What size pinhole can be reliably detected using visual inspection? Our customer wants hole defects logged with cartesian coordinates, any hole larger than 0.010 inch diameter. A missed defect is grounds to reject the lot. Our initial response was this requirement is not humanly possible using visual inspection, even with backlighting. Our firm has not budgeted for a camera-based inspection system, and if we tried to adopt a turnkey vision system, implementation and validation would likely exceed project lead-time constraints. The customer’s response was what size hole can be reliably identified? Can you help me find published data on visual inspection for pinholes?
Some important details: we are working with 0.002 inch thick paper, 36 inches wide, moving at 6 feet/min roll-to-roll. At 20 inches viewing distance, I calculated a 1.5 inch field of focus (2°). For baseline data, I found 8 thin spots >0.010” per square yard using ImageJ software (unless the hole is circular and perpendicular to the paper, the true size is difficult to discern). For reference, I am saying 0.010 inches is the size of the period (full stop) at the end of this sentence.
Some important details: we are working with 0.002 inch thick paper, 36 inches wide, moving at 6 feet/min roll-to-roll. At 20 inches viewing distance, I calculated a 1.5 inch field of focus (2°). For baseline data, I found 8 thin spots >0.010” per square yard using ImageJ software (unless the hole is circular and perpendicular to the paper, the true size is difficult to discern). For reference, I am saying 0.010 inches is the size of the period (full stop) at the end of this sentence.
