Development Of A Sphericity Detection System Based On Double Probes

At present,the characteristic sizes of micro-devices tend to be miniaturized.Microspheres are often used as scanning probes,because of the needs of measuring system,the processing sizes of microspheres are becoming smaller and smaller.For example,the probe used in micro-nano CMM measurement system is a microsphere with diameter ranging from tens to hundreds of microns and the sphericity is required in tens of nanometers or higher accuracy.At present,the measurement technology of microsphere sphericity is still in the exploratory stage,and there is no mature technology.To solve the problem of sphericity measurement of microspheres with diameters ranging from tens to hundreds of micrometers,a measurement method based on scanning probes technology is proposed in this thesis.Based on the proposed measurement method,the research contents of this thesis are summarized as follows.(1)The mechanical system that has been built is introduced.Resonant probes are constituted by tungsten probes with large aspect ratio and quartz tuning forks.Double probes and the microsphere are fixed on micro-motion tables with high precision respectively.Two probe tips are symmetrically placed on both sides of the equatorial circular cross section of the microsphere to realize measurement.(2)The signal processing circuit is designed and built.In order to obtain DC voltage signal with high quality which is required in the control system,the amplitude feedback processing circuit of the scanning probe signal is designed,and the circuit is debugged and fabricated.The weak sinusoidal voltage signal output by the probe is converted into a low noise DC voltage signal.(3)The alignment detection system of double probes and the microsphere is completed with high precision.The relative position of probes and the microsphere are on real time observations by horizontal and vertical video microscopes.The alignment images are processed by image fusion and image edge detection technology,and the alignment error is detected and compensated at the pixel level to achieve high precision alignment.(4)The measurement experiments of optical fiber microspheres are carried out.Two-dimensional contour datas are obtained by scanning equatorial circular cross-sections of the optical fiber microsphere at 0,30,60,90,120 and 150 degrees respectively.The three-dimensional contour information of the optical fiber microsphere is finally obtained through data processing.