Lens barrel and cam mechanism

1. A lens barrel including a plurality of cam grooves and a plurality of cam followers, the lens barrel comprising:

an optical system for forming an optical image of an object;

a first tube for supporting at least one lens included in the optical system; and

a second tube disposed one of inside and outside the first tube,

wherein

the first tube includes a second cam groove and a third cam follower in a side surface thereof on which the second tube is disposed,

the second tube includes a second cam follower engaging with the second cam groove and includes a third cam groove engaging with the third cam follower, and

at least one of the second cam groove and the third cam groove includes a nonlinear section having a nonlinear shape, in the nonlinear section, at least one of the pairs among the pair of the second cam follower and the second cam groove, and the pair of the third cam follower and the third cam groove is engaged in a state in which, while the other one of such pairs is engaged at the same time.

2. The lens barrel according to claim 1 , wherein at least one of the second cam groove and the third cam groove includes a section, in which a wall surface is disposed in one side of an optical axis direction and no wall surface is disposed in the other side.

3. The lens barrel according to claim 1 , wherein a maximum value of a width of a portion of the second cam follower where the second cam follower engages with the second cam groove is different from a maximum value of a width of a portion of the third cam follower where the third cam follower engages with the third cam groove.

4. A cam mechanism including a plurality of cam grooves and a plurality of cam followers, the cam mechanism comprising:

a first tube including, in one of an outer side surface thereof and an inner side surface thereof,

a second cam groove, and

a third cam follower; and

a second tube disposed on the one of the side surfaces of the first tube, the second tube including

a third cam groove engaging with the third cam follower, and

a second cam follower engaging with the second first cam groove,

wherein at least one of the second cam groove and the third cam groove includes a nonlinear section having a nonlinear shape, in the nonlinear section, at least one of the pairs among the pair of the second cam follower and the second cam groove, and the pair of the third cam follower and the third cam groove is engaged in a state in which, while the other one of such pairs is engaged at the same time.

5. The cam mechanism according to claim 4 , wherein a maximum value of a width of a portion of the second cam follower where the second cam follower engages with the second cam groove is smaller than a maximum value of a width of a portion of the third cam follower where the third cam follower engages with the third cam groove.

6. The cam mechanism according to claim 5 , wherein, when the second tube rotates with respect to the first tube to move with respect to the first tube in a direction of an axis of rotation, a part of a region in which the second cam follower moves is located outside an end portion of the first tube in the direction of the axis of the rotation.

7. The cam mechanism according to claim 6 , wherein, when the second cam follower is located at the part of the region, the second cam follower comes in contact with the first tube, upon being subjected to a force in a direction in which the first tube and the second tube are collapsed.

8. A lens barrel comprising:

an optical system for forming an optical image of an object;

a first tube for supporting at least one lens included in the optical system; and

a second tube disposed one of inside and outside the first tube,

wherein

one of the first tube and the second tube includes a cam groove;

the other of the first tube and the second tube includes a cam follower engaging with the cam groove;

the first tube includes a first projection protruding toward the second tube;

the second tube includes a second projection protruding toward the first tube;

the first tube includes a first wall formed along a moving track of the second projection that moves when the cam follower moves along the cam groove; and

the second tube includes a second wall formed along a moving track of the first projection that moves when the cam follower moves along the cam groove.

9. A lens barrel including a plurality of cam grooves and a plurality of cam followers, the lens barrel comprising:

a first tube; and

a second tube disposed one of inside and outside the first tube;

wherein:

the first tube includes a second cam groove and a third cam follower in a side surface thereof on which the second tube is disposed,

the second tube includes a second cam follower engaging with the second cam groove and includes a third cam groove engaging with the third cam follower, and

at least one of the second cam groove and the third cam groove includes a section, in which a wall surface is disposed in one side of an optical axis direction and no wall surface is disposed in the other side.