DK202170033A1

DK202170033A1 - Improving impact robustness of a variable lens

Info

Publication number: DK202170033A1
Application number: DKPA202170033A
Authority: DK
Inventors: Henriksen Lars
Original assignee: Polight Asa
Priority date: 2021-01-27
Filing date: 2021-01-27
Publication date: 2021-01-28

Abstract

The invention relates to a controllable lens which comprises a transparent or reflective first cover member, a transparent second cover member, a transparent, deformable, non-fluid body sandwiched between the first and second cover members, an actuator system arranged to generate a controllable bending of the first cover member, a support structure arranged so that it at least partially surrounds the non-fluid body and the second cover member and wherein the support structure provides a radial gap between support structure and the nonfluid body and the second cover member so that the second cover member is able to displace radially towards the support structure, and protective means such as a shock absorbing material arranged between the second cover member and the support structure to reduce shock impacts between an outer edge of the second cover member and the support structure.

Description

DK 2021 70033 A1 1

IMPROVING IMPACT ROBUSTNESS OF A VARIABLE LENS

FIELD OF THE INVENTION The invention relates to optical devices with variable optical power or variable beam deflection, particularly to methods for achieving impact robust designs.

BACKGROUND OF THE INVENTION Variable lenses having an adjustable focal length are used in compact cameras such as compact cameras used in smart phones. One type of such variable lenses comprises a non-fluid body sandwiched between two membranes of which at least one is bendable. While such lenses have shown to provide several advantages, improvements are still needed and therefore the inventors have devised this invention.

SUMMARY It is an object of the invention to improve optical assemblies such as variable lenses for use in optical imaging systems, particularly imaging systems for compact cameras. Such improvements may relate to manufacturing methods for achieving improved robustness of the optical assembly and the lens.

In a first aspect of the invention there is provided a controllable optical assembly with a variable optical power and/or a variable beam deflection, the optical assembly comprises - a transparent or reflective first cover member, -a transparent second cover member, - a transparent, deformable, non-fluid body sandwiched between the first and second cover members, so that the first and second cover members and the non- fluid body constitute a lens with an optical axis intersecting the non-fluid body and the first and/or the second cover members, - an actuator system arranged to generate a controllable bending of the first cover member, - a support structure arranged to support the first cover member and arranged so that it at least partially surrounds the non-fluid body and the second cover member, and wherein the support structure provides a radial gap between support structure and the non-fluid body and the second cover member so that

DK 2021 70033 A1 2 the second cover member is able to displace radially towards the support structure, - protective means comprising one or more of: a) a shock impact absorbing material arranged between the second cover member and the support structure to reduce shock impacts between an outer edge of the second cover member and the support structure, b) a reinforcement of the outer edge of the second cover member, or c) an elastic connection arranged between the second cover member and the support structure to restrain the radial displacement of the second cover member.

Advantageously, the protective means leads to an improved design of the optical assembly which at least provides improved robustness of one or more components of the optical assembly such as the second cover member or the support structure.

Embodiments of the invention are provided in the description and the claims. A second aspect of the invention relates to a method for improving robustness of a transparent cover member of a controllable optical assembly.

In general, the various aspects and embodiments of the invention may be combined and coupled in any way possible within the scope of the invention. These and other aspects, features and/or advantages of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will be described, by way of example only, with reference to the drawings, in which Fig. 1 shows shows an example of an optical assembly such as a variable lens, Figs. 2A-2D, 3 and 4 shows different examples for protective means for achieving improved robustness, Fig. 5 shows a process for manufacturing cover members provided soft protective material, and

DK 2021 70033 A1 3 Fig. 6 shows a camera module comprising the controllable optical assembly.

DETAILED DESCRIPTION Fig. 1 shows a controllable optical assembly 199 such as a controllable lens having a variable optical power and/or a variable beam deflection. The upper illustration is a top view, and the two lower illustrations are side views showing the lens in two different actuation states. The lens comprises a first cover member 111 and a second cover member 112. In an embodiment, the first and second cover members are transparent. Alternatively, one of the first and second cover members is reflective such as the first cover member 111, e.g. provided with a reflective metal layer to provide full or partial reflection so that the incident light beams are reflected back to the opposite transparent cover member.

The lens 100 further comprises a transparent, deformable, non-fluid body 105 sandwiched between the first and second cover members, so that the first and second cover members and non-fluid body constitute the lens having an optical axis 150 intersecting the first and second cover members and the non-fluid body. The non-fluid body 105 abuts the inwardly facing surfaces of the first and second cover members 111, 112.

The optical axis 150 may be defined as the axis which passes through centers of the first and second cover members 111, 112 and the non-fluid body 105 and which is normal to a plane of one of the cover members. The optical axis is further defined according to conventional optical definitions.

An actuator system 120 is arranged to generate a controllable bending and/or tilt of the first cover member 111. The change of the overall outer shape of the lens can be controlled, e.g. according to values in a look-up table.

At least one of the first and second cover members 111, 112 are configured to be bent by forces or torques provided by the actuator system 120. It is understood that the forces in general comprises forces distributed over an area, e.g. due to stresses generated by strains generated by surface mounted piezo elements.

The lens comprises a support structure 130 arranged to support the first cover member 111. In this example, the first cover member 111 is supported by the

DK 2021 70033 A1 4 support structure 130, e.g. fixed to the support structure, while the second support member 112 is not in contact with the support structure 130, but connected to the non-fluid body 105.

The transparent deformable, non-fluid lens body 105 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. As illustrated, the lens 100 comprises a gap 183 between the support structure 130 and the non-fluid body 105. The motion of the non-fluid body 105 is therefore unrestrained radially relative to the optical axis 150, i.e. along directions perpendicular to the optical axis. In a preferred embodiment, the lens body is made from a soft polymer, which may include a number of different materials, such as silicone, polymer gels, a polymer network of cross-linked or partly cross- linked polymers, and a miscible oil or combination of oils. The elastic modulus of the non-fluid lens body may be larger than 300 Pa, thereby avoiding deformation due to gravitational forces in normal operation. The refractive index of the non- fluid lens body may be larger than 1.3. The non-fluid body 205 may have a refractive index which is equal, substantially equal or close to the refractive index of the first and second cover members 111, 112 in order to reduce reflections at the boundaries of the non-fluid body 105.

Due to the elasticity of the non-fluid body, the second cover member 112 can displace laterally or radially, e.g. in a radial direction 181 perpendicular or substantially perpendicular to the optical axis 150. The lateral displacement may be caused by external forces exerted to the optical assembly 199, e.g. due to high accelerations of the optical assembly 199 such as high accelerations caused by inappropriate use of the optical assembly 199.

The cover members 111, 112 are generally slab-shaped and may have curved such as a pre-shaped, e.g. spherically pre-shaped, or plane surfaces or a combination thereof. The cover members 111, 112 may be made from a large number of different materials, such as acrylics, polyolefins, polyesters, silicones, polyurethanes, glass and others. At least the one of the first and second cover members 111, 112 which is arranged to be deformed by the actuators, has a stiffness which is suitable to enable bending by actuation of the actuator system

DK 2021 70033 A1

120. In general, the material of the first and/or the second cover member 111, 112 may be formed in a material having a Young's modulus in the range between 5 MPa and 100 GPa to provide the necessary stiffness. For example, Young's modulus for borosilicate glass is 63 GPa, and 72 GPa for fused silica glass. 5 The bending of the first and/or second cover members 111, 112 is at least partly due to radially varying reaction forces from the lens body 105 which affects the Sag of at least the first cover member 111 and thus the optical power instead of just vertically compressing the lens body with no change in Sag. A full explanation ofthe effect of the lens body 105 on the curvature of the cover members is described in WO2019/002524A1 hereby incorporated by reference.

In the Fig. 1 example, the actuator system 120 may comprise one or more piezoelectric elements mounted on the surface of the first cover member 111. For example, the actuator system may be constituted by an annular ring shaped piezo attached on a surface of the first cover member 111 in order to provide bending of the first cover member. Instead of a ring shaped element, a plurality of piezo elements may be distributed along a circle around the optical axis 150.

Actuator systems 120 configured in other ways are also feasible. For example, linear displacement actuators may be located between the first and second cover members 111, 112 and connected with the inwardly pointing surfaces of the cover members 111, 112.

The actuator system is arranged so that the optical assembly 199 comprises an inner portion 182 which constitutes the transparent lens area, surrounded by the one or more actuators of the actuator system 120 so that light can pass unobstructed through the lens area. The non-fluid body 105 is arranged so that it covers at least the lens area, but may also extend beyond the extension of the lens area towards the perimeter of the first or second cover member 111, 112. The actuator system 120 may be configured to solely generate a controllable bending of the first or the second cover member 111,112. Thus, by the actuation, the first and/or second cover member can be bend into a concave or convex shape and thereby provide an optical power to light transmitted through the lens.

DK 2021 70033 A1 6 Alternatively, the one or more actuator system 120 may be arranged to displace and/or tilt the first cover member 111 relative to the second cover member 112. For example, the actuator system 120 may be arranged as explained above, between the cover members 111, 112, so that the relative angle between the two cover members can be changed, e.g. in order to change the direction of light transmitted through the optical assembly 199.

The support structure 130 may be configured as a rigid frame, e.g. manufactured from silicon, metal or plastic. The support structure may be arranged so that it at least partially surrounds the non-fluid body and the attached second cover member 112 and thereby provides a continuous support for the first cover member 111.

Furthermore, the controllable optical assembly 199 may be arranged with a radially extending gap 183 such as an air gap 183 between the perimeter of the non-fluid body 105 and the second cover member 112 on one side and the support structure 130 on the other side, i.e. a gap extending radially relative to the optical axis 150 and separating the perimeter of non-fluid body 105 in a radial direction from the support structure 130. Due to the gap, the non-fluid body is able to expand unconstrained in the radial direction in response to actuator actions. However, due to the gap, the second cover member is also able to be moved radially towards the inner surface of the support structure.

To reduce any unintended effects of an impact between the second cover member 112 and the support structure 130 due to a large lateral displacement of the second cover member 112 towards the support structure 130, Figures 2A-2D, 3 and 4 shows different protective means 201-204, 301, 401 to prevent or mitigate such unintended effects.

Fig. 2A shows application of protective means 201 which comprises a soft material applied so that is fills a part of the air gap 183. As shown the soft material, e.g. an adhesive such as an epoxy adhesive, may be applied in the corner where the first cover member 111 connects with the support structure 130. The adhesive may have properties so that it does not exhibit wetting with the non-fluid polymer

DK 2021 70033 A1 7 body 105, i.e. so that the soft material does not make a connection with the non- fluid body 105. The soft material should have stiffness which is low enough to prevent, or substantially prevent, interference with the bending of the first cover member

111. The soft material is applied so that it connects with the inner surface of the support structure 130 and extends along said inner surface at least to a location where the second cover member 112 would contact said inner surface if displaced laterally. The soft material should have a thickness in the radial direction 181 large enough to sufficiently reduce the impact forces, i.e. contact forces, from a collision between the second cover member 112 and the support structure.

The soft material may have a stiffness in the range from 10 to 200 MPa. Fig. 2B shows application of protective means 202 which comprises a soft material such as a soft coating applied, as illustrated, on surfaces of the support structure 130 and the inner surface of the first cover member 111, before the non-fluid body 105 is connected to the inner surface of the first cover member 111. This process such as a spraying or chemical vapor deposition process may be advantageous due to simplified manufacturing where the coating is applied over many items, i.e. partly manufactured assemblies 199, at the same time. However since the coating is applied over the inner portion 182 of the lens, the coating must be transparent and additionally have the same or substantially the same refractive index as the first cover member 111 and the non-fluid body 105. Possible coating materials comprise polymer, lacquer, parylene, and inorganic materials. Alternatively, the transparent inner portion 182 may be masked during the spraying or deposition process so that non-transparent coating materials may be used.

DK 2021 70033 A1 8 As in the Fig. 2A example, at the location where the second cover member 212 would contact said inner surface if displaced laterally, the coating material should have a thickness in the radial direction 181 large enough to sufficiently reduce the impact forces, i.e. contact forces, from a collision between the second cover member 112 and the support structure 130.

Fig. 2C shows application of protective means 203 which comprises a soft material such as a soft coating - similar to the protective means 202 in Fig. 2B. Here the soft material is applied on surfaces of the second cover member 112, before the non-fluid body 105 is connected to the inwardly pointing surface of the second cover member 112. The opposite side, i.e. the outwardly pointing surface, which may be AR coated, may be provided with a removable protective sheet such as a tape, during the process of coating the inwardly pointing surface of the second cover member 112.

Again, since the coating is applied over the inner portion 182 of the lens, the coating must be transparent and additionally have the same or substantially the same refractive index as the first cover member 111 and the non-fluid body 105; alternatively, the transparent inner portion 182 may be masked during the coating process. The thickness of the soft coating at the edges of the second cover member 212 facing the support structure 130 is selected to provide a stiffness low enough to sufficiently reduce the possible impact forces.

The soft material of the protective means 202, 203 in Figs 2B-2C may have a stiffness in the range from 10 to 200 MPa. Fig. 2D shows application of protective means 204 which comprises a thin reinforcement coating, such as an inorganic layer which fills micro interstices in the edges of the second cover member and prevent chipping which could result from impacts between the edges of the second cover member 112 and the support structure 130. Material examples of the reinforcement coating comprises Al203 and SiO2 which may be applied e.g. by atomic layer deposition or chemical vapor deposition.

DK 2021 70033 A1 9 Similar to Fig. 2C, the reinforcement coating may be applied after dicing the plate material into the second cover members 112 and before the non-fluid body 105 is connected/applied to the inwardly pointing surface of the second cover member

112.

Fig. 3 shows application of protective means 301 which comprises a soft material applied to only to the corners of the second cover member 112. The soft material, having a stiffness in the above-mentioned ranges and made from similar materials may be applied before the non-fluid body 105 is connected to the second cover member 112. Fig. 4 shows application of protective means 401 which comprises an elastic material or visco elastic material, such as structured, e.g. corrugated, soft tape, elastic adhesive strips or other strip like elements. The protective means 401 may be arranged to connect only the corners of the second cover member to the support structure. Thus, the elastic connections are arranged so that the tensile and compressive forces generated in the elastic connections in response to lateral displacement of the second cover member always will attempt to center the second cover member 112. Thereby, the elastic connections will limit the lateral movement of the second cover member 112. The protective means 401 in the form of elastic connections may be configured to minimally restrict vertical displacements of the second cover member 112 in the direction of the optical axis. Accordingly, the elastic connections should have low stiffness in the vertical direction. Fig. 5 shows steps A-F in a possible process for providing at least the edges of the second cover members 112 with a shock impact absorbing material 501. The steps comprise: Step A: Providing the plate material for the second cover members 112. Step B: Dicing the plate material into the second cover members 112 by use of a suitable cutting method. Step C: Appling a soft material such as polymer or glue onto the diced second cover members 112 so that at least the gaps between the second cover members

DK 2021 70033 A1 10 are filled, but possibly also so that the upper surfaces are covered.

After application of the soft material, a curing process may be applied.

Step D: Removing such as scraping off excess material.

The removal of material may be performed so that a thin layer remains on the top surfaces of the second cover members 112 as in Step E, or so that the material on the top surfaces is completely removed as in Step F.

According to Step E, the soft material should be transparent and have a refractive index corresponding to that of the non-fluid body 105. Finally, a protective tape applied on the AR coated side 502 in step A before the dicing process in step B may be removed.

Fig. 6 shows a camera module 600 comprising the controllable optical assembly 199 and an image sensor 601 arranged to receive light transmitted through the optical assembly 199 which may include both variable lenses and optical tilt devices.

Additional optical components such as fixed optical lenses 602 may be arranged optically connected with the optical assembly 199. In this example, the optical axis is folded such as by a mirror or prism comprised by the optical assembly 199. The camera module 600 may be used in an electronic device such as a smart phone.

Claims

DK 2021 70033 A1 11 CLAIMS

1. A controllable optical assembly (199) with a variable optical power and/or a variable beam deflection, the optical assembly comprises - a transparent or reflective first cover member (111) -a transparent second cover member (112), - a transparent, deformable, non-fluid body (105) sandwiched between the first and second cover members, so that the first and second cover members and the non-fluid body constitute a lens with an optical axis (150) intersecting the non- fluid body and the first and/or the second cover members, - an actuator system (120) arranged to generate a controllable bending of the first cover member, - a support structure (130) arranged to support the first cover member (111) and arranged so that it at least partially surrounds the non-fluid body and the second cover member (112), and wherein the support structure provides a radial gap (182) between support structure and the non-fluid body and the second cover member so that the second cover member (112) is able to displace radially towards the support structure, - protective means comprising one or more of: a) a shock impact absorbing material (201, 202, 203, 301) arranged between the second cover member and the support structure to reduce shock impacts between an outer edge of the second cover member and the support structure, b) a reinforcement (204) of the outer edge of the second cover member, or c) an elastic connection (401) arranged between the second cover member and the support structure to restrain the radial displacement of the second cover member.

2. A controllable optical assembly according to claim 1, wherein the shock impact absorbing material is attached to the support structure.

3. A controllable optical assembly according to any of the preceding claims, wherein the shock impact absorbing material is attached both to the support structure (130) and the first cover member (111) so that the shock impact absorbing material partially fills the radial gap.

DK 2021 70033 A1 12 4, A controllable optical assembly according to any of the preceding claims, wherein the shock impact absorbing material is a coating extending over a surface of the support structure (130) and between the first cover member (111) and the transparent, deformable, non-fluid body (105).

5. A controllable optical assembly according to any of the preceding claims, wherein the shock impact absorbing material is attached to the edge of the second cover member (112).

6. A controllable optical assembly according to claim 5, wherein the shock impact absorbing material is a coating extending over an area between the second cover member (112) and the transparent, deformable, non-fluid body (105).

7. A controllable optical assembly according to any of the preceding claims, wherein the shock impact absorbing material is transparent.

8. A controllable optical assembly according to any of the preceding claims, wherein the reinforcement is arranged to fill micro interstices and prevent chipping of the outer edge of the second cover member.

9. A controllable optical assembly according to any of the preceding claims, wherein the elastic connection comprises one or more radially extending elastic members (401) connecting the second cover member (112) with the support structure (130).

10. A controllable optical assembly according to claim 9, wherein the elastic members exhibit a relative low stiffness to displacements of the second cover member along the optical axis (150) and a relative higher stiffness to displacements of the second cover member in the radial direction (181).

11. A controllable optical assembly according to any of the preceding claims, wherein the support structure comprises a rigid frame.

DK 2021 70033 A1 13

12. A controllable optical assembly according to any of the preceding claims, wherein the first cover member is fixed to the support structure and wherein the one or more actuators are connected to a surface of the first cover member.

13. A controllable optical assembly according to any of the preceding claims, wherein the actuator system comprises one or more piezo electric elements connected to the surface of the first cover member.

14. A method for improving robustness of a transparent cover member of a controllable optical assembly, the controllable optical assembly comprises - a transparent or reflective first cover member (111) - a transparent second cover member (112), - a transparent, deformable, non-fluid body (105) sandwiched between the first and second cover members, so that the first and second cover members and the non-fluid body constitute a lens with an optical axis (150) intersecting the non- fluid body and the first and/or the second cover members, - an actuator system arranged to generate a controllable bending of the first cover member, - a support structure (130) arranged to support the first cover member (111) and arranged so that it at least partially surrounds the non-fluid body and the second cover member (112), and wherein the support structure provides a radial gap between support structure and the non-fluid body and the second cover member so that the second cover member is able to displace radially towards the support structure, wherein the method comprises one or more of a) reducing shock impact amplitudes between an outer edge of the second cover member and the support structure by providing a shock absorbing material between the second cover member and the support structure, b) reinforcing an outer edge of the second cover member by providing said edge with a reinforcement, or c¢) restraining the radial displacement of the second cover member by providing an elastic connection between the second cover member and the support structure.