Auto-focusing apparatus and method for camera

• US 8,036,524 B2
• Filed: 08/13/2008
• Issued: 10/11/2011
• Est. Priority Date: 09/03/2007
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Myoung-Won, Yoon, Young-Kwon, Lee, Hae-Sun, Lee, Yong-Gu
• Primary Examiner(s): Perkey; W. B.
• Assistant Examiner(s): ADAMS, BRET W
• Application Number:
  US12/190,779
• Publication Number:
  US 20090060487A1
• Time in Patent Office: 1,154 Days
• Field of Search: 396/133
• US Class Current: 396/133
• CPC Class Codes: G03B 13/36 Autofocus systems
• CPC Class Codes: G03B 3/10 Power-operated focusing
• CPC Class Codes: H04N 23/675 comprising setting of focusing regions

Abstract

Disclosed is an apparatus and method for auto-focusing a camera, which includes the steps of detecting an initial value of an encoder by measuring an initial position of a lens system, matching the measured initial value of the encoder with the initial position value of the lens system to be moved, measuring a distance value of a subject through a distance measuring sensor, determining a displacement that a focus lens has to be moved with respect to the measured distance value, and adjusting a position of the focus lens such that a position value of the focus lens actually moved is the same as the displacement value.

Claims

1. A method of auto focusing a camera, comprising the steps of:

measuring an initial value of an encoder corresponding to a first control signal necessary for initial movements of a focus lens;

measuring a distance value of a subject using a distance measuring sensor;

determining a displacement that a focus lens has to be moved based on the measured distance value; and

adjusting a position of the focus lens to be moved by a driver, such that a position value of the focus lens moved is substantially the same as the displacement value by transferring a second control signal according to the initial value of the encoder and the displacement value to the driver.

2. The method of auto-focusing as claimed in claim 1, wherein the measuring of the initial value of the encoder is performed by using a hall sensor of the encoder.

3. The method of auto-focusing as claimed in claim 2, wherein the initial value of the encoder may be detected as different initial values according to a mounting and position of a lens system.

4. The method of auto-focusing as claimed in claim 1, further comprising the step of:

determining a value of a driving current that corresponds to the initial value of the encoder.

5. The method of auto-focusing as claimed in claim 1, wherein the determining of the displacement that the focus lens has to be moved with respect to the measured distance value is achieved according to the equation:

x=f(L)=fA(L)=fB(L)=fC(L),

wherein L is a distance between the lens and the subject, x is a position of the lens at which the subject is in complete focus, and A, B, and C are driving currents of respective different driving units.

6. The method of auto-focusing as claimed in claim 1, wherein the step of measuring of the distance of the subject using the distance measuring sensor comprises:

measuring the distance, and

determining a displacement determines an optimum position.

7. The method of auto-focusing as claimed in claim 6, further comprising the step of:

linearly re-adjusting a position value of the lens system such that a scaling factor between a position of the lens actually moved and the displacement value fulfills the equation;

x=f(L)

where x equals a displacement, and L equal a distance between the camera and a subject.

8. The method of claim 1, wherein the determining step further comprises determining by a predetermined algorithm.

9. The method of claim 1, wherein the initial value is determined from at least one actual movement of the focus lens.

10. An apparatus for auto-focusing a camera, comprising:

an encoder, wherein an initial value of the encoder corresponds to a first control signal necessary for initial movements of a focus lens;

a distance measuring sensor for measuring a distance to a subject and transferring the measured distance value to an image signal processor (ISP);

the ISP receiving the initial value of the encoder and determining a displacement which a focus lens has to be moved based on the measured distance value received from the distance measuring sensor; and

a controller for adjusting a position value of the focus lens to be moved by a driver, such that a position of the moved focus lens is the same as the displacement value by transferring a second control signal according to the initial value of the encoder and the displacement value to the driver.

11. The apparatus of claim 10, wherein the controller comprises:

a feedback control circuit for linearly re-adjusting a position value of the focus lens such that a scaling factor between a position of the focus lens actually moved and the displacement value fulfills the equation;

x=f(L)

where x equals a displacement, and L equal a distance between the camera and a subject; and

a driver for moving the lens system by receiving the position value of the lens system re-adjusted at the feedback control circuit and controlling a motor of a driving unit adapted to move the focus lens.

12. The apparatus of claim 10, wherein the encoder includes a permanent magnet and a hall sensor.

13. The apparatus of claim 10, wherein the encoder is operative to move along with the movement of the focus lens.

14. The apparatus of claim 13, wherein the encoder transfers a point of time at which the focus lens starts to be moved by a driving unit to the ISP.

15. The apparatus of claim 14, wherein the encoder measures an actual movement distance of the focus lens, and transfers the measured movement distance to the controller.

16. The apparatus of claim 10, wherein the controller controls a driving unit irrespective of driving currents of similarly manufactured driving units.