Research On Detecting Optical Fiber Geometric Parameter Based On Machine Vision

Detecting geometric parameters of new type specific fiber is precondition and guarantee that researching property of new type specific fiber and ensuring quality of processing of production. With the fast development of machine vision technology, vision measurement technology is fast development and extensive use, and it is widely used in many fields as a way of non-contact measurement. The paper is mainly study the measurement of fiber geometric parameters based on machine vision.Firstly, the paper research philosophy of measurement of detecting fiber geometric parameters based on machine vision technology, fix testing program and testing system configuration according to character of D type fiber and specific fiber end face. Measuring system contain CMOS camera, imaging system, lighting system, collecting image system and processing software system, meanwhile detailed analyze the choice of camera, lens, lighting, and lighting method. Secondly, in order to raise testing accuracy, paper introduced the conception and method of focusing, meanwhile emulate some kinds of focusing function.The paper focus on fiber geometric parameters testing system involved image processing algorithm. Testing system preprocess with median filtering of 3x3 window, according to fiber image feature, many experiment and emulation. Testing system chose good noise immunity of Canny operator as a full pixel edge detection operator, when measuring the length of D type fiber. Testing system apply gray moment sub-pixel algorithm, and the algorithm is simple and high precision. When testing specific fiber, according to the feature of fiber end face, firstly, testing system do grey level histogram of fiber end face image, and get outer-cover and air-hole of binary image by level histogram, than compute radius and circle centre of outer-cover and air-hole through Hough transform. Secondly get two ellipse core of fiber image by level histogram again, extract contour of two ellipse-core fiber applying for edge chain code method, than compute semi-minor axis, semi-major axis and ellipse center by least squares fitting.Lastly, the system use standard single-mode fiber to measure fiber diameter and get the testing of result. The system also measure two ellipse-core fiber geometric data, and the geometric data contain Cladding diameter and Center position, air-hole diameter and center position, long axis and short axis of elliptical core, the center coordinates. Through experimental tests, fiber geometry detection system can measure the length of D type fiber in-line, and measure Special fiber end geometry correctly, accuracy to meet the test requirements.