Galvanometer-type scanner

• US 6,665,102 B2
• Filed: 09/25/2002
• Issued: 12/16/2003
• Est. Priority Date: 09/28/2001
• Status: Active Grant

• Current Assignee: Harmonic Drive Systems Inc.
• Original Assignee: Harmonic Drive Systems Inc.
• Inventors: Maruyama, Toshiki, Akahane, Akira, Tanioka, Nozomu, Miyashita, Kunio
• Primary Examiner(s): Phan, James
• Application Number:
  US10/253,716
• Publication Number:
  US 20030063357A1
• Time in Patent Office: 447 Days
• Field of Search: 359/198, 359/199, 359/200, 359/213, 359/214, 346/107--10, 310/36, 310/66, 310/145, 310/177, 318/37, 318/119
• US Class Current: 359/199.4
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence

Abstract

A DC motor of a galvanometer-type scanner has four poles, and compared to a conventional DC motor with a bipolar construction, the armature inductance L can be reduced to half or less for a case where the external diameter of the rotor and the induced voltage constant K_E are the same. Since K_E/L, which is the index for the rise of torque of the motor, is increased by a factor of two or more, the responsiveness of the motor can be improved without increasing the exciting current of the winding. Accordingly, it is possible to provide a galvanometer-type scanner that can set minute angles of around one degree within several hundred microseconds.

Claims

1. A galvanometer-type scanner that is required to perform positioning operations for minute angles of around one degree within a positioning time in the order of several hundred microseconds, an oscillation angle of a mirror being no greater than 30 degrees and the galvanometer-type scanner comprising:

a limited angle direct current (DC) motor; and

a mirror that is attached to a rotational shaft of the DC motor,

wherein the number of poles in the DC motor is four, and an electrical time constant (L/R) of the DC motor is longer than the required positioning time.