Surface Topography And Vibration Measurement Based On Fringe Projection

In the field of industrial measurement,acquiring a three-dimensional information reconstruction model of an object surface is a basic step for subsequent analysis and decision making,and it is also a prerequisite for measuring a vibrating object.Traditional contact measurement methods can only measure static objects due to the limitation of measurement methods.In order to be able to perform fast full field measurements,a non-contact optical measurement method is required.Fringe projection and Fourier transform profilometry greatly meet the requirements of vibrating object measurement with its fast calculation speed,instantaneous information acquisition and wide application scenarios.In this paper,the three-dimensional shape of the surface of a static object is obtained by Fourier transform profilometry based on fringe projection method,and a low-frequency vibration measurement system based on fringe projection is proposed.Then the optical measurement of a vibrating object is carried out,vibration frequency and amplitude are obtained later.Aiming at the phase blur problem in the phase analysis process,a composite grating projection method combining dot matrix projection and fringe projection is proposed,and the measurement accuracy of different types of stripe gratings as projection patterns is compared and analyzed.Firstly,this paper introduces the necessity of vibration measurement and the method of surface measurement of the current stage.The principle of fringe projection and Fourier transform profilometry is theoretically deduced,and the gradient measurement limit of this method is analyzed in detail.Secondly,the complex grating coding method based on lattice projection is introduced by explaining the inevitable error accumulation in phase blurring and phase unwrapping in the phase measurement method,combined with the accuracy of dot matrix projection and the full field property of fringe projection.The precision of data processing is exceeded.Then,combined with Fourier fringe profilometry applied to the theoretical basis of vibration measurement,a controllable vibrating object was measured.By comparing the image acquired by the camera with the reference image,Fourier transform,window filtering,inverse Fourier transform and height restoration are sequentially performed,and a specific reference point in the height restored graph is extracted,and the frequency and amplitude of the object is analyzed through the height distribute curve.After analyzing the frequency and amplitude measurement sensitivity and resolution using the square wave as the projection pattern,sine waves and triangular waves were respectively used as projection patterns,and the measurement results were compared.Finally,the possible errors in the measurement process are discussed and theoretically analyzed,and the methods to reduce the measurement error are proposed from different fields.At the same time,under the premise of improving the experimental algorithms and equipment,the possibility of real-time measurement is verified,and the conclusions and prospects are summarized,and the future research direction is planned.