All-fiber Rotation Speed Measurement And Signal Processing Based On Laser Speckle Interferometry

As a common non-contact measurement method,optical interference method has the characteristics of nondestructive,high precision and wide applicability.Fiber optic interference sensing is widely studied and applied because of its large dynamic measurement range,anti-electromagnetic interference and flexible structure,which can work in extreme environment.However,when using optical fiber interferometer sensor,the surface of the measured object is mostly mirror,and the rough surface is less.Therefore,in this paper,optical fiber sensor is applied in the measurement of motion parameters of objects with rough surfaces.Aiming at the speed measurement problem,an all-optical fiber speed measurement method based on laser speckle interference is proposed.At the same time,to determine the rotation direction of the rotating object,the method of all-fiber Angle measurement and rotation direction determination based on laser speckle interference is studied.The cross-correlation algorithm is used to process the signals in the measurement of rotational speed and Angle.The specific research contents are as follows:1.Establish the optical fiber laser speckle interference model,that is,after the laser is transmitted through the optical fiber,it irradiates on the object with rough surface and scatters,and part of the scattered light returns back to the optical fiber to interfere with the reflected light from the inner end face of the optical fiber.The intensity expression of interference signal is deduced,and the formula and properties of cross-correlation algorithm are described,which provides a theoretical support for all fiber speed and angle measurement based on laser speckle interferometry.2.An all-fiber speed measurement method based on laser speckle interference is proposed to measure the speed of rotating objects with rough surfaces.In this method,two non-interfering interferometric speckle signals are generated by a circulator with only one light source,and the two interferometric speckle signals are cross-correlated.Because the rotation of the object is periodic motion,the rotation period of the object can be obtained by analyzing the cross-correlation function of the two interferometric speckle signals,and the reciprocal of the period is the rotational speed of the object.Experiments show that the relative error of the method is less than 0.5%.3.In order to determine the rotation direction of a rotating object with rough surface,an all-fiber Angle measurement and rotation direction determination method based on laser speckle interference is proposed.The Angle to be measured is the Angle formed between the two incident points and the center of the circle when the two beams are on the same circle.Two interferometric speckle signals are formed when the object rotates,and the two signals are analyzed by cross-correlation algorithm.By analyzing the cross-correlation function,the time delay of the point passing through two beams of light and the rotation period of the object are obtained.The ratio of time delay and period is the ratio of Angle to be measured and circumference Angle,and then the Angle can be obtained.The experimental results show that the relative error of this method is less than 5% within 180.0°.The direction of rotation of the rotating object can be determined by measuring the Angle.