Study On High Precision Linear Time-Grating Displacement Sensor Based On Configured Moving Light Field

Precise displacement measurement is the most crucial physical quantity in the process of precision manufacturing and also one of important means to guarantee product quality.Optical measurement methods have remained dominant roles in the common precision displacement methods.Among the optical measurement methods,laser interferometers and optical grating sensors are applied widely.However,due to the high prices and strict environmental requirements for laser interferometers,and stringent specification of manufacturing equipment and infrastructure for high precision grating,and blockade on techniques by foreign countries,the optical precision measurement technology and equipment is lagging far behind international advanced level.Funded by National Natural Science Foundation of China(NSFC),this paper develops the research on time grating sensor based on the configured moving light field.The main purpose of this research is to develop a displacement sensor which can rival the international high precision grating by using domestic relatively undeveloped grating production process and infrastructure.The main contents and innovations are as follows:(1)The mathematical models of traditional displacement measurement and time grating measurement are summarized systematically.Various displacement measurement methods are summed up in two mainly mathematical models,and the characteristics of displacement measurement are analyzed.At the same time,the mathematic model of time grating is concluded and the essential feature about how time grating measured displacement by using time is illustrated.Based on the measurement principle,this paper illustrates the essential differences between time grating measurement method and other traditional measurement methods.(2)Through the analysis of rotating magnetic field,a configured method of high precision moving light field,with a precise modulation of time and space to light intensity,is proposed in the optical field.To verify the feasibility of measurement scheme,which is used the light intensity modulation of time and space to realize displacement measurement,a single grate type of time grating prototype is designed.(3)The researches on designing,simulating,and fabricating of LED(Light Emitting Diode)collimated light source are developed.Combining with the characteristic of LED point light source and the software of simulation,the light source model is simulated.And the secondary optics design of LED is executed by putting forward the design method of free curved surface collimation lens.By building 3D models to simulate,fabricating the collimation lens,and testing the light source effect,four groups of collimation light sources with ±10°beam angles are designed and fabricated.(4)High precision moving light field generation and control method are studied,including physical structure design of sensor's illuminate surface,light source design,high precision alternate light field generation,and high precision photoelectric conversion circuit design and so on.It provides a practical basis for obtaining high precise moving light field.The performance of moving light field is tested respectively in two kinds of sensor's prototypes.In this way,the feasibility of the above control method is verified.(5)Experiments of two kinds of time grating sensors are carried out in order to examine the actual effect of configured moving light field to realize the displacement measurement and working performance of sensor prototype.The error sources of linear time grating sensor system of configured moving light field are analyzed and calculated.According to the characteristic of error sources,a method of error correction which combined with hardware and software of linear interpolation is proposed.Experimental results indicate that in the range of 0mm~150mm,the accuracy of four-phase time grating is better than ±0.45?m and the accuracy of three-phase differential time grating is better than ±0.4?m.(6)The method of improving system stability is studied.The system stability of the various antipodes and differential structure sensor are compared and tested.And a digital filtering method of recursive average filter is proposed in order to improve the system stability.Experimental results indicate that the high stability measurement system could be obtained by adopting methods of differential structure,average effect of multiple antipodes,and recursive average filter etc.In conclusion,combined with the measurement principle of time grating,in the optical field,this dissertation provides a high precision displacement measurement method which adopts the space and time orthogonal modulation of light intensity.Based on this method,two kinds of light field type of time grating sensors with different structures are designed and developed.Experimental research indicate that the principle prototype has the advantages of low manufacturing cost,high measuring precision and good stability,etc.Therefore,the research of this dissertation not only builds a complete research system which composed of “light field,electric field,and magnetic field” for time grating sensor,but also provides a novel measurement method to realize high precision displacement measurement,which does not depend on the precision manufacturing technology for optical displacement measurement.