The invention relates to a method for producing at least one optical lens according to claim 1 particularly suitable for being installed in an optic for eye tracking devices, in the eye tracking device cameras.

It is well known that optical lenses for glass optics have to be ground or injected into a suitable mold in an injection-molding process.

These grinding or casting processes make it possible to meet various requirements for the quality of the imaging properties of the lens. This can be low distortion or the most uniform brightness possible over the entire imaging plane of the lens.

The requirements on the quality of the imaging properties are different for an imaging or an image-processing system. In an imaging system, the image quality should generally meet the expectations of the viewer. In the case of an image- processing system, this expectation is different, since it only has to be sufficient for the intended application and any imaging errors can be taken into account in the evaluation.

The disadvantage of known manufacturing processes for optical lenses is that they become more and more complex to produce as miniaturization increases. For example, when grinding optical lenses with decreasing size, the demands on the precision of the manufacturing process become higher and higher. Also in injection - molding processes, the requirements increase as the size of the lenses decreases, since, for example, the boundary surface between lens material and mold increases in relation to the volume.

It is therefore the object of the invention to specify a method for the production of at least one optical lens of the type mentioned above, with which the disadvantages mentioned can be avoided, with which a further miniaturization of the optical lenses is possible with simultaneous reduction of the costs and production in large numbers.

According to the invention, this is achieved by the features of claim 1.

This leads to the advantage that small optical lenses can be produced with low effort and in large quantities with a quality sufficient for at least one image- processing system. The effect is used here that a liquid drop, due to a balance of forces, naturally takes on a shape that forms an optical lens. This lens shape and thus the properties of the lens can be influenced by the appropriate selection of the boundary conditions. The lens shape is therefore no longer imposed from the outside by grinding or a casting mold, but adjusts itself automatically. Accordingly, there is no need for expensive processing of the lens surface by grinding or surface defects caused by the influence of a casting mold. After curing the lens material, a finished lens is already available. Furthermore, this technology is easy to miniaturize, since the size of the lens depends on the amount of the drop of lens material and the lens shape arises automatically.

The invention further relates to an optical component suitable to be installed in an optic for eye tracking device, comprising at least one optical lens according to claim 9.

The invention further relates to a device for manufacturing optical lenses suitable to be installed in an optic for eye tracking devices according to claim 10.

The invention therefore also has the object of specifying a device for the production of optical lenses suitable to be installed in an optic for eye tracking device of the type mentioned above, with which the disadvantages mentioned above can be avoided, with which miniaturization of the optical lenses is possible while simultaneously reducing costs and production in large quantities.

According to the invention, this is achieved by the features of claim 10.

The advantages of the device correspond to the advantages of the above- mentioned method.

The invention further relates to an eye tracking device comprising an optical component according to claim 15.

The subclaims relate to further advantageous features of the invention.

Explicit reference is hereby made to the wording of the claims, whereby the claims are inserted at this point by reference in the description and are deemed to be reproduced verbatim. If a photopolymer is used as the liquid lens material, wherein the drop of the photopolymer is cured by means of a lamp, the advantage is that the time of curing can be specified exactly.

If the imaging properties of the lens material in the lens shape on the lens carrier are measured by means of an image-capturing optical system, the advantage is that the imaging properties of the lens material in both liquid and solid state can be detected already during the manufacturing process, individually for each lens manufactured.

The invention is described in more detail with reference to the enclosed drawing, in which only one preferred embodiment is shown as an example.

Fig. 1 shows a preferred embodiment of the device for the production of optical lenses as a schematic representation.

Fig. 1 shows a preferred embodiment for a device for a method for the production of at least one optical lens 1, wherein at least one drop 2 of a liquid lens material is applied to a lens carrier 3 in such a way that the liquid lens material on the lens carrier 3 assumes a lens shape, wherein subsequently, to form the at least one optical lens 1, the at least one drop 2 of the liquid lens material is cured.

A lens 1 is an optical element with imaging properties that is bounded by two refractive surfaces. The method can be used to produce a single optical lens 1, wherein it is preferably provided that several optical lenses 1 are produced at the same time.

In particular, a predetermined amount of liquid lens material is applied to a lens carrier 3 for production. The liquid lens material is the material which later forms the optical lens 1, but is still liquid before curing. Accordingly, the lens material must be transparent at least in the solid state.

The liquid lens material is applied so that a single drop 2, in particular, is formed. Due to a natural equilibrium of forces, the drop 2 of liquid lens material on the lens carrier 3 automatically assumes a shape that is predetermined by the existing boundary conditions.

Then the at least one drop 2 of the liquid lens material is cured, resulting in the formation of a solid optical lens 1 from the lens material. Curing designates the process of solidifying the lens material.

This leads to the advantage that small optical lenses 1 can be produced with little effort and in large quantities, with a quality sufficient for at least one image- processing system. The effect is used here that a liquid drop 2, due to a balance of forces, naturally assumes a shape that forms an optical lens 1 . This lens shape and thus the properties of the lens 1 can be influenced by the appropriate selection of the boundary conditions. The lens shape is therefore no longer imposed from the outside by grinding or a casting mold, but adjusts itself automatically. Accordingly, there is no need for expensive processing of the lens surface by grinding or surface defects caused by the influence of a casting mold. After curing of the lens material, a finished lens 1 is already available. Furthermore, this technology is easy to miniaturize, since the size of lens 1 depends on the amount of the drop of lens material and the lens shape arises automatically.

Furthermore, an optical component for a camera comprising at least one optical lens 1 is provided.

Furthermore, a device for producing optical lenses 1 is provided, comprising a holder 5 for the lens carrier 3, and at least one application device 6 for applying at least one drop 2 of a liquid lens material on a lens carrier 3 arranged on the holder 5. The holder 5 is provided so that the lens carrier 3 is arranged on it, in particular fixed. The application device 6 is designed to apply drops 2 of the liquid lens material to the lens carrier 3.

As mentioned at the beginning, the shape of the drop 2, and thus also the shape of the solid lens 1 after curing, is determined by the boundary conditions. The shape of the drop 2 at the first boundary surface to the lens carrier 3 is determined by the lens carrier 3.

In particular, a flat lens carrier 3 can be used, so that the first boundary surface is flat. Accordingly, the optical lens 1 produced in this way will be a plano-convex lens 1 .

However, it may also be provided that the lens carrier 3 is curved, in particular concave. In this case, the first boundary surface of the drop 2 is convex, which also allows a biconvex lens 1 to be produced.

At the second boundary surface of the drop 2, which faces away from the lens carrier 3 and is only in contact with the surrounding gas, a convex shape results due to the surface tension of the liquid lens material. The shape of the second boundary surface can be influenced by a variety of different factors.

The most important influence here is the contact angle, which can be essentially determined by Young's equation. The contact angle results from the ratio of the individual interfacial energies, namely between the liquid lens material and the surrounding gas, the liquid lens material and lens carrier 3 and lens carrier 3 to the surrounding gas. The surrounding gas can be air, but also a process gas, for example a protective gas. The individual interfacial energies can be influenced by the choice of the materials of the liquid lens material or lens carrier 3 or a coating of the lens carrier 3 as well as other physical parameters such as temperature.

In particular, it may be provided that the contact angle between the liquid lens material and the lens carrier 3 is less than 90° , preferably less than 65°, especially preferably less than 50°.

Furthermore, it may be provided that the contact angle between the liquid lens material and the lens carrier 3 is greater than 5°, preferably greater than 15°, especially preferably greater than 25°.

Without consideration of further interferences, the second boundary surface would be spherical, because the interfacial energy between a liquid and a gas is usually high and the spherical shape minimizes the surface area. However, the effect of gravity causes the second boundary surface to deviate from the spherical shape.

In particular, the method may provide for a predetermined amount of the liquid lens material to be applied to the lens carrier 3 for each drop 2. Here the predetermined quantity can be set in advance.

The specified quantity per drop 2 can be a maximum of 5 μl, in particular a maximum of 3 μl, especially preferably a maximum of 1 μl. At these quantities, very small drops 2 and thus also small optical lenses 2 are formed. It has been shown that with such small quantities, the influence of gravity on the second boundary surface is reduced, whereby the deviation of the lens shape from a spherical lens shape and the resulting imaging errors can also be reduced.

In particular, a diameter of the at least one drop 2 can be a maximum of 2 mm, in particular a maximum of 1 mm, especially preferably a maximum of 750 μm.

It can also be provided that the specified quantity per drop 2 is at least 0.1 μl.

The drop 2 can be applied so that it is in free fall before contact with the lens carrier 3.

Alternatively, the drop 2 can be applied in such a way that it is in contact with both the lens carrier 3 and the application device 6 for a certain time.

The at least one drop 2 can be dripped on in particular.

It may be particularly preferably provided that the application device 6 applies at least one drop 2 to a previously defined area of the lens carrier 3.

It may be particularly preferably provided that the application device 6 has at least one outlet 7 connected to a dispenser. The outlet 7 can have the shape of a needle, in particular, since it allows drops 2 to be applied to the lens carrier 3 in a simple and targeted manner. The application device 6 can also have a dosing device with which the quantity of liquid lens material delivered through outlet 7 can be predetermined.

It may be especially preferably provided that the application device 6 is designed to apply several drops 2 of the liquid lens material simultaneously to the lens carrier 3. In this case, the application device 6 can have several outlets 7 arranged in a row or an array, which simultaneously apply drops 2 to the lens carrier 3. It may also be provided that the device has a moving device which moves the lens carrier 3 relative to the application device 6 after a manufacturing step. This allows a large number of optical lenses 1 to be produced in an automated process.

For the production of optical lens 1, the lens material must be selected with regard to suitable parameters such as viscosity, refractive index and curing behavior.

To form a solid optical lens 1, the drop of liquid lens material is cured on the lens carrier 3. In principle, many physical processes are known with which liquids can be cured.

It may be preferably provided that a photopolymer is used as liquid lens material and that drop 2 of the photopolymer is cured by means of a lamp 4. Accordingly, it may also be provided that the device also has a lamp 4 for curing the liquid lens material. A photopolymer is a polymer that can be cured when irradiated with light from the appropriate electromagnetic spectrum, especially the UV-VIS range. The lamp 4 emits electromagnetic waves in a spectral range in which the photopolymer cures. It may be especially preferably provided that the photopolymer is cured by UV light, and that accordingly lamp 4 is a UV lamp 4. The advantage of this is that the curing of the liquid lens material can be carried out in a targeted manner. This also makes it possible to specify the point in time when curing takes place, for example when the lens shape changes over time.

Alternatively, the lens material can be a polymer which polymerizes by evaporation of a solvent, or a glass which solidifies.

It may be preferably provided that the at least one optical lens 1 is removed from the lens carrier 3 after curing. In particular, a release agent can be applied to the lens carrier 3 in advance so that the optical lens 1 can be removed. The optical lens 1 can then be joined flatly to a flat part of the optical component at the first boundary surface, in particular at the entire first boundary surface.

Alternatively, it can be provided that the optical lens 1 is fixed directly in a materially bonded manner to the lens carrier 3 and then installed in the optical component together with the lens carrier 3. In the optical component, the optical lens 1 is then connected directly to the lens carrier 3 without the need for any further adhesive. In this case may be obtained a semifinished product comprising one optical lens 1 and the relevant portion of carrier 3, which may be then provided with an aperture, in order to obtain an optic suitable to be installed in an eye tracking device.

It can preferably be provided that the camera with the optical component may have only one such optical lens 1. This allows the camera to be designed in a particularly compact manner. In particular, such camera is particularly suitable to be an eye camera of an eye tracking glasses or an eye tracking devices in general, like an eye tracking module. This compatibility arises because of the camera reduced dimensions, its compactness, and because of the knowledge of its own image properties, once detected by the image-capturing optical system 8 provided in the manufacturing method described hereinafter.

Eye-tracking spectacles comprise two eye cameras arranged in a nose frame of the glasses and a field of view camera in the middle of the glasses, showing the front scenery of the user. Pure eye tracking spectacles are provided only with eye cameras and do not comprise any field of view camera.

Are also known eye tracking modules, comprising only eye cameras and not any field of view camera, which shall be integrated in other glasses, like for instance virtual/augmented/mixed reality glasses.

The field of view camera is provided to record a field of view video including individual and successive field of view images. The recordings of the two eye acquisition cameras and the at least one field of view camera can thus be entered in correlation in the field of view video of the respective gaze point. Therefore such eye tracking glasses may be connected to a computer device, even remotely, and display the user ^' s gaze information over his/her field of view on the computer device.

With such eye cameras arranged in a pair of eye tracking glasses or in eye tracking devices in general, appropriate miniaturization is particularly important and requested, especially when said eye cameras are arranged in the nose frame of the eye tracking glasses. Said eye cameras may be of low quality, thus producing a correspondent video image quality.

Preferably, a transparent lens carrier 3 may be used. In addition to the advantage that the lens carrier 3 can later also be installed with the optical lens 1, there are other advantages, for example better illumination during UV curing or the use of an image-capturing optical system 8 directly during production.

The lens carrier 3 can be made of plastic in particular. Alternatively, the lens carrier 3 can be made of glass. Preferably, it can be provided that the lens carrier 3 can be designed as an optical filter, which is only transparent for a given frequency spectrum. This allows the lens 1 to be placed directly on the optical filter of the camera, which further miniaturizes the size of the camera.

One difference between this method and conventional methods using grinding or injection molding is that the lens shape is not directly predefined, ground or imposed, but is determined by the boundary conditions themselves. This also means that the lens shape is limited to those shapes that a liquid drop 2 can assume on its own. Furthermore, small disturbances, for example an asymmetric drop 2 or small changes in the surface energy of the lens carrier 3, can lead to changes in the lens shape, which will result in corresponding imaging errors of the finished optical lens 1.

It is therefore particularly preferably provided that the imaging properties of the lens material in the lens form on the lens carrier 3 are measured by means of an image-capturing optical system 8. The sum total of the imaging properties of the lens material in lens form is called imaging properties. The imaging properties can therefore include the focal length of the optical lens 2 but also imaging errors caused by deviations from rotational symmetry or spherical shape.

In particular, it may be provided with respect to the device that the holder 5 is part of the image-capturing optical system 8 for measuring the imaging properties of the lens material on the lens carrier 3, wherein at least one optical axis of the image-capturing optical system 8 passes through an opening 9 of the holder 5.

In particular, the image-capturing optical system 8 can be designed in such a way that the optical rays of an object, in particular of a test pattern 10, are focused through the lens material in lens form onto an image plane. In particular, an image sensor 11 can be arranged in the image plane, which captures the image of the test pattern. In particular, the image sensor 11 can be connected to an evaluation unit

12. Furthermore, the image sensor 11 can be arranged on a printed circuit board

13. Fig. 1 shows a schematic device.

Furthermore, an aperture 14 can be arranged in the beam path, wherein in particular the opening 9 can form the aperture 14. The acquisition of the imaging properties can be carried out for several purposes.

It can be provided in a particularly preferable manner that the image-capturing optical system 8 is used to measure the imaging properties of the liquid lens material in the lens shape. In this way it can be checked before the lens material is cured whether lens 1 will have the desired imaging properties after curing. It should be taken into account that the refractive index of the lens material can change during curing.

In particular, it may be preferably provided that parameters influencing the lens shape are changed in case of a deviation from the intended imaging properties in order to change the imaging properties in a predefined way. In particular, by changing the temperature of the lens carrier 3, the contact angle and thus the lens shape can be varied. Furthermore, the lens shape can be varied by varying the amount of lens material. This has the advantage that the shape of the lens can be influenced in a targeted manner before the lens solidifies.

It may be further provided that the lens shape of the at least one drop 2 may vary in time after application, and that the image-capturing optical system 8 may determine a point in time for the liquid lens material to cure in a predetermined manner. Here, it may be provided that, for example, if the lens material is sufficiently viscous, drop 2 requires a certain time to assume the final shape, and that the liquid lens material can be specifically solidified even before this time. It may also be provided that the contact angle changes over time due to reactions between the liquid lens material and the lens carrier. As a result of the course of these time-varying states, lens shapes can be achieved which would not be possible in a final state of equilibrium.

It may also be preferably provided that the image-capturing optical system 8 is used to capture the imaging properties of the solid optical lens 1. This allows the imaging properties of optical lens 1 to be recorded during the production process.

Here it may be provided that the imaging properties of the optical lens 1 are compared with target imaging properties, and that the optical lens 1 is discarded if the value falls below a limit value.

It may be particularly provided that the imaging properties of optical lens 1 are stored and, when using optical lens 1 in an image-processing system, correction values are generated based on the imaging properties of optical lens 1. In an image-processing system, it is not the image representation on the image sensor 11 that is important, but rather that the optical parameters of the optics and thus in particular the imaging properties of the optical lens 1 are determined during manufacture and that these imaging properties can then be given to a downstream intelligence for further processing, in particular image processing. Image- processing systems are subject here to special cost pressure, since the image quality is generally not evaluated by humans and then the quality of the optics is adapted to the application.

In particular, the imaging properties of essentially every manufactured optical lens 1 may be recorded after curing and stored for the respective lens 1. The imaging properties can be calculated by means of the image of the test image at the image sensor 3 of the image capturing optical system 8. When using lens 1, correction values can be determined for this lens 1 on the basis of the stored imaging characteristics. These correction values are stored in the memory of a computer which evaluates images from the camera in which lens 1 is installed. This computer may, for example, be part of eye tracking glasses or may be connected to eye tracking glasses. With the help of the correction values, the imaging errors of lens 1 can then be taken into account when the computer evaluates the images of the camera, thus compensating the imaging errors in the manufacturing process.

The following are principles for the understanding and interpretation of the present disclosure.

Features are usually introduced with an indefinite article "a, an". Therefore, unless the context indicates otherwise, "a, an" is not to be understood as a numeral word.

The connective word "or" is to be interpreted as inclusive and not exclusive. Unless the context indicates otherwise, "A or B" also includes "A and B", wherein "A" and "B" represent arbitrary features.

By means of an ordering numerical word, for example "first", "second" or "third", a feature X or an object Y in particular is distinguished in several embodiments, unless this is otherwise defined by the disclosure of the invention. In particular, a feature X or an object Y with an ordering numerical word in a claim does not mean that an embodiment of the invention falling under this claim must have a further feature X or a further object Y.

An "essentially" in conjunction with a numerical value includes a tolerance of ± 10% around the specified numerical value, unless the context indicates otherwise.

For ranges of values, the endpoints are included, if not shown differently in the context.