Optical deflector with a pneumatic and a magnetic bearing

An optical deflector which deflects light issuing from a light source by rotating a mirror, comprising:

• a rotary shaft rotatable integrally with said mirror which is mounted on an outer periphery of said rotary shaft, said rotary shaft being formed with herringbone grooves on said outer periphery;
• an annular rotary magnet assembly mounted on said outer periphery of said rotary shaft and magnetized to different polarities sequentially in a circumferential direction;
• casing means for accommodating and rotatably supporting said rotary shaft, said outer periphery of said rotary shaft and an inner periphery of said casing means constituting a dynamic pressure pneumatic bearing;
• a first rotary magnet mounted in an upper end portion of said rotary shaft;
• a first stationary magnet mounted on said casing means to face said first rotary magnet with a polarity the same as said first rotary magnet, said first rotary magnet and first stationary magnet constituting a thrust magnetic bearing due to a repulsive force acting therebetween;
• a second stationary magnet located to face said rotary magnet with a polarity the same as said first rotary magnet, said first and second stationary magnets constituting a thrust magnetic bearing due to a repulsive force acting therebetween;
• a cap member connected to said casing means for supporting said stationary magnet inside of said cap member;
• and
• coil means disposed in said casing means to face said rotary magnet assembly, said rotary magnet assembly and coil means constituting a motor.