First and second coherent beams illuminate a common area on an exposure station. A phase detector senses the relative phase between the first and second beams to provide a control signal. There is at least one phase shifter in the path of at least one of the coherent beams. The control signal is coupled to the phase shifter to adjust the phase imparted thereby so that the relative phase between the first and second coherent beams is substantially constant.
申请公布号
US5142385(A)
申请公布日期
1992.08.25
申请号
US19910643141
申请日期
1991.01.09
申请人
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
发明人
ANDERSON, ERIK H.;SMITH, HENRY I.;SCHATTENBURG, MARK L.