Determining optical properties of a transparent object

Abstract

The invention relates to a measuring device (1), a system, a measuring method, and a computer program (5) for determining optical properties of a transparent object (8). In order to be able to determine optical properties of a transparent object (8) in a particularly simple manner, a measuring method is proposed comprising the following steps: capturing images (30, 31, 32) of a test pattern (3) during a capturing process, wherein the capturing process comprises capturing test patterns (21, 22) of the object (8) imaged at at least two different positions (11, 12) of the object (8), wherein the distances of the object positions (11, 12) from one another are known and wherein the relative positions of the image capturing devices (10) from one another and from the display device (2) are unchanged during the capturing process, and determining optical properties of the object (8) during a determination process without knowledge of the geometric shape, the position, and the orientation of the object (8) from the images (30, 31, 32) of the test pattern (3) captured during the capturing process, by comparing with one another test patterns (20, 21, 22) captured during the capturing process.

Description

[0001] Description

[0002] Determining optical properties of a transparent object

[0003] The invention relates to a measuring device, a system, a measuring method and a computer program for determining optical properties of a transparent object.

[0004] Determining the refractive power of eyeglasses is a standard task in ophthalmic practice. Typically, eyeglasses of unknown prescription are measured manually using a so-called lensmeter. When the lenses are not relatively simple single-vision lenses, but modern progressive lenses, the operation is difficult, and the results are unreliable, as they also depend on the skill of the operator.

[0005] Progressive lenses, which today represent the standard care for older patients, are lenses with a location-dependent refractive power that typically have a distance part in the upper area of ​​the lens and a near part (reading part) in the lower area. In the transition zone between the distance and near parts, aberrations occur inherently, and lens manufacturers try to counteract these with a variety of lens designs. However, it has become apparent that not every patient is able to cope with every lens design, so that the cause of dissatisfaction often has to be determined in the optician's practice. One possible cause is faulty manufacturing of the glasses. For example, the position of the distance reference point and the near reference point must be adapted to the position of the patient's pupils.There is therefore a need to be able to determine the optical properties of spectacles in a simple manner and to relate these properties to the patient. Attempts are being made to achieve these goals using modern measuring devices and methods. While simple lens measuring devices only allow point-by-point measurements, more advanced devices that work on the basis of wavefront measurements already enable the distribution of refractive power over a limited part of the lens area. The disadvantage, however, is that for technical and optical reasons this is not possible over the entire surface and particularly not when the spectacles are in the wearing position. Thus, the solutions known to date only allow measurements in a limited part of the entire surface, determined by the maximum aperture of the sensors used.In addition, the determination of far and especially near points fails due to the lack of recording of the global properties of the lenses.

[0006] An object of the present invention is to provide a technique with which the optical properties of a transparent object, in particular its refractive effect, can be determined in a particularly simple manner.

[0007] This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are specified in the subclaims or emerge from the following description and / or the accompanying figures.

[0008] The measuring device according to the invention for determining optical properties of a transparent object comprises a display device for displaying a test pattern, a number of image capture devices for capturing images of the test pattern, wherein the image capture devices capture test patterns imaged by the object at at least two different positions of the object during a capturing process, wherein the distances between the object positions are known and wherein the relative positions of the image capture devices to each other and to the display device are unchanged during the capturing process, and a computer unit with a computer program for determining optical properties of the object, which computer program during a determination process without knowledge of the geometric shape,the position and orientation of the object from the images of the test pattern captured by the image capture devices during the capture process, the optical properties of the object are determined by comparing the test patterns captured during the capture process.

[0009] The system according to the invention for determining optical properties of a transparent object comprises such a measuring device and a transparent object positioned between the display device and the number of image capture devices.

[0010] The measuring method according to the invention for determining optical properties of a transparent object comprises the following steps: a) capturing images of a test pattern during a capturing process, wherein the capturing process comprises capturing test patterns imaged by the object at at least two different positions of the object, wherein the distances between the object positions are known and wherein the relative positions of the image capturing devices to one another and to the display device are unchanged during the capturing process, and b) determining optical properties of the object during a determination process without knowledge of the geometric shape, the position and the orientation of the object from the images of the test pattern captured during the capturing process, by comparing test patterns captured during the capturing process with one another.

[0011] The computer program according to the invention comprises computer program instructions which, when the program is executed by a computer unit, cause the computer unit to carry out the determination step of the above-mentioned method.

[0012] The advantages and embodiments explained below in connection with the device according to the invention also apply mutatis mutandis to the system according to the invention, the method according to the invention and the computer program according to the invention and vice versa.

[0013] The invention uses the principle of photogrammetry and is based on the application of the principle of transmitted light deflectometry (transmission deflectometry). The object to be measured forms a test pattern. Refraction on the surface of a transparent object causes a shift and / or distortion of the imaged pattern, which depends on the object geometry. The deflection of the transmitted light can be used to determine the optical properties of the object, in particular its refractive power. The deflection of the transmitted light is therefore measured. For this purpose, the imaged pattern is recorded by suitable image capture devices, for example digital cameras.From the changes in the detected pattern, for example in the form of displacements and / or distortions, optical properties of the object are determined, such as the local refractive power, the local inclination of the surface or the local prismatic effect. Preferably, at least one refractive power distribution is determined from the local pattern changes. The invention can be used in particular to determine optical properties of thin, transparent objects. In other words, the object to be measured is preferably a thin optical element. This is understood here in particular to mean an optical element which, with regard to its optical effect, can be represented by a main surface. In the case of thin optical elements, optical properties can be determined particularly easily with the aid of the invention.However, the invention can also be used in principle with other objects, in particular with optical elements in which the distance between the main surfaces is significantly smaller than the measuring distance, and with optical elements that behave only approximately like a thin optical element or whose optical behavior can be at least approximately represented by a single main surface. The object is at least transparent enough to allow sufficient light transmission through the object for measurement.

[0014] The test pattern used can be any arrangement of any number of virtually any pattern elements. Suitable pattern elements include points, lines, or other elements that can be represented in isolation from one another.

[0015] With the aid of the invention, optical elements can be measured quickly and over their entire area in transmission, in particular to determine their optical properties, in particular their local refractive power. The invention can be applied to a wide variety of optical elements. The invention is particularly advantageously used in spectacles, in particular progressive lenses. More precisely, the optical element to be examined in this case is formed by the spectacle lenses mounted in the frame of a spectacle. In simple terms, the measurement object is a mounted pair of spectacles. However, the invention can also be used with a single spectacle lens as the measurement object. For the sake of simplicity, the term spectacles will be used below. In this case, spectacles are an example of an intentionally refracting optical element which is intended to achieve a defined optical, in particular refractive, effect.The invention can also be used particularly advantageously in vehicle windows, in particular windshields. A windshield is an example of an unintentionally refracting optical element which is not intended to have any optical, in particular no refractive, effect. In all cases, the invention is based on detecting local changes in the direction of the beam caused by the optical element and using them to evaluate the optical effect and thus the quality of the optical elements. In the case of spectacles, the aim of testing the optical properties is to identify the properties of the spectacle lenses mentioned above which are important for the optician. For windshields, the measurement of the local refractive power is prescribed for safety reasons.The aim of testing optical properties here is to check optical homogeneity, in particular to detect defects and optical irregularities, such as streaks, refractive index jumps and the like.

[0016] The technical solution according to the invention is characterized in that any transparent objects, in particular thin transparent objects, can be measured. Several objects can also be measured simultaneously. If the object is a pair of spectacles, both lenses can be examined simultaneously. The technical solution according to the invention is characterized in that the optical properties can be recorded over the entire surface of the object. In particular, the invention enables the local refractive powers to be determined over essentially the entire aperture of an optical element (full-surface refractive power distribution), for example a spectacle lens, whereas with the methods known from the prior art it is often not possible, due to process reasons, to record the entire spectacle lens as the measuring surface.

[0017] The technical solution according to the invention is characterized by the fact that the detection of the optical properties is independent of the optical power of the object. In particular, the material of the object being measured or its refractive power does not need to be known. If the object is a pair of glasses, the type of lenses (monofocal, multifocal, progressive) does not need to be taken into account.

[0018] The technical solution according to the invention is characterized by the fact that the optical properties can be determined without knowledge of the object's geometric parameters, solely by using its optical power. In other words, the geometric properties of the object (outer contour, radii of curvature, thickness) do not need to be known to determine the object's optical properties. In particular, the geometric shape of the object's optically effective surfaces does not need to be known to determine the object's refractive power.

[0019] The technical solution according to the invention is characterized in that the measurement result depends neither on the measurement position (the exact location) of the object nor on its orientation. Therefore, neither needs to be known. The object position is understood to be the position of the measurement object in the measurement field. The object can be located at any distance between the display device and the image capture devices. For the inventive determination of the optical properties of the object, only the displacement of the measurement object between the object positions at which the images are captured needs to be known. In other words, only the distances between the object positions need to be known, in the simplest case, the difference between the object positions along the optical axis (z-axis). Also, no markings on the object or further information are required for the measurement.In particular, no further information is determined apart from the captured images of the test pattern.

[0020] If the object to be examined is a pair of glasses, the invention makes it possible to take a measurement in the position in which the glasses are actually used, i.e. in the position in which the lenses are actually used.

[0021] The invention relates to the measurement of the refractive power of optical elements, in particular to the distribution of the refractive power across the entire aperture of the element. The invention allows a spatially resolved refractive power distribution of an optical element to be determined in a particularly simple manner.

[0022] If the object is a pair of spectacles, the invention enables a particularly simple representation of the actual refractive power distribution and the determination of characteristic points in the spectacle lens in relation to the edge, e.g. distance and near points. This can provide the optician with crucial information on the cause of customer dissatisfaction. At the same time, the optician is given a measuring method which, for the purposes of quality control, can record, quantify and display the achieved position and orientation of the spectacle lens in relation to the determined, frame-specific fitting points measured on the patient. In particular, the position of the near and far points in relation to the determined edge can be determined and displayed.At the same time, the respective local refractive powers and, if necessary, other parameters at these points can be determined, displayed and compared with a design value of the respective spectacle lenses (“prescription”).

[0023] According to a preferred embodiment of the invention, the measuring device comprises a positioning device for achieving a different positioning of the object between the display device and the image capture devices. At the same time, the computer program is preferably designed such that it controls the positioning device for the different positioning of the object during the capture process.

[0024] According to a preferred embodiment of the invention, the image capture devices are designed such that, during the capture process, they capture a reference test pattern displayed by the display device, unchanged, i.e., not altered by the object. This capture serves as a blank measurement for calibrating the determination process. The number of image capture devices depends on the number of objects to be measured. The display device is advantageously an electronic display so that, if necessary, the number, arrangement, and shape of the displayed pattern elements can be easily changed.According to a preferred embodiment of the invention, the computer program is designed such that during the determination process it determines the local pattern changes for a number of object positions, preferably for each object position, namely the changes in the test pattern imaged by the object compared to the reference test pattern as a comparison test pattern.

[0025] According to a preferred embodiment of the invention, the computer program is designed in such a way that, during the determination process, for a number of object positions, preferably for each object position, changes in a test pattern that is imaged by the object arranged in a first object position compared to a number of other test patterns as comparison test patterns, it determines which other test patterns are imaged by the object when the object is in object positions that differ from the first object position.

[0026] According to a preferred embodiment of the invention, the computer program is designed in such a way that, during the determination process, it determines changes in the test pattern imaged by the object compared to a comparison test pattern, preferably exclusively within an edge boundary of the object.

[0027] According to a preferred embodiment of the invention, the computer program is designed such that, during the determination process, it determines changes in the test pattern imaged by the object compared to a comparison test pattern for a plurality of image groups, each image group being formed by a neighborhood of images of individual pattern elements of the test pattern and each image group representing a surface element of the object, i.e. an element of the main surface of the object. An image group can in particular be formed by an NxN neighborhood, for example a 2x2, 3x3 or 4x4 neighborhood, each neighborhood having an actual center point formed by a pattern element or a virtual center point.This means that the changes are not determined for individual pattern elements of the test pattern, i.e. individual pattern elements are not compared, but that the changes are always determined based on a group of pattern elements (mapping group) in the test pattern mapped by the object. The number of neighborhoods therefore determines the number of data points for the subsequent evaluation. The changes are determined for a large number of such neighborhoods. In other words, it is not the distortion and / or displacement of individual pattern elements of the test pattern that is examined, but the change in the placement of the pattern elements of the test pattern and thus the distortion and / or displacement of the test pattern.

[0028] By considering neighborhoods, i.e., areas of adjacent pattern elements, the problem of the limited resolution of the measurement method is solved. According to a further preferred embodiment of the invention, the resolution is further improved by evaluating the placement of pattern elements in overlapping image groups.

[0029] For each image group (neighborhood) of at least 2x2 pattern elements, a local affine transformation between the original image (test pattern) and the image (image of the original image using an optical element) can be calculated, which mathematically approximates the local optical effect. According to a preferred embodiment of the invention, the computer program is designed in such a way that, during the determination process, it determines a local affine transformation matrix for each pair of test patterns to be compared for a number of the surface elements considered, for a number of the image groups considered, preferably for each image group. Each pair of test patterns consists on the one hand of an image imaged by the object from an object position, i.e.a test pattern changed by the object and, on the other hand, a comparison test pattern, where the comparison test pattern is the unchanged reference test pattern or a test pattern imaged by the object from a different object position. If a comparison is made between an imaged test pattern and the reference test pattern, the transformation matrix converts the reference test pattern representing the unchanged initial state into the test pattern imaged by the object representing the changed state. If a comparison is made between two imaged test patterns created from different object positions, the transformation matrix converts a first test pattern, which is imaged by the object arranged in a first object position, into another test pattern, which is imaged by the object when the object is in an object position different from the first object position.

[0030] According to a preferred embodiment of the invention , the computer program is designed in such a way that during the determination process for at least one imaging group , preferably for each imaging group , it determines from the transformation matrices determined for this imaging group the principal axis directions and the scalings along the two principal axes and from these the local refractive power of the image generated by this

[0031] Determines the area element represented by the mapping group.

[0032] According to a preferred embodiment of the invention, the computer program is designed in such a way that, during the determination process, it determines for at least one image group, preferably for each image group, from the transformation matrices determined for this image group, the local translations and from these the local prism of the surface element represented by this image group.

[0033] According to a preferred embodiment of the invention, the computer program is designed such that, following the determination process, it generates a refractive index map of the object using at least one of the determined optical properties of the transparent object. Preferably, the computer program generates a spatially resolved refractive index map related to the edge boundary of the object.

[0034] According to a preferred embodiment of the invention, the computer program is designed to generate a composite image to display an overlay of the generated refractive index map with an edge boundary of the object. In other words, if the measurement object is a pair of spectacles, a measurement of the mounted spectacles and a reference to the actual edge geometry can be performed. The optician can then, for example, immediately determine whether the spectacles have been correctly ground, i.e., whether they are correctly seated in the frame.

[0035] In this context, it has proven particularly advantageous to represent the refractive power distribution as a composite image of the refractive power within the determined boundary of the measurement object and the actual boundary of the measurement object. According to a preferred embodiment of the invention, the computer program is designed such that, before or after the determination process, it determines an edge boundary of the object from the images of the test pattern acquired during the acquisition process. The computer program preferably determines the edge boundary with the aid of an image processing algorithm.

[0036] According to a preferred embodiment of the invention, the transparent object is an object with an intended optical effect, in particular a mounted pair of spectacles, wherein the spectacles are preferably in their position of use.

[0037] According to a preferred embodiment of the invention, the transparent object is an object without an intended optical effect, in particular an extended, substantially flat object, in particular a windshield of a motor vehicle.

[0038] Further embodiments of the invention, features, and combinations of features are given below in the explanation of embodiments of the invention. These embodiments relate to mounted spectacles and a windshield as measuring objects. However, embodiments, features, and combinations of features given in this context are not limited to these measuring objects, but also apply directly or correspondingly to other optical elements or are transferable to other optical elements. Fig. 1 shows a simplified perspective view of a measuring device.

[0039] Fig. 2 is a simplified schematic representation of a

[0040] measuring device,

[0041] Fig. 3 a reference test pattern,

[0042] Fig. 4 shows a test pattern imaged by an object in a first object position,

[0043] Fig. 5 shows a test pattern imaged by the object in a second object position,

[0044] Fig. 6 Composite images overlaying generated refractive index maps with a border boundary.

[0045] All figures depict the invention not to scale, but merely schematically and with only its essential components. Like reference numerals correspond to elements with the same or comparable function.

[0046] The example described below relates to the generation of a refractive index chart for progressive lenses. The measuring device 1 comprises, as outlined in Figs. 1 and 2, a self-illuminating display 2, for example a TFT screen, as a display device for displaying a test pattern 3. The displayed test pattern 3, here in the form of a simple dot grid, is shown in Fig. 3. The dot grid comprises a plurality of regularly arranged dot-shaped pattern elements 23. The measuring device 1 comprises a computer unit 4 with a computer program 5 for providing the test pattern 3 by controlling the display 2 connected to the computer unit 4.

[0047] A pair of spectacles 8 mounted on a support 7 serves as the measurement object. In this example, two measuring fields are provided for the spectacles 8 with two lenses 9. The measuring device 1 comprises two digital cameras 10 serving as image capture devices, so that a camera 10 is assigned to each measuring field (binocular measuring arrangement). The measuring fields can overlap. Several cameras 10 can also be provided for each spectacle lens 9 or per measuring field. The additional data thus obtained can be used to improve the quality of the measurement results.

[0048] The glasses 8 are placed in a first object position 11 between the display 2 and the cameras 10. For the subsequent determination of the optical properties, neither the absolute position of the recording medium 7 nor any angle (tilt, inclination) of the measuring object 8 is relevant.

[0049] The cameras 10 are arranged at a fixed, known distance from the display 2. The relative positions of the cameras 10 to each other and to the display 2 remain unchanged during the acquisition process. The distance between the cameras 10 is not important, and in particular, it does not depend on the distance between the lenses 9 in terms of channel-by-channel centering.

[0050] The cameras 10 are designed so that their focal plane corresponds to the plane of the display 2 and both cameras 10 each capture the entire object 8, i.e., both lenses 9 of the spectacles. Fig. 2 only symbolically shows a single beam path 13 for each lens 9 and camera 10.

[0051] In the example described here, the optical axes of the cameras 10 s are arranged parallel to one another to simplify the evaluation of the measurement data and are assigned to the lenses 9 of the glasses 8 and aligned to their centers.

[0052] The cameras 10 image the display 2 or part of it and capture an image of the test pattern 3. In other words, the test pattern 3 shown by the display 2 is projected by the glasses 8 onto the sensors of the cameras 10. Both lenses 9 are captured simultaneously. The number of pattern elements 23 captured by the cameras 10 is irrelevant for the measurement result. The number of pattern elements 23 captured only influences the lateral resolution of the measurement. With very strongly reducing spectacle lenses 9, the number of detectable pattern elements 23 becomes very small. In this case, the density of the pattern elements 23 in the test pattern 3 can be increased.

[0053] Images (pictures) of the test pattern 3 are taken with the cameras 10. First, an image 30 of the unchanged test pattern 3 is taken with the cameras 10, i.e. the pattern not altered by the spectacle lenses 9, see Fig. 3. This unchanged test pattern 3 serves as a reference test pattern 20. This makes it known where the individual pattern elements 23 of the test pattern 3 are located in the images captured by the cameras 10 when there is no refractive element between the display 2 and the cameras 10.

[0054] Subsequently, the cameras 10 record at least two images 31, 32 of the test pattern 3 altered by the glasses 9 (see Figs. 4, 5). For a measurement with sufficient accuracy for spectacle lenses, two images at different distances of the measurement object 8 from the measuring device 1 are sufficient. Sufficient accuracy for spectacle lenses is in the range of 1 / 16 diopter.

[0055] With the glasses 8 in a first object position 11, a first modified image 31 is recorded with the cameras 10. The first modified test pattern 21 depicted therein is shown in Fig. 4. As can be seen there, the pattern elements 23 of the first test pattern image 21 located within an edge boundary 18 are slightly shifted relative to the corresponding pattern elements 23 in the image 30 of the reference test pattern 20.

[0056] The measuring arrangement 1 is then changed such that the glasses 8 are in a second object position 12 between the display 2 and the cameras 10. For this purpose, the support carrier 7 is moved in the z-direction 17 between the display 2 and the cameras 10. Since the glasses 8 are fixed in position to the support carrier 7, the distance between the various object positions 11, 12 corresponds to the distance between the corresponding positions of the support carrier 7. In an alternative variant, the display 2 and cameras 10 are mounted at a fixed, aligned distance from one another and are designed as a moving unit and are moved in the z-direction 17 relative to the support carrier 7, which is stationary in this case, in order to establish the required object positions 11, 12.

[0057] The second object position 12 differs from the first object position 11 by a significant Az . In the illustrated example, the second object position 12 is closer to the cameras 10 and is indicated by dashed lines in Fig. 2. The distance (Az) between the object positions 11, 12 is known and represents the only information required, in addition to the image data from the recordings by the cameras 10, to determine the optical properties of the glasses 8.

[0058] The computer unit 4 with the computer program 5 also serves to control a movement unit (not shown) which serves as a positioning device for assuming different object positions 11, 12 by moving the recording carrier 7 in the z-direction 17 or, in an alternative variant, by moving the display camera unit relative to a stationary recording carrier 7 in the z-direction 17.

[0059] With the glasses 8 in this second object position 12, the cameras 10 record a second modified, here enlarged, image 32. The second modified test pattern 22 depicted therein is shown in Fig. 5. It shows a greater displacement compared to the first modified test pattern 21 shown in Fig. 4 with respect to the reference test pattern 20, as well as an enlargement of the pattern elements 23 within the edge boundary 18.

[0060] 3, 4 and 5, there is no pattern element in the center of the pattern. This defect 24 is used in the subsequent image processing to simplify assignment of an examined location within the measuring field. In an alternative variant not shown, a test pattern is used to achieve this purpose which comprises non-point-shaped pattern elements which have different shapes depending on their position within the test pattern. The computer unit 4 with the computer program 5 is also used to evaluate the measurement results recorded by the cameras 10. The properties of the measurement object 8 are determined with the computer program 5 by analyzing the recorded images 31, 31, 32. The computer program 5 contains algorithms for carrying out the necessary calculations and for determining the desired data.

[0061] First, the limiting edge 18 of the spectacle lenses 9 is determined from the measured image data, i.e. the visible edge of the spectacle lenses in the frame. In the further evaluation, the changes of the test pattern 21, 22 compared to the reference test pattern 20 are determined exclusively within this edge boundary. From this edge boundary, an edge line 19 can be determined, which serves as the border of a refractive index map 29 or is inserted into a composite image 33, see Fig. 6. The determined position of the edge 18 is also used as a boundary condition for the expected value for the position of the surface to be measured of the respective spectacle lens 9.

[0062] After the limiting edge 18 of the spectacle lenses 9 has been determined, for each of the two spectacle lenses 9 the test pattern 21, 22 changed by the spectacles 8 to be measured is compared for each object position 11, 12 with an unchanged reference test pattern 20 in order to determine local pattern changes.

[0063] The test pattern 3 consists of pattern elements 23 in the form of points which lie on the intersection lines of equidistant horizontal and vertical lines (Cartesian point pattern). For each individual point there are therefore four direct horizontal and vertical neighbors and a further four neighbors in the diagonals which together represent the so-called 8-neighborhood. Firstly a search is carried out for the positions of the images of the pattern elements 23 in the image. Here, the individual pattern elements 23 are not considered, but rather image groups are considered, with each image group being formed by a 3x3 neighborhood of pattern elements 23. Each image group 25 represents a surface element of a spectacle lens 9. In other words, surface elements of each spectacle lens 9 to be evaluated are defined by selecting neighborhoods of pattern elements 23 in the images 30, 31, 32 captured by the cameras 10.

[0064] Next, the corresponding centroids of the 25 image groups are determined. The extent by which these centroids are deflected from the nominal position, i.e., the calibrated zero position, is then determined. Then, for each 25 image group, i.e., for each 3x3 neighborhood, a local affine transformation matrix is ​​determined. This transforms the unperturbed initial state (calibrated state) into the perturbed state (state with the refractive element), whereby, for example, at least five of the nine pattern elements of the neighborhood must be present. This is done for all 25 image groups that represent surface elements within the previously determined boundary.

[0065] However, the exact location of the refractive element 8 and the exact angle at which the refractive surface is located are unknown. However, since the refractive surfaces of the lenses 9, which are made of the same material, are adjacent to each other, i.e., geometrically connected, their principal surfaces must be continuously and differently connected to each other (continuity condition). Taking this into account, a substantially unique solution for the position of the respective principal surface and thus also the refractive power of the refractive surfaces is obtained.

[0066] After the transformation matrices have been determined, it is determined with the aid of suitable algorithms of the computer program 5 in which direction and with which strength the local refractive power of the surface element results, which is represented by the considered image group 25, ie the corresponding 3x3 neighborhood t .

[0067] Although a set of possible main surfaces of a spectacle lens 9 can be determined in this way, the angle of the refracting surface is still unknown when evaluating only a single measurement with a single object position 11. Only by evaluating the results of at least a second measurement, in which the spectacles 8 are in a different object position 12, i.e., a different position of the main surface is present, can the angle and thus the position of the main surface be determined.

[0068] The transformation parameters (principal axis directions, scaling, displacement) then emerge from the transformation matrix calculated for each 3x3 neighborhood and each object position 11, 12 and are calculated using suitable algorithms of the computer program 5. In other words, the coefficients of each individual local affine transformation matrix provide information about the mean lateral displacement (translation) of the corresponding pattern element group (neighborhood), as well as about the scaling with respect to the respective principal axes and the orientation of these principal axes. The local pattern displacements from both object positions 11, 12 can be calculated to form the local prism. In other words, the local translation is irrelevant for the upcoming refractive power calculation, but the local prism and its orientation can be calculated from it.

[0069] The two scales along the two principal axes represent the magnifications (reductions). Using the local scales along the locally applicable principal axes, which were determined in both object positions 11, 12, the local refractive power present there is calculated with the aid of suitable algorithms of the computer program 5. The refractive power is recalculated from two magnifications (i.e., two object positions) using a mapping equation. In other words, the pairwise scales of the primary principal axes from the two different object positions 11, 12, but at the same location on the spectacle lens 9, are converted into an underlying refractive power in this section using a mapping equation. The same applies to the pairwise scales of the secondary principal axes.The sphere, the spherical equivalent (mean), and the cylinder (difference) are then calculated from the two local refractive powers (primary and secondary) along the respective sections. This also determines the orientation of the cylinder.

[0070] The spatially resolved measurement data for sphere, cylinder, axis, and prismatic power obtained in this way, related to the actual edge of the lenses 9 (i.e., the lower orders of refractive power), can be displayed as a refractive index map 29 for assessing centration, the position of the cylinder, and other patient-specific parameters. This can be used for quality assurance and to determine the causes of patient-specific intolerances. For this purpose, refractive index maps 29 are generated that show the distribution of the refractive indices. The refractive index maps 29 are combined with the determined edge line 19 in a composite image 33.

[0071] In the case of the measurement of spectacles 8, the display contains the refractive index maps 29 of both lenses 9 relative to the spectacle frame. The refractive index map 29 can be displayed for the spherical equivalent, the minimum and maximum principal section, sphere, cylinder, cylinder axes and prism effect, see Fig. 6, which shows refractive index maps of progressive lenses calculated from measurements, with the upper display showing the spherical equivalent and the lower display showing the cylinder. The displayed border of the refractive index maps 29 by means of the edge line 19 corresponds to the actual shape of the spectacle frame. This allows a direct assignment of the refractive powers to the patient's actual visual points, which can be obtained, for example, using a video centration system.

[0072] The calculated results, in particular the determined refractive index maps 29 and / or composite images 33, are displayed for immediate use by the optician using a suitable display device 6, for example, a second display. The computer program 5 is also configured to display these results by controlling the second display connected to the computer unit 4.

[0073] In this way, all optical properties can be determined across essentially the entire aperture of the lens. Since the evaluation is not point-by-point but rather based on neighborhoods, only predictions about the optical properties of those areas located in the immediate vicinity of the geometric edge of the lens can be made by extrapolation.

[0074] In a further, non-illustrated embodiment of the invention, a windshield of a motor vehicle serves as the optical element and measurement object. All of the technical features and properties of the measuring device 1 and the measuring method specified above in connection with the measurement object, glasses 8, also apply accordingly to the measurement object, the windshield. However, according to a preferred embodiment, only a single camera 10 would be used, which together with the display 2 forms a display-camera unit in the form of a C-arm, which is mounted on a robot arm. The various object positions 11, 12 of the measurement object relative to the camera 10 are realized in that the C-arm is moved around the stationary measurement object, in other words, by traversing the measurement object. In this case, several defined positions are approached in a three-dimensional trajectory.During the determination process for a number of image groups, a suitable transformation matrix corresponding to this measurement arrangement is determined for each pair of test patterns to be compared.

[0075] When using such a C-arm system, which is also suitable for other large objects, a pose-dependent misalignment correction is required in addition to the calculation and data evaluation described above in connection with the measurement of the glasses 8 in order to take into account the gravity-induced bending of the C-arm, which influences the measurement result, as a function of the C-arm's position in space. All features presented in the description, the following claims and the drawings can be essential to the invention both individually and in any combination with one another. These features or combinations of features can each constitute an independent invention, the use of which is expressly reserved.

[0076] When specifying a combination of features defining an invention, individual features from the description of an embodiment need not necessarily be combined with one or more or all other features specified in the description of that embodiment; in this respect, any sub-combination of features of one or more embodiments is expressly disclosed.

[0077] Furthermore, physical features of the device can be reformulated to become process features, and process features can be reformulated to become physical features of the device. Features reformulated in this way are implicitly disclosed.

[0078] The device according to the invention is designed to carry out the described method, in particular and at least to carry out the determination step, i.e. to determine the optical properties of the object during the determination process. The device is preferably a computer unit (data processing unit, computer) designed to carry out all steps in accordance with the method described here which are related to the processing of data, or the device comprises such a computer unit. The computer unit preferably has a number of function modules, each function module being designed to carry out a specific function or a number of specific functions in accordance with the described method. The function modules can be hardware modules or software modules.In other words, as far as the computer unit is concerned, the invention can be implemented either in the form of computer hardware or in the form of computer software or in a combination of hardware and software. As far as the invention is implemented in the form of software, i.e. as a computer program, all of the functions described are implemented by computer program instructions when the computer program is executed on a computer with a processor. The computer program instructions are implemented in a manner known per se in any programming language and can be made available to the computer in any form, for example in the form of data packets transmitted via a computer network or in the form of a computer program stored on a data carrier.

[0079] Reference symbol list

[0080] 1 measuring device

[0081] 2 Display

[0082] 3 test samples

[0083] 4 Computer unit

[0084] 5 computer program

[0085] 6 additional display devices

[0086] 7 recording media

[0087] 8 glasses

[0088] 9 Lens

[0089] 10 Camera

[0090] 11 first object position

[0091] 12 Second object position Beam path (free) (free) (free) z-direction Edge of the lens Edge line Reference test pattern First modified test pattern Second modified test pattern Pattern element Defect Image group (NxN neighborhood) (free) (free) (free) Refractive index chart Image of the reference test pattern Image of the first modified test pattern Image of the second modified test pattern Composite image

Claims

Claims 1. Measuring device (1) for determining optical properties of a transparent object (8), with a display device (2) for displaying a test pattern (3), with a number of image capture devices (10) for capturing images (30, 31, 32) of the test pattern (3), wherein the image capture devices (10) capture test patterns (21, 22) imaged by the object (8) at at least two different positions (11, 12) of the object (8) during a capture process, wherein the distances of the object positions (11, 12) to one another are known and wherein the relative positions of the image capture devices (10) to one another and to the display device (2) are unchanged during the capture process, with a computer unit (4) with a computer program (5) for determining optical properties of the object (8), which computer program (5) during a determination process without knowledge of the geometric shape,the position and the orientation of the object (8) from the images (30, 31, 32) of the test pattern (3) captured by the image capture devices (10) during the capture process, optical properties of the object (8) are determined by comparing test patterns (20, 21, 22) captured during the capture process.

2. Measuring device (1) according to claim 1, with a positioning device for realizing a different positioning of the object (8) between the display device (2) and the image capture devices (10) , wherein the computer program (5) during the detection process, the positioning device is activated to position the object (8) differently.

3. Measuring device (1) according to claim 1 or 2, wherein the image capture devices (10) capture an unchanged reference test pattern (20) during the capture process.

4. Measuring device (1) according to claim 3, wherein the computer program (5) determines, during the determination process, for a number of object positions (11, 12), changes in the test pattern (21, 22) imaged by the object (8) compared to the reference test pattern (20) as a comparison test pattern.

5. Measuring device (1) according to one of claims 1 to 4, wherein the computer program (5) during the determination process for a number of object positions (11, 12) changes of a test pattern (21) which is imaged by the object (8) arranged in a first object position (11) compared to a number of other test patterns (22) as a comparison test pattern determines which other test patterns (22) are imaged by the object (8) when the object (8) is in a position (11) different object positions (12).

6. Measuring device (1) according to claim 4 or 5, wherein the computer program (5) during the determination process changes in the test pattern imaged by the object (8) (21, 22) compared to a comparison test sample (20) within an edge boundary (18) of the object (8).

7. Measuring device (1) according to one of claims 4 to 6, wherein the computer program (5) during the determination process changes in the test pattern imaged by the object (8) (21, 22) compared to a comparison test pattern (20) for a plurality of image groups (25), each image group (25) being formed by a neighborhood of images of individual pattern elements (23) of the test pattern (3) and each image group representing a surface element of the object (8).

8. Measuring device (1) according to claim 7, wherein the computer program (5) during the determination process for a number of these mapping groups (25) determines a local affine transformation matrix for each pair of test patterns (20, 21, 22) to be compared.

9. Measuring device (1) according to claim 8, wherein the computer program (5) during the determination process for at least one The imaging group (25) determines the principal axis directions and the scalings along the two principal axes from the transformation matrices determined for this imaging group (25) and from these the local refractive power of the surface element represented by this imaging group (25).

10. Measuring device (1) according to claim 8 or 9, wherein the computer program (5) during the determination process for at least one image group (25) determines from the transformation matrices determined for this image group (25) the local translations and from these the local prism of the surface element represented by this image group (25).

11. Measuring device (1) according to one of claims 1 to 10, wherein the computer program (5) following the determination process using at least one of the determined optical Properties of the object (8) generates a refractive index map (29) of the object (8).

12. Measuring device (1) according to claim 11, wherein the computer program (5) generates a composite image (33) to display an overlay of the generated refractive index map (29) with an edge boundary (19) of the object.

13. Measuring device (1) according to one of claims 1 to 12, wherein the computer program (5) determines an edge boundary (18) of the object (8) from the images of the test pattern (3) acquired during the acquisition process.

14. System for determining optical properties of a transparent object (8), with a measuring device (1) according to one of claims 1 to 13 and with a transparent object (8) positioned between the display device (2) and the number of image capture devices (10).

15. System according to claim 14, wherein the transparent object (8) is an object with an intended optical effect, in particular a mounted pair of spectacles, wherein the spectacles are preferably in their position of use.

16. System according to claim 14, wherein the transparent object (8) is an object without an intended optical effect, in particular an extended, substantially flat object, in particular a windshield of a motor vehicle.

17. Measuring method for determining optical properties of a transparent object (8) , comprising the following steps: Capturing images (30, 31, 32) of a test pattern (3) during a capturing process, wherein the capturing process comprises capturing test patterns (21, 22) imaged by the object (8) at at least two different positions (11, 12) of the object (8), wherein the distances between the object positions (11, 12) are known and wherein the relative positions of the image capturing devices (10) to each other and to the display device (2) are unchanged during the capturing process, Determining optical properties of the object (8) during a determination process without knowledge of the geometric shape, the position and the orientation of the object (8) from the images (30, 31, 32) of the test pattern (3) acquired during the acquisition process by comparing test patterns (20, 21, 22) acquired during the acquisition process.

18. A computer program comprising computer program instructions which, when executed by a computer unit (4), cause the computer unit (4) to carry out the determining step of the method according to claim 17.

Images