Autofocus device and digital camera

1. An autofocus device comprising:

a lens drive system for translating a lens;

a first in-focus position detector for detecting a first in-focus position while translating the lens in a first direction by the lens drive system;

a second in-focus position detector for detecting a second in-focus position while translating the lens in a direction opposite to the first direction by the lens drive system, the second in-focus position detector operating after the first in-focus position is detected; and

a backlash detector for detecting a backlash in the lens drive system according to the first and the second in-focus positions;

wherein an amount of lens translation to an in-focus position is corrected according to previously detected backlash.

2. The autofocus device according to claim 1 , further comprising:

an imager for capturing an image through the lens; and

a contrast detector for detecting a contrast of an image captured by the imager;

wherein the first and second in-focus position detectors capture images at different positions of the lens as the lens is translated and the contrast detector detects contrasts of the images, so that a peak of the contrasts detected by the first in-focus position detector corresponds to the first in-focus position and a peak of the contrasts detected by the second in-focus position detector corresponds to the second in-focus position.

3. The autofocus device according to claim 1 , wherein detecting of backlash, by said backlash detector, and a learning process are performed during an autofocus operation.

4. The autofocus device according to claim 3 , wherein the learning process is carried out in consideration of at least one of a lens type, a drive direction, a drive speed and an attitude of a camera body.

5. The autofocus device according to claim 1 , wherein a drive amount of the lens drive system for adjusting a position of the lens from the exceeding position to the in-focus position is determined based upon an exceeding rotation and an amount of the backlash, the exceeding position being a position at which the first in-focus position is detected when the lens is translated in the first direction.

6. An autofocus device comprising:

a lens drive system for translating a lens;

a first in-focus position detector for detecting a first in-focus position while translating the lens in a first direction by the lens drive system;

a second in-focus position detector for detecting a second in-focus position while translating the lens in a direction opposite to the first direction by the lens drive system, the second in-focus position detector operating after the first in-focus position is detected; and

a backlash detector for detecting a backlash in the lens drive system according to the first and the second in-focus positions,

wherein at least one of the backlash and a drive amount from an exceeding position to the in-focus position is subjected to a learning process, the exceeding position being a position at which the first in-focus position is detected when the lens is translated in the first direction.

7. The autofocus device according to claim 6 , wherein the learning process is carried out in consideration of at least one of a lens type, a drive direction, a drive speed and an attitude of a camera body.

8. The autofocus device according to claim 6 , wherein detecting of backlash, by said backlash detector, and a learning process are performed during an autofocus operation.

9. The autofocus device according to claim 6 , wherein a drive amount of the lens drive system for adjusting a position of the lens from the exceeding position to the in-focus position is determined based upon an exceeding rotation and an amount of the backlash.

10. An autofocus device comprising:

a lens drive system for translating a lens;

a first in-focus position detector for detecting a first in-focus position while translating the lens in a first direction by the lens drive system;

a second in-focus position detector for detecting a second in-focus position while translating the lens in a direction opposite to the first direction by the lens drive system, the second in-focus position detector operating after the first in-focus position is detected; and

a backlash detector for detecting a backlash in the lens drive system according to the first and the second in-focus positions,

wherein the first and second in-focus position detectors comprise a focusing mechanism using a phase-difference detection method.

11. The autofocus device according to claim 10 , wherein detecting of backlash, by said backlash detector, and a learning process are performed during the autofocus operation.

12. The autofocus device according to claim 11 , wherein the learning process is carried out in consideration of at least one of a lens type, a drive direction, a drive speed and an attitude of a camera body.

13. The autofocus device according to claim 10 , wherein a drive amount of the lens drive system for adjusting a position of the lens from the exceeding position to the in-focus position is determined based upon an exceeding rotation and an amount of the backlash, the exceeding position being a position at which the first in-focus position is detected when the lens is translated in the first direction.

14. A digital camera comprising:

a lens barrel including a lens system

a lens drive system for translating a lens of the lens system;

a first in-focus position detector for detecting a first in-focus position while translating the lens in a first direction by the lens drive system;

a second in-focus position detector for detecting a second in-focus position while translating the lens in an opposite direction with respect to the first direction by the lens drive system, the second in-focus position detector operating after the first in-focus position is detected; and

a backlash detector for detecting a backlash in the lens drive system according to the first and the second in-focus positions

wherein an amount of lens translation to an in-focus position is corrected according to previously detected backlash.

15. The digital camera according to claim 14 , wherein detecting of backlash, by said backlash detector, and a learning process are performed during the autofocus operation.

16. The digital camera according to claim 15 , wherein the learning process is carried out in consideration of at least one of a lens type, a drive direction, a drive speed and an attitude of a camera body.

17. The digital camera according to claim 14 , wherein a drive amount of the lens drive system for adjusting a position of the lens from the exceeding position to the in-focus position is determined based upon an exceeding rotation and an amount of the backlash, the exceeding position being a position at which the first in-focus position is detected when the lens is translated in the first direction.

18. A method comprising:

translating a lens;

detecting a first in-focus position while translating the lens in a first direction by a lens drive system;

detecting a second in-focus position while translating the lens in a direction opposite to the first direction by the lens drive system, the second in-focus position detecting operating after the first in-focus position is detected; and

detecting a backlash in the lens drive system according to the first and the second in-focus positions

wherein an amount of lens translation to an in-focus position is corrected according to previously detected backlash.

19. The method according to claim 18 , wherein the detecting of backlash and a learning process are performed during an autofocus operation.

20. The method according to claim 18 , wherein a drive amount of the lens drive system for adjusting a position of the lens from an exceeding position to the in-focus position is determined based upon an exceeding rotation and an amount of the backlash, the exceeding position being a position at which the first in-focus position is detected when the lens is translated in the first direction.