Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2001-06-26
2003-01-21
Robinson, Mark A. (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S214100, C359S223100
Reexamination Certificate
active
06509996
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positioning assembly incorporating a torque motor, and, in particular, to a positioning assembly including a torque motor coupled to a position sensor enabling better heat dissipation from the motor.
BACKGROUND OF THE INVENTION
Torque motors are widely used for a variety of applications. One application is the use of a torque motor, in combination with a shaft position sensor, in a positioning assembly for positioning optical elements in order to guide light beams. The optical element can be a lens, mirror, waveplate, or the like. This type of device is often called an optical scanning galvanometer or optical scanner.
In operation, a light source directs light toward the optical element. The optical element reflects the light in desired directions depending on the task to be accomplished. The optical element is typically attached to the output shaft of the torque motor, which provides the necessary torque to drive the optical element. The position of the motor output shaft and optical element is sensed by a position sensor connected to the motor, and controlled, e.g. by a software application, based on the sensor output.
In a typical prior art configuration, the motor has its output shaft directly connected to the optical element on one end, and the position sensor coupled to the motor on the other end. In addition, the motor typically has a bracket connected to it to support the system. Thus, the motor is disposed between the output shaft/optical element combination and the position sensor. A problem with this configuration is that heat generated by the motor may be transferred directly to the position sensor, adversely affecting its performance. The heat generated by the motor may also be transferred to the connecting bracket, thereby causing expansion of the bracket and further adverse performance effects. For example, motor heat dissipation may result in unacceptable position drift in the system such that the speed and accuracy of the optical scanning system are hampered.
Accordingly, there is a need in the art for a positioning assembly including a thermally de-coupled motor configuration that enables better heat dissipation and reduces position drift in optical scanning systems.
BRIEF SUMMARY OF THE INVENTION
A positioning assembly for controlling the position of an element consistent with the invention includes: a motor having an output shaft coupled to the element; a position sensor; and a thermal isolator disposed between the motor and the sensor, the output shaft extending through the isolator and through at least a portion of the sensor. In one exemplary embodiment, the present invention may be utilized in an optical scanning system wherein the element to be positioned is an optical element for directing light from a light source. In optical scanning applications, the thermally de-coupled torque motor and position sensor permit enhanced heat dissipation from the torque motor, thereby reducing adverse thermal affects on the system.
A method of constructing a positioning assembly for positioning an element consistent with the invention includes: providing a motor having an output shaft; coupling the element to the output shaft; providing a thermal isolator; and coupling a position sensor to the motor with the output shaft extending through the isolator and the at least a portion of the sensor.
REFERENCES:
patent: 4388964 (1983-06-01), Almgren et al.
patent: 5575828 (1996-11-01), Dutto et al.
Grossman Tucker Perreault & Pfleger PLLC
Nutfield Technology, Inc.
Robinson Mark A.
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