Motorized adjustment drive for lenses

Abstract

An electromotive drive (1) for moving at least one optical element (2) along an optical axis (3) of a lens, comprising a magnet arrangement (9) configured statically as a primary part and a coil actuator device (7, 4) configured axially movable as a secondary part and encompassing the optical axis (3), wherein the magnet arrangement (9) consists of a plurality of flat magnets (13) arranged symmetrically and evenly distributed around the circumference, and the coil device (7) consists of a hollow coil body (7) with a polygonal cross-section, having a plurality of planar surface segments of the same size, with one or more current conductors arranged in a plurality of mutually parallel windings on the outer circumference of the coil body (7) on the surface segments in the circumferential direction, and the at least one optical element (2) is mounted in the actuator device (4) arranged within the coil body (7), characterized in that - the number of flat magnets (13) corresponds to the number of surface segments, - an edge length (L) of the flat magnets (13) is adapted to the length of the side of a lateral surface segment of the coil body (7), - the actuator device (4) arranged within the coil body (7) has connecting elements (6) with the coil body (7) in the radial direction, - the flat magnets (13) are arranged with an air gap parallel to the lateral surface segments of the coil body (7) inside a yoke body forming a magnetic main return path (10) with equal length legs as the inner (11, 11') and outer (12) part of the main return path, and - two diametrically opposed guide systems (20, 20') for the axially movable secondary part designed as an actuator (4) are arranged parallel to the optical axis (3), the radial distance of which from the optical axis is smaller than the radial distance of the lateral surface segments of the coil body (7).

Description

[0001] The invention relates to an electromotive drive for adjusting optical elements along an optical axis of a lens according to the preamble of claim 1.

[0002] Electric motor drives are available in various designs for focusing and adjusting the focal length of photographic lenses. These primarily include small, compact DC motors, ultrasonic motors, and stepper motors with gear units.

[0003] Ultrasonic motors are also known as drive systems. These are designed as ring motors arranged around the circumference of a lens mount. Ring motors usually use gear transmission to drive the focusing and focal length adjustment elements in the axial direction. They require complex electronic control with high electrical voltages. Mechanical friction between the stator and rotor generates contamination inside the lens barrel and impairs imaging performance through deposits on the optical elements.

[0004] A device for axially adjusting the position of an optical imaging system is known from DE 197 18 189 A1. The optical imaging system is arranged within a support ring, which is guided longitudinally in a housing. Magnetic elements are arranged in the outer circumferential surface of the support ring. These magnetic elements follow a controllably arranged magnetic field on the outer circumference of the housing, thereby axially displacing the support ring with the imaging system.

[0005] EP 1 884 813 A1 discloses an electromagnetic drive for the axial adjustment of an optical imaging system held in a mount. The electromotive drive consists of a coil arrangement wound parallel to the optical axis of the imaging system and a permanent magnet enclosing the optical axis as an arc segment. The coil arrangement and the permanent magnet share a common iron yoke. When energized, the coil winding moves over the arc segment of the permanent magnet, thereby adjusting the mount of the optical imaging system via a pin / slot coupling guided in a cam carrier.

[0006] US 2008 / 0186601 A1 discloses a lens drive device based on the moving coil principle, with a square-shaped coil body featuring alternating shorter and longer outer surfaces. The coil body has an octagonal cross-section, with a yoke body with inner and outer legs forming a magnetic main return path only at the four shorter corners. The magnetic force acts perpendicularly on the coil only at the four shorter segments with the magnetic main return path.

[0007] US 2009 / 0237815 A1 discloses a compact lens drive device based on the voice coil principle, in which a coil with an octagonal cross-section is partially enclosed by four magnets arranged in the corners of a square module housing. Due to its design, the magnetic force acting on the coil is disadvantageously limited to only four segments. Such drives are also referred to as voice coils.

[0008] US 2017 / 0023764 A1 shows a voice coil lens drive module with an autofocus mechanism. The coil used has an octagonal cross-section with asymmetrical, alternating short and long surface segments. Space-saving installation in a square module housing is achieved by four magnet elements with a trapezoidal cross-section, whose bases are arranged on the long surface segments of the coil. Significant parts of the coil are not exposed to a magnetic field, thus resulting in a low efficiency and a low motor constant.

[0009] JP 2009271204 A discloses a lens drive device with inductive detection of the lens position without a position sensor. A coil with an octagonal cross-section, movably arranged in a magnetic field, is partially enclosed by a yoke body with a U-shaped cross-section. The disadvantage is that only a portion of the coil circumference is used to generate movement. To generate an inhomogeneous magnetic field, the yoke body has a shorter inner leg and a longer outer leg. A flat magnet is arranged on the longer outer leg. The position of the movable coil within the yoke body is determined using a position detection circuit. The position detection circuit detects a change in inductance caused by a change in the relative position of the movable coil to the yoke body.

[0010] Electromotive drives based on the voice coil principle, in the aforementioned designs suitable exclusively for small moving masses, such as single lenses in miniature camera modules, therefore consist of one or more permanent magnets and a winding body with current conductors located in an air gap in the magnetic field. If a current flows through the current conductors applied to the winding body, the winding body moves in the magnetic field of the permanent magnet due to the Lorentz force in a direction orthogonal to the plane spanned by the magnetic field direction and the current direction. Cylindrical electromotive drives or voice coils are constructed according to the so-called moving coil principle, i.e. the coil is located in a magnetic pot. If the winding body moves relative to the statically arranged magnetic pot, the magnetic pot is referred to as the primary part of the electromotive drive and the winding body as the secondary part.If the winding body is arranged statically and the magnet arrangement is movable, the winding body is referred to as the primary part and the magnet arrangement as the secondary part. For cylindrical voice coil motors, designs using the so-called multi-coil principle are also known, in which the so-called motor constant can be optimized despite a compact installation space. The motor constant is the ratio of the force generated by the magnetic field and current strength to the power loss. The higher the motor constant, the less heat is generated due to power loss when generating a predetermined force. Consequently, the motor constant is a measure of a motor's efficiency in converting electrical energy into kinetic energy. Since the winding resistance of the current conductors on the winding body increases with increasing temperature, the power loss also increases. For this reason, the motor constant is also temperature-dependent.

[0011] Because the position of the coil body changes in relation to the magnetic field generated by the permanent magnets, the force generated by the current flowing in the coil's conductors depends on the position of the coil. Complex current or voltage controls are required for constant or rapid force generation. To increase the force generated by such an electromotive drive, either the voltage and / or the current can be increased. Both are disadvantageous for mobile applications, such as the motor drive of heavy optical elements in lenses, as these rely on the use of batteries. Increasing the coil current requires a further adjustment of the coil geometry. This results in the coil becoming larger and the energy consumption increasing.Another disadvantage is the maximum possible current, which is limited by the technical specification of electronic motor driver components.

[0012] Another way to increase the generated force is to increase the magnetic flux density by using larger and stronger magnets. The disadvantage of this is that the space required for the motor drive concept is disproportionately increased, preventing the use of compact lenses and small focus groups, even with lenses with large lenses.

[0013] The object of the invention was to optimize the power and efficiency of prior art electric motor drives, e.g., those based on the voice coil principle, and to increase the motor constant. A further objective was to keep the space required for the drive compact while maintaining or reducing the power consumption, while simultaneously enabling use with large photographic lenses.

[0014] These objects are achieved in an electric motor drive of the type mentioned at the outset by the features of patent claim 1; advantageous further developments are the subject of the subclaims.

[0015] The key finding of the invention is that, in every axial movement position of the coil, the length of the current conductor is maximized in the magnetic field acting on the coil, or the coil length is optimized in the effective magnetic field. Furthermore, the invention provides that the magnetic field generating the Lorentz force and acting on the coil length is optimized in terms of its orthogonality over the entire axial displacement path of the coil body and is thus aligned as perpendicularly as possible to the current conductors of the coil in order to optimize the resulting force generation in the axial direction or in the direction of the optical axis.

[0016] An electric motor drive according to the invention has a static magnet arrangement as the primary part of a motor for moving optical components along the optical axis of a lens. An axially movable coil actuator device with the optical axis as its center is provided as the secondary part of the motor, wherein the optical component or several optical components, such as a focus element of a lens, are mounted in the actuator device. The magnet arrangement consists of a large number of flat magnet elements arranged symmetrically and evenly distributed around the circumference, and the coil device consists of a hollow coil body with a polygonal cross-section and a large number of flat, uniformly sized shell surface segments. According to the invention, the number of flat magnets corresponds to the number of shell surface segments.Advantageously, an edge length of the flat magnets L is adapted to the length L' of the side of a lateral surface segment of the coil former and is between 10% greater or 10% smaller than the length L' of the side of a lateral surface segment (L = L' ± 10% L'). One or more current conductors consisting of a plurality of parallel windings are applied to the lateral surface segments on the outer circumference in the circumferential direction. The actuator device with the optical element to be moved is arranged within the coil former. According to the invention, the actuator device arranged within the coil former has a plurality of connecting elements, such as connecting webs, in the radial direction with the coil former. In this way, a stable, compact and torsion-resistant connection is created between the actuator device and the coil former, which enables the movement of larger masses.In a particularly material-saving design, the current conductors applied in the circumferential direction on the outer circumference are wound in the circumferential direction at the end of the connecting webs extending parallel to the optical axis, so that the lateral surface segments of the coil body are formed by the large number of approximately 200 parallel windings of the current conductors. If a current flows in one direction through the current conductors, the Lorentz force causes the actuator device with optical component to move in one direction, so that the coil device is moved axially in one direction in the magnet arrangement like a moving coil or voice coil. If the current flows in the other direction through the current conductors, the coil device with actuator device and optical component moves axially in the other direction.

[0017] In a particularly advantageous manner, the flat magnets are arranged with a narrow air gap, i.e. at a distance smaller than the material thickness of the coil former, parallel to the outer surface segments of the coil former, with one flat magnet per outer surface segment being arranged inside a yoke body. According to the invention, the yoke body forms a magnetic main yoke with equally long legs as the inner and outer part of the main yoke or yoke body. In this way, the yoke body or the magnetic main yoke completely encompasses the outer surface segment of the coil former. In this way, the magnet arrangement advantageously forms a homogeneous magnetic field that penetrates the outer surface segments of the coil former at an orthogonal angle. One yoke body is provided for this purpose.The yoke bodies which are open on one side, or the yoke body arrangement formed from a plurality of yoke bodies arranged concentrically around the optical axis, can advantageously be introduced during production and for assembly purposes of the coil body.

[0018] The homogeneity and direction of the magnetic field acting on the coil segments is advantageously ensured by the fact that the flat magnets have the same polarization in the radial direction.

[0019] Depending on the required or available installation space for the electric motor drive according to the invention, the flat magnets are arranged optionally in the yoke body on the inner or outer part of the magnetic main magnetic return path. To generate a particularly strong magnetic field, split flat magnet pairs of identical polarity can be arranged in the yoke body. In this case, one flat magnet part is advantageously attached to the inner part of the main magnetic return path and one to the outer part, or secured by adhesive.

[0020] For advantageous and further improved homogenization of the magnetic field generated in the coil's air space, a magnetic shunt connecting the inner and outer parts of the main magnetic return path is provided on the open side of the yoke body. This creates a homogeneous magnetic field orthogonal to the direction of movement within the coil body's maximum axial movement range using current conductors.

[0021] In a particularly compact design of the electric motor drive, the cross-sectional edge length of the surfaces of the inner parts of the respective main yokes (inner legs of the yoke bodies) facing the coil segments of the coil body is smaller than the edge length of the flat magnets attached to the inner surface of the outer parts of the respective main yokes (outer legs of the yoke bodies). A particularly homogeneous and equally strong magnetic field can be created using individual yoke bodies in which the cross-sections of the outer and inner parts of the main yoke are designed to match in terms of their surface area. In this case, the inner parts of the main yoke have a greater radial strength than the outer parts of the main yoke, despite having a smaller edge length. In this way, compact external dimensions of the entire electric motor drive can also be achieved.

[0022] According to the invention, for straight guidance of the actuator, two statically arranged guide systems are provided, preferably as guide rods, parallel to the optical axis and diametrically opposed, for the axially movable secondary part (actuator with optical element) between the coil former and the open diameter of the actuator. The radial distance of the guide rods from the optical axis is therefore smaller than the radial distance between the lateral surface segments of the coil former, or smaller than the radial distance of the coil from the optical axis. One of the guide rods serves as a support system on which the actuator is guided radially, free of play and tilt, aligned parallel to the optical axis. One guide rod is aligned parallel to the optical axis and thus represents a plain bearing for the actuator.The actuator is further guided on the second guide rod via a radially elongated hole formed in the actuator in such a way that pivoting movement about the opposite sliding guide axis is prevented. This prevents over-determination of the bearing, which could lead to jamming, and ensures straight guidance of the optical components along the optical axis.

[0023] Particularly advantageously, the guide systems are designed as guide rods and arranged in a space-saving manner between two adjacent legs of the inner parts of the main magnetic return path. The radial distance of the guide rods from the optical axis corresponds to the radial distance of the inner parts of the magnetic main magnetic return path, so as not to restrict the open diameter for the optical components. The inner parts of the main magnetic return path (inner legs of the yoke), located on the circumference to the left and right of the guide rods, have a smaller edge length or cross-sectional width than the other inner parts of the main magnetic return path.

[0024] In an embodiment of the electric motor drive according to the invention that is particularly suitable for lens motor drives, the coil former has six, eight, ten, or twelve circumferential surface segments. The coil former is advantageously formed by a plurality of essentially parallel windings of current conductors running in the circumferential direction. The hollow actuator has connecting elements that are evenly distributed around its circumference according to the number of circumferential surface segments. These connecting elements are designed as narrow web-like projections, with the windings of the current conductors resting at an angle to their outer ends. A hexagonal cross-sectional shape for the coil former has proven particularly advantageous, with the individual parallel current conductors resting at an angle of 120° on the web-like projections of the connecting elements. The circumferential surface segments are at an angle of 120° to one another.In a further advantageous design, particularly suitable for creating an optimized, homogeneous magnetic field, the coil former has an octagonal cross-section with internal angles of 135° to each other. During winding production, the current conductors bend at a 45° angle at the web-like projections on the circumference of the hollow actuator.

[0025] The combination of these measures makes it possible to optimize the power and efficiency of the electric motor drive for use with large photographic lenses. With 200 optimally coordinated windings of current conductors and the use of flat magnets with a remanent flux density between 0.8 and 1.6, preferably 1.4 Tesla, it is possible to generate a constant flux density of 0.5 to 0.6 Tesla in the gap of the yoke body. The coil, which is arranged in the strong and constant, homogeneous magnetic field generated in this way, increases the motor constant such that masses of up to 4 N (Newton) can be moved at a speed suitable for autofocus applications. For example, a moving mass of up to 100 grams can be moved at 4 m / sec. 2This allows for use in large photographic lenses while maintaining a compact design. The power consumption is comparable to that of conventional arrangements and can even be optimally reduced with the arrangements described.

[0026] An embodiment of an electric motor drive according to the invention is shown schematically in the drawing and is described in more detail below with reference to the figures.

[0027] This shows Fig. 1 a longitudinal section through a motor drive, Fig. 2a a cross-section through a motor drive, Fig. 2b a detail view of Fig. 2a Fig. 3 Representation in the direction of the optical axis with schematically shown magnetic secondary return paths, Fig. 4 a cross-section through a magnet arrangement with flat magnets as two-part flat magnet pairs of rectified polarization, Fig. 5 a detail view X from Fig. 4 with SN SN polarization.

[0028] In the Fig. 1 schematically shown in a longitudinal section, an optical element 2 with optical axis 3 is mounted in an actuator device 4. The actuator device 4 is designed to be axially movable and has in the area of ​​the optical element 2 (a schematically shown lens 2) in Fig. 2a, which connect the actuator device 4 to a coil body 7. The connecting elements 6 are directed radially outwards, are longitudinally extended in the axial direction and are formed in the shape of a web between the actuator device 4 and the coil body 7. The connecting elements 6 have a Fig. 2a, which runs parallel to the optical axis 3 and serves to support the coil former 7 or its windings of current conductors (not shown). The length of the web edge 8 corresponds to the axially defined width B of the coil former 7 or the current conductors wound side by side and flat on top of one another on the web edge 8. Fig. 1 further shows a statically designed magnet arrangement 9, which consists, among other things, of a yoke body which is U-shaped in the sectional view and forms a magnetic main yoke 10. The magnetic main yoke 10 has a magnetically active inner part 11 and a magnetically active outer part 12. The coil 7 and flat magnets 13 are arranged between the inner part 11 and the outer part 12 of the magnetic main yoke 10. The flat magnet(s) 13 can be fastened to the outer part 12 of the magnetic main yoke 10 by an adhesive connection (not shown). The inner part 11 of the main yoke 10 is arranged facing the optical axis 3 and thus enclosing the actuator device 4 in the region of the lens 2. The inner part 11 and the outer part 12 form the equally long legs of a U-shaped yoke body.The end of the U-shaped yoke body of the magnetic main yoke 10, which is open for assembly purposes, covers a magnetic secondary yoke 14 connecting the inner part 11 and outer part 12 of the main yoke. The actuator device 4 can be divided according to their functions into a coil actuator part 5 and a sensor actuator part 15, which adjoins it in the axial direction and extends outside the magnet arrangement 9. The coil actuator part 5 has the mount for the optical element 2 and, as described above, is connected to the sensor actuator part 15 by connecting elements 6 (see . Fig. 2a) is connected to the coil 7 consisting of a plurality of electrical conductors (not shown in detail). A further position sensor ensures the axial displacement position of the actuator device 4 relative to the statically arranged magnet arrangement 9. The position sensor is, for example, controlled by a Fig. 1 on the sensor actuator part 15, schematically illustrated, and a sensor 17 statically assigned to it. A space-saving magnetoresistive absolute value sensor scale 16 (MR sensor 16 / 17) is advantageously used, the functionality of which is not disrupted by its arrangement outside the coil actuator part 5 and thus also outside the strong magnetic field of the magnet arrangement 9. Of course, other position sensors are also possible, such as magnetoresistive incremental encoders. In this case, the sensors must be calibrated both during production and each time the motor is switched on, during which the front and rear end positions of the actuator device 4 are detected. An optical grating scale has the advantage that the position sensors are not disrupted by the strong magnetic field of the magnet arrangement 9.The axial position of the actuator device 4 relative to the static magnet arrangement 9 can be reliably determined in this way. A schematically illustrated front damper 18 with a front end stop 19 that is adjustable in the axial direction is arranged on the front side of the coil actuator part 5. The front damper 18 with front end stop 19 can also consist of a damper arrangement comprising several dampers 18 distributed around the front circumference of the actuator device 4. In the opposite front area of ​​the sensor actuator part 15, a rear damper 18' with an associated rear end stop 19' that is adjustable in the axial direction is provided with the same effect. This advantageously prevents a collision of the coil former 7 at the front and rear ends of the maximum axial displacement path at the main return path 10 or the secondary return path 14.Impact noises in the respective end positions of the actuator device 4 in the de-energized state of the coil 7 can be prevented.

[0029] In Fig. 2a, the polarization direction of the magnetic field is marked by S and N for two of the flat magnets 13. This polarization direction applies to all Fig. 2a schematically shown flat magnets 13. In Fig. 2a shows a guide rod 20 aligned parallel to the optical axis 3 for axially guiding the actuator device 4 in the upper area. Diametrically opposite in the lower area, another parallel aligned guide rod 20' is arranged. In order to ensure the open diameter for the lens 2 is as large as possible, the guide rods 20 / 20' are arranged at a distance from the optical axis 3 which is, on the one hand, smaller than the radial distance of the web edges 8 and, on the other hand, larger than the radius of the lens 2. In the case of a guide rod not in Fig. In the embodiment shown in Figure 2a, all inner parts 11 of the magnetic main yoke are identical and are arranged at a distance from the optical axis 3 which is greater than the radial distance of the guide rods 20 / 20' from the optical axis 3. Particularly space-saving and ensuring the largest possible diameter for the lens 2 is a distance of the guide rods 20 / 20' each from the optical axis 3 which corresponds to the distance of the inner parts 11 of the magnetic main yoke from the optical axis 3.

[0030] To clarify the dimensioning of the inner parts 11 of the magnetic main return, Fig. 2b an enlarged section of Fig. 2a. The inner part of the magnetic main return path 11' arranged to the left of the guide rod 20 is smaller in terms of its cross-sectional edge length l' facing the coil 7 than the cross-sectional edge length l of the further inner part of the magnetic main return path 11. The respective Fig. The inner parts 11' of the magnetic main yoke shown in Figure 2a, adjacent to one of the guide rods 20 / 20', have a smaller cross-sectional edge length l' than the remaining inner parts 11 of the magnetic main yoke, which are designed with a larger cross-sectional edge length l optimized for homogenizing the magnetic field. The magnetically effective cross-sectional area 21 of the outer part 12 of the magnetic main yoke is sketched between the dimension lines for the edge length L of the flat magnets 13 and L' of the length of the side of a lateral surface segment of the coil former 7. Ideally, the magnetically effective cross-sectional area 21 of the outer parts of the magnetic main yoke 12 corresponds to the magnetically effective cross-sectional area 22 of the inner parts of the magnetic main yoke 11.Since the cross-sectional edge length l' of the inner part of the magnetic main return path 11' adjacent to the guide rod 20 is smaller, this has a cross-sectional geometry for adaptation which causes the magnetically effective cross-sectional area 22' to correspond to the magnetically effective cross-sectional area 22 of the other inner parts of the magnetic main return path 11.

[0031] To further clarify the structure of the electric motor drive 1 according to the invention, Fig. 3 shows a view in the direction of the optical axis 3 with schematically illustrated magnetic secondary return paths 14. The cutaway views also show the connecting elements 6 arranged between the coil actuator part 5 and the coil 7. The coil 7 is wound on the web edges 8 on the outer circumference. The lens 2 with optical axis 3 is mounted in a mount 5. Adjacent to the guide rods 20 / 20', the inner parts of the magnetic main return path 11' with a smaller cross-sectional edge length l' can be seen.

[0032] In Fig. 4 shows a variant of the electromotive drive 1 according to the invention with two-part flat magnet pairs 13', 13'' as flat magnets per shell surface segment of the coil body 7. For the sake of clarity, not all features are shown in Fig. 4 with reference numerals. The two-part flat magnet pairs 13', 13'' are arranged in the U-shaped yoke body on the inner 11, 11' and outer 12 parts of the main magnetic return path. The coil 7 is arranged between the flat magnet pair parts 13', 13'' with a narrow air gap. The respective air gap between coil 7 and flat magnet pair part 13' or flat magnet pair part 13'' is smaller than the radial thickness of the coil 7. The edge length of one flat magnet part 13'' (or first flat magnet pair part 13'') is adapted to the length L' of the side of a lateral surface segment of the coil body 7 and is arranged on the outer 12 part of the main magnetic return path and fixed, for example, by means of adhesive technology. The edge length of the other flat magnet part 13' (orThe second flat magnet pair part 13') is adapted to the cross-sectional edge length l, l' of the surface of the inner 11, 11' part of the magnetic main return path facing the lateral surface segments of the coil body 7 and is arranged or glued thereto. The edge length (l, l') of these inner second flat magnet pair parts is thus smaller than the edge length (L') of the first flat magnet pair parts 13'' on the outer part 12 of the magnetic main return path.

[0033] In Fig. 5 is the Fig.4 Section marked with X, shown enlarged as a detailed illustration. The polarization of the magnet pair parts 13', 13'' alternates from the inside to the outside, resulting in the following structure from the inside to the outside: inner part 11' of the magnetic main return path, small second flat magnet pair part 13' with polarity S - N, outer surface segment of the coil body 7, large first flat magnet pair part 13'' with polarity S - N, outer part 12 of the magnetic main return path. A reversed polarity from the inside to the outside, N - S for the small second flat magnet pair parts and N - S for the large first flat magnet pair parts is also possible. List of reference symbols 1 Electric motor drive 2 optical element / lens 3 optical axis 4 Actuator device 5 Coil actuator part / socket 6 connecting elements 7 coil body / coil 8 web edge 9 Magnet arrangement 10 magnetic main return 11.11' inner part of the main magnetic return 12 outer part of the main magnetic return 13 flat magnets 13',13'' flat magnet pair parts 14 magnetic shunt 15 Sensor actuator part 16 Sensor scale 17 Sensor 18 / 18' front / rear shock absorber 19 / 19' front / rear end stop 20 / 20' guide rods 21 magnetically effective surface outer part magnetic main return 22.22' magnetically effective area inner part magnetic main return B Width coil body 7 L edge length flat magnet L' Length of the side of a lateral surface segment of the coil body l, l' cross-sectional edge length of inner parts main return 11,11'

Claims

[1] An electromotive drive (1) for moving at least one optical element (2) along an optical axis (3) of a lens, comprising a magnet arrangement (9) designed to be static as a primary part and a coil actuator device (7, 4) designed to be axially movable as a secondary part and encompassing the optical axis (3), wherein the magnet arrangement (9) consists of a plurality of flat magnets (13) arranged symmetrically and evenly distributed around the circumference, and the coil device (7) consists of a hollow coil body (7) with a polygonal cross-section, having a plurality of planar surface segments of the same size, with one or more current conductors applied in a plurality of mutually parallel windings on the outer circumference of the coil body (7) on the surface segments in the circumferential direction, and the at least one optical element (2) is mounted in the actuator device (4) arranged within the coil body (7), characterized by , that - the number of flat magnets (13) corresponds to the number of surface segments, - an edge length (L) of the flat magnets (13) is adapted to the length of the side of a lateral surface segment of the coil body (7), - the actuator device (4) arranged within the coil body (7) has connecting elements (6) with the coil body (7) in the radial direction, - the flat magnets (13) are arranged with an air gap parallel to the lateral surface segments of the coil body (7) inside a yoke body forming a magnetic main return path (10) with equal length legs as the inner (11, 11') and outer (12) part of the main return path, and - two diametrically opposed guide systems (20, 20') for the axially movable secondary part designed as an actuator (4) are arranged parallel to the optical axis (3), the radial distance of which from the optical axis is smaller than the radial distance of the lateral surface segments of the coil body (7). [2] Electric motor drive (1) according to claim 1, characterized by that the flat magnets (13) have the same polarization in the radial direction. [3] Electric motor drive (1) according to claim 1 or 2, characterized by that the flat magnets (13) in the yoke body are arranged on the inner (11, 11') or outer (12) part of the main magnetic return, or the flat magnets are designed as two-part flat magnet pairs (13', 13'') of rectified polarization, wherein a flat magnet part (13') is arranged on the inner (11, 11') and a flat magnet part (13'') is arranged on the outer (12) part of the main magnetic return. [4] Electric motor drive (1) according to one of claims 1 to 3, characterized by that on the open side of the yoke body, a magnetic secondary return (14) connecting the inner (11, 11') and the outer (12) part of the main return is arranged, so that the maximum axial movement range of the coil body (7) with current conductors has a magnetic field that is homogeneous orthogonal to the direction of movement. [5] Electric motor drive (1) according to one of claims 1 to 4, characterized by that the cross-sectional edge length (l, l') of the surface of the inner (11, 11') part of the main return path facing the lateral surface segments of the coil body (7) is smaller than the edge length (L) of the flat magnets (13). [6] Electric motor drive (1) according to claim 5, characterized bythat the guide systems (20, 20') are arranged between each two adjacent legs of the inner parts (11') of the main return path at a radial distance of the inner parts (11, 11') of the main return path from the optical axis (3). [7] Electric motor drive (1) according to one of the preceding claims, characterized by that the coil body (7) has six, eight, ten or twelve surface segments.

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