An adjustable non-circular acceleration compensated liquid lens

Abstract

The invention relates to a membrane based fluidic lens (1,1') with a non-circular membrane (3,3') and a non-circular aperture, a partially flexible lens shaper (2, 2') for adjusting a focal length of the lens (1,1'), an actuation assembly to adjust the focal length and a means to inherently adjust for acceleration-induced aberrations.

Description

[0001] An adjustable non-circular acceleration compensated liquid lens

[0002] Specification

[0003] The invention relates to an adjustable liquid lens with the features according to claim 1 and 15.

[0004] In the art liquid lenses are known, most liquid lenses with an adjustable membrane suffer from several drawbacks.

[0005] A first drawback is that optical degradation of the lens due to acceleration forces such as gravity that lead to an unwanted deformation of the membrane and thus introduce optical aberrations.

[0006] A second drawback is that membrane-based fluid lenses is that the lens design needs to completely circular for existing lens shaper geometries. In many applications, the aperture of the lens, however, is noncircular and in particular, non- symmetric. In order to adjust the focal length or to correct for cylinder- or other aberrations the actuation and in particular the lens shaping of the membrane becomes more elaborate.

[0007] At least these two problems have motivated the inventors to improve on existing liquid lens designs in order to overcome these problems.

[0008] The object is achieved by the lens having the features of claim 1 or 15.

[0009] Advantageous embodiments are described in the dependent claims.

[0010] According to a first aspect of the invention, an adjustable, liquid lens comprises the following components:

[0011] - an at least partially flexible lens shaper having a lens shaper contour enclosing a lens shaper aperture,

[0012] - a first membrane and a second membrane, wherein the first membrane is circumferentially attached to the lens shaper or the second membrane, such that a first boundary contour is formed where the first membrane is attached to the lens shaper or the second membrane respectively, - an optical element an optical element forming a transparent portion around the optical axis of the liquid lens,

[0013] - wherein the second membrane with a first side and a second side facing in the opposite direction than the first side, wherein the second membrane is circumferentially attached to an attachment component selected from the group consisting of: a) the optical element, b) the lens shaper, c) the first membrane, particularly in case the first membrane is attached to the lens shaper, such that a second boundary contour is formed where the second membrane is attached to the attachment component,

[0014] - a first liquid enclosed in a first volume between the first membrane and the second membrane, particularly the first side of the second membrane,

[0015] - a second liquid enclosed in a second volume between the optical element and the second membrane, in particular the second side of the second membrane,

[0016] - an actuator assembly comprising at least one actuator, wherein the actuator assembly is configured to adjust the liquid lens in a plurality of actuation states, and such that in one or more actuation states of said plurality of actuation states the lens shaper contour lies partially outside of a plane, particularly, a single plane associated to the lens shaper aperture, wherein o the first boundary contour is non-circular, or o the second boundary contour is non-circular, wherein the first liquid comprises a first mass density and a first refractive index, wherein the second liquid comprises a second mass density and a second refractive index, o wherein the first mass density is greater than the second mass density and wherein the first refractive index is smaller than the second refractive index, or o wherein the first mass density is smaller than the second mass density and wherein the first refractive index is greater than the second refractive index. The liquid lens is in particular adjustable in terms of sphere and / or cylinder.

[0017] The term “lens shaper” in the context of the current specification particularly refers to a component or a portion of a component that is configured to limit an area of the membrane attached to the lens shaper, wherein within that area the membrane may be adjustable in curvature.

[0018] The lens shaper may be embodied in form of a rim portion of the component that circumferentially limits the area of the membrane.

[0019] The lens shaper may also be embodied as an annular component that is removably attached to the lens and particularly such that the lens shaper is movable with respect to a bottom portion of the lens or a liquid volume of the lens.

[0020] The lens shaper is partially flexible which in the context of the specification may be interpreted that along the lens shaper aperture at least some portions of the lens shaper are movable, wherein a direction of motion of these portions may be limited to motions along the optical axis of the lens.

[0021] Such a lens shaper allows to locally adjust the first boundary contour of the first membrane with regard to a position along the optical axis.

[0022] In case also the second membrane is attached to the lens shaper, the lens shaper allows further, to locally adjust second boundary contour of the second membrane with regard to a position along the optical axis.

[0023] This feature allows for adjusting focal length, sphere and cylinder for noncircular membrane geometries of liquid lenses.

[0024] In contrast, with a stiff lens shaper this would not be possible.

[0025] The flexible lens shaper may also be formed from a flexible annular structure that is bent to different positions along the optical axis.

[0026] In particular, the first boundary contour may be understood a closed line at which the first membrane is attached to the lens shaper or the second membrane respectively, wherein said line encloses an area of the first membrane in which the first membrane is deformable and in which the optical axis is comprised. Thus the first boundary contour encloses the optical axis. Said line may extend along a rim portion of the first membrane or the second line respectively.

[0027] Similarly, the second boundary contour may be understood as a closed line at which the second membrane is attached to the attachment component. The second boundary contour encloses the optical axis.

[0028] In certain embodiments, it might be advantageous to provide a spacer component or another component between the lens shaper and the first membrane. In the context of the current specification this component is then to be interpreted as being part of the lens shaper.

[0029] The same notion holds true with regard to the attachment component to which the second membrane is attached. Also, here it might be advantageous or necessary to provide an additional component between said attachment component and the second membrane. The notion of this specification, this additional component is then considered to be comprised by the attachment component.

[0030] In some embodiments the membrane, the first or the second membrane, may be attached to the lens shaper or the attachment component respectively by means of glue or bonding or clamping.

[0031] The first membrane in particular covers the lens shaper aperture and is attached along the lens shaper aperture to the lens shaper.

[0032] The optical element may be a massive transparent or at least portion via transparent element that comprises an aperture through which light can propagate.

[0033] This optical element may be arranged at on a side of the adjustable liquid lens through which light enter or leaves the liquid lens, wherein said side is particularly located opposite a side that comprises the lens shaper aperture.

[0034] The optical elements may be formed and arranged in the lens such as to limit liquid volume on one side along the optical axis of the liquid lens.

[0035] The optical element may have an optical power or may be solely formed as a window plate.

[0036] In certain embodiments the optical element serves as the attachment component.

[0037] This to be understood that on a side of the optical element that faces toward the lens shaper said optical element comprises a rim portion along which second membrane is attached to the optical element. In particular in between the second membrane and the side of the optical element that faces toward the lens shaper the second liquid might be arranged. For this purpose, the rim portion of the optical element might be formed as so circumferential lateral wall.

[0038] Said rim portion might be formed by a separate element that is comprised by the optical element or the optical element might be formed integrally, i.e. in one piece to comprise said rim portion.

[0039] An actuation state in the context of the current specification is a state that is adopted by the lens, in response to a mechanical movement of the actuator assembly. In particularly each actuation state is associated to a change in pressure in the first and or the second volume, which in turn, adjusts a shape and / or a curvature of the first and or the second membrane.

[0040] The partially flexible lens shaper allows for the actuator assembly to adjust the lens shaper in a fashion that in one or more actuation states the lens shaper contour cannot be comprised by a single plane. This means that the lens shaper may be actuated such that along the lens shaper aperture the lens shaper adopts different positions along the optical axis wherein there is no single plane that comprises all positions along the lens shaper aperture.

[0041] The specific feature of the liquid lens allows to have non-circular geometries of the first boundary contour and the second boundary contour.

[0042] In particular, the notion of a non-circular geometry of the first boundary contour relates to actuation states of the liquid lens in which the first boundary contour is comprised in a single plane. This plane might be tilted with respect to the optical axis.

[0043] In particular, the notion of a non-circular geometry of the second boundary contour may relate to actuation states of the liquid lens in which the second boundary contour is comprised in a single plane, e.g. when the attachment component corresponds to the lens shaper or the first membrane. This plane might be tilted with respect to the optical axis.

[0044] Alternatively, or additionally, the term “non-circular” in the context of the first and / or the second boundary contour may be understood as the shape of the respective boundary contour, when the boundary contour is projected on a plane, in particular projected on a plane orthogonal to the optical axis.

[0045] The term “non-circular” in the context of a two-dimensional manifold that is embedded in a three-dimensional space, might require appropriate projection to a two-dimensional space. This projection is not meant to transform a circular boundary contour in a non-circular boundary contour.

[0046] In particular, the boundary contour may be regarded as non-circular if there is no projection in a single plane in which the boundary contour appears circular.

[0047] Alternatively, or additionally, the term “non-circular” in the context of the first and / or the second boundary contour may be understood as the shape of the respective boundary contour, when first and / or the second membrane are disassembled, no pre-tension is applied to the membrane and the membrane is essentially laid out on a flat surface. If the respective boundary contour adopts a non-circular geometry, the respective boundary contour is considered to be non-circular. This definition may be particularly useful, in case the lens does not comprise actuation state, that allow to adjust the first or the second boundary contour in a single plane.

[0048] Particularly, the first boundary contour comprises at least two extension directions in said plane, that differ in length by at least 3% and at most by 400%.

[0049] Particularly, the second boundary contour comprises at least two extension directions in said plane, that differ in length by at least 3% and at most by 400%.

[0050] The first mass density may be a factor 1.03 to 4 times greater than the second mass density and the first refractive index may be a factor 1.03 to 2 times smaller than the second refractive index, or

[0051] The first mass density may be a factor 1.03 to 4 times smaller than the second mass density, and the first refractive index may be a factor 1.03 to 2 times greater than the second refractive index.

[0052] The differences in mass density and refractive index of the first and the second liquid allow for compensating acceleration induced aberrations, such as gravity-induced aberrations of the liquid lens. Specific selection of the density and refractive index combinations may be done in accordance with the membrane properties such as the membrane stiffness.

[0053] In particular, the second volume may be completely closed, wherein the second membrane has no means of active actuation but may only respond to a pressure change in the first volume.

[0054] According to another embodiment of the invention, the second volume may be limited exclusively by rigid, fixed, i.e. non-movable element(s) and the second membrane, wherein the second membrane is attached exclusively to rigid and fixed element(s) of the lens.

[0055] The lens according to the first aspect of the invention allows for aberration-corrected imaging and non-circular membrane geometries.

[0056] According to another embodiment of the invention, the actuator assembly is configured to deform and in particular not only move the lens shaper or a part of the lens shaper in a direction of the optical axis of the liquid lens such that the lens shaper contour lies partially outside of a single plane associated to the lens shaper aperture.

[0057] This embodiment specifies the advantages of an at least partially flexible lens shaper that allows actuation along the optical axis, in which the lens shaper contour is not comprised in a single plane.

[0058] According to another embodiment of the invention, a portion in which the lens shaper is flexible comprises more than 2.5% of a circumference of the lens shaper contour, preferably more than 50% of the circumference of the lens shaper contour, and most preferably more than 97.5%of the circumference of the lens shaper contour.

[0059] This embodiment provides for a lens shaper that provides sufficient flexibility to adjust the liquid lens.

[0060] The term “circumference” may be understood as a size measure of the lens shaper around its aperture.

[0061] This embodiment particularly allows for a lens shaper that may be formed partially by a wall portion of the liquid lens (i.e. a non-flexible portion) and partially by a flexible element (i.e. the flexible portion of the lens shaper. According to another embodiment of the invention, the actuator assembly is configured to adjust a liquid pressure in the first or in the second liquid, such as to deform, e.g. to adjust a curvature of the first membrane and / or the second membrane within the first boundary contour or the second boundary contour.

[0062] In particular, the curvature of the first and / or the second membrane may deform in response to an adjusted liquid pressure, that in turn causes the lens shaper to adjust its lens shaper contour.

[0063] This embodiment may be particularly advantageous, when the actuation assembly is arranged such that it is not directly moving the lens shaper, but configured to adjust the liquid pressure in the lens, e.g. by means of a movable piston that is not the lens shaper, causing the flexible portion(s) of the lens shaper to adjust their position in response to the adjusted liquid pressure.

[0064] According to another embodiment of the invention, the first boundary contour in particular a projection therefrom onto a plane orthogonal the optical axis encloses a first area, i.e. a first aperture, and the second boundary contour in particular a projection therefrom onto a plane orthogonal the optical axis encloses a second area, i.e. a second aperture, wherein the first area is more than 5%, more than 10%, or more than 20% greater than the second area, particularly wherein the first area is more than 80% greater than the second area.

[0065] According to another embodiment of the invention, the first area is less than 200%, particularly less than 100% greater than the second area.

[0066] The enclosed area corresponds in particular to the area within which a curvature of the membrane is adjustable.

[0067] This embodiment allows for an aperture of the first membrane that is greater than an aperture of the second membrane.

[0068] According to another embodiment of the invention, the first boundary contour encloses a first area and the second boundary contour encloses a second area, wherein the second area is more than 5%, more than 10%, or more than 20% greater than the first area, particularly wherein the second area is more than 80% greater than the first area. According to another embodiment of the invention, the second area is less than 200%, particularly less than 100% greater than the first area.

[0069] According to another embodiment of the invention, a reference contour corresponds to the second boundary contour isotropically scaled with a factor, wherein the first boundary contour extends not further away from the reference contour than 20%, in particular not further away from the reference contour than 10%, 5%, or 2% of a greatest extension direction of the reference contour.

[0070] This embodiment in essence allows for identical or almost identical scaled boundary contours, wherein a deviation of an isotropically scaled boundary contour is provided as well for reference.

[0071] The reference contour may be an imaginary contour. Having the boundary contours scaled in essence isotropically allows for a compact design of the aperture portion of the lens.

[0072] According to another embodiment of the invention, the first boundary contour encloses a first aperture and wherein the second boundary contour encloses a second aperture, wherein the first and the second aperture each limit an aperture angle with respect to a center of an image plane of the lens, wherein the first and the second aperture are selected such that the aperture angle is identical within the tolerances, in particular the tolerances mentioned in the previous embodiment for the first and the second aperture, particularly within a cross-section of the liquid lens through the optical center.

[0073] This embodiment provides a lens geometry in which all apertures are adjusted to each other, such that aperture dimensions are not unnecessary big and thus require excess built-space.

[0074] This embodiment allows for the most compact design of the lens.

[0075] According to another embodiment of the invention, the lens shaper is attached to an elastically deformable circumferential wall of the liquid lens, wherein upon actuation, the wall is compressed or extended along the optical axis.

[0076] This embodiment allows for a particularly large stroke of the lens. The elastically deformable wall portion may also be considered to be part of the lens shaper.

[0077] The deformable wall portion may limit a liquid volume of the lens, in which the first or the second liquid is comprised.

[0078] The wall may comprise a u-shaped cross-section or a zig-zagging cross-section, such that the wall may be deformed in a bellows-like fashion. The elastically deformable wall may also compensate for thermal expansion of the liquids.

[0079] According to another embodiment of the invention, the optical element comprises a first and a second portion, wherein the second portion forms a circumferential recess in the direction to the first membrane or the second membrane with regard to the first portion around a center, in particular the center, where the optical axis intersects the optical element, of the optical element, wherein the elastically deformable wall is attached to the recess.

[0080] According to this embodiment, the second portion extends around the first portion of the optical element, and may provide a circumferential step around the first portion, wherein the elastically deformable wall may be arranged on the second portion such that the elastically deformable wall extends along the step.

[0081] This embodiment allows for a very compact lens design, as the volume comprising the first and the second liquid may be kept as little as possible, while maintaining a full stroke capability of the lens.

[0082] According to another embodiment of the invention, a boundary between the first portion and the second portion of the optical element encloses an aperture angle of the optical element with respect to a center of the image plane of the lens, wherein the aperture angle of the optical element is equal or greater than the smaller of the aperture angles of the first and the second aperture.

[0083] This embodiment features apertures that are adjusted such that a minimal built space can be obtained.

[0084] In the following, advantageous embodiments of the first and second portion of the optical element are disclosed.

[0085] According to another embodiment of the invention, a width of the circumferential recess is adjusted such that at full stroke of the lens shaper, a gap between the compressed wall and the first portion is maintained, i.e. the elastically deformable wall does not touch the first portion even when fully compressed.

[0086] According to another embodiment of the invention, a depth of the recess relative to the first portion is smaller, in particular at least 5 %, 10 % or 20 % smaller, than a full stroke of the lens shaper contour.

[0087] The term “depth” in relation to the recess is to be understood as an extend along the optical axis, with regard to a height (also measured along the optical axis) of the first portion relative to the second portion. According to another embodiment of the invention, the elastically deformable wall has a U-shaped cross-section along a plane comprising the optical axis, wherein an opening of the “u” of the U-shaped cross-section points away from the optical axis.

[0088] According to another embodiment of the invention, the first boundary contour and / or the second boundary contour, in particular, when project on a plane orthogonally to the optical axis or when actuated such that the first and or second boundary contour are comprised by a plane, is symmetrical with respect to exactly one axis orthogonal to the optical axis or with respect to exactly one axis in the plane comprising the first and / the second boundary contour respectively.

[0089] This embodiment limits the first and the secondary boundary contour to shapes that are in essence geometries that deviate from a circular symmetry, which features an abundance of symmetry axes. Similarly, the first and / or the boundary contour are limited to geometries that deviate from an elliptic or oval geometry, as these geometries feature two axes of symmetry (the principal axes).

[0090] According to another embodiment of the invention, the optical element comprises a concave surface such that it forms a lens element.

[0091] This embodiment allows for a compact built space of the liquid lens. As it reduces a distance to an image plane of the liquid lens.

[0092] According to another embodiment of the invention, the first membrane has a first membrane stiffness and the second membrane has a second membrane stiffness, wherein a ratio between the first membrane stiffness and the second membrane stiffness is between 1 and 4 or between 1 and 3.

[0093] This allows using membranes having a thickness (and thus an elasticity) that may be actuated with low forces of actuation.

[0094] According to another embodiment of the invention, the at least two extension directions of the first boundary contour differ in length between 5% and 170%, and / or wherein the at least two extension directions of the second boundary contour differ in length between 5% and 170%.

[0095] These embodiments in turn disclose for example an elliptical or an oval geometry of the first and / or the second boundary contour within limits of the principal axes.

[0096] According to another embodiment of the invention, the at least two extension directions of the first boundary contour differ in length between 10% and 50%, and / or wherein the at least two extension directions of the second boundary contour differ in length between 10% and 50%. This embodiment discloses a slightly elliptical membrane geometry. According to another embodiment of the invention, the first membrane, the second membrane, as well as the first and the second liquid are selected such that the first membrane deforms under acceleration forces, such as gravity, at least partially in an opposite direction along an optical axis of the lens than the second membrane, membrane.

[0097] Further, according to another embodiment, a stiffness Si of the first membrane and a stiffness S2 of the second membrane is given by

[0098] Si _ n2-ni P- -P2s2n2~ 1 P2 particularly when the first aperture portion and the second aperture portion have the same size, particularly the same radii or when the lens is configured to project or receive essentially collimated light, particularly wherein the first mass density pi is larger than the second mass density p2 and first refractive index m is smaller than the second refractive index n2.

[0099] According to another embodiment of the invention, the second liquid is comprised in a volume between the first portion of the optical element and the second membrane, wherein the second membrane is circumferentially attached to a boundary region extending along a boundary between the first and the second portion.

[0100] According to another embodiment of the invention, the first volume that is formed between the first and the second membrane, wherein the elastically deformable wall limits the first volume as well.

[0101] According to another embodiment of the invention, the first volume comprising the first liquid comprises a first and second subvolume forming the first volume, wherein the first subvolume extends in a region defined by the first portion of the optical element between the second membrane and the first membrane, wherein the second subvolume extends between the first membrane, and the second portion of the optical element, such that the first volume extends radially beyond the second volume.

[0102] Thus, the first volume is arranged “on top” of the second volume and extends radially beyond the second volume as well.

[0103] The first and the second subvolumes are imaginary subvolumes that may not be limited by a hardware feature. This embodiment allows for a liquid lens in which the second volume is comprised from all sides except on by the first volume, such that a very compact built of the lens is achieved.

[0104] According to another embodiment of the invention, the first membrane is attached to a first side of the lens shaper facing away from the optical element, wherein the second membrane is attached to a second side of the lens shaper facing toward to optical element.

[0105] Thus, the first volume is comprised between the first and the second membrane, and laterally, i.e. radially limited by the lens shaper.

[0106] According to another embodiment of the invention, the first membrane is attached to a first side of the lens shaper facing away from the optical element, wherein the second membrane is attached to the first membrane on a side of the first membrane facing toward the optical element.

[0107] According to a second aspect of the invention, an adjustable fluid, in particular a liquid lens has an optical axis and comprises at least the following components:

[0108] - a lens shaper, particularly wherein the lens shape is flexible,

[0109] - a first membrane attached to the lens shaper, such that a first boundary contour is formed where the first membrane is attached to the lens shaper,

[0110] - a rigid optical element arranged on the optical axis,

[0111] - an actuator assembly comprising at least one actuator, wherein the actuator assembly is configured to adjust the liquid lens in a plurality of actuation states exhibiting an adjusted curvature of the first membrane, wherein the first boundary contour is non-circular,

[0112] - wherein the rigid optical element comprises a first sub-aperture section configured to confer a first focal power to the optical element and a second sub-aperture section configured to confer a second focal power to the optical element, wherein the first and the second sub-aperture sections are arranged on opposite sides of a design plane extending parallel to or on the optical axis of the lens, wherein a difference between the first focal power and the second focal power is at least 0.1 diopters, wherein the first and the second subaperture sections are designed to compensate an acceleration-induced , in particular a local, focal power variation of the lens. The lens according to the second aspect of the invention allows for compensating for example gravity-induced aberrations when the lens is oriented essentially along a design direction relative to gravity or the acceleration force in question.

[0113] For example, if the lens is designed to be oriented at a 90° angle with respect to gravity, the design plane may be located on the optical axis of the lens and orthogonal to gravity.

[0114] Particularly, the design plane is an imaginary plane that defines the two sub-aperture sections.

[0115] Thus, the lens may be designed specifically for an orientation with respect to the accelerating force, such that when lens is oriented according to 'said design orientation, any gravity or acceleration-induced effect on the first membrane may be compensated by the shape of the optical element in particular by the optical properties of the first and the second sub-aperture section.

[0116] Focal length may be adjusted by the first membrane, while any acceleration induced aberrations may be avoided.

[0117] According to another embodiment of the invention, an aperture of the optical element consists of the first and the second sub-aperture sections.

[0118] According to another embodiment of the invention, the first sub-aperture section comprises less than 5%, particularly less than 10%, more particularly less than 25%, even more particularly less than 50% of the aperture of the optical element.

[0119] The percentage refers in particular to an area of the aperture of the optical element.

[0120] The aperture may comprise an associated aperture diameter that ranges between 2 to 4 mm or between 3 to 5 mm.

[0121] The fluid lens may be adapted to adjust for sphere and / or cylinder.

[0122] Terms, definitions, features, examples and embodiments are applicable from the first aspect to the second aspect in combination or alone and vice versa.

[0123] In particular, the term “non-circular” may be understood in connection with actuation states of the lens in which the first boundary contour is comprised in a plane.

[0124] Alternatively, the term “non-circular” may be understood as a contour that a projection of the first boundary contour adopts when projected in a single plane, particularly on a plane orthogonal to the optical axis.

[0125] According to another embodiment of the invention, the first boundary contour comprises at least two extension directions in said plane, that differ in length at least 3% and at most 400%. The lens shaper may be formed according to an embodiment of the first aspect of the invention. That is, in particular, the lens shaper may be partially flexible so that a lens shaper contour comprising a lens shaper aperture may be adjusted such that the contour is no comprised in any single plane.

[0126] This allows to adjust the lens despite a non-circular first boundary contour for various focal state without introducing aberrations caused by the non-circular first boundary contour.

[0127] According to another embodiment of the invention, the difference between the first focal power and the second focal power is greater than 1 / 8, particularly greater than 0.2 diopter, more particularly greater than 0.25 diopter.

[0128] According to another embodiment of the invention, the difference between the first focal power and the second focal power is smaller than 1 , 2, 5, or 10 diopter.

[0129] According to another embodiment of the invention, the focal power of the lens, in particular an overall focal power of the lens may be adjusted by adjusting a pressure on the membrane exerted from the fluid, such that a curvature of the membrane is adjusted and thus a focal power of the lens. For this purpose, the lens shaper may be formed adjustable, i.e. as disclosed for the lens according to the first aspect. That is, the lens may comprise an actuation assembly configured to adjust a position of the lens shaper along the optical axis of the lens.

[0130] Alternatively, the lens shaper may be fixed with respect to the optical element, and a pressure of the fluid may be adjusted by means of an actuation assembly that adjusts the pressure of the fluid, such that a curvature of the membrane is adjusted in response to the adjusted pressure.

[0131] According to another embodiment of the invention, the acceleration-induced acceleration is a gravity-induced acceleration.

[0132] This embodiment in particular may also refer to the lens according to the first aspect.

[0133] According to another embodiment of the invention, the first sub-aperture section comprises a first curvature of the optical element, and the second sub-aperture section comprises a second curvature of the optical element, to convey the differing first and second focal power.

[0134] The first curvature may be located on a first side of the optical element facing toward the first membrane and / or on a second side of the optical element facing away from the first membrane. The second curvature may be located on a first side of the optical element facing toward the first membrane and / or on a second side of the optical element facing away from the first membrane.

[0135] In particular, the first and the second curvature each comprise a curvature profile extending in the first and the second sub-aperture section respectively.

[0136] According to another embodiment of the invention, the first and the second curvature are located both on the first and / or the second side.

[0137] According to another embodiment of the invention, the optical element comprises a design focal power, wherein the first focal power is greater than the design focal power and wherein the second focal power is smaller than the design focal power - or vice versa.

[0138] The design focal power may positive or negative.

[0139] That is, the design focal power may be regarded as a focal power of the lens, when oriented according to its design orientation and under influence of the acceleration force and when there is no focal power adjusted by a curvature of the first membrane.

[0140] According to another embodiment of the invention, a difference between the first focal power and the second focal power is greater than 0.1 , particularly greater than 1 / 8 diopters, particularly greater than 0.2 diopters, more particularly greater than 0.25 diopters.

[0141] According to another embodiment of the invention, a difference between the overall focal power of the lens and the first focal power and / or the second focal power is greater than 0.05, particularly greater than 1 / 16 diopters.

[0142] In particular, the overall focal power of the lens is the focal power of the assembled lens. Particularly, for focal states of the lens that exhibit the highest degree of membrane curvature.

[0143] According to another embodiment of the invention, the optical element comprises design curvature designed to convey the design focal power to the optical element, wherein the first curvature in the first sub-aperture section is greater than the design curvature and the second curvature in the second sub-aperture section is smaller than the design curvature - or vice versa.

[0144] The design curvature may be comprised on the same or an opposite side of the optical element than the first and the second curvature. For example, the first and the second curvature may be arranged on the first side of the optical element, wherein the design curvature is arranged on the second side of the optical element, i.e. the opposite side.

[0145] According to another embodiment of the invention, the rigid optical element is designed as a refractive element.

[0146] According to another embodiment of the invention, the fluid lens comprises a fluid, such as a first liquid, wherein the rigid optical element is in direct contact with the fluid, which is disposed between the first membrane and the rigid optical element.

[0147] This embodiment allows for a simplified geometry of the lens. The volume in which the fluid is comprised therefore is limited on one side of the lens by the first membrane and on an opposite side by the optical element.

[0148] A lateral wall may be formed by a wall. Said wall may be an elastically deformable wall as laid out in the context of the first aspect of the invention. In particular, the optical element may comprise a first portion and a second portion according to the first aspect. The first and the second sub-aperture section would be arranged and comprised on the first portion of the optical element.

[0149] Embodiments relating to the optical element and in particular to the first and the second portion of the optical element are applicable to the second aspect of the invention, at least in so far as no second membrane is concerned.

[0150] That is, the second portion may be formed as a step or recess circumferentially surrounding the first portion, wherein the wall may be arranged and attached on the second portion of the optical element.

[0151] According to another embodiment of the invention, the lens shaper encloses a lens shaper aperture with a lens shaper contour. That is, the lens shaper encloses an aperture that is limited by an annular lens shaper contour. The lens shaper contour may or may not be comprised in a single plane. This may depend on an actuation state of the lens.

[0152] According to another embodiment of the invention, the actuator assembly is configured to deform the lens shaper or a part of the lens shaper in direction of the optical axis of the lens such that the lens shaper contour lies partially outside of a single plane associated to the lens shaper aperture.

[0153] According to another embodiment of the invention, a portion in which the lens shaper is flexible comprises more than 2.5% of a circumference of the lens shaper contour, preferably more than 50% of the circumference of the lens shaper contour, and most preferably more than 97.5%of the circumference of the lens shaper contour. According to another embodiment of the invention, the actuator assembly is configured to adjust a liquid pressure in the fluid, such as a first liquid, such as to deform the first membrane within the first boundary contour.

[0154] According to another embodiment of the invention, a reference contour corresponds to a boundary contour of the optical element in particular to a first portion of the optical element, wherein said reference contour is isotropically scaled with a factor, wherein the first boundary contour extends not further away from the reference contour than 20% of a greatest extension direction of the reference contour.

[0155] According to another embodiment of the invention, the first boundary contour encloses a first aperture and wherein the boundary contour of the optical element, in particular the boundary contour of the first portion of the optical element encloses a second aperture, wherein the first and the second aperture each limit an aperture angle with respect to a center of an image plane of the lens, wherein the first and the second aperture are selected such that the aperture angle is identical for the first and the second aperture.

[0156] According to another embodiment of the invention, the lens shaper is attached to an elastically deformable circumferential wall of the lens, wherein upon actuation, the wall is compressed or extended along the optical axis.

[0157] According to another embodiment of the invention, the optical element comprises a first and a second portion, wherein the second portion forms a circumferential recess with regard to the first portion around a center of the optical element, wherein the wall is attached to the recess.

[0158] The first and the second section are particularly comprised by the first portion of the optical element.

[0159] According to another embodiment of the invention, a boundary between the first portion and the second portion of the optical element encloses an aperture angle of the optical element with respect to a center of the image plane of the lens, wherein the aperture angle of the optical element is equal or greater than the smaller of the aperture angles of the first aperture.

[0160] According to another embodiment of the invention, a width of the circumferential recess is adjusted such that at full stroke of the lens shaper, a gap between the compressed wall and the first portion is maintained.

[0161] According to another embodiment of the invention, a depth of the recess is smaller than a full stroke of the lens shaper contour. According to another embodiment of the invention, the elastic deformable wall has a U-shaped cross-section along a plane comprising the optical axis, wherein an opening of the “u” of the U-shaped cross-section points away from the optical axis.

[0162] According to another embodiment of the invention, the first boundary contour is symmetrical with respect to exactly one axis.

[0163] According to another embodiment of the invention, the optical element comprises a concave surface such that it forms a lens element.

[0164] This embodiment allows for a compact built space of the liquid lens. As it reduces a distance to an image plane of the liquid lens.

[0165] According to another embodiment of the invention, the at least two extension directions of the first boundary contour differ in length between 5% and 170%.

[0166] This embodiment discloses for example an elliptical or an oval geometry of the first boundary contour within limits of the principal axes.

[0167] According to another embodiment of the invention, the at least two extension directions of the first boundary contour differ in length between 10% and 50%.

[0168] This embodiment discloses a slightly elliptical membrane geometry.

[0169] According to another embodiment of the invention, the first volume comprising the first liquid comprises a first and second subvolume forming the first volume, wherein the first subvolume extends in a region defined by the first portion of the optical element and the first membrane, wherein the second subvolume extends between the first membrane, and the second portion of the optical element, such that the first volume extends radially beyond the second volume.

[0170] Thus, the first volume is arranged “on top” of the first portion and extends radially beyond the first portion of the optical element.

[0171] The first and the second subvolumes are imaginary subvolumes that may not be limited by a hardware feature.

[0172] This embodiment allows for a liquid lens in which the second volume is comprised from all sides except on by the first volume, such that a very compact built of the lens is achieved.

[0173] According to another embodiment of the invention, the first membrane is attached to a first side of the lens shaper facing away from the optical element, or wherein the first membrane is attached to a second side of the lens shaper facing toward to optical element. According to a third aspect of the invention, a design and fabrication method for an rigid optical element configured to compensate an acceleration-induced, in particular a gravity-induced, aberration in a non-circular fluid lens with the rigid optical element, the method comprising the following steps:

[0174] - simulating an acceleration-dependent aberration of the non-circular fluid lens, when the lens is oriented with its optical axis along one or more design directions with respect to a direction of the acceleration,

[0175] - in a computer-implemented modelling step, modelling optical surfaces of the optical element by optimizing, in particular by ray-tracing method, a non- rotational symmetric surface sag component of the optical surfaces, to reduce the acceleration-induced aberration by at least 10%, 20%, 50%, 80, 90% or 95% of the lens, when the lens is oriented along the design direction, and

[0176] - fabricating the optical element according to the results of the modelling step.

[0177] The design of the lens in terms of the first boundary contour may be provided to the method together with a design direction along which the lens is oriented with respect to the acceleration force.

[0178] The design direction may be understood as a design orientation, as the decisive feature is the orientation relative to the acceleration force and not the specific direction.

[0179] According to another embodiment of the invention, the modelling of the optical surfaces comprises modelling a first sub-aperture section configured to confer a first focal power to the optical element and a second sub-aperture section configured to confer a second focal power to the optical element, wherein the first and the second sub-aperture sections are arranged on opposite sides of a design plane extending parallel to or on the optical axis of the lens, wherein a difference between the first focal power and the second focal power is at least 0.1 diopters, wherein the first and the second sub-aperture sections are designed to compensate the acceleration- induced aberration

[0180] According to another embodiment of the invention, the difference between the first focal power and the second focal power is at least 0.125 diopters, particularly at least 0.2 diopters, more particularly at least 0.25 diopters.

[0181] Particularly, the difference between the first focal power and the second focal power is not more than 1 diopters. According to another embodiment of the invention, the simulating step comprises a finite element method by applying a hydrostatic pressure gradient to a first membrane of the liquid lens.

[0182] This allows to determine a physically correct surface deformation of the membrane. The hydrostatic gradient may be determined by the fluid density and the acceleration acting on the fluid.

[0183] According to another embodiment of the invention, the liquid lens is a liquid lens according to the second aspect of the invention.

[0184] According to another embodiment of the invention, the simulating and / or modeling is based on numerical calculations.

[0185] Figures and Examples

[0186] Particularly, exemplary embodiments are described below in conjunction with the Figures. The Figures are appended to the claims and are accompanied by text explaining individual features of the shown embodiments and aspects of the present invention. Each individual feature shown in the Figures and / or mentioned in said text of the Figures may be incorporated (also in an isolated fashion) into a claim relating to the device according to the present invention.

[0187] Fig. 1 shows an embodiment of the liquid lens according to the first aspect of the invention;

[0188] Fig. 2 shows a variation of the embodiment of the liquid lens according to the first aspect of the invention;

[0189] Fig. 3 shows another exemplary embodiment of the liquid lens according to the first aspect of the invention;

[0190] Fig. 4 shows a top view on a lens according to the invention

[0191] Fig. 5 shows an exemplary embedment of similar apertures

[0192] Fig. 6 shows an exemplary embedment of scaling of the apertures.

[0193] Fig. 7 shows another embodiment of the lens according to the invention with a partially flexible lens shaper;

[0194] Fig. 8 shows another embodiment of the lens according to the invention with a partially flexible lens shaper;

[0195] Fig. 9 shows several embodiments of the lens according to the invention; Fig. 10 shows further embodiment of the lens according to the invention;

[0196] Fig. 11 shows an embodiment of the optical element according to a lens of the second aspect of the invention; and

[0197] Fig. 12 shows another embodiment of the lens according to the second aspect of the invention.

[0198] In Fig. 1 an exemplary embodiment of the liquid lens 1 according to the first aspect is shown.

[0199] The liquid lens 1 comprises the following components: a lens shaper 2 on a first side of the lens 1, an optical element 5 on a second side of the lens 1, wherein the second side is located opposite the first side of the lens 1 along an optical axis 100 of the lens 1.

[0200] The lens shaper 2 limits a lens shaper aperture 21 (cf. Fig. 7C) with a lens shaper boundary contour 20. The lens shaper 2 comprises an annular element 2 that is flexibly adjustable along the optical axis 100, such that the lens shaper contour 20 may not be comprised in a single plane. In the state that is shown in Fig. 1 , the lens shaper boundary contour 20 is comprised in a plane extending orthogonal to the optical axis 100.

[0201] The lens shaper 2 comprises a plurality of interface tabs 22 extending essentially radially outwards from an outer contour of the lens shaper 2. The interface tabs 22 are locations at which an actuation assembly (not shown) comprising one or more actuators (not shown) may interface to push and / or pull the lens shaper 2 at the tabs 22. As there a several tabs 22, in this example seven, wherein only six are depicted, it is possible to locally deform the lens shaper 2 along the optical axis 100 and thus to generate a lens shaper contour 20 that varies in height along the optical axis 100, wherein it may be varied such that the interface tabs 22 and thus the lens shaper contour 20 may not be comprised in a single plane. The actuation and shaping of the lens shaper contour 20 may be achieved by actuating each interface tab 22 individually and independently from each other along the optical axis 100 of the lens 2.

[0202] The lens shaper 2 is connected to the optical element 5 by way of an elastically deformable wall 6 that in this example has a u-shaped cross-section, wherein an opening of the “u” faces away from the optical axis 100. The wall 6 may be formed as a bellows. The wall 6 may be compressed by pushing the lens shaper 2 via its tabs 22 toward the optical element 5, causing the u-shaped cross-section to narrow and potentially bend toward the optical axis 100 with a bottom side of the ”U”. Similarly, when the lens shaper 2 is pulled away from the optical element 5, the wall 6 stretches, such that the U-shaped cross-section may widen.

[0203] The lens shaper 2 and / or the wall 6 may comprise additional elements that are used at an interface between the wall 6 and the lens shaper 2, such as an additional annular element, that may be suited to provide a better attachment of the lens shaper

[0204] 2 to the wall 6.

[0205] On a side opposite the lens shaper 2, the wall 6 is attached to the optical element 5 along a circumferential portion 52 of the optical element 5.

[0206] Like the lens shaper 2 and the wall 6, also the optical element 5 may comprise additional elements 7 that are arranged at the interface of the wall 6 and the optical element 5. These elements 7 may serve the purpose of providing a better or more rigid attachment of the wall 6 to the optical element 5.

[0207] The wall 6 may be attached to the lens shaper 2 and / or the optical element 5 for example by means of a glue or a bond or clamping.

[0208] The lens 1 comprises two volumes, a first V1 and a second volume V2 that are separated from each other in a liquid tight fashion. In the first volume V1 a first liquid L1 is comprised, wherein in the second volume V2 a second liquid L2 is comprised.

[0209] The liquids L1, L2 are selected to have specific optical properties at least with regard to their refractive index and the mass density at room temperature or the design temperature in which lens is to operated.

[0210] Specifically, the liquids L1, L2 are selected such that either the first mass density is greater than the second mass density and wherein the first refractive index is smaller than the second refractive index, or such that the first mass density is smaller than the second mass density and wherein the first refractive index is greater than the second refractive index.

[0211] This allows to render the lens 1 less susceptible to optical aberrations that are caused by gravity and other accelerating forces.

[0212] The lens 1 comprises a first elastically deformable membrane 3 that covers particularly under pretension the aperture 21 of the lens shaper 2.

[0213] The first membrane 3 is attached to the lens shaper 2 (or a separate element comprised by the lens shaper), at the lens shaper contour 20, where first membrane

[0214] 3 is attached to the lens shaper 2, a first boundary contour 30 is formed. The first boundary contour 30 in essence outlines a line of connection between the first membrane 3 and the lens shaper 2. The first boundary contour 30 encloses an area 31 of the first membrane 3 in which the first membrane 3 is deformable.

[0215] The first membrane 3 crosses the optical axis 100 and defines a first aperture 31 that is associated to the first membrane 3.

[0216] The first boundary contour 30 in essence follows the in particular inner, lens shaper contour 20.

[0217] The first boundary contour 30 is non-circular. Thus, the lens shaper contour 20 is non-circular.

[0218] The term “circular” and thus “non-circular” may be understood in the context of a two- dimensional plane. Therefore, in order to assess whether the first boundary contour 30, or for sake of any contour in the context of the current specification, when not comprised by a single plane is non-circular, the contour has to be embedded into a single plane, i.e. a reference plane has to be associated to the said contour.

[0219] There are several ways to associate such a reference plane to the contour. A first way is to define the term “non-circular” by way of projection of the contour onto a plane orthogonal to the optical axis, said plane being the reference plane.

[0220] A more concise definition may be achieved by the following: the reference plane is defined such that the contour has a smallest distance to said plane, i.e. a distance is of points comprised by the contour, e.g. the interface tabs, to the plane is determined, wherein the smallest distance is a sum (e.g. normalized by the number of points) of all said distances. A projection (in particular an orthogonal projection along the plane normal vector) of the contour onto this reference plane should result in a non-circular shape for the non-circular contour. This reference plane does not need to be oriented orthogonal to the optical axis.

[0221] A further definition, may be the following: a contour is considered non-circular, when in an actuation state of the lens in which the contour is comprised by a single plane, said contour is non-circular. It is of minor importance of the latter definition that the actuation state is actually adopted or adoptable by the lens, as long as such an actuation state in theory exists.

[0222] All three definitions provide unique advantages and drawbacks, however, the skilled person applying said definitions is enabled to determine whether the contour is circular or non-circular. Wherein in doubt, the last and the second to last definition (“smallest distance” plane and “actuation state”) seem most appropriate. In particular the first membrane 3 limits the first volume V1 from an outside medium of lens 1, such as surrounding air. The first membrane 3 in particular forms an optical surface of the lens 1.

[0223] When the lens shaper 2 is deformed, the first boundary contour 30 is deformed accordingly. This interplay is of particular importance, as the first boundary contour 30 is non-circular, which requires a more complex shaping of the first boundary contour 30 in order to provide a membrane shape that corresponds to a lens surface of a circular lens.

[0224] In the first volume V1 the first liquid L1 is comprised, wherein the first volume V1 is limited by the first membrane 3 on the first side of the lens 1.

[0225] In order to separate the first and the second liquid L1 , L2 from each other the lens 1 comprises a second membrane 4. The second membrane 4 separates the first from the second volume V1 ,V2 and is elastically deformable. The second membrane 4 comprises a first side 43 facing toward the first membrane 3 and a second side 44 facing in the opposite direction, i.e. toward the optical element 5.

[0226] The second membrane 3 according to the example shown in Fig. 1 is attached to an attachment component. In this case, the attachment component is the optical element 5. The second membrane 4 is attached circumferentially around a protruding portion 56 of the optical element 5 and encloses the second liquid L2 between the second side 44 of the second membrane 4 and the optical element 5.

[0227] The protruding portion 56 may be formed a rigid wall portion. Along the circumference of the protruding portion 56 a second boundary contour 40 of the second membrane 4 is formed that encloses the optical axis 100 of the lens 1 and an aperture 41 of the second membrane 4 as well as an aperture of the optical element 5. The second boundary contour 40 is non-circular as well. In particular, the shape (not necessary the size) of the non-circular portion is the same for the first and the second boundary contour 30, 40.

[0228] By way of selecting the first and the second liquid L1, L2 the lens 1 is rendered robust against acceleration-induced aberrations, particularly when the liquids are selected within the ranges provided for the refractive index and the mass density respectively in the current specification.

[0229] The optical element 5 of Fig. 1 comprises a first portion 51 and a second portion 52. The first portion 51 extends over the optical axis 100, wherein the second portion 52 extends circumferentially around the first portion 51. The first portion 51 in essence defines the aperture of the optical element 5, wherein the second portion 52 is adapted to serve a different purpose.

[0230] With respect to the first portion 51, the second portion 52 forms a step such that the second portion 52 provides an area that encloses the first portion 51, wherein the optical element 5 is thinner at the second portion 52 than at the first portion 51.

[0231] This step forms a recess 53 of the optical element 5. On the area of the second portion 52 the wall 6 is attached to the optical element 5.

[0232] Thus, the second portion 52 is set back with regard to the first portion 51 and the first membrane 3.

[0233] The recess 53 or step width 52 of the second portion 52 is formed such that the wall 6 may be compressed - and therefore bent towards the first portion 51 due to its “u”- shaped cross-section - without touching the first portion 51.

[0234] This allows for a particular compact design (along the optical axis) of the lens 1 while allowing a full stroke (and thus a comparably large adjustment range of a focal power of the lens), while maintaining gravity-induced aberration reduction. Only the specific interplay of all components allows for a lens with all these advantageous features combined.

[0235] In the following reference numerals as well as features that are in essence identical to the ones described previously, in particular in the context of Fig. 1 are not elaborated again, but are considered to apply to the following examples as well and in the identical or at least an analog fashion. Similarly, further features elaborated in the following Figures may be applied and / or combined to the exemplary embodiment shown in Fig. 1.

[0236] In Fig. 2 a variation of the embodiment shown in Fig. 1 is shown. The variation in essence features an annular element 7 that is comprised by the optical element 5. This element 7 forms an attachment surface of the wall 6 to the optical element 5.

[0237] In Fig. 3 another exemplary embodiment of the lens according to the invention is shown. This embodiment is based on the embodiments of Fig .1 and 2 but differs in particular in that the attachment component is not the optical element 5 but the lens shaper 2. Thus, the second membrane 4 is attached to the lens shaper 2.

[0238] In this example, the first membrane 3 is attached to a first side 23 of the lens shaper 2, wherein the first side 23 of the lens shaper 2 faces away from the optical element 5, wherein an opposite side - the second side 24 - of the lens shaper 2 faces toward the optical element 5.

[0239] The second membrane 4 is attached to the second side 24 of the lens shaper 2. The volume V1 for the first liquid L1 is therefore limited by the first and the second membrane 3, 4, and the lens shaper contour. The first volume V1 is therefore comparably thin.

[0240] The second volume V2 extends between the second side 44 of the second membrane 4 and the optical element 5.

[0241] It may be advantageous to overfill the first volume V1 such that the first and the second membrane 3, 4 would not touch.

[0242] In the following, the non-circularity of the first boundary contour 30 and the second boundary contour 40 are elaborated in form of several embodiments and details with respect to these embodiments.

[0243] Fig. 4 shows a view long the optical axis onto the first membrane of the lens.

[0244] The non-circular first boundary contour 30 is clearly recognizable. The lens shaper 2 comprises seven interface tabs 22 for the actuator assembly (not shown). Each actuator tab 22 may be actuated independently from each other by the actuator assembly and moved along the optical axis. In this example, the first boundary contour 30 is non-circular. In particular, in the actuation state shown, the first boundary contour 30 is comprised in a plane orthogonal to the optical axis. In this plane, there exists only a single axis of symmetry 102. That is the, the first boundary contour 30 is not only-non-circular, but also non-elliptical and non-oval.

[0245] Further, the shape of the first boundary contour 30 and the second boundary contour 40 are very similar in this embodiment.

[0246] A definition of similar contours is given in some previous embodiments and are elaborated in Fig. 5.

[0247] In Fig. 5, an example of a first and a second boundary contour 30, 40 is shown with a focus on similarity of the contours. The view is along the optical axis of the lens 1.

[0248] A reference contour 101 corresponds to the second boundary contour 40 isotropically scaled with a factor, wherein the first boundary contour 30 extends not further away from the reference contour 101 than 20% (indicated by the double arrow 103), in particular not further away from the reference contour than 10%, 5%, or 2% of a greatest extension direction 101-1 of the reference contour 101. These limits are indicated by the lines 104L and 10411.

[0249] This embodiment in essence allows for identical or almost identical scaled boundary contours 30, 40, wherein a deviation of an isotropically scaled boundary contour is provided as well for reference.

[0250] In Fig. 6, in essence the same lens 1 as in Fig. 1 is schematically shown in a schematic cross-sectional view focusing only on the first 31 and the second aperture 41 of the first 3 and the second membrane 4. Here, it can be seen that the first aperture 31 enclosed by the first boundary contour 30 and thus the lens shaper aperture 20, and the second aperture 41 enclosed by the second boundary contour 40 differ in size, wherein the aperture 41 of the second boundary contour 40 is smaller than the aperture 31 defined by the first boundary contour 30.

[0251] The degree to which the apertures 31, 41 differ is selected such that an aperture angle an associated to each of the first 31 and the second aperture 41 is the same, such that the effective aperture of the lens 1 is limited by both apertures 31, 41 to the same extent. The aperture angle a is defined for example as the angle measured between the optical axis 100 and the aperture from a center z of an image plane. The image plane may be comprised by an eye or a camera.

[0252] The first and the second boundary contour 30, 40 are identical by way of scaling of the contour isotropically.

[0253] In Fig. 7, a different kind of embodiment is shown for the lens 1 according to the invention. Here, the lens 1 comprises in essence an actuation volume VA and a lens volume VL. The actuation volume VA and the lens volume are fluidically connected, such that either the first liquid or the second liquid may travel back and forth between the volumes.

[0254] The lens volume VL comprises the optical axis 100 and all optical apertures of lens 1. The actuation volume VA in turn is arranged laterally shifted with regard to the lens volume VL.

[0255] The actuation volume VA is adjustable in size by means of the actuator assembly, (not shown) such as to adjust a pressure in the lens volume VL.

[0256] The lens shaper 2 is attached to a rigid housing portion 8 of the lens 1, rendering the lens shaper 2 partially flexible. Where the lens shaper 2 is attached to the housing portion 8 the lens shaper 2 is fixed to a certain location and cannot move. Where the lens shaper 2 is attached to the deformable wall 6 (similarly to the previous embodiments, except the wall 6 is not deformable around the complete circumference, but may form the rigid housing portion 8), the lens shaper 2 is deformable, e.g. when the pressure in the actuation volume VA and thus in the lens volume VL is adjusted.

[0257] Upon actuation, the pressure in the lens volume VL is adjusted, wherein the lens shaper 2 deforms only the portion where it is connected to the deformable portion of the wall 6. In Fig. 7B) and C) the cross-sections along the lines A-A and B-B in Fig. 7A) are shown.

[0258] Actuation is performed with a piston 9 that is located on a membrane limiting the actuation volume VA. The piston 9 may be pushed or pulled toward or away from the actuation volume VA thereby adjusting the pressure in the actuation and the lens volume VA, VL, In the example shown, the second liquid L2 is the liquid that extends also into the actuation volume VA. The first and the second membrane 3, 4 are both attached to the lens shaper 2.

[0259] Also, in this embodiment, the first and the second boundary contour 30, 40 comprise only a single axis of symmetry 102 (alog B-B) and thus are non-elliptic and non-oval.

[0260] The deformable wall 6 is shaped at least in parts as an elastic bellows (cf. Fig. 7C).

[0261] A variation of the embodiment of the lens shown in Fig. 7 is depicted in Fig. 8.

[0262] In Fig. 8, the main difference is that the second membrane 4 is attached to the optical element 5, wherein the optical element 5 comprises a transparent window portion 57 and a container portion 58 configured to receive said transparent window portion 57.

[0263] The container portion 58 forms a protruding portion 56 in the lens volume VL, in which the second liquid L2 is enclosed between the second membrane 4 and the optical element 5. The first liquid L1 extends into the actuation volume VA.

[0264] The mechanics of actuation and the partially flexible lens shaper 2 are identical to the embodiment Fig.7 and 1 with the mentioned differences.

[0265] In Fig. 9 several variants of the lens 1 according to the invention are shown. The differences lie in the location where the first and the membrane 3, 4 are attached to the lens shaper 2.

[0266] In the first variant Fig. 9A) the first membrane 3 is attached to a first side 23 of the lens 2 shaper and the second membrane 4 is attached to the second side 24 of the lens shaper 2 as elaborated in a previous embedment. In Fig. 9B) the second membrane 4 is attached to the second side 24 of the lens shaper 2. The first membrane 3 is attached to the second membrane 4, such that the first volume V1 is formed as a cushion-like structure enclosed solely by the first and the second membrane 3,4.

[0267] In Fig. 9C) the second membrane 4 is attached to the first side 23 of the lens shaper 2. In particular, the first membrane 3 is attached to the second membrane 4 or directly to the lens shaper 2.

[0268] Further variants are shown in Fig. 10. These variants in essence show variations of the optical element 5. In Fig. 10A) the optical element 5 comprises a window portion 57 as well as a container portion 58 comprising the window portion 57. The window portion 57 is a separate window element that is arranged in a corresponding recess of the container portion 58 of the optical element 5.

[0269] In Fig. 10B) the optical element 5 is a one-piece element, comprising the window portion 57 as well as the container portion 58.

[0270] An exemplary embodiment of the rigid element 5’ according to the second aspect is show in Fig. 11.

[0271] In Fig. 11, the optical element 5’ according to a lens of the second aspect is shown schematically. The optical element 5’ and in particular the aperture of the optical element is non-circular. A coordinate system associated to the rigid element 5’ is provided, wherein an x- and y-axis are shown in two direction indicated by the depicted axes. An extension of the rigid element along a z-axis, is provided in form of a gray scale coding. The brighter the gray value, the higher its associated z-axis value. In addition, contour lines are depicted that indicate contours of identical z- values of the rigid element 5’.

[0272] The optical element 5’ comprises a first section 5T and a second section 52’, wherein the first section 5T without loss of generality, in essence extends in a space corresponding to positive y-axis values, wherein the second section 52’ extend along the negative y-axis values.

[0273] The rigid element 5’ has been designed for a situation in which the lens T would be oriented orthogonally to gravity with its optical axis that points along the z-axis and oriented such that the positive y-axis points in an opposite parallel direction of gravity. This orientation may be referred to as the design direction or design orientation. A border section between the first and the second section 5T, 52’ extends in essence along the values of y=0. By way of the design of the first and the second section 51’, 52’, the first section 5T exhibits a different focal power than the second section 52’. In combination with a fluid or liquid comprised by the lens T (cf. Fig. 12) this leads to a compensation of gravity-induced aberration induced by the gravitational forces that cause the membrane 3’ to bulge non-symmetrically with respect to the optical axis, but to exhibit a sagging effect towards the negative y-axis.

[0274] The rigid element 5’ by means of the two sections allow to compensate this effect.

[0275] As the effect and the fluid dynamics may be simulated, it is possible to design the surface of the optical element to this compensate this effect.

[0276] In order to design the shape and contour of the rigid element 5’, optical properties of the assembled lens oriented along said design orientation can be simulated e.g. by ray tracing program. The simulation may further comprise a sag of the fluid or liquid comprised by the lens that leads to a non-symmetric curvature of the membrane when the lens is oriented along the design orientation.

[0277] The simulation may be executed on a lens having a rigid element devoid of any first or second section, i.e. a rigid element that provides the same refractive power over its complete aperture. From these results the shape and contour of the rigid element according to the second aspect may be derived.

[0278] Alternatively, the simulation is performed on a lens comprising the rigid optical element according to the second aspect, such that the shape and contour of the first and the second section is obtained directly form the simulation.

[0279] The simulation may comprise varying the first and the second sections in terms of their focal power, their size and geometry.

[0280] In addition, the optical properties of the lens may be determined for various focal states of the lens, ,i.e. for different curvatures of the membrane

[0281] In Fig. 12 a cross-section view of a lens T according to the second aspect is shown.

[0282] The lens T comprises the rigid optical element 5’, the rigid optical element 5’ forms a first side of a liquid volume V1 of the lens T in which in this example a liquid L1 is comprised. The liquid volume V1 is limited on a second side with an distensible membrane 3’ by means of a lens shaper 2’. A further lens 10’ is arranged on the optical axis 100’, as an exemplary embodiment of an optical system comprising the lens T according to the second aspect. The first section 5T of the rigid optical element 5’ and the second section 52’ of the rigid optical element 5’ may differ by more than 0.1 diopters.

[0283] Reference numerals

[0284] 1 liquid lens (1st aspect)

[0285] T fluid lens (2ndaspect)

[0286] 2 lens shaper

[0287] 2’ lens shaper (2ndaspect)

[0288] 20 lens shaper contour

[0289] 21 lens shaper aperture

[0290] 22 interface tabs

[0291] 23 first side of lens shaper

[0292] 24 second side of lens shaper

[0293] 3 first membrane

[0294] 3’ first membrane (2ndaspect)

[0295] 30 first boundary contour

[0296] 31 first area / first aperture

[0297] 4 second membrane

[0298] 40 second boundary contour

[0299] 41 second area / second aperture

[0300] 43 first side of second membrane

[0301] 44 second side of second membrane

[0302] 5 optical element

[0303] 5’ optical element (2ndaspect)

[0304] 5C center of optical element

[0305] 51 first portion

[0306] 52 second portion

[0307] 5T first sub-aperture section

[0308] 52’ second sub-aperture section

[0309] 53 circumferential recess

[0310] 54 depth of recess

[0311] 55 gap between wall and first portion 56 protruding portion

[0312] 57 window portion

[0313] 58 container portion

[0314] 6 wall

[0315] 7 annular element

[0316] 8 rigid housing portion

[0317] 9 piston

[0318] 10’ further lens

[0319] 100 optical axis

[0320] 100’ optical axis

[0321] 101 reference contour

[0322] 101-1 greatest extension of reference contour

[0323] 102 symmetry axis of the first and the second boundary contour

[0324] 103 Tolerance

[0325] 104U upper bound

[0326] 104L lower bound a aperture angle z center of image plane

[0327] L1 first liquid

[0328] L2 second liquid

[0329] V1 first volume

[0330] V2 second volume

[0331] VA actuation volume

[0332] VL lens volume

[0333] *****

Claims

Claims1. An adjustable liquid lens (1) comprising the following components:- an at least partially flexible lens shaper (2) having a lens shaper contour (20) enclosing a lens shaper aperture (21),- a first membrane (3) and a second membrane (4), wherein the first membrane (3) is attached to the lens shaper (2) or the second membrane (4), such that a first boundary contour (30) is formed where the first membrane (3) is attached to the lens shaper (2) or to the second membrane (4),- an optical element (5) forming a transparent portion around an optical axis (100) of the lens (1),- wherein the second membrane (4) is attached to an attachment component (2,3,5) selected from the group consisting of: a) the optical element (5), b) the lens shaper (2), c) the first membrane (3), such that a second boundary contour (40) is formed where the second membrane (4) is attached to the attachment component (2,3,5),- a first liquid (L1) enclosed in a first volume (V1) between the first membrane (3) and the second membrane (4),- a second liquid (L2) enclosed in a second volume (V2) between the optical element (5) and the second membrane (4),- an actuator assembly comprising at least one actuator, wherein the actuator assembly is configured to adjust the liquid lens (1) in a plurality of actuation states, and such that in one or more actuation states the lens shaper contour(20) lies partially outside of a plane associated to the lens shaper aperture(21), wherein o the first boundary contour (30) is non-circular, and / or o the second boundary contour (40) is non-circular, wherein the first liquid (L1) comprises a first mass density and a first refractive index, wherein the second liquid (L2) comprises a second mass density and a second refractive index, o wherein the first mass density is greater than the second mass density and wherein the first refractive index is smaller than the second refractive index, oro wherein the first mass density is smaller than the second mass density and wherein the first refractive index is greater than the second refractive index.

2. The liquid lens (1) according to claim 1, wherein the actuator assembly is configured to deform the lens shaper (2) or a part of the lens shaper (2) in direction of the optical axis (100) of the lens (1) such that the lens shaper contour (20) lies partially outside of a single plane associated to the lens shaper aperture (21).

3. The liquid lens (1) according to one of the preceding claims, wherein a portion in which the lens shaper (2) is flexible comprises more than 2.5% of a circumference of the lens shaper contour (20), preferably more than 50% of the circumference of the lens shaper contour (20), and most preferably more than 97.5%of the circumference of the lens shaper contour (20).

4. The liquid lens (1) according to one of the preceding claims, wherein the actuator assembly is configured to adjust a liquid pressure in the first or the second liquid (L1, L2), such as to deform the first membrane (3) and / or the second membrane (4) within the first boundary contour (30) or the second boundary contour (40).

5. The liquid lens (1) according to one of the preceding claims, wherein the first boundary contour (30) encloses a first aperture (31) and the second boundary contour (40) encloses a second aperture (41), wherein the first aperture (31) is more than 5%, more than 10%, or more than 20% greater than the second aperture (41), particularly wherein the first aperture is more than 100% greater than the second aperture.

6. The liquid lens (1) according to one of the preceding claims, wherein a reference contour (101) corresponds to the second boundary contour (40) isotropically scaled with a factor, wherein the first boundary contour (30) extends not further away from the reference contour (101) than 20% of a greatest extension direction (101-1) of the reference contour (100).

7. The liquid lens (1) according to claim 5, wherein the first and the second aperture (31, 41) each limit an aperture angle (a) with respect to a center (z) of an image plane of the lens (1), wherein the first and the second aperture (31 , 41) are selected such that the aperture angle (a) is identical for the first and the second aperture (31, 41).

8. The liquid lens according to one of the preceding claims, wherein the lens shaper (2) is attached to an elastically deformable circumferential wall (6) of the lens (1), wherein upon actuation, the wall (6) is compressed or extended along the optical axis (100).

9. The liquid lens (1) according to claim 8, wherein the optical element (5) comprises a first (51) and a second portion (52), wherein the second portion (52) forms a circumferential recess (53) with regard to the first portion (51) around a center (5C) of the optical element (5), wherein the wall (6) is attached to the recess (53).

10. The liquid lens (1) according to claim 7 and 9, wherein a boundary between the first portion (51) and the second portion (52) of the optical element (5) encloses an aperture angle of the optical element (5) with respect to the center (z) of the image plane of the lens (1), wherein the aperture angle of the optical element (5) is equal or greater than the smaller of the aperture angles (a) of the first and the second aperture (31, 41).

11. The liquid lens (1 ) according to one of the claims 8 to 10, wherein a width of the circumferential recess (53) is adjusted such that at full stroke of the lens shaper (2), a gap between the compressed wall (6) and the first portion (51) of the optical element (5) is maintained.

12. The liquid lens (1) according to one of the claims 9 to 12, wherein a depth (54) of the recess (53) is smaller than a full stroke of the lens shaper contour (20).

13. The liquid lens (1) according to one of the claims 9 to 13, wherein the wall (6) has a U-shaped cross-section along a plane comprising the optical axis (100),wherein an opening of the “u” of the U-shaped cross-section points away from the optical axis (100).

14. The liquid lens (1) according to one of the preceding claims, the first boundary contour (31) and / or the second boundary contour (42) is symmetrical with respect to exactly one axis (102).

15. An adjustable fluid lens (T) having an optical axis (100’) comprising:- a lens shaper (2’),- a first membrane (3’) attached to the lens shaper, such that a first boundary contour is formed where the first membrane (3’) is attached to the lens shaper (2’),- a rigid optical element (5’) arranged on the optical axis (100’),- an actuator assembly comprising at least one actuator, wherein the actuator assembly is configured to adjust the lens (T) in a plurality of actuation states exhibiting an adjusted curvature of the first membrane (3’), wherein for actuation states of the lens (1) in which the first boundary contour is comprised in a plane, the first boundary contour is non-circular,- wherein the rigid optical element (5’) comprises a first sub-aperture section (5T) configured to confer a first focal power to the optical element (5’) and a second sub-aperture section (52’) configured to confer a second focal power to the optical element (5’), wherein the first and the second sub-aperture sections (5T, 52’) are arranged on opposite sides of a design plane extending parallel to or on the optical axis (100’) of the lens (1 ’), wherein a difference between the first focal power and the second focal power is at least 0.1 diopters, wherein the first and the second sub-aperture sections (51’,52’) are designed to compensate an acceleration-induced, in particular local, focal power variation of the lens (T).

16. The fluid lens (T) according to claim 15, wherein the acceleration-induced acceleration is a gravity-induced acceleration.

17. The fluid lens (T) according to claim 15 or 16, wherein the first sub-aperture section (5T) comprises a first curvature of the optical element (5’), and the second sub-aperture section (52’) comprises a second curvature of the optical element (5’), to convey the differing first and second focal power.

18. The fluid lens (T) according to one of the claims 15 to 17, wherein the optical element (5’) comprises a design focal power, wherein the first focal power is greater than the design focal power and wherein the second focal power is smaller than the design focal power - or vice versa.

19. The fluid lens (T) according to claim 19, wherein the optical element (5’) comprises design curvature designed to convey the design focal power to the optical element (5’), wherein the first curvature in the first sub-aperture section (5T) is greater than the design curvature and the second curvature in the second sub-aperture section (52’) is smaller than the design curvature - or vice versa.

20. The fluid lens (T) according to one of the claims 15 to 19, wherein the rigid optical element (5’) is designed as a refractive element.

21. The fluid lens (T) according to one of the claims 15 to 20, wherein the fluid lens (T) comprises a fluid, such as a first liquid, wherein the rigid optical element (5’) is in direct contact with the fluid, which is disposed between the first membrane (3’) and the rigid optical element (5’).

22. A design and fabrication method for an optical element (5’) configured to compensate an acceleration-induced, in particular a gravity-induced, aberration in a non-circular fluid lens (T) with the rigid optical element (5’), the method comprising the following steps:- simulating an acceleration-dependent aberration of the non-circular fluid lens, when the lens is oriented with its optical axis along one or more design directions with respect to a direction of the acceleration,- in a computer-implemented modelling step, modelling optical surfaces of the optical element by optimizing, in particular by ray-tracing method, a non- rotational symmetric surface sag component of the optical surfaces, to reduce the acceleration-induced aberration by at least 10% of the lens when the lens is oriented along the design direction, and- fabricating the optical element according to the results of the modelling step.

23. The rigid optical element design method according to claim 22, wherein the modelling of the optical surfaces comprises modelling a first sub-aperture section (5T) configured to confer a first focal power to the optical element and a second sub-aperture section (52’) configured to confer a second focal power to the optical element (5’), wherein the first and the second subaperture sections (5T, 52’) are arranged on opposite sides of a design plane extending parallel to or on the optical axis (100’) of the lens (T), wherein a difference between the first focal power and the second focal power is at least 0.1 diopters, wherein the first and the second sub-aperture sections (5T, 52’) are designed to compensate the acceleration-induced aberration.

24. The rigid optical element design method according to claim 22 or 23, wherein the simulating step comprises a finite element method by applying a hydrostatic pressure gradient to a first membrane of the liquid lens.

25. The rigid optical design method according to one of the claims 22 to 24, wherein the fluid lens is a fluid lens (T) according to one of the claims 15 to 21.

26. The rigid optical element design method according to one of the claims 22 to25, wherein simulating and / or modelling is based on numerical calculations.*****

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