HIGH RESOLUTION ENCODER HEAD

摘要

A measurement system (22) for measuring the position of a work piece (28) along a first axis includes a grating (234), and an encoder head (238) that directs a first measurement beam (240) at the grating (234) at a first angle, and directs a second measurement beam (242) at the grating (234) at a second angle. An absolute value of the first angle relative to a normal (244) of the grating (234) is different from an absolute value of the second angle relative to the normal (244) of the grating (234). Additionally, the first measurement beam (240) has a first wavelength, and the second measurement beam (242) has a second wavelength that can be different from the first wavelength. Further, the first measurement beam (240) and the second measurement beam (242) can impinge at approximately the same location on the grating (234).

主权项

1. A measurement system for measuring a relative movement along a first axis of a first object and a second object, the first object and the second object being movable relative to each other, the measurement system comprising:
a grating that is coupled to one of the first object and the second object; and an encoder head that directs a first measurement beam at the grating at a first angle, and directs a second measurement beam at the grating at a second angle; wherein an absolute value of the first angle relative to a normal of the grating is different than an absolute value of the second angle relative to the normal of the grating.