US-12625363-B2 - Thermal expansion compensation in tunable lenses

US12625363B2US 12625363 B2US12625363 B2US 12625363B2US-12625363-B2

Abstract

The present invention relates to a method and to means for compensating thermal expansion in a tuneable lens. In particular, the present invention a tuneable lens comprising means for compensating thermal expansion and an apparatus, such as a camera module comprising a tunable lens comprising means for compensating thermal expansion.

Inventors

Pierre Craen
Janne Tapani Kilpinen

Assignees

POLIGHT ASA

Dates

Publication Date: 20260512
Application Date: 20220329
Priority Date: 20210329

Claims (13)

1 . A tunable lens, comprising: a first and a second transparent membrane; a transparent, deformable, non-fluid body located in between said first and said second transparent membrane, wherein said transparent, deformable, non-fluid body comprises a first polymer; one or more actuators; and a second polymer located in between said first and said second transparent membranes, wherein said first and second polymers have a different Coefficient of Thermal expansion (CTE), thereby producing a first polymer layer and a second polymer layer, wherein said first polymer layer and said second polymer layer have a thickness gradient along a radius of said tunable lens.
2 . The tunable lens according to claim 1 , wherein said first polymer is a polymer network of cross-linked or partly cross-linked polymers comprising a miscible oil or combination of oils.
3 . The tunable lens according to claim 1 , wherein said second transparent membrane is a plano-convex membrane, thereby creating a thickness gradient along a radius of said tunable lens in said first polymer.
4 . The tunable lens according to claim 1 , wherein the second polymer is comprised in at least one coating located onto said first and/or said second transparent membrane.
5 . The tunable lens according to claim 4 , wherein said at least one coating is a film of an optical transparent material having a different CTE than the one of said first and said second transparent membranes.
6 . The tunable lens according to claim 1 , wherein at least one structure element located onto said first and/or said second membrane comprises the second polymer.
7 . The tunable lens according to claim 6 , wherein said at least one structure element is a pressing structure element.
8 . The tunable lens according to claim 6 , wherein said at least one structure element is a supporting structure element.
9 . The tunable lens according to claim 6 , wherein said at least one structure element has a stop function, thereby limiting the deformation of said first and/or said second transparent membrane.
10 . The tunable lens according to claim 1 , wherein said one or more actuators are piezoelectric actuators.
11 . The tunable lens according to claim 1 , wherein said one or more actuators are Voice Coil Motors (VCMs).
12 . The tunable lens according to claim 1 , wherein said one or more actuators are Shape Memory Alloy (SMA).
13 . A camera module (CM) comprising the tunable lens according to claim 1 .

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a U.S. National Phase Application of PCT International Application Number PCT/EP2022/058278, filed on Mar. 29, 2022, designating the United States of America and published in the English language, which is an International Application of and claims the benefit of priority to European Patent Application No. 21165466.0, filed on Mar. 29, 2021. The disclosures of the above-referenced applications are hereby expressly incorporated by reference in their entireties. FIELD OF THE INVENTION The present invention relates to a method and to means for compensating thermal expansion in a tuneable lens. In particular, the present invention relates to a tuneable lens comprising means for compensating thermal expansion and an apparatus, such as a camera module, comprising a tunable lens comprising means for compensating thermal expansion. BACKGROUND OF THE INVENTION Tunable lens performances are influenced by thermal induced effects. For example, focus drift in optical system due to temperature variation is well known and it restricts the specific temperature range in which a device can be optimally used. In that, there is a need for solutions compensating the effects of temperature drift. In general, due to different coefficient of thermal expansion (CTE) of the materials used in the different elements of the tunable lens structure, deformation of the optical portion of the tunable lens may occur. For example, the presence of support or pressing structure having a higher CTE of the below membrane may cause substantial displacement of the Z component of the field when temperature changes between 25° C. and 60° C. Furthermore, tunable lens employing polymer based lens body may be further influenced by thermal induced expansion. Due to the different CTE of the polymer lens body, the distance between membranes or between the membrane and the substrate underneath may increase when temperature increases. As a consequence, the optical path may be changed and the actuator interface position may differ, influencing the optical performance of the tuneable lens. Moreover, index of refraction of the polymer based lens body may also change over temperature, introducing further optical performances shift. In that, several parameters may contribute to thermal induced variation and there is a need for systems and methods for compensating effects due to optical variation induced by thermal expansion within tuneable lenses. Hence, a tunable lens being able to compensate for thermal defocus would be advantageous. OBJECT OF THE INVENTION An object of the present invention is to provide a tunable lens being able to compensate for thermal defocus. An object of the present invention may also be seen as to provide an alternative to the prior art. In particular, it may be seen as an object of the present invention to provide a tunable lens being able to compensate for thermal defocus that solves the above-mentioned problems of the prior art by employing means for compensating thermal expansion of the tunable lens. SUMMARY OF THE INVENTION Thus, the above-described object and several other objects are intended to be obtained in a first aspect of the invention by providing a tunable or controllable lens, comprising: a first and a second transparent membrane; a transparent, deformable, non-fluid body located, such as sandwiched, in between the first and the second transparent membrane; one or more actuators; and means for compensating thermal expansion of the tunable lens. The tunable or controllable lens is a lens having a variable optical power. The first and a second transparent membrane are cover members that can be transparent to VIS light, i.e. have a determined transmittance within the visible (VIS) light spectral range making the lens suitable for being used in a camera module. The transparent deformable, non-fluid lens body is preferably made from an elastic material. Since the lens body is non-fluid, no fluid-tight enclosure is needed to encapsulate the lens body to prevent a leakage therefrom. In some embodiments, the tunable lens may comprise a support wall. The support wall may be arranged to support the first transparent membrane and/or the second transparent membrane. When the support wall is present, the lens comprises a gap, such as an air gap, between a potential support wall and the transparent, deformable, non-fluid body. The motion of the non-fluid body is therefore unrestrained radially relative to the optical axis, i.e. along directions perpendicular to the optical axis. In some embodiments, the transparent, deformable, non-fluid body comprises a first polymer. The first polymer may be a polymer network of cross-linked or partly cross-linked polymers comprising a miscible oil or combination of oils. In some embodiments, the transparent, deformable, non-fluid body is made from a soft polymer, which may include a number of different materials, such as silicone, polymer