The con-focal method on verifying focal plane of MAS machine

The Maskless DNA Array Synthesizer (MAS) is very efficient and flexible device on custom designed DNA array fabricating. To make the MAS's focal plane keep stable is important during the chip synthesizing process. In this paper we bring a creative idea using con-focal method to verify focal plane of MAS machine. That method is very sensitive on focal plane verification and could be used on other optical lithography system or the projecting system, which need real time focal plane precision control.