Bearingless ultrasound-sweep rotor

An ultrasonic imaging device comprising:

• a. a housing having a region transparent to ultrasonic signals;
• b. a mirror within said housing and obliquely aligned with an ultrasonic transducer, wherein said mirror is designed to reflect ultrasonic signals transmitted by said transducer;
• c. a rotor comprising a first magnetic region, a second magnetic region, and a third magnetic region, wherein said first magnetic region is connected to said mirror;
• and
• d. stator means comprising a first stator block connected to said housing proximal to said rotor, and a second stator block connected to said housing distal to said rotor,
• wherein said first magnetic region and said third magnetic region have oppositely-directed dipole moments substantially axially aligned with said rotor, wherein said second magnetic region lies between said first magnetic region and said third magnetic region and has a dipole moment substantially transversely aligned with said rotor, and wherein said first stator block and said second stator block have oppositely-directed dipole moments substantially axially aligned with said rotor.

An ultrasonic imaging method comprising the steps of:

• a. connecting an ultrasonically-reflective mirror to a rotor;
• b. magnetically suspending said rotor within an ultrasonically conductive fluid;
• and
• c. rotating said mirror and said rotor within said ultrasonically conductive fluid.

A levitation position control system comprising:

• a. a driver coupled to and for positioning an object;
• b. sense means for generating a velocity signal from movement of said object;
• c. integration means for converting said velocity signal into a position signal;
• d. velocity servo means for employing said velocity signal and said position signal to generate a drive signal that servoes said position signal to a target value;
• and
• e. integration offset correction means for causing said drive signal progressively to re-bias said position signal.

A method for controlling the levitation position of an object, said method comprising the steps of:

• a. exerting a driving force to said object;
• b. generating a velocity signal indicating a change in a position of said object;
• c. integrating said velocity signal to obtain a position-indicating signal;
• d. determining said driving force as a function of said velocity signal and said position-indicating signal, such that said position-indicating signal approaches an equilibrium value;
• and
• e. progressively correcting an offset of said position-indicating signal in response to said driving force.