Abstract: There is disclosed herein an automatic focusing system including an optical system having a focus lens, a zoom lens and an image pickup device for converting a light beam from an object into a corresponding electrical signal. The automatic focusing system comprising a filter for deriving a predetermined component of the electrical signal, a detector for detecting a focus voltage of the predetermined component and a drive circuit for moving the focus lens and zoom lens in the directions of the optical axis of the optical system. Also included in the focusing system is a control unit which moves the focus lens through the drive circuit to bring the focus lens into the fous positon and, when the focus position is not taken in a predetermiend movable range, moves the zoom lens toward the wide-angle side before again moving the focus lens so as to take the focus position.

Abstract: An expansive demolition agent prepared by crushing a clinker for manufacturing powdered expansive demolition agent obtained by sintering, which is capable of hydrating and expanding in a hole drilled in a brittle material to demolish the brittle material, the maximum particle diameter of the agent being one-third or less the diameter of the hole, and containing 10% or less of fine particles having a particle diameter of 0.3 mm or less.

Abstract: A video camera comprises a camera body, a view finder part provided on one side surface of the camera body, a battery receiving part located on the one side surface of the camera body, and a battery which is detachably attached to the battery receiving part to function as a grip of the video camera.