Abstract: A lens barrel for use in an optical instrument such as a camera or other imaging device has a circuit board having an aperture which allows a light beam from a photographed object to pass therethrough. The aperture has a substantially polygonal shape which substantially coincides with an area of the light beam effective in forming an image on a recording portion including a film plane or an image sensing plane. The peripheral portion of the circuit board around the aperture provides a mounting area which is large enough to mount a large-sized IC chip which may include a zooming data processing circuit and other control circuits.

Abstract: A lens mounting including a distance adjusting ring responsive to a signal representing the object to an in-focus position, and provided with an intermediate stopper retractable from an intermediate point in the range of rotation of the aforesaid distance adjusting ring.