Camera Calibration: pixel focal length and millimeter focal length conversion

1. pixel focal length and millimeter focal length conversion
  Fu = Ku * DPX;
  FV = Kv * dpy;
1) ku and KV are pixel focal lengths in the X (U) and Y (v) Directions of the internal camera matrix;
2) Fu and FV are the millimeter focal lengths in the X (U) and Y (v) Directions of the camera respectively;
3) DPX and dpy are measured in mm/pixel;
4) DPX and dpy indicate valid X (y) dimension of pixel in frame Graber, respectively, and the effective size of pixels in the horizontal (vertical) Direction of the imaging plane.

2. Calculate the pixel interval between the horizontal and vertical directions based on the fccdsize of the CCD size. The unit is mm)
1) DPX = DX * NCX/nfx;
  Dpy = Dy;

2) dx = (1/fccdsize * 25.4*4/5)/picture_cx;
  DY = (1/fccdsize * 25.4*4/5)/picture_cy;
Note: Dx and Dy are respectively X (y) dimension of camera's sensor element (in mm );
   25.4 meaning: 1inch inches =25.4mm;
   4 and 3 represent the X-and y-direction pixel ratios of CCD, which are generally the aspect ratio of the image;
   In the format, picture_cx and picture_cy are generally the width and height of the image.
3. NCX is the desired number (provided by the manufacturer) in the X direction, which is generally equal to the image width.
  Nfx is the number of pixels sampled per line of the camera, and the X-direction size of the image (number of pixels), which is generally equal to the width of the image.
  Fccdsize is the CCD size, which is generally 1/2, 1/3, 1/5, etc. camera parameters are provided by the manufacturer.