Patent Description:
High-end digital camera modules, and specifically cellphone (e.g. smartphone) digital cameras include mechanisms that enable advanced optical function such as focus or optical image stabilization (OIS). Such mechanisms may actuate (e.g. displace, shift or tilt) an optical element (e.g. lens, image sensor, mirror) to create the desired optical function. A commonly used actuator is based on voice coil motor (VCM) technology. In VCM technology, a permanent (or "fixed") magnet and a coil are used to create actuation force. The coil is positioned in the vicinity of the magnetic field of the fixed magnet. Upon driving current in the coil, a Lorentz force is created on the coil, an in return an equal counter-force is applied on the magnet. The magnet or the coil is rigidly attached to an optical element to construct an actuated assembly. The actuated assembly is then moved by the magnetic Lorenz force. Henceforth, in this description, a VCM will be referred to also as "VCM engine" and an actuator including such a VCM (or VCM engine) will be referred to as to as "VCM actuator" or simply "actuator".

In addition to the magnetic force, a mechanical rail is known to set the course of motion for the optical element. The mechanical rail keeps the motion of the lens in a desired path, as required by optical needs. A typical mechanical rail is known in the art as "spring-guided rail", in which a spring or set of springs is used to set the motion direction. A VCM that includes a spring-guided rail is referred to as a "spring-guided VCM". For example, <CIT> discloses a lens element shifted in a linear spring rail to create focus. For example, international patent application <CIT> discloses the incorporation and use of a spring guided VCM in a folded camera structure ("FCS" - also referred to simply as "folded camera"). The disclosure teaches a lens element shifted to create focus and OIS and an optical path folding element (OPFE) shifted in a rotational manner to create OIS. Also, <CIT> teaches AF + OIS in a folded actuator where the actuator dos not add to the module height.

Another typical mechanical rail is known in the art a "ball-guided rail", see e.g. <CIT>. With a ball-guided rail, the lens is bound to move in the desired direction by set of balls confined in a groove (also referred to as "slit"). A VCM that includes a ball-guided rail is referred to as a "ball-guided VCM". A ball-guided VCM has several advantages over a spring-guided VCM. These include: (<NUM>) lower power consumption, because in a spring-guided VCM the magnetic force has to oppose a spring mechanical force, which does not exist in a ball-guided VCM, and (<NUM>) higher reliability in drops that may occur during the life-cycle of a camera that includes the VCM. The actuation method in <CIT> is designed for a standard non-folded lens, where the lens optical axis is directly pointed at the object to be photographed and cannot be used in a folded camera.

In view of the above, there is a need for, and it would be advantageous to have a linear ball guided VCM inside a folded camera to reduce the folded camera dimensions, in particular camera height and/or width. In addition, there is a need to show such a structure in a combination with various actuation mechanisms for the OPFEs in these cameras.

<CIT>, <CIT>, <CIT> disclose folded cameras, <CIT> discloses a camera.

Aspects of embodiments disclosed herein relate to VCMs to actuators including such VCMs, the actuators having linear ball-guided rails for AF and OIS in a folded camera, and to digital cameras, and in particular to cameras with folded optics that incorporate such VCMs.

In some exemplary embodiments there is provided an actuator for carrying and actuating a lens holder with a lens, the lens having a first optical axis, the lens receiving light folded from an optical path along a second optical axis that is substantially perpendicular to the first optical axis, the actuator comprising a first VCM engine coupled to the lens holder, a second VCM engine coupled to the lens holder, a first linear ball-guided rail operative to create a first movement of the lens holder upon actuation by the first VCM engine, wherein the first movement is in a first direction parallel to the first optical axis, and a second linear ball-guided rail operative to create a second movement of the lens holder upon actuation by the second VCM engine, wherein the second movement is in a second direction that is substantially perpendicular to the first optical axis and to the second optical axis.

In an exemplary embodiment, the first movement is for focus and the second movement is for OIS.

In an exemplary embodiment, an actuator further comprises a middle moving frame that includes at least one groove in the first direction and at least one groove in the second direction.

In an exemplary embodiment, the lens holder and the lens are made as one part.

In an exemplary embodiment, each of the first and second linear ball-guided rails includes a pair of grooves having at least one ball located therebetween.

In an exemplary embodiment, the first and second VCM engines include respective first and second VCM magnets.

In an exemplary embodiment, an actuator further comprises a static base, wherein the lens holder is movable only along the first direction with respect to the middle moving frame and wherein the middle moving frame is movable only along the second direction with respect to the static base.

In an exemplary embodiment, an actuator further comprises a static base, wherein the lens holder is movable only along the second direction with respect to the middle moving frame and wherein the middle moving frame is movable only along the first direction with respect to the static base.

In an exemplary embodiment, the first and second VCM magnets are fixedly attached to the lens holder.

In an exemplary embodiment, the first VCM magnet is fixedly attached to the lens holder and the second VCM magnet is fixedly attached to the moving frame.

In an exemplary embodiment, the first VCM magnet is fixedly attached to the moving frame, and the second VCM magnet is fixedly attached to the lens holder.

In an exemplary embodiment, the first VCM engine and the second VCM engine include respective first and second VCM coils mechanically coupled to the static base.

In an exemplary embodiment, an actuator further comprises at least one ferromagnetic yoke attached to the static base and used to pull the first VCM magnet in order to prevent both the first and the second linear ball-guided rail from coming apart.

In an exemplary embodiment, an actuator further comprises at least one ferromagnetic yoke attached to the static base and used to pull the first VCM magnet or the second VCM magnet in order to prevent both the first and the second linear ball-guided rail from coming apart.

In an exemplary embodiment, an actuator further comprises at least one ferromagnetic yoke attached to the static base and used to pull the second VCM magnet in order to prevent both the first and the second linear ball-guided rail from coming apart.

In an exemplary embodiment, the first and second VCM coils and the first and second VCM magnets are respectively separated by a constant distance.

In an exemplary embodiment, an actuator further comprises a first position sensor and a second position sensor for measuring a position of the lens upon the movement in the first and second directions, respectively.

In an exemplary embodiment, the first and second position sensors are Hall bar position sensors operative to measure the magnetic field of the first and the second VCM magnets, respectively.

In some exemplary embodiments, any of the actuators above may be included in a folded camera together with an OPFE that folds the light from the optical path along the second optical axis to an optical path along the first optical axis, wherein the OPFE is tiltable around the second direction by a spring based mechanism or a ball based mechanism.

In some exemplary embodiments, the folded camera is included together with an upright camera in a dual-aperture camera.

Aspects, embodiments and features disclosed herein will become apparent from the following detailed description when considered in conjunction with the accompanying drawings, in which:.

<FIG> shows an isomeric view of a linear ball guided VCM actuator <NUM> according to an example disclosed herein, the example not suitable for the claimed invention. <FIG> shows actuator <NUM> in an exploded view. Actuator <NUM> enables the shift of a lens <NUM> having an optical axis <NUM> (also referred to as "first optical axis") in two directions in a plane (i.e. the X-Y plane in the shown figures), as described below: AF operation in a direction <NUM> and OIS operation in a direction <NUM>. Actuator <NUM> has exemplary length/width/height dimensions in the range of <NUM>- <NUM>, i.e. actuator <NUM> can be contained in a box with dimension of 3x3x3 mm<NUM> to 40x40x40 mm<NUM>. The description continues with reference to a coordinate system XYZ shown in <FIG> and <FIG> as well as in a number of other figures.

In actuator <NUM>, lens <NUM> is positioned and held in a lens holder (or lens carrier) <NUM> that fits the shape of lens <NUM>. In some embodiments, lens holder <NUM> and lens <NUM> may be a single part. In some embodiments, they may be separate parts. In the following description and claims, the term "lens holder" may be describing a lens holder only, or a unified part (component) that includes a lens holder and a lens. Lens holder <NUM> may be made, for example, by plastic molding, or alternatively by other methods. Three magnets <NUM>,<NUM> and <NUM> are fixedly attached (e.g. glued) to lens holder <NUM> from below (in the negative Z direction in the figure). The assembly of lens holder <NUM> and magnets <NUM>-<NUM> will be referred to henceforth as "top actuated sub-assembly" <NUM>. <FIG> shows top actuated sub-assembly <NUM> from a bottom view. Lens holder <NUM> includes four grooves, 102a-d. Grooves 102a-d are parallel to each other and are along the Y-axis. Grooves 102a-d are used to guide top actuated sub-assembly <NUM> along the Y direction.

Actuator <NUM> further includes a middle moving frame <NUM>, typically made of plastic. <FIG> show middle moving frame <NUM> from top and bottom views, respectively. Middle moving frame <NUM> includes eight grooves 112a-h, four grooves 112a-d on a top surface of adaptor <NUM> along the Y direction and four grooves 112e-h on a bottom surface of adaptor <NUM> are along the X direction. Top actuated sub-assembly <NUM> is positioned on top of middle moving frame <NUM> such that grooves 112a-d are just below and parallel to grooves 102a-d, respectively.

In the example shown, four balls 114a-d are positioned on top of grooves 112a-d (one ball on top of each groove) such that balls 114a-d space apart lens holder <NUM> and middle moving frame <NUM> and prevent the two parts from touching each other. In other embodiments, actuator <NUM> may have more than one ball on top each groove 112a-d, for example up to <NUM> balls per groove. Balls 112a-d may be made from Alumina or another ceramic material, from a metal or from a plastic material. Typical ball diameters may be in the range of <NUM>-<NUM>. Other ball sizes and positioning considerations may be as in co-owned international PCT patent application <CIT> titled "Rotational Ball Guided Voice Coil Motor".

Since lens holder <NUM> and middle moving frame <NUM> are exemplarily plastic molded, there is some tolerance allowed in part dimensions, typically a few tens of microns or less for each dimension. This tolerance may lead to misalignment of position between adjacent (facing) grooves 102a-102b-112a-112b and/or 102c-102d-112c-112d. To better align the grooves, grooves 102a-d, 112a-b may be V-shaped, i.e. have a V cross-section shape to ensure ball positioning, while grooves 112c-d may have a wider, rectangular cross-section. Grooves 102a-b and 112a-b are aligned during assembly, while the alignment of grooves 102c-d and 112c-d has a small freedom allowed by the rectangular cross section.

The assembly of top actuated sub-assembly <NUM>, balls 114a-d, and middle moving frame <NUM> will be referred to henceforth as "bottom actuated sub-assembly" <NUM>.

Actuator <NUM> further includes a base <NUM>, typically made of plastic (<FIG> and <FIG>). Base <NUM> is molded with four grooves 122a-d along the X direction. Bottom actuated sub-assembly <NUM> is positioned on the top of base <NUM> such that grooves 122a-d are parallel to grooves 112e-h respectively. In the embodiment shown, base <NUM> only serves as part of actuator <NUM>. In other embodiments, the base plastic molding may extend to serve for other purposes, such as a base for an actuator associated with a prism, to hold a camera sensor, to hold a shield, to prevent stray light and dust from reaching image sensor, etc..

Four balls 124a-d are positioned on top of grooves 122a-d (one ball on top of each groove) such that balls 124a-d space middle moving frame <NUM> apart from base <NUM> and prevent the two parts from touching each other. In other embodiments, actuator <NUM> may have more than one ball on top each groove 122a-d, for example up to <NUM> balls per groove. The size, material and other considerations related to balls 124a-d are similar to those of balls 114a-d.

Actuator <NUM> further includes three metallic ferromagnetic yokes <NUM>, <NUM> and <NUM> fixedly attached (e.g. glued) to base <NUM> from above (positive Z direction in the figure) such each yoke is positioned below a respective one of magnets <NUM>, <NUM> and <NUM>. In other embodiments, ferromagnetic yokes <NUM>, <NUM> and <NUM> may be fixedly attached to base <NUM> from below. Each yoke pulls its respective magnet by magnetic force in the negative Z direction, and thus all yokes prevent both top actuated sub-assembly <NUM> and bottom actuated sub-assembly <NUM> from detaching from base <NUM>. Balls 114a-d prevent top actuated sub-assembly <NUM> from touching middle moving frame <NUM> and balls 124a-d prevent bottom actuated sub-assembly <NUM> from touching base <NUM>. Both top actuated sub-assembly <NUM> and bottom actuated sub-assembly <NUM> are thus confined along the Z-axis and do not move in positive or negative Z directions. The groove and ball structure further confines top actuated sub-assembly <NUM> to move only along the Y-axis and bottom actuated sub-assembly <NUM> to move only along the X-axis.

Actuator <NUM> further includes an electro-magnetic (EM) sub-assembly <NUM>, see <FIG> and <FIG>. EM sub-assembly <NUM> includes three coils <NUM>, <NUM> and <NUM>, two Hall bar elements <NUM> and <NUM> and a PCB <NUM>. Coils <NUM>-<NUM> and Hall bar elements <NUM>-<NUM> are soldered (each one separately) to PCB <NUM>. Coils <NUM>-<NUM> have exemplarily each a "stadium" shape and typically include a few tens of coil windings (i.e. in a non-limiting range of <NUM>-<NUM>), with a typical resistance of <NUM>-<NUM> ohm. PCB <NUM> allows sending input and output currents to coils <NUM>-<NUM> and to Hall bar elements <NUM>-<NUM>, the currents carrying both power and electronic signals needed for operation. PCB <NUM> may be connected electronically to the external camera by wires (not shown). EM sub-assembly <NUM> is positioned between magnets <NUM>-<NUM> and yokes <NUM>-<NUM>, such that each coil <NUM>-<NUM> is positioned between a respective one of magnets <NUM>-<NUM> and a respective one of yokes <NUM>-<NUM>. Upon driving a current in a coil (e.g. coil <NUM>), a Lorentz force is created on the respective magnet (i.e. magnet <NUM>); a current in a clockwise direction will create force in the positive Y direction, while a current in counter clockwise direction will create a force in the negative Y direction. Similarly, driving a current in coils <NUM> or <NUM> will create a respective Lorentz force on magnets <NUM> or <NUM>; a current in a clockwise direction will create force in the positive X direction, while a current in a counter clockwise direction will create a force in the negative X direction. A full magnetic scheme (e.g. fixed magnets <NUM>-<NUM> pole direction) is described in detail for example in co-owned patent application PCT/IB2016/<NUM>, and is known in the art.

Hall bar element <NUM> is positioned inside coil <NUM> and can sense the intensity and direction of magnetic field of magnet <NUM>. Hall bar element <NUM> can thus measure the respective position of magnet <NUM> along the Y direction. Hall bar element <NUM> is positioned inside coil <NUM> and can sense the intensity and direction of magnetic field of magnet <NUM> and therefore measure the respective positon of magnet <NUM> along the X direction. Two Hall bar elements can thus sense the motion of top actuated sub-assembly <NUM> in the X-Y plane and can serve as position sensors for closed loop control, as known in the art and as described for example in detail in co-owned patent application PCT/IB2016/<NUM>. Actuator <NUM> can thus serve to move lens <NUM> in the X-Y plane as needed by optical demands. The control circuit (not shown) may be implemented in an integrated circuit (IC). In some cases, the IC may be combined with Hall elements <NUM> and/or <NUM>. In other cases, the IC may be a separate chip, which can be located outside of the camera (not shown).

It may be noted that all electrical connections needed by actuator <NUM> are to EM sub-assembly <NUM>, which is stationary relative to base <NUM> and to the external world. As such there is no need to transfer any electrical current to any moving part.

Example <NUM> describes a general two-direction actuator. Other embodiments may have variations as follows:
In example <NUM>, top actuated sub-assembly <NUM> moves in the Y direction relative to middle moving frame <NUM> and to base <NUM>, while bottom actuated sub-assembly <NUM> moves in the X direction relative to base <NUM>. In other actuator embodiments, such as in an actuator <NUM>" shown in <FIG> and <FIG> below, top actuated sub-assembly <NUM> may move in the X direction relative to middle moving frame <NUM> and to base <NUM>, while bottom actuated sub-assembly <NUM> may move in the Y direction relative to base <NUM>.

In example <NUM>, there are two VCMs providing force in the X direction. This is done to reduce power consumption. In other embodiments, an actuator may have only one VCM providing force in the Y direction.

In example <NUM>, there is one VCM providing force in the Y direction. This is done to reduce space. In other embodiments, an actuator may have more than one VCM in the X direction (for example two VCM).

In example <NUM>, magnets <NUM> and <NUM> are fixedly attached to lens carrier <NUM> as part of top actuated sub-assembly <NUM>. Since magnets <NUM> and <NUM> provide force in the X direction and only need to move in the X direction relative to the base, in other embodiments magnets <NUM> and <NUM> may be fixedly attached to middle moving frame <NUM>.

In some embodiments, actuator <NUM> may include parts not shown in figures. These may include: mechanical shield, electrical connectivity to the external world, driving IC, interface to connect to other camera parts, etc..

<FIG> shows an isomeric view of a linear ball guided VCM actuator <NUM>' according to another example disclosed herein, the example not suitable for the claimed invention. <FIG> shows actuator <NUM>' in an exploded view. Actuator <NUM>' is similar to actuator <NUM> in structure (and therefore similar elements/components are not numbered and/or described) and function, except for a single difference: in actuator <NUM>, magnets <NUM> and <NUM> are attached to lens carrier <NUM>, while in actuator <NUM>', magnets <NUM> and <NUM> are attached not to lens carrier <NUM> but to middle moving frame <NUM>. Attaching magnets <NUM> and <NUM> to middle moving frame <NUM> allows full decoupling of the lens motion along the Y axis from magnets <NUM> and <NUM>; namely, any motion of lens carrier <NUM> along the Y axis will not influence position reading by Hall sensor element <NUM>.

<FIG> shows an isomeric view of a linear ball guided VCM actuator <NUM>" according to an embodiment suitable for the claimed invention. <FIG> shows actuator <NUM>" in an exploded view. Actuator <NUM>" is similar to actuator <NUM> in structure (and therefore similar elements/components are not numbered and/or described) and function, except for the following differences:.

<FIG> shows an actuator such as actuator <NUM>, <NUM>' or <NUM>" included in a folded camera structure <NUM>. For simplicity, the following description refers to actuator <NUM>, with the understanding that it applies equally well to actuators <NUM>' and <NUM>". In FCS <NUM>, actuator <NUM> serves exemplarily to move lens <NUM>. Actuation of actuator <NUM> is done in FCS <NUM> to create autofocus AF (lens motion along X-axis) and OIS (lens motion along Y-axis) as described in co-owned PCT/IB2016/<NUM>. FCS <NUM> further includes an OPFE <NUM> and an image sensor <NUM>. OPFE <NUM> folds the light from a second optical axis <NUM> to first optical axis <NUM>.

FCS <NUM> may further include other parts that are not displayed in <FIG>, such as a mechanical shield to protect the camera, stray light limiters, dust traps, IR filter(s), electrical circuitry for connection to external devices, control hardware, memory units (e.g. EEPROM), gyroscopes, etc. FCS <NUM> may further include an actuation mechanism for moving or tilting OPFE <NUM> for OIS around an axis <NUM>, axis <NUM> being substantially perpendicular to both optical axis <NUM> and optical axis <NUM>. Note that in FCS <NUM>, magnet <NUM> and coil <NUM> are positioned between lens <NUM> and image sensor <NUM>, a region known in the art as the "back focal length" (BFL) of lens <NUM>.

<FIG> shows an embodiment numbered <NUM> of another FCS that includes an actuator <NUM>", in which case the FCS is according to the claimed invention , or includes actuator <NUM> or <NUM>', in which case the FCS is not according to the claimed invention. In FCS <NUM>, OPFE <NUM> is tiltable by a first embodiment of a rotational spring based mechanism numbered <NUM>. Exemplarily, the mechanism may be based on a VCM. A full description of a rotational spring based VCM, with explanation of its method of operation, is provided in co-owned patent <CIT>. In FCS <NUM>, actuator <NUM> and VCM <NUM> are physically separate; in other embodiments, they may be connected or share parts, for example, by having a single unified plastic base.

<FIG> shows an embodiment numbered <NUM> of yet another FCS that includes an actuator <NUM>", in which case the FCS is according to the claimed invention , or includes actuator <NUM> or <NUM>', in which case the FCS is not according to the claimed invention. In FCS <NUM>, OPFE <NUM> is tiltable (rotatable) by a second embodiment of a rotational ball based mechanism numbered <NUM>. Exemplarily, the mechanism may be based on a VCM. A full description of a rotational ball guided VCM <NUM>, with explanation of the method of operation, is provided in <CIT>. In FCS <NUM>, actuator <NUM> and VCM <NUM> are physically separate, or they may be connected or share parts, for example, by having a single unified plastic base.

<FIG> shows an exemplary embodiment numbered <NUM> of a dual-aperture camera (dual-camera) that comprises a FCS such as FCS <NUM>, <NUM> or <NUM> and a non-folded (upright) camera <NUM>. In the exemplary embodiment shown, the FCS is similar to FCS <NUM>, but it should be understood that the FCS can be any other FCS disclosed herein. Upright camera <NUM> includes a lens <NUM> and an image sensor <NUM>. Lens <NUM> has an optical axis <NUM> that is substantially parallel to second optical axis <NUM>. Upright camera <NUM> may include other parts (not shown), such as an actuation mechanism for lens <NUM>, a shield, electrical circuitry, etc. The usage and operation of a dual-camera structure is described for example in co-owned <CIT>.

Any of the actuators disclosed above is included in a folded camera, which folded camera may be included together with an upright (non-folded) camera in a dual-aperture camera with folded lens, for example as described in co-owned <CIT>.

While this disclosure describes a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of such embodiments may be made. In general, the disclosure is to be understood as not limited by the specific embodiments described herein, but only by the scope of the appended claims.

Claim 1:
A folded camera, comprising:
a lens having a first optical axis and held in a lens holder, the lens receiving light folded from an optical path along a second optical axis that is substantially perpendicular to the first optical axis;
an optical path folding element (OPFE) that folds the light from the optical path along the second optical axis to an optical path along the first optical axis;
an image sensor; and
a voice coil motor (VCM) actuator for carrying and actuating the lens holder holding the lens, the actuator having a top side and a height in a direction parallel to the second optical axis,
characterised in that
the actuator is designed to allow insertion of the lens into the actuator from the top side, thereby reducing the height of the actuator.