AUTOFOCUS LENS DEVICE AND IMAGING SYSTEM

Japanese Patent JP2015055689

A

PROBLEM TO BE SOLVED: To provide a lens device that enables an appropriate amount of light to be adjusted in accordance with a usage situation or an intension of a user when adjusting an amount of light so that a F-number does not exceed a threshold capable of an autofocus control.SOLUTION: In a lens device comprising: an autofocus control group performing an in-focus detection by detection of a phase difference using an image formation optical system including, in order from an object side, a focus lens group 1, a variable diaphragm 2 serving as first light amount adjustment means, and a branch optical system 3 and a branch ray flux; and second light amount adjustment means 5 which is different from the first light amount adjustment means 2 and adjusts the amount of light gradually, let a threshold of a F-number capable of detection of an in-focus position be denoted as F1 and a full aperture F-number of the lens device be denoted as F2, and upon causing an amount of light to be reduced by the light amount adjustment means 5, let a F-number right before the amount of light is caused to be reduced be denoted as Fb, an amount of adjustment Ln causing the amount of light to be reduced by the second light amount adjustment means 5 falls within a range satisfying F2≤Fb/√Ln