Optical component and optical system

Abstract

Tunable optical lens (1) comprising two optical elements (2, 3), which are arranged along an optical axis (4) and enclose an intermittent space, a flexible membrane (5), which is arranged between the two optical elements (2, 3) along the optical axis (4) and which divides the intermittent space in two volumes (6, 7), each of which are filled with an optical liquid (8, 9), at least one flexible member (10, 13), which limits the two volumes (6, 7) at least in a radial direction with respect to the optical axis and which at least partially holds the flexible membrane (5). It is essential that a reservoir space (11) is arranged on a side of the flexible member (10, 13) facing away from the two volumes (6, 7) and which is at least partially limited by the flexible member (10, 13), wherein the reservoir space (11) is sealed with respect to an environment of the tunable optical lens (1).

Description

[0001] Title

[0002] Optical component and optical system

[0003] Description

[0004] The present invention relates to a tunable optical lens and an optical system.

[0005] Tunable optical lenses of the type mentioned above allow for dynamic adjustment of focal length and other optical properties. These tunable lenses often employ liquidic systems, where the shape of a flexible membrane can be altered in order to achieve the above named effects.

[0006] Tunable optical lenses are for example known from EP14793794 and each may comprise two optical elements, which are arranged along an optical axis and enclose an intermittent space. The flexible membrane, as mentioned above, is arranged between the two optical elements along the optical axis and divides the intermittent space in two volumes, each of which are filled with an optical liquid. At least one flexible member limits the two volumes at least in a radial direction with respect to the optical axis and at least partially holds the flexible membrane. A compartment may be arranged on a side of the flexible member facing away from the two volumes, which may carry further components of the tunable optical lens.

[0007] A challenge of previously known tunable optical lenses is related to the use of optical liquids that typically are in contact with the flexible member. Due to the material properties of the flexible member or environmental influences at least one of the optical liquids may diffuse through the flexible member. As a result, the optical properties of the tunable lens may change in an undesirable way due to the volatilization of one of the optical liqiuds. The diffusing liquid may further negatively influence the functionality of components, which may be arranged in the compartment, which is adjacent to the flexible member.

[0008] It is an objective of the invention to propose a tunable optical lens whose adjustable optical properties do not significanly change over the entire operating time of the tunable optical lens. This objective also arises with regard to an optical system in which the tunable optical lens can be used. The objective is solved by a tunable optical lens according to claim 1 and an optical system according to claim 15. Preferred embodiments of the invention are subject matters of dependent claims.

[0009] According to the invention, the tunable optical lens comprises two optical elements, which are arranged along an optical axis and enclose an intermittent space. A flexible membrane is arranged between the two optical elements along the optical axis and divides the intermittent space in two volumes, each of which are filled with an optical liquid. At least one flexible member limits at least one of the two volumes at least in a radial direction with respect to the optical axis and at least partially holds the flexible membrane.

[0010] It is essential for the invention, that a reservoir space is arranged on a side of the flexible member facing away from the two volumes, which is at least partially limited by the flexible member. The reservoir space is sealed with respect to an environment of the tunable optical lens.

[0011] The invention is based on the realization that the volatilization of at least one of the optical liquids from one of the two volumes mainly depends on a concentration gradient of said optical liquid between the volume in question and a space adjacent thereto. With previously known tunable optical lenses, this results in the diffused liquid entering a neighbouring comparment and escaping from it into the environment. This maintains the concentration gradient in relation to one of the optical liquids in the relevant volume with respect to the compartment, so that diffusion continues uninterrupted. This leads to a corresponding deterioration of the optical properties of the tunable lens over its operating time.

[0012] By providing a reservoir space instead of a compartment, the leaking optical liquid can remain in the optical tunable lens, so that a desired concentration gradient and in particular a concentration equilibrium can be set, which counteracts further diffusion of at least one of the optical liquids.

[0013] It is also possible to provide a saturation liquid in the reservoir space during assembly of the optical tunable lens, the properties of which may be selected in such a way that it counteracts a diffusion of at least one of the two optical liquids through the flexible member. I n a simple embodiment, the optical elements are transparent elements that can be made of glass or plastic and can have an essentially flat design. It is also possible that the optical elements have an optical power and are curved on at least one surface.

[0014] I n particular, the optical elements each have two oppositely facing surfaces. The surfaces of the two optical elements preferably delimit the intermittent space between the optical elements and are each adjacent to one of the optical liquids. I n other words, a surface of a first optical element may limit a first one of the volumes and be in contact with a first optical liquid therein and a surface of a second optical element may limit a second one of the volumes and be in contact with a second optical liquid therein.

[0015] The invention is not limited to a specific type of optical liquid. It is possible that at least one of the optical liquids comprises water, oil, glycerol, ethanol, ethylene or methanol . It is preferred that the two optical liquids have essentially identical densities.

[0016] The flexible membrane is preferably transparent, at least portionwise, and is aligned with a transparent area along the optical axis. The flexible membrane limits both of the two volumes at least along the optical axis. The optical properties of the tunable lens depend on the shape of the flexible membrane.

[0017] The flexible member is preferably used to hold the flexible membrane and to limit the two volumes in which the optical liquids are contained. The deformability of the flexible member can ensure that the membrane is also kept movable, particularly in an edge area, so that its shape can be changed as required and with minor restrictions in order to be able to adapt the optical properties of the tunable optical lens.

[0018] The invention is not limited to how the reservoir space is designed and what measures are taken to hermetically seal it with respect to its environment. However, it is relevant that the reservoir space is directly or indirectly adjacent to the flexible member in order to be able to communicate with one of the volumes in such a way that a concentration ratio between one of the optical liquids and the liquid contained in the reservoir has an effect on diffusion.

[0019] I n a preferred embodiment, the flexible member has a material-inherent permeability for at least one component of at least one of the optical liquids and the reservoir space is at least partly filled with a saturation liquid in order to establish a concentration ratio between at least one of the volumes and the reservoir space with respect to the component of the optical liquids for which the flexible member is permeable.

[0020] According to the embodiment described above, a saturation liquid may be added to the reservoir space during assembly of the tunable optical lens in order to counteract diffusion of at least one of the optical liquids or a component comprised therein through the flexible member. Compared to an unfilled reservoir space, it is therefore not necessary for one of the optical liquids to first diffuse through the flexible member in order to be able to counteract subsequent, further diffusion.

[0021] The preferred embodiment is not limited to a specific nature or properties of the saturation liquid or the quantity in which it is present in the reservoir space. However, it is advantageous that the saturation liquid is selected in such a way that at least one of the optical liquids or a component comprised therein has a limited solubility in the saturation liquid and preferably that the saturation liquid is at least approximately saturated with the corresponding or liquid or the component comprised therein when the reservoir space is filled or prevents said liquid or the component comprised therein from dissolving in the saturation liquid.

[0022] I n a preferred embodiment, the flexible member is a bellows, in particular an elastomer bellows, which extends between the two optical elements within the intermittent space.

[0023] The use of a bellows, which can be made of an elastomer, has proven to be advantageous in order to achieve the required adjustability of the flexible membrane and at the same time has properties with regard to its material permeability, which can be easily compensated by the use of a reservoir space or a saturation liquid.

[0024] In a preferred embodiment, the reservoir space is at least partially limited by a housing which extends circumferentially about the optical axis.

[0025] The housing may be made of plastic or other material and may define at least a portion of an outer shell of the tunable optical lens. The housing enables the tunable lens to be sealed off from its surroundings in a structurally simple manner. I n particular, this is possible by means of a sealing coating on the inside and / or outside of the housing or, for example, by using sealing elements, which can be arranged between different portions of the housing. I n a preferred embodiment, the flexible member is a first flexible member. The tunable optical lens also comprises a second flexible member, wherein the first flexible member limits the two volumes in the radial direction. The second flexible member is arranged on a side of the first flexible member facing away from the two volumes such that the reservoir space is at least partially enclosed between the first flexible member and the second flexible member.

[0026] The use of two flexible elements is advantageous, as the reservoir space can be divided into several areas by them, making it possible, for example, to fill it only partially with a saturation liquid, to collect a diffusing liquid and to arrange other components separately from it, which should only come into contact with one of the liquids to a limited extent.

[0027] I n particular, one advantage of using at least two flexible elements may be that a diffusing liquid has to overcome at least two diffusion barriers. This counteracts an undesired diffusion of at least one of the liquids, which leads to improved optical properties over the service life of the tunable optical component.

[0028] The first and second flexible members can each be bellows, which each extend around the optical axis of the tunable component and in particular are arranged essentially concentrically to one another in relation to the optical axis. It is possible that the flexible membrane is only held by the first flexible member, which delimits the two volumes. It is also possible that the flexible membrane is held by the first member and by the second member and, in particular extends at least partially in a radial direction through the first member.

[0029] In a preferred embodiment, a first portion of the reservoir space is enclosed between the first flexible member and the second flexible member and is at least partially filled with the saturation liquid and wherein a second portion of the reservoir space is enclosed between the second flexible member and the housing.

[0030] According to the further development described above, a first part of the reservoir space is enclosed between the two flexible members and can be separated from the two volumes by the first flexible member. It is possible to fill this first portion partially or completely with the saturation liquid and thus counteract diffusion of one of the optical liquids in the manner described above. A second part can be separated from the first part by the second flexible member and at least partially be limited by the housing. This makes it possible to arrange further technical components within the reservoir space.

[0031] I n a preferred embodiment, an actuator is arranged on a side of the flexible member facing away from the two volumes and is mechanically coupled to the flexible membrane, in particular by means of a shaping element, which extends radially through the flexible member.

[0032] According to the embodiment described above, the actuator is used to change the shape of the membrane. The advantageous further development is not limited to how or according to which principle the actuator is designed. It is possible that the actuator is of an electromechanical type or, for example, comprises a memory shape alloy which can be deformed depending on its temperature in order to be able to influence the shape of the membrane.

[0033] I n a preferred embodiment, the actuator is arranged in the reservoir space and is at least partially immersed by the saturation liquid.

[0034] The preferred embodiment described above is based on the realization that the actuator can come into contact with the saturation liquid. It is therefore not necessary to shield it completely from the saturation liquid. This is particularly possible for actuators that are inert in terms of their adjustability, however can exert large adjustment forces, so that it is not a disadvantage if the adjustment has to be carried out against a flow resistance caused by the saturation liquid.

[0035] For other types of actuators, it is advantageous if they do not come into excessive contact with the saturation liquid. This is the case, for example, if the actuator has frictional components whose abrasion could get into the liquid in an undesirable way. Hence, in another preferred embodiment, the actuator is arranged in the second portion of the reservoir space, which in particular is essentially free of the saturation liquid.

[0036] As described above, only the first portion of the reservoir space can be filled with a saturation liquid, so that the second portion adjacent to it does not need to be filled with the saturation liquid in order to achieve the advantages of the invention. Preferably, the reservoir space is completely filled with the saturation liquid. Alternatively, the reservoir space is partly filled with the saturation liquid and is partly filled with a gas, which is saturated with the saturation liquid.

[0037] Preferably, the saturation liquid comprises at least one component, which is essentially identical to the component in at least one of the optical liquids for which the flexible member is permeable.

[0038] The further development described above is based on the realization that the saturation liquid does not have to differ in its properties from one of the optical liquids responsible for the optical properties of the optical component. Rather, by using the saturation liquid in the reservoir space, which is identical to one of the liquids whose diffusion is to be prevented, the desired concentration balance can be generated in a simple manner. Further advantages arise when assembling the optical tunable lens, as the number of different liquids that should not mix is reduced, thereby optimizing the handling effort.

[0039] As described above, the objective is also solved by an optical system. The optical system comprises a tunable optical lens according to the invention or a preferred embodiment thereof and an image sensor or an image projector, which are arranged along an optical path with the tunable optical lens.

[0040] An optical system according to the invention can be designed as a headworn device, for example virtual reality glasses, which can comprise an image projector. With the tunable optical lens, it is possible to take into account different visual abilities of the wearer of such virtual reality glasses, so that in particular it is not necessary to wear another visual aid, such as glasses, which offers advantages in terms of comfort. It is also thinkable that the optical system is part of a cell phone in which an image sensor is used to take pictures. The use of the tunable optical lens makes it possible to change the focus of an image or, for example, to compensate for unwanted movements of the cell phone. The optical path may at least partially extend along the optical axis of the tunable optical lens.

[0041] Advantages and possible embodiments of the invention are explained below with reference to examples of embodiments and the figures.

[0042] Figure 1 shows a first embodiment of a tunable optical lens; Figure 2 shows a second embodiment of a tunable optical lens;

[0043] Figure 3 shows a third embodiment of a tunable optical lens.

[0044] Figure 1 illustrates a first embodiment of a tunable optical lens 1 . The lens comprises two optical elements 2 and 3, which are arranged along an optical axis 4 and enclose an intermittent space. Positioned between the two optical elements 2 and 3 along the optical axis 4 is a flexible membrane 5. This membrane divides the intermittent space into two volumes, 6 and 7, each of which is filled with an optical liquid, 8 and 9 respectively.

[0045] A flexible member 10 is positioned to limit the two volumes 6 and 7 in a radial direction with respect to the optical axis 4. This flexible member 10 also partially holds the flexible membrane 5. On the side of the flexible member 10 facing away from the two volumes 6 and 7, a reservoir space 11 is arranged. This reservoir space 11 is at least partially limited by the flexible member 10.

[0046] The flexible member 10 has a material-inherent permeability for at least one of the optical liquids 8 or 9 or a component comprised therein. The reservoir space 11 is sealed with respect to the environment of the tunable optical lens 1. The reservoir space 11 is filled with a saturation liquid 12, which is chosen to establish a concentration balance between at least one of the volumes 6 or 7 and the reservoir space 11 with respect to the optical liquid 8 or 9 for which the flexible member 10 is permeable.

[0047] Additionally, the flexible member 10 is depicted as a bellows, specifically an elastomer bellows, which extends between the two optical elements 2 and 3 within the intermittent space. The reservoir space 11 is at least partially limited by a housing 3, which extends circumferentially about the optical axis 4.

[0048] An actuator 16 is arranged on the side of the flexible member 10 facing away from the membrane 5. This actuator 16 is mechanically coupled to the flexible membrane 5 to adjust an optical property of the tunable optical lens 1. The actuator 16 includes a shaping element 17, which extends radially through the flexible member 10 and is connected to the membrane 5.

[0049] I n this embodiment, the actuator 16 is arranged in the reservoir space 11 and is completely immersed in the saturation liquid 12. The saturation liquid 12 is essentially identical to the optical liquid 8 for which the flexible member 10 is permeable according to this embodiment.

[0050] The tunable optical lens 1 shown in Figure 1 has well adjustable optical properties over the entire operating time of the tunable optical lens due to the structure described above. This is due to the fact that the reservoir space is used to hold the saturation liquid, which makes it possible to counteract diffusion of at least one of the optical liquids through the flexible member 10.

[0051] Figure 2 illustrates a second embodiment of a tunable optical lens 1. The lens comprises two optical elements 2 and 3, which are aligned along an optical axis 4. These optical elements enclose an intermittent space that is divided into two volumes 6 and 7 by a flexible membrane 5. Each volume is filled with an optical liquid, denoted as 8 and 9 respectively.

[0052] Similarly to the first embodiment as described above, the flexible membrane 5 is positioned between the two optical elements 2 and 3 along the optical axis 4. The membrane 5 divides the intermittent space into two distinct volumes 6 and 7. These volumes are filled with optical liquids 8 and 9, which are essential for the tunable functionality of the lens.

[0053] A flexible member 10 is situated radially with respect to the optical axis 4 and serves to limit the two volumes 6 and 7. This flexible member 10 also partially holds the flexible membrane 5 in place. On the side of the flexible member 10 facing away from the two volumes 6 and 7, a reservoir space 11 is arranged. This reservoir space 11 is at least partially limited by the flexible member 10 and is hermetically sealed from the external environment.

[0054] An actuator 16 is positioned on the side of the flexible member 10 and 13 facing away from the membrane 5. This actuator 16 is mechanically coupled to the flexible membrane 5 through a shaping element 17, which extends radially through the flexible member 10 and 13. The actuator 16 is designed to adjust an optical property of the tunable optical lens 1 . I n this embodiment, the actuator 16 is arranged within the reservoir space 11 and may at least be partially immersed in the saturation liquid 12.

[0055] In contrast to the first embodiment of the tunable lens, which is shown in Figure 1 , the reservoir space 11 is only partly filled with the saturation liquid 12, which may be held by a container or an absorbent material (not shown here) . Another part of the reservoir space 11 is however filled with a gas, which is saturated with the saturation liquid 12. This also makes it possible, as described above, to counteract duffusion of at least one of the optical liquids or a component comprised therein, especially if the saturated liquid 12 comprises a componentwhich is essentially identical to the liquid in question whose diffusion is to be prevented or a component comprised therein.

[0056] Figure 3 illustrates an embodiment of a tunable optical lens 1 . Similarly to the embodiments shown in Figures 1 and 3, the lens comprises two optical elements 2 and 3, which are arranged along an optical axis 4. These optical elements enclose an intermittent space that is divided into two volumes 6 and 7 by a flexible membrane 5. Each volume is filled with an optical liquid, denoted as 8 and 9 respectively.

[0057] A first flexible member 10 is positioned to limit the two volumes 6 and 7 in a radial direction with respect to the optical axis 4. This flexible member 10 also partially holds the flexible membrane 5. A reservoir space 11 is arranged on the side of the flexible member 10 that faces away from the two volumes 6 and 7. This reservoir space 11 is at least partially limited by the flexible member 10.

[0058] The first flexible member 10 exhibits a material-inherent permeability for at least one of the optical liquids 8 or 9 or a component comprised therein. The reservoir space 11 is sealed from the external environment of the tunable optical lens 1 . The reservoir space 11 is filled with a saturation liquid 12 to establish a concentration ratio between at least one of the volumes 6 or 7 and the reservoir space 11 with respect to the optical liquid 8 or 9 for which the flexible member 10 is permeable or a component comprised therein.

[0059] Additionally, the tunable optical lens 1 comprises a second flexible member 13. The second flexible member 13 is arranged on the side of the first flexible member 10 facing away from the two volumes 6 and 7. Consequently, the reservoir space 11 is divided into a first portion 14 and a second portion 15. The first portion 14 is enclosed between the first flexible member 10 and the second flexible member 13 and is at least partially filled with the saturation liquid 12. The second portion 15 is enclosed between the second flexible member 13 and the housing 3.

[0060] The first portion 14 of the reservoir space 11 is filled with the saturation liquid 12, whereas the second portion 15 is not filled with the saturation liquid 12, however comprises an actuator 16. The actuator 16 is arranged on the side of the flexible member 10 and 13 facing away from the membrane 5. This actuator 16 is mechanically coupled to the flexible membrane 5 by means of a shaping element 17, which extends radially through the flexible members 10 and 13.

[0061] In contrast to the two embodiments shown in Figures 1 and 2, the third embodiment shown in Figure 3 makes it possible to use actuators that are not intended to come into contact with liquids and still achieve a low volatilization of optical liquids. This makes it possible to maintain the optical properties of the tunable lens 1 over its entire service life.

Claims

Claims1. Tunable optical lens (1 ) comprising- two optical elements (2, 3), which are arranged along an optical axis (4) and enclose an intermittent space;- a flexible membrane (5) , which is arranged between the two optical elements (2, 3) along the optical axis (4) and which divides the intermittent space in two volumes (6, 7) , each of which are filled with an optical liquid (8, 9);- at least one flexible member (10, 13), which limits at least one of two volumes (6, 7) at least in a radial direction with respect to the optical axis and which at least partially holds the flexible membrane (5); characterized in that a reservoir space (11 ) is arranged on a side of the flexible member (10, 13) facing away from the two volumes (6, 7) and is at least partially limited by the flexible member (10, 13) and that the reservoir space (11 ) is sealed with respect to an environment of the tunable optical lens (1 ) .

2. Tunable optical lens (1 ) according to claim 1 , wherein the reservoir space (11 ) comprises a liquid.

3. Tunable optical lens (1 ) according to claim 2, wherein the liquid comprised by the reservoir space is a saturation liquid (12) filling the reservoir space (11 ) .

4. Tunable optical lens (1 ) according to claim 3, wherein the flexible member (10, 13) has a material-inherent permeability for at least one component comprised in at least one of the optical liquids (8, 9) and the reservoir space is filled with the saturation liquid (12) in order to establish a concentration ratio between at least one of the volumes (6, 7) and the reservoir space (11 ) with respect to the component of the optical liquid (8, 9) for which the flexible member (10, 13) is permeable.

5. Tunable optical lens (1 ) according to at least one of the preceding claims, wherein the flexible member (10, 13) is a bellows, in particular an elastomer bellows, which extends between the two optical elements (2, 3) within the intermittent space.

6. Tunable optical lens (1 ) according to at least one of the preceding claims, wherein the reservoir space (11 ) is at least partially limited by a housing (3) which extends circumferentially about the optical axis (4).

7. Tunable optical lens (1 ) according to at least one of the preceding claims, wherein the flexible member (10) is a first flexible member (10) and wherein the tunable optical lens (1 ) comprises a second flexible member (13), wherein the first flexible member (10) limits the two volumes (6, 7) in the radial direction and the second flexible member (13) is arranged on a side of the first flexible member (10) facing away from the two volumes (6, 7) such that the reservoir space (11 ) is at least partially enclosed between the first flexible member (10) and the second flexible member (13) .

8. Tunable optical lens (1 ) at least according to claims 4, 6 and 7, wherein a first portion (14) of the reservoir space (11 ) is enclosed between the first flexible member (10) and the second flexible member (13) and is at least partially filled with the saturation liquid (12) and wherein a second portion (15) of the reservoir space (11 ) is enclosed between the second flexible member (13) and the housing (3).

9. Tunable optical lens (1 ) according to at least one of the preceding claims, comprising an actuator (16), which is arranged on a side of the flexible member (10, 13) facing away from the two volumes (6, 7) and which is mechanically coupledto the flexible membrane (5) by means of a shaping element (17), which extends radially through the flexible member (10, 13) .

10. Tunable optical lens (1 ) at least according to claims 3 and 9, wherein the actuator (16) is arranged in the reservoir space (11 ) and is at least partially immersed by the saturation liquid (12) .11 . Tunable optical lens (1 ) at least according to claims 8 and 9, wherein the actuator (16) is arranged in the second portion (15) of the reservoir space (11 ) .

12. Tunable optical lens (1 ) at least according to claim 4, wherein the saturation liquid (12) comprises at least one component, which is essentially identical to the component in at least one of the optical liquids (8, 9) for which the flexible member (10, 13) is permeable.

13. Tunable optical lens (1 ) at least according to claim 3, wherein the reservoir space (11 ) is completely filled with the saturation liquid (12).

14. Tunable optical lens (1 ) according to at least one of the claims 3 to 12, wherein the reservoir space (11 ) is partly filled with the saturation liquid (12) and is partly filled with a gas, which is saturated with the saturation liquid (12).

15. Optical system comprising a tunable optical lens (1 ) according to one of the preceding claims and an image sensor or an image projector, which are arranged along an optical path with the tunable optical lens (1 ) .

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