A barrier opening and closing mechanism includes a refractive optical
system having a plurality of lens elements and disposed so as to refract
light substantially at right angles; a lens barrel holding the refractive
optical system; a rotary cam ring disposed concentrically with the lens
barrel, having a first cam groove, and rotating on an optical axis of
subject light having been refracted; a lens driving mechanism driving, in
a direction of the optical axis, at least one lens element included in the
refractive optical system engaged with the first cam groove; and a barrier
member protecting a most subject side lens element of the refractive
optical system. In the barrier opening and closing mechanism, the rotary
cam ring has, in a predetermined angle range on an outer surface thereof,
a second cam groove including a region extending obliquely to the optical
axis, a driving member is provided that has a cam follower engaged with
the second cam groove and is driven in a direction substantially parallel
to the optical axis, and the barrier is opened and closed by moving in
response to a movement of the driving member in the predetermined angle
range.
