A Method To Calibrate Micro-CT Metrology System

Dimensional CT metrology,as a new coordinate measuring technology has been gradually prevalent.Many research institutions from all over the world have been doing some continuous researches on this issue and have yielded some results.Since there are many components such as X-ray source,kinematic system,detector and data reconstruction module in a metrology CT,it renders complicated error sources.Micro-CT system had been developed with an optocoupler detector added,which increases the spatial resolution and extends the measuring range of the system from micrometers to hundreds of micrometers.However,scintillators,objective lens,tube lens and CCD yield more complicated error sources.This will result in difficulty of increasing the measuring accuracy and tracing the measurement uncertainty.To solve this problem,A scheme focusing on the metrological characteristics of micro-CT system had been designed and microsphere standard which can be used to calibrate the probing form error and probing size error had been developed,while micro ball-plate standard and micro hole-plate standard which can be used to calibrate the length measuring error had been developed as well.The values of the standards’ features were calibrated with micro-nano coordinate measuring machine,roundness instrument and metrological scanning electron microscope.Then the micro-CT system was calibrated with the micro standards.Preliminary estimation of the sources of uncertainty was carried out and combined standard uncertainty was calculated later.In the end,reasonable prospect has been taken in order to develop new micro standards with new material or methods.