Patent ID: 7750534
Filing Date: 2010-07-06
Classification: G03B,H02N

Abstract:
1. A drive device comprising: an electromechanical transducer expanding and contracting in response to application of voltage; a given member moving back and forth with expansion and contraction of said electromechanical transducer; a moving part being engaged with said given member by a frictional force and capable of moving relative to said given member with expansion and contraction of said electromechanical transducer; and a voltage applying part applying voltage to said electromechanical transducer by repetition of an output cycle in which a selected one of a first voltage value, a second voltage value lower than said first voltage value, and a third voltage value lower than said second voltage value is output, said output cycle being a cycle of firstly outputting said first voltage value during a first period, secondly outputting said second voltage value during a second period, thirdly outputting said third voltage value during a third period, and finally outputting said second voltage value during a fourth period, wherein said voltage applying part is configured to change a moving speed of said moving part relative to said given member by varying the lengths of said first to fourth periods, said voltage applying part being further configured such that as the length of said first period is changed across a range from a minimum to maximum value thereof, at least one of the rates of change in the lengths of said second and fourth periods is changed at least once.