초록 ▼

An automatic focusing apparatus of a video camera automatically matches a focus in response to a video signal obtained from an image sensing circuit. The automatic focusing apparatus detects the level of a high frequency component of the video signal in order to supply a focus evaluating value which

An automatic focusing apparatus of a video camera automatically matches a focus in response to a video signal obtained from an image sensing circuit. The automatic focusing apparatus detects the level of a high frequency component of the video signal in order to supply a focus evaluating value which takes a maximum value in an in-focus position. A focusing motor controlling circuit performs an automatic focusing operation by a hill-climbing servo system based on the supplied focus evaluating value. A determination is made by employing a fuzzy inference with respect to the initialization of the direction of movement of a lens when the automatic focusing operation starts, the selection of a focusing area from a plurality of areas, and the reactivation of the automatic focusing operation due to a change of an object after once the automatic focusing operation is completed.

대표청구항 ▼

An automatic focusing apparatus for automatically matching a focus relative to an object in response to a video signal obtained from image sensing means, said image sensing means including a focusing lens (1) and an image sensor, said apparatus comprising: relative position changing means (2, 3) for

An automatic focusing apparatus for automatically matching a focus relative to an object in response to a video signal obtained from image sensing means, said image sensing means including a focusing lens (1) and an image sensor, said apparatus comprising: relative position changing means (2, 3) for changing a relative position of said focusing lens relative to said image sensor and along an optical axis of said focusing lens; focus evaluating value detecting means (50) for detecting a level of a high frequency component of the video signal obtained from said image sensing means and for supplying the detected level as a focus evaluating value representing a degree of in-focus relative to said object, wherein said focus evaluating value detecting means comprises: means (5a, 51, 50b, 5f, 50f), responsive to said video signal, for establishing a plurality of areas on an image sensed by said image sensor; and means (5c, 50c, 5h, 5d, 5e, 5g, 50g), operative in response to said establishing means, for extracting the high frequency component of said video signal in each one of said areas and, in response thereto, generating a plurality of corresponding focus evaluating values; and control means (100), connected to said relative position changing means, for determining a direction in which the focusing lens is to move along said axis in order to achieve an in-focus position and for controlling said relative position changing means, in response to said plurality of focus evaluating values, in order to move the relative position of said focusing lens to the in-focus position; wherein the control means determines a weighted mean value by evaluating a fuzzy inference wherein specific ones of said focus evaluating values are applied as input to a plurality of pre-defined rules, with each of the rules providing a pre-defined output value so as to define, for all of said rules, a plurality of pre-defined output values, the fuzzy inference being evaluated by: associating, for each of said rules, a pre-defined membership value with at least a specific one of the focus evaluating values so as to form a plurality of membership values for all of said rules; and determining the weighted mean value as a weighted mean value of all of said output values each weighted by a corresponding one of said membership values; and the control means ascertains the direction in response to the determined weighted mean value.