Depth Measurement Based On Defocus Method Using Liquid Crystal Lens

In recent years,artificial intelligence has entered a golden development period,and computer vision applications are becoming more and more common,such as face brush payment,3D model restoration,and autonomous driving.An important part of these technologies is acquiring three-dimensional information of the scene.The three-dimensional information is obtained,which broadens the dimension of the information and paves the way for further acquisition of other information.Cameras can only acquire two-dimensional images,which makes the original three-dimensional scenes unable to be completely acquired.The depth measurement technology allows us to obtain the relative distance relationship of each object in the actual scene,which makes up for the shortcoming of the loss of 3D information.There are many current methods of depth measurement.This topic mainly uses the liquid crystal lens as the imaging device to obtain the depth information of the scene through two methods: defocus and focus.The liquid crystal lens is a new type of imaging device with low power consumption,electronically controlled focusing,lightness and compactness.Defocus method mainly calculates the distance by analyzing the difference in the defocus amount between different distance object points.The focus rule is to find the clearest frame in a series of images focused at different positions by the focus evaluation operator,and then to obtain the depth indirectly through the Gaussian formula.Combining the liquid crystal lens with these two methods to obtain depth is very innovative,not only can make up for the shortcomings of the two methods,but also improve efficiency and extend the life of the system.The main work and innovations of this article are as follows:Depth measurement based on the defocus method of liquid crystal lens is proposed.The traditional defocus method for measuring depth requires moving the sensors in the imaging system to collect the required images.Long-term mechanical movement will not only shorten the life of the system,but also reduce the accuracy.On the other hand,in order to avoid the change of the system magnification caused by moving the sensor,the imaging optical path will also be changed to the imaging side telecentric optical path,and the telecentric optical path generally has a large volume.The use of a liquid crystal lens that can be electrically controlled for focusing not only does not require any mechanical movement,but also because the lens itself has a relatively small aperture,acting as a diaphragm in the system can avoid changes in magnification.In this project,I analyze the expression of blurring amount in the imaging system where the liquid crystal lens acts as a focusing device from the perspective of geometrical optics.The feasibility of this method is verified by simulation analysis.In addition,I also analyzed the effect of the amount of blur on the result,the depth value of the initial focus surface,and the depth measurement accuracy.A depth measurement based on the liquid crystal lens focusing method is proposed.Traditional focus method depth measurement requires constantly moving a part of the imaging system so that it can continuously change the focus position and collect the required image set.Liquid crystal lenses rely on the rotation of liquid crystal molecules to achieve zooming.We found that we can use the continuity of the liquid crystal molecules to achieve continuous zooming,that is,to quickly scan objects at various positions in the scene during a switching of the driving voltage.This feature can not only avoid the continuous movement to change the focus position to acquire images,but also keep the image magnification constant during scanning,which greatly improves efficiency.