Abstract: Two prisms comprising a lower stage of four cylindrical members which refract and enlarge a beam in one dimension, and comprising an upper stage of four identical cylindrical members revolved 90.degree. on the vertical axis so as to refract and enlarge the beam in the other dimension, thereby producing a magnified whole image of the object. The cylindrical members are longitudinal segments of hollow and whole cylinders, and each member has a planar face opposite a cylindrical face. Three of the members can be revolved so as to place the planar face at various angles to the beam and thereby produce a range of magnification from 0 to 50.times. when two stages are used and from 0 to 2500.times. when four stages are used.

Abstract: A lens drive mechanism comprising a lens mount, a basic barrel having a compartment defined therein for accommodating the lens mount for movement in a direction parallel to the optical axis, a pin member, and a generally semicircular cross-sectioned cam member mounted so as to cover the basic barrel for rotation about the optical axis and having a cam groove defined therein with the free end of the pin member engaged in the cam groove.

Abstract: An optical lens moving mechanism for zoom lens systems using a plane cam is disclosed. A lens system having an optical axis comprises at least two lens groups. A first lens holder and a second lens holder which respectively hold the two lens groups are moved along a guide parallel with the optical axis by a rotational movement of the plane cam which moves on a plane parallel with the optical axis, to zoom the lens system. The mechanism further includes a zooming motor, a position detector, and a controller to control the rotation of the motor, according to the zooming position of the lens system, to achieve a uniform zooming speed.

Abstract: A helicoid thread mechanism which comprises a male helically threaded tube and a female helically threaded tube is provided with a helically threaded block for threadedly engaging the female tube onto the male tube. A sliding frictional contact noise which is produced between the two tube members when they engage with each other is eliminated by suitable selection on the helically threaded shape and the material of the block.