Liquids for tunable optical devices and use thereof

Abstract

The invention relates to an optical tunable device, wherein the optical tunable device comprises a membrane, delimiting at least partially a volume, wherein the volume is filled with a liquid comprising at least one siloxane based polymer compound comprising n repeating units and comprising at least one moiety X in a repeating unit UX, wherein X is selected from (Cm-alkyl)-R1, and wherein the siloxane based polymer compounds.

Description

[0001] Liquids for tunable optical devices and use thereof

[0002] The present invention relates to an optical tunable device comprising a volume and a membrane, wherein the membrane delimits the volume at least partially and the volume is filled with a siloxane-based polymer compound. Furthermore, the present invention relates to a siloxane based polymer compound and use of said siloxane based polymer compound in an optical tunable device.

[0003] Background of the Invention

[0004] An optical device, such as a tunable lens, typically comprises a transparent and elastically expandable membrane, an optical element opposing (facing) the membrane and a wall connecting the optical element to the membrane. The membrane, the optical element, and the wall delimit a volume of the lens, which is filled with a liquid.

[0005] The focus of the lens can be adjusted by changing the curvature of the membrane. This may for instance be achieved by using an actuator that presses a holding ring against the membrane so as to deform an optically active part of the membrane (LIS2010202054).

[0006] Also known are lens assemblies in which a force is directly exerted on the membrane e.g., by means of a coil (WO2010104904) or by means of a ring-shaped piston that directly indents the membrane in order to deform it (US2011267703).

[0007] Alternatively, the optical behavior of the membrane can be changed by using a wall that is designed to be adjustable in height with respect to the optical element. By amending the height of the wall, the pressure of the fluid residing inside the volume and therewith a curvature of the membrane, and / or the spatial position of the membrane with respect to the optical element is adjusted.

[0008] Based on the chemical structure and composition, most elastomeric membrane materials suitable for the use in tunable liquid lenses suffer from effects based on solubility and swellability caused by the liquid filled in the volume.

[0009] The present invention aims to expand the spectrum of liquids which are suitable for use in tunable lenses based on a liquid-elastomer technology using polydimethylsiloxane (PDMS) membranes and substituted PDMS. The liquids of the invention allow the use of PDMS and substituted PDMS in a broad spectrum of possible applications with different requirements applying the many positive properties, such as low-temperature flexibility, long-term stability under UV, heat and moisture stability and high transmission. This objective is attained by the subject-matter of the independent claims of the present specification, with further advantageous embodiments described in the dependent claims, examples, figures and general description of this specification.

[0010] Summary of the Invention

[0011] Liquids which are suitable for the use in optical devices, such as tunable lenses have to meet certain criteria. A suitable molecule needs to contain a spectrum of properties where the chemical affinity to the membrane environment such as a PDMS matrix and the 3-dimensional structure and stability of the membrane are in balance. An important role plays a low solubility (typically less than 1.5%) so the molecules of the liquid do not penetrate the surface nor bulk of the surrounding polymer network of the membrane so as to avoid extensive swelling of the membrane.

[0012] While in the ideal case no measurable swelling is observed in the targeted temperature range from -40°C to +85°C (the case for larger alkyl- and Nitril- functionalized Siloxanes), there are applications where up to 4% or eventually even more swelling is allowed (measured with Methyl-Phenyl-modified siloxanes) under the condition that the application does not see abrupt changes of the environmentally relevant conditions (such as temperature changes of more than about 20°C per minute). Dissolution and diffusion should both be fully reversible. To monitor these processes, exact test conditions are of fundamental importance to allow a decision of the compatibility of the molecule with respect to a certain membrane.

[0013] The specific limit of swelling that may be tolerated is a case and application specific question. For example, liquids for lenses that will be used at high temperature or high-pressure conditions might be assessed differently compared to liquids for lenses that will be used at low temperatures because the swelling and diffusivity is temperature dependent, i.e. , the solubility of the liquid in the elastomer of the membrane increases with temperature and thus the swelling. A thermal shock on an elastomer such as PDMS can lead to a situation of oversaturation with the result that the liquid is pressed out of the polymer matrix, creating surface effects such as thin films and later nucleation and droplet formation on the surface. Nevertheless, in specific conditions a maximum of 5 % swelling is tolerable.

[0014] Finally, the material pair of liquid and elastomer prove compatible for optical applications when its complete spectrum of properties do not allow the liquid molecule to penetrate into the polymer bulk - or when its complete spectrum of properties do not allow the molecule to penetrate through the polymer bulk and through the surface at the same time and as long as the polymer network is not affected in instable manner. This might be given if the affinity is high and stops the molecule from being released into another medium (gas or another fluid). The present invention describes an optical tunable device that comprises a volume filled with a liquid (siloxane base polymer compound) that fulfils the criteria described above with regard to a PDMS membrane material.

[0015] A first aspect of the invention relates to an optical tunable device, wherein the optical tunable device comprises a membrane, delimiting at least partially a volume, wherein the volume is filled with a liquid comprising at least one siloxane based polymer compound comprising n repeating units and comprising at least one moiety X a repeating unit UX, wherein X is selected from (Cm-alkyl)-R1, wherein m is an integer from 0 and 20; and o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CFhjp-CHs or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CFkjq-CHs or (CF^jq-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 1 , 500, in particular 1 and 100, in particular 10 to 90.

[0016] As described above, tunable lenses based on a liquid-elastomer technology comprise a volume that is at least partially delimited by an elastic membrane which contacts the liquid filled in said volume. The focus of the tunable lens can be adjusted by changing the curvature of the elastic membrane. Means for adjusting the curvature of the membrane are known to those of skill in the art. A non-limiting example for such device is shown in Fig. 1 and Fig. 2.

[0017] A second aspect of the invention relates to a compound of a general formula 1

[0018] (1), wherein each X1is independently from any other X1selected from (Cm-alkyl)-R1, wherein

[0019] ■ m is an integer from 0 and 20; and R1is selected from wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 1 , 500, in particular 1 and 100, in particular 10 to 90. each X2is independently from any other X2selected from (Cm-alkyl)-R1or Ci-20-alkyl-R1, wherein

[0020] ■ m is an integer from 0 and 20; and

[0021] Z .R2

[0022] ■ R1is A , wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 ,, n is an integer from 1 and 100, in particular 10 to 90, and

[0023] R5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated.

[0024] A third aspect of the invention relates to a compound of a general formula 1

[0025] (1), wherein each X1is independently from any other X1selected from (Cm-alkyl)-R1, wherein

[0026] ■ m is an integer from 0 and 20; and R1is selected from wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 1 , 500, in particular 1 and 100, in particular 10 to 90. each X2is independently from any other X2selected from (Cm-alkyl)-CH3, wherein m is an integer from 0 and 20 and R5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated.

[0027] Any embodiment discussed under the first aspect of the invention can also be applied to the second or third aspect of the invention.

[0028] A fourth aspect of the invention relates to the use of a compound of formula 1 as described in the first aspect of the invention in an optical system.

[0029] Terms and definitions

[0030] For purposes of interpreting this specification, the following definitions will apply and whenever appropriate, terms used in the singular will also include the plural and vice versa. In the event that any definition set forth below conflicts with any document incorporated herein by reference, the definition set forth shall control.

[0031] The terms “comprising,” “having,” “containing,” and “including,” and other similar forms, and grammatical equivalents thereof, as used herein, are intended to be equivalent in meaning and to be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. For example, an article “comprising” components A, B, and C can consist of (i.e., contain only) components A, B, and C, or can contain not only components A, B, and C but also one or more other components. As such, it is intended and understood that “comprises” and similar forms thereof, and grammatical equivalents thereof, include disclosure of embodiments of “consisting essentially of” or “consisting of.”

[0032] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit, unless the context clearly dictate otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure.

[0033] Reference to “about” a value or parameter herein includes (and describes) variations that are directed to that value or parameter per se. For example, description referring to “about A” includes description of “A”.

[0034] As used herein, including in the appended claims, the singular forms “a,” “or,” and “the” include plural referents unless the context clearly dictates otherwise.

[0035] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0036] The term Cm-alkyl in the context of the present specification relates to an alkyl moiety consisting of a certain number (m) of C atoms. The alkyl moiety may be linear or branched. For instance, n-butyl, 2-methylpropyl and tert-butyl are examples for m being 4.

[0037] The term PDMS relates to polydimethylsiloxane (CAS No. 63148-62-9).

[0038] The term substituted PDMS refers to at least partially functionalised PDMS by additional substituents such as phenyl or fluoride.

[0039] The term alkyl in the context of the present specification relates to a saturated linear, branched or (partially or completely) cyclic hydrocarbon, wherein in certain embodiments one carboncarbon bond may be unsaturated and one CH2 moiety may be exchanged for oxygen (ether bridge) or nitrogen (NH, or NR with R being methyl, ethyl, or propyl; amino bridge). The term unsubstituted Cm-alkyl when used herein in the narrowest sense relates to the moiety -CmH2m- if used as a bridge between moieties of the molecule, or -CnH2n+i if used in the context of a terminal moiety. It may still contain fewer H atoms if used in the context of a cyclical structure.

[0040] The term Ci-4-alkyl in the context of the present specification relates to a saturated linear or branched hydrocarbon having 1 , 2, 3 or 4 carbon atoms. Non-limiting examples for a C14 alkyl are methyl, ethyl, propyl, prop-2-enyl, n-butyl, 2-methylpropyl, tert-butyl, cyclo-butyl, cyclopropyl, methyl-cyclo-propyl. In certain embodiments, a C1-4- alkyl is a methyl, ethyl, propyl or butyl moiety.

[0041] A Ci-6-alkyl in the context of the present specification relates to a saturated linear or branched hydrocarbon having 1 , 2, 3, 4, 5 or 6 carbon atoms. Non-limiting examples for a Ci-Ce alkyl include the examples given for Ci-4-alkyl above, and additionally n-pentyl, 2-methylbutyl, 3- methylbutyl, 1 , 1-dimethylpropyl, 1 ,2-dimethylpropyl, 1 ,2-dimethylpropyl, cyclo-pentyl, cyclo- hexyl, methyl-cyclo-pentyl. In certain embodiments, a Cs alkyl is a pentyl or cyclopentyl moiety and a Ce alkyl is a hexyl or cyclohexyl moiety.

[0042] The term C -cycloalkyl in the context of the present specification relates to a saturated hydrocarbon ring having 4, 5, 6 or 7 carbon atoms, wherein in certain embodiments, one carbon-carbon bond may be unsaturated and / or one CH2 moiety may be exchanged for oxygen (ether bridge) or nitrogen (NH, or NR with R being methyl, ethyl, or propyl; amino bridge). Non-limiting examples of a C4-7-cycloalkyl moiety include cyclobutyl (-C4H7), cyclopentenyl (C5H9), and cyclohexenyl (CeHn) moieties.

[0043] The term amine-substituted [group] refers to a moiety or group that is modified by one or several amine groups -NHR or -NR2, or derivatives thereof, with each R being defined further in the description.

[0044] A polymer of a given group of monomers is a homopolymer (made up of a multiple of the same monomer); a copolymer of a given selection of monomers is a heteropolymer constituted by monomers of at least two of the group.

[0045] The term substituted in its broadest sense refers to an alkyl or phenyl that is substituted in one or several carbon atoms. Non-limiting examples include -CH2F, -CHF2, -CF3, -(CFh^F, - (CHF)2H, -(CHF)2F, -C2F5, -(CH2)3F, -(CHF)3H, -(CHF)3F, -C3F7, -(CH2)4F, -(CHF)4H, -(CHF)4F and -C4F9, -SCF3, -OCF3, -SFS, -NCF3, -(NCH3)F, -(NH)F. A similar definition applies to a substituted alkyl that is substituted in one or several carbon atoms by with phenyl.

[0046] Detailed Description of the Invention

[0047] A first aspect of the invention relates to an optical tunable device, wherein the optical tunable device comprises a membrane, delimiting at least partially a volume, wherein the volume is filled with a liquid comprising at least one siloxane based polymer compound comprising n repeating units and comprising at least one moiety X in a repeating unit UX, wherein X is selected from (Cm-alkyl)-R1, wherein

[0048] ■ m is an integer from 0 and 20; and

[0049] ■ R1is selected from , wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2-R4, -CF2- R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 1 and 500.

[0050] In certain embodiments, the invention relates to an optical tunable device, wherein the optical tunable device comprises a membrane, delimiting at least partially a volume, wherein the volume is filled with a liquid comprising at least one siloxane based polymer compound comprising n repeating units and comprising at least one moiety X in a repeating unit UX, wherein X is selected from (Cm-alkyl)-R1, wherein

[0051] ■ m is an integer from 0 and 20; and

[0052] ■ R1is selected from , wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2-R4, -CF2- R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 1 and 100, in particular 10 to 90.

[0053] In certain embodiments, the invention relates to an optical tunable device, wherein the optical tunable device comprises a membrane, delimiting at least partially a volume, wherein the volume is filled with a liquid comprising at least one siloxane based polymer compound comprising n repeating units and comprising at least one moiety X in a repeating unit UX, wherein X is selected from (Cm-alkyl)-R1, wherein

[0054] ■ m is an integer from 0 and 20; and

[0055] ■ R1is selected from , wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2-R4, -CF2- R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 100 and 500.

[0056] In certain embodiments, n is an integer from 10 to 50.

[0057] In certain embodiments, n is an integer from 10 to 30.

[0058] In certain embodiments, n is an integer from 10 to 20.

[0059] In certain embodiments, n is an integer from 20 to 30.

[0060] In certain embodiments, n is an integer from 60 to 90.

[0061] In certain embodiments, n is an integer from 70 to 90.

[0062] In certain embodiments, the optical tunable device is a lens.

[0063] In certain embodiments, the membrane comprises a PDMS or substituted PDMS, particularly is PDMS or substituted PDMS.

[0064] The PDMS or the substituted PDMS is optical transparent.

[0065] The focus of the lens can be adjusted by changing the curvature of the membrane. This may for instance be achieved by using an actuator that presses a holding ring against the membrane, by means of a coil or by means of a ring-shaped piston that directly indents the membrane in order to deform it, or by using a wall that is designed to be adjustable in height with respect to the optical element.

[0066] A non-limiting example of an optical tunable device that may be filled with a siloxane based polymer compound is shown in the Figures.

[0067] As described above, tunable lenses based on a liquid-elastomer technology comprise a volume that is at least partially delimited by an elastic membrane which contacts the liquid filled in said volume. The focus of the tunable lens can be adjusted by changing the curvature of the elastic membrane. Means for adjusting the curvature of the membrane are known to those of skill in the art. A non-limiting example for such device is shown in Fig. 1 and Fig. 2.

[0068] In certain embodiments, the PDMS or the substituted PDMS is purely elastic with low viscoelastic damping.

[0069] In certain embodiments, the PDMS is unsubstituted PDMS.

[0070] In certain embodiments, the optical tunable device comprises a device that is designed to adjust the curvature of the membrane. In certain embodiments, the optical tunable device comprises an actuator to adjust the curvature of the membrane.

[0071] In certain embodiments, the optical tunable device comprises a ring, a coil or a piston that is designed to adjust the curvature of the membrane or a wall that is designed to be adjustable in height to adjust the curvature of the membrane.

[0072] The volume is filled with a siloxane based polymer compound. The polymer comprises n repeating units UX, wherein n is an integer from 1 to 100, particularly from 10 to 90, wherein the repeating units UX are characterized by side chains X1and X2.

[0073] Typically, the n number is in the range of 1 to 100, particularly 10 to 90. Within this range, basic compatibility and neglectable swelling of the elastic membrane material is achieved. Of note, the viscosity increases with increasing number of monomers n. For most applications, a low viscosity is preferred since it leads to a higher tuning speed of the adaptive element - especially at lower temperatures. Nevertheless, a high viscosity can be preferred when the dynamics of the optical is of less importance, but the robustness towards mechanical shocks, low vapour pressures, robustness against cavitation (with induced bubble formation) or comparable are preferred. Nevertheless, at low or very low temperatures, such low molecular weight type of liquids may be preferred. These extreme conditions (high / low temperatures; high / low pressures) are likely to be found in space applications, where tunable optical devices such as focus tunable lenses can significantly reduce the weight of optical systems.

[0074] For optical tunable devices specifically used at high temperatures (e.g.,40° to 150 °C), the Standard Temperature and Pressure (STP) viscosity of the polymer should be high.

[0075] Suitable membranes are optically transparent, have low viscoelastic damping and show chemical and physical stability (including stable elasticity) over a very broad temperature range, i.e. at least from minus 40°C to 200°C.

[0076] In certain embodiments, the membrane is transparent and stable at a temperature between - 40 °C and +200 °C.

[0077] In certain embodiments, the optical tunable device the siloxane based polymer compound is a polymer with one repeating unit UX or a co-polymer with only one type of repeating unit UX and at least one further repeating unit FU, wherein the ratio of UX to FX is higher than 1 : 100, in particular higher than 5 : 100, more particularly higher than 10 : 100, more particularly higher than 25 : 100, more particularly higher than 50 : 100. more particularly higher than 75 : 100. Here, n is to be understood as the number of repeating units UX plus the number of further repeating units FU. In certain embodiments, the volume is filled with at least one siloxane based polymer compound and comprises additives, in particularly additives to change the stability of materials such as inhibitors or absorbers.

[0078] In certain embodiments, the volume is filled with a mixture of two or more siloxane based polymer compounds. This allows the adjustment of the optical properties such as refractive index or density.

[0079] In certain embodiments, the volume is filled with a mixture of two or more siloxane based polymer compounds and comprises additives, in particularly additives to change the stability of materials such as inhibitors or absorbers.

[0080] In certain embodiments, the polymer compound is a polymer with only one type of repeating unit UX.

[0081] In certain embodiments, the polymer compound comprises a viscosity in a range between 0.1 mPa*s and 10 000 mPa*s, particularly in a range between 1 mPa*s and 5 000 mPa*s, more particularly in a range between 10 mPa*s and 2500 mPa*s.

[0082] In certain embodiments, the polymer compound comprises a viscosity in a range between 100 mPa*s and 2000 mPa*s, particularly in a range between 500 mPa*s and 1500 mPa*s,

[0083] Viscosity mentioned above is valid for temperatures between 0°C and 40°C, particularly between 10 and 30°, more particularly between 15 and 25°C.

[0084] In certain embodiments, the polymer compound remains fluidic at temperatures as low as - 40°C or below, particularly down to -40°C, more particularly to temperatures below -20°C.

[0085] In certain embodiments, the refraction index is in a range of 1.4 to 1.8, particularly in a range of 1.5 to 1.7, more particularly 1.5 to 1.6.

[0086] In certain embodiments, the at least one siloxane based polymer compound is of a general formula 1 ,

[0087] (1), wherein each X1is independently from any other X1selected from (Cm-alkyl)-R1, wherein

[0088] ■ m is an integer from 0 and 20; and ■ R1is selected from wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2-R4, -CF2- R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, each X2is independently from any other X2selected from (Cm-alkyl)-R1or Ci-20-alkyl-R1, wherein

[0089] ■ m is an integer from 0 and 20; and

[0090] ■ R1is selected from wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2-R4, -CF2- R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 1 to 100, in particular 10 to 90, and

[0091] R5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated.

[0092] The use of different X1and X2leads to a copolymer structure with different repeating units defined by X1and X2.

[0093] In certain embodiments, the at least one siloxane based polymer compound is of a general formula 1 ,

[0094] (1), wherein each X1is independently from any other X1selected from (Cm-alkyl)-R1, wherein

[0095] ■ m is an integer from 0 and 20; and

[0096] R1is selected from wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, each X2is independently from any other X2selected from (Cm-alkyl)-R1or Ci-20-alkyl , wherein

[0097] ■ m is an integer from 0 and 20; and o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 100 to 500, and

[0098] R5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated. In certain embodiments, the at least one siloxane based polymer compound is of a general formula 1 ,

[0099] (1), wherein each X1is selected from (Cm-alkyl)-R1, wherein m is an integer from 0 and 20; and o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2-R4, -CF2- R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, each X2is selected from (Cm-alkyl)-R1or Ci-20-alkyl-R1, wherein m is an integer from 0 and 20; and o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2-R4, -CF2- R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 1 to 100, in particular 10 to 90, and

[0100] R5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated.

[0101] In certain embodiments, the at least one siloxane based polymer compound is of a general formula 1 ,

[0102] (1), wherein

[0103] X1is selected from (Cm-alkyl)-R1, wherein

[0104] ■ m is an integer from 0 and 20; and o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, and

[0105] X2is selected from Ci-20-alkyl, particularly Ci- -alkyl, more particularly Ci-3-alkyl; n is an integer from 100 to 500, and

[0106] R5is selected from Ci-6-alkyl, particularly Ci-3-alkyl, more particularly Ci-alkyl, which can be partially or completely fluorinated.

[0107] In certain embodiments, the at least one siloxane based polymer compound is of a general formula 1 ,

[0108] (1), wherein

[0109] X1is selected from (Cm-alkyl)-R1, wherein m is an integer from 0 and 20; and

[0110] R1is selected from wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2-R4, -CF2- R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, and

[0111] X2is selected from Ci-20-alkyl, particularly Ci-10-alkyl, more particularly Ci-6-alkyl; n is an integer from 1 to 100, in particular 10 to 90, and

[0112] R5is selected from Ci-6-alkyl, particularly Ci-3-alkyl, more particularly Ci-alkyl, which can be partially or completely fluorinated. ,

[0113] In certain embodiments, R1is selected from Embodiments comprising show an improved compatibility with respect to PDMS it is better due to the lower solubility compared to siloxanes comprising larger alkyl chains or CN substituents.

[0114] . / r2

[0115] In certain embodiments, R1is selected from A / R2

[0116] Embodiments comprising A show a lower solubility regarding to a PDMS membrane compared to siloxanes comprising larger alkyl chains or CN substituents. / R2

[0117] Embodiments comprising A show a lower solubility regarding to a PDMS membrane compared to siloxanes comprising larger alkyl chains or CN substituents.

[0118] In certain embodiments, X1or X2, particularly X1is selected from (Cm-alkyl)-R1, wherein m is an integer from 0 and 20; and wherein o A is selected from -OCF2-, or -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1

[0119] In certain embodiments, A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from -CF3 or -CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3.

[0120] In certain embodiments, A is selected from -SCF2-, -OCF2-, -NH-, -N(CH3)-, S- or -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3.

[0121] In certain embodiments, A is selected from -OCF2-, -NH-, -N(CH3)-, or -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3.

[0122] In certain embodiments, A is selected from -NH-, -N(CH3)- or -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3,

[0123] In certain embodiments, A is selected from more particularly -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3.

[0124] In certain embodiments, A is selected from -NH-, -N(CH3)-, or -O- and R2is -CF3.

[0125] In certain embodiments, A is -O- and R2is -CF3..

[0126] In certain embodiments, R2is -CF3. In certain embodiments, B is selected from F, SCF3, OCF3, CF3, SCF2-R4, OCF2-R4, CF2-R4, wherein R4is selected from (CH2)q-CH3.

[0127] In certain embodiments, B is selected from F, SCF3, OCFs or CF3.

[0128] In certain embodiments, B is selected from SCF3, OCFs or CF3.

[0129] In certain embodiments, B is selected from SCF3 or OCF3.

[0130] In certain embodiments, B is selected from SCF3.

[0131] In certain embodiments, B is F.

[0132] In certain embodiments, o is an integer from 1 to 5.

[0133] In certain embodiments, o is an integer from 2 to 5, particularly from 3 to 5.

[0134] In certain embodiments, o is an integer from 4 to 5, particularly o is 5.

[0135] In certain embodiments, o is an integer from 1 to 5

[0136] In certain embodiments, q is an integer from 0 to 20, particularly an integer from 0 to 12, more particularly 0 to 6.

[0137] In certain embodiments, R3is -(CH2)P-CH3, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 .

[0138] In certain embodiments, R6is -(CH2)P-CH3, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 1 .

[0139] In certain embodiments, m is an integer from 0 to 12, particularly 0 to 6.

[0140] In certain embodiments, m is 0.

[0141] In certain embodiments, m is an integer from 0 to 4.

[0142] In certain embodiments, m is 0 and o is 1.

[0143] In certain embodiments, m is an integer from 2 to 4.

[0144] In certain embodiments, m is an integer from 2 to 4 and 0 is 5.

[0145] In certain embodiments, n is an integer from 10 to 20 and X1is selected from -OCF2-, -NH-, - N(CH3)-, or -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from - (CH2)P-CH3, in particular from -NH-, -N(CH3)- or -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3, more particularly from more particularly -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3.

[0146] A substituent OCF3 or OCF2- provides a fluid with a good range of viscosity and a low solubility with respect to PDMS. In certain embodiments, n is an integer from 20 to 30 and X1is selected from -OCF2-, -NH-, - N(CH3)-, or -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from - (CH2)P-CH3, in particular from -NH-, -N(CH3)- or -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3, more particularly from more particularly -O- and R2is selected from -CF3 or -CF2-R3, particularly CF3, and wherein R3is selected from -(CH2)P- CH3.

[0147] In certain embodiments, n is an integer from 70 to 90 and X1is selected from is selected from -OCF2-, -NH-, -N(CH3)-, or -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3, in particular from -NH-, -N(CH3)- or -O- and R2is selected from - CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3, more particularly from more particularly -O- and R2is selected from -CF3 or -CF2-R3, particularly CF3, and wherein R3is selected from -(CH2)P-CH3.

[0148] In certain embodiments, X2is selected from Ci-20-alkyl.

[0149] In certain embodiments, X2is selected from Ci- -alkyl.

[0150] In certain embodiments, X2is selected from Ci-6-alkyl.

[0151] In certain embodiments, X2is selected from Ci-3-alkyl.

[0152] In certain embodiments, R5is selected from Ci-3-alkyl, which can be partially or completely fluorinated.

[0153] In certain embodiments, R5is Ci-alkyl, which can be partially or completely fluorinated.

[0154] In certain embodiments, the compound is selected from one of the following

[0155]

[0156] In certain embodiments, the compound is (Phenylmonofluoride).

[0157] For an optical tunable device comprising a liquid of this siloxane based polymer an increased swelling and a decreased evaporation was observed.

[0158] The Phenylmonofluoride sowhed after 120 days a swelling (at 85°C) of less than < +1.5% and the evaporation was (at 85°) less than <-0.2%. The density is 1.2 and the refraction index (589.3 nm at 20°C) is 1.5138 with a transmission of 90.27%. There were no diffusion droplet. A second aspect of the invention relates to a compound of the general formula 1

[0159] (1), wherein each X1is independently from any other X1selected from (Cm-alkyl)-R1, wherein

[0160] ■ m is an integer from 0 and 20; and R1is selected from wherein o A is selected from -SCF2, -OCF2.-NH-, -N(CH3)-, S- or -O- and R2is - CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3 or -(CH2)P- phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2-R4, -CF2- R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, each X2is independently from any other X2selected from (Cm-alkyl)-R1or Ci-20-alkyl-R1, wherein m is an integer from 0 and 20; and o A is selected from -SCF2, -OCF2.-NH-, -N(CH3)-, S- or -O- and R2is - CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3 or -(CH2)P- phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2-R4, -CF2- R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 1 and 100, in particular 10 to 90, and

[0161] R5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated.

[0162] In certain embodiments, the Cm-alkyl of the moiety (Cm-alkyl)-R1is linear.

[0163] In certain embodiments, the compound is of the general formula 1

[0164] (1), wherein each X1is independently from any other X1selected from (Cm-alkyl)-R1, wherein

[0165] ■ m is an integer from 0 and 20; in particular m is an integer from 0 to 6, more particularly m is an integer from 0 to 4 and R1is selected from wherein o A is selected from -SCF2, -OCF2.-NH-, -N(CH3)-, S- or -O- and R2is - CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3 or -(CH2)P- phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 o B is selected from F, SCF3, OCF3, CF3, SCF2-R4, OCF2-R4, CF2-R4, wherein R4is selected from (CH2)q-CH3, in particular from F, SCF3, OCF3, or CF3, more particularly B is F, and each X2is independently from any other X2selected from Ci-20-alkyl, particularly C1-10- alkyl, more particularly Ci-3-alkyl; n is an integer from 1 and 500, in particular 100 to 500, and

[0166] R5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated.

[0167] In certain embodiments, the compound is of the general formula 1

[0168] (1), wherein each X1is independently from any other X1selected from (Cm-alkyl)-R1, wherein

[0169] ■ m is an integer from 0 and 20; in particular m is an integer from 0 to 6, more particularly m is an integer from 0 to 4 and o A is selected from -SCF2, -OCF2.-NH-, -N(CH3)-, S- or -O- and R2is - CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3 or -(CH2)P- phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 o B is selected from F, SCF3, OCF3, CF3, SCF2-R4, OCF2-R4, CF2-R4, wherein R4is selected from (CH2)q-CH3, in particular from F, SCF3, OCF3, or CF3, more particularly B is F, and each X2is independently from any other X2selected from Ci-20-alkyl, particularly C1-10- alkyl, more particularly Ci-3-alkyl; n is an integer from 1 and 100, in particular 10 to 90, and

[0170] R5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated.

[0171] Any embodiments discussed under the first aspect of the invention is also an embodiment for the second aspect of the invention.

[0172] A third aspect of the invention relates to the use of a compound as described in the first aspect of the invention in an optical tunable device.

[0173] The optical tunable device is explained below with reference to the enclosed drawing.

[0174] Description of the Figures

[0175] Fig. 1 shows a plan view of a first membrane attached to a first holding member;

[0176] Fig. 2 shows cross sectional views of lens according to the invention having a first wall in the form of a bellows;

[0177] Fig. 3 shows a cross sectional view of a prism according to the invention having a second wall in the form of membrane;

[0178] Fig. 4 shows a cross sectional view of a simplest prism according to the invention having two walls in form of membranes;

[0179] Fig. 5 shows a cross sectional view of a tunable prism according to the invention having a first wall in the form of a membrane in a neutral (A) and active position (B);

[0180] Fig. 6 shows the swelling of the Phenylmonofluoride at 85 °C

[0181] Fig. 7 shows the evaporation of the Phenylmonofluoride at 85 °C

[0182] References:

[0183] 1 Lens

[0184] 10 Membrane

[0185] 10b inner side of the membrane 10 10c Optically active and elastically expandable region of the membrane 10

[0186] 11 Circular holding member

[0187] 11a Circumferential inner edge of the holding member 11

[0188] 12 Outermost edge of the membrane 10

[0189] 20 Optical element

[0190] 30 Circumferential first wall

[0191] 31 Circumferential and partially flexible region

[0192] 32 Crease

[0193] 33 Circumferential edge region of the wall 30

[0194] 34 First section of the wall 30

[0195] 35 Opposing section of the wall 30

[0196] 36 Circumferential second lover edge region of the wall 30

[0197] 40 Actuator means

[0198] A Optical axis

[0199] D direction

[0200] F fluid

[0201] H height

[0202] V volume

[0203] 1a Prism

[0204] 2a Container

[0205] 3a Transparent optical fluid

[0206] 4a Wall member

[0207] 5a Planar bottom portion

[0208] 6a Elastic membrane

[0209] 60a Circumferential portion of the membrane 6a

[0210] 60b Elastic membrane

[0211] 7a Enclosed volume

[0212] 8a Glass window 80a Outer edge of the window 8a

[0213] 20a Elastically expandable membrane portion

[0214] 30a Refractive index

[0215] 100a Incident light

[0216] 200a Optical axis

[0217] 201a x-axis

[0218] 202a y-axis

[0219] 203a z-axis

[0220] 204a Tilt angle

[0221] 205a Deflection angle

[0222] 300a actuation force

[0223] Figure 2 shows in conjunction with Fig. 1 an embodiment of a tunable lens 1 suitable for the present invention. The lens 1 comprises a transparent and elastically expandable first membrane 10 as shown in Fig. 1. The first membrane 10 can be made of a glass, a polymer, an elastomer, a plastic or any other transparent and elastically expandable material. The first membrane 10 is attached via an outermost edge region 12 of the first membrane 10 to a circular first holding member 11 such that the membrane 10 is preferably in a pretensioned state. The circular first holding member 11 actually delimits an optically active and elastically expandable circular region 10c of the first membrane 10 which region 10c extends up to a circumferential inner edge 11a of the first holding member 11. As an alternative, said region 10c may also have a rectangular shape in case a correspondingly shaped first holding member 11 is used as shown in Fig 3. Such a first holding member 11 may comprise two separate parallel members or may be formed as a rectangular frame having to parallel legs shaping the lens.

[0224] This results in a cylindrical lens 1 instead of a spherical lens 1. However, any other shape of said region 10c is also possible by choosing the geometry of the first holding member 11 accordingly.

[0225] The lens 1 further comprises a first optical element 20 opposing the first membrane 10, wherein said first optical element 20 is an e.g., plate-like rigid element that extends along an extension plane being oriented perpendicular to an optical axis A of the lens 1 . The first optical element 20 can be transparent. Particularly, the first optical element may be formed out of or comprises a glass, and can be formed as an (e.g., glass) window, a lens, a micro structured element with refractive, diffractive or reflective structures. The first optical element 20 can further be made of plastic, a polymer or a metal. It may further comprise a reflection or antireflection coating.

[0226] The first membrane 10 and the first optical element 20 face each other along said optical axis A, wherein these two components are connected to each other via a circumferential first wall 30, which is connected to said first holding member 11 via a first upper circumferential edge region 33 of the first wall 30, and which is connected to the first optical element 20 via a circumferential second lower edge region 36 of the first wall 30, which second edge region 36 opposes the first edge region 33. Thus, the first wall 30 protrudes from the first optical element 20 along a first direction D which may run parallel to the optical axis A towards the first holding member 11.

[0227] The first membrane 10, the first optical element 20, and said first wall 30 are connected such that they delimit a first volume V of the lens 1 which is filled with a first fluid F such that said first fluid F fills the first volume V completely and particularly presses against an inner side 10b of the first membrane 10 facing the first optical element 20.

[0228] Now, in order to adjust a curvature of the membrane 10, e.g., of said region 10c, for adjusting the focal length of the lens 1 and / or so as to adjust the spatial position of the first membrane 10 with respect to the first optical element 20, the first wall 30 is designed to be adjustable in height H along said first direction D with respect to said first optical element 20, so as to adjust the pressure of the first fluid F residing inside the first volume V. Here, the height H of the first wall 30 may be adjusted such that the pressure of the first fluid F changes which leads to a corresponding change of the curvature of the first membrane 10 of the lens 1 due to the constant volume of the fluid F.

[0229] Specifically, when said height H of the first wall 30 is decreased overall, which would correspond to a reduction of the volume V of the lens 1 , the first fluid F presses due to its incompressibility against the elastically deformable region 10c of the first membrane 10, thus increasing the curvature of this region 10c. At the same time said region 10c of the first membrane 10 expands elastically.

[0230] Further, when said height H is increased overall, the pressure of the first fluid F decreases causing said region 10c of the first membrane 10 to contract and said curvature of said region 10c of the first membrane 10 to decrease.

[0231] However, the height H of the first wall 30 may also be changed asymmetrically with respect to axis A in a way that the pressure of the fluid F remains constant or is the same after adjusting the height H. Then, merely the spatial position of said first membrane 10 or said region 10c of the first membrane 10 is changed. However, an asymmetrical height adjustment may also lead to an altered pressure of the first fluid F and a corresponding change in curvature of said region 10c of the first membrane 10.

[0232] Specifically, the height H 1 of a first section 34 of the first wall 30 may be higher than the height H2 of an opposing section 35 of the first wall 30 leading to a tilted orientation of said region 10c of the first membrane 10 with respect to said optical axis A or the first optical element 20.

[0233] Preferably, the first wall 30 as indicated in Fig. 2 comprises a bellows or is formed as a bellows. Such a bellows 30 comprises a plurality of e.g., circumferential and particularly flexible regions 31 , wherein particularly each two adjacent regions 31 are connected to each other via an (e.g., circumferential) crease 32, such that when said height H of the first wall 30 is decreased said adjacent regions 31 are folded towards each other and when said height H of the first wall 30 is increased said adjacent regions 31 are folded away from each other. Thus, concerning its cross section, the first wall or bellows 30 preferably comprises a zig-zag pattern. The creases 32 of the bellows 30 may be reinforced by means of rigid elongated members that may follow the course of an associated crease 32.

[0234] Preferably, said creases 32 extend along or parallel to the extension plane of the first optical element 20 (i.e. , in a peripheral direction of the first wall / bellows 30) or perpendicular to said first direction D.

[0235] Due to the bellows structure, the first wall 30 deforms easier in said first direction D along which the first wall 30 comprises said adjustable height H than in a second direction D’ running perpendicular to said first direction D.

[0236] In order to adjust the height H of the first wall 30 either locally or in an overall fashion, the lens 1 comprises an actuator means 40 which is coupled to the first wall 30 so as to adjust its height H along said direction D.

[0237] Preferably, said actuator means 40 is designed to exert a force on the first wall 30 so as to adjust the height H of the first wall 30, wherein particularly said actuator means 40 is coupled to said first holding member 11 , so that the point of application of said force lies outside said region 10c of the first membrane 10. Thus, when the actuator means pushes on the first holding member 11 counter to the first direction D said regions 32 of the bellows 30 approach each other and the height of the first wall 30 decreases. On the other hand, when the actuator means 40 moves the first holding member 11 in the first direction D away from the first optical element 20, the regions 31 of the bellows 30 are folded / pivoted away from their respective adjacent regions 31 and the height H of the first wall 30 increases correspondingly. Particularly, the actuator means 40 may be connected to the first optical element 20 so as to be able to move the first holding member 11 with respect to the first optical element 20. Particularly, said actuator means 40 does not push a structure against said region 10c of the first membrane 10. Therefore, the whole region 10c of the first membrane 10 can in principle be used for influencing a light path which allows one to increase the ration between the clear aperture and the outer diameter of the lens 1.

[0238] Further, the first wall 30, e.g., in the form of a bellows 30, may be also adjustable in a lateral direction (i.e., the second direction D'). Such a shearing movement of the first wall 30 may be used for the purpose of image stabilization, i.e., in order to compensate for a movement of the lens 1 in a plane running perpendicular to the optical axis A. Here, the actuator means 40 is also preferably coupled to the first holding member 11 and designed to displace said first holding member 11 along said second direction D'.

[0239] Fig. 3 shows a schematic cross-sectional view of the tunable prism. Fig. 3 shows a basic embodiment of a tunable prism 1a is shown in a cross-sectional view and the basic working principle is demonstrated. The tunable prism 1a comprises a container 2a filled with a transparent optical fluid 3a. The container 2a has a planar bottom portion 5a consisting of glass. The bottom portion 10a is arranged such that it faces towards the side of incident light 100a. Furthermore, a wall member 4a delimits the container 2a laterally with respect to the optical axis 200a. The wall member 4a is integrally formed with the bottom portion 5a. The optical axis 200a (broken lines) of the tunable prism 1 extends orthogonally and centrally through the bottom portion 5a along the z-axis 203a.

[0240] The container 2a furthermore comprises an elastic membrane 6a arranged opposite the bottom portion 5a of the container 2a. The elastic membrane 6a is repeatedly elastically expandable and stretchable. In its resting state, the elastic membrane 6a extends under lateral tension parallel to the bottom portion 5a. This tension provides a restoring force to the membrane 6 to return in its resting state, when no actuation force is applied.

[0241] The membrane 6a is sealed to the wall member 4a of the container 2a at its edges such that the fluid 3a cannot escape the volume 7a enclosed by the wall member 6a, the bottom portion 5a and the membrane 6a.

[0242] On top of the membrane 6a facing away from the volume 7a, a glass window 8a is attached to the membrane 6a. In the resting state of the membrane 6a, the glass window 8a is extends parallel to the bottom portion 5a.

[0243] Between an outer edge 80a of the glass window 8a and the wall member 4a a circumferential portion 60a of the membrane 6a is not covered by the glass window 8a. This portion is referred to as the elastically expandable portion 60a. In the resting state, incident light 100a traverses the tunable prism 1a from the bottom portion 5a through the volume 7a to the window 8a without being deflected from the optical axis 200 as indicated by the arrows 100a, 101a.

[0244] When an actuation force 300a is applied to the outer edge 80a of the window 8a, the window 8a tilts around at least one axis, referred to as the first axis 201a, e.g., the x-axis. The window 8a can also be tilted around a second axis 202a, e.g., the y-axis that is particularly orthogonal to the first axis 201a and - like the first axis 201a - extends 10a within the plane of extension of the window 8a.

[0245] When the actuation force 300a is applied to the window 8a, the window 8a experiences a tilting motion around the first and / or second axis 201a, 202a.

[0246] In the tilted state, the window 8a is not extending parallel to the bottom portion 5a but encloses a tilt angle 204a with the bottom portion 5a and the optical axis 200a; a first section of the outer edge 80a of the glass window 8a is closer to the bottom portion 5a, while another section of the outer edge 80a located opposite the first section is located further away from the bottom portion 5a.

[0247] The elastically expandable membrane portion 60a around the outer edge 80a of the window 8a is stretched correspondingly. As the membrane 6a is elastic, particularly the 20a elastically expandable membrane portion 60a conveys a restoring force to the tilted window 8a.

[0248] In the tilted state of the tunable prism 1a, traversing light 100, 101 exits the prism 1a at an angle 205 with respect to the optical axis 200. This is indicated by the arrows 100, 101 pointing into and outwards the tunable prism 1a.

[0249] By adjusting the actuation force 300a on the window 8a, the tilt angle 204a of the window 8a can be adjusted, which translates to an adjusted deflection angle 205a of the exiting light 101a.

[0250] The relationship between the mechanical tilt angle 204a of the window 8a and the resulting deflection angle 205a of the light depends on the refractive index of the 30a optical fluid 3a, particularly the liquid. The higher the refractive index of the liquid 3a, the stronger the resulting light deflection.

[0251] On the other hand, a low-refractive index liquid usually exhibits less dispersion than a high- refractive index liquid. Therefore, when chromatic aberrations should be avoided, a low- refractive index liquid can be used. Thus, particularly in polychromatic applications like imaging, a low-refractive index liquid is suitable. The refractive index of a low-refractive index liquid is for example around 1 .33.

[0252] A high-refractive index liquid in turn is suitable for monochromatic applications such as iris detection. The refractive index of a high-refractive index liquid is for example around 1.56. In Fig. 4 an embodiment of the tunable prism 1a is shown that comprises a minimum number of components and that is particularly well suited for cost efficient production. The container 2a consists of only the transparent bottom portion 5a, the glass window 8a and two deformable, particularly elastic membranes 6a, 60a, 60b that are sealed with each other in order to form the closed container volume comprising the liquid 3a. This embodiment forms a bellows. Such a double-membrane bellows-container 2a further minimizes the required actuation force for tilting the window 8a around the first or second axis and on the other hand maximizes the ratio between clear aperture 90a and outer diameter of the window 8a.

[0253] Any previously introduced actuation concept (VCM with air-coils or embedded PCB-coils, SMA, Reluctance motor) and prism-shaping device type can be applied.

[0254] In Fig. 5 another embodiment of the tunable prism 1a is shown. This embodiment comprises only one membrane 6a that is sealed to the bottom portion 5a. The edges of the bottom portion 5a, where the membrane 6a is sealed to, can also be understood as wall members 4a.

[0255] In the left panel of Fig. 5 the neutral position (light passes through the prism 1a without being deflected) with a non-tilted window 8a is shown, wherein on the right panel of Fig. 5 the window 8a is tilted with respect to the bottom portion 5a, such that light is deflected when passing through the prism 1a.

[0256] The container 2a comprises the liquid 3a. The membrane 6a is deformable but not necessary elastic.

[0257] The container 2a acts like a bellows when the prism-shaping device is actuated (not shown).

[0258] Such a bellows-container 2a would require less actuation force and maximize the ratio between clear aperture 90a and outer diameter because the membrane 6a is mainly 10a deformed in axial direction, i.e. , parallel to the optical axis and not in radial direction.

[0259] Fig. 6 shows the swelling of monofluorophenyl siloxane (OL2431). After 120 days, the swelling at 85 °C is < +1.5%. Overall, is the density of the polymer 1.2, while having a transmission of 90.27% and a refraction index of 1.5138 at 20°C at 589.3 nm.

[0260] Fig. 7 shows the evaporation of monofluorophenyl siloxane (OL2431). After 120 days, the evaporation at 85 °C is < -0.2%. Overall, is the density of the polymer 1.2, while having a transmission of 90.27% and a refraction index of 1.5138 at 20°C at 589.3 nm.

[0261] Examples

[0262] An example of preparation of the siloxane based compound is as follows. Other compounds can be produced analogously.

[0263] Starting Materials: The precursor materials can be obtained such as 1-(4-Bromobutyl)-4- fluorobenzene(C Hi2BrF) CAS Number: 89326-70-5 or trichloromethylsilane (CHsSiC ) Cas Number: 109-99-9.

[0264] Preparation of the Grignard reagent

[0265] C6H4F-(CH2)4Br + Mg C6H4F-(CH2)4MgBr

[0266] In a dry, inert atmosphere, dissolve of 1-(4-Bromobutyl)-4-fluorobenzene in anhydrous tetra hydrofuran (THF). Add a solution of magnesium turnings in THF dropwise to the bromobutyl fluorobenzene solution. Stir and reflux the reaction mixture for a couple hours to to ensure complete formation of the Grignard reagent (C Hi2BrFMg).

[0267] Synthesis of the Monomer

[0268] Add the resulting Grignard compound to an ice-cold solution of methyltrichlorosilane in diethylether over 4 hours, with vigorous stirring. (Grignard compound:methyltrichlorosilane = 1 :2 weight ratio). Separate the excess magnesium salts by filtration. Remove excess methyltrichlorosilane and the Grignard reagent by distillation under vacuum using a short-path apparatus to obtain pure 4-fluorophenylbutyldichlorosilane (C Hi2BrFMg).

[0269] Scheme 1. Preparation of Grignard Reagent and Synthesis of the Monomer

[0270] Hydrolysis of the Monomer to Oligomers:

[0271] Place saturated sodium carbonate solution in a flask. Add the ether solution of the dichlorosilane monomer dropwise with constant stirring. Continue the hydrolysis for 30 minutes to allow the silanols to undergo condensation and form oligomers. Extract the oligomers with diethylether and neutralize with dilute HCI. Dry the resulting siloxane oligomers with anhydrous MgSO4. Polymerization of the Oligomers

[0272] Place silanol-terminated 4-fluorophenylbutylsiloxane oligomers in flask and heat under vacuum. Add potassium carbonate (at a 5:100 weight ratio). Monitor the increase in viscosity inside the reaction and allow the reaction to proceed until the rotation of the stirring bar is impeded due to the increased viscosity. Bring the materials to room temperature and neutralize with 0.2 M HCI. Extract the reaction products with diethyl ether, and dry by precipitation in methanol. Finally dry under vacuum at 90°C fort to remove traces of solvent.

[0273] Scheme 2. Hydrolysis and subsequent Polymerization of Oligomers

[0274] The other examples can be produced in an analogue way.

Claims

Claims1 . An optical tunable device, wherein the optical tunable device comprises a membrane, delimiting at least partially a volume, wherein the volume is filled with a liquid comprising at least one siloxane based polymer compound comprising n repeating units and comprising at least one moiety X in a repeating unit UX, wherein X is selected from (Cm-alkyl)-R1, wherein■ m is an integer from 0 and 20; ando A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 1 and 500.

2. An optical tunable device according to claim 1 , wherein the optical tunable device comprises a membrane, delimiting at least partially a volume, wherein the volume is filled with a liquid comprising at least one siloxane based polymer compound comprising n repeating units and comprising at least one moiety X in a repeating unit UX, wherein X is selected from (Cm-alkyl)-R1, wherein■ m is an integer from 0 and 20; ando A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6,n is an integer from 1 and 100, in particular 10 to 90.

3. The optical tunable device according to claim 1 , wherein the optical tunable device comprises a membrane, delimiting at least partially a volume, wherein the volume is filled with a liquid comprising at least one siloxane based polymer compound comprising n repeating units and comprising at least one moiety X in a repeating unit UX, wherein X is selected from (Cm-alkyl)-R1, wherein■ m is an integer from 0 and 20; ando A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 100 and 500.

4. The optical tunable device according according to any of the preceding claims, wherein the polymer compound is a polymer with only one type of repeating units UX or a copolymer with repeating units UX and at least one further repeating unit FU, wherein the ratio of UX to FX is higher than 1 : 100, in particular higher than 25 : 100, more particularly higher than 50 : 100, more particularly higher than 75 : 100.

5. The optical tunable device according according to any of the preceding claims, wherein the polymer compound is a polymer with only one type of repeating unit UX.

6. The optical tunable device according according to any of the preceding claims, wherein the at least one siloxane based polymer compound is of a general formula 1 ,(1), wherein each X1is independently from any other X1selected from (Cm-alkyl)-R1, wherein■ m is an integer from 0 and 20; and■ R1is selected from, wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, each X2is independently from any other X2selected from (Cm-alkyl)-R1or Ci-20-alkyl , wherein■ m is an integer from 0 and 20; and■ R1is selected from, wherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 1 to 100, in particular 10 to 90, andR5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated.

7. The optical tunable device according according to any of the previous claims, wherein the at least one siloxane based polymer compound is of a general formula 1 ,(1), whereineach X1is independently from any other X1selected from (Cm-alkyl)-R1, wherein■ m is an integer from 0 and 20; and■ R1is selected fromwherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, each X2is independently from any other X2selected from (Cm-alkyl)-R1or Ci-20-alkyl , wherein m is an integer from 0 and 20; andR1is selected fromwherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, n is an integer from 100 to 500, andR5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated.

8. The optical tunable device according according to any of the preceding claims, wherein the at least one siloxane based polymer compound is of a general formula 1 ,(1), whereinX1is selected from (Cm-alkyl)-R1, wherein■ m is an integer from 0 and 20; and■ R1is selected fromwherein o A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, andX2is selected from Ci-20-alkyl, particularly Ci-10-alkyl, more particularly Ci-6-alkyl; n is an integer from 1 to 100, in particular 10 to 90, andR5is selected from Ci-6-alkyl, particularly Ci-3-alkyl, more particularly Ci-alkyl, which can be partially or completely fluorinated.

9. The optical tunable device according according to any of the preceding claims, wherein the at least one siloxane based polymer compound is of a general formula 1 ,(1), whereinX1is selected from (Cm-alkyl)-R1, wherein■ m is an integer from 0 and 20; and■ R1is selected fromwhereino A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)P-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 , o B is selected from -F, -SCF3, -OCF3, -CF3, -SCF2-R4, -OCF2R4, -CF2R4, wherein R4is selected from (CH2)q-CH3 or (CH2)q-phenyl, wherein o is an integer from 1 to 5, and wherein q is an integer from 0 to 6, andX2is selected from Ci-20-alkyl, particularly Ci-10-alkyl, more particularly Ci-3-alkyl; n is an integer from 100 to 500, andR5is selected from Ci-6-alkyl, particularly Ci-3-alkyl, more particularly Ci-alkyl, which can be partially or completely fluorinated.

10. The optical tunable device according to any of the previous claims, wherein R1is selected from11 . The optical tunable device according to any of the previous claims, wherein R1is12. The optical tunable device according to any of the previous claims, wherein A is selected from -SCF2-, -OCF2-, -NH-, -N(CH3)-, S- or -O- and R2is selected from -CF3 or -CF2-R3, and wherein R3is selected from -(CH2)P-CH3.

13. The optical tunable device according to any one of the previous claims, wherein A is selected from - -NH-, -N(CH3)-, or -O-, particularly -O-.

14. The optical tunable device according to any one of the previous claims, wherein B is selected from F, SCF3, OCF3, CF3, SCF2-R4, OCF2-R4, CF2-R4, wherein R4is selected from (CH2)q-CH3, in particular from F, SCF3, OCF3, or CF3, more particularly B is F.

15. The optical tunable device according to any one of the previous claims, wherein o is an integer from 1 to 5.

16. The optical tunable device according to any one of the previous claims, wherein o is an integer from 2 to 5, particularly from 3 to 5.

17. The optical tunable device according to any one of the previous claims, wherein o is an integer from 4 to 5, particularly o is 5.

18. The optical tunable device according to any one of the previous claims, wherein q is an integer from 0 to 20, particularly an integer from 0 to 12, more particularly 0 to 619. The optical tunable device according to any one of the previous claims, wherein m is an integer from 0 to 12, particularly 0 to 6.

20. The optical tunable device according to any of the previous claims, wherein m is an integer from 0 to 4.21 . The optical tunable device according to any of the previous claims, wherein m is 0 and o is 1.

22. The optical tunable device according to any of the previous claims, wherein m is an integer from 2 to 4 and o is 5.

23. A compound of the general formula 1(1), wherein each X1is independently from any other X1selected from (Cm-alkyl)-R1, wherein■ m is an integer from 0 and 20; in particular m is an integer from 0 to 6, more particularly m is an integer from 0 to 4 ando A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 o B is selected from F, SCF3, OCF3, CF3, SCF2-R4, OCF2-R4, CF2-R4, wherein R4is selected from (CH2)q-CH3, in particular from F, SCF3, OCF3, or CF3, more particularly B is F, and each X2is independently from any other X2selected from Ci-20-alkyl, particularly C1-10- alkyl, more particularly Ci-3-alkyl; n is an integer from 1 and 500, in particular 100 to 500, andR5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated.

4. A compound of the general formula 1(1), wherein each X1is independently from any other X1selected from (Cm-alkyl)-R1, wherein■ m is an integer from 0 and 20; in particular m is an integer from 0 to 6, more particularly m is an integer from 0 to 4 ando A is selected from -SCF2-, -OCF2-, -NH-, -N(R6)-, S- or -O- and R2is selected from CF3 or CF2R3, and wherein R3and R6are selected independently from each other from -(CH2)P-CH3 or -(CH2)p-phenyl, wherein p is an integer from 0 to 6, in particularly 0 to 3, more particularly 0 or 1 o B is selected from F, SCF3, OCF3, CF3, SCF2-R4, OCF2-R4, CF2-R4, wherein R4is selected from (CH2)q-CH3, in particular from F, SCF3, OCF3, or CF3, more particularly B is F, and each X2is independently from any other X2selected from Ci-20-alkyl, particularly C1-10- alkyl, more particularly Ci-3-alkyl; n is an integer from 1 and 100, in particular 10 to 90 andR5is selected from Ci-6-Alkyl, particularly Ci-3-Alkyl, more particularly Ci-Alkyl, which can be partially or completely fluorinated.