ZOOM DRIVING ACTUATOR AND POSITION CONTROL METHOD FOR ZOOM DRIVING

Abstract

Disclosed herein is an actuator for driving zoom lenses, where the zoom actuator comprises a first carrier having attached thereto a first lens and movable along an optical axis; a second carrier having attached thereto a second lens and being capable of moving along the optical axis and running anterior or posterior to the first carrier; a housing enclosing the first and second carriers; a first magnet attached to the first carrier; a second magnet attached to the second carrier; a first coil unit mounted to the housing and facing the first magnet; a second coil unit mounted to the housing and facing the second magnet; and a plurality of balls; with at least one of said plurality of balls positioned between the housing and the first carrier; and at least one of said plurality of balls positioned between the housing and the second carrier.

Description

Claims

1. A zoom actuator, said zoom actuator comprising: a first carrier having a first lens attached thereto and movable along an optical axis;a second carrier having a second lens attached thereto, said second carrier being capable of moving anterior or posterior to the first carrier along the optical axis;a housing enclosing the first and second carriers;a first magnet attached to the first carrier;a second magnet attached to the second carrier;a first coil unit mounted to the housing and facing the first magnet;a second coil unit mounted to the housing and facing the second magnet; anda plurality of balls; with at least one of said plurality of balls positioned between the housing and the first carrier; and at least one of said plurality of balls positioned between the housing and the second carrier.

2. The zoom actuator according to claim 1, wherein the first carrier comprises: a first mount equipped with the first lens; anda first support fitted provided on the first mount, either left or right thereto,; andsaid first support extending longer along the optical axis than the first mount.

3. The zoom actuator according to claim 2, wherein the second carrier comprises: a second mount equipped with the second lens; anda second support fitted provided on a side of the second mount, either to the left or right thereof, but opposite the side the first support is fitted provided thereon, said second support extending longer than the second mount in a direction opposite to the first carrier along the optical axis.

4. The zoom actuator according to claim 1, wherein the first coil unit or the second coil unit consists of n coils (n being a natural number equal to or greater than 2) placed anterior or posterior relative to each other along the optical axis; andwherein the first magnet or the second magnet consists of n+1 magnetic poles facing respectively, the first coil unit or the second coil unit.

5. The zoom actuator according to claim 3, wherein the first carrier further comprises: a first rail formed on the first support; anda second rail formed on a region of the first mount unfitted with the first support being absent thereon, andwherein the second carrier further comprises: a third rail formed on the second support; anda fourth rail formed on a region of the second mount unfitted with the second support being absent thereon, andwherein the housing comprises: a first guide rail and a third guide rail, each of the first and third guide rails formed of plural individual rails and facing respectively, the first rail and the third rail, anda second guide rail and a fourth guide rail; each of the second and fourth guide rails facing respectively, the second and fourth rail, andwherein at least one of said plurality of balls is placed per each space spanning from each of the first to fourth rails to each of the respective first to fourth guide rails.

6. The zoom actuator according to claim 5, wherein each of the first to fourth guide rails is aligned parallel to the optical axis, andwherein the first guide rail is formed on one side of the housing, either to the left or right, and the third guide rail is formed on the other side of the housing devoid of the first guide rail, andwherein the second guide rail is formed on the an inner side of the third guide rail, and the fourth guide rail is formed on the an inner side of the first guide rail.

7. The zoom actuator according to claim 1, wherein the zoom actuator further comprises a plurality of Hall sensors disposed along the optical axis at positions differing in their distances displaced from the an interpolar boundary of the first magnet.

8. The zoom actuator according to claim 7, wherein the plurality of Hall sensors is arranged on a line running parallel to the optical axis, said plurality of Hall sensors being disposed either anterior or posterior to one another with respect to the optical axis.

9. The zoom actuator according to claim 7, wherein the first magnet has m magnetic poles (m being a natural number equal to or greater than 3) facing the first coil unit, andwherein the plurality of Hall sensors is configured to face together the a same pole out of the m magnetic poles when the first carrier is at the a default position.

10. A method for positional control of a zoom actuator, said zoom actuator comprising a first carrier having attached thereto a first lens and a first magnet and movable along an optical axis, a second carrier having attached thereto a second lens and a second magnet, said second carrier being capable of moving anterior or posterior to the first carrier along the optical axis, a first coil unit facing the first magnet, a second coil unit facing the second magnet, and a plurality of Hall sensors facing the first magnet, the method comprising the steps of: a signal input step for receiving an output signal from each of the plurality of Hall sensors;a position signal generating step for generating the a position signal for the first carrier by carrying out operations on the output signals; anda positional control step for controlling the a position of the first carrier using the position signal; andwherein the plurality of Hall sensors is disposed along the optical axis at positions differing in their distances displaced from the an interpolar boundary of the first magnet.

11. The method according to claim 10, wherein the first magnet has m magnetic poles (m being a natural number equal to or greater than 3) facing the first coil unit, andwherein at the a default position of the first carrier, the position signal generating step carries out on the position signals, either additive operation when the plurality of Hall sensors is facing together the a same magnetic pole of the first magnet, or a subtractive operation when each of the plurality of Hall sensors is facing a different magnetic pole of the first magnet.