Position detecting device
AssigneeCanon Kabushiki Kaisha
InventorsHiroyuki Takahara, Shigeru Ogino, Masayoshi Sekine
Life of this patent
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Abstract
A position detecting device comprises a movable member, a first electrode movable with the movement of the movable member, and a second electrode disposed at a location opposed to the first electrode. The edge of at least one of the first and second electrodes are inclined with respect to the direction of movement of the first electrode, whereby the area over which the first electrode and the second electrode overlap each other is varied by the relative movement of the two electrodes and an electrostatic capacity provided by the two electrodes is also varied to make the detection of the absolute position of the movable member possible and to change a position detection accuracy in accordance with a position of the first electrode.
Claims21
A position detecting device comprising:
- (a) a movable member;
- (b) a first electrode movable with movement of said movable member;
- and
- (c) a second electrode disposed at a location opposed to said first electrode, an edge of at least one of said first and second electrodes being inclined with respect to a direction of movement of said first electrode, the inclination of the edge varying in accordance with a position of said first electrode relative to said second electrode so that an area over which said first electrode and said second electrode overlap varies in response to relative movement of said first and second electrodes, to indicate an absolute position of said movable member with respect to said second electrode and to change a position detection accuracy in accordance with a position of said first electrode.
An optical apparatus having a position detecting device, comprising:
- (a) a first movable lens movable in a direction of an optical axis thereof;
- (b) first driving means for moving said first movable lens;
- (c) a second movable lens movable in a direction of an optical axis thereof;
- (d) second driving means for moving said second movable lens;
- (e) a first position detection device for detecting the position of said first movable lens, said first position detection device being provided with a first electrode movable with the movement of said first movable lens, and a second electrode disposed at a location opposed to said first electrode, an edge of at least one of said first electrode and said second electrode being inclined with respect to the direction of movement of said first electrode, the inclination of the edge varying in accordance with a position of said first electrode relative to said second electrode so that an area over which said first electrode and said second electrode overlap varies in response to relative movement of said first and second electrodes, to vary an electrostatic capacity to indicate an absolute position of said first movable lens with respect to said second electrode and to change a position detection accuracy in accordance with a position of said first electrode;
- and
- (f) movement control means for driving said second driving means to move said second movable lens using information regarding the absolute position of said first movable lens obtained by at least said first position detection device.
Dependencies are inferred from the claim text.