Research On Development Of A3D Contact Probe With Large Scanning Range For Nano-Coornidate Measuring Machines

In this research a novel scanning probe has been developed, with micron range and nanometer resolution. This probe can be equipped in a3D micro/nano measuring system for microstructure measurement. This scanning probe includes an elastic mechanism, composed by a ball-tip, a stylus, a floating plate, reflective mirrors, elastic components and the housing structure, transforming the3D motion of the tip-ball into the angular and linear displacement of the reflective mirrors, which can be detected by an embedded3D sensor. The main tasks of this research are listed as below:1. A3D sensor has been proposed by integrating a micro Michelson interferometer and a DVD pickup head for linear and angular measurement respectively. The angle measuring range of the DVD pickup head has been effectively increased. An elastic-component-based probe structure featured by small size and good symmetry has been designed. Then, instead of the DVD pickup head with a micro auto-collimator which shares the same laser diode with the micro Michelson interferometer, a reformed3D sensor based on the micro auto-collimator and the micro Michelson interferometer has been designed. Additionally, an optional structure of the micro Michelson interferometer and micro auto-collimator with parallel optical path was also developed to achieve better alignment tolerance by introducing a lens beside the reflective mirror.2. Three elastic structures with equal-strain based on elastic strings, Z-shaped and V-shaped beryllium bronze plate springs have been designed and the rigidities have been modeled respectively. The maximum permitted contact forces in scanning measurement have been calculated aiming at the typical materials both the specimen and the ball tip. Each structure has been optimized and the proper parameters have been obtained. The optimized designs have been testified by both ANSYS simulation and practical experiments.3. After the fabrication, installation and testing of the probes are completed; different experimental systems were set up to calibrate the contacting force, resolution, stability, measuring range and repeatability. Experimental data show that the probe has the contacting force gradient within1mN/μm, resolution of1nm, measuring range of±20μm x±20μm x20μm and the repeatability accuracy within30nm. It’s found that the temperature variation contributes most to the reading drift. Compared with the optoelectronic system, the mechanic structure is much more sensitive to the temperature variation. In a constant temperature space the reading drift of the probe is less than30nm for the duration of one hour.4. The coupling of three axes has been analyzed and three different mathematic models have been proposed for decoupling. A PI nanopositioning stage was employed to set up the calibration system, with which the original measurement data table was acquired. Then two mathematic models, based on multiple linear regression and Taylor expansion respectively, were configured with the original measurement data to determine the decoupling parameters. The former was found to have higher accuracy. The working performance of the probe has been testified by measuring the flatness and thickness of a standard gauge block and the diameter of a convex lens. Besides, the error source of the probe was analyzed and the methods to improve the measuring accuracy were proposed.