| Abstract | A laser Doppler encoder includes a set of prisms mounted on a fixed base
along with an additional prism, an end retroreflector and a laser/detector
and a second set of prisms mounted on a moving/rotating base. The
laser/detector generates a laser beam that is transmitted through the sets
of prisms on the fixed and moving bases as well as the additional prism
and the end retroreflector until the laser beam finally reaches a
heterodyning detector that is housed coaxially inside the laser/detector.
The laser beam is a frequency-stabilized laser beam such that the laser
beam that is reflected back to the heterodyning detector is
frequency-shifted by the movement of the moving base relative to the fixed
base so that the amount of movement (either rotational or linear) of the
moving base can be accurately determined. Moreover, the end retroreflector
enables the laser Doppler encoder to be readily self-aligned such that the
alignment time is substantially reduced and the three-dimensional optical
path configuration results in a compact and integrated optical design
which optimizes the system's anti-vibration performance. The laser Doppler
encoder can be used in conjunction with a high energy resolution
monochromator for accurately determining the rotational movement of an arm
in the monochromator or can be used in conjunction with a closed looped
motion controller for providing feedback on the rotational displacement of
the arm of the monochromator so that the arm can be accurately positioned. |
