Phase Imbalance Optimization in Interference Linear Displacement Sensor with Surface Gratings

Abstract

In interferential linear displacement sensors, accurate information about the position of the reading head is calculated out of a pair of quadrature (sine and cosine) signals. In double grating interference schemes, diffraction gratings combine the function of beam splitters and phase retardation devices. Specifically, the reference diffraction grating is located in the reading head and regulates the phase shifts in diffraction orders. Measurement diffraction grating moves along with the object and provides correspondence to the displacement coordinate. To stabilize the phase imbalance in the output quadrature signals of the sensor, we propose to calculate and optimize the parameters of these gratings, based not only on the energetic analysis, but along with phase relationships in diffraction orders. The optimization method is based on rigorous coupled-wave analysis simulation of the phase shifts of light in diffraction orders in the optical system. The phase properties of the reference diffraction grating in the interferential sensor are studied. It is confirmed that the possibility of quadrature modulation depends on parameters of static reference scale. The implemented optimization criteria are formulated in accordance with the signal generation process in the optical branch. Phase imbalance and amplification coefficients are derived from Heydemann elliptic correction and expressed through the diffraction efficiencies and phase retardations of the reference scale. The phase imbalance of the obtained quadrature signals is estimated in ellipticity correction terms depending on the uncertainties of influencing parameters.

A Tribute to Sergey Odinokov

“…research in the field of security holograms and the development of new types of security features used to protect documents from forgery and falsification: micro-and nano-optical hidden elements, plasmonic diffraction gratings, color 2D/3D images formed in photopolymer materials; -development of optoelectronic devices for identification and control of the authenticity of documents with security holograms [1]; -development of optical-holographic systems of archival memory (including based on computer-generated holograms) [2]; -the creation of computer-generated holographic and diffraction optical elements for miniature optoelectronic devices and systems, micro-optics and devices, using plasmachemical etching technology [3]; -development of holographic aiming and target designation devices [4]; -calculation and manufacture of holographic waveguides, and the development of advanced visualization and augmented reality systems on their basis [5,6]; -the creation of various types of holographic sensors: wavefront sensor [7][8][9], encoders of angular and linear displacements [10].…”