Patent ID: 7970274

Claim:
A diaphragm control apparatus incorporated in a camera body, to which an interchangeable lens provided with a diaphragm apparatus is detachably attached, said diaphragm apparatus including a diaphragm operatively-associated rod for driving an adjustable diaphragm to open and shut said adjustable diaphragm, and said diaphragm control apparatus including a slider that is driven to move said diaphragm operatively-associated rod, said diaphragm control apparatus comprising: a diaphragm control mechanism including a stepping motor and a lead screw which is driven to rotate by said stepping motor, wherein said slider is moved by rotation of said lead screw; a resilient biaser which biases said slider toward an initial position at a movement extremity of said slider, wherein said slider is allowed to move to an initial position corresponding to an initial position of said diaphragm apparatus via said diaphragm operatively-associated rod by rotating said lead screw and said stepping motor when said stepping motor is in a free state with said interchangeable lens attached to said camera body; a position detector for detecting a position of said slider; and a controller which excites said stepping motor to rotate said stepping motor stepwise by repeating a plurality of excitation patterns, wherein, when driving said stepping motor by a predetermined number of steps in a direction to move said slider away from said origin position against a biasing force of said resilient biaser, said controller detects a position of said slider before driving said stepping motor stepwise as said origin position via said position detector, and thereafter detects a stepping position of said slider to compare said stepping position with said origin position each time said stepping motor is driven by one step, and counts said number of steps based from the moment at which said stepping position of said slider exceeds a predetermined position in said direction to move said slider away from said origin position against said biasing force of said resilient biaser.