Position-detecting system
A position-detecting system, which is used to detect a relative position of a movable member with respect to a fixed member, is provided. The system includes a plurality of light sources, a position-sensing device, and a light-source controller. The light sources are provided on one of the fixed member or the movable member, and emit a spotlights. The position-sensing device is provided on another one of the fixed member or the movable member. The position-sensing device receives the spotlight and outputs a position signal relating to the relative position in accordance with a position where the spotlight is received. The light-source controller controls an ON/OFF state of the plurality of light sources. The light-source controller continuously turns on one of the light sources when only a spotlight from light source is detected by the position-sensing device, and flashes two or more than two of the light sources when spotlights from two or more than two light sources are detected by the position sensing device.
1. A position-detecting system, comprising:
a movable member that is moved in a two-dimensional plane relative to a fixed member;
a light source unit that is provided on one of said fixed member and said movable member, and said light source unit comprises a plurality of light emitting devices which is separately disposed at a predetermined distance;
a position-sensing device that is provided on another one of said fixed member and said movable member, and which receives light from said light source unit and detects a position where said light is received;
a light-source controller that selectively turns on one of said plurality of light emitting devices in a predetermined order; and
a calculator that calculates a direction, displacement, and rotation of motion of said movable member in accordance with two pairs of position data, in which one pair of position data represents positions where light from a pair of light emitting devices is detected and the other pair of position data represents positions where light from said pair of light emitting devices is detected at a predetermined time interval after said one pair of position data is detected.
2. A position-detecting system according to claim 1 , wherein the number of said plurality of light emitting devices is two, and said light-source controller alternately turns on said two light emitting devices over the same interval.
3. A position-detecting system according to claim 1 , wherein said movable member is rotatably supported with respect to the fixed member.