초록 ▼

A still camera utilizes a focus evaluation value based on an imaging video signal to execute an autofocus operation by a hill-climbing control method. A CPU divides a focus area into a plurality of regions to obtain a focus evaluation value from a digital integrator for each of the regions. When the

A still camera utilizes a focus evaluation value based on an imaging video signal to execute an autofocus operation by a hill-climbing control method. A CPU divides a focus area into a plurality of regions to obtain a focus evaluation value from a digital integrator for each of the regions. When the autofocus operation is restarted from the state of a monitoring mode in accordance with a variation of the focus evaluation value, the CPU detects a further hill of the focus evaluation value while forcibly moving a focus lens position always toward a near side, and when a maximal value of the once detected focus evaluation value is less than a certain standard value, additionally executes the autofocus operation.

대표청구항 ▼

1. An imaging apparatus having an autofocus function, comprising:an imaging video signal generator having a focus lens and an imaging device, and providing an imaging video signal; a driver moving a position of said focus lens relative to said imaging device; a first focus area setting controller se

1. An imaging apparatus having an autofocus function, comprising:an imaging video signal generator having a focus lens and an imaging device, and providing an imaging video signal; a driver moving a position of said focus lens relative to said imaging device; a first focus area setting controller setting a focus area divided into a plurality of regions on an imaging screen; a first focus evaluation value generator detecting a high frequency component of said imaging video signal at each of said plurality of regions to generate a plurality of focus evaluation values respectively corresponding to said plurality of regions; a first autofocus controller executing an autofocus operation determining, from positions where said plurality of focus evaluation values respectively assume maximal values, a position where a maximal value can be attained at a closest side to be an in-focus position, and controlling said driver to move the position of said focus lens to the in-focus position; and a first autofocus restarting controller controlling said driver to restart said autofocus operation and to determine an in-focus position while forcibly moving the position of said focus lens from said in-focus position toward a near side, whenever variation occurs in said plurality of focus evaluation values at said in-focus position; said autofocus operation being executed per certain period of said imaging video signal. 2. The imaging apparatus according to claim 1, whereinsaid first autofocus restarting controller includes a first detector detecting a position where each of said plurality of focus evaluation values assumes a maximal value while moving the position of said focus lens from said in-focus position toward said near side, and a second detector detecting a position where the focus evaluation value assumes a further maximal value, when any maximal value of said plurality of focus evaluation values is lower than a certain standard value, by ignoring the maximal value and continuing movement of the position of said focus lens toward said near side. 3. The imaging device according to claim 2, whereinsaid first autofocus restarting controller includes a first adjuster adjusting the number of executions of said autofocus operation to be greater when any maximal value of said plurality of focus evaluation values is lower than a certain standard value. 4. The imaging apparatus according to claim 1, whereinsaid first autofocus restarting controller further includes a second adjuster adjusting the number of executions of said autofocus operation so as to continue movement of the position of said focus lens toward said near side when detected that the focus evaluation value is smaller than a previously detected maximal value but has an increasing tendency during movement of the position of said focus lens toward said near side. 5. The imaging apparatus according to claim 1, wherein said first autofocus restarting controller further includesa third adjuster adjusting the number of executions of said autofocus operation to decrease the number of executions of said autofocus operation for continuing the movement of the position of said focus lens toward said near side when a depth of field of said imaging video signal generator is set deep, and to increase the number of executions of said autofocus operation for continuing movement of the position of said focus lens toward said near side when a depth of field is set shallow. 6. The imaging apparatus according to claim 1, whereinsaid first autofocus restarting controller further includes a fourth adjuster adjusting the number of executions of said autofocus operation to decrease the number of executions of said autofocus operation for continuing movement of the position of said focus lens toward said near side when the position of said focus lens is at a near side at the time of restarting said autofocus operation, and to increase the number of executions of said autofocus operation for continuing movement of the position of said focus lens toward said near side when the position of said focus lens is at a distant side at the time of restarting said autofocus operation. 7. The imaging apparatus according to claim 1, further comprising:a luminance data generator detecting a luminance component at each of said plurality of regions to generate a plurality of luminance data respectively corresponding to said plurality of regions; and said first autofocus restarting controller including a restart stop controller stopping the restarting of said autofocus operation when variation of respective luminance data of said plurality of regions is relatively large. 8. The imaging apparatus according to claim 1, whereinsaid first autofocus restarting controller includes an autofocus terminating controller inverting a movement direction of the position of said focus lens toward a distant side if no in-focus position can be determined even though the position of said focus lens is moved toward said near side, and determining a position of a maximal value of a focus evaluation value detected first after the inversion as an in-focus position to terminate the autofocus operation. 9. The imaging apparatus according to claim 1, further comprising:a luminance data generator detecting a luminance component at each of said plurality of regions to generate a plurality of luminance data respectively corresponding to said plurality of regions; and a focus evaluation value controller excluding a focus evaluation value corresponding to a region where high luminance data is present, if any, among said plurality of regions, from a plurality of focus evaluation values to be targets of the autofocus operation by said autofocus controller. 10. The imaging apparatus according to claim 1, whereinsaid imaging video signal generator selectively supplies an imaging video signal of a still picture or an imaging video signal of a moving picture; and said imaging apparatus further comprises: a second focus area setting controller setting a plurality of focus areas or a single focus area, undivided into a plurality of regions; a second focus evaluation value generator detecting a high frequency component of said imaging video signal in said focus area undivided, to generate a focus evaluation value; a second autofocus controller executing an autofocus operation controlling said driver to determine a position where a focus evaluation value generated by said second focus evaluation value generator assumes a maximal value as an in-focus position and to move the position of said focus lens to the in-focus position; a second autofocus restarting controller controlling said driver to restart said autofocus operation and to determine an in-focus position, whenever variation occurs in said focus evaluation value at said in-focus position; and a switch controller operating said second focus area setting controller, said second focus evaluation value generator, said second autofocus controller and said second autofocus restarting controller in place of said first focus area setting controller, said first focus evaluation value generator, said first autofocus controller and said first autofocus restarting controller, when an imaging video signal of said moving picture is supplied from said imaging video signal generator. 11. The imaging apparatus according to claim 1, further comprising:a second focus area setting controller setting a plurality of focus areas or a single focus area, undivided into a plurality of regions; a second focus evaluation value generator detecting a high frequency component of said imaging video signal in said focus area undivided, to generate a focus evaluation value; a second autofocus controller executing an autofocus operation controlling said driver to determine a position where a focus evaluation value generated by said second focus evaluation value generator assumes a maximal value as an in-focus position to move the position of said focus lens to the in-focus position; a second autofocus restarting controller controlling said driver to restart said autofocus operation and to determine an in-focus position, whenever variation occurs in said focus evaluation value at said in-focus position; and a switch controller operating said second focus area setting controller, said second focus evaluation value generator, said second autofocus controller and said second autofocus restarting controller, in place of said first focus area setting controller, said first focus evaluation value generator, said first autofocus controller and said first autofocus restarting controller, when no in-focus position can be detected after restarting of the autofocus operation by said first autofocus restarting controller.