Camera module and method for auto focus thereof

Patent metadata

Field	Value
Publication number	US-11002939-B2
Application number	US-201616300038-A
Country	US
Kind code	B2
Filing date	Jun 30, 2016
Priority date	Jun 30, 2016
Publication date	May 11, 2021
Grant date	May 11, 2021

Abstract

The present invention relates to an apparatus and a method for controlling auto focus of a camera module including a voice coil motor actuator. The camera module includes a sensing unit configured to sense a movement of the lens unit and a controller configured to control the movement of the lens unit based on a sensing signal sensed by the sensing unit. If an initial operation command is received, the controller moves the lens unit to an end point of a maximum movement range. If the lens unit is positioned at the end point of the maximum movement range, the controller compares the sensing signal sensed by the sensing unit with a predetermined reference signal to calculate a compensation value for an error. If a focus operation command is received, the controller can move the lens unit to a focus position based on the calculated compensation value and compensate for the focus position of the lens unit.

First claim

What is claimed is:

1. A camera module performing auto focus by moving a lens unit, the camera module comprising:
a sensing unit configured to sense a movement of the lens unit;
a sensor configured to sense whether a metal object is installed in vicinity of the camera module; and
a controller configured to:
control the movement of the lens unit based on at least a sensing signal sensed by the sensing unit,
move the lens unit to an end point of a maximum movement range in response to sensing, by the sensor, that the metal object is installed in the vicinity of the camera module,
compare the sensing signal sensed by the sensing unit with a predetermined reference signal to calculate a compensation value for an error in response to the moved lens unit positioned at the end point of the maximum movement range, and
move the lens unit to a focus position and compensate for the focus position of the lens unit based on the calculated compensation value in response to receiving a focus operation command.

2. The camera module of claim 1 , wherein the sensing unit includes a coil sensor configured to sense a current or voltage varying according to a distance from the lens unit.

3. The camera module of claim 1 , wherein the sensing unit is deployed in a manner of being apart from one side of the lens unit as much as a prescribed space and is positioned on a moving direction of the lens unit.

4. The camera module of claim 1 , wherein the maximum movement range corresponds to a moving distance between a first end point to which the lens unit is able to maximally move forward and a second end point to which the lens unit is able to maximally move backward.

5. The camera module of claim 4 , wherein the controller is configured to move the lens unit to the end point of the maximum movement range by:
calculating a first distance between a current position point of the lens unit and a first end point of the maximum movement range,
calculating a second distance between the current position point of the lens unit and a second end point of the maximum movement range, and
moving the lens unit to an end point closer to the lens unit among the first and second end points of the maximum movement range by comparing the first distance and the second distance with each other.

6. The camera module of claim 1 , wherein the controller is configured to calculate the compensation value for the error by calculating at least one of a first compensation value for compensating for a drive signal applied to the lens unit and a second compensation value for compensating for the sensing signal sensed by the sensing unit.

7. The camera module of claim 6 , wherein the controller is configured to calculate the first compensation value by:
comparing the sensing signal sensed by the sensing unit with the predetermined reference signal to check whether or not there is an error, and
when the error is checked, calculating the first compensation value for the error and storing the calculated first compensation value.

8. The camera module of claim 7 , wherein the first compensation value for the error is calculated only the checked error does not belong to a predetermined error range.

9. The camera module of claim 6 , wherein the controller is configured to calculate the second compensation value by:
compensating for the drive signal applied to the lens unit based on the calculated first compensation value,
applying the compensated drive signal to the lens unit,
checking whether or not there is an additional error by comparing the sensing signal sensed by the sensing unit with the predetermined reference signal,
when the additional error is checked, calculating the second compensation value for the additional error, and
storing the calculated second compensation value.

10. The camera module of claim 6 , wherein the controller is configured to compensate for the focus position of the lens unit by:
moving the lens unit to a focus position by compensating for the drive signal applied to the lens unit based on the calculated first compensation value, and
compensating for the focus position of the lens unit based on the calculated second compensation value.

11. A method for autofocusing in a camera module, the method comprising:
sensing a movement of a lens unit via a sensing unit;
controlling the movement of the lens unit based on at least a sensing signal sensed by the sensing unit;
moving the lens unit to an end point of a maximum movement range in response to sensing, by a sensor, that a metal object is installed in vicinity of the camera module;
comparing the sensing signal sensed by the sensing unit with a predetermined reference signal to calculate a compensation value for an error in response to the moved lens unit positioned at the end point of the maximum movement range; and
moving the lens unit to a focus position based on the calculated compensation value and compensating for the focus position of the lens unit in response to receiving a focus operation command.

12. The method of claim 11 , wherein the sensing unit includes a coil sensor configured to sense a current or voltage varying according to a distance from the lens unit.

13. The method of claim 11 , wherein the sensing unit is deployed in a manner of being apart from one side of the lens unit as much as a prescribed space and is positioned on a moving direction of the lens unit.

14. The method of claim 11 , wherein the maximum movement range corresponds to a moving distance between a first end point to which the lens unit is able to maximally move forward and a second end point to which the lens unit is able to maximally move backward.

15. The method of claim 14 , wherein moving the lens unit to the end point of the maximum movement range further comprises:
calculating a first distance between a current position point of the lens unit and a first end point of the maximum movement range,
calculating a second distance between the current position point of the lens unit and a second end point of the maximum movement range, and
moving the lens unit to an end point closer to the lens unit among the first and second end points of the maximum movement range by comparing the first distance and the second distance with each other.

16. The method of claim 11 , wherein calculating the compensation value for the error further comprises:
calculating at least one of a first compensation value for compensating for a drive signal applied to the lens unit and a second compensation value for compensating for the sensing signal sensed by the sensing unit.

17. The method of claim 16 , wherein calculating the first compensation value further comprises:
comparing the sensing signal sensed by the sensing unit with the predetermined reference signal to check whether or not there is an error, and
when the error is checked, calculating the first compensation value for the error and storing the calculated first compensation value.

18. The method of claim 17 , wherein the first compensation value for the error is calculated only when the checked error does not belong to a predetermined error range.

19. The method of claim 16 , wherein calculating the second compensation value further comprises:
compensating for the drive signal applied to the lens unit based on the calculated first compensation value,
applying the compensated drive signal to the lens unit, configured to check whether or not there is an additional error by comparing the sensing signal sensed by the sensing unit with the predetermined refere

Assignees

• Lg Electronics Inc

Inventors

• Kwon Youngman
• Kang Hyungjoo
• Kwon Sungdu
• Lee Jayong
• Park Haejin
• Hong Samnyol

Classifications

• G03B3/10 Primary

  Power-operated focusing · CPC title

• G02B7/105

  with movable lens means specially adapted for focusing at close distances · CPC title

• G01R15/18

  using inductive devices, e.g. transformers · CPC title

• G02B7/09 Primary

  adapted for automatic focusing or varying magnification · CPC title

• G01D5/202

  by movable a non-ferromagnetic conductive element (G01D5/2033 takes precedence) · CPC title