| 摘要 |
<p>A reference signal is used to track the actual behavior of the scanner (60) in an interferometer (40) to produce scanner-position data that can be used to correct errors introduced by scanner nonlinearities and other error sources. A narrow-band light source (42) is advantageously utilized to cover the entire range of operation of the scanner (60). Because of the independent reference channel, the invention is suitable for implementation with all types of conventional interferometric techniques. The concept is preferably implemented by utilizing an additional light source (42) and the same scanner (60) used for the measurement, so that the OPD varies in synchronization of both the reference-signal and data-collection procedures. Alternatively, a high temporal-coherence filter (32) may be used with the same light source (12) and optical path used for the interferometric measurement.</p> |
