device 2 can be rotated relative to the world coordinate system W along at least one axis. Preferably, the industrial robot 100 is designed such that a headlight 3 held by the holding device 2 can be pivoted independently around a pivot point along two axes and can be displaced relative to this pivot point.

[0101] In other words: by rotation about the joint axes G, a change in the object coordinate system T relative to the world coordinate system W is caused along a kinematic chain from a foot 100.F of the industrial robot 100, which is stationary in the world coordinate system W, to the holding device 2. The kinematic chain is determined by the relative rotation angles of arm segments 100.1, which are each connected to a joint axis G via a joint.

[0102] An industrial robot 100 has a particularly large number of degrees of freedom and is particularly flexible in its movement and programming. However, instead of an industrial robot 100, any other type of movable positioning device 1 can be used that has a holding device 2 and enables the spatial repositioning of an object to be measured held thereby. In particular, goniometers 10 in the form shown in Figure 1shown design can be used.

[0103] If a light source Q held by the holding device 2, for example a spotlight 3, is measured by a measuring device that is fixedly arranged relative to the world coordinate system W, it is necessary to determine the position and orientation of the object coordinate system T relative to the world coordinate system W in order to classify the measurements of the measuring device. The measuring device is configured to determine the luminous intensity distribution body of the light source Q over at least a partial range of the radiation solid angle. Preferably, the measuring device is configured to indirectly determine at least one partial luminous intensity distribution body.

[0104] In the present embodiment, the measuring device comprises a luminance measuring camera 4, which is configured to detect at least one photometric parameter, and a medium M.

[0105] By means of the industrial robot 100, the spotlight 3 is aligned and positioned such that the luminous flux emitted by it at least partially hits the medium M.

[0106] The medium M can be designed as a diffusely and spectrally neutrally reflecting surface. In this case, the luminance measuring camera 4 is arranged in the same half-space as the spotlight 3 with respect to the medium M and is configured to record the light diffusely reflected by the medium M. The reflecting surface can be flat (plane) or curved, for example, spherical.

[0107] The medium M can also be designed as a diffuser. In this case, the luminance measuring camera 4 is arranged opposite the spotlight 3 with respect to the medium M and is configured to record the light scattered by the medium M.

[0108] The arrangement and orientation of the luminance measuring camera 4 and the medium M relative to each other and relative to the world coordinate system W are known or are recorded.

[0109] In order to assign the photometric parameter (e.g., luminance) recorded pixel by pixel in a pixel coordinate system using the luminance measuring camera 4, it is therefore necessary and sufficient to determine the position and orientation of the object coordinate system T relative to the world coordinate system W. The position of the object coordinate system T is determined by the position of the object coordinate system origin TO, specified in coordinate values ​​of the world coordinate system W. The orientation of the object coordinate system T is determined by the position of at least one axis Tx, Ty, Tz, specified as a direction vector in coordinate values ​​of the world coordinate system W.

[0110] According to the prior art, the position and orientation of the object coordinate system T relative to the world coordinate system W is determined by detecting the angles of rotation along the joint axes G of the industrial robot 100 and inserting them into a mechanical motion model of the industrial robot 100, which describes the kinematic chain between the foot 100.F and the holding device 2. In the prior art, the angles of rotation are detected by angle of rotation encoders, for example, rotary incremental encoders.

[0111] In contrast, the invention proposes to determine the position and orientation of the object coordinate system T relative to the world coordinate system W by direct referencing in the world coordinate system W without reference to the kinematic chain, wherein in a first step the position of the object coordinate system origin TO is determined as a point in coordinate values ​​of the world coordinate system W by direct referencing and in a second step the orientation of the object coordinate system T is determined as a direction vector in coordinate values ​​of the world coordinate system W by direct referencing.

[0112] An advantage of the method according to the invention is that the effort required to prevent or correct inherent deformations of a positioning device 1 can be significantly reduced compared to the prior art. In particular, the requirements for the mechanical rigidity of elements of the positioning device 1 that are moved relative to one another along the kinematic chain can be relaxed. This allows for cost, space, and weight savings on a positioning device 1.

[0113] Furthermore, the method according to the invention eliminates the need for position sensors arranged on the output side for precise determination of the relative position of all elements of a positioning device 1 that are linked along the kinematic chain and move relative to one another. This reduces the costs and design effort for such a positioning device 1.

[0114] First, the Figures 2 and 3 Examples of how to determine the position of the object coordinate system origin TO are explained.

[0115] Subsequently, based on the Figures 4 and 5 Examples of how to determine the orientation of the object coordinate system T are explained.

[0116] The exemplary embodiments for determining the orientation of the object coordinate system T and for determining the position of the object coordinate system origin TO are explained separately for the sake of clarity. Preferred embodiments of the invention comprise features of both at least one exemplary embodiment for determining the orientation of the object coordinate system T and at least one exemplary embodiment for determining the position of the object coordinate system origin TO.

[0117] Figure 2shows an embodiment in which a referencing of the object coordinate system T is carried out by arranging measuring marks 5 on the headlight 3 held in the holding device 2, thus being fixed in position to the object coordinate system T.

[0118] The measurement marks 5 can be configured as passive measurement marks 5. For example, passive measurement marks 5 can be formed by structures already present on the headlight 3 (or another light source Q to be measured), such as edges, corners, or prints. Passive measurement marks can also be formed by stickers affixed to the headlight 3 with optically easily recognizable, sharply defined, and high-contrast structures, for example, with black-and-white printed QR codes or printed black-and-white contrasting circles or annuli.

[0119] Passive measurement marks 5 can also be three-dimensional, for example, as spheres. Spherical passive measurement marks 5 have the advantage that they are recorded with a circular contour without distortion, regardless of the viewing angle. This enables particularly high precision in the localization of spherical passive measurement marks 5 in a camera image.

[0120] The measuring marks 5 can alternatively or additionally also be designed as active measuring marks 5 which emit light in the visible or non-visible wavelength range, which can be recorded by a referencing camera 601 to 603.

[0121] Such active measuring marks 5 have a unique structure, for example a circular light exit limited by an aperture, a spherical structure, a point-like structure with a very narrowly defined light exit or an approximately direction-independent radiation characteristic, which can be achieved for example by means of a diffuser or a frosted spherical surface.

[0122] Preferably, detection and assignment of active measurement marks 5 in an image is improved and facilitated by selecting the spectral characteristics of the emitted light so that they are clearly and clearly distinguishable from the light emitted by the light source Q to be measured, for example, by the headlight 3. Spectral separation can be achieved, for example, by means of a wavelength-dependent beam splitter or by means of a spectral filter arranged in front of a referencing camera 601 to 603.

[0123] Detection and assignment of active measuring marks 5 can further be improved and facilitated by temporally modulating, for example scanning, the emission of light by the active measuring marks 5.

[0124] In the environment of the industrial robot 100, three referencing cameras 601, 602, 603 are arranged in a fixed position relative to the world coordinate system W such that in a target measuring position P1 of the object coordinate system origin TO, each measuring mark 5 is detected by a plurality of referencing cameras 601 to 603.

[0125] The referencing cameras 601 to 603 are known in their poses—that is, the location of their respective capture plane and the orientation of their respective optical axes—relative to the world coordinate system W and are stable during the measurement of the headlight 3. Furthermore, the referencing cameras 601 to 603 are known in their respective imaging properties. In particular, the respective main and distortion parameters of the referencing cameras 601 to 603 are known. Methods for determining the main and distortion parameters of cameras are known from the prior art.

[0126] The active and / or passive measuring marks 5 are designed such that they are clearly identifiable in an image recorded by a referencing camera 601 to 603 and have a sharp structure, for example a high spatial frequency and / or at least one sharp edge.

[0127] Furthermore, a calibration scale (not shown in detail), the length of which is known absolutely (in millimeters) along at least one dimension, is arranged so that it is visible to the referencing cameras 601 to 603. Such a calibration scale can be formed, for example, by a known (measured) distance between two measuring marks 5.

[0128] Since the measuring marks 5 are arranged in a fixed position in the object coordinate system T and the referencing cameras 601 to 603 are arranged in a fixed position in the world coordinate system W, the position of this measuring mark 5 with respect to the world coordinate system W can be determined by triangulation by comparing the position of the image of a measuring mark 5 in an image of a first referencing camera 601 with the position of the image of the same measuring mark 5 in an image of at least one further referencing camera 602, 603.

[0129] Methods for detecting the position of the image of a measuring mark 5 in a camera image and for triangulation, i.e., for determining a position of a measuring mark 5 in the world coordinate system W that corresponds to the positions of the images of this measuring mark 5 detected in the multiple camera images, are known from the prior art. In particular, methods of close-range photogrammetry are known.

[0130] If the target measuring position P1 is approximately reached by means of the rotary encoders assigned to the joint axes G, the measuring marks 5 are recorded by the referencing cameras 601, 602, 603, identified, and their position in the world coordinate system W is measured using a triangulation method. From the known position of the measuring marks 5 relative to the object coordinate system origin TO, the position of the object coordinate system origin TO in the world coordinate system W is determined.

[0131] Advantageously, a lack of rigidity (for example, deflection and / or twisting) of the arm segments 100.1, the inaccuracy of the rotation angle determination along the joint axes G and an inaccurate mechanical movement model of the industrial robot 100 do not affect the accuracy of the position determination of the object coordinate system origin TO relative to the world coordinate system W.

[0132] This makes it possible to use more cost-effective positioning devices 1 with lower accuracy requirements for measuring light sources Q, such as spotlights 3. It is only necessary to ensure the constancy of the position and / or orientation of the spotlight 3 held by the holding device 2 during the detection of a partial segment of a light distribution. For this purpose, cost-effective and reliable braking devices for industrial robots 100 are known and available.

[0133] In one embodiment of a method for measuring a headlight 3, the headlight 3 is first roughly pre-positioned at a target measurement position P1 by means of the industrial robot 100. The rough pre-positioning can be performed by evaluating the measured values ​​of the rotary encoders on the joint axes G.

[0134] The industrial robot 100 can then be controlled in such a way that the positional deviation of the actual measuring position P1' from the target measuring position P1 is reduced.

[0135] This procedure can be repeated, whereby the positional deviation of the actual measuring position P1' from the target measuring position P1 is iteratively reduced until a desired accuracy is achieved (i.e.: an upper limit for the positional deviation of the actual measuring position P1' from the target measuring position P1 is undershot).

[0136] Alternatively, it is also possible to maintain an achieved actual measurement position P1' even if it deviates from a target measurement position P1, and to take into account the positional deviation of the headlight 3 and thus also of the object coordinate system origin TO determined by evaluating the images recorded by the referencing cameras 601, 602 when evaluating the photometric parameter recorded in the pixel coordinate system with the luminance measuring camera 4.

[0137] Figure 3 shows an embodiment in which the position of the object coordinate system T is determined by two measuring marks 5 designed as marking discs 501, 502 being arranged on the holding device 2 of the industrial robot 100. Since the headlight 3 is fixed in the holding device 2 during the measuring process, the marking discs 501, 502 are arranged stationary relative to the object coordinate system T.

[0138] The marking discs 501, 502 have a high-contrast printed pattern, for example, in the manner of a target with concentric, alternating white and black circular rings and / or in the manner of crosshairs. The marking discs are not arranged coplanarly. Preferably, the marking discs 501, 502 are arranged orthogonally to one another.

[0139] In the environment of the industrial robot 100, two referencing cameras 601, 602 are arranged in a fixed position relative to the world coordinate system W such that, in a target measurement position P1 of the object coordinate system origin TO, each referencing camera 601, 602 detects an associated marking disc 501, 502. Preferably, the referencing cameras 601, 602 are arranged such that, in and near the target measurement position P1, the associated marking disc 501, 502 is approximately perpendicular, preferably at an angle of between 80° and 100°, relative to the optical axis of the referencing camera 601, 602.

[0140] If the target measuring position P1 is approximately reached by means of the rotary angle sensors assigned to the joint axes G, the marking discs 501, 502 are recorded and measured by the respectively assigned referencing camera 601, 602.

[0141] For example, the marking discs 501, 502 and the referencing cameras 601, 602 can be arranged such that, when the ideal target measurement position P1 is reached, a marking disc 501, 502 appears centrally in the pixel coordinate system of the associated referencing camera 601, 602. Thus, a deviation from the target measurement position P1 of the holding device 2 in all axes Wx, Wy, Wz of the world coordinate system W can be determined by determining the deviations from the central position of the marking disc 501, 502 in the pixel coordinate system of the respective referencing camera 601, 602 and transferring them to the world coordinate system W according to the image scale.

[0142] An advantage of this embodiment is that even very large deviations from the target measurement position P1 can be detected by selecting a sufficiently large image angle of the referencing cameras 601, 602. It is also possible to use differently designed marking discs 501, 502, for example, printed with different patterns, to avoid confusion of coordinates of the identified actual measurement position P1'.

[0143] Furthermore, it is also possible to use more than two referencing cameras 601, 602 and / or more than two marking discs 501, 502 in order to improve the accuracy and robustness of the position determination.

[0144] If they are differently designed, for example, printed with different patterns, several marking discs 501, 502 can be recorded together by a referencing camera 601, 602. By measuring the distance between the centers of the recorded marking discs 501, 502, it is possible, for example, to determine an angle of inclination of a straight line passing through the centers of the marking discs 501, 502 relative to the image plane of the referencing camera 601, 602.

[0145] Thus, in an embodiment not shown in detail, the position and orientation of the holding device 2 (and the object coordinate system T) relative to the world coordinate system W can be determined by three referencing cameras 601, 602 with pairs of vertically aligned image planes and a total of six marking discs 501, 502, two of which are arranged coplanar to an image plane of a respectively assigned referencing camera 601, 602.

[0146] In a further embodiment not shown in detail, the referencing cameras 601, 602 are replaced by clusters of light barriers formed by light sources and photosensors arranged opposite one another and fixed to the world coordinate system W. Marking discs 501, 502 or similarly designed, light-tight measuring marks 5 arranged rigidly on the holding device 2 interrupt one or more of these light barriers depending on their position and thus enable the position of the holding device 2 to be determined along a measuring direction that is perpendicular to one light barrier or perpendicular to several light barriers.

[0147] Figure 4 shows schematically an embodiment for determining the orientation of the object coordinate system T.

[0148] Referencing cameras 601, 602 are arranged on the holding device 2 of the industrial robot 100, fixed in position relative to the object coordinate system T. The referencing cameras 601, 602 are configured to record measurement marks 5, which are arranged in the environment of the industrial robot 100, fixed in position relative to the world coordinate system W.

[0149] The measuring marks 5 can be formed by existing, stationary, structured equipment elements of a measuring laboratory, for example, edges or corners of cabinets, measuring tables, ceiling lights or installations. The measuring marks 5 can be analogous to the Figure 3 illustrated embodiment can also be formed by specially arranged marking discs 501, 502 or similar high-contrast and structured markings.

[0150] The aperture angles of the referencing cameras 601, 602 are selected such that they capture at least one of the measuring marks 5 in every position and orientation of the holding device 2. Furthermore, the referencing cameras 601, 602 are arranged on the positioning device such that their respective optical axes can be changed by a movement of the industrial robot 100 relative to the world coordinate system W.

[0151] Preferably, the referencing cameras 601, 602 are arranged after the last movable link of the kinematic chain, for example in a fixed position and orientation relative to the holding device 2.

[0152] In a calibration phase, the surrounding space is completely scanned with the referencing cameras 601, 602. For each of the reference calibration cameras 601, 602, a correlation data set is created that relates each recorded image to a pose, i.e., to a position and an orientation, of the holding device 2 and thus also of the referencing cameras 601, 602.

[0153] In an analogous manner to the Figure 2 In the embodiment shown, the orientation of the object coordinate system T can be determined by measuring the pixel coordinates of the images of the measuring marks 5 in the images recorded by the referencing cameras 601, 602.

[0154] In a subsequent work phase, an image captured by a referencing camera 601, 602 is overlaid with at least one image of the stored correlation data set and the alignment of the optical axis of the respective referencing camera 601, 602 is determined therefrom.

[0155] The orientation of the object coordinate system T can thus be determined with just one referencing camera 601, 602, if its position, i.e. the position of the object coordinate system origin TO, has been determined beforehand, for example by means of Figure 3 already explained.

[0156] With a plurality of referencing cameras 601, 602, the position of the object coordinate system T can also be determined or checked from their determined optical axes by sectioning.

[0157] Figure 5shows an embodiment of the industrial robot 100, in which a pilot light source 7 with a main optical plane 7.1 is arranged stationary relative to the holding device 2, which projects a pattern into space along pilot rays X. The pose (position and orientation) of the pilot light source 7 relative to the spatial coordinate system T is known from the mounting of the pilot light source 7 on the holding device 2.

[0158] The pilot light source 7 can be designed, for example, as a diffractive optical element (DOE) and configured such that a dot matrix XR with dots XP is emitted into a subspace, for example, a half-space, approximately in a 1-degree grid, with each pilot beam X corresponding to a projection point XP of the dot matrix XR. The pilot light source 7 preferably emits in the non-visible and low-energy range.

[0159] A section of the dot matrix XR is captured by means of an optical capture device 20 arranged in a fixed position in a known position and orientation in the world coordinate system W, which in Figure 6 is shown. The collecting device 20 is arranged to collect at least one pilot beam X.

[0160] The collecting device 20 has a light-tight housing 20.1, on which a diaphragm tube 20.2 is arranged on the entrance side. The diaphragm tube 20.2 projects into the light-tight housing 20.1 and is closed at the end projecting into the housing 20.1 by a diffuse screen 20.3, onto which the at least one collected pilot beam X is projected as a projection point XP. The diaphragm tube 20.2 can be configured such that only a single pilot beam X is directed onto the screen 20.3 and thus only a single projection point XP is projected on the screen.

[0161] A capture camera 20.4 is arranged behind the screen 20.3 in the direction of the pilot beam X. The capture camera 20.4 captures an image of the screen 20.3 with at least one projection point XP projected onto it. The capture camera 20.4 can be designed as a luminance measuring camera 4.

[0162] A change in the orientation of the holding device 2 corresponds to a pivoting of the main plane 7.1 around a rotation center 7.2 at a horizontal angle ϕ and / or at a vertical angle θ. As a result, the pilot beam X is also pivoted by the horizontal angle ϕ and / or the vertical angle θ, and the corresponding projection point XP is moved accordingly in the horizontal and / or vertical direction on the screen 20.3.

[0163] The position of a point XP on the screen 20.3 is determined using the capture camera 20.4. The position of the center of rotation 7.2 of the principal plane 7.1 is known from the determination of the position of the object coordinate system T and from the known pose of the pilot light source 7 in this object coordinate system T. Thus, the horizontal angle ϕ can be determined from the horizontal position of a point XP, and the vertical angle θ from the vertical position of a point XP.

[0164] To avoid ambiguity in determining the angles ϕ and θ, at least one pilot beam X that strikes the screen 20.3 through the aperture tube 20.2 must be identified. For this purpose, the beam profiles of different pilot beams X, in particular neighboring pilot beams X, can be designed differently using a DOE. For example, different beam profiles can be designed such that neighboring points XP in the point matrix XR have different dimensions and / or different intensities and / or different structures when projected onto the screen 20.3 and can thus be distinguished using the capture camera 20.4.

[0165] Alternatively or additionally, the at least one pilot beam X which strikes the screen 20.3 through the aperture tube 20.2 can be identified by determining the orientation of the object coordinate system T roughly, i.e. with the resolution of the solid angle grid in which the pilot beams X diverge.

[0166] Such a rough determination of the orientation of the object coordinate system T, for example with a resolution of one degree, is possible by simple sensors on the joint axes G of the industrial robot 100. Alternatively or additionally, a rough determination of the orientation can be carried out by measuring the position of a plurality of measuring marks 5 according to one of the Figures 2 or 3 explained procedure.

[0167] Starting from such a rough orientation determination, which only has to be sufficient to identify the at least one point XP captured on the screen 20.3 from the point matrix XR, by determining the position of this at least one point XP by means of the capture camera 20.4, a determination of the angles ϕ and θ that is improved by orders of magnitude is possible, for example with a resolution of 1 / 100 degree to 1 / 1000 degree.

[0168] In another, in Figure 7 In the schematically illustrated embodiment, an incremental change in the orientation and / or position of the headlight 3 held by the industrial robot 100 is determined by registering luminance measurement images 81 to 85. In the present case, the headlight 3 is designed as a vehicle headlight 3.

[0169] For this purpose, by rotating about at least one joint axis G of the industrial robot 100, a first to fifth target measuring position P1 to P5 is successively approached. The first to fifth actual measuring position P1' to P5' actually reached in each case are approximately determined by means of the rotary angle encoders (not shown in detail) which are assigned to the joint axes of the industrial robot 100. Alternatively or additionally, the first to fifth actual measuring position P1' can also be determined by an embodiment of the method described with reference to Figure 1 to Figure 4 described procedure.

[0170] In the first to fifth actual measuring positions P1` to P5', a first to fifth luminance measurement image 81 to 85 of the switched-on vehicle headlight 3 is recorded with the luminance measurement camera 4, which in Figure 8 are shown schematically.

[0171] The first to fifth target measuring positions P1 to P5 are set up and arranged in such a way that the corresponding luminance measurement images 81 to 85 have an overlap sufficient for image registration, at least in pairs, even taking into account the maximum possible deviations of the actual measuring positions P1' to P5' when approaching the target measuring positions P1 to P5.

[0172] In other words: even with the most unfavorable arrangement of the actual measurement positions P1' to P5', within the scope of the positioning tolerance possible, for example, due to the inaccuracy of the rotary encoders on the joint axes G and / or the inherent deformation of the arm segments 100.1 of the industrial robot 100, the luminance measurement images 81 to 85 have an overlap sufficient for image registration.

[0173] Image registration methods in which offset and / or distorted intensity images (e.g., grayscale or color images) are superimposed are known from the prior art, for example, from the publication B. Zitova, J. Flusser: Image registration methods: a survey, Elsevier. Image and Vision Computing, Vol. 21, 2003, pp. 977-1000. It is also known how large the overlap required for image registration must be, depending, for example, on the structure, contrast, or distortion of the intensity images.

[0174] For example, the first to fifth target measurement positions P1 to P5 are arranged and configured such that the first luminance measurement image 81 assigned to the first target measurement position P1, as an anchor image, has an overlap with each further luminance measurement image 82 to 85 sufficient for image registration.

[0175] However, it is also possible that a plurality of target measurement positions P1 to P5 are set up in such a way that the associated luminance measurement images 81 to 85 are arranged in stripes.

[0176] Any other, planar arrangement of the luminance measurement images 81 to 85 can also be achieved by arranging and setting up the corresponding target measurement positions P1 to P5, if each luminance measurement image 81 to 85 is connected in an overlapping manner to every other luminance measurement image 81 to 85 via at least one overlap path, wherein along an overlap path of luminance measurement images 81 to 85, two adjacent luminance measurement images 81 to 85 (i.e.: predecessor and successor in the overlap path) have an overlap sufficient for image registration, wherein the overlap must also be sufficient for image registration if the respective actually achieved actual measurement position P1` to P5' deviates from the assigned target measurement position P1 to P5 to a maximum of unfavorable within the framework of the positioning accuracy of the industrial robot 100.

[0177] An advantage of this embodiment is that the luminance distribution generated by a vehicle headlight 3 can be recorded over a large area, in principle over any desired extent, in particular extending beyond the recording range of a single luminance measurement image 81 to 85 of the luminance measurement camera 4, wherein only low demands are placed on the positioning accuracy of the industrial robot 100, in particular on its mechanical rigidity and on the accuracy of its position or angle sensors. LIST OF REFERENCE SYMBOLS

[0178] 1Positioning device 100Industrial robot, positioning device 100.1Arm segment 2Holding device 3Headlight, vehicle headlight 4Luminance measuring camera 5Measuring mark 501, 502Marking disc, measuring mark 6Reference instrument 601, 602, 603Reference instrument, referencing camera 7Pilot light source 7.1Main plane 7.2Center of rotation 81 to 85First to fifth luminance measurement image 10Goniometer, positioning device 10.1Tripod arm 10.2Holding plate, holding device 10.DCenter of rotation 10.FFoot 10.STripod 10.X, 10.Y, 10.ZFirst, second, third translation axes 10.H, 10.VHorizontal, vertical rotation axes 20Collecting device 20.1Housing 20.2Aperture tube 20.3Screen 20.4Collection camera ϕ ϕhorizontal angle θ θvertical angle MMedium, collecting plane, measuring surface GGarticulation axis P1 (first) target measuring position P1' (first) actual measuring position P2 to P5 second to fifth target measuring position P2` to P5' second to fifth actual measuring position QLight source TObject coordinate system T.OObject coordinate system origin T.xObject x-axis T.yObject y-axis T.yObject y-axis WWorld coordinate system W.xWorld x-axis W.yWorld y-axis W.yWorld y-axis XPilot beam X.RProjection matrix, point matrix X.PProjection structure, projection point

Claims

1. Method for photometrically measuring a light source (Q, 3) clamped into a positioning device (1), which comprises an object coordinate system (T), by means of a luminance measurement camera (4) arranged fixedly relative to a world coordinate system (W), wherein the light source (Q, 3) is moved between a first current measurement position (P1') and at least one further current measurement position (P2' to P5') along a kinematic chain of the positioning device (1) in the world coordinate system (W), wherein, with the light source (Q, 3) switched on, a luminance measurement image (81 to 85) is recorded at each current measurement position (P1' to P5') by means of the luminance measurement camera (4), the image describing the spatial distribution of a photometric characteristic in a measurement area (M), wherein the location and / or the orientation of the object coordinate system (T) relative to the world coordinate system (W) is captured at each current measurement position (P1' to P5') in direct relationship with the world coordinate system (W) without reference to the kinematic chain of the positioning device (1) with a capturing tolerance which, in terms of at least one parameter, is smaller than the assured positioning tolerance of the positioning device (1), wherein the capturing tolerance indicates the maximum deviation of the actual location and / or orientation of the object coordinate system from the captured location and / or orientation of the object coordinate system relative to the world coordinate system, and wherein the assured positioning tolerance is determined as the maximum deviation of a current measurement position (P1' to P5') that is actually approached from a specified target measurement position (P1 to P5), and wherein a necessary positioning tolerance of the positioning device (1) is ascertained and a positioning device (1) having a positioning tolerance which is smaller than or preferably identical to the ascertained necessary positioning tolerance is selected, wherein the necessary positioning tolerance is ascertained such that a sequence of target measurement positions (P1 to P5) can be arranged and approached such that complete capturing of the photometric characteristic in the measurement area is possible with the assigned sequence of actually reached current measurement positions (P1' to P5') located in each case within the positioning tolerance around a target measurement position (P1 to P5).

2. Method according to Claim 1, characterized in that the measurement area (M) is formed by a medium (M) which is configured for diffuse reflection and / or scattering of the light emitted by the light source (Q, 3) and which is arranged in a fixed location and orientation relative to the world coordinate system (W), is illuminated by the light source (Q, 3) and is recorded by the luminance measurement camera (4).

3. Method according to either of the preceding claims, characterized in that the luminance measurement camera (4) captures the light source (Q, 3) in a direct beam path, wherein the measurement area (M) is arranged on a surface of the light source (Q, 3) facing the luminance measurement camera (4).

4. Method according to any of the preceding claims, characterized in that the light source (Q, 3) is pivoted about at least one axis extending through a centre of rotation (10.D, 7.2).

5. Method according to any of the preceding claims, characterized in that, in a first step, the location of the object coordinate system (T) relative to the world coordinate system (W) is ascertained by directly sampling at least one measurement mark (5, 501, 502) and, in a second step, the orientation of the object coordinate system (T) relative to the world coordinate system (W) is determined.

6. Method according to any of the preceding claims, characterized in that the location and / or the orientation of the object coordinate system (T) is determined by capturing at least one measurement mark (5, 501, 502) by means of in each case at least one referencing camera (601, 602)7. Method according to Claim 6, characterized in that at least one referencing camera (601, 602) is arranged fixedly with respect to the world coordinate system (W) and at least one measurement mark (5, 501, 502) is arranged fixedly with respect to the object coordinate system (T).

8. Method according to Claim 6 or 7, characterized in that at least one referencing camera (601, 602) is arranged fixedly with respect to the object coordinate system (T) and at least one measurement mark (5, 501, 502) is arranged fixedly with respect to the world coordinate system (W).

9. Method according to any of Claims 6 to 8, characterized in that at least one measurement mark (5, 501, 502) is set up as an active measurement mark (5) for emitting radiation which is detectable by at least one assigned referencing camera (601, 602).

10. Method according to any of the preceding claims, characterized in that at least one receiving plane (20.3, M) is arranged fixedly in the world coordinate system (W), the location of the object coordinate system (T) in the world coordinate system (W) is determined and the respective orientation of the object coordinate system (T) is ascertained for each location from the measurement of modulated illumination that is emitted in the known direction relative to the object coordinate system (T) and received on the at least one receiving plane (20.3, M).

11. Method according to Claim 10, characterized in that the modulated illumination is generated by means of a diffractive optical element as a projection matrix (X.R), which comprises at least one projection structure (X.P) which projects along a respective pilot beam (X) onto a receiving plane (20.3, M).

12. Method according to Claim 10, characterized in that the modulated illumination is emitted by the light source (Q, 13), wherein current measurement positions (P1' to P5') are approached which each lie within a predetermined distance around a target measurement position (P1 to P5), wherein in each case at least one luminance measurement image (81 to 85) is recorded at each current measurement position (P1' to P5'), wherein the target measurement positions (P1 to P5) are selected such that at least two luminance measurement images (81 to 85) overlap and wherein the offset between mutually overlapping luminance measurement images (81 to 85) is ascertained by means of an image registration method and the respective orientation of the object coordinate system (T) is ascertained therefrom and from the current measurement positions (P 1' to P5') in each case assigned to the luminance measurement images (81 to 85).

13. Method according to any of the preceding claims, characterized in that in each case one target measurement position (P1 to P5) is determined for each current measurement position (P1' to P5') by evaluating parameters of the positioning device (1), and the location and orientation of the object coordinate system (T) are captured proceeding from the target measurement position (P1 to P5).

14. Method according to Claim 13, characterized in that the positioning device (1) is controlled for approaching a target measurement position (P1 to P5) in each case such that a current measurement position (P1' to P5') within a predetermined distance from the respectively assigned target measurement position (P1 to P5) is reached.

15. Use of a method according to any of the preceding claims for photometrically measuring a headlamp (3).

16. Use according to Claim 15, characterized in that a vehicle headlamp (3) is photometrically measured.