Nonlinearity and frequency-path modelling of three-longitudinal-mode nanometric displacement measurement system

Nano-Metrology Based on the Laser Interferometers

“…The distinct interference terms can be divided into four groups namely dc interference (DI), ac interference (AI), ac reference (AR), and optical power (OP). These components in the threelongitudinal-mode interferometer are respectively given by (Olyaee & Nejad, 2007a Figure 10 shows the combination of the frequency-path elements in the measurement arm of two systems. The main signals and leakages are depicted by large and small solid circles, respectively.…”

Design of electronic sections for nano-displacement measuring system

“…The resolution of the phase detector is proportional to the counter clock pulse. If the frequency of the clock pulse is denoted by f CLK , the phase detection resolution is given by [4] δ…”

“…The trends of reducing the minimum feature size, increasing wafer size and increasing throughput push the performance requirements for interferometric systems to small levels. Nowadays, the laser heterodyne interferometers are the instrument of choice for many precision machines which can be readily extended up to a resolution less than one optical wavelength [4][5][6][7]. Enhanced heterodyne displacement measurement interferometers using a three-longitudinal-mode He-Ne laserbased super-heterodyne technique were first introduced by Yokoyama in 2001 [8].…”

Use of adaptive RLS, LMS, and NLMS algorithms for nonlinearity modeling in a modified laser interferometer

“…It was shown that the principal measurement nonlinearity in a heterodyne interferometer arises from elliptical polarization and nonorthogonality of the two frequencies laser input. Many efforts have been done to model and to compensate the nonlinearity error by inserting more complex optical setup and complex computational analysis [5][6][7][8][9][10][11][12][13][14][15][16].…”