Traditional measurement methods for optical displacement have higher demands for the environment and it is difficult to improve the manufacturing precision of measuring devices.Therefore,a novel linear displacement measurement method was proposed by using the alternating light field as measuring medium.On the basis of the method,a light Intensity orthogonal modulation type displacement sensor was designed.The method combined two electrical standing waves with orthogonal changes into the electrical traveling wave signals,then,it measured the time sequence of traveling waves to achieve the spatial displacement measurement.In order to explore the sensing mechanism of the sensor,the actual measurement model of the sensor was derived,and the influence of key factors associated with the sensing mechanism on the measurement error was analyzed in detail.According to the analysis of the measuring principle and model theory,a sensor prototype was developed and various critical factors effecting on measurement error levels were tested.Then,sensor structures and parameters were optimized.The experimental results show that measuring errors of the optimized sensor are controlled within ± 0.5 μm in the measuring range of 108 mm,which demonstrates that proposed method is a new displacement detection solution without demands for precise photolithographic processing.