Automatic focusing device

An automatic focusing device comprising:

• a zoom lens system including means for forming a path of substantially parallel rays in a photographing optical system when a photographing lens is focused on an object to be photographed;
• a prism spectroscope with a half-mirror surface disposed in the path of said parallel rays;
• shielding means for preventing the interference of said two light beams which are split by said half-mirror surface of said prism spectroscope;
• a pair of detecting arrays disposed at a position in conjugation with the position of the image pickup plane of said photographing optical system, so as to simultaneously receive two light beams which pass through different portions of a focus lens in said photographing optical system and are split by said half-mirror surface;
• signal processing means for receiving and processing a relative positional relation of two video signals corresponding to the intensity distributions of the images of said object which are detected by said pair of detecting arrays and producing a corresponding output signal;
• and
• drive means for moving said photographing optical system or an image pickup plane to the focusing position of said object according to an output signal of said signal processing means.

An automatic focusing device comprising:

• a detecting array for detecting the intensity distribution of the image of an object to be photographed which is formed by a light beam passing a predetermined portion of a photographing optical system and producing a video signal corresponding to said intensity distribution;
• an image pickup tube having an image pickup surface on which the image of said object is formed by the entire light beam passing said photographing optical system;
• extracting circuit means for extracting a video signal corresponding to the intensity distribution of a part corresponding to said detecting array of the image of said object which is formed on said image pickup surface;
• signal processing means for comparing and processing a relative positional relation of said video signals corresponding to said two intensity distributions and producing a corresponding output signal;
• and
• drive means for moving said photographing optical system to the focusing position of said object according to an output signal of said signal processing means.

An automatic focusing device comprising:

• a zoom lens system including means for forming substantially parallel rays in a photographing optical system when a photographing lens is focused on an object to be photographed;
• a spectroscope with a pair of half-mirror surfaces disposed in the path of said parallel rays;
• an image pickup tube with a pair of blanking parts which simultaneously receives two light beams which pass different portions of a focus lens in said photographing optical system and, after being split by said half-mirror surfaces, directed in parallel with the optical axis of said photographing optical system;
• signal processing means for detecting and processing the intensity distributions of the images which are formed on said blanking parts by said two light beams and producing a corresponding output signal;
• and
• drive means for moving said photographing optical system to the focusing position of said object according to an output signal of said signal processing means.