| 摘要 |
A microphone or other acoustic sensor is used to detect sound or other vibrations caused by the passage of pulses of radiation of a projection beam. The measured vibrations may be used to determine the intensity of the projection beam or the presence of contaminants. The vibrations are caused by absorption of the beam pulses in an absorptive gas or by objects, e.g. the substrate or mirrors in the projection lens, on which the projection beam is incident. <IMAGE> |
