HALL-EFFECT BASED LINEAR MOTOR CONTROLLER

• US 20120008929A1
• Filed: 09/22/2011
• Published: 01/12/2012
• Est. Priority Date: 10/01/2007
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: David, Paul, Milano, Shaun D.
• Granted Patent: US 9,784,594 B2
• Time in Patent Office: Days
• US Class Current: 396/125
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G02B 7/102 controlled by a microcomputer cameras with interchangeable lenses G03B17/14
• CPC Class Codes: G03B 13/36 Autofocus systems
• CPC Class Codes: H02K 11/215 Magnetic effect devices, e.g. Hall-effect or magneto-resistive elements
• CPC Class Codes: H02K 41/0352 Unipolar motors
• CPC Class Codes: H02P 25/034 Voice coil motors voice coil motors driven by DC H02P7/025
• CPC Class Codes: H02P 25/06 Linear motors
• CPC Class Codes: H02P 25/066 of the stepping type
• CPC Class Codes: H02P 6/006 Controlling linear motors
• CPC Class Codes: H04N 23/54 Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method

Abstract

A linear motion control device for use in a linear control system is presented. The linear motion control device includes a coil driver to drive a coil that, when driven, effects a linear movement by a motion device having a magnet. The linear motion control device also includes a magnetic field sensor to detect a magnetic field associated with the linear movement and an interface to connect an output of the magnetic field sensor and an input of the coil driver to an external controller. The interface includes a feedback loop to relate the magnetic field sensor output signal to the coil driver input.

Claims

1. A method of focusing a lens in a camera module, comprising:

determining a displacement range for the lens;

using the displacement range to request a desired displacement of the lens; and

providing the request to a device that causes displacement of the lens by a voice coil actuator, by using an internal control loop to adjust a drive current supplied to a coil of the voice coil actuator.

2. The method of claim 1, further comprising:

causing capture of an image projected by the lens in a frame;

determining if the frame is a maximum frame;

if the frame is determined not to be a maximum frame, advancing to a next frame and returning to the step of using the displacement range to request a desired displacement of the lens.

3. The method of claim 2, further comprising:

if the frame is determined to be the maximum frame, determining which frame is in focus;

selecting the frame that is determined to be in focus; and

causing a picture to be taken for the selected frame.