Temperature based control of voice coil motor

Patent metadata

Field	Value
Publication number	US-9568704-B1
Application number	US-201514828431-A
Country	US
Kind code	B1
Filing date	Aug 17, 2015
Priority date	Aug 17, 2015
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

In some embodiments, the method includes measuring a first responsive voltage value for a first voltage drop between a first terminal attached to a first suspension spring of an actuator housing a voice coil motor for moving a lens assembly and a second terminal of the magnetic coil of the voice coil motor. In some embodiments, the method includes calculating a first resistance of the magnetic coil based at least in part upon the first voltage value and measuring a second responsive voltage value for a second voltage drop between the first terminal attached and the second terminal. In some embodiments, the method includes calculating a second resistance of the magnetic coil based at least in part upon the second responsive voltage value and calculating a relative temperature for the magnetic coil based at least in part upon the first resistance and the second resistance.

First claim

What is claimed is:

1. A system, comprising:
an actuator housing a voice coil motor for moving a lens assembly, comprising a first terminal and a second terminal, wherein
the first terminal is attached to a first suspension spring of the actuator housing the voice coil motor for moving the lens assembly, and
the second terminal is attached to a second suspension spring of a magnetic coil of the voice coil motor for moving the lens assembly;

a driver circuit configured for
controlling movement of and providing power to the voice coil motor, and
passing a first electrical signal having a first current value and a second electrical signal having a second current value to the voice coil motor;

a measuring circuit configured for
measuring a first responsive voltage value for a first voltage drop between the first terminal attached to the first suspension spring of the actuator housing the voice coil motor for moving the lens assembly and the second terminal attached to the second suspension spring of the magnetic coil of the voice coil motor, wherein
the first responsive voltage value is a voltage existing in response to passing the first electrical signal having the first current value through the first suspension spring to the magnetic coil, and

measuring a second responsive voltage value for a second voltage drop between the first terminal and the second terminal, wherein
the second responsive voltage value is a voltage existing in response to passing the second electrical signal having the second current value through the first suspension spring to the magnetic coil; and

a processor configured for:
calculating a first resistance of the magnetic coil based at least in part upon the first responsive voltage value;
calculating a second resistance of the magnetic coil based at least in part upon the second responsive voltage value, and
calculating a relative temperature for the magnetic coil based at least in part upon the first resistance and the second resistance.

2. The system of claim 1 , the driver circuit is further configured for:
adjusting a position of the lens assembly based at least in part upon the relative temperature.

3. The system of claim 1 , the driver circuit is further configured for:
moving the lens assembly by adjusting a current through the first suspension spring to compensate for the effect of the relative temperature to a position selected based at least in part upon the relative temperature, wherein the adjusting compensates for one or more of
changes in optical characteristics of the lens barrel in response to the relative temperature, and
changes in electrical characteristics of components of the actuator in response to the relative temperature.

4. The system of claim 1 , the driver circuit is further configured for:
controlling movement of and providing power to the voice coil motor creating the first electrical signal and the second electrical signal in a frequency range that does not overlap with a frequency range of used to controlling movement of the voice coil motor.

5. The system of claim 1 , the driver circuit is further configured for:
generating the first electrical signal and the second electrical signal as components of a probe pulse lasting between one-half millisecond and two milliseconds.

6. The system of claim 1 , the driver circuit is further configured for:
generating the first electrical signal and the second signal as components of a probe pulse having no direct current content.

7. The system of claim 1 , the driver circuit is further configured for:
generating the first electrical signal and the second signal as components of a bipolar probe pulse.

8. A method, comprising:
measuring a first responsive voltage value for a first voltage drop between a first terminal attached to a first suspension spring of an actuator housing a voice coil motor for moving a lens assembly and a second terminal of a magnetic coil of the voice coil motor, wherein
the second terminal is attached to a second suspension spring of the magnetic coil of the voice coil motor for moving the lens assembly, and
the first responsive voltage value is a voltage existing in response to passing a first electrical signal having a first current value through the first suspension spring to the magnetic coil;

calculating a first resistance of the magnetic coil based at least in part upon the first responsive voltage value;
measuring a second responsive voltage value for a second voltage drop between the first terminal attached and the second terminal, wherein
the second responsive voltage value is a voltage existing in response to passing a second electrical signal having a second current value through the first suspension spring to the magnetic coil;

calculating a second resistance of the magnetic coil based at least in part upon the second responsive voltage value; and
calculating a relative temperature for the magnetic coil based at least in part upon the first resistance and the second resistance.

9. The method of claim 8 , further comprising:
adjusting a position of the lens assembly based at least in part upon the relative temperature.

10. The method of claim 8 , further comprising:
moving the lens assembly by adjusting a current through the first suspension spring to compensate for the effect of the relative temperature to a position selected based at least in part upon the relative temperature, wherein the adjusting compensates for one or more of
changes in optical characteristics of the lens barrel in response to the relative temperature, and
changes in electrical characteristics of components of the actuator in response to the relative temperature.

11. The method of claim 8 , wherein
a driver circuit controlling movement of and providing power to the voice coil motor creating the first electrical signal and the second electrical signal in a frequency range that does not overlap with a frequency range of used to controlling movement of the voice coil motor.

12. The method of claim 8 , wherein
the first electrical signal and the second electrical signal are components of a probe pulse lasting between one-half millisecond and two milliseconds.

13. The method of claim 8 , wherein
the first electrical signal and the second signal are components of a probe pulse having no direct current content.

14. The method of claim 8 , wherein
the first electrical signal and the second signal are components of a bipolar probe pulse.

15. A non-transitory, computer-readable storage medium, storing program instructions that when executed by one or more computing devices cause the one or more computing devices to implement:
measuring a first responsive voltage value for a first voltage drop between a first terminal attached to a first suspension spring of an actuator housing a voice coil motor for moving a lens assembly and a second terminal attached to a second suspension spring of a magnetic coil of the voice coil motor for moving the lens assembly, wherein
the instructions to cause the one or more computing devices to implement measuring the first responsive voltage value further comprise instructions to cause the one or more computing devices to implement the first responsive voltage value that is a voltage existing in response to passing a first electrical signal having a first current value through the first suspension spring to the magnetic coil;

calculating a first resistance of the magnetic coil based at least in part upon the first responsive voltage value;
measuring a second responsive voltage value for a second voltage drop between the fi

Assignees

• Apple Inc

Inventors

• Wong Calvin K
• Hegde Shashikant G
• Baer Richard L

Classifications

• G01R19/10

  Measuring sum, difference or ratio · CPC title

• H02P25/028

  with four quadrant control · CPC title

• G01K7/36

  using magnetic elements, e.g. magnets, coils (magnetic elements per se H01F) · CPC title

• H02P29/0055

  Electricity · mapped topic

• G02B7/08 Primary

  adapted to co-operate with a remote control mechanism · CPC title