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EP-4220296-B1 - ZOOM DRIVING ACTUATOR AND POSITION CONTROL METHOD FOR ZOOM DRIVING

EP4220296B1EP 4220296 B1EP4220296 B1EP 4220296B1EP-4220296-B1

Inventors

  • PARK, CHUL SOON
  • KANG, IN SU
  • YEON, Je Seung
  • LEE, BYUNG CHEOL
  • CHO, HYEON IK

Dates

Publication Date
20260506
Application Date
20210909

Claims (10)

  1. A zoom actuator (100), said zoom actuator (100) comprising: a first carrier (120) having a first lens (60) attached thereto and movable along an optical axis; a second carrier (130) having a second lens (70) attached thereto, said second carrier (130) being capable of moving anterior or posterior to the first carrier (120) along the optical axis; a housing (110) enclosing the first and second carriers (120, 130); a first magnet (M1) attached to the first carrier (120); a second magnet (M2) attached to the second carrier (130); a first coil unit (C1) mounted to the housing (110) and facing the first magnet (M1); a second coil unit (C2) mounted to the housing (110) and facing the second magnet (M2); and a plurality of balls (B1, B2, B3, B4); with at least one of said plurality of balls (B1, B2, B3, B4) positioned between the housing (110) and the first carrier (120); and at least one of said plurality of balls (B1, B2, B3, B4) positioned between the housing (110) and the second carrier (130), characterized in that the first coil unit (C1) or the second coil unit (C2) 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; and the first magnet (M1) or the second magnet (M2) consists of n+1 magnetic poles facing respectively, the first coil unit (C1) or the second coil unit (C2).
  2. The zoom actuator according to claim 1, wherein the first carrier (120) comprises a first mount (121) equipped with the first lens (60); and a first support (123) fitted on the first mount (121), either left or right thereto; said first support (123) extending longer along the optical axis than the first mount (121).
  3. The zoom actuator according to claim 2, wherein the second carrier (130) comprises a second mount (131) equipped with the second lens (70); and a second support (133) fitted on a side of the second mount (131), either to the left or right thereof, but opposite the side the first support (123) is fitted thereon, said second support (133) extending longer than the second mount (131) in a direction opposite to the first carrier (120) along the optical axis.
  4. The zoom actuator according to claim 3, wherein the first carrier (120) further comprises: a first rail (125) formed on the first support (123); and a second rail (127) formed on a region of the first mount (121) unfitted with the first support (123), and wherein the second carrier (130) further comprises: a third rail (135) formed on the second support (133); and a fourth rail (137) formed on a region of the second mount (131) unfitted with the second support (133), and wherein the housing (110) comprises: a first guide rail (111) and a third guide rail (113), each of the first and third guide rails (111, 113) formed of plural individual rails and facing respectively, the first rail and the third rail (125, 135), and a second guide rail (112) and a fourth guide rail (114); each of the second and fourth guide (112, 114) rails facing respectively, the second and fourth rail (127, 137), and wherein at least one of said plurality of balls (B1, B2, B3, B4) is placed per each space spanning from each of the first to fourth rails (125, 127, 135, 137) to each of the respective first to fourth guide rails (111, 112, 113, 114).
  5. The zoom actuator according to claim 4, wherein each of the first to fourth guide rails (111, 112, 113, 114) is aligned parallel to the optical axis, and wherein the first guide rail (111) is formed on one side of the housing (110), either to the left or right, and the third guide rail (113) is formed on the other side of the housing (110) devoid of the first guide rail (111), and wherein the second guide rail (112) is formed on the inner side of the third guide rail (113), and the fourth guide rail (114) is formed on the inner side of the first guide rail (111).
  6. The zoom actuator according to claim 1, wherein the zoom actuator (100) further comprises a plurality of Hall sensors (140A-1, 140A-2) disposed along the optical axis at positions differing in their distances displaced from an interpolar boundary of the first magnet (M1).
  7. The zoom actuator according to claim 6, wherein the plurality of Hall sensors (140A-1, 140A-2) is arranged on a line running parallel to the optical axis, said plurality of Hall sensors (140A-1, 140A-2) being disposed either anterior or posterior to one another with respect to the optical axis.
  8. The zoom actuator according to claim 6, wherein the first magnet (M1) has m magnetic poles (m being a natural number equal to or greater than 3) facing the first coil unit (C1), and wherein the plurality of Hall sensors (140A-1, 140A-2) is configured to face together the same pole out of the m magnetic poles when the first carrier (120) is at the default position.
  9. A method for positional control of a zoom actuator (100), said zoom actuator (100) comprising a first carrier (120) having attached thereto a first lens (60) and a first magnet (M1) and movable along an optical axis, a second carrier (130) having attached thereto a second lens (70) and a second magnet (M2), said second carrier (130) being capable of moving anterior or posterior to the first carrier (120) along the optical axis, a first coil unit (C1) facing the first magnet (M1), a second coil unit (C2) facing the second magnet (M2), and a plurality of Hall sensors (140A-1, 140A-2) facing the first magnet (M1), the method comprising the steps of: a signal input step for receiving an output signal from each of the plurality of Hall sensors (140A-1, 140A-2); a position signal generating step for generating the position signal for the first carrier (120) by carrying out operations on the output signals; and a positional control step for controlling the position of the first carrier (120) using the position signal; and wherein the plurality of Hall sensors (140A-1, 140A-2) is disposed along the optical axis at positions differing in their distances displaced from the interpolar boundary of the first magnet (M1).
  10. The method according to claim 9, wherein the first magnet (M1) has m magnetic poles (m being a natural number equal to or greater than 3) facing the first coil unit (C1), and wherein at the default position of the first carrier (120), the position signal generating step carries out on the position signals, either additive operation when the plurality of Hall sensors (140A-1, 140A-2) is facing together the same magnetic pole of the first magnet (M1), or a subtractive operation when each of the plurality of Hall sensors (140A-1, 140A-2) is facing a different magnetic pole of the first magnet (M1).

Description

TECHNICAL FIELD The present disclosure relates to a zoom actuator and a method for positional control. More particularly, the present disclosure relates to inter alia, an actuator capable of driving lenses over extended strokes with improved precision. BACKGROUND ART As the hardware technology for image processing has been developed and the user needs for image shooting have increased, functions such as autofocus (AF) and optical image stabilization (OIS) have been applied to a camera module or the like, mounted to a portable terminal such as a cellular phone and a smart phone as well as an independent camera device. Recent years have seen actuators for zoom lens that supports variable adjustment features including the object size by tuning the focal length through such functions as zoom-in and zoom-out. In certain models of actuators, further diversification in implementing zoom has been attainable through combinations in the relative positions among plural lenses (lens assembly). Since zoom lenses have longer or extended distances of movement along the optical axis (also referred to as stroke) than ordinary lenses, the actuators used for driving zoom lens must accordingly be designed to exert sufficient driving force. Furthermore, their design should enable accurate detection and feedback control of the corresponding position of the zoom lenses across the entire stroke range. Actuators known in the art, however, had an element for driving carriers simply installed in multiple numbers, but independent of one another. Thus, although they were capable of functions based on relative positioning of the lenses such as zooming and auto-focusing, their abilities were lacking in precisely detecting the position of the carrier (lens) of interest and utilizing such information for feedback control across the extended moving distances, limited by their reliance on conventional application of Hall sensors. In addition, although art-known actuators met with some degree of success in fortifying the driving force by placing magnets at both ends of the carrier, this approach led to inflated actuator dimensions because room for movement has to be set aside for each carrier in designing actuator space. Accordingly, there were big obstacles in the use of prior art actuators in applications such as smart phones where size or volume was a significant issue. In addition, prior art actuators were incapable of precisely controlling the driving of individual carriers, especially in such intervals where multiple carriers were in proximity. Prior art actuators were configured to comprise plural number of carriers, each with a magnet attached, which in turn was disposed to face a coil for generating electromagentic force in that magnet. This setup caused magnetic interference generated from the interaction with the other coil or the other magnet, posing another unsolved technical problem. US 2020/137274 A1 discloses a zoom actuator with the features of the preamble of present claim 1. DISCLOSURE Technical Problem The present disclosure has been contemplated to solve the aforementioned problems of the related art in the context mentioned above. It is a technical goal of the present invention to achieve a more effective utilization of space for the actuator. It is another technical goal to provide a zoom actuator capable of accurately detecting position over an extended stroke range leading to an improved precision in zoom driving by means of a plurality of interactive Hall sensors. These and other objects and advantages of the present disclosure may be understood from the following detailed description and will become more fully apparent from the exemplary embodiments of the present disclosure. Also, it will be easily understood that the objects and advantages of the present disclosure may be realized by the means shown in the appended claims and combinations thereof. Technical Solution To achieve the technical goals mentioned above, in one aspect of the present disclosure is provided a zoom actuator which comprises a first carrier having a first lens attached thereto and movable along an optical axis; a second carrier having a second lens attached thereto with the second carrier being capable of moving along the optical axis and running anterior or posterior to the first carrier; a housing to enclose 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 and mounted to the housing and facing the second magnet; and a plurality of balls, in which at least one of said plurality of balls is positioned between the housing and the first carrier and at least one of said plurality of balls is positioned between the housing and the second carrier. In a particular embodiment, the first carrier comprises a first mount equipped with the first lens; a first support fitted on the first mount