Abstract: In an automatic aperture control circuit for an automatic diaphragm lens of a CCTV camera, having a ballast power source circuit II which stabilizes an externally supplied power source, an input signal detector III, an output circuit IV, and an intermediate power source circuit V, in which opening and closing operations of a diaphragm is controlled in accordance with a diaphragm drive signal which is obtained from an image signal or a spurious signal, output from a CCTV camera, using an iris servo-meter apparatus VI, a surge prevention device is inserted between the portion of a power line P1 of the ballast power source circuit II on the input side and a ground line, and a low impedance fixed resistor R1 is inserted in series between a connection point of the power line P1 to the surge absorber and the reverse connection prevention diode D1 of the ballast power source II.

Abstract: A travel-limit circuit having a DC motor for a lens by which the endurance of the motor can be improved while at the same reducing the rebound due to the inertia of the moving body at a travel extremity. The travel-limit circuit has a lens motor that drives, e.g., zoom lens groups. Limits which detect whether the lens group has reached their travel extremities at which mechanical stoppers are provided. The motor driving circuit, which drives the lens motor and the limit switches, activates a short break by short circuiting the pair of input terminals on the lens motor via diodes while cutting current flow from the motor driving circuit for the lens motor upon detection that the lens groups have reached their travel limit.

Abstract: In a concentric ND filter in which multi-layered circular ND filter elements whose diameter is decreased stepwise toward the uppermost layer from the lowermost layer are concentrically provided on a first transparent substrate, a surrounding space of the concentrically multi-layered ND filter elements defined by and between the surface of the transparent substrate and the surface of the central ND filter layer of the smallest diameter is filled with a transparent adhesive.