Linear motor, linear motor system, and optical apparatus

A linear motor comprising:

• an armature configured to include coils;
• and
• a field magnet portion configured to include permanent magnets and yokes, the field magnet portion moving in an axial direction relative to the armature, and
• wherein in the field magnet portion, the permanent magnets and the yokes are disposed so that an interlinkage magnetic flux density, which is a density of interlinkage magnetic flux acting on the armature, changes periodically along the axial direction,
• the armature includes a first coil and a second coil, and the first coil and the second coil are disposed so that a phase distance between each other's centroids in the axial direction becomes 90° + n × 180° (n is an integer), corresponding to a periodic change characteristic along the axial direction of the interlinkage magnetic flux density caused by the field magnet portion,
• at least one third coil is further disposed on the armature in accordance with the periodic change characteristic along the axial direction of the interlinkage magnetic flux density caused by the field magnet portion,
• a thrust as a resultant force is obtained by controlling an energization amount ratio between the first coil, the second coil, and the third coil in accordance with a phase of the armature relative to the field magnet portion, and
• the third coil is disposed at a position relative to either the first coil or the second coil such that a phase distance between each other's centroids in the axial direction is greater than 135° and smaller than 225°.