TECHNICAL FIELD

The disclosure relates to an optical arrangement comprising a linear actuation module and an optical module, the optical module comprising a deformable volume.

BACKGROUND

There are difficulties relating to providing efficient optical systems into small electronic devices such as smartphones. Such electronic devices preferably have as small outer dimensions as possible, while optical systems require certain dimensions in order to provide sufficiently good image sharpness, spatial frequency, sensitivity, and so on.

Therefore, imaging zooms for portable electronic devices have mostly been digital, which however affects the resolution of the images. Digital zoom does not add any information to image, but is done only by cropping and scaling a portion of original image to larger size. Optical zoom, on the other hand, magnifies the target using lenses and provides more details in the original resolution, providing a better resolution image.

One solution for reducing the necessary dimensions is to use tunable lenses, which have strong refractive power due to high optical surface deformation caused by external or internal electromechanical actuation. A high deformation rate usually requires application of high force. Generation of such high force usually requires high power consumption or leads to an increased form factor or thermal issues. SUMMARY

It is an object to provide an improved optical 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 an optical arrangement comprising a linear actuation module and an optical module, the optical module comprising a deformable volume, the deformable volume comprising a first deformable area and a second deformable area, the linear actuation module comprising a drive element and a piston element, the drive element and the piston element being interconnected, the piston element being non-rotatably connected to the first deformable area, the drive element being rotatable around a center axis in a first tangential direction and in an opposite, second tangential direction, the piston element being moveable along the center axis in response to rotation of the drive element in the first tangential direction and the second tangential direction, and the second deformable area being at least partially deformable in a direction opposite to the direction of movement of the piston element.

Such a solution utilizes a structure that not only achieves the required magnification for but does so within a small form factor, which allows the optical arrangement to fit into a comparatively thin electronic device while still facilitating a focal length which is sufficient.

In a possible implementation form of the first aspect, the deformable volume comprises a lens, and at least a part of an optical axis of the optical module extends parallel to, and is offset from, the center axis, such that the actuation doesn’t take place in front of the optical axis of the lens.

In a further possible implementation form of the first aspect, the deformable volume comprises a first volume, comprising the first deformable area, and a second volume, comprising the second deformable area, and movement of the piston element generates a change of the first volume which change generates a corresponding change of the second volume, providing a solution having strong refractive power.

In a further possible implementation form of the first aspect, the linear actuation module further comprises a drive unit, the drive unit being configured to rotate the drive element around the center axis.

In a further possible implementation form of the first aspect, the drive unit comprises an electric motor and a transmission unit, the transmission unit being fixedly interconnected with the drive element.

In a further possible implementation form of the first aspect, the electric motor is DC motor, a stepper motor, or a piezo motor, providing small yet sufficient means for operating the optical arrangement.

In a further possible implementation form of the first aspect, the transmission unit is mounted directly onto the electric motor and comprises at least one of a leadscrew and gear, providing simple, reliable, and spatially efficient means for driving the optical arrangement.

In a further possible implementation form of the first aspect, the drive unit further comprises a sensor, preferably a hall sensor for monitoring the rotations of the motor.

In a further possible implementation form of the first aspect, the optical module further comprises a push plate arranged in the first deformable area of the deformable volume, providing additional stiffness to the deformable volume making it less sensitive.

In a further possible implementation form of the first aspect, the piston element is adhered to the first deformable area of the deformable volume, allowing a simple yet reliable connection between linear actuation module and optical module. In a further possible implementation form of the first aspect, the piston element is non- rotatably connected to the push plate by means of at least one of mechanical interlocking, magnetic attraction, and friction between the piston element and the push plate, allowing releasable connection between linear actuation module and optical module.

In a further possible implementation form of the first aspect, the linear actuation module further comprises a stopper element extending in parallel with the center axis, the piston element being non-rotatably connected to the stopper element.

In a further possible implementation form of the first aspect, one of the drive element and the piston element is an externally threaded shaft, and the other of the drive element and the piston element is an internally threaded hollow cylinder, the thread of the drive element being adapted for engaging the thread of the piston element. The threaded solution is spatially efficient and transfers, easily and reliably, rotational movement to linear movement, and vice versa.

In a further possible implementation form of the first aspect, the first deformable area becomes increasingly concave as an overlap between the thread of the drive element and the thread of the piston element decreases, and the first deformable area becomes increasingly convex as the overlap between the thread of the drive element and the thread of the piston element increases, the decrease and increase changing the refraction index of the second volume. The overlap provides sufficient mechanical support and guidance to the components of the linear actuation module.

In a further possible implementation form of the first aspect, the deformable volume comprises an elastic optical material.

In a further possible implementation form of the first aspect, the elastic optical material is a self-containing material, facilitating the use of high-viscosity materials. According to a second aspect, there is provided an electronic device comprising an optical arrangement according to the above.

This and other aspects will be apparent from and 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 shows a schematic illustration of an electronic device in accordance with one embodiment of the present invention; Fig. 2 shows a schematic illustration of a linear actuation module in accordance with an embodiment of the present invention;

Fig. 3a shows a schematic illustration of an optical arrangement in accordance with an embodiment of the present invention, wherein the linear actuation module is in a position which leaves the deformable volume of the optical arrangement unaffected;

Fig. 3b shows the embodiment of Fig. 3a, wherein the linear actuation module is in a first end position which leaves the first deformable area of the deformable volume concave and the second deformable area of the deformable volume convex;

Fig. 3c shows the embodiment of Figs. 3a and 3b, wherein the linear actuation module is in a second end position which leaves the first deformable area of the deformable volume convex and the second deformable area of the deformable volume concave; Fig. 4a shows a schematic illustration of an optical arrangement in accordance with an embodiment of the present invention, wherein the linear actuation module is in a position which leaves the deformable volume of the optical arrangement unaffected;

Fig. 4b shows the embodiment of Fig. 4a, wherein the linear actuation module is in a second end position which leaves the second deformable area of the deformable volume convex;

Fig. 4c shows the embodiment of Figs. 4a and 4b, wherein the linear actuation module is in a second end position which leaves the second deformable area of the deformable volume concave.

DETAILED DESCRIPTION

Fig. 1 shows an electronic device 10 comprising an optical arrangement described in further detail below. The housing and display of the electronic device 10 enclose a plurality of components, including the optical arrangement. The optical arrangement may be part of an imaging system such as a high magnification zoom camera.

The optical arrangement, shown in Figs 3a to 4c, comprises a linear actuation module 1 and an optical module 2. A further embodiment of the linear actuation module 1 is shown in Fig. 2.

The linear actuation module 1 comprises a drive element 4 and a piston element 5 which are interconnected. The drive element 4 is rotatable around a center axis C in a first tangential direction and in an opposite, second tangential direction. The piston element 5 is partially fixed such that it does not rotate around the center axis C together with the drive element 4 in the first tangential direction and the second tangential direction, but is nevertheless moveable along the center axis C in response to the rotation of the drive element 4. The rotational movement of drive element 4 is, in other words, transformed to a linear movement of piston element 5.

The linear actuation module 1 may further comprise a drive unit 6 configured to rotate the drive element 4 around the center axis C. The drive unit 6 may comprise an electric motor

7 and a transmission unit 8 , the transmission unit 8 being fixedly interconnected with the drive element 4. The electric motor 7 may be a small DC motor, stepper motor, or piezo motor. The transmission unit 8 may be integrated with, and/or mounted directly onto, the electric motor 7 and comprise at least one of a leadscrew and gear. The transmission unit

8 may comprise a planetary gearbox with suitable gearing ratio. The transmission unit 8 may also comprise the drive element 4, e.g. in the form of a common drive shaft, such that there is no need for a separate drive element 4. The drive unit 6 may comprise at least one sensor, preferably a hall sensor arranged within the electric motor 7, e.g. for detecting rotations.

The optical module 2 comprises a deformable volume 3, which comprises a first deformable area 3a and a second deformable area 3b as indicated in Figs 3a to 4c. The deformable volume 3 may comprise a first volume 3c, comprising the first deformable area 3a, and a second volume 3d, comprising the second deformable area 3 hr The piston element 5 is non-rotatably connected to the first deformable area 3a, and the second deformable area 3b may be at least partially deformable in a direction opposite to the direction of movement of the piston element 5, i.e. movement of the piston element 5 generates a change of the first volume 3c which change generates a corresponding, but opposite, change of the second volume 3d. This is shown in Figs. 3b and 4b, where movement of the piston element 5 in a direction towards the optical module 2 generates an increase of the second volume 3d. Correspondingly, Figs. 3c and 4c show movement of the piston element 5 in a direction away from the optical module 2, which generates a reduction of the second volume 3d.

The deformable volume 3 may comprise a lens, such as a tunable lens, and at least a part of an optical axis O of the optical module 2 may extend parallel to, but offset from, the center axis C, such that the linear actuation doesn’t take place in front of the optical axis of the lens. Hence, the lens is subject to off-axis compression by a non-symmetrical element.

In one embodiment, the deformable volume 3 comprises an elastic optical material, such as a soft polymer or a liquid contained within a transparent membrane. The elastic optical material may be a self-containing material which does not require a membrane, such as a gel. Such a self-containing material is non-flowing, i.e. has high viscosity, while a liquid contained within a membrane is flowing, i.e. has a low viscosity.

The piston element 5 may be adhered to the first deformable area 3a of the deformable volume 3, directly or to a push plate 9 arranged in the first deformable area 3a of the deformable volume 3.

The piston element 5 may also be non-rotatably connected to the push plate 9 by means of at least one of mechanical interlocking, magnetic attraction, and friction between the piston element 5 and the push plate 9.

In one embodiment, shown in Fig. 2, the linear actuation module 1 comprises a stopper element 11 extending in parallel with, but offset from, the center axis C. The piston element 5 is non-rotatably connected to the stopper element 11, e.g. by means of interconnecting and axially directed recesses and protrusions.

One of the drive element 4 and the piston element 5 may be an externally threaded shaft, and the other of the drive element 4 and the piston element 5 may be an internally threaded hollow cylinder, the thread of the drive element 4 being adapted for engaging the thread of the piston element 5. Figs. 2 to 4c show embodiments wherein the drive element 4 is an externally threaded shaft and the piston element 5 is an internally threaded hollow cylinder.

The first deformable area 3a becomes increasingly concave, see Figs. 3b and 4b, as an overlap between the thread of the drive element 4 and the thread of the piston element 5 decreases, and the first deformable area 3a becomes increasingly convex, see Figs. 3c and 4c, as the overlap between the thread of the drive element 4 and the thread of the piston element 5 increases. As the thread overlap decreases, the piston element 5 is moved in a direction towards the optical module 2, such that increased pressure is applied by the linear actuation module 1 onto the optical module 2, subsequently deforming the shape of the deformable volume 3. Correspondingly, as the thread overlap increases, the piston element 5 is moved in a direction from the optical module 2, such that the pressure applied by the linear actuation module 1 onto the optical module 2 decreases, also deforming the shape of the deformable volume 3.

The decrease and increase in thread overlap changes the shape of the first deformable area 3a, which shape can be or become flat as in Figs. 3a and 4a, concave as in Figs. 3b and 4b, and convex as in Figs. 3c and 4c. This change also affects the size of the first volume 3c. As the first deformable area 3a becomes increasingly concave, the first volume 3c is reduced and, correspondingly, the second volume 3d increased. As the first deformable area 3a becomes increasingly convex, the first volume 3c increases and, correspondingly, the second volume 3d is reduced. By changing the second volume 3d, the refraction index for light passing through of the second volume 3b is also changed.

The various aspects and implementations have 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. 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.

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