Patent ID: 9503676
Filing Date: 2016-11-22
CPC Classification: G01B,G01D,G02B,G11B,H04N

Claim Text:
1. A lens device having a movable optical element, the lens device comprising: a rotary member configured to rotate around an optic axis of the movable optical element depending on a movement of the movable optical element; a magnetic recording member fixedly provided on the rotary member and disposed along a circumferential direction of the rotary member, the magnetic recording member being recorded, at a plurality of positions on an outer periphery of the rotary member in a rotational direction thereof, with a plurality of position magnetic signals, respectively, which are magnetic signals that indicate the positions, respectively; a signal detecting unit disposed at a position facing the magnetic recording member so as to detect the magnetic signal recorded in the magnetic recording member; and a position detecting unit configured to detect a position of the movable optical element based on the magnetic signal detected by the signal detecting unit, wherein the position magnetic signals are each formed by a magnetic pattern magnetized in the rotational direction, the magnetic pattern indicating an n-bit digital code where n is equal to or more than a natural number of 2, a range in which one of the position magnetic signals is recorded in the magnetic recording member, has a first width in the rotational direction of the rotary member, the magnetic recording member is recorded with a range identification magnetic signal between each two adjacent position magnetic signals of the plurality of position magnetic signals to be adjacent to the position magnetic signals, the range identification magnetic signal is a magnetic signal that identifies a range in which the adjacent position magnetic signal is recorded, the range identification magnetic signals are each formed by a magnetic pattern magnetized in the rotational direction, a range in which one of the range identification magnetic signals is recorded, has a second width in the rotational direction, the second width being smaller than the first width, the position detecting unit detects the position of the movable optical element based on the position magnetic signal which is detected continuously after the range identification magnetic signal is detected, and a magnetic intensity of the magnetic pattern forming the range identification magnetic signal differs from a magnetic intensity of the magnetic pattern forming the position magnetic signal.