Automatic focus control system for video camera

• US 4,609,944 A
• Filed: 05/24/1984
• Issued: 09/02/1986
• Est. Priority Date: 05/25/1983
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Kato, Yukihiro, Nakada, Yasuo
• Primary Examiner(s): Rubinson, Gene Z.
• Assistant Examiner(s): BRINICH, STEPHEN M
• Application Number:
  US06/613,571
• Time in Patent Office: 831 Days
• Field of Search: 358/213, 358/228, 358/227, 358/212, 354/406, 354/407, 354/402
• US Class Current: 348/347
• CPC Class Codes: G02B 7/38 measured at different points on the optical axis , e.g. focussing on two or more planes and comparing image data
• CPC Class Codes: H04N 23/671 in combination with active ranging signals, e.g. using light or sound signals emitted toward objects
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method

Abstract

An automatic focus control system for a video camera comprises a main optical system for conducting light from an object and including an adjustable diaphragm for adjusting the amount of light conducted therethrough, a beam splitter disposed in the main optical system for diverting a portion of the light from the main optical system into an optical subsystem which has a second adjustable diaphragm for adjusting the amount of light conducted through the optical subsystem, a converter for converting the portion of the light diverted through the optical subsystem into focusing signals, and an automatic focus control circuit including a contrast detecting circuit for detecting a focused state of the light from the object in response to the focusing signals.

Claims

1. An automatic focus control system for adjusting a video camera from an unfocused state to a substantially focused state;

said system comprising;

a main optical system for conducting light from an object;

a first diaphragm for controlling the volume of light in the main optical system;

first means for photoelectrically converting the light from said object from the main optical system into an imaging signal;

an optical subsystem for conducting a part of the light from said object as conducted by said main optical system;

a second diaphragm for controlling the volume of said light in the optical subsystem;

second means for converting part of the light from said object from said optical subsystem into focusing signals; and

an automatic focus control unit including contrast detecting means responsive to said focusing signals and generating a control signal for controlling said second diaphragm in such a manner as to reduce its effective diameter in the unfocused state and enlarge its effective diameter in the substantially focused state.

2. The automatic focus control system for a video camera as in claim 1;

wherein said second diaphragm is interposed between said main optical system and said optical subsystem.

3. The automatic focus control system for a video camera as in claim 2;

and further comprising a beam splitter for splitting light from said object and supplying same to said main optical system light and said optical subsystem .

4. An automatic focus control system for adjusting a video camera from an unfocused state to a substantially focused state;

said system comprising;

a main optical system for forming an image of an object, said main optical system including an adjustable diaphragm means for adjusting the amount of light conducted therethrough;

beam splitting means disposed in said main optical system for diverting a portion of said light from said main optical system;

an optical subsystem for forming an image of said object from said portion of said light diverted from said main optical system by said beam splitting means;

second adjustable diaphragm means for adjusting the amount of light conducted through said optical subsystem;

converting means for converting said portion of said light into focusing signals; and

automatic focus control means including contrast detecting means responsive to said focusing signals for controlling said second diaphragm in such a manner as to reduce its effective diameter in the unfocused state and enlarge its effective diameter in the substantially focused state.

5. The automatic focus control system for a video camera as in claim 4 wherein said contrast detecting means includes first and second contrast detecting circuits for supplying first and second contrast signals, respectively, in response to said light from said object.

6. The automatic focus control system for a video camera as in claim 5 wherein said automatic focus control means includes comparison means for comparing said first and second contrast signals to generate a compared signal.

7. The automatic focus control system for a video camera as in claim 6 and further comprising means for adjusting the focus of said main optical system, and drive circuit means responsive to said compared signal for actuating said means for adjusting.

9. The automatic focus control system for a video camera as in claim 4 and further comprising second converting means for converting said light from said object from said main optical system into an image signal.

8. An automatic focus control system for a video camera comprising:

a main optical system for forming an image of an object, said main optical system including an adjustable diaphragm means for adjusting the amount of light conducted therethrough;

beam splitting means diaposed in said main optical system for directing a portion of said light from said main optical system;

an optical subsystem for forming an image of said object from said portion of said light diverted from said main optical system by said beam splitting means;

second adjustable diaphragm means for adjusting the amount of light conducted through said optical subsystem;

converting means for converting said portion of said light into focusing signals;

automatic focus control means responsive to said focusing signals and including contrast detecting means for detecting a focused state of said light from said object by detecting the contrast of said image formed by said optical subsystem at a plurality of points, comparison means for comparing said first and second contrast signals to generate a unimpaired signal, and means responsive to said first and second contrast signals for adjusting said second diaphragm;

said contrast detecting means including first and second contrast detecting circuits for supplying first and second contrast signals, respectively, in response to said light from said object; and

further comprising

means for adjusting the focus of said optical system, and drive circuit means responsive to said compared signal for actuating said means for adjusting.