WO2025248123A1

WO2025248123A1 - Optical component and optical assembly

Info

Publication number: WO2025248123A1
Application number: PCT/EP2025/065058
Authority: WO
Inventors: Manuel Aschwanden; David Andreas NIEDERER; Luca Lucera
Original assignee: Optotune Switzerland AG
Current assignee: Optotune Switzerland AG
Priority date: 2024-05-30
Filing date: 2025-05-30
Publication date: 2025-12-04
Anticipated expiration: 2026-11-30

Abstract

Optical component (1), comprising at least two optical elements (2, 3), which each are at least partially transparent and are arranged along an optical axis (4), wherein the two optical elements (2, 3) and/or a connecting element (10), which is arranged between the two optical elements (2, 3) at least partially define two surfaces (5, 6), which are separated by a contact line (11) and wherein the two surfaces (5, 6) at least partly enclose an intermittent space, which is filled with two non-mixable liquids (7, 8) such that one of the two surfaces (5) is in contact with one of the two liquids (7) and the respective other of the two surfaces (6) is in contact with the respective other of the two liquids (8), wherein the two surfaces (5, 6) have different wetting properties in relation to the liquids (7, 8) in contact with them.

Description

Title

Optical component and optical assembly

Description

The invention relates to an optical component according to claim 1.

Optical components of the type mentioned above can be used to influence incident light beams. This may be necessary to compensate for the optical properties of another optical element, which may be a liquid lens.

Such a liquid lens can have at least one deformable membrane that delimits a volume filled with an optical liquid. As a result of gravity or other external acceleration, the liquid can be distributed unevenly perpendicular to an optical axis, resulting in a sag of the liquid lens. This leads to a distortion of the optical properties of the liquid lens.

To correct aberrations, a so-called sag compensation may be applied. Sag compensation allows the liquid lens to maintain or enhance its optical quality, particularly in the face of changes in the orientation, in the acceleration, in particular gravity, in ambient temperature, pressure, or other environmental conditions that can affect the properties of the liquid. This is particularly important for applications such as adaptive optics, imaging, and augmented reality, where precise optical performance is critical.

A sag compensation can involve adjusting the curvature of the membrane to achieve the desired optical performance of the liquid lens. This may be achieved by applying an electrical voltage, magnetic field, or pressure on the liquid lens. However, a drawback of the possible options for sag compensation is that additional components are usually required to influence the distribution of the liquid or the shape of the membrane in the desired manner.

It is an objective of the invention to suggest an optical component by means of which the optical path of a light beam can be influenced in the desired manner without having to actively deform an optically effective surface. The objective is solved by means of an optical component according to claim 1. Preferred embodiments are subject matters of dependent claims.

According to the invention, the optical component comprises at least two optical elements, which are at least partially transparent and are arranged along an optical axis. The two optical elements and/or a connecting element, which is arranged between the optical elements, at least partially define two surfaces, which are separated by a contact line that runs circumferentially about the optical axis. The two surfaces at least partly enclose an intermittent space, which is filled with two non-mixable liquids such that one of the two surfaces is in contact with one of the two liquids and the respective other of the two surfaces is in contact with the respective other of the two liquids. The two surfaces have different wetting properties in relation to the liquids in contact with them.

The invention is based on the realisation that the properties of two optical elements, in particular their respective surfaces, and the two liquids located between them can be selected such that the distribution of the two liquids is influenced. I n particular, at least one of the optical liquids may be distributed such that it is possible to refract and/or bend an incident light beam relative to the optical axis. This enables a compensation of abberations caused by other optical components, in particular liquid lenses, which are arragend along the optical axis. I n particular, the desired liquid distribution is achieved solely under the influence of an external acceleration, for example an earth's gravitational force. Advantageously, no active adjustment of an optically effective component is required.

Preferably, the contact line runs directly between the two optical elements or is at least partially defined by the connecting element, which is arranged between the two optical elements.

A particular finding, on which the invention is based, is that the sag of a liquid lens does not need to be compensated completely. This is due to the circumstance that the sag is caused by an external acceleration, which causes a focal power of the liquid lens that does not need to be compensated.

In particular, the choice of surface properties of the surfaces alone, depending on different wetting properties in relation to the liquids in contact with them , can compensate for a part of the acceleration-dependent sag. Preferably, the optical component is suitable to compensate at least 10 percent, preferably 50 percent, highly preferred 90 percent of the acceleration-based sag of the optical component.

A connecting element may be arranged between the two optical elements such that the contact line is at least partly defined by the connecting element. According to such an embodiment, the two surfaces are not only defined by the two optical elements but also by the connecting element. It is possible that one of the two surfaces extends over one of the optical elements and a part of the connecting element. It is also possible that the surfaces are only defined by the connecting element, such that the optical elements do not necessarily have different wetting properties. Alternatively, only the optical elements may define the surfaces, which have different wetting properties.

In general, the invention is not limited to a certain position or course of the contact line or how it is defined. It is only relevant that the intermittent space and the liquids contained in the intermittent space are at least partially in contact with two surfaces with different wettability properties.

The optical elements can be essentially rigid elements that are at least partially transparent, particularly in a wavelength range of visible light. This makes the optical component particularly suitable for use in optical devices that are intended to improve a person's visual ability.

The two optical elements can be arranged in such a way that the optical axis of the optical component runs through their respective transparent areas. It is within the scope of the invention that the surfaces are formed entirely by the optical elements or only partially, so that in particular further elements may define the surfaces and delimit the intermittent space.

It is relevant that the surfaces of the two optical elements delimit a spatial area, at least along the optical axis, in which the two optical liquids are located. The invention is generally not limited to specific properties of the liquids. It is only relevant that they are suitable for use in an optical component and that the two optical liquids are non-mixable with each other. For example, one of the two optical liquids is water or oil. This can be achieved by placing a flexible membrane within the intermittent space. I n particular, the membrane is also transparent in the area of the optical axis and in particular ensures that the optical fluids are spatially separated within the intermittent space. I n terms of manufacturing costs, the use of a membrane is a simple way of separating the two liquids spatially from one another, in particular without having to ensure that the liquids are soluble in one another.

It is also possible that the optical fluids within the intermittent space are in direct contact with each other. I n this case, the chemical properties of the liquids can be selected in such a way that they do not merge or are soluble in one another. This has particular advantages for the manufacture of the optical component, as no additional component in the form of a membrane has to be provided to separate the two liquids from each other. Furthermore, investigations by the applicant have shown that conventional membranes may not be completely impermeable to the liquids to be separated or even chemically react with one of the liquids to be separated. I n particular the intermittent space is hermetically sealed.

As mentioned above, it is relevant for the invention that the two surfaces have different wetting properties in relation to the liquids in contact with them . This is based on the realisation that a desired liquid distribution within the intermittent space can be favoured by wetting the surfaces differently with the liquids contained therein. I n particular, under the influence of an external acceleration, especially gravitational acceleration, an uneven distribution of the liquids within the intermittent space can be set, preferably with respect to the optical axis.

This allows a boundary region to form in a contact area between the liquids, the shape of which is suitable for influencing an incident light beam in a desired manner. It is an important finding that the wettability properties of the surfaces with respect to the liquids have an effect on the geometrical shape of the boundary region, which is relevant for the optical properties of the optical component.

By arranging the optical component according to the invention next to a liquid lens along the optical axis, it is possible in particular to compensate for acceleration dependent portion of the sag of a liquid lens. The boundary region may comprise the membrane as mentioned above or a direct contact between the two optical liquids.

Different wetting properties may be defined in terms of a contact angle between one of the surfaces and the liquid, which is in contact with it. A surface that is well wettable with respect to the liquid that is in contact with it may have a low contact angle. I n comparison, another surface that is poorly wettable with respect to the other liquid that is in contact with it may have a high contact angle.

The contact angle may be considered a reference value that cannot be determined directly using the optical component according to the invention, but preferably under laboratory conditions. Preferably, a first surface or an area of the first surface with the higher contact angle is in contact with a first of the two liquids, which has the higher surface tension and a second surface or an area of the second surface with the higher contact angle is in contact with a second of the two liquids, which has the lower surface tension.

For a better clarity the optical elements may be referred to as a first optical element and a second optical element. The first optical element may at least partially define a first surface and the second optical element may at least partially define a second surface. The two liquids may be referred to as a first optical liquid and a second optical liquid. The first surface may be in contact with the first liquid and the second surface may be in contact with the second liquid. The wettability of the first surface with respect to the first liquid may be higher than the wettability of the second surface with respect to the second liquid.

Advantageously, at least one of the surfaces can also have different areas that differ in terms of their wettability with the optical fluid in contact with the respective surface. This allows further influencing of the distribution of the liquids within the intermittent space. I n particular, the first and/or second surface may comprise multiple areas with different wetting properties and/or gradually changing wetting properties with respect to the surface.

It is within the scope of invention that at least one of the optical elements or a surface, which at least is partially defined by the optical element, is treated in order to set a desired wetting property. This may be achieved by a chemical surface treatment, in particular by hydrophobisation, whereby at least one of the surfaces is treated with hydrophobic substances such as silanes or fluorcarbons, and/or by hydrophilization, whereby at least one of the surfaces is treated with hydrophilic substances like polysaccharides or polyethylene glycol.

Additionally or alternatively, setting of a desired wettability may be achieved by physical surface modification, in particular by etching, wherein a microscopic structure is defined on a surface and/or by coating, wherein a thin layer of another material, for example a polymer, is applied to a surface.

Additionally or alternatively a surface may be plasma treated.

It is possible that the surface is defined by the optical element itself or by an optical layer, which is connected to the respective optical element. I n particular at least one of the optical elements may have an optical power. Also, it is within the scope of the invention that there are further optical elements arranged within the intermittent space or on a surface of one of the optical elements facing away from the intermittent space.

I n a preferred embodiment, the two optical liquids differ in densities, preferably by more than 0.01 g/ccm , more preferably 0.05 g/ccm, and/or differ in refractive indexes and/or differ in surface tensions, preferably by at least 10 mN/m , preferably 20 m N/m, more preferably by 30 m N/m , most preferably by 50 m N/m . Preferably, the above mentioned properties refer to room temperature, preferably 20°C.

The aforementioned properties have proven to be particularly advantageous with respect to the necessary optical properties for a sag compensation and the benefits achievable with the invention. By setting the above named differences in densities, refractive indexes and surface tensions, a desired distribution of the two optical liquids in the intermittent space, particularly in relation to each other and perpendicular to the optical axis can be adjusted. This makes it possible to influence the shape of the boundary region where the two liquids are adjacent to each other, both separated by a membrane and in direct contact to each other, allowing the optical path of an incoming light beam to be influenced as desired. I n a preferred embodiment, the optical liquids each have a viscosity below 10 Pa*s, preferably below 1 Pa*s, highly preferred below 0.10 Pa*s, most preferred below 0.05 Pa*s. This favours the desired distribution of the two optical liquids with respect to the optical axis without the necessity of an actuation element and in particular as a function of an external acceleration. Preferably, the above mentioned properties refer to room temperature, preferably 20°C.

Preferably, one of the two optical liquids is of hydrophobic nature and/or wherein the respective other optical liquid is of hydrophilic nature. Additionally or alternatively, one of the two optical liquids is of oleophobic nature and/or wherein the respective other optical liquid is of oleophilic nature. Preferably, one of the liquids may be water-based or oil-based and be in contact with a hydrophilic or respectively oleophilic surface in order to achive a good wettability and a small contact angle. Preferably, one of the liquids may be water-based or oil-based and be in contact with a hydrophobic or oleophiobic surface in order to achive a poor wettability and a high contact angle.

As described above, the two surfaces border each other along the contact line. This line runs around the optical axis and defines a boundary region in which the liquids are located within the intermittent space. By setting a specific course for the contact line, the distribution of the liquids within the intermittent space can thus be influenced, thereby affecting the optical properties of the optical component as well. I n particular, the course of the contact line is independent of an external acceleration but can be set with a defined course.

It is possible that the contact line runs in a plane that is essentially perpendicular to the optical axis. I n the plane, the course of the contact line can depend on the geometric shape of the optical elements. If, for example, the optical elements are configured as cylindrical lenses, they can be connected to each other at the edges, so that the contact line in the plane is essentially circular. However, the contact line may have a shape with a varying radius within the plane. The optical elements can be connected to each other by means of a circumferential element, which defines a part of one or both surfaces and may at least partly define the contact line. It is also possible that the contact line has a course which, in relation to a plane orthogonal to the optical axis, is at least partially curved. This is possible, for example, if the optical elements are curved, at least on the surfaces facing each other. I n this case, the surfaces can be directly connected to each other to define the contact line, or by means of a connecting element, whose geometry can essentially determine the course of the contact line. Preferably, the two optical elements each have a calotte shape.

According to a preferred embodiment of the present invention the optical component comprises an optical aperture.

I n a preferred embodiment, the optical aperture has a non-round projection when viewed along the optical axis, i.e. , an outer contour in a plane perpendicular to the optical axis, said outer contour delimiting the optical aperture and being non-round.

Furthermore, in a preferred embodiment, the non-round projection of the optical aperture has one of: zero symmetry planes, one symmetry plane, two symmetry planes, more than two symmetry planes. Particularly, each of the symmetry planes can be parallel to the optical axis.

According to yet another preferred embodiment, at least one of the optical elements comprises a refractive optical power.

Furthermore, according to a preferred embodiment, the two liquids are arranged in the intermittent space and configured to be passively redistributed relative to one another under the influence of an external acceleration, thereby compensating for aberrations of an external lens, particularly a liquid lens.

Within the scope of the invention, the optical component can be used in a headworn device. This can be a pair of glasses, especially a virtual reality headset or an augmented reality headset.

Possible embodiments and advantages of the invention are described in the Figures.

Figure 1 shows a first embodiment of an optical element according to the invention; Figure 2 shows a second embodiment of an optical element according to the invention;

Figure 3 shows an assembly of the first embodiment of the optical element and a liquid lens

The "sag" of fluid lenses refers to the deformation or curvature of the liquid surface within the lens. This deformation is a crucial aspect of the lens's functionality, as it affects the lens's optical power. The term "sag" originates from the shape that the liquid's surface takes on when it is subject to gravitational forces or other acceleration.

The sag of a fluid lens is essential for its optical performance. By precisely controlling the sag, the lens can achieve desired optical properties, such as variable focal lengths, aberration correction, or adaptive optics. This flexibility makes fluid lenses valuable in applications where rapid and precise adjustments to the optical system are required, such as in imaging systems, barcode scanners, or virtual reality devices.

I n a fluid lens, the curvature of the liquid surface can be controlled by various means, such as applying an electric field, a magnetic field, or changing the pressure within the lens. By altering the curvature of the liquid surface, the focal length of the lens can be adjusted, allowing for dynamic focusing capabilities. However, it is a disadvantage, that control means are necessary to control the sag.

Below, optical components are described, with which sag compensation is possible in a simple manner, particularly without active adjustment of an optically effective component.

Figure 1 shows a first embodiment of such an optical component 1 . The optical component 1 comprises two optical elements 2, 3. According to this embodiment, the optical elements 2,3 are made of glass and are essentially flat. However, in an alternative embodiment, the optical elements 2, 3 may be curved. For sake of better understanding, optical element 2 is referred to as the first optical element 2 and optical element 3 is referred to as the second optical element 3.

The first optical element 2 and the second optical element 3 are arranged along an optical axis 4 and each are transparent with respect to wavelength range of visible light, such that the optical component 1 is well suited for an application in a headworn device, for example virtual reality glasses.

The first optical element 2 defined a part of a first surface 5 and the second optical element 6 defined a part of a second surface 6. The surfaces 5, 6 are facing each other at least along the optical axis 4 and delimit an intermittent space, which is filled with a first optical liquid 7 and a second optical liquid 8.

The first optical surface 5 is in contact with the first optical liquid 7 and the second optical surface 6 is in contact with the second optical liquid 8. It is relevant that the first optical liquid 7 and the second optical liquid 8 are immiscible. According to the embodiment shown in Figure 1 , the liquids are separated along a common region 9, which may be defined by a membrane. Alternatively, the liquids 7, 8 may be chosen depending on their chemical properties such that no membrane is required and wherein the liquids 7, 8 are in direct contact with each other.

According to the embodiment shown in Figure 1 , the two optical liquids 7,8 differ in densities by more than 0.01 g/ccm . Furthermore, they differ in refractive indexes and surface tensions by more than 10 mN/m. The optical fluids 7, 8 each have a viscosity below 10 Pa*s.

The first optical element 2 and the second optical element 3 are connected in a circumferential region by means of a connecting element 10, which has a ring shape. It is thinkable that the circumferential region is circular or noncircular.

I n the embodiment shown here, the first and second surfaces 5, 6 are not only formed by the first and second optical elements 2, 3, respectively, but also by the connecting element 10, at which the two surfaces adjoin each other along a common contact line 11 , which runs about the optical axis 4 and, in the embodiment shown here, essentially corresponds to the geometry of the connecting element 10. I n other words, the contact line 11 runs in a plane, which is perpendicular to the optical axis 4.

As indicated by Figure 1 , the common boundary region 9 between the first liquid 7 and the second liquid 8 has a shape such that it is possible to bend a light beam incident along the optical axis 4, thereby compensating for the acceleration dependent sag portion of a liquid lens, which can also be arranged along the optical axis 4. To adjust the desired distribution of the liquids within the intermittent space, through which this is possible, the first and second surfaces 5, 6 have different wetting properties with respect to the first and second liquids 7, 8 respectively, with which they are each in contact. As a result, it is especially possible to adjust surface tensions of the liquids 7, 8 that induce the desired shape of the boundary region 9.

For example, one of the surfaces 5 or 6 may be treated by means of plasma treatment in order to achieve the desired wettability properties. Alternatively or additionally, the surfaces 5 or 6 may be treated chemically or physically.

Figure 2 shows another embodiment of an optical component 1 , which has a similar structure like the optical component shown in Figure 1 . For the sake of better understanding, identical reference numerals are used for identical elements.

In contrast to the embodiment shown in Figure 1 , the optical elements 2, 3 shown in Figure 2 each have a calotte geometry. The optical elements 2, 3 are also connected via an intermediate element, along which the contact line 10 runs. I n contrast to Figure 1 , the contact line does not exclusively run in a plane oriented orthogonal to the optical axis but is curved in such a way that the course of the contact line extends out of this plane.

I nstead of the embodiment shown here, the optical elements 2, 3 could also be curved in such a way that they are directly connected to each other in a circumferential edge area. This makes it possible to dispense with the connecting element 10. In principle, the geometries of the optical elements 2, 3 can be chosen arbitrarily, allowing the compensation component shown here to adapt to any lens structure. I n particular, the course of the contact line 11 can also be chosen arbitrarily and depending on the geometry of the optical elements 2, 3 in order to adjust the desired distribution of the liquids within the intermittent space. It is thinkable that an eye or a sensor is located within a recess of the curved contact line 11 or faces such a recess. This is preferred, if the optical component 1 is used in a headworn device.

Furthermore, the explanations regarding Figure 1 apply accordingly. Figure 3 shows an assembly of an optical component 1 and a liquid lens 12. According to the embodiment shown in Figure 3, the optical component 1 is identical to the optical component 1 as shown in Figure 1 , however it may also be identical to the optical component 1 as shown in Figure 2 or have another structure and design as described above.

In the assembly according to Figure 3, the tunable lens 12 has a deformable membrane 13, which together with the optical element 3 encloses a space filled with an optical fluid 14. The filled space is sealed at the periphery with a ring element 15, which is connected to the connecting element 11 . A lens shaping element 16 is in contact with the membrane on a side facing away from the fluid 14. By moving the lens shaping element 16, the shape of the membrane 13 can be influenced.

As indicated in Figure 3, the fluid 14 is distributed unevenly perpendicular to the optical axis due to an external acceleration, resulting in the sag described earlier. This leads to imaging errors, preferably an accelerationdependent portion of the sag, which, however, can be corrected with the optical component 1. I n particular, the different wetting properties on the surfaces 5, 6 allow for adjusting a distribution of the fluids 7, 8, which has a compensating effect for the lens 12.

It is advantageous if the fluids 7, 8, and 14 are subjected to the same acceleration, which ensures that the distributions of the fluids 7, 8, and 14 perpendicular to the optical axis are always adjusted in the correct ratio to each other and depending on the acceleration, for example, due to the gravitational field of the Earth or as a result of movement of the assembly shown in Figure 3.

Furthermore, the optical component can comprises an optical aperture 100 that can have a non-round projection when viewed along the optical axis 4. Particularly, said projection of the optical aperture can have one of: zero symmetry planes, one symmetry plane, two symmetry planes, more than two symmetry planes. Particularly, each of the symmetry planes can be parallel to the optical axis.

Furthermore, each of the optical elements 2, 3 can comprises a refractive optical power.

Claims

1. Optical component (1 ), comprising at least two optical elements (2, 3), which each are at least partially transparent and are arranged along an optical axis (4) , wherein the two optical elements (2, 3) and/or a connecting element (10), which is arranged between the two optical elements (2, 3) at least partially define two surfaces (5, 6), which are separated by a contact line (11 ) and wherein the two surfaces (5, 6) at least partly enclose an intermittent space, which is filled with two non-mixable liquids (7, 8) such that one of the two surfaces (5) is in contact with one of the two liquids (7) and the respective other of the two surfaces (6) is in contact with the respective other of the two liquids (8) wherein the two surfaces (5, 6) have different wetting properties in relation to the liquids (7, 8) in contact with them.

2. Optical component (1 ) according to claim 1 , wherein the two optical liquids (7, 8) differ in density, preferably by more than 0.01 g/ccm , more preferably 0.05 g/ccm , and/or differ in refractive index and/or differ in surface tension, preferably by at least 10 m N/m , preferably 20 mN/m, more preferably by 30 mN/m , most preferably by 50 m N/m .

3. Optical component (1 ) according to claim 1 or 2, wherein the optical liquids (7, 8) each have a viscosity below 10 Pa*s, preferably below 1 Pa*s, highly preferred below 0.10 Pa*s, most preferred below 0.05 Pa*s.

4. Optical component (1 ) according to at least one of the preceding claims, wherein the first and second liquid (7, 8) are separated by means of a membrane.

5. Optical component (1 ) according to at least one of the claims 1 to 3, wherein the first and second liquid are in direct contact with each other.

6. Optical component (1 ) according to at least one of the preceding claims, wherein one of the two optical liquids (7) is of hydrophobic nature and/or wherein the respective other optical liquid (8) is of hydrophilic nature.

7. Optical component (1 ) according to at least one of the preceding claims, wherein one of the two optical liquids (7) is of oleophobic nature and/or wherein the respective other optical liquid (8) is of oleophilic nature.

8. Optical component (1 ) according to at least one of the preceding claims, wherein the contact line (11 ) runs in a plane perpendicular to the optical axis (4).

9. Optical component (1 ) according to at least one of the preceding claims, whereby the contact line (11 ) has a course, which in relation to a plane perpendicular to the optical axis (4), is at least partially curved.

10. Optical component (1 ) according to one of the preceding claims, wherein the two optical elements (2, 3) are in direct contact with each other at least along the contact line (11 ) .

11 . Optical component (1 ) according to one of the preceding claims, wherein the optical elements (2, 3) are connected by means of the connecting element (10) , which runs circumferentially about the optical axis (4) , wherein the contact line (11 ) is arranged on the connecting element (10) , preferably wherein the shape of the contact line (11 ) at least partially corresponds to a geometry of the connecting element (10).

12. Optical component (1 ) according to one of the claims 1 to 11 , wherein the two optical elements (2, 3) each have a calotte shape.

13. Optical component according to one of the preceding claims, wherein the optical component (1 ) comprises an optical aperture (100) .

14. Optical component according to claim 13, wherein the optical aperture (100) has a non-round projection when viewed along the optical axis (4).

15. Optical component according to claim 14, wherein the non-round projection of the optical aperture (100) has one of: zero symmetry planes, one symmetry plane, two symmetry planes, more than two symmetry planes.

16. Optical component according to claim 15, wherein each of the symmetry planes is parallel to the optical axis (4) .

17. Optical component according to one of the preceding claims, wherein at least one of the optical elements (2, 3) comprises a refractive optical power.

18. Optical component according to one of the preceding claims, wherein the two liquids (7, 8) are arranged in the intermittent space and configured to be passively redistributed relative to one another under the influence of an external acceleration, thereby compensating for aberrations of an external lens, particularly a liquid lens.

19. Headworn device, in particular glasses or virtual reality glasses or augmented reality glasses, comprising an optical component according to claims 1 to 18.