TECHNICAL FIELD

The disclosure relates to an optical system for an electronic apparatus, the optical system comprising an optical unit and a drive for moving the optical unit.

BACKGROUND

There are several difficulties relating to optical systems for portable electronic apparatuses. Electronic apparatuses such as smartphones 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 etc.

The challenges associated with providing sufficiently good optical systems for smartphones are similar to those faced by pocket-size digital still cameras. The components needed to achieve high-quality images take up a lot of space, but when the apparatus is not in use, it should have a very slim form factor. To achieve this, retractable or “pop-up” optics are used to enable a large optics height when in use, and a slim apparatus when in transport mode.

Furthermore, the optics have to be quick (the pop-up movement should take much less than 500 ms), silent, and accurate (an accuracy in the pop-up direction of ~3 pm is required).

Prior art solutions face challenges such as noisy mechanics, mechanically hard-wearing parts, large power consumption, insufficient reliability and robustness, inaccurate positioning, too large size, or high-cost components.

Hence, there is a need for an improved optical system for an electronic apparatus.

SUMMARY

It is an object to provide an improved optical system for an electronic apparatus. 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 system for an electronic apparatus, the optical system comprising an optical unit and a drive module, the optical unit being at least partially enclosed by the drive module, the drive module being configured to generate rotary motion around a first axis, and the optical unit comprising a connection structure configured to convert the rotary motion generated by the drive module to linear motion of the optical unit along the first axis.

The drive module allows a direct and fixed mechanical connection such that there is no need for a gear system that takes up space and which can become damaged or worn over time. Furthermore, slack between the drive module and the optical unit is prevented. Slack is an undesired feature since it means that when changing the direction of rotation, the linear movement of the lens module does not follow immediately but only after some rotation. This would make focusing slow and inaccurate and must be avoided.

In a possible implementation form of the first aspect, the optical unit comprises at least one lens module, allowing the optical system to be used with, e.g. image sensors.

In a further possible implementation form of the first aspect, the drive module comprises a stepper motor comprising a stator body, a rotor body enclosed by the stator body, the stator body and the rotor body being coaxially arranged along the first axis, and an electromagnetic assembly configured to rotate the rotor body relative to the stator body around the first axis. Stepper motors have two sets of teeth that are configured to align, enabling accurate movement of the motor since the rotor will move the distance of one tooth size only when a voltage pulse is applied to the electromagnetic assembly, i.e. the rotor will not rotate freely when current is applied.

In a further possible implementation form of the first aspect, the stator body and the rotor body are annular elements, the stator body having an inner diameter larger than an outer diameter of the rotor body. This allows a motor having an as small size as possible, in particular a very thin motor.

In a further possible implementation form of the first aspect, the optical unit is arranged in a hollow space delimited by an inner diameter of the rotor body. This arrangement enables placing the motor in direct drive configuration around the lens module. Furthermore, the functional parts of the rotor can relatively easily be shrunk into a smallest possible size so that the hollow space can be utilized for the optical unit or for minimizing the size of the overall solution.

In a further possible implementation form of the first aspect, the electromagnetic assembly comprises a magnetic element arranged within the rotor body, and a coil assembly arranged between the stator body and the rotor body, the coil assembly comprising a plurality of coils configured to generate a magnetic field attracting or repelling the rotor body via the magnetic element, a change in the magnetic field generating stepwise rotation of the rotor body around the first axis relative the stator body, allowing the coils and magnet element remain aligned throughout the movement of the optical unit such that the strength of the magnetic field is unaffected.

In a further possible implementation form of the first aspect, each coil is wound around a second axis extending perpendicular to the first axis. This allows the magnetic field to be the strongest in a direction which does not induce disturbance currents in the printed wiring boards of the apparatus.

In a further possible implementation form of the first aspect, the magnetic element is a permanent magnet, facilitating holding power also when coil assembly is unpowered.

In a further possible implementation form of the first aspect, each step of the stepwise rotation around the first axis corresponds to a range of movement of the lens module along the first axis, the range of movement being equal to a depth of focus of the lens module, facilitating highly accurate movement along the first axis.

In a further possible implementation form of the first aspect, the rotor body comprises two annular rotor sections arranged along the first axis, the annular rotor sections comprising ferromagnetic material, and the annular rotor sections being separated by the magnetic element. This allows use of a relatively small magnetic element that takes up less space and is less expensive. In a further possible implementation form of the first aspect, the connection structure is arranged between the lens module of the optical unit and the rotor body of the drive module, allowing an optical system which has an as small form factor as possible.

In a further possible implementation form of the first aspect, the connection structure comprises a threaded base element configured to rotate with the rotor body of the drive module, and the lens module comprises a thread configured to engage a thread of the threaded base element and is configured to move along the first axis in response to rotation of the rotor body around the first axis, the lens module (5) being configured to interlock with the threaded base element or the stator body such that rotation of the lens module is prevented. The threads transfer external load without damaging the drive, while also increasing the speed of the zoom action. Furthermore, the setup of threaded parts allows the optical system to be driven by means of a single drive module. Additionally, the height of the optical system is kept to a minimum.

In a further possible implementation form of the first aspect, the connection structure comprises at least one threaded base element, configured to be stationary relative the stator body of the drive module, and at least two threaded connectors partially nested within each other, the threaded connectors being configured to move along the first axis in response to rotation of the rotor body around the first axis, a first threaded connector being configured to accommodate the lens module, the first threaded connector being configured to be stationary relative the base element, and at least one second threaded connector being arranged between the threaded base element and the first threaded connector, the second threaded connector being configured to rotate relative the base element and the first threaded connector in response to rotation of the rotor body. Such a structure achieves the required focal length while still remaining rigid. The threads transfer external load without damaging the drive, while also doubling the speed of the zoom action. Furthermore, the setup of multiple threaded parts allows the optical system to be driven across an as large movement range as possible while still keeping the height of the optical system to a minimum.

In a further possible implementation form of the first aspect, the first threaded connector is configured to interlock with the threaded base element such that rotation of the first threaded connector is prevented, providing a simple and durable solution for preventing rotation. In a further possible implementation form of the first aspect, one of the first threaded connector and the threaded base element comprises a groove and the other of the first threaded connector and the threaded base element comprises a ridge engaging the groove, a longitudinal axis of the groove and a longitudinal axis of the ridge extending in parallel with the first axis, ensuring the movement of the first threaded connector is limited to along the first axis.

In a further possible implementation form of the first aspect, the first threaded connector interlocks with the threaded base element such that rotation of the first threaded connector is prevented, allowing the optical unit to be moved between a first end position and a second end position along the first axis in response to rotation of the second threaded connector around the first axis, providing a simple and reliable solution for preventing rotation.

In a further possible implementation form of the first aspect, the threaded base element and the threaded connectors are at least partially formed as hollow cylinders, at least one surface of each hollow cylinder comprising a thread configured to engage a corresponding thread of an adjacent hollow cylinder, providing a thin solution with a relatively large movement range.

According to a second aspect, there is provided an electronic apparatus comprising the optical system according to the above. This optical system allows the apparatus to have an optical system that is silent, reliable, responsive, and accurate.

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. la shows a perspective view of an optical system in accordance with an example of the embodiments of the disclosure, wherein the optical unit is in a first end position;

Fig. lb shows a perspective view of the example in Fig. la, wherein the optical unit is in a second end position;

Fig. 2a shows a partial cross-section of an optical system in accordance with an example of the embodiments of the disclosure, wherein the optical unit is in the first end position; Fig. 2b shows a partial cross-section of the example in Fig. 2a, wherein the optical unit is in the second end position;

Fig. 3a shows a partial cross-section of an optical system in accordance with an example of the embodiments of the disclosure, wherein the optical unit is in the first end position;

Fig. 3b shows a partial cross-section of the example in Fig. 3a, wherein the optical unit is in the second end position;

Fig. 4a shows a partial cross-section of an optical system in accordance with an example of the embodiments of the disclosure, wherein the optical unit is in the first end position;

Fig. 4b shows a partial cross-section of the example in Fig. 4a, wherein the optical unit is in the second end position;

Fig. 5a shows a partial cross-section of an optical system in accordance with an example of the embodiments of the disclosure, wherein the optical unit is in the first end position;

Fig. 5b shows a partial cross-section of the example in Fig. 5a, wherein the optical unit is in the second end position.

DETAILED DESCRIPTION

The present invention relates to an optical system 1 for an electronic apparatus, the optical system 1 comprising an optical unit 2 and a drive module 3, the optical unit 2 being at least partially enclosed by the drive module 3, the drive module 3 being configured to generate rotary motion around a first axis Al, and the optical unit 2 comprising a connection structure 4 configured to convert the rotary motion generated by the drive module 3 to linear motion of the optical unit 2 along the first axis Al.

The optical system 1 comprises an optical unit 2 and a drive module 3, and is configured for use in particular with smaller electronic apparatuses such as smartphones, however, the optical system 1 can be used with any size apparatus.

The optical unit 2 is arranged such that it is at least partially enclosed by the drive module 3. The optical unit 2 may comprise at least one lens module 5, the lens module in turn comprising at least one lens.

The drive module 3 is configured to generate rotary motion around a first axis Al. The optical unit 2 comprises a connection structure 4 configured to convert the rotary motion generated by the drive module 3 to linear motion of the optical unit 2 along the first axis Al. The drive module 3 is arranged such that it circumscribes the optical unit 2, i.e. the optical axis A2 of the optical unit 2 being coaxial with the rotation axis of the drive module 3, i.e. first axis Al.

The drive module 3 may comprise a stepper motor 6. The stepper motor 6 comprises a stator body 7 and a rotor body 8 enclosed by the stator body 7. The stator body 7 and the rotor body 8 are coaxially arranged along the first axis Al such that the rotor body 8 is nested within the rotor body 8.

The drive module 3 may be a direct drive module, i.e. configured to be operatively connected to the optical unit 2 by direct coupling or direct engagement of the rotor body 8 with a part of the connection structure 4 of the optical unit 2. As shown in Figs. 4a to 5b, the rotor body 8 of the drive module 3 may be directly connected, i.e. fixed, to the connection structure 4 such that the connection structure 4 rotates along with the rotor 8. As shown in Figs. 2a-3b, the the rotor body 8 of the drive module 3 may directly engage, i.e. physically interconnect with, one part of the connection structure 4, this one part rotating along with the rotor body 8 while further parts of the connection structure 4 are configured to not rotate, preventing the lens module 5 from rotating.

The stator body 7 and the rotor body 8 may be annular elements, the stator body 7 having an inner diameter that is larger than an outer diameter of the rotor body 8. The optical unit 2 may be arranged in a hollow space 10 delimited by an inner diameter of the rotor body 8.

The stepper motor 6 furthermore comprises an electromagnetic assembly 9 configured to rotate the rotor body 8 relative the stator body 7 around the first axis Al. The electromagnetic assembly 9 may comprise a magnetic element 11 arranged within the rotor body 8, and a coil assembly 12 arranged between the stator body 7 and the rotor body 8. The coil assembly 12 comprises a plurality of coils configured to generate a magnetic field attracting or repelling the rotor body 8 via the magnetic element 11. A change in the magnetic field, i.e. a change in the attracting or repelling force, generates a stepwise rotation of the rotor body 8 around the first axis Al relative the stator body 7.

Each step of the stepwise rotation around the first axis Al may correspond to a range of movement of the lens module 5 along the first axis Al, the range of movement being equal to a depth of focus of the lens module 5. As an example, the range of movement may be 3-7 mm and the movement may be executed in less than 500 ms. Furthermore, the step accuracy is sufficient for autofocus, such that the drive module can be used both for the main movement of the optical unit and autofocus.

Each coil of the coil assembly 12 may be wound around a second axis (A2) extending perpendicular to the first axis Al. The magnetic element 11, which is arranged within the rotor body 8, may be a permanent magnet. The direction of the magnetic field of the permanent magnet may be along the first axis Al.

The rotor body 8 may comprise two annular rotor sections 8a, 8b arranged along the first axis Al, i.e. being stacked on top of each other and separated and interconnected by the magnetic element 11.

The connection structure 4 may be arranged between the lens module 5 of the optical unit 2 and the rotor body 8 of the drive module 3. The connection structure 4 may comprise at least one threaded base element 13, configured to be stationary relative the stator body 7 of the drive module 3. As shown in Figs. 2a to 3b, the threaded base element 13 may be part of the stator body 7 or fixed to the stator body 7, and comprise an outer thread.

The connection structure 4 may also comprise at least two threaded connectors 14, 15 partially nested within each other. The threaded connectors 14, 15 are configured to move along the first axis Al in response to the rotation of the rotor body 8 around the first axis Al.

A first threaded connector 14 is configured to accommodate the lens module 5 as well as to remain stationary relative the base element 13 in a plane extending perpendicular to the first axis Al. The first threaded connector 14, and the lens module 5, do, in other words, not rotate around the first axis Al .

One or more second threaded connector(s) 15 are arranged between the threaded base element 13 and the first threaded connector 14. The second threaded connector(s) 15 are not connected to any other elements than the threaded base element 13 and the first threaded connector 14, i.e. the second threaded connector(s) 15 are configured to only transfer rotational movement to linear movement. The number of second threaded connectors 15 is chosen to fit the individual form factor of the optical system 1. Each second threaded connector 15 is configured to rotate relative the base element 13 as well as relative the first threaded connector 14 in response to rotation of the rotor body 8.

The threaded base element 13 and the threaded connectors 14, 15 may be at least partially formed as hollow cylinders, at least one surface of each hollow cylinder 13, 14, 15 comprising a thread configured to engage a corresponding thread of an adjacent hollow cylinder 13, 14, 15. As illustrated in Figs. 2a to 3b, the threaded base element 13 may comprise an outer thread. The first threaded connector 14 may comprise an inner thread. The second threaded connector 15 may comprise an outer thread configured to engage the inner thread of the first threaded connector 14 and an inner thread configured to engage the outer thread of the threaded base element 13.

The first threaded connector 14 may be configured to interlock with the threaded base element 13 such that rotation of the first threaded connector 14 is prevented, while still allowing the optical unit 2 to be moved between a first end position Pl, i.e. the extended position illustrated in Figs, la, 2a, and 3a, and a second end position P2, i.e. the retracted position illustrated in Figs, lb, 2b, and 3b, along the first axis Al in response to rotation of the second threaded connector(s) 15 around the first axis Al.

Either the first threaded connector 14 or the threaded base element 13 may comprise a groove, while the other of the first threaded connector 14 and the threaded base element 13 comprise a corresponding ridge engaging the groove. The longitudinal axis of the groove and the longitudinal axis of the ridge extend in parallel with the first axis Al, allowing the ridge and groove to slide relative each other in a direction parallel with the first axis Al, such that the first threaded connector 14 and the lens module 5 move along the first axis Al without rotating around the first axis Al .

The connection structure 4 may instead comprise a threaded base element 13 configured to rotate relative the stator body 7 of the drive module 3. As shown in Figs. 4a to 5b, the threaded base element 13 may be part of the rotor body 8 or fixed to the rotor body 8, and comprise an inner thread. The threaded base element 13 is configured to accommodate the lens module 5, and the lens module 5 may comprise an outer thread configured to engage the inner thread of the threaded base element 13. The lens module 5 is configured to move along the first axis Al in response to the rotation of the rotor body 8 around the first axis Al .

The lens module 5 may be configured to interlock with the threaded base element 13 such that rotation of the lens module 5 is prevented, while still allowing the optical unit 2 to be moved between a first end position Pl, i.e. the extended position illustrated in Figs. 4a and 5a, and a second end position P2, i.e. the retracted position illustrated in Figs. 4b and 5b, along the first axis Al in response to rotation of the threaded base element 13 around the first axis Al.

The present invention also relates to an electronic apparatus, such as a smartphone or tablet, comprising the optical system 1 described above.

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. Unless otherwise indicated, the drawings are intended to be read (e.g., cross-hatching, arrangement of parts, proportion, degree, etc.) together with the specification, and are to be considered a portion of the entire written description of this disclosure. As used in the description, the terms “horizontal”, “vertical”, “left”, “right”, “up” and “down”, as well as adjectival and adverbial derivatives thereof (e.g., “horizontally”, “rightwardly”, “upwardly”, etc.), simply refer to the orientation of the illustrated structure as the particular drawing figure faces the reader. Similarly, the terms “inwardly” and “outwardly” generally refer to the orientation of a surface relative to its axis of elongation, or axis of rotation, as appropriate.