TECHNICAL FIELD

The disclosure relates to a lens arrangement comprising a chamber with a volume of transparent liquid, a method of operating such a lens arrangement, and to an optical system comprising two such lens arrangements.

BACKGROUND

In optical zoom cameras, piezo SIDM (Smooth Impact Drive Mechanism,) and VCM (Voice Coil Motor, magnet-coil) based actuation systems are used to drive two or more lens groups, at least one group for zoom and one group for focus. Such arrangements typically require long travel distances, e.g. several millimetres, depending on the zoom factor, and two or more actuators are typically needed for discretely moving the lens groups for zoom and focus, respectively. Furthermore, such arrangements are space consuming, and adjustment of such arrangements are slow, and noisy, as they comprise moving the actual lens.

Liquid lenses, on the other hand, operate on the principle of deforming the lens as opposed to moving the lens. Prior art discloses such a liquid lens, comprising a liquid chamber, being deformed by means of a change in the volume of liquid located within the liquid chamber. Liquid is transferred into, or from, the liquid chamber via tubes connected to a further chamber. A piston is arranged within said further chamber, and movement of the piston causes movement of the liquid due to the volumetric change caused by the piston. The piston is operated by the above-mentioned VCM (magnet-coil) based actuation systems. Such an arrangement is space consuming, and furthermore, the use of a VCM actuation system limits the amount of feree which can be generated. Reducing the size of a VCM actuation system leads to thermal and force generating problems, since a VCM actuation system requires a specific size in order to be able to generate sufficient force and in order to allow heat generated by the operating current to be dissipated. For these reasons, the VCM actuation system is conventionally arranged outside of the optical system.

SUMMARY

It is an object to provide an improved lens arrangement and an improved optical system comprising such a lens arrangement.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect, there is provided a lens arrangement comprising a chamber filled with a volume of transparent liquid, the chamber being delimited by walls, at least one of the walls being elastic, at least another one of the walls being a first transparent wall, the first transparent wall being elastic, a second transparent wall being placed opposite to the first transparent wall, the chamber being T-shaped or L-shaped and comprising a first wing delimited by the first transparent wall and by the second transparent wall, and a second wing delimited by the elastic wall.

Such a solution allows for a lens arrangement which is as compact as possible while still comprising all necessary functions. The branched shape of the lens arrangement allows it to accommodate a relatively large volume of liquid in relation to the external dimensions of the lens arrangement, the large volume of liquid, in turn, facilitating sufficient displacement of the first transparent wall in order for the lens arrangement to provide proper zoom and focus capabilities.

In a possible implementation form of the first aspect, the first wing and the second wing are arranged at a right angle to one another, facilitating maximum possible displacement of the elastic wall. In a further possible implementation form of the first aspect,

the lens arrangement further comprises an actuator configured to deform the elastic wall, allowing a simple and efficient way of displacing the elastic wall as well as the first transparent wall.

In a further possible implementation form of the first aspect, a rigid plate is associated with the at least one elastic wall, for engaging with the actuator, reinforcing the elastic wall such that it is not damaged by being in contact with the actuator.

In a further possible implementation form of the first aspect, the actuator is configured to at least one of push the elastic wall into the chamber and/or pull the elastic wall away from the chamber, allowing the actuator to travel an as short distance as possible outside of the chamber.

In a further possible implementation form of the first aspect, the actuator comprises at least one shape-memory alloy member, facilitating an efficient yet structurally simple actuator.

In a further possible implementation form of the first aspect, the actuator comprises at least one pair of parallel arranged shape-memory alloy members, allowing the actuator to travel bi-directionally.

In a further possible implementation form of the first aspect, the lens arrangement further comprises an electrically conductive bending arm connected to the at least one shape- memory alloy member, a first end of the bending arm being fixed, and a second end of the bending arm being arranged to move freely and to engage with the elastic wall or the rigid plate, providing support to the shape-memory alloy members.

In a further possible implementation form of the first aspect, the bending arm is arranged between a pair of the shape-memory alloy members in the same plane, and wherein one end of the bending arm is arranged to move freely in the plane upon being pulled by one of the shape-memory alloy members, providing a return force to the actuator such that the actuator returns to a neutral position when the actuator is deactivated. In a further possible implementation form of the first aspect, the lens arrangement further comprises electric couplings connecting to the one or more shape-memory alloy members and the bending arm being configured to conduct an amount of electric current through one of the shape-memory alloy members and the bending arm, so that the one shape- memory alloy member contracts along its length, activating the actuator and allowing it to travel a desired distance in response to the amount of current transferred.

In a further possible implementation form of the first aspect, the at least one shape- memory alloy member is a wire, rod, or strip with a circular, triangular, rectangular, or polygonal cross-section, facilitating an as space efficient yet strong shape-memory alloy member as possible.

According to a second aspect, there is provided an optical system comprising a first lens arrangement, a second lens arrangement, the first lens arrangement and the second lens arrangement being arranged so that the first transparent wall and the second transparent wall of both the first lens arrangement and the second lens arrangement are aligned along a common optical axis.

Such a solution allows for an optical system which is as compact as possible while still comprising all necessary functions, including proper zoom and focus capabilities.

In a possible implementation form of the second aspect, the first lens arrangement and the second lens arrangement are arranged between an image sensor and a prism, with the image sensor and the prism aligned along the common optical axis, facilitating an as space efficient optical system as possible.

According to a third aspect, there is provided a method of operating a lens arrangement comprising providing a lens arrangement, providing a bending arm connected to the one or more shape-memory alloy members, a first end of the bending arm being fixed, and a second end of the bending arm being arranged to move freely and to engage with the elastic wall or the rigid plate, providing at least one electric coupling connecting to the one or more shape-memory alloy members, selectively conducting electric current via the at least one electric coupling through one of the at least one shape-memory alloy members, causing an increase in the temperature of the shape-memory alloy member, leading to a contraction along the length of the shape alloy member, thereby displacing the freely moving end of the bending arm and causing it to deform the elastic wall, thereby changing the shape of the first transparent wall of the lens arrangement.

Such a method facilitates the operation of a lens arrangement which is as compact as possible while still comprising all necessary functions. The method provides a simple and efficient way of generating sufficient displacement of a chamber wall in order for the lens arrangement to provide proper zoom and focus capabilities.

According to a fourth aspect, there is provided an actuator comprising a bending arm, a first elongated SMA member and a second elongated SMA member, both having a first end and a second end, the first and second elongated SMA members being spaced parallel with the bending arm with the first and second elongated SMA members on opposite sides of the bending arm, a first support longitudinally spaced from a second support, the first support being secured to the bending arm and to the first ends of both SMA members, the second support being secured to the bending arm and to the second ends of both SMA members, a first electric coupling connecting to the first end of the first SMA member for conducting electric current through the first SMA member, a second electric coupling connecting to the first end of the second SMA member for conducting electric current through the second SMA member, and a third electric coupling between the bending arm and both second ends of the elongated SMA members. Such an actuator has sufficient range of motion, in two travel directions, while still being compact and comprising few components. Furthermore, the configuration of the actuator allows the actuator to be placed such that it does not significantly increase the dimensions of, e.g., the optical system into which it is placed.

In a possible implementation form of the fourth aspect, the bending arm is flexible and configured to return to an original state after being bent.

In a further possible implementation form of the fourth aspect, the first SMA member and the second SMA member are configured to contract when heated by an electric current running through the SMA member concerned. In a further possible implementation form of the fourth aspect, the first SMA member and the second SMA member are configured to relax when cooling down after ended heating by an electric current running through the SMA member concerned.

In a further possible implementation form of the fourth aspect, the first support is configured to be secured to another entity.

In a further possible implementation form of the fourth aspect, at least one of the first, second, and third electric couplings comprise a crimp.

In a further possible implementation form of the fourth aspect, either the first end of the bending arm is fixed and the second end of the bending arm is movable, or the first end of the bending arm is movable and the second end of the bending arm is fixed.

In a further possible implementation form of the fourth aspect, the free end of the bending arm is configured to actuate another entity.

In a further possible implementation form of the fourth aspect, the actuator comprises a controller configured for selectively conducting electric current through either the first SMA member or through the second SMA member.

These and other aspects will be apparent from the embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present disclosure, the aspects, embodiments and implementations will be explained in more detail with reference to the example embodiments shown in the drawings, in which:

Fig. 1 is a sectional view of a lens arrangement according to an embodiment in a first state, Fig. 2 is a sectional view of the lens arrangement of Fig. 1 in a second state,

Fig. 3 is a sectional view of the lens arrangement of Fig. 1 in a third state, Fig. 4 is an elevated view of an optical system according to an embodiment with a lens arrangement of Fig. 1 ,

Fig. 5 is a top view of the optical system of Fig. 4,

Fig. 6 is a side view of the optical system of Fig. 4,

Fig. 7 is an elevated view of an actuator and a lens arrangement of the optical system of Fig. 4

Fig. 8 is an elevated view of an actuator according to an embodiment,

Fig. 9 is a side view of the actuator of Fig. 8,

Fig. 10 is a top view of the actuator of Fig. 8,

Fig. 11 is an elevated view of the actuator of Fig. 8 without its base,

Fig. 12 is a side view of an actuator according to another embodiment,

Fig. 13 is an elevated view of the actuator of Fig. 12,

Fig. 14 is a is a diagrammatic side view of an actuator according to another embodiment in a first state, and

Fig. 15 is a diagrammatic side view of the actuator of Fig. 14 in a second state.

DETAILED DESCRIPTION

Figs. 1 to 3 show a lens arrangement 10 comprising a chamber 1 filled with a volume of transparent liquid. The chamber 1 is delimited by a plurality of walls 3, 4, 5 forming a closed housing 2. At least one of the walls 3 is elastic. At least one further wall is a first transparent wall 4 which is also elastic. A second transparent wall 5 is placed opposite to the first transparent wall 4. The housing 2 and the chamber 1 is preferably T-shaped or L- shaped, and comprises a first wing 7 delimited by the first transparent wall 4 and by the second transparent wall 5, and a second wing 8 delimited by the elastic wall 3. The first transparent wall 4 is arranged such that it extends along a direction perpendicular to the optical axis of the lens arrangement, and the elastic wall 3 is arranged such that it extends along a direction parallel to the optical axis of the lens arrangement, and perpendicular to the first transparent wall 4. The first transparent wall 4 and the second transparent wall 5 extend in parallel, as shown in Fig. 2.

Figs. 1 to 3 show a T-shaped chamber 1 , wherein the horizontally extending leg of the T corresponds to the second wing 8, and the vertically extending leg of the T corresponds to the first wing 7. The two wings 7, 8 are interconnected such that liquid can move between the two wings without obstruction. Each wing 7, 8 comprises at least one elastic wall, such that the internal volume of each wing can change in response to external influence, as shown in Figs. 1 and 3. This will be discussed in more detail further below. The first wing 7 and the second wing 8 are preferably arranged at a right angle to one another, however, any other suitable angle would be possible.

The elastic wall 3 may be provided with a rigid plate 9. The rigid plate 9 extends in parallel with the elastic wall 3, preferably across a center section of the elastic wall 3. Hence, the center section of the elastic wall 3 is reinforced while the side sections of the elastic wall 3 can expand and contract in response to movement of an actuator 20 engaging with the elastic wall 3/rigid plate 9 and being configured to deform the elastic wall 3. The rigid plate 9 on the elastic wall provides a rigid support for the actuator 20. Specifically the actuator is configured to engage the rigid plate and move said rigid plate and thus the elastic wall uniformly forward and backwards. In this manner an area of the elastic wall corresponding to the area of the rigid plate can be moved forward and backwards along a direction perpendicular to the optical axis of lens arrangement, while a portion of the elastic wall surrounding the rigid plate 9 is deformed to allow the movement. The rigid plate 9 may be fixed to the elastic wall so as to produce, when moved by the actuator 20, a corresponding deformation of the elastic wall to produce a change in the volume of the second wing 8.

The actuator 20 is bi-directional and configured to push the elastic wall 3 into the chamber 1 as well as pull the elastic wall 3 away from the chamber 1. When the elastic wall 3 is pushed into the chamber 1 , as shown in Fig. 1 , the internal volume of the second wing 8 decreases, and liquid is pushed from the second wing 8 into the first wing 7, increasing the internal volume of the first wing 7. When the elastic wall 3 is pulled from the chamber 1 , as shown in Fig. 3, the internal volume of the second wing 8 increases, and liquid is pulled from the first wing 7 into the second wing 8, decreasing the internal volume of the first wing 7.

The actuator 20 comprises at least one shape-memory alloy member 11 , 12, as shown in Figs 7 to 15. The shape-memory alloy member 1 1 , 12 may be a wire, rod, or strip with a circular, triangular, rectangular, or polygonal cross-section. In one preferred embodiment, the actuator 20 comprises at least one pair of parallel arranged shape-memory alloy members 11 , 12.

The actuator 20 further comprises an electrically conductive bending arm 13 which is connected to the shape-memory alloy members 1 1 , 12. The first end 14 of the bending arm 13 is fixed, e.g. to a first support 24, and the opposite second end 15 of the bending arm 13 is arranged to move freely and to engage with the elastic wall 3 or the rigid plate 9 (also shown in Figs. 7 and 8). Alternatively, the first end 14 of the bending arm 13 may be movable and the second end 15 of the bending arm 13 fixed. Regardless, the free end of the bending arm 13 is configured to actuate another entity such as the above-mentioned elastic wall 3. The bending arm 13 is flexible and configured to return to its original state, shown in Fig. 14, after being bent, shown in Fig. 15.

In one embodiment, the bending arm 13 is arranged between a pair of shape-memory alloy members 1 1 , 12 in the same plane, and one end of the bending arm 13 is arranged to move freely in the plane upon being pulled by one of the shape-memory alloy members, see Figs. 7 to 1 1. In this embodiment, the second end 15 of the bending arm 13 extends perpendicular to the first end of the bending arm 13. In a further

embodiment, shown in Figs. 12 and 13, the second end 15 of the bending arm 13 extends in parallel with, but in an opposite direction of, the first end of the bending arm 13.

Electric couplings 21 , 22 connect an electrical supply to the shape-memory alloy members 11 , 12 and the bending arm 13 being configured to conduct an amount of electric current through one of the shape-memory alloy members 11 , 12 and the bending arm 13. When supplying electric current to a shape-memory alloy member 11 , 12, the member contracts along its length, and as a result thereof the bending arm 13 is bent in a direction towards the electrically activated shape-memory alloy member 1 1 , 12.

When activating shape-memory alloy member 11 , the bending arm 13 is bent in a direction away from the elastic wall 3, pulling the elastic wall 3 from the chamber 1.

When activating shape-memory alloy member 12, the bending arm 13 is bent in a direction towards from the elastic wall 3, pushing the elastic wall 3 into the chamber 1. In other words, each of the shape-memory alloy members 1 1 , 12 are configured to contract when heated by an electric current running through the shape-memory alloy member 1 1 ,

12 concerned. Correspondingly, each of the shape-memory alloy members 1 1 ,12 are configured to relax when cooling down after ending the heating made by an electric current running through the shape-memory alloy member 11 , 12 concerned, i.e. when electric current is no longer supplied to the shape-memory alloy member 1 1 ,12.

A more detailed description of the actuator 20 is provided in the following.

The actuator 20 comprises a first elongated shape-memory alloy member 1 1 and a second elongated shape-memory alloy member 12, both having a first end and a second end. The first elongated shape-memory alloy member 1 1 and a second elongated shape-memory alloy member 12 are spaced and extend in parallel with the bending arm

13 such that the first shape-memory alloy member 1 1 and the second shape-memory alloy member 12 extend on opposite sides of the bending arm 13. The first ends of the shape-memory alloy members 1 1 , 12 and the first end 14 of the bending arm 13 may also be connected to an actuator housing 17.

The actuator 20 is further provided with a first support 24, configured to be secured to another entity such as the housing of an electronic device or a printed circuit board. The actuator 20 is also provided with a second support 23, the second support 23 being longitudinally spaced from the first support in the direction of the bending arm 13.

The first support 24 is secured to the bending arm 13 and to the first ends of both shape- memory alloy members 1 1 , 12. The second support 23 is secured to the bending arm 13 and to the second ends of both shape-memory alloy members 1 1 , 12.

A first electric coupling 21 connects the electrical supply to the first end of the first shape-memory alloy member 1 1 for conducting electric current through the first shape- memory alloy member 1 1. A second electric coupling 22 connects the electrical supply to the first end of the second shape-memory alloy member 12 for conducting electric current through the second shape-memory alloy member 12. Furthermore, there is a third electric coupling 23 arranged between the bending arm 13 and both second ends of the shape-memory alloy members 1 1 , 12. At least one of the first electric coupling 21 , the second electric coupling 22, and the third electric coupling 23 comprises a crimp. The actuator 20 may further comprise a controller configured for selectively conducting electric current through either the first shape-memory alloy member 1 1 or through the second shape-memory alloy member 12.

The present disclosure further relates to a method of operating a lens arrangement 10 such as that described above. The method comprises providing a lens arrangement 10 and an actuator 20. The actuator 20 is provided by means of providing a bending arm 13 connected to one or more shape-memory alloy members 1 1 ,12. The first end 14 of the bending arm 13 is fixed, and the second end 15 of the bending arm 13 is arranged to move freely and to engage with the elastic wall 3 or the rigid plate 9 of the lens arrangement 10. Furthermore, the method comprises providing at least one electric coupling 21 , 22 connecting to the one or more shape-memory alloy members 1 1 , 12. Electric current is selectively conducted via the at least one electric coupling 21 , 22 through one of the shape-memory alloy members 1 1 ,12, causing an increase in the temperature of the shape-memory alloy member 1 1 ,12, leading to a contraction along the length of the shape alloy member 1 1 , 12. Hence the freely moving end 14 of the bending arm 13 is displaced, causing it to deform the elastic wall 3 and thereby changing the shape of the first transparent wall 4 of the lens arrangement 10.

The present disclosure further relates to an optical system comprising two lens arrangements 10, 10’, see Figs. 4 to 6. The optical system comprises a first lens arrangement 10 and a second lens arrangement 10’. The first lens arrangement 10 and the second lens arrangement 10’ are arranged so that the first transparent wall 4 and the second transparent wall 5 of both the first lens arrangement 10 and the second lens arrangement 20 are aligned along a common optical axis. The first lens arrangement 10 and the second lens arrangement 10’ may be arranged between an image sensor 19 and a prism 18, with the image sensor 19 and the prism 18 being aligned along the common optical axis. Furthermore, the optical system may comprise a first lens group 6 and a second lens group 16, arranged between the image sensor 19 and the prism 18. The first lens arrangement 10 is arranged between the first lens group 6 and the second lens group 16, and the second lens arrangement 10’ is arranged between the second lens group 16 and the prism 18. The various aspects and implementations has been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject-matter, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word“comprising” does not exclude other elements or steps, and the indefinite article“a” or“an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

The reference signs used in the claims shall not be construed as limiting the scope.