BACKGROUND

Technical Field

The present disclosure relates to a lens assembly driving apparatus and a photographing module. More particularly, the present disclosure relates to a lens assembly driving apparatus and a photographing module applicable to a portable electronic device.

Description of Related Art

With the popularity of personal electronic products and mobile communication products having camera functionalities, such as smart phones and tablet personal computers, the demand for compact electronic devices with high resolution and high image quality also increases significantly.

Nowadays, a lens assembly employed in an electronic device normally adopts a voice coil motor (VCM) as a driving apparatus for providing autofocus function. With an electromagnetic force generated by the interaction of magnets and a coil, and with the degree of freedom and the restoring force provided by springs which are required by the movement of the carrier carrying the lens assembly, the carrier is driven by the voice coil motor to bring the lens assembly to move along a direction parallel to an optical axis, so that the autofocus functionality of the lens assembly can be achieved.

However, a conventional driving apparatus usually adopts a single annular magnet, which has a drawback of uneven distribution of magnetic flux. Moreover, when assembling the annular magnet and a metal yoke, the assembling position may be affected by the magnet force due to the dimensional tolerance. As a result, the assembling position is unstable.

Therefore, how to improve the evenness of the magnetic flux distribution and assembling precision of the driving apparatus so as to enhance the autofocus function of the lens assembly, and how to reduce the volume of the driving apparatus so as to accord with the compact trend of current electronic devices, have been the goal of the related industries.

SUMMARY

According to one aspect of the present disclosure, a lens assembly driving apparatus includes a holder, a metal yoke, a carrier, a lens assembly, a magnet set, a coil and at least one elastic element. The holder has an opening. The metal yoke is coupled with the holder, and the metal yoke has a through hole. The carrier is movably disposed in the metal yoke. The carrier includes an object-side portion and at least three inner surfaces. The object-side portion has an object-side central hole. Each of the inner surfaces has a diameter. The diameters of the inner surfaces are different from each other. Each of the diameters of the inner surfaces is greater than a diameter of the object-side central hole. The lens assembly has an optical axis. The optical axis is corresponding to the object-side central hole. The lens assembly includes at least three lens elements. Each of the lens elements has an outer diameter. The outer diameters of the lens elements are different from each other. The lens assembly is coupled in the carrier, and a movement of the lens assembly relative to the holder is according to a movement of the carrier. The magnet set includes only two magnets. The two magnets are opposite to each other and are fixed inside the metal yoke. Each of the two magnets includes a concave arc structure. The coil surrounds and is fixed at an exterior of the carrier. The coil is corresponding to the two magnets. The elastic element is coupled with the carrier and the holder. The concave arc structure of each of the two magnets has a concave arc center. In each of the two magnets, when an included angle between two connecting lines of two ends of the concave arc structure and the concave arc center is θ, the following condition is satisfied:
95 degrees<θ<175 degrees.

According to another aspect of the present disclosure, a photographing module includes the lens assembly driving apparatus according to the aforementioned aspect.

According to further another aspect of the present disclosure, an electronic device includes the photographing module according to the aforementioned aspect.

According to yet another aspect of the present disclosure, a lens assembly driving apparatus includes a holder, a metal yoke, a carrier, a lens assembly, a magnet set, a coil and at least one elastic element. The holder has an opening. The metal yoke is coupled with the holder, and the metal yoke has a through hole. A side wall of the metal yoke includes at least one plane structure and at least one convex curved structure. The carrier is movably disposed in the metal yoke and includes an object-side portion. The object-side portion has an object-side central hole. The lens assembly has an optical axis. The optical axis is corresponding to the object-side central hole. The lens assembly includes at least three lens elements. Each of the lens elements has an outer diameter. The outer diameters of the lens elements are different from each other. The lens assembly is coupled in the carrier, and a movement of the lens assembly relative to the holder is according to a movement of the carrier. The magnet set includes a plurality of magnets. The magnets are corresponding to each other and are fixed inside the metal yoke. Each of the magnets includes a concave arc structure. The coil surrounds and is fixed at an exterior of the carrier. The coil is corresponding to the magnets. The elastic element is coupled with the carrier and the holder. The lens assembly driving apparatus is a non-threaded driving apparatus. When a total number of the plane structure and the convex curved structure is N, the following condition is satisfied:
3<N<7.

