Recording 3D image data using light sectioning process

Abstract

To provide a method of compensating an oblique light incidence on light reception elements and implementing smaller angles of incidence on an image sensor to improve light sensitivity.SOLUTION: A camera for recording 3D image data using a light sectioning process, according to the invention, comprises: an illumination unit for projecting a light pattern in a focal plane 28; an image sensor 22 having a plurality of light reception elements in an image plane; a reception optics 26 arranged upstream of the image sensor 22 and having an objective plane; and a control and evaluation unit 24 configured to generate 3D image data by evaluating the light pattern in a captured image of the image sensor 22, where the image plane is tilted with respect to the focal plane. The reception optics 26 has at least one metaelement 30 for compensating oblique light incidence on the light reception elements.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a camera and a method for recording three-dimensional image data in the light section method according to the preambles of claims 1 and 15, respectively. [Background technology]

[0002] In light section methods, a light pattern is projected into the detection area and the height profile of the object is inferred from the distortion by triangulation. Laser triangulation using a line light source is particularly popular. Typically, detection is performed during relative motion and two-dimensional height profiles at each time point are combined into three-dimensional image data. Quite often, additional level measurements are made and used to capture light and dark images or textures.

[0003] FIG. 8 shows a known Scheimpflug arrangement, which allows a laser line to be sharply photographed over the entire measurement range, thereby obtaining valuable three-dimensional image data. In this arrangement, a camera 100 with an objective lens 102 is assembled so that its image plane 104, the objective lens main plane 106, and the sharp or focal plane 108 intersect with each other in a common straight line. In this case, however, the light strikes the image sensor of the camera 100 obliquely due to the Scheimpflug arrangement and the chief ray angle of the objective lens 102. While the effect of the Scheimpflug arrangement concerns all pixels equally, the chief ray angle acts individually on each pixel, i.e. it is still 0 degrees at the central pixel and increases from there towards the periphery of the image sensor. The Scheimpflug arrangement therefore reduces the light efficiency, since not all the light reaches each pixel due to the oblique light incidence. In addition, a camera assembled with the Scheimpflug arrangement is rather large.

[0004] FIG. 9 illustrates a conventional solution for increasing the light sensitivity of an image sensor. FIGS. 9(a)-(c) respectively show an exemplary pixel 110, its photosensitive surface 112, and a microlens 114 placed in front of it. In the case of perpendicular light incidence as in FIG. 9(a), the light is converged by the lens onto the photosensitive surface 112. However, in the case of oblique light incidence as in FIG. 9(b), a lateral shift occurs, and the light is partially or completely off the photosensitive surface 112. To compensate for this, the microlens 114 can be shifted by δx with respect to the photosensitive surface 112 as in FIG. 9(c). However, the shift δx must match the angle of incidence. This requires a very expensive and specialized design, which must be redone for each sensor variant. The light that is off the photosensitive surface 112 not only reduces the light sensitivity of the image sensor, but also generates stray light, which further deteriorates the image capture.

[0005] Another undesirable effect of oblique light incidence is multiple reflections within the glass cover, which does not occur with normal light incidence, only harmless back reflections in the direction of the light source that do not enter the image sensor. Anti-reflection coatings also show an angle dependency.

[0006] The work in [1] discusses various uses of wedge prisms. In particular, they can be used to tilt the image field or to correct this tilt. However, this action always involves aberrations. They can eliminate either coma or astigmatism, but never both. Therefore, their use in laser triangulation (which the work does not discuss) would introduce additional measurement errors.

[0007] The work in Non-Patent Document 2 has nothing to do with laser triangulation but deals with so-called metalenses and space plates. Metalenses are extremely thin optical elements with lens action, equipped with special nanostructures to influence the light path. Space plates, on the other hand, use a similar technique to target the area between the lenses, since metalenses must first be kept at a certain distance from each other, just like classical lenses. Space plates reduce this distance, further reducing the overall depth of the optical system. One special method for creating such nanostructures is nanoimprinting.

[0008] US Pat. No. 5,399,433 discloses a triangulation sensor using an optical meta-element in the receiving path to compensate for various adverse effects of triangulation. Such triangulation sensors perform only scalar or one-dimensional measurements and should not be confused with the types of cameras mentioned at the beginning for recording three-dimensional image data by light section method or laser triangulation. No camera-specific issues such as the Scheimpflug arrangement or optimization of the image sensor in two axes are addressed in US Pat. No. 5,399,433 in particular, in which the deviation of the receiving spot in the near field is limited by an optical meta-element.

[0009] Patent Document 3 introduces a LARP device (Laser Activated Remote Phosphor). In the document, a wedge prism, a metalens, and a Scheimpflug arrangement are mentioned in various embodiments, but they are not closely related to each other. This document has nothing to do with laser triangulation. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] DE 10 2021 119 423 A1 [Patent Document 2] DE 10 2021 122 418 A1 [Patent Document 3] US 2019 / 0170314 A1 [Non-patent literature]

[0011] [Non-Patent Document 1] Howard, James W.: "Formulas for the coma and astigmatism of wedge prisms used in converging light", Applied optics 24.23 (1985): 4265-4268 [Non-Patent Document 2] Reshef, Orad, et al. "An optic to replace space and its application towards ultra-thin imaging systems", Nature communications 12.1 (2021): 1-8 Summary of the Invention [Problem to be solved by the invention]

[0012] It is therefore an object of the present invention to improve the acquisition of three-dimensional image data in the light section method. [Means for solving the problem]

[0013] This problem is solved by a camera and a method for recording three-dimensional image data in a light section method as claimed in claims 1 and 15, respectively. The light section method generally refers to the acquisition of three-dimensional image data from the distortion of a projected light pattern by the contour of an object using triangulation, in particular laser triangulation, in which a line of light is projected as a light pattern. A light source, in particular a laser, projects a light pattern or a line of light in a focal plane. An image sensor with a number of light receiving elements or pixels, typically arranged in a matrix, images the light pattern on the object on which the light pattern falls. A receiving optical system with an objective main surface is arranged in front of the image sensor. A control and evaluation unit determines the three-dimensional image data by evaluating the profile of the captured light pattern. The image plane is tilted with respect to the focal plane.

[0014] The basic idea from which the invention begins is to provide the receiving optics with at least one optical meta-element, which compensates for oblique light incidence on the receiving element. Oblique light incidence occurs in particular due to the tilt between the image plane and the focal plane and / or the respective chief ray angle, as discussed at the beginning. Depending on the embodiment, the meta-element acts on the reflected light bundle in different ways and replaces and / or supplements the receiving optics. To this end, the meta-element comprises metasurfaces and / or metamaterials, i.e. nanostructures that perfectly target and shape the wavefront of the reflected light bundle. In the case of metasurfaces, such nanostructures are provided on the surface, while in the case of metamaterials, the appropriate properties are achieved by means of nanostructures in a layered system or solid body.

[0015] The present invention has the advantage that a smaller angle of incidence on the image sensor can be realized, which improves the light sensitivity and, in some embodiments, mitigates the disturbing side effects of the Scheimpflug arrangement or, in some embodiments, the advantages of the Scheimpflug arrangement can be obtained without a real Scheimpflug arrangement, which in turn allows for a more compact geometry and is easier to manufacture. In some embodiments, the height resolution can be linear. The optical meta-element makes it easier to create variants, since for other geometry or other focal planes, one can simply use a different meta-element, or even the meta-element can be adapted to the other geometry or can perform its function in the same way in the other geometry. The optical meta-element can fulfill the tasks of the receiving optics with smaller lens errors or compensate for the lens errors if an objective lens is still used in the receiving optics. The multiple reflections in the glass cover mentioned at the beginning can be avoided thanks to the optical meta-element.

[0016] The meta-element preferably creates a prism effect, whereby the angle of incidence of incoming received light is altered before it impinges on the image sensor, such that oblique light incidence on the image sensor becomes normal light incidence, or at least the oblique angle of incidence is reduced towards normal light incidence.

[0017] The meta-element preferably has different optical behavior across the photo-sensitive elements. Individual compensation for each photo-sensitive element can be considered in the meta-element, but is not feasible at all by classical means. It is conceivable to target groups of photo-sensitive elements, such as rows or columns, and compensate in the same way within each group in the meta-element.

[0018] The receiving optics preferably comprises a microlens array arranged in front of the image sensor, thereby combining the action of the microlens array, which focuses the received light onto the respective photosensitive areas of the image sensor, with the action of the optical meta-element provided according to the invention.

[0019] The microlenses of the microlens array preferably have an offset with respect to the light receiving elements. This offset is conventionally used to compensate for oblique light incidence, but in the present invention, the optical meta-element fulfills this role. Therefore, a standard microlens array without offset can be used, which has the advantage of flexibility in use in different camera variants and cost. Nevertheless, this embodiment combining the offset of the microlenses and the use of a meta-element is possible.

[0020] The meta-element preferably directs light perpendicularly to each microlens, thereby achieving even perfect compensation for oblique light incidence.

[0021] The meta-element preferably additionally has the functionality of a microlens field. In this embodiment, it is possible to dispense with the microlens field and still obtain the same optical effect of focusing the respective light-sensitive areas of the light-receiving elements. The meta-element itself ensures that the light is properly focused on the light-sensitive areas of the image sensor, in addition to compensating for oblique light incidence.

[0022] In another possible combination, the metaelement only partially replaces the function of the microlens field, so that the microlens field and the metaelement complement each other. It is further conceivable that two or more metaelements each share the desired optical functionality.

[0023] The receiving optics preferably comprises a receiving lens, i.e. in such an embodiment a classical receiving lens or a classical receiving objective lens is still present.

[0024] The image sensor is preferably tilted relative to the receiving lens in a Scheimpflug configuration, so that the image plane, the objective lens principal plane of the receiving lens, and the focal plane intersect with each other on a common straight line. The optical meta-element ensures that the received light is incident on the receiving element as perpendicularly as possible, despite the tilt of the image sensor.

[0025] The image sensor and the receiving lens are preferably arranged relative to each other such that the image plane and the objective lens main plane are parallel. As an alternative, the Scheimpflug arrangement is avoided from a physical point of view. However, the optical meta-element mimics the advantageous optical effects of the Scheimpflug arrangement.

[0026] The meta-element is preferably configured to focus light from the focal plane onto the image sensor. In this way, the optical meta-element preferably assumes the function of a receiver lens, either alone or in combination with a receiver lens or as part of the receiver optics. As mentioned above, there may be multiple meta-elements, e.g., one meta-element for the receiver lens function and another meta-element for compensating for oblique light incidence, or a single meta-element for both.

[0027] The meta-element is preferably an active meta-element, meaning that it is a meta-element whose optical properties can be adjusted, so that it can be adapted to a particular focal plane or tilt, or to a particular camera or shooting situation. Thus, for example, it is not necessary to manufacture multiple meta-elements for camera variations or specific applications, or at least within certain limits, camera variations can be eliminated altogether by adaptation with the active meta-element.

[0028] The receiving optics preferably comprises a space plate. The corresponding German term has not yet been coined. A space plate is also a metamaterial, but it does not primarily aim at changing the wavefront in response to tilt or lens action. Rather, it realizes a longer optical path in a smaller physical space, so to speak, in order to allow the optical elements, in particular the metalenses, to be arranged closer together side by side. In particular, it is conceivable to combine the action of the space plate with that of the optical metaelement by providing a metasurface on the front and / or back side of the space plate. The use of a space plate allows for a very compact construction in embodiments in which the optical metaelement also becomes the receiving lens and assumes a double function. For further details on the space plate, the reader is referred to the supplementary work of the aforementioned non-patent document 2.

[0029] The metaelement is preferably configured for multi-focal imaging, which allows for a clear capture of various focal planes with different inclinations. This is of interest when capturing multiple regions of interest (ROIs), especially when there are multiple laser lines or when lines of the image sensor are used for special purposes (e.g. a few peripheral lines as color lines).

[0030] It is desirable for the metaelement to have anamorphic properties, i.e. different focal properties in the two axes of the image sensor. Classical optical means would require additional lenses for this, with the corresponding assembly space and costs. The metaelement can fulfill both of these requirements if necessary.

[0031] The method according to the invention can be implemented in a similar manner and thus exhibits similar advantages, such advantageous features being exemplarily recited, for example but not exclusively, in the dependent claims following the independent claims of this application.

[0032] The invention, together with further characteristics and advantages thereof, will now be described in greater detail, exemplarily on the basis of embodiments, with reference to the accompanying drawings, in which: FIG. [Brief description of the drawings]

[0033] [Figure 1] General view of a camera and its detection area for capturing 3D images by light section method or by laser triangulation. [Diagram 2] FIG. 13 is a schematic diagram of a camera embodiment in a Scheimpflug geometry for compensating for oblique light incidence with an optical meta-element. [Diagram 3] Schematic diagram of a camera embodiment that lacks the physical Scheimpflug arrangement but has the same kind of optical effect through optical meta-elements. [Figure 4] FIG. 13 is a schematic diagram of an embodiment of a camera in which an optical meta-element additionally takes over the function of a receiving lens. [Diagram 5] Schematic diagram of an embodiment of a camera with the addition of a space plate. [Figure 6] 1 is a schematic diagram of an embodiment of a camera having multiple projected illumination lines and a capture area. [Figure 7] Schematic diagram of a multi-focal embodiment of the camera. [Figure 8] Schematic diagram of a conventional Scheimpflug arrangement. [Figure 9] 1 is a schematic diagram of a conventional approach to using microlenses in front of an image sensor, particularly offset microlenses. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] FIG. 1 shows a general view of a camera 10 for capturing three-dimensional images by the light section method or by laser triangulation in an exemplary capture situation. The principle of laser triangulation is known per se and will only be briefly introduced. An illumination unit 12 generates a light fan 14 in the focal plane, which ultimately projects a light line onto the object 16 to be detected. The three-dimensional contour of the object 16 distorts the light line. By evaluating the shape of the light line in the captured images of the camera 10, the three-dimensional contour is inversely estimated, knowing the geometrical arrangement and the properties of the camera 10 and the illumination unit 12. In this case, only a two-dimensional height profile corresponding to the object cross section under the light line is obtained for each captured image. The light line is slowly guided along the object 16 by a relative movement (for example the movement of a conveyor belt 18). The three-dimensional image data 20 is obtained by continuously building up the two-dimensional height profile in this way.

[0035] FIG. 2 shows a schematic diagram of an embodiment of a camera 10 in a Scheimpflug arrangement. Of the camera 10, only the light receiving optics, which have not yet been described, the image sensor 22 with light receiving elements or pixels, which are not shown separately, and the control and evaluation unit 24, in which the triangulation evaluation takes place, are shown in a simplified manner. The control and evaluation unit 24 can be an internal computing unit, an external computing unit or a combination of both. Examples of internal computing units are microprocessors or digital computing modules such as Central Processing Units (CPUs), Field Programmable Gate Arrays (FPGAs), Digital Signal Processors (DSPs), Application-Specific Integrated Circuits (ASICs), AI processors, Neural Processing Units (NPUs), Graphics Processing Units (GPUs), etc. An external computing unit can be a control device or any form of computer, such as a notebook, a smartphone or a tablet, or it can be a local network, an edge device or the cloud.

[0036] The camera 10 is assembled in this embodiment in a Scheimpflug configuration. A single receiving lens 26 is depicted to represent the receiving objective lens. The Scheimpflug configuration means that the image plane of the image sensor 22, the objective lens main surface of the receiving lens 26, and the focal plane 28 intersect with each other on a common straight line, as already explained at the beginning in FIG. 8. A necessary but not sufficient condition for this is that the focal plane 28 is tilted with respect to the image plane.

[0037] To compensate for oblique light incidence on image sensor 22, there is an optical meta-element 30 placed in front of image sensor 22. Additionally, an optional microlens field 32 can be used, preferably between optical meta-element 30 and image sensor 22. The microlens can be a standard component with a centered microlens as in FIG. 9(a) or can be offset as in FIG. 9(c). Note that the latter is no longer necessary due to the presence of optical meta-element 30, but it is still conceivable that, for example, the offset and optical meta-element 30 could share the required angular compensation with each other.

[0038] The optical meta-element 30 comprises a meta-material or a meta-surface, the latter preferably fabricated by nanoimprinting. Conventional optical components such as lenses, prisms, waveplates or holograms are based on the propagation of light over distances much larger than the wavelength of the light fan 14 to form a wavefront. In this way, significant changes in the amplitude, phase or polarization of the light wave are gradually accumulated along the light path. In contrast, the optical meta-element 30 comprises a structure that can be considered as a very small anisotropic light diffuser or a resonator or optical antenna. The structures have dimensions and spacing in the nanometer range, much smaller than the wavelength of the light fan 14. Thus, by introducing spatial changes in the optical response of the light diffuser by the nanostructures, the optical meta-element 30 forms an arbitrary shaped light wavefront with sub-wavelength resolution by Huygens' principle. This allows the optical behavior, in particular that of a lens or prism, to be mimicked. One feature is the high flexibility to achieve desired output wavefronts and thus a great variety of optical effects by tailored nanostructures. Materials with appropriate transmission properties are used depending on the wavelength range, for example titanium dioxide, silicon nitride or gallium phosphide in the visible spectral range, aluminum nitride in the ultraviolet spectral range, chalcogenide alloys in the mid-wave infrared range, and silicon in the long-wave infrared range.

[0039] In the camera 10, the optical meta-element 30 is expected to compensate the angle of incidence of the received light on the image sensor 22, in particular for each individual light receiving element. This is similar to the action of a wedge prism, but in the meta-material this effect can be achieved without aberrations. The simulated wedge prism can set a unique refraction angle for each individual light receiving element so that the light is perpendicular to the light receiving element. In this case, the oblique light incidence based on the Scheimpflug arrangement and / or the chief ray angle depending on the position on the image sensor can be compensated. Once the reference values ​​for this specific optical effect are determined, the required nanostructures can be calculated and created. With classical optical elements, such compensation is not possible with the structure size of the individual pixels. Moreover, the optical meta-element 30 can be easily exchanged to reproduce other variations or application situations of the camera. The required optical effects can be realized in a single optical meta-element 30 as described, or distributed among two or more optical meta-elements.

[0040] FIG. 3 is a schematic diagram of an embodiment of the camera 10 without the physical Scheimpflug arrangement, but with the same kind of optical effect by the optical meta-element 30. The optical effect of the Scheimpflug arrangement is that the image distance, i.e. the distance between the image-side principal plane and the image sensor 22, varies across the light-receiving elements of the image sensor 22. This helps to compensate for the effect of the oblique object plane and the resulting changing object distance. A sharp image when the object distance changes can also be achieved by changing the focus position across the image sensor 22 instead of by the physical Scheimpflug arrangement. The optical meta-element 30 of this embodiment is constructed accordingly. That is, it generates a focus position for each light-receiving element that corresponds to the physical tilt position of the image sensor 22 in the Scheimpflug arrangement. The change in focus position by the optical meta-element 30 can also be generated for each light-receiving element individually, but preferably only along the height direction, i.e. along the direction in which the focal plane 28 is tilted with respect to the image plane of the image sensor 22. This can be called an emulated Scheimpflug arrangement using the optical meta-element 30. Additionally, it is possible to compensate the chief ray angle for each light receiving element in optical meta-element 30 in response to the optical action of the misaligned microlenses. See the description of the embodiment shown in FIG. 2 for this. The functions of the mimicked Scheimpflug arrangement and the chief ray angle compensation may be distributed among two or more optical meta-elements 30, or may be realized in a single optical meta-element 30.

[0041] FIG. 4 shows a schematic diagram of another embodiment of the camera 10. In contrast to FIG. 3, here the optical meta-element 30 additionally assumes the function of the receiving lens 26 or the receiving objective lens and is therefore arranged at a greater distance to the image sensor 22, approximately at the position of the previous receiving lens 26. This optical meta-element 30 thus acquires the additional focusing properties of a metalens, like the previous receiving lens 26. The function of the mimicked Scheimpflug arrangement described in FIG. 3 is superimposed on this focusing effect, in particular in combination with compensation of the chief ray angle. Here again, the various optical functions can be realized in a single optical meta-element 30 or distributed over at least two optical meta-elements, in particular here with another optical meta-element located closer to the image sensor 22. As an additional optical function to the same optical meta-element 30 or to another optical meta-element, the height resolution can be linearized. This is described in the patent documents 1 and 2 cited at the beginning, but this time it is transferred from a conventional one-dimensional sensor to the camera 10.

[0042] FIG. 5 shows a schematic diagram of an embodiment of the camera 10. In FIG. 4, the optical meta-element 30, which replaces the receiving lens 26, must be placed away from the image sensor 22. To achieve a more compact structure, a space plate 34 is now added. As already briefly explained at the beginning, the space plate 34 is a special optical meta-element that can replace a long optical path through air in a fairly narrow space. Thanks to the space plate 34, it is therefore again possible to place the optical meta-element 30 quite close to the image sensor 22. The entire receiving optics can then be realized with a minimum overall depth as a sandwich of the image sensor 22, the optional microlens field 32, the space plate 34 and the optical meta-element 30, in particular in a monolithic structure. The space plate can also be used in other embodiments, but the same compactness is not achieved there because the classical receiving lens 26 is still present.

[0043] 6 shows a schematic diagram of an embodiment of the camera in what can be called a reverse Scheimpflug arrangement. This is particularly suitable when there are several capture areas, which in the illustrated example are the two laser lines of the two lighting units 12a-b and the RGB area 36. To allow multiple measurements, the two laser lines are preferably offset from one another in the conveying direction. In this case, the focal plane is not the plane of the light fan 14a-b, which is no longer unique in the first place, but the base plane of the object (such as the surface of the belt conveyor 18). The illustrated arrangement is particularly suitable for flat objects, such as when inspecting wood.

[0044] FIG. 7 shows a schematic diagram of a multi-focal embodiment of the camera 10. It is based on the embodiment described in FIG. 3 and can be transferred to other embodiments. The optical meta-element 30 supports multiple focal positions, so that multiple regions of interest with different triangulation parameters or focal planes 28a-b can be captured. This allows, for example, line-by-line color imaging in addition to laser triangulation. It also allows the use of the inverse Scheimpflug arrangement shown in FIG. 6 for various object distances or object heights, not just flat objects.

[0045] Another variant, without its own illustration, is to provide the receiving optics with anamorphic properties, i.e. different focal properties in two axes of the image sensor 22, via the optical meta-element 30. This is particularly suitable for the embodiment shown in FIG. 4. Through anamorphic properties, for example, the width of the image can be compressed or expanded at the same height. If you try to do this with classical lenses, you will have to incur very high costs due to the additional lens and the additional assembly space required for it.

Claims

1. A camera (10) for recording three-dimensional image data (20) in a light section method, the camera (10) comprising: an illumination unit (12) for projecting a light pattern (14) in a focal plane (28); an image sensor (22) having a number of light receiving elements in an image plane; a light receiving optical system (26) arranged in front of the image sensor (22) and having an objective lens main surface; and a control and evaluation unit (14) configured to generate the three-dimensional image data (20) by evaluating the light pattern (14) in an image captured by the image sensor (22), the image plane being inclined with respect to the focal plane (28), The receiving optical system (26) includes at least one optical meta-element (30) that compensates for oblique light incidence on the receiving element. A camera (10) comprising:

2. The camera (10) of claim 1 , wherein the meta-element (30) creates a prism effect.

3. The camera (10) of claim 1 , wherein the meta-element (30) has a different optical effect across the light receiving element.

4. The camera (10) of claim 1, wherein the receiving optics (26) comprises a microlens array (32) disposed in front of the image sensor (22).

5. The camera (10) of claim 4, wherein the microlenses of the microlens array (32) are offset relative to the light receiving elements.

6. The camera (10) of claim 4, wherein the meta-element (30) directs light perpendicularly to each microlens.

7. The camera (10) of claim 1 , wherein the meta-element (30) additionally comprises a function of a microlens field.

8. The camera (10) of claim 1, wherein the receiving optics comprises a receiving lens (26).

9. The camera (10) of claim 8, wherein the image sensor (22) is tilted relative to the receiving lens (26) in a Scheimpflug configuration.

10. 9. The camera (10) of claim 8, wherein the image sensor (22) and the receiving lens (26) are arranged relative to each other such that an image plane and a principal objective lens plane are parallel.

11. The camera (10) of claim 1, wherein the meta-element (30) is configured to focus light from the focal plane (28) onto the image sensor (22).

12. The camera (10) of claim 1 , wherein the meta-element (30) is an active meta-element whose optical properties can be adjusted.

13. The camera (10) of claim 1, wherein the receiving optics (26) comprises a space plate (34).

14. 10. The camera (10) of claim 1, wherein the meta-element (30) is configured for multi-focal image capture and / or the meta-element (30) has anamorphic properties.

15. A method for recording three-dimensional image data (20) according to the principle of the light section method, in which a light pattern (14) is projected in a focal plane (28), an image sensor (22) having a number of light receiving elements images the light pattern (14) in an image plane through a light receiving optical system (26) having an objective lens main surface arranged in front of the image sensor (22), and the imaged light pattern (14) is evaluated to generate the three-dimensional image data (20), the image plane being inclined with respect to the focal plane (28), The receiving optical system (26) includes at least one optical meta-element (30) that compensates for oblique light incidence on the receiving element. The method comprising:

Images