Patent ID: 8289626

Claim:
A rotationally extendable structure of a lens barrel comprising: a stationary ring; a rotational ring, which is supported by said stationary ring to move in an optical axis direction while rotating, said rotational ring including a peripheral gear at the rear end thereof with respect to the optical axis direction; and a rotational-ring drive gear, which is rotatably driven by a motor that is supported by said stationary ring, wherein said rotational-ring drive gear includes a long gear portion, which has a length, in the optical axis direction, sufficient to mesh with said peripheral gear over an entire moving range of said rotational ring in the optical axis direction, and a large-diameter gear portion provided at the rear end of said long gear portion, wherein a rotational driving force of said motor is transmitted to and drives said large-diameter gear portion, and wherein said rotational ring is provided, at the rear end thereof with a large-diameter-gear accommodation recess, said large-diameter gear portion being accommodatable into said large-diameter-gear accommodation portion; wherein when said rotational ring is moved to a rearward movement extremity in the optical axis direction, said large-diameter gear portion of said rotational-ring drive gear enters into said large-diameter-gear accommodating recess so that said large-diameter gear portion is positioned, with respect to the optical axis direction, at a position coincident with a position of said peripheral gear.