Focus control method and video camera apparatus

A video camera apparatus having an autofocus function for focusing a focus lens having focus lens positions on a target object imaged by an imaging means, comprising:

• estimation value generating means for generating for each focus lens position a plurality of estimation values by extracting a high-frequency component of a video signal output from said imaging means under respectively different conditions of imaging said target object;
• and
• control means for, in consideration of a total estimation value determined as a summation of a plurality of said estimation values indicating an increase/decrease in said plurality of estimation values resulting from movement of said focus lens, detecting a correct focus lens position where said target object is brought into focus, and for moving said focus lens to said correct focus lens position.

A video camera apparatus having a focus lens for focusing a target object received by an imaging means by setting said focus lens to focus lens positions for imaging said target object, said apparatus comprising:

• a plurality of estimation value generators adapted to generate a plurality of estimation values for each focus lens position, by extracting a high-frequency component of a video signal output from said imaging means when said focus lens is moved to said focus lens position, wherein each estimation value is associated with one of a plurality of estimation windows;
• and
• a focus controller operative to control said focusing based on an operation of summing at least up counts and down counts for a current lens position, each up count representing a condition in which an estimation value for an associated window is larger than the estimation value for that window in a previous lens position, each down count representing a condition in which an estimation value for an associated window is lower than the estimation value for that window in the previous lens position, and said focusing is controlled in accordance with the largest sum of up or down counts for the current lens position.

A focus control apparatus for controlling a focus lens of a video camera for focusing a target object received by an imaging means by setting said focus lens to focus lens positions for imaging said target object to produce a video signal, said apparatus comprising:

• estimation value generating means having a plurality of estimation value generating circuits for generating a plurality of estimation values for a focus lens position by extracting a high-frequency component of a video signal output from said imaging means, wherein each estimation value generating circuit generates a respective estimation value under a respectively different specific filtering condition of imaging said target object;
• and
• a focus controller operative to control said focus lens based on an operation of summing at least up counts and down counts for a current lens position, each up count representing a result in which an estimation value for an associated filtering condition is larger than the estimation value for that condition in a previous lens position, each down count representing a result in which an estimation value for the associated filtering condition is lower than the estimation value for that condition in the previous lens position, and said focusing is controlled in accordance with the largest sum of up or down counts.