Patent ID: 7372637

Claim:
A focusing unit comprising: a screw body having a male thread in an outer perimeter face thereof; a tubular nut body having an inner perimeter face and an outer perimeter face with a female thread in the inner perimeter face to engage with the screw body, and having a cam follower on the outer perimeter face; a cam ring holding the screw body rotatably and axially non-movable relative to the cam ring, receiving said tubular nut body inside the cam ring slidably, and comprising a perimeter wall, wherein the cam ring has a groove for receiving said cam follower, formed in the perimeter wall, comprising a first long groove axially parallel with the tubular nut body, having a first axial direction end and a second axial direction end, and a second long groove having a first inclined end and a second inclined end, wherein the first inclined end is connected to the second axial direction end so that an angle between the first long groove is more than a right angle and the cam follower is able to follow the first long groove and the second long groove smoothly; and an optical member driver fixedly connected to the tubular nut body, axially movable by translating rotation of the screw body via the tubular nut body to movement in the axial direction, said optical member driver further connected to an optical member.