Method and device for measuring optical lenses for individual wearing conditions of users

Abstract

The invention relates to a method and apparatus for measuring optical lenses for various wearing conditions of users. The invention relates to an apparatus for measuring the cornea of ​​a subject, comprising: an image capture device configured to capture image data of the subject's iris from a plurality of viewpoints via an imaging beam path passing through the cornea; and a calculation unit configured to: provide a mathematical model of the anterior segment of the subject's eye, the mathematical model comprising mathematical models of the cornea and the iris; identify and register image features of the iris present in a plurality of images of the image data; determine a deviation between the actual position of the image features of the iris in the images captured from the plurality of viewpoints and the expected position of the image features of the iris in the images captured from the plurality of viewpoints taking into account the relative position of the mathematical model of the cornea and the iris; adapt parameters of the mathematical model of the cornea so as to minimize the deviation; and determine measurement variables of the cornea based on the adapted mathematical model of the cornea.

Description

[0001] This application is a divisional application of the patent application with the application date of April 23, 2019, application number 201980027633.2, international application number PCT / EP2019 / 060346, and invention name “Method and device for measuring optical lenses for various wearing conditions of users”. Technical Field

[0002] The present disclosure relates to the field of ophthalmic optics, and more particularly to an apparatus for measuring the optical effect of an optical lens, in particular a spectacle lens, disposed in a measurement volume. The present disclosure further relates to an apparatus for measuring the spatial refractive index distribution of an optical lens, in particular a spectacle lens, disposed in a measurement volume. The present disclosure further relates to a method for calibrating a corresponding apparatus and a computer-implemented method for measuring the optical effect of an optical lens disposed in a measurement volume. Background Art

[0003] In the case of spectacle lenses, the measurement value of interest is the vertex power (VP). Under certain observation conditions, the vertex power is an effective variable of the lens. Consequently, VP varies depending on the distance from the observer or the inclination of the lens. Measuring instruments that determine VP by directly interpreting the light beam passing through the lens will always determine VP in this measuring instrument configuration. This effective variable is of only limited use for the unambiguous qualification of components. Therefore, ISO VP was defined to remedy this. ISO VP is the VP measured perpendicular to the surface normal under parallel incident light. For this purpose, specific measuring instruments have been developed in the past that determine the ISO VP at various locations on the lens.

[0004] The advantage of ISO VP is that it is a unique variable, not an effective variable like VP. The disadvantage is that ISO VP can deviate from the effect of a pair of glasses when worn (also known as the wearing vertex power or wearing value).

[0005] A lensometer with a spectacle installation for calibrating ready-to-glass spectacles is known from DE 1238690 B1. With this lensometer, the vertex power of a spectacle lens already arranged in a spectacle frame can be determined.

[0006] EP2101143 A1 discloses a method and apparatus for capturing the shape of a transparent refractive object. In this method, the object to be measured is inserted transmissively into an imaging system. Using the improved imaging system thus produced, a grid with a known structure is imaged into a receiver device, and the resulting image is evaluated. A planar grid with a known structure is used, whose grid points are assigned to evaluable spatial coordinates in a grid coordinate system. One or more of these planar grids are inserted at at least two different positions relative to the object to be measured.

[0007] US 2016 / 0109362 A1 discloses a method and apparatus for determining a local refractive index.

[0008] Knaus et al., "Measuring the refractive power with deflectometry in transmission," Acta DGaO, 2008, describe a deflectometry method for determining refractive power.

[0009] WO 2017 / 134275 A1 describes a method and a system for determining the optical axis and / or physical properties of a lens, and their use in the context of virtual imaging and head-mounted display devices.

[0010] WO 2016 / 207412 A1 discloses an apparatus and method for measuring various data of a pair of glasses arranged in a measurement position, the pair of glasses having a left lens and / or a right lens. The apparatus includes a display for displaying a test structure. The apparatus includes an image capture device that captures the test structure via an imaging beam path that passes through the left lens and / or the right lens of the glasses. The apparatus includes a computer unit having a computer program that determines the refractive power distribution of at least a portion of the left lens and / or the right lens based on an image of the test structure captured by the image capture device, a known spatial orientation of the display relative to the image capture device, and a known spatial orientation of the glasses relative to the image capture device.

[0011] DE 10 2013 219 838 A1 discloses a method and a system for determining the spatial structure of an object.

[0012] DE 102014005281 A1 discloses a method and a device for determining the position of at least one spectacle lens in space.

[0013] DE 102011089704 A1 discloses the storage of information about spectacle lenses, spectacle lens blanks or spectacle lens semi-finished products.

[0014] Devices known from the prior art are effect measurement devices, in which the effect of an optical element is initially determined at a measuring location. Summary of the Invention

[0015] Against this background, it is an object of the present invention to provide a measuring device which facilitates a more flexible determination of the optical effect of an optical lens.

[0016] According to a first aspect of the present disclosure, a device for measuring the optical effect of an optical lens, in particular a spectacle lens, arranged in a measurement volume is provided, the device comprising a display device configured to display a test structure; an image capture device configured to capture image data of the test structure from a plurality of viewpoints via an imaging beam path passing through the lens; and a calculation unit, wherein the calculation unit is configured to determine a three-dimensional shape of the lens based on the image data; and to calculate the optical effect of the lens based on the three-dimensional shape of the lens, wherein the lens is a spectacle lens. The calculation unit is configured to calculate the optical effect of the spectacle lens for a specified wearing position of a user, which specified wearing position may differ from the measurement position in which the image data was captured.

[0017] Compared to conventional lens meters, the main advantages of the present invention may include, among other things, increased clarity and / or range of applications. This is due to the fact that the optical effect of a lens always depends on the direction of the incident radiation. In the case of a measurement setup, a measuring instrument that only measures the optical effect can reliably determine the optical effect. This makes it possible to make very precise statements for a wide range of applications.

[0018] However, the measured condition and the actual wearing condition or wearing position of a spectacle lens may not agree or may deviate from each other to such an extent that a reliable statement is no longer possible. Therefore, further measurements of the effects under wearing conditions are necessary to determine the optical effect in this wearing position.

[0019] The solution according to the present invention follows a different approach: a two-stage procedure is proposed, in which the three-dimensional shape of the lens is first determined, and only then the optical effect of the lens is calculated. The known three-dimensional shape or topography of the lens allows the optical effect to be subsequently calculated for any viewing or wearing situation. This can include, among other advantages, more accurate results and a more personalized interpretation for a wide variety of specific user requirements.

[0020] The display unit displays the test structure. The image capture device captures the test structure from multiple viewpoints. Because the test structure is known, a correlation can be made between the image data of the test structure captured by the image capture device for each of the multiple viewpoints. If an optical lens is now placed in the measurement volume between the display unit and the image capture device, the beam path between the corresponding pixel of the image data and the corresponding image element of the test structure is affected.

[0021] However, as pointed out in WO 2016 / 207412 A1, in this process, it is not possible to determine only a single virtual refractive plane. According to the proposed solution, by means of capturing image data from multiple viewpoints through an imaging beam path passing through the lens, it is possible to make a separate statement about the shape of the front surface (through which the beam path emanating from the test structure enters the optical lens) and a statement about the shape of the back surface (through which the beam path emanating from the test structure exits the optical lens). Therefore, for this purpose, a system of equations with a large number of equations can be established, based on which the surfaces on the beam paths can then be reconstructed. The three-dimensional shape of the lens then follows from the shape of the front surface and the shape of the back surface.

[0022] Calculation of the optical effect based on the three-dimensional shape can then be performed using known methods.

[0023] It will be appreciated that the three-dimensional shape of the entire lens need not be determined. By way of example, the calculation may be performed on only a portion (e.g. only the front and back surfaces, but not the sides) or only a portion of the user's field of view.

[0024] When determining the three-dimensional shape of the lens by means of the calculation unit, further information can advantageously be taken into account, such as the known relative spatial position of the display device with respect to the respective viewpoint from which the capture was performed.

[0025] According to another aspect, a device for measuring the optical effect of an optical lens arranged in a measurement volume is provided, the device comprising a display device configured to display a test structure; an image capture device configured to capture image data of the test structure from a plurality of viewpoints via an imaging beam path passing through the lens; and a calculation unit, wherein the calculation unit is configured to: determine a three-dimensional shape of the lens based on the image data; and calculate the optical effect of the lens based on the three-dimensional shape of the lens. The calculation unit may be configured to determine the three-dimensional shape of the lens further taking into account one or more known contact points of the lens; wherein the positions of these contact points are used to assign an expected value for the position of the spectacle lens in the measurement volume to an algorithm for determining the shape of the spectacle lens.

[0026] According to another aspect of the present disclosure, a device for measuring the optical effect of an optical lens arranged in a measurement volume is provided, the device comprising a display device configured to display a test structure; an image capture device configured to capture image data of the test structure from multiple viewpoints via an imaging beam path passing through the lens; and a calculation unit, wherein the calculation unit is configured to: determine a three-dimensional shape of the lens based on the image data; and calculate the optical effect of the lens based on the three-dimensional shape of the lens. The calculation unit can be configured to determine the three-dimensional shape of the lens taking into account boundary conditions, wherein the boundary conditions are determined by reading information about the lens to be measured. The boundary conditions can be determined by reading a marking or code on the lens.

[0027] According to another exemplary aspect of the present disclosure, which may help understand the present invention, a method for calibrating an apparatus for measuring various data of an optical lens arranged in a measurement volume is provided, wherein the method includes the following steps: setting or displaying a test structure on a display device; setting a first distance between an image capture device and the display device, and capturing image data of the test structure through the image capture device from the first distance; setting a second distance between the image capture device and the display device, and capturing image data of the test structure through the image capture device from the second distance; determining the direction of an incident light beam captured by the image capture device and the corresponding pixels in the image data based on the image data captured at the first distance and the image data captured at the second distance.

[0028] The advantage of this solution is that the direction of the incident light beam can be determined in a simple manner. Here, the display device used for measurement in any case can also be used for calibration purposes. During calibration, the relative position of the display device (including its image point) with respect to the image capture device can preferably be taken into account.

[0029] Due to the height adjustment, the angle of the incident light beam relative to the image capture device, for example, the camera of the image capture device, changes. The direction of the incident light can be determined based on the relationship between the known height change and the accompanying change in the image of the test structure in the image data. This facilitates the so-called "backward propagation" of the incident light beam.

[0030] According to another aspect of the present disclosure, a method, in particular a computer-implemented method, for measuring the optical effect of an optical lens, in particular a spectacle lens, arranged in a measurement volume is disclosed, the method comprising the following steps: providing a test structure for display on a display device; capturing image data of the test structure from multiple viewpoints by an imaging beam path passing through the lens; determining a three-dimensional shape of the lens based on the image data; and calculating the optical effect of the lens based on the three-dimensional shape of the lens.

[0031] According to further aspects of the present disclosure, methods corresponding to the aforementioned aspects are proposed.

[0032] According to another aspect of the present disclosure, a computer program product is provided, comprising instructions that, when executed by a computer, cause the program to implement one of the aforementioned methods. It should be understood that the method steps in this case are designed to be implemented by a computer. By way of example, capturing image data can be understood to refer to receiving image data. Thus, the term can be understood to refer to the transmission of measurement data generated by a physical image sensor. Accordingly, a test structure can be provided by providing test structure data. The data can then be displayed by a display device.

[0033] Providing the test structure may also be a previous step not performed by the computer program product.

[0034] If not indicated otherwise, the terms used herein are to be understood within the meaning of the standard DIN EN ISO 13666:2012 prepared by the Deutsches Institut für Normung eV [German Institute for Standardization].

[0035] According to Section 5.8 of the DIN EN ISO 13666:2012 standard, the term "front surface" or "object-side surface" refers to the surface of a spectacle lens in spectacles that is intended to face away from the eye. According to Section 5.19 of DIN EN ISO 13666:2012, the term "back surface" or "eye-side surface" refers to the surface of a spectacle lens that is intended to be mounted facing the eye. As an alternative, the term "front surface" within the scope of the present disclosure may refer to the surface of the lens that faces the display device. Correspondingly, the back surface within the scope of the present disclosure may refer to the surface that faces away from the display device.

[0036] In one configuration, an image capture device may be provided, the image capture device comprising a first camera and a second camera, wherein the first camera is configured to capture first image data from a first viewpoint and the second camera is configured to capture second image data from a second viewpoint; and wherein the computing unit is configured to determine the three-dimensional shape of the lens based on the first image data and the second image data. As an alternative to using two cameras, the first image data and the second image data may be captured at different positions using a single camera. A shifting device or positioning device may be provided to move the camera between the first and second positions.

[0037] In an optional development, the first camera and the second camera may be arranged at an angle relative to each other, such that the test structure may be captured by the first camera from a first angle and by the second camera from a second angle.

[0038] The lens is a spectacle lens, and the optical effect of the spectacle lens is calculated for a given wearing position of a user. One advantage may be, in particular, that the optical effect can be calculated retrospectively for any given specified or desired wearing position of the user. Here, the wearing position may also differ significantly from the measurement position at which the image data was captured. The calculation unit may be configured to calculate the optical effect of the spectacle lens for a specified wearing position of the user, which differs from the measurement position at which the image data was captured. This allows for user-specific adaptation and flexible calculation of usage values. In contrast, conventional lens meters do not provide an individualized representation for the user.

[0039] In one configuration, a calculation unit may be provided, which is configured to iteratively determine the three-dimensional shape of the lens by an integration method.

[0040] In another configuration, a computing unit may be provided, which is configured to determine the three-dimensional shape of the lens based on back-tracing a light beam entering the image capture device. In particular, the light beam entering the image capture device may be traced back to a known original position of a test structure displayed on a display device. In particular, the relative position of the display device to the position or viewpoint of the captured image data is known. Optionally, the relative position may be determined based on the above-mentioned camera calibration, by means of changes in distance or height. By way of example, methods such as back-propagation or reverse ray tracing may be used to determine the three-dimensional shape of the lens. In short, the surface reconstruction of the lens to be measured is performed based on a comparison of the expected position and the actual position of one or more elements of the test structure in the captured image.

[0041] In one configuration, determining the three-dimensional shape of the lens can include dividing the front and / or back surface of the lens into surface elements and determining the alignment of these surface elements, in particular determining the surface normals of these surface elements. In particular, this determination can be performed based on back-tracing the light beam entering the image capture device. In other words, the surface alignment can be determined for each surface element (for each surface element). By way of example, the surface normal of each segment or surface element can be calculated.

[0042] In a further development, the calculation unit can be configured to determine the three-dimensional shape of the front and / or back surface of the lens based on the alignment of the surface elements. A surface of the lens, for example the front or back surface, can be constructed from individual surface elements. Preferably, the surface is constructed in such a way that there are no (significant) jumps between adjacent elements.

[0043] In one embodiment, the calculation unit can be configured to determine the three-dimensional shape of the lens taking into account the boundary conditions of a parameterized region, in particular a plane, a sphere, a torus or a segment thereof, in which the front or back surface of the lens is a parameterized region. The advantage is that the calculation is faster and / or more accurate, since the parameter space is reduced by specifying the boundary conditions.

[0044] In one embodiment, a calculation unit can be provided that is configured to determine the three-dimensional shape of the lens, further taking into account one or more known contact points of the lens. As an alternative or in addition thereto, a calculation unit can be provided that can be configured to determine the three-dimensional shape of the lens taking into account boundary conditions, wherein the boundary conditions are determined by reading information about the lens to be measured, in particular by reading markings or codes on the lens. Again, the advantage can be that the calculation is faster and / or more accurate, due to the further reduction in degrees of freedom. It will be understood that multiple known contact points or the lens glass holder or spectacles holder can also be taken into account. By way of example, engravings or markings regarding the curvature, material, or refractive index can be read as a code on the lens and taken into account in the calculation.

[0045] In an exemplary configuration, which may help understanding the present invention, a calculation unit may be provided, which is further configured to determine the refractive index of the lens to be measured, in particular to determine its spatial refractive power distribution. Lenses or spectacle lenses with one refractive index may be considered as special cases. Preferably, the refractive index is constant in at least one part. Further, the spatial refractive power distribution of a so-called GRIN (GRaded-INdex) lens may be determined. The inventors have recognized that the proposed solution can be used not only to capture the shape but also to determine the refractive index, i.e. to measure the interior of a transparent body. By way of example, internal interfaces between areas with different refractive indices may be determined. Possible applications include, for example, multi-part lenses, lenses formed from materials with different refractive indices, achromatic lenses, optical systems or objectives.

[0046] In one configuration, the apparatus may further include a height adjustment device configured to change the distance between the image capture device and the display device. Furthermore, the computing unit may be further configured to determine the beam direction of the light beam captured by the image capture device based on image data captured at different distances between the image capture device and the display device. Thus, an association between pixels and beam directions can be established in a simple manner.

[0047] The advantages described above in detail for the first aspect of the present invention are correspondingly applicable to the other aspects of the present invention.

[0048] It goes without saying that the features mentioned above and also those yet to be explained below can be used not only in the combination specified in each case but also in other combinations or alone, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description.

[0050] Figure 1 shows a schematic illustration of a device for measuring the optical action of an optical lens arranged in a measurement volume;

[0051] Figure 2 An exemplary diagram of a test structure recorded through a lens is shown;

[0052] Figure 3 shows an exemplary illustration of a test structure recorded through a tilted spectacle lens;

[0053] Figure 4 A diagram showing the beam path through a transparent object;

[0054] Figure 5 A diagram showing the beam path through the lens is shown;

[0055] Figure 6 A lens composed of parametric surface elements is shown;

[0056] Figure 7 shows a schematic illustration of a device for measuring the optical action of an optical lens arranged in a measurement volume;

[0057] Figure 8 A further embodiment of a device for measuring the optical action of an optical lens arranged in a measurement volume is shown;

[0058] Figure 9 A flow chart showing an arrangement of a method for measuring the optical action of an optical lens arranged in a measurement volume;

[0059] Figure 10 A detailed flow chart showing the configuration of this method;

[0060] Figure 11 A flow chart illustrating an embodiment of a calibration method;

[0061] Figure 12 A schematic diagram of an eye is shown;

[0062] Figure 13 showing an image representation of a plan view of an eye with an image representation of an iris;

[0063] Figure 14 shows a schematic illustration of an apparatus for measuring the cornea;

[0064] Figure 15 showing the association or correlation of image features in images of the iris recorded from different viewpoints;

[0065] Figure 16 shows additional correlations of image features; and

[0066] Figure 17 A flow chart illustrating an embodiment of a method for measuring a cornea is shown. DETAILED DESCRIPTION

[0067] Figure 1 The device 10 shown in FIG. 1 is used to determine the optical effect of an optical lens 100, in particular a spectacle lens. The device 10 comprises a display device 20 configured to display a test structure 21. By way of example, this display device can be a screen or a display and can display different test structures.

[0068] The device 10 further comprises an image capture device 30 configured to capture image data of the test structure 21 from a plurality of viewpoints 31, 31', 31" via an imaging beam path 32 passing through the lens 100. In one aspect, the imaging beam paths from a plurality of different viewpoints may be recorded successively by one camera, which is arranged successively at a plurality of different positions. However, a plurality of cameras are preferably provided in order to capture image data in parallel. It will be appreciated that a hybrid form may also be provided. By way of example, the image capture device 30 may comprise a first camera 33 and a second camera 34, wherein the first camera 33 is configured to capture first image data from a first viewpoint 33 and the second camera 34 is configured to capture second image data from a second viewpoint 33". A measurement volume 200 is located between the test structure 21 and the image capture device 30, which test structure may be displayed on the display device 20.

[0069] The device 10 further includes a computing unit 40. By way of example, the computing unit 40 may be a computer, a microcontroller, an FPGA, or the like. The computing unit 40 is configured to determine the three-dimensional shape of the lens 100 based on the image data; and to calculate the optical effect of the lens 100 based on the three-dimensional shape. In other words, a two-stage process is proposed, in which the three-dimensional shape of the lens is first determined, and only then the optical effect of the lens is calculated based on the three-dimensional shape of the lens.

[0070] The following references Figures 2 to 6 This method according to the present disclosure will be explained in more detail.

[0071] Figure 2A plan view of the test structure 21 of the display device 20 recorded through the lens 100 is shown. By way of example, this may be recorded by the camera 33 through the lens 100 according to Figure 1 The test structure 21 is reproduced in a distorted form due to the lens 100. This deflection of the beam already allows conclusions to be drawn about the optical effect of the lens 100. However, this only allows statements about the effect of the entire lens 100.

[0072] Figure 3 Another exemplary image recorded by the camera is shown. However, in this case, the spectacles 101 with the optical lens 100 are arranged at a large inclination in the measurement area, so that the beam deflection caused by the optical lens 100 reproduces the actual optical effect in the wearing position only with limited accuracy.

[0073] Figure 4 An exemplary illustration of beam paths through a transparent object, such as lens 100, is shown. The origin of the beam paths is a defined point 22 on display device 21. Beam paths emanating from defined point 22 enter lens 101 at surface 102 and exit the lens at surface 103. Thus, these beam paths pass through lens 100. The beams are refracted at both entrance surface 102 and exit surface 103. Depending on the relative spatial position or orientation of lens 100 relative to display device 20 and image capture device 30, different optical effects may occur.

[0074] The inventors have realised that by recording the test structure from multiple viewpoints and thus capturing a large number of imaging beam paths (see also Figure 1 ) can resolve this uncertainty or ambiguity in optical interactions, and thus determine the optical properties of the inserted lens. In other words, a system of equations can be constructed for the imaging beam paths, each relating the imaging beams that pass through the lens 100 and enter the image capture device from multiple viewpoints to their known origins on the display device 20. From this, the three-dimensional shape of the lens 100 can be determined, and optionally, the refractive index of the lens or the distribution of braking forces within the lens can also be determined.

[0075] Figure 5A simplified example of a beam path through lens 100 is reproduced. Image point 22 on display device 20 is captured by camera 34. Beam path 110 enters the lens at point 104 on the front side 102 of lens 100 and exits the lens at point 106 on the back surface 103 of the lens. In short, when measuring with only one camera, there are equations with two unknowns: entry point 104 and exit point 105 (including the spatial orientation of the surface at these points). By using image capture device 30 to record the test structure from additional viewpoints (as indicated by additional camera 33), additional beam paths 111 and 112 can be captured. In the case of beam path 111, exit point 104 coincides with beam path 110 of camera 34. In the case of beam path 112, entry point 105 coincides with beam path 110 of camera 34. Thus, multiple equations can be established by which properties of lens 100 disposed between display device 20 and image capture device 30 can be determined.

[0076] For this purpose, the computing unit may be configured to preferably model the lens 100 as a component surface made of parameterized surface elements, such as Figure 6 , which is shown in exemplary form in FIG. The orientation of surface elements 106, 107 in front and back surfaces 102, 103 can be determined based on the deflection of the beam at points 104 and 105. Alternatively, another partitioning can be performed within lens 100. By way of example, additional interfaces within lens 100 can be determined. Optionally, a further computing unit can be implemented to determine the refractive index of lens 100 or the spatial refractive power distribution of the lens.

[0077] Alternatively, the device can be implemented as a device for measuring the spatial refractive power distribution of an optical lens arranged in a measurement volume. For this purpose, an interface configured to receive lens geometry data describing the three-dimensional shape of the lens can preferably be provided. In this case, the shape of the lens does not need to be calculated; instead, the interface can be used as input parameters for calculating the spatial refractive power distribution of the lens based on the image data and the lens geometry data.

[0078] Reference Figure 5 and Figure 6The computing unit can be configured to determine the three-dimensional shape of the lens based on back-tracing the beams entering the image capture device. The directions of the beams 110, 111, 112 entering the cameras 33, 34 of the image capture device are known. For this purpose, the image capture device can again be calibrated as described below. Thus, the incoming beams can be back-traced starting from the respective cameras 33, 34. The lens 100 is located in the beam path, between the image capture device or the respective cameras (whose position is known) and the test structure (whose position is known). Starting from a model of the lens 100, this model can be successively parameterized by the computing unit in such a way that the (known) test structure is imaged through the model of the lens 100 in such a way that image data captured by the image capture device emerge. For parameterization, in particular, the alignment of the surface elements forming the lens surface (here represented by surface normals 129, 130) can be adapted, the distance 131 between the surface elements can be varied, and optionally the refractive index n or the refractive index distribution within the lens can be varied.

[0079] Figure 7 and Figure 8 A further embodiment of a device 10 for measuring the optical effect of an optical lens 100 arranged in a measurement volume is shown. Corresponding components are denoted by the same reference numerals and will not be explained in detail again to avoid repetition.

[0080] Figure 8 An embodiment is shown in which the image capture device 30 comprises two cameras 30, 31'. These cameras see the pattern or test structure 21 from different perspectives. The calculation unit is implemented to reconstruct the test object 4 from the corresponding image data. For this purpose, a gradient field can be determined from the surface elements or normals 129, 129', such as Figure 5 and Figure 6 Explained.

[0081] Light from a defined source at a defined origin of the test structure 21 passes through the lens 100 and is captured by the image capture device 30 from different viewing angles by means of a calibrated camera system. The refractive surface of the body is reconstructed from the emerging images.

[0082] The principle works with one, two or more cameras. In an advantageous embodiment, two cameras are used, since in this case a good cost / utilization ratio can be achieved. Even more cameras can be used to further improve accuracy.

[0083] The image capture device 30 or camera 31, 31' is calibrated using a known function, by means of which a unique principal ray (camera ray) can be derived in 3D for each sensor coordinate from the origin and direction. This calibration can be performed according to the prior art. Alternatively, the known optical design of the camera and / or the employed objective lens can be included in the camera model instead of the above-described camera calibration.

[0084] By way of example, the display device 20 can have a self-luminous source, such as an array of light-emitting diodes, a TFT or LED display, a 3D display, a laser source, a polarized display, or a collimated selectively structured lighting unit. Light can also be shone onto the display device. By way of example, the display device onto which the light is shone can have a test pattern (e.g., a dot pattern or a checkerboard pattern), a particularly regular 3D pattern, an unknown feature-rich flat image (wherein the position can be estimated during operation), or an unknown feature-rich 3D scene (the position is estimated during optimization).

[0085] The calculation unit 40 can use additional information to determine the three-dimensional shape. In particular, the three-dimensional shape can be reconstructed based on the known viewpoint or position of the camera from which the image data was captured and the known position of the test structure. In this example, the image data can be the position of the image of the light beam entering the camera on the camera detector. The light beam entering the image capture device can be calculated based on the image data and the known viewpoint. Calibration of the image capture device can serve as a basis for this.

[0086] Optionally, the calculation unit 40 can be further configured to determine the three-dimensional shape of the lens, taking into account one or more boundary conditions. By way of example, a contact point or stop point 51 can be predetermined. The relative position of the lens 100 at this point is known and can be taken into account when determining the three-dimensional shape of the lens. Furthermore, information such as the shape, refractive index, or material of the front and / or back surfaces of the lens can be predetermined. Optionally, the device can be configured to read information present on the lens, for example in the form of engravings or markings 140, and take this information into account when determining the three-dimensional shape and / or when calculating the optical effect.

[0087] The invention is particularly advantageously used for measuring spectacle lenses, in particular progressive addition spectacle lenses (also known as variable focus spectacle lenses). However, simpler spectacle lenses (e.g., spherical, aspherical, toric, or prismatic lenses) can also be measured using the proposed device.

[0088] Alternatively, the calculation unit can be configured to calculate the ISO vertex power or vertex power in a specific measuring device configuration in order to provide equivalent data. By providing wearer-specific data, such as the distance between the pupil and the spectacle lens (vertex distance) and its relative position (e.g., facial bezel curvature or wearing anteversion angle), the vertex power used can be calculated.

[0089] Optionally, multiple test objects in the measurement space can be measured simultaneously. When measuring a pair of glasses with a left and a right eyeglass lens, the calculation unit can be further implemented to determine the position and relative position of the eyeglass lenses relative to one another. This allows, for example, calculation of additional information such as the distance of the optical path. Transparent bodies with different active zones can also be provided as multiple test objects. By way of example, this could be a pair of glasses with two lenses or a lens with multiple zones (bifocal, trifocal, or multifocal).

[0090] Figure 9 A flow chart of a method 900 for measuring the optical effect of an optical lens, in particular a spectacle lens, arranged in a measurement volume is shown, the method comprising the steps set out below. In a first step 901, a test structure is provided for display on a display device. In a second step 902, image data of the test structure are captured from a plurality of viewpoints by an imaging beam path passing through the lens. In a third step 903, the three-dimensional shape of the lens is determined based on the image data (and the known positions of the viewpoints and the display device relative to each other). In a fourth step 904, the optical effect of the lens is calculated based on the three-dimensional shape of the lens. This calculation can be implemented in any use case. Thus, a calculation unit can be configured to calculate a first optical effect corresponding to the ISO vertex power and a second optical effect corresponding to the use case of the user.

[0091] Optionally, the measurement method may start from step 905 , which is for calibrating the device.

[0092] A corresponding method for calibrating a device may then comprise the following steps: in a first calibration step, a test structure is arranged on the display device. In a second calibration step, a first distance between the image capture device and the display device is set, and image data of the test structure are captured from the first distance by means of the image capture device.

[0093] like Figure 8 As shown in , a height adjustment device 150 may be provided, which is configured to change the distance between the image capture device and the display device. In this context, the computing unit may be further configured to determine the beam direction of the light beam captured by the image capture device based on image data captured from different distances between the image capture device and the display device.

[0094] In a further step of the method for calibrating a device, a second distance between the image capture device and the display device can be set, and image data of the test structure can be captured from the second distance using the image capture device. From this, in a further step, the direction of the incident light beam captured by the image capture device and the corresponding image point in the image data can be determined.

[0095] Figure 10 A detailed flow chart of an embodiment of a method 1000 for measuring the optical effect of a lens arranged in a measurement volume is shown.

[0096] In a first step S1011, a test structure is displayed on a display device. By way of example, this test structure may be a pattern of dots or stripes. In a further step S1012, image data of the test structure are captured by an image capture device. In a step S1013, the positions of features of the test structure, e.g., the positions of the pattern points in the image data (corresponding to the positions on the detector surface of the image capture device), may be determined. Here, there may be a camera calibration step S1001, e.g., as explained above or Figure 11 In step S1014, the light beams or directions of these light beams incident on the image capture device can then be determined. The light beams incident on the camera can be determined as 3D vectors starting from the camera image of the displayed pattern as viewed through the lens to be measured.

[0097] In step S1021, the complete or partial pattern of the test structure can be displayed on the display device. In a further step S1022, image data of the test structure are captured by an image capture device. In step S1023, the pattern points can be associated with the image points in the image data. In particular, a series of different test patterns can be provided to resolve possible ambiguities when associating the pattern points with the image points in the image data. In other words, the luminous points of the image data captured by the image capture device can be assigned to the positions of the luminous points on the display device and therefore also to the calculated light beams incident on the image capture device. As an alternative or in addition thereto, the calculation unit can be configured to determine the neighbor relationship based on the overall pattern of the test structure.

[0098] In step S1031, a planar lighting element may be placed on a display device. By way of example, all pixels of the display device may be displayed in white. This highlights the outline of the lens, and the lens outline can be determined in step S1032. In step S1033, the relative position and size of the lens can be determined based on the captured outline. In other words, the relative position of the lens within the measurement volume can be determined in a simple manner.

[0099] In step S1041, the "best-fit" parameterized lens can be calculated. Preferably, the "best-fit" parameterized lens that can be located in the measurement volume of the device can be determined by backpropagation of the camera beam. A parameterized lens should be understood to mean a lens that can be described by several parameters such as radius, thickness or refractive index. For example, these lenses include spherical lenses and toric lenses. Toric lenses are a general compromise that can be applied here. In a more specific embodiment, it may be sufficient to define individual "complex surface zones" on the lens and only describe the spectacle lens there. By way of example, a first of these zones can be the "far zone" of a progressive lens. By way of example, a second of these zones can be the "near zone" of a progressive lens. In addition to the position of the lens or the individual surfaces, further parameters can be radius, thickness and refractive index.

[0100] In step S1042, the "best-fit" gradient surface for the front and / or back surfaces of the lens can be determined by reverse ray tracing of the camera rays. Thus, the surface of the "best-fit" parameterized lens determined in step S1041 can be described as a gradient surface, and the gradient at the location of the beam path can be varied so that the location of the light-emitting point on the display device is perfectly hit by the reverse propagation of the camera rays. In short, the three-dimensional shape of the lens is thus adapted so that the light beam received by the image capture device and the associated beam source are aligned with the display device.

[0101] In step S1043, the front surface and / or back surface of the lens can be obtained by integrating the gradient surfaces. In other words, a (continuous) new surface is determined based on the segmented gradient surfaces or the gradient surfaces determined for the surface elements. Here, this new surface can be the front surface or the back surface of the lens.

[0102] According to step S1044, steps S1042 and S1043 can be iteratively repeated. By way of example, these steps can be repeated until a quality standard is met. Optionally, if sufficient quality cannot be achieved, step S1041 can also be included in the iterative loop to consider alternative lens geometries. Due to the iterations, the three-dimensional shape of the lens can be obtained.

[0103] In another exemplary embodiment, which may aid in understanding the present invention, the shape of a lens may be predetermined, and alternatively, the spatial power distribution within the lens may be iteratively determined in a similar fashion.

[0104] One or more variables can then be determined based on the determined three-dimensional shape (optionally including the refractive index). In step S1052, usage values, particularly user-specific usage values, can be calculated. For this purpose, wearer-specific data, such as the distance between the cornea and the vertex, can be provided in step S1051. In step S1053, the ISO vertex power can be determined. In step S1054, the vertex power for the device configuration can be determined.

[0105] If a plurality of lenses or spectacle lenses are arranged simultaneously in the measurement volume, additional parameters such as the spacing of the gradient channels can optionally be determined.

[0106] It should be understood that the aforementioned steps may be performed by a computing unit and that the computing unit may be configured accordingly for the purpose of performing these steps.

[0107] Figure 11 A flow chart illustrating an exemplary embodiment of a method 1100 for calibrating a device for measuring various data of an optical lens arranged in a measurement volume is provided, which may aid in understanding the present invention. This calibration may be used, in particular, to provide a set of functions that assign a beam direction (e.g., a 3D vector) to an image point (preferably each image point) of image data captured by an image capture device, the 3D vector describing the beam direction or light beam entering the image capture device. Such a set of functions may have the following form:

[0108] where (x0, y0, 0) describes the point of the light beam in the reference plane of the image capture device, preferably the reference plane of the lens system of the camera of the image capture device, and (dx, dy, 1) describes the direction vector of the incident light beam. Thus, the set of functions contains the following four functions: x0(x, y), y0(x, y), dx(x, y), and dy(x, y), where x and y describe the pixel coordinates in the image data of the image capture device (in this case, the camera).

[0109] Such a set of functions can be determined by means of a test structure (e.g. a dot pattern) being displayed on a display device and observed from different distances by a camera of an image capture device. Figure 8 The device shown in exemplary form in FIG. 1 may include a height adjustment device 150 configured to change the distance between the image capture device and the display device.

[0110] exist Figure 11 In the method shown in FIG, steps S1101 to S1104 can be respectively Figure 10 Corresponding to steps S1011 to S1014 in . Figure 11Steps S1111 to S1113 shown in FIG. 1 may each correspond to steps S1021 to S1023 described above. However, a loop is provided in which the distance between the image capturing device and the display device is changed in step S1121. Figure 8 As shown in , a change in distance changes the direction of the incident light beam. The computing unit can be configured to determine the direction of the incident light beam based on image data captured at a first distance and image data captured at a second distance. It should be understood that this determination can further depend on the relative position between the display device and the image capture device and the change in distance.

[0111] like Figure 11 As shown in FIG, in step S1131, 3D light beams can be interpolated for a plurality of image points or pixels of the image capture device, preferably for each image point or pixel. Subsequently, in step S1132, the variables x0, y0, dx, and dy for the image point can be determined. In the following step S1133, a polynomial fit can be applied to the variables x0, y0, dx, and dy. This can thus be used to determine a set of functions that assign the direction of the incident light beam to each image point of the image data captured by the image capture device.

[0112] Optionally, the camera calibration method can be used to determine Figure 8 The relative spatial positions of the contact points 51 are shown in exemplary form in FIG. . For this purpose, the display device 20 can be configured to display a monochrome background or a background of constant brightness as a test structure. The image capture device captures the display without the lens inserted. In this case, the contact points produce a shadow (e.g. a circle in the case of a contact sphere), which is captured by the image capture device and included in the image data. The calculation unit can be implemented to determine the positions of the contact points 51 based on these image data. These positions can then be used as boundary conditions when determining the three-dimensional shape of the lens. When the contact points are observed by at least two cameras, the center points (relative positions) of these cameras can be determined by interpolation of the camera rays. The positions of the contact points can be used to specify an expected value for the position of the spectacle lens in the measurement volume for an algorithm for determining the shape of the spectacle lens. The advantages of this configuration include increased accuracy.

[0113] It should be understood that the explanations made above may be applied accordingly to the exemplary embodiments below, and vice versa. To avoid repetition, the following is particularly intended to discuss other aspects. The features of the aforementioned exemplary embodiments and the exemplary embodiments below may be advantageously combined with each other.

[0114] The inventors have realised that the concepts described herein may also be used advantageously for measuring the cornea. Figure 12Shown is a schematic cross-sectional illustration of an eye 1200. The eye comprises a cornea 1201, an iris 1202, a pupil 1203, and a lens 1204. Figure 13 A plan view of the eye is shown with images representing the iris 1202 and pupil 1203. However, in this case, the primary cause of refractive error is not the lens 1204 but the cornea 1201. The primary cause of a subject's refractive error may be the corneal curvature. Therefore, it is desirable to be able to objectively determine the shape of the cornea.

[0115] Figure 14 A schematic illustration of an apparatus for measuring the cornea of ​​a subject according to another aspect of the present disclosure is shown. The apparatus may include the following: an image capture device (30) configured to capture image data of an iris (1202) of the subject from a plurality of (known) viewpoints via an imaging beam path (32) passing through the cornea (1201); and a computing unit (40). The computing unit is configured to: provide a mathematical model of the anterior segment of the subject's eye, the mathematical model comprising mathematical models of the cornea and the iris; identify and register image features of the iris present in a plurality of images of the image data; determine a deviation between an actual position of the image features of the iris in the images captured from the plurality of viewpoints and an expected position of the image features of the iris in the images captured from the plurality of viewpoints taking into account the relative positions of the mathematical model of the cornea and the iris; adapt parameters of the mathematical model of the cornea in such a way that the deviation is minimized; and determine a measurement variable of the cornea based on the adapted mathematical model of the cornea.

[0116] The image capture device 30 may also have Figure 1 The same or similar configuration as described above. The image capture device captures image data of the iris 1202 via a beam path passing through the cornea 1201. In order to capture image data from different known viewpoints, the camera 33 can be positioned successively at different known positions. For this purpose, a positioning device (not shown) can be provided. As an alternative or in addition thereto, a plurality of cameras 33, 34 can be provided, which capture image data in parallel. The advantages of parallel capture include that the user's eyes do not need to move between different measurements.

[0117] The inventors have recognized that the cornea 1201, located between the iris 1202 and the image capture device 30, can be calculated without knowing what the iris 1202 looks like. The iris 1202 has an unknown structure or pattern. However, the iris 1202 is typically very organized. The inventors have recognized that a large number of image features of the iris can be identified and then their positions evaluated in multiple images of image data recorded from different locations. To this end, a system of equations can be established based on the imaging beam path 32 captured at corresponding known locations; from this, the shape of the cornea 1201 can be calculated.

[0118] Figure 15 and Figure 16 The association or correlation of unknown image features in images of the iris recorded from different viewpoints is shown. Figure 15 The left image shows a view through the cornea from a first position, e.g. Figure 14 A first image representation 1500a of the iris 1202 recorded by the camera 33 in FIG. Figure 16 The right image shows a view through the cornea from a second position, for example, through Figure 14 15. A second image representation 1500b of the iris 1202 recorded by the camera 34 in FIG. 15. Because the iris is generally a very organized area, a correlation 1502 can be determined between the same initial points 1501a and 1501b of the iris 1201. Reference numerals 1503a and 1503b, connected by 1502′, designate another example of corresponding points. This correlation 1500 can be performed for a large number of images 1500a to 1500d and image points, such as Figure 16 As shown in .

[0119] Based on this correlation or association analysis, a large number of beam paths can be reconstructed, e.g. Figure 14 As is apparent from the beam path 32 shown, the beam of light originating from the same image point on the iris 1202 passes through different points of the cornea 1201 and is captured at different positions by the image capture device 30. If the same starting point is now identified in the image representation, a statement can be made about the cornea 1201, which is located between the starting point on the iris 1202 and the entrance openings of the cameras 33, 34, as described above with reference to Figure 14 described.

[0120] Figure 17A flowchart illustrating an embodiment of a method for measuring a subject's cornea is provided, which may aid in understanding the present invention. Calibration of the camera system may be performed in an optional previous step. However, calibration may already be performed by the manufacturer. In a first step 1701, image data of the subject's iris may be captured from multiple viewpoints via an imaging beam path passing through the cornea. In a second step 1702, a mathematical model of the subject's anterior eye may be provided, including a mathematical model of the cornea (and the relative position of the iris relative to the cornea). In a third step 1703, image features of the iris present in multiple images (preferably all images) of the image data may be identified and registered (or designated in the images). In a fourth step 1704, deviations between the actual positions of the image features of the iris in the images captured from the multiple viewpoints and the expected positions of the image features of the iris in the images captured from the multiple viewpoints, given the mathematical model of the cornea and the relative position of the iris, may be determined. In a fifth step 1705, parameters of the mathematical model of the cornea may be adapted to minimize these deviations. Preferably, steps 1703 and 1704 may be repeated iteratively. In a sixth step, measured variables of the cornea can now be determined based on the mathematical model of the corneal adaptation. By way of example, the refractive power or astigmatism can be evaluated.

[0121] In summary, the solution disclosed herein may contribute in particular to the simplified contactless measurement of a lens element arranged in a measurement volume or contactless measurement of the cornea in the field of ophthalmic optics, in particular reducing injuries to light-sensitive users.

[0122] Other examples are described below:

[0123] Example 1. A device (10) for measuring the optical effect of an optical lens (100) arranged in a measurement volume (200), comprising:

[0124] - a display device (20) configured to display the test structure (21);

[0125] - an image capture device (30) configured to capture image data of the test structure from a plurality of viewpoints (31, 31', 31") via an imaging beam path (32) passing through the lens (100); and

[0126] - a calculation unit (40), wherein the calculation unit is configured to:

[0127] - determining the three-dimensional shape of the lens (100) based on the image data; and

[0128] - calculating the optical effect of the lens (100) based on the three-dimensional shape of the lens;

[0129] The lens (100) is a spectacle lens and the optical effect of the spectacle lens is calculated for a given wearing position of a user.

[0130] Example 2. The apparatus of Example 1, wherein the image capturing device (30) comprises a first camera (33) and a second camera (34), wherein the first camera (33) is configured to capture first image data from a first viewpoint, and the second camera (34) is configured to capture second image data from a second viewpoint; and wherein the computing unit (40) is configured to determine a three-dimensional shape of the lens (100) based on the first image data and the second image data.

[0131] Example 3. A device as described in any of the preceding examples, characterized in that the computing unit (40) is configured to calculate the optical effect of the spectacle lens for a specific wearing position of the user, which is different from the measurement position for capturing the image data.

[0132] Example 4. A device as described in any of the preceding examples, characterized in that the calculation unit (40) is configured to iteratively determine the three-dimensional shape of the lens (100) by means of an integration method.

[0133] Example 5. An apparatus as described in any of the preceding examples, characterized in that the computing unit (40) is configured to determine the three-dimensional shape of the lens (100) based on back-tracing the light beam entering the image capture device (30).

[0134] Example 6. An apparatus as described in any of the preceding examples, characterized in that determining the three-dimensional shape of the lens (100) includes dividing the front surface and / or back surface (102, 103) of the lens into surface elements (106, 108) and determining the alignment of these surface elements.

[0135] Example 7. The apparatus of Example 6, wherein the computing unit (40) is implemented to determine the three-dimensional shape of the front surface (102) and the back surface (103) of the lens (100) based on the alignment of the surface elements.

[0136] Example 8. A device as described in any of the preceding examples, characterized in that the computing unit (40) is configured to determine the three-dimensional shape of the lens (100) taking into account the boundary conditions of the parameterized area on the front surface (102) or the back surface (103) of the lens.

[0137] Example 9. The device of Example 8, wherein the parameterized region comprises a sphere, a torus, or a segment thereof.

[0138] Example 10. A device as described in any of the preceding examples, characterized in that the computing unit (40) is configured to further determine the three-dimensional shape of the lens (100) taking into account one or more known contact points (51) of the lens.

[0139] Example 11. A device as described in any of the preceding examples, characterized in that the calculation unit (40) is configured to determine the three-dimensional shape of the lens taking into account boundary conditions, wherein the boundary conditions are determined by reading information about the lens (100) to be measured.

[0140] Example 12. The apparatus of Example 11, wherein the boundary condition is determined by reading a marking or code (140) on the lens.

[0141] Example 13. A device as described in any of the preceding examples, characterized in that the calculation unit (40) is further configured to determine the spatial refractive power distribution of the lens (100) to be measured.

[0142] Example 14. The device of any of the preceding examples, wherein:

[0143] - a height adjustment device (150) configured to change the distance between the image capture device (30) and the display device (20); and

[0144] - wherein the calculation unit (40) is further configured to determine a beam direction of the light beam captured by the image capture device based on image data captured from different distances between the image capture device and the display device.

[0145] Example 15. A device for measuring the spatial refractive power distribution of an optical lens arranged in a measurement volume (200), comprising:

[0146] - a display device (20) configured to display the test structure (21);

[0147] - an image capture device (30) configured to capture image data of the test structure from a plurality of viewpoints (31, 31', 31") via an imaging beam path passing through the lens (100);

[0148] - an interface configured to receive lens geometry data describing the three-dimensional shape of the lens; and

[0149] - a calculation unit (40), wherein the calculation unit is configured to:

[0150] - calculating the spatial refractive power distribution of the lens (100) based on the image data and the lens geometry data.

[0151] Example 16. A device (10) for measuring the optical effect of an optical lens (100) arranged in a measurement volume (200), comprising:

[0152] - a display device (20) configured to display the test structure (21);

[0153] - an image capture device (30) configured to capture image data of the test structure from a plurality of viewpoints (31, 31', 31") via an imaging beam path (32) passing through the lens (100); and

[0154] - a calculation unit (40), wherein the calculation unit is configured to:

[0155] - determining the three-dimensional shape of the lens (100) based on the image data; and

[0156] - calculating the optical effect of the lens (100) based on the three-dimensional shape of the lens;

[0157] The calculation unit (40) is configured to determine the three-dimensional shape of the lens (100) further taking into account one or more known contact points (51) of the lens.

[0158] Example 17. A device (10) for measuring the optical effect of an optical lens (100) arranged in a measurement volume (200), comprising:

[0159] - a display device (20) configured to display the test structure (21);

[0160] - an image capture device (30) configured to capture image data of the test structure from a plurality of viewpoints (31, 31', 31") via an imaging beam path (32) passing through the lens (100); and

[0161] - a calculation unit (40), wherein the calculation unit is configured to:

[0162] - determining the three-dimensional shape of the lens (100) based on the image data; and

[0163] - calculating the optical effect of the lens (100) based on the three-dimensional shape of the lens;

[0164] The calculation unit (40) is configured to determine the three-dimensional shape of the lens taking into account boundary conditions, wherein the boundary conditions are determined by reading information about the lens (100) to be measured.

[0165] Example 18. A method (900) for measuring the optical effect of an optical lens (100) arranged in a measurement volume (200), the method comprising the following steps:

[0166] - providing a test structure (21) for display on a display device (20);

[0167] - capturing image data of the test structure from a plurality of viewpoints (31, 31', 31") via an imaging beam path (32) passing through the lens (100);

[0168] - determining the three-dimensional shape of the lens (100) based on the image data; and

[0169] - calculating the optical effect of the lens (100) based on the three-dimensional shape of the lens;

[0170] The lens (100) is a spectacle lens and the optical effect of the spectacle lens is calculated for a given wearing position of a user.

[0171] Example 19. A method (900) for measuring the optical effect of an optical lens (100) arranged in a measurement volume (200), the method comprising the following steps:

[0172] - providing a test structure (21) for display on a display device (20);

[0173] - capturing image data of the test structure from a plurality of viewpoints (31, 31', 31") via an imaging beam path (32) passing through the lens (100);

[0174] - determining the three-dimensional shape of the lens (100) based on the image data; and

[0175] - calculating the optical effect of the lens (100) based on the three-dimensional shape of the lens;

[0176] Therein, the three-dimensional shape of the lens (100) is determined taking into account one or more known contact points (51) of the lens.

[0177] Example 20. A method (900) for measuring the optical effect of an optical lens (100) arranged in a measurement volume (200), the method comprising the following steps:

[0178] - providing a test structure (21) for display on a display device (20);

[0179] - capturing image data of the test structure from a plurality of viewpoints (31, 31', 31") via an imaging beam path (32) passing through the lens (100);

[0180] - determining the three-dimensional shape of the lens (100) based on the image data; and

[0181] - calculating the optical effect of the lens (100) based on the three-dimensional shape of the lens;

[0182] The three-dimensional shape of the lens is determined taking into account boundary conditions, wherein the boundary conditions are determined by reading information about the lens (100) to be measured.

[0183] Example 21. A computer program product comprising instructions which, when executed by a computer, cause the computer to implement the method (900) of any one of Examples 18 to 20.

Claims

1. An apparatus (1) for measuring the cornea of ​​a subject, comprising: - an image capture device (30) configured to capture image data of the subject's iris (1202) from a plurality of viewpoints via an imaging beam path (32) passing through the cornea (1201); and - a calculation unit (40), wherein the calculation unit is configured to: - providing a mathematical model of the anterior segment of the subject's eye, the mathematical model comprising mathematical models of the cornea (1201) and the iris (1202); - identifying and registering image features of the iris present in a plurality of images of said image data; - determining a deviation between an actual position of an image feature of the iris (1202) in images captured from a plurality of viewpoints and an expected position of the image feature of the iris in images captured from a plurality of viewpoints taking into account a mathematical model of the cornea and the relative position of the iris; - adapting the parameters of the mathematical model of the cornea so as to minimize said deviation; and - Determining measured variables of the cornea based on an adapted mathematical model of the cornea.

2. The device (1) as claimed in claim 1, wherein The calculation unit (40) is configured to evaluate the refractive power or astigmatism as a measured variable of the cornea based on an adapted mathematical model of the cornea.

3. The device (1) as claimed in any one of the preceding claims, wherein The mathematical model includes the relative position of the iris with respect to the cornea.

4. The device (1) as claimed in claim 1 or 2, wherein The apparatus is configured to calculate the cornea (1201) located between the iris (1202) and the image capture device without prior knowledge of what the iris (1202) looks like.

5. The device (1) as claimed in claim 1 or 2, wherein Correlation of a priori unknown image features in images of the iris recorded from different viewpoints is performed.

6. The device (1) as claimed in claim 1 or 2, wherein The calculation unit (40) is configured to calculate the shape of the cornea (1201) using a set of equations established based on the imaging beam path (32) captured at corresponding known positions by means of the image capture device (30).

7. The device according to claim 1 or 2, characterized in that The image capture device (30) has a first camera (33) and a second camera (34), wherein the first camera (33) is configured to capture first image data from a first viewpoint, and the second camera (34) is configured to capture second image data from a second viewpoint; and wherein the computing unit (40) is configured to determine the three-dimensional shape of the cornea (1201) based on the first image data and the second image data.

8. The device according to claim 1 or 2, characterized in that The calculation unit (40) is configured to iteratively determine the three-dimensional shape of the cornea (1201) by means of an integration method.

9. The device according to claim 8, characterized in that Determining the three-dimensional shape of the cornea (1201) includes dividing the anterior and / or posterior surfaces of the cornea into surface elements and determining the alignment of the surface elements.

10. The device according to claim 1 or 2, characterized in that The calculation unit (40) is configured to determine the three-dimensional shape of the cornea (1201) taking into account a boundary condition that the front surface or the back surface of the cornea (1201) has a parameterizable area.

11. The device according to claim 10, characterized in that The parameterizable region includes a sphere, a torus, or a segment of a sphere or a torus.

12. The apparatus of claim 1 or 2, wherein: The computing unit (40) is configured to determine the three-dimensional shape of the cornea (1201) further taking into account one or more known contact points (51) of the cornea.

13. A method (1700) for corneal measurement of a subject, comprising the steps of: - capturing (1701) image data of the subject's iris (1202) from a plurality of viewpoints via an imaging beam path (32) passing through the cornea (1201); and - providing (1702) a mathematical model of the anterior segment of the subject's eye, the mathematical model comprising mathematical models of the cornea (1201) and the iris (1202); - identifying and registering (1703) image features of the iris present in a plurality of images of said image data; - determining (1704) a deviation between an actual position of an image feature of the iris (1202) in images captured from a plurality of viewpoints and an expected position of the image feature of the iris in images captured from a plurality of viewpoints taking into account a mathematical model of the cornea and the relative position of the iris; - adapting (1705) the parameters of the mathematical model of the cornea so as to minimize said deviation; and - Determining (1706) measured variables of the cornea based on the adapted mathematical model of the cornea.

14. The method for corneal measurement according to claim 13, comprising the preceding step of calibrating the image capture device (30) for capturing image data of the iris (1202) from a plurality of viewpoints.

15. A computer program product comprising instructions which, when executed by a computer, cause the computer to carry out the method (1700) as claimed in claim 13.

Images