Refractive index matched half-wave plate with a nematic liquid crystal for three-dimensional laser metrology applications

摘要

There exists a need in a quality and accuracy of a three-dimensional laser metrology operating in numerically controlled automatic machines. For this purpose, one sends three laser beams mutually perpendicular. These three beams of the wavelength lambda = 0.6328 mu m are generated by the same laser and are directed along three independent, orthogonal, mutually perpendicular, optical paths with a given light polarization plain. Using these beams, constituting the frame of coordinates, three independent laser rangefinders are able to determine spatial coordinates of a working tool or a workpiece. To form these optical pulses, a special refractive index matched Half-Wave Plate with nematic Liquid Crystal (LCHWP) was applied. The presented half-wave plate is based on a single Twisted Nematic (TN) cell (with the twist angle Phi = pi/2) of a rather high cell gap d similar to 15 mu m filled with a newly developed High-Birefringence Nematic Liquid Crystal Mixture (HBLCM) of optical anisotropy as high as Delta n similar to 0.40 at lambda = 0.6328 mu m, where the Mauguin limit above 5.00 similar to Delta nd lambda/2 = 0.32 is fulfilled.