usb-cam (3)攝像機標定文件-ORB-SLAM標定文件

http://www.luohanjie.com/2017-04-05/the-problem-of-calibration-data-in-orb-slam2.html

ORB_SLAM2中標定數據的問題

 

在使用ORB_SLAM2的過程中，我使用Kinect v2作為攝像機，而在使用之前需要對Kinect進行標定的工作。幸好iai_kinect2這個驅動提供了標定的工具^[1]。按照說明操作，獲得了標定的數據，如calib_color.yaml文件中包含了攝像機的內參和畸變等參數：

%YAML:1.0
cameraMatrix: !!opencv-matrix
   rows: 3
   cols: 3
   dt: d
   data: [ 1.0550860028898474e+03, 0., 9.7022756868552835e+02, 0.,
       1.0557186689448556e+03, 5.2645231780561619e+02, 0., 0., 1. ]
distortionCoefficients: !!opencv-matrix
   rows: 1
   cols: 5
   dt: d
   data: [ 5.0049307122037007e-02, -5.9715363588982606e-02,
       -1.6247803478461531e-03, -1.3650166721283822e-03,
       1.2513177850839602e-02 ]
rotation: !!opencv-matrix
   rows: 3
   cols: 3
   dt: d
   data: [ 1., 0., 0., 0., 1., 0., 0., 0., 1. ]
projection: !!opencv-matrix
   rows: 4
   cols: 4
   dt: d
   data: [ 1.0550860028898474e+03, 0., 9.7022756868552835e+02, 0., 0.,
       1.0557186689448556e+03, 5.2645231780561619e+02, 0., 0., 0., 1.,
       0., 0., 0., 0., 1. ]

 

%YAML:1.0
    #--------------------------------------------------------------------------------------------
    # Camera Parameters. Adjust them!
    #--------------------------------------------------------------------------------------------

    # Camera calibration and distortion parameters (OpenCV) 
    Camera.fx: 1.0550860028898474e+03
    Camera.fy: 1.0557186689448556e+03
    Camera.cx: 9.7022756868552835e+02
    Camera.cy: 5.2645231780561619e+02

    Camera.k1: 5.0049307122037007e-02
    Camera.k2: -5.9715363588982606e-02
    Camera.p1: -1.6247803478461531e-03
    Camera.p2: -1.3650166721283822e-03
    Camera.k3: 1.2513177850839602e-02

    Camera.width: 960
    Camera.height: 540

    # Camera frames per second 
    Camera.fps: 30.0

    # Color order of the images (0: BGR, 1: RGB. It is ignored if images are grayscale)
    Camera.RGB: 1

    # IR projector baseline times fx (aprox.)
    Camera.bf: 40.0

    # Close/Far threshold. Baseline times.
    ThDepth: 50.0

    # Deptmap values factor 
    DepthMapFactor: 1000.0

    #--------------------------------------------------------------------------------------------
    # ORB Parameters
    #--------------------------------------------------------------------------------------------

    # ORB Extractor: Number of features per image
    ORBextractor.nFeatures: 1000

    # ORB Extractor: Scale factor between levels in the scale pyramid     
    ORBextractor.scaleFactor: 1.2

    # ORB Extractor: Number of levels in the scale pyramid    
    ORBextractor.nLevels: 8

    # ORB Extractor: Fast threshold
    # Image is divided in a grid. At each cell FAST are extracted imposing a minimum response.
    # Firstly we impose iniThFAST. If no corners are detected we impose a lower value minThFAST
    # You can lower these values if your images have low contrast            
    ORBextractor.iniThFAST: 20
    ORBextractor.minThFAST: 7

    #--------------------------------------------------------------------------------------------
    # Viewer Parameters
    #--------------------------------------------------------------------------------------------
    Viewer.KeyFrameSize: 0.05
    Viewer.KeyFrameLineWidth: 1
    Viewer.GraphLineWidth: 0.9
    Viewer.PointSize:2
    Viewer.CameraSize: 0.08
    Viewer.CameraLineWidth: 3
    Viewer.ViewpointX: 0
    Viewer.ViewpointY: -0.7
    Viewer.ViewpointZ: -1.8
    Viewer.ViewpointF: 500

 

在解決了雙重標定的問題后^[3]，我使用qhd質量(960x540)的圖片跑ORB_SLAM2程序，發現無論是單目模式還是RGBD模式的結果都不堪理想。經過排查后，發現還是標定數據的問題。

在iai_kinect2的標定程序中，使用的FullHD(1920x1080)分辨率圖片，所以得到的計算機內參數據是針對1920x1080這個分辨率的；而我在ORB_SLAM2中，使用的是QHD(960x540)分辨率的圖片。為了使用標定數據與使用照片對應，需要對1920x1080下的標定數據作出處理，對內參數據根據分辨率按比例進行縮減^[4]，在這里，需要對fx

 

的值乘以一個0.5。

 

%YAML:1.0
    #--------------------------------------------------------------------------------------------
    # Camera Parameters. Adjust them!
    #--------------------------------------------------------------------------------------------

    # Camera calibration and distortion parameters (OpenCV) 
    Camera.fx: 527.54300144
    Camera.fy: 527.85933447
    Camera.cx: 485.11378434
    Camera.cy: 263.2261589

    Camera.k1: 5.0049307122037007e-02
    Camera.k2: -5.9715363588982606e-02
    Camera.p1: -1.6247803478461531e-03
    Camera.p2: -1.3650166721283822e-03
    Camera.k3: 1.2513177850839602e-02
    
    ...