Multi-head Reflective Intensity Modulation Fiber Optic Sensor Development

In this paper,the light intensity compensation technology,the light field distribution end of the fiber,the intensity modulation characteristic function,and the weak photoelectric signal detection principle are used to analyze and study the fiber sensor.A dual-path intensity modulation fiber sensor is proposed.Requires the addition of a lens system,which can change the measurement accuracy and linear range of the fiber optic sensor,and also increase the distance between the probe and the measured object.It is expected to make breakthroughs in fiber optic sensor measurement methods and technologies in order to achieve the measurement of the surface Measured under conditions of change in reflectivity for the purpose of high accuracy and high efficiency.Firstly,the light field distribution at the exit end of the transmitting fiber of the optical fiber sensor is studied.Under the premise that the transmitting beam has specular and diffuse reflection on the reflective surface,the light emphasis characteristic function of the optical fiber sensor and the distance between the optical fiber probe and the reflective surface are obtained through theoretical analysis.The relationship between the distance,the theoretical model of the displacement measurement of the optical fiber sensor was established,and the influence of the roughness of the reflecting surface and the parameters of the optical fiber on the characteristic curve of the light enhancement system were analyzed by using Matlab simulation.The effects of the smooth mirror surface and the complete diffuse reflection surface on the modulation characteristics,as well as the effects of the fiber-to-axle distance,core radius,and numerical aperture of the fiber on the modulation characteristics when the beam is diffusely reflected on the surface of the object are studied.The results show that the intensity modulation characteristics of specular reflection are significantly better than that of diffuse reflection surfaces,and the peak value of the modulation function is five times that of diffuse reflections,and the intensity modulation characteristics gradually decrease as the roughness of the reflection surface increases in sequence.As far as the design of the optical fiber sensor is concerned,the axial distance of the transmitting and receiving optical fibers and the core diameter of the transmitting optical fiber are reduced within the range allowed by the conditions,so that the intensity modulation function of the optical fiber sensor achieves the optimal state for measurement and improves the measurement accuracy of the sensor.Secondly,by exploring the principle,advantages and disadvantages of the intensity compensation method,the overall optical path structure of the dual optical path intensitymodulation fiber sensor is designed,and the optoelectronic devices included in the sensor are designed and selected,and the overall optical path structure of the intensity modulation fiber sensor is designed as a whole,Followed by the design and selection of each optoelectronic device.In addition,the mechanical structure of the optical fiber sensor is analyzed and designed,including the design of the connecting sleeve of the microscopic objective lens,the design of the optical fiber probe fixing device,the design of the optical fiber probe fixing sleeve,the clamping and fixing of the spectroscopic element,the design of the connecting cube,etc.The block is used as the basis for the mechanical mechanism design to ensure the coaxiality of the dual optical path structure and reduce the measurement error of the sensor.Completed the analysis and design of the optical fiber sensor hardware circuit,on this basis,the design of the pulse modulation circuit was completed,and the NE555 chip was used to realize the signal generation circuit with adjustable pulse width.The circuit used the change of the external resistance to adjust the duty cycle.The photoelectric conversion and amplifying circuits of weak signals are designed in order,to realize the conversion and amplification processing of optical signals to electrical signals,AD data acquisition,digital filtering and phase sensitive detection,and filtering of stray signals,so that the measurement The signal of information was passed.Finally,according to the designed overall optical path structure of the optical fiber sensor,the assembly of each mechanical structure part of the optical fiber sensor is completed,and a verification experiment of the intensity-modulated optical fiber sensor is realized.Experiments are performed when the reflecting surface is specular reflection and diffuse reflection,and the main performance(linear range and sensitivity)of the intensity-modulated fiber optic sensor in displacement measurement is tested.The experimental results show that the measurement sensitivity of the sensor on specular reflection is better than that of rough surface,and the linear range of the back slope is higher than the linear range of the front slope.