Location of the holes

The BlobAnalyser tool is used to locate the holes. With this tool the following information can be extracted:

• Diameter (horizontal)
• Diameter (vertical)
• FormFactor
• Eccentricity
• Area
• Perimeter
• X/Y position of the hole
• others

Calibration

• Set up the zoom and focus for the holes
• Put a Ronchi Ruling under the camera (see Figure on the right side)
• Count the number of line pairs in the viewport
• With this information and the size of the viewport (in pixels) calculate the size of one pixel (see calculation below)

Calculation

(The used Ronchi Ruling has 100 line pairs per 1 inch)

• Calculate the size of 1 line: 100 lines = 1 inch = 0.0254 m
  1 line = 0.0254 / 100 = 0.000254 m
• Calculate the size of 1 pixel (29 lines are counted in the viewport)
  29 lines = 29 * 0.000254 = 0.007366 m = 640 pixel
  1 pixel = 0.007366 / 640 = 0.000011509375 m
  
• Calculate the size of the holes
  Hole 0 = 139 pixel => 139 * 0.000011509375 = 1.60 mm
  Hole 1 = 151 pixel => 151 * 0.000011509375 = 1.74 mm