FOCUSING APPARATUS FOR OPTICAL PROJECTION DEVICE AND PROJECTION OPTICAL SYSTEM

摘要

A focus adjusting apparatus and a projection optical system of an optical projection device are provided to form a BFL(Back Focal Length) adjuster of a lens barrel with a few parts by supporting the lens barrel to a frame and adjusting BFL through an adjusting ring, and thus facilitate assembling and reduce the manufacturing cost. A focus adjusting apparatus of an optical projection device is composed of a frame(100) having a first screw unit(110) of first pitch; a lens barrel(200) movably installed at the frame and provided with a second screw unit(210) of second pitch; and an adjusting ring(300) having a third screw unit(311) corresponding to the first screw unit and a fourth screw unit(321) corresponding to the second screw unit, supporting the lens barrel to the frame, and moving the lens barrel in the direction of an optical axis.