Research On Light Field Projection Of 3-Dimensional Measurement

Three-dimensional imaging and sensing technology is an important way to obtain real three-dimensional world information,and provides a data foundation for reconstructing the true geometric shape of objects and subsequent three-dimensional modeling,detection,and recognition.With the development of artificial intelligence and big data,the acquisition and application of three-dimensional shape data of objects have received more and more attention,which has also promoted the vigorous development of three-dimensional measurement technology.It has a wide range of applications,such as face recognition,target detection,VR(Virtual Reality Technology)and product inspection,which also puts forward higher requirements for three-dimensional measurement.The structured light three-dimensional measurement technology is a commonly used optical three-dimensional measurement technology,usually using sinusoidal fringe coding,the measurement accuracy can reach one tenth to several hundredths of an equivalent wavelength,and the frame rate can reach tens of kHz.The sinusoidal fringes generated by the projector are actually realized by the different brightness of multiple pixels,and the pixels have a certain size limit,so the period of the fringe pattern on the projected display cannot be too small.The situation in a small area is not suitable.The response time of the digital projector itself is on the order of microseconds,which is lower than the frame rate of high-speed cameras.This paper proposes a new structured light projection method,theoretically analyzes the projection principle,and designs a sinusoidal fringe field projection module.The module has the advantages of compact structure and simple control.In addition,the backlight uses LED chips,and the response time is in the order of nanoseconds.In theory,high-speed measurement can be achieved.The main research contents of the paper are as follows:1.Analysis and comparison of structured light coding methods;Several commonly used structured light coding methods are analyzed,and the advantages and disadvantages of each method are compared.The basic principles of Fourier transform profilometry and phase shift profilometry based on sinusoidal phase coding are introduced.Speed and measurement are measured in phase shift profilometry As a compromise between accuracy,the four-step phase shift method was chosen as the research method of the thesis.2.Analysis and comparison of structured light projection methods;The development of structured light projection method is briefly introduced,and several commonly used techniques based on binary pattern defocusing to form sinusoidal stripes are analyzed.Because only 2 levels of gray are used,the measurement speed is improved,but these defocusing methods are subject to the projector lens and the degree of control is not good.3.Research on projection fringe based on binary sine pattern;A method for generating sinusoidal fringe patterns based on binary sinusoidal patterns is proposed.Compared with traditional methods,this method does not require defocusing.Due to the negative film method,the size of the sinusoidal pattern can be smaller and finer,and has the advantages of a binary pattern,fast switching speed,and can be used for high-speed measurement.The effects of light expansion direction and defocusing on the formation of sinusoidal fringes were analyzed through simulation.A sinusoidal fringe field projection module was designed and a three-dimensional measurement system was built to verify the method.