Patent ID: 7974530
Filing Date: 2011-07-05
Classification: G03B

Abstract:
1. 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 position detector, which detects 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 said slider is biased to move toward an initial position by a resilient biaser, wherein, when said stepping motor is in a free state with said interchangeable lens attached to said camera body, said slider allows said diaphragm operatively-associated rod to move to a position corresponding to an initial position of said diaphragm apparatus by a biasing force of said resilient biaser while rotating said lead screw and said stepping motor, wherein said controller detects a position of said slider held at said position corresponding to said initial position of said diaphragm apparatus as an origin position of said slider via said position detector, wherein said controller drives said stepping motor, which is initially at rest at a position corresponding to said origin position, stepwise in a first direction to move said slider away from said origin position against said biasing force of said resilient biaser by repeating said plurality of excitation patterns in a predetermined order; thereafter drives said stepping motor stepwise in a second direction to move said slider toward said origin position by repeating said plurality of excitation patterns in reverse order to said predetermined order while detecting a position of said slider via said position detector; and thereafter detects a position of said slider after holding said stepping motor for a first waiting time upon a distance from said detected position of said slider, which is detected via said position detector, to said origin position becoming less than a moving distance of said slider for one step of said stepping motor, wherein said controller causes said stepping motor to enter a free state upon a lapse of said first waiting time, and wherein said controller performs an origin-position initialization process, in which said controller detects a position of said slider upon a lapse of a second waiting time to set one of said plurality of excitation patterns as an initial excitation pattern from a difference between a position of said slider detected during said holding of said stepping motor for said first waiting time and a position of said slider detected in said free state thereof and further from said moving distance of said slider.