TECHNICAL FIELD

The disclosure relates to an electromagnetic actuator configured to generate movement of at least one optical module, the electromagnetic actuator comprising a magnet and an electromagnetic coil.

BACKGROUND

Electronic apparatuses such as portable smartphone devices today contain a number of moving opto-electro-mechanics systems, such as auto-focus, optical image stabilization, optical zoom, variable aperture, and mechanical shutter, all operated by small actuators.

The most commonly used actuating technology is based on so-called voice coil implementations. This is due to their constructional simplicity, parts availability, ease-of- manufacturability, and low cost. Voice coil-based actuators generally provide motive force by a magnet reacting to an electromagnetic field generated by a current passing through a coil of wire.

Such actuators having direct drive-based magnet-coil operation based on an oscillating magnet have a relatively short stroke. The resulting level of force depends on the magnetic flux vs. electric field interference. This reduces rapidly when the magnet has been moved such that the fields no longer interfere, which provides an upper limit to the stroke length and force level.

Such current and common actuators provide sufficient force to move masses having reasonably small sizes (100-1000 mg), however, they are unsuitable for use with certain optical elements such as tunable lenses having deformable membranes. These require relatively high force levels around -100-300 mN.

A further type of actuating technology comprises a rotary motor-based source unit equipped with a leadscrew turning the rotational movement into linear movement. Such actuators generally have a longer stroke, however, face challenges including poor response in terms of speed and operating (audible) noise. Rotary-based motors almost always require transmission elements to increase torque or convert the rotation into linear movement, and such transmission elements usually generate mechanical noise.

Yet another type of actuating technology comprises a piezo-electric system that generates continuous linear movement by means of a sequential drive pattern of small incremental piezo steps. The small sequential increments are rapidly activated and any mechanical parts having, e.g., stick-shift-based mutual couplings act as sources of noise as well.

Hence, there is a need for solutions that provide quiet and long-range movement of optical modules.

SUMMARY

It is an object to provide an improved electromagnetic actuator for generating movement of an optical module. 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 electromagnetic actuator configured to generate movement of at least one optical module, the electromagnetic actuator comprising a magnet arranged in nesting configuration with an electromagnetic coil in a first plane, the magnet being configured to pivot around a pivot axis extending in the first plane, and wherein pivoting movement of the magnet around the pivot axis is controlled by an electrical current in the electromagnetic coil, a connecting element configured to interconnect the magnet and the optical module, and to convert the pivoting movement of the magnet to the movement of the optical module.

Such an actuator not only has a relatively long actuation stroke but can also generate force sufficient to move optical elements having relatively high masses such as tunable lenses. By basing the actuation onto a rotational displacement between coil and magnet, significant improvements are achieved in power and force generation efficiency due to better field interaction, as well as in the magnitude of output displacement range, i.e. actuator stroke. Furthermore, the actuator is quiet and allows much flexibility in the configuration of surrounding components. Additionally, actuators comprising magnets and electromagnetic coils are generally simple, easy to manufacture, and have low cost. In a possible implementation form of the first aspect, the connecting element is fixedly connected to the magnet and a first end of the connecting element is configured to engage the optical module, wherein the pivoting movement of the magnet causes pivoting movement of the first end along an arched path in a second plane perpendicular to the first plane, facilitating a secure transfer of movement between the magnet and the optical module.

In a further possible implementation form of the first aspect, the magnet has a circular or rectangular cross-section as seen in the first plane, providing maximum flexibility.

In a further possible implementation form of the first aspect, the electromagnetic coil is configured to enclose a circumference of the magnet, a distance between an inner surface of the electromagnetic coil and a circumferential surface of the magnet being constant, improving efficiency due to less separation in the magnet-coil interface during rotation.

In a further possible implementation form of the first aspect, the electromagnetic actuator further comprises a return element configured to generate a return force on the magnet when the magnet is in a pivoted position and there is no electrical current in the electromagnetic coil, the return force returning the magnet to an equilibrium position wherein the magnet is arranged coplanarly with the electromagnetic coil in the first plane. This allows the magnet to be selfcentering, dispensing of the need for active return movement.

In a further possible implementation form of the first aspect, the return element comprises an elastic element fixed to opposite sections of the electromagnetic coil, a center of the elastic element being fixed to the first end of the connecting element or to an intermediate section of the connecting element located between the first end and the pivot axis. This allows the magnet to be returned to the equilibrium position by means of a cost-effective component having a very small form factor.

In a further possible implementation form of the first aspect, the return element comprises a further magnet superimposed with the pivot axis in a third plane parallel with the first plane, facilitating a reliable and durable way of returning the magnet to the equilibrium position. In a further possible implementation form of the first aspect, the electromagnetic actuator further comprises a sensor superimposed with the pivot axis in a fourth plane parallel with the first plane, facilitating detection of a change in the magnetic field generated by the pivoting magnet.

In a further possible implementation form of the first aspect, the connecting element is arranged to protrude from a first center surface area of the magnet, a longitudinal axis of the connecting element intersecting the pivot axis, facilitating movement of the optical module in a first direction perpendicular to the pivot axis.

In a further possible implementation form of the first aspect, the connecting element is arranged to protrude from a first peripheral surface area of the magnet, the longitudinal axis of the connecting element not intersecting the pivot axis, facilitating movement of the optical module in a second direction perpendicular to the pivot axis.

In a further possible implementation form of the first aspect, the connecting element is configured to protrude from a second center surface area or second peripheral surface area of the magnet, the second center surface area and the second peripheral surface area extending parallel with the first center surface area and the first peripheral surface area, the pivoting movement of the magnet causing pivoting movement of a second end of the connecting element along a second arched path in the second plane, the first end and the second end of the connecting element being opposite ends of the connecting element. This allows additional elements to be connected to the magnet or actuator, increasing the functionality and/or improving the actuator.

In a further possible implementation form of the first aspect, the second end of the connecting element comprises a counterweight configured to counteract a gravitational force applied onto the first end of the connecting element by the optical module. The counterweight balances the downwards directed gravitational force created by the optical module 2 when in a vertical position.

In a further possible implementation form of the first aspect, the connecting element comprises a first direct drive element, facilitating use with “periscope” cameras wherein a single optical module, e.g. comprising focusing lenses, in two directions along the optical axis of the optical module.

In a further possible implementation form of the first aspect, the electromagnetic actuator further comprises a second direct drive element, extending from the second end of the connecting element and being configured to interconnect the magnet and a further optical module and to convert the pivoting movement of the magnet to movement of the further optical module. This allows use of the actuator with, e.g., optical zoom cameras having both zooming and focusing lenses.

In a further possible implementation form of the first aspect, a first end of the second direct drive element is configured to engage the further optical module, and a second end of the second direct drive element is interconnected with the second end of the connecting element, the pivoting movement of the magnet generating movement of at least one of the optical module and the further optical module, allowing several optical modules to be moved individually or simultaneously.

According to a second aspect, there is provided an optical system comprising at least one electromagnetic actuator according to the above and at least one optical module, the electromagnetic actuator being configured to generate movement of the optical module(s) along a displacement axis extending parallel with, or transverse to, an optical axis of the optical module(s).

Such an optical system not only allows relatively long focal lengths but can comprise optical elements having relatively high masses such as tunable lenses. Such a system also allows fastfocusing lens actuation for, e.g., telecentric or periscope type cameras with long focal length, cameras that require extended lens movement.

In a possible implementation form of the second aspect, the first end of the connecting element and/or the first end of the second direct drive element is configured to engage the optical module(s) such that movement of the first end along an arched path generates movement of the optical module(s) along the displacement axis, allowing transfer of rotational movement to linear movement. In a further possible implementation form of the second aspect, the optical module(s) comprise(s) at least one recess configured to accommodate the first end of the connecting element or the first end of the second direct drive element, the recess allowing movement of the first end in a direction parallel with, or transverse to, the displacement axis. This is a simple and reliable solution for transferring rotational movement to linear movement.

In a further possible implementation form of the second aspect, the optical system comprises at least two optical modules and at least two electromagnetic actuators, each optical module being connected to one electromagnetic actuator, allowing several optical modules to be moved individually.

In a further possible implementation form of the second aspect, the optical system comprises two optical modules and one electromagnetic actuator, each optical module being connected to the connecting element or the second direct drive element of the electromagnetic actuator, allowing several optical modules to be moved simultaneously.

In a further possible implementation form of the second aspect, the optical system comprises one optical module and at least two electromagnetic actuators, the electromagnetic actuators being distributed around a periphery of the optical module and being configured to generate movement of the optical module around a first tilting axis and a second tilting axis, the first tilting axis and the second tilting axis extending perpendicular to the pivot axes of the electromagnetic actuators. This allows the use of a 2-axis tilting cradle platform holding the optical module and working as a gimbal OIS system.

In a further possible implementation form of the second aspect, the optical system comprises one optical module and four electromagnetic actuators distributed evenly around the periphery of the optical module and being configured to tilt the optical module around the first tilting axis and/or the second tilting axis, allowing both pitch and yaw tilting which creates an angular change of the optical axis of the optical system.

In a further possible implementation form of the second aspect, the periphery of the optical module comprises at least two grooves, each groove being aligned with one of the first tilting axis and the second tilting axis and being configured to allow movement around the other of the first tilting axis and the second tilting axis. According to a third aspect, there is provided an electronic apparatus comprising the optical system according to the above. Such an apparatus can be provided with optical elements having relatively high masses and which require relatively long focal lengths.

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 shows a cross-sectional view of a part of an electromagnetic actuator in accordance with an example of the embodiments of the disclosure;

Fig. 2 shows a schematic illustration of an optical system in accordance with an example of the embodiments of the disclosure;

Fig. 3a shows a schematic illustration of a part of an electromagnetic actuator in accordance with an example of the embodiments of the disclosure;

Figs. 3b and 3 c show sectional views of parts of electromagnetic actuators in accordance with examples of the embodiments of the disclosure;

Figs. 4a to 4c show schematic illustrations of an optical system in accordance with an example of the embodiments of the disclosure, illustrating the movement of the optical module generated by the electromagnetic actuator;

Figs. 5a to 5c show schematic illustrations of an optical system in accordance with an example of the embodiments of the disclosure, illustrating the movement of two optical modules generated by two electromagnetic actuators;

Fig. 6a shows a schematic illustration of an optical system in accordance with an example of the embodiments of the disclosure, wherein the electromagnetic actuator comprises a counterweight;

Fig. 6b shows a schematic illustration of an electromagnetic actuator in accordance with an example of the embodiments of the disclosure; the electromagnetic actuator comprising a counterweight;

Fig. 7 shows a schematic illustration of a part of an electromagnetic actuator in accordance with an example of the embodiments of the disclosure; Figs. 8a and 8b show schematic illustrations of a part of an electromagnetic actuator in accordance with an example of the embodiments of the disclosure, wherein the magnet is in a pivoted position as well as in an equilibrium position;

Fig. 9 shows a schematic illustration of an electromagnetic actuator in accordance with an example of the embodiments of the disclosure;

Figs. 10a and 10b show schematic illustrations of electromagnetic actuators in accordance with examples of the embodiments of the disclosure;

Figs. I la and 11b show further schematic illustrations of electromagnetic actuators in accordance with examples of the embodiments of the disclosure;

Figs. 12a to 12c show schematic illustrations of an optical system in accordance with an example of the embodiments of the disclosure, illustrating the movement of two optical modules generated by one electromagnetic actuator;

Figs. 13a to 13c show schematic illustrations of an optical system in accordance with an example of the embodiments of the disclosure, illustrating the movement of the optical module generated by the electromagnetic actuator;

Figs. 14a to 14c show schematic illustrations of an optical system in accordance with an example of the embodiments of the disclosure, illustrating the movement of one optical module generated by four electromagnetic actuators;

Fig. 14d show schematic illustrations of an optical system in accordance with an example of the embodiments of the disclosure, illustrating the movement of one optical module generated by two electromagnetic actuators.

DETAILED DESCRIPTION

The present invention relates to an electromagnetic actuator 1 configured to generate movement of at least one optical module 2, the electromagnetic actuator 1 comprising a magnet 3 arranged in nesting configuration with an electromagnetic coil 4 in a first plane Pl, the magnet 3 being configured to pivot around a pivot axis Al extending in the first plane Pl, and wherein pivoting movement of the magnet 3 around the pivot axis Al is controlled by an electrical current in the electromagnetic coil 4, a connecting element 5 configured to interconnect the magnet 3 and the optical module 2, and to convert the pivoting movement of the magnet 3 to the movement of the optical module 2. The present invention furthermore relates to an optical system 10 comprising at least one electromagnetic actuator 1 and at least one optical module 2, the electromagnetic actuator 1 being configured to generate movement of the optical modules 2 along a displacement axis A3 extending parallel with, or transverse to, an optical axis A4 of the optical modules 2, as well as an electronic apparatus comprising the optical system 10.

The electromagnetic actuator 1 is configured to generate movement of at least one optical module 2 such as a lens holder comprising lenses. The actuator is suitable for use for a variety of applications such as autofocus, lens shift OIS, sensor shift Optical Image Stabilization (OIS), miniature shutter, variable aperture, and optical zoom. The movement may be any kind of movement such as linear movement.

The electromagnetic actuator 1 comprises a magnet 3 arranged in nesting configuration with an electromagnetic coil 4 in a first plane Pl, as shown in Figs. 1 and 3a to 3c. By nesting is meant that the electromagnetic coil 4 encloses the magnet 3, i.e., that the magnet 3 is contained within the electromagnetic coil 4.

The magnet 3 is configured to pivot around a pivot axis Al extending in the first plane Pl, as illustrated in Figs. 1, 4a, 4c, 5b, 5c, 8b, 12a, 12c, 13a, 13c, and 14c. The pivoting movement of the magnet 3, around the pivot axis Al, is generated by manipulating the electrical current in the electromagnetic coil 4. In other words, when the electromagnetic coil 4 is supplied with current, electromotive force turns the magnet 3 around the pivot axis Al based on north-south poling directions, and forces the attractive poles of the magnet 3 and electromagnetic coil 4 to match.

A connecting element 5 is configured to interconnect the magnet 3 and the optical module 2, and to convert the pivoting movement of the magnet 3 to the movement of the optical module 2.

The connecting element 5 may be fixedly connected to the magnet 3. A first end 5a of the connecting element 5 may be configured to engage the optical module 2, as shown in, e.g., Fig. 2. The pivoting movement of the magnet 3 may cause a pivoting movement of the first end 5 a along an arched path in a second plane P2 perpendicular to the first plane Pl, i.e. by pivoting the magnet 3 and connecting element 5 around axis Al, the connecting element 5 moves within plane P2. The magnet 3 may have a circular cross-section, see Figs. 3b and 8a-8b, or a rectangular crosssection, see Fig. 3c, as seen in the first plane Pl.

The electromagnetic coil 4 may be configured to enclose a circumference of the magnet 3, a distance between an inner surface of the electromagnetic coil 4 and a circumferential surface of the magnet 3 being constant, as shown in Figs. 8a and 8b.

The electromagnetic actuator 1 may further comprise a return element 6, see Figs. 10a to 1 lb. The return element 6 is configured to generate a return force on the magnet 3 when the magnet 3 is in a pivoted position and there is no electrical current in the electromagnetic coil 4, i.e. allowing the magnet 3 to be self-centering. The return force returns the magnet 3 to an equilibrium position, shown in Figs. 2, 4b, 5a, 6a, 6b, 8a, 9 to 11b, 12b, 13b, and 14a. The magnet 3 is arranged coplanarly with the electromagnetic coil 4 in the first plane Pl, when in the equilibrium position.

The return element 6 may comprise an elastic element, e.g. a compression spring or metal flexure, fixed to opposite sections of the electromagnetic coil 4, as shown in Figs. 1 la- 1 lb. The center of the elastic element is fixed to the first end 5a of the connecting element 5, as shown in Fig. I la, or to an intermediate section 5c of the connecting element 5 located between the first end 5a and the pivot axis Al, as shown in Fig. 1 lb.

The return element 6 may also comprise a further magnet superimposed with the pivot axis Al in a third plane P3 parallel with the first plane Pl, as shown in Fig. 10b. The further magnet may be arranged on a printed wiring board (PWB), adjacent magnet 3 and aligned with the pivot axis Al.

The electromagnetic actuator 1 may also comprise a sensor 7 superimposed with the pivot axis Al in a fourth plane P4 parallel with the first plane Pl, as shown in Figs. lOa-lOb. The sensor 7 may be arranged on the backside of the PWB to provide closed loop control.

The sensor may be a hall sensor and/or configured to detect a change in the magnetic field generated by the magnet 3 and the electromagnetic coil 4, the change being induced by the pivoting movement of the magnet 3. The magnet 3 may be pivoted such that the magnet 3 extends in a fifth plane P5 intersecting the first plane Plat the pivot axis Al, as illustrated in Fig. 1, and at a pivot angle 0°<a<180° to the first plane Pl. For example, a ±25° deflection angle, from the first plane Pl, results in a total pivot angle a of 50°. With such a deflection, it has been proven that as much as 75 % of the actuator performance can be maintained.

The connecting element 5 may be arranged to protrude from a first center surface area of the magnet 3, a longitudinal axis A2 of the connecting element 5 intersecting the pivot axis Al. This is illustrated in Figs. 2, 4a-6b, 8a-12c, and 14a-14d. The length of the connecting element 5 along the longitudinal axis A2 can be selected to create a desired stroke length, making it suitable for both short stroke applications such as AF, OIS, deforming lens, and long stroke applications such as optical zoom.

The connecting element 5 may also be arranged to protrude from the first peripheral surface area of the magnet 3, the longitudinal axis A2 of the connecting element 5 not intersecting the pivot axis Al. In other words, the connecting element 5 is offset relative the pivot axis Al as shown in Figs. 13a-13c.

The connecting element 5 may furthermore be configured to protrude from a second center surface area or second peripheral surface area of the magnet 3, the second center surface area and the second peripheral surface area extending parallel with the first center surface area and the first peripheral surface area. This is illustrated in Figs. 6a, 6b, I la, 12a-12c, and 14a-14d. The pivoting movement of the magnet 3 causes a pivoting movement of a second end 5b of the connecting element 5 along a second arched path in the second plane P2, the first end 5a and the second end 5b of the connecting element 5 being opposite ends of the connecting element 5.

The second end 5b of the connecting element 5 may comprise a counterweight 8 configured to counteract a gravitational force applied onto the first end 5a of the connecting element 5 by the optical module 2, as illustrated in Figs. 6a, 6b, and 14a-14c. The counterweight 8 is a gravity balancing feature. As the magnet 3 turns around the pivot axis Al, it has a cantilever type of behavior. On one side of the cantilever, the optical module 2 constitutes a moving mass. In order to balance the optical module’s 2 downwards directed gravitational force when in a vertical position, a counterweight 8 can be added to the other side of the cantilever. This additional mass would be located behind the magnet. The connecting element 5 may comprise a first direct drive element, e.g. a link or lever directly interconnecting the magnet 3 and the optical module 2.

The electromagnetic actuator 1 may further comprise a second direct drive element 9, extending from the second end 5b of the connecting element 5 and being configured to interconnect the magnet 3 and a further optical module 2 and to convert the pivoting movement of the magnet 3 to movement of the further optical module 2. A second direct drive element 9 is shown in Figs. 12a- 12c. A first end 9a of the second direct drive element 9 may be configured to engage the further optical module 2, and a second end 9b of the second direct drive element 9 may be interconnected with the second end 5b of the connecting element 5, such that the pivoting movement of the magnet 3 generating movement of at least one of the optical module 2 and the further optical module 2.

The present invention further relates to an optical system 10 comprising at least one electromagnetic actuator 1 as described above and at least one optical module 2, as shown in Figs. 2, 4a-6a, and 12a-14d. The electromagnetic actuator 1 is configured to generate movement of the optical modules 2 along a displacement axis A3 extending parallel with, or transverse to, an optical axis A4 of the optical modules 2. The optical modules may be used to facilitate camera applications in a smartphone, such as the above-mentioned autofocus, lens shift OIS, sensor shift Optical Image Stabilization (OIS), miniature shutter, variable aperture, and optical zoom.

The optical system 10 may comprise additional components such as an image sensor, a sensor substrate (e.g. PWB), holding structures, linear guide shafts, static lenses, and angled reflective element, none of which are discussed further. The magnet 3 and electromagnetic coil 4 may, e.g., be side-mounted in a housing.

The first end 5a of the connecting element 5 and/or the first end 9a of the second direct drive element 9 may be configured to engage the optical modules 2 such that movement of the first end 5a, 9a along an arched path generates movement of the optical modules 2 along the displacement axis A3.

The optical modules 2 may comprise at least one recess 11 configured to accommodate the first end 5a of the connecting element 5 or the first end 9a of the second direct drive element 9, the recess 11 allowing movement of the first end 5a, 9a in a direction parallel with, or transverse to, the displacement axis A3. The first end 5a, 9a and recess 11 may be configured as a balljoint type interconnection, allowing the first end 5a, 9a to rotate within recess 11 as the optical module 2 is being moved.

As shown in Figs. 4a-4c, the optical system 10 may comprise one optical module 2 and one electromagnetic actuator 1. Such an embodiment has a long stroke and allows fast-focusing lens actuation for, e.g., a telecentric camera with long focal length. This type of camera optics requires extended lens movement.

As shown in Figs. 13a-13c, the optical system 10 may comprise one optical module 2 and one electromagnetic actuator 1, the actuator being configured to move the optical module 2 in a direction perpendicular to the optical module’s optical axis. This is useful for OIS implementations and for handling one of the two OlS-axes (pitch or yaw) of the camera.

As shown in Figs. 5a-6a, the optical system 10 may comprise at least two optical modules 2 and at least two electromagnetic actuators 1, each optical module 2 being connected to one electromagnetic actuator 1. This solution may be used for a “periscope” type optical zoom camera, commonly used with focusing lenses. The basic architectural parts are identical to the previous telecentric camera, with the addition of a second optical module 2.

As shown in Figs. 12a-12c, the optical system 10 may comprise two optical modules 2 and one electromagnetic actuator 1, each optical module 2 being connected to the connecting element 5 or the second direct drive element 9 of the electromagnetic actuator 1. The use of a second direct drive element 9 allows an optical zoom camera (variable focal length) having both zooming and focusing lenses.

As shown in Figs. 14a-14d, the optical system 10 may comprise one optical module 2 and at least two electromagnetic actuators 1, the electromagnetic actuators 1 being distributed around a periphery of the optical module 2. This allows use of a 2-axis tilting cradle platform holding the optical module and working as a gimbal OIS system.

The electromagnetic actuators 1 are configured to generate movement of the optical module 2 around a first tilting axis A5 and a second tilting axis A6, the first tilting axis A5 and the second tilting axis A6 extending perpendicular to the pivot axes Al of the electromagnetic actuators 1. By adjusting the mutual operation of the electromagnetic actuators 1, the optical module can be tilted around the first tilting axis A5 and the second tilting axis A6, for pitch and yaw, creating an angular change of the optical axis of the optical system 10.

The optical module 2 may further comprise a convex element 13 configured to provide center support to the optical module 2, as illustrated in Figs. 14a and 14c.

As illustrated in Fig. 14b, the optical system 10 may comprise one optical module 2 and four electromagnetic actuators 1 distributed evenly around the periphery of the optical module 2 and being configured to tilt the optical module 2 around the first tilting axis A5 and/or the second tilting axis A6. The four electromagnetic actuators 1 may be arranged on each side of a base housing such that the connecting element 5 of each actuator protrudes partly into the center cavity of the base housing. The cradle platform carrying the optical module 2 is arranged within the housing such that it is tiltable, e.g. by being supported against the base housing by the convex element 13, forming a bottom side gimbal pivot feature. The convex element 13 may be configured to allow the optical module 2 to be tilted around this point by e.g. ±3-5°.

The periphery of the optical module 2 may comprise at least two grooves 12, each groove 12 being aligned with one of the first tilting axis A5 and the second tilting axis A6 and being configured to allow movement around the other of the first tilting axis A5 and the second tilting axis A6. As shown in Figs, 14a, 14c, and 14d, the groove 12 may have an X-shaped crosssection. This prevents the coupling interfaces from limiting each other's tilting movement. The X-shape allows the first end 5a of one connecting element 5 to perform its normal tilt movement (e.g. around the first tilting axis A5), by having close contact with the upper and lower edges at the center of the groove 12, while still allowing slight rotation to allow tilting movement in a perpendicular direction (e.g. around the second tilting axis A6) to be performed freely, due to the wider gap formed at the edges of the groove 12.

The present invention also relates to an electronic apparatus, such as a smartphone, comprising the optical system 10 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.