Position detector and positioning device

Abstract

A position detector ( 3 ) capable of obtaining an output having a linearity in a wide range includes: a magnetic field generating member ( 11 ) attached to a movable member ( 10 ) movable in a predetermined movable direction (x); and magnetic field detection means ( 12 ) for detecting a magnetic field change caused by movement of the magnetic field generating member ( 11 ). The magnetic field generating member ( 11 ) includes an N-pole portion ( 13 ) magnetized into N-pole, an S-pole portion ( 14 ) magnetized into S-pole arranged in the movable direction with the N-pole portion ( 13 ), and a non-magnetized portion ( 15 ) not magnetized between the N-pole portion ( 13 ) and the S-pole portion ( 14 ).

1 .- 6 . (canceled) 
     
     
         7 . A position detector, comprising:
 a magnetic field generating member attached to a movable member movable in a predetermined movable direction and magnetized so that N-pole and S-pole are repeated in a fixed width in the movable direction; and   two magnetic field detecting elements for detecting a change of magnetic field caused by movement of the magnetic field generating member,   wherein the two magnetic field detecting elements are juxtaposed in the movable direction at an interval expressed as (n/2+¼) δ with respect to integer n, when a width of the N-pole and the S-pole is set to ½ δ, respectively,   the position detector further comprising operation means for carrying out operations of:   (A−B)/(A+B) if both A and B are 0 or more, and if both A and B are 0 or less; and   (A+B)/(A−B) if either A or B is less than 0,   wherein A and B represent detection signals by the two magnetic field detecting elements, respectively.   
     
     
         8 . The position detector according to  claim 7 , wherein the magnetic field detecting element is a magneto-resistive element. 
     
     
         9 .- 10 . (canceled) 
     
     
         11 . A positioning device, comprising the position detector of  claim 7 , wherein:
 the movable member being in frictional engagement with a drive shaft which is moved backward and forward in the movable direction by a piezoelectric actuator wherein,   the piezoelectric actuator has an electromechanical transducer expanded and contracted in the movable direction, for slidably moving the movable member on the drive shaft by changing a rate of expansion and contraction of the electromechanical transducer.   
     
     
         12 . The positioning device according to  claim 11 , wherein the movable member holds an optical element. 
     
     
         13 . The position detector according to  claim 7 , wherein each magnetic field detecting element is a Hall element.