A focus sensor for an application in a nanopositioning and nanomeasuring machine

Abstract

A focus sensor on the basis of a hologram laser unit was developed and successfully tested in a nanopositioning and nanomeasuring machine as a zero indicator. The high resolution of the focus sensor is due to a high-precision optical adjustment and special solutions incorporated into the electronic parts. Thus, any sensor malfunctions caused by back-reflected light inside of the assembly could be completely avoided by means of the special high-frequency modulation and laser power stabilization. Common mode noise reduction provides the high SNR of the output signals. The measurements were made according to a dynamic principle by permanent difference formation between the output signal of the focus sensor and the length value of the z-interferometer of the nanopositioning and nanomeasuring machine. The measuring results are presented, and further possibilities of application are outlined.