A Confocal Probe Base On Time Difference Measurement

As a type of modern large-scale precision instruments, coordinate measuringmachines become more and more important and have broad prospects in domain ofthe three-dimensional measurements. Probe is one of its major components, whichplays an essential role in terms of measuring accuracy, working efficiency andfunctions. According to the way of accessing probes are divided into contact type andnon-contact type. Nowadays, non-contact laser probes are becoming the mainstreamof development because of their high efficiency, quick-response, zero friction etc.New non-contact and convenient probes are needed to enable people to evaluate theirproducts. A new probe is developed in this thesis to satisfy this need. This probe hassmall light spot and can be used to measure the micro electro-mechanical system.A dynamic active confocal probe is developed in the thesis. The displacementmeasurement of the vibrating lens is converted to time difference measurement. Thetime difference between the peak signal and the zero point of the vibration motion isdetermined by A/D sampling and single chip computer technology. No auxiliary armis used in the probe, which makes the probe not only much simpler and of lower costbut also more efficient in industrial measurements.First, the overall design of the confocal probe based on time diffirentmeasurement, including system structure and improvement, electric circuit and signalprocessing system, is discussed in the thesis. Then, experimental studies of the probeperformance and analyses of the experimental results are presented.This research is financially supported by the National Natural Science Foundationof China, project No. 50275108 "The Motion Measuring and Testing Techniques inMEMS" and project No. 50075064 "Non-contact Intelligent Measurement ofFree-Form Sculptured Surfaces".