Modeling And Error Analysis For Time Of Flight In The 3D Imaging Application

The three-dimensional(3D)imaging techniques,which include the scanning and the non-scanning 3D imaging technology,have been applied to practical fields such as navigation,monitoring,recognition and virtual reality,by far.For the scanning 3D imaging technology,its distance measurement not only is longer but also it can obtains distance or two-dimensional information.However,it is difficult to be widely used,because of the heavy weight,high power consumption and expensive prices.The non-scanning 3D imaging technology can provide both a 2D image and exact distance values in real-time,and the stereo vision effect is stronger,so it is studied extensively.For the non-scanning 3D imaging technology,it can be realized by the direct and the indirect time-of-flight(TOF)measurement.For the direct TOF measurement technology,it mainly use the characteristic of pulse modulation.And it has the advantage of long-distance detection and not easily affected by the outside light.However,the indirect TOF measurement is mainly applied in indoor environment due to that its distance measurement is realized by the continues wave signals passing through a modulation-demodulation wave.Comparing with the direct TOF measurement,the distance of the indirect TOF measurement is shorter.But,the accuracy of the indirect TOF measurement is easy to be influenced by ambient light and aliasing effect.To overcoming these defects,we in this thesis focus on the suppression of ambient light and aliasing effect.From the measurement principle,the system modeling,the error analysis and the compensation methods,we obtain a series of results of the guiding significance by making use of the indirect TOF measurement.The structure of the thesis is the following.We first describe the development states,the research background and significance of the 3D imaging system.Subsequently,the main technology and the development trends of the TOF measurement are introduced.And then the influence of the both direct and indirect TOF technology on the ranging results are described.The distance between the target and the camera can be obtained by the indirect TOF measurement.Therefore,we first deduce the physical expressions of the distance measurement by means of the modulation-demodulation wave,such as,cosine wave-cosine wave,cosine wave – square wave,and square wave-square wave.Then,the ranging accuracies of the above three methods are obtained by the calculation of theMATLAB/SIMULINK modeling.It is shown that in these methods,the accuracy of cosine wave-cosine wave method is the highest,and closely followed by the cosine wave-square wave method,and the lowest accuracy is the square wave-square wave method.When the indirect TOF measurement is applied to the circuit,it is easy to be realized of the high power modulation of the cosine wave-square wave method by comparing with the cosine wave-cosine wave method.And the influence of photon noise on the cosine wave-square wave method is less than that on the cosine wavecosine wave method.Therefore,we deduce the indirect TOF physical expressions by means of the cosine wave-square wave method being served as the modulationdemodulation wave.Subsequently,the MATLAB/SIMULINK model of the four exposure method is proposed.By calculating the phase of the MATLAB/ SIMULINK model,it is found that the best integration and sampling time are 0.05 ms and 10 ns,respectively.In order to increase the distance measurement accuracy,some unsatisfactory factors must be depressed.Due to that these factors results in an aliasing effect,we renew to calculating the distance by the MATLAB/SIMULINK simulation.The corresponding output model are also replaced by a new operation symbol.Under the consideration of the aliasing effect,we find that the average value of distance error is half of that of in absence of the aliasing effect.Finally,we make a series of summary on the mainly work during the master's period.And the future research studies on the application of 3D imaging TOF method are prospected.