Research On Key Technologies Of Nanometer Displacement Measurement By Grating Interferometry

Nanometer measuring technology is one of the crucial preconditions that, for the moment and future, are capable of dealing with many problems caused by high precision and high resolution requirement. It is not only the precursor and foundation for nanometer science but also a critical problem being faced with metrology. Grating interferometry is one of the technologies that can implement displacement measurement with nanometer resolution. It has many unique advantages compared with laser interferometry. And it can achieve higher accuracy and resolution than traditional geometry moiré. It has been proved to be very useful in many practical applications, such as microelectronics, ultra-precision manufacturing, bioengineering, medicine, space technology, and material science, etc.In this dissertation, Key technologies of nanometer displacement measurement by grating interferometry are systematically investigated, which mainly include measuring theories, designing grating interferometer and new subdividing method for moiréinterference fringes. The main works and contributions achieved in this dissertation are concluded as follows:1. Based on the scalar diffraction theory, the mathematical model of optical configuration of transmissive grating interferometer is established. It indicats that moiréinterference fringes is affected by many parameters, such as grating pitch, light wavelength, light beam size and incidence angle, etc. The variation that the width, intensity, orientation and contrast of moiréinterference fringes along with every parameter is numerically analyzed.2. The diffraction characteristics of rectangular grating are studied deeply by vector diffraction theory. The relationships between the number of diffraction order and grating pitch, refractive index of medium, light wavelength, incidence angle and azimuth angle are investigated. The diffraction efficiency changing with grating parameters, especially for the situation that Gaussian beams diffracted by finite grating, is numerically studied.3. A new optical configuration of grating interferometer that based on polarization-maintained fiber optical coupler (FOC) is put forward. Because the spectroscope and reflector in transmissive grating interferometer are replaced with FOC the ratio of beam splitting is steady and can no longer vary with fluctuation of light intensity and polarization orientation. The contrast of moiréinterference fringes is more constant than that of traditional grating interferometer. Furthermore, the measurement error...