Research On UAV Ranging Technology Based On Infrared And Visible Images

Nowadays,Unmanned Aerial Vehicle(UAV)is widely used in various fields and has a huge space for development.Cases of UAVs crashing out of control causing casualties and stopping normal flights have occurred frequently,thus the effective supervision of UAVs will become an imperative.Technically speaking,the key of supervising UAVs divides into identification and ranging-localization.Since the image sensor has the advantages of low cost and high positioning accuracy,it has been rapidly developed in engineering projects.Meanwhile,in order to make up for the insufficiency of a single sensor and overcome the effects of extreme weather such as heavy fog and darkness,combination of the infrared camera and the visible light camera has become the main method for UAVs supervision.Based on requirements of a science and technology project of the CAAC Southwest Regional Administration,this paper mainly includes the following aspects:(1)An aluminium based chessboard is used to calibrate the infrared camera.Besides,in order to improve contrast,the calibration data of the infrared camera is achieved successfully by heating the chessboard.Because aluminum has a high reflectivity about 95% to far infrared rays,thus the infrared camera can receive reflected infrared light to achieve the goal of chessboard imaging.(2)In this paper,we add spatial information by combining phase consistency and mutual information.The matching accuracy is improved effectively.In the multi-spectral image registration,because of the different imaging mechanism,the distribution of image's pixel gray value is non-linear.So the traditional matching algorithm based on gray correlation and image feature cannot be used simply.Since the mutual information measure does not need to assume the relation between the gray of image with different imaging principle,so it is very good in the field of multi-spectral image registration.But because the mutual information only utilizes the statistic characteristic of the gray,the spatial position relation between pixels in the image is neglected.The phase consistency can extract the edge information of the image.Combined with phase consistency,it makes up for the lack of spatial position relation between the pixels of the mutual information.(3)We can use the difference of pixel gray value to achieve the adaptive change of the matching window.In the stereo matching process,the choice of matching window shape and size is a very important problem.The matching window must be large enough to contain enough intensity changes,as well as small enough to avoid the effect of projection distortion.If the matching window is too small to contain enough intensity changes,a poor parallax estimation will be obtained because the signal-to-noise ratio is too low.Conversely,if the matching window is too large which causes the problem of containing the scene points with different depths,the different projection distortions of the left and right images will result in mismatch problem.The infrared image can reflect the thermal radiation information of different objects.The different gray values can reflect the regional feature to some extent,so the gray information of the infrared image can be used as the reference of the region segmentation,so according to this feature,the adaptive transformation of the matching window is achieved.