Research On 3D Fringe Projection Measurement Method Based On Time Phase Unwrapping

The three-dimensional measurement technology has greatly changed the way of life and production.Among them,3D topography measurement of digital fringe projection technique has the advantages of non-contact,fast,high-precision,low cost,easy popularization and simple operation,which has become a research hotspot and been widely used in industrial inspection,quality control,reverse engineering,rapid measurement,biological medicine,virtual reality and other fields.With the improvement of the quality of life and the development of industrial production,the requirements for 3D topography measurement of digital fringe projection technique are getting higher and higher,requiring faster and higher precision measurement.The fringe projection technique based on time phase unwrapping method has high reliability and accuracy.However,this method requires a large number of fringe patterns to be projected and acquired,and the processing data is large,the measurement time is long,and fast,real-time,and dynamic measurements cannot be performed.This paper focuses on the key issues of fast and high precision measurement of fringe projection based on time phase unwrapping method.1.The principles of linear growth method,fitting index method and fitting negative index method for time and phase unwrapping method are studied in detail.These methods need to collect and process a large amount of data,and the measurement speed is slow.Based on this,this paper proposes a method to reduce the data acquisition time.The method adds two fringe patterns based on the four-step phase shifting fringes.The six fringe patterns can obtain a wrap phase and an auxiliary phase.By using the relationship between the two phases,a new wrap with a frequency half the wrap phase can be obtained.Phase.That is to say,the method of a set of patterns can be two different frequencies of wrapped phase.The fitting index method and the fitting negative index method needlog₂ s sets of patterns?s is the maximum period number of the patterns?.In the case of four-step phase shift,4log₂ s sets of patterns are needed.This method requires3log₂ sfringe patterns,and reduces the pattern bylog₂ s fringe patterns,which can shorten the projection and acquisition time,data processing time,and improve the measurement speed to some extent.The feasibility of the method is proved by experiments.2.The principle of dual-frequency heterodyne method and three-frequency heterodyne method is described in detail,and the shortcomings of each method are analyzed.The error of the phase main value in the dual-frequency heterodyne method limitsthehigh-precisionmeasurementusinghigh-frequencyfringes.The three-frequency heterodyne method can use the high-frequency patterns,but the two-difference operation will amplify the error of the main-value phase.It may cause the heterodyne phase to be inaccurate,which may cause a jump error in the continuous phase of the expansion.Combined with the existing research results,a phase unwrapping method combining dual-frequency heterodyne and phase encoding is proposed.The phase of the heterodyne phase is unfolded by the phase-encoding fringe,and the period of the heterodyne phase does not cover the whole field of view,thereby breaking the limitation of the phase main value error on the high-frequency patterns,and only the sequential heterodyne is performed,without the continuous phase jump caused by the amplification of the phase error of the principal value.The feasibility and effectiveness of the method are verified through comparative experiments.3.A new time phase unwrapping method is proposed using the designed fringes.The method only needs 6 fringes and simple algorithm.The effectiveness and feasibility of the method are verified by experiments.