Feature size
Define the smallest defect, edge or code width you must detect or measure reliably.
Knowledge · Fundamentals
Camera resolution, FOV and working distance, one geometry.
The smallest feature you must see, the available space and the lens together decide whether your sensor has ‘enough pixels’, not the megapixel claim alone.
Decision
Start from the feature, not the catalogue
Resolution only matters once you know how many pixels you want across the smallest critical feature width, and whether lighting and motion keep those pixels usable.
Pixels across the feature
Rule of thumb: several pixels across that width, more for gauging, fewer for coarse presence. Always validate.
FOV & working distance
FOV must cover the part (plus margin) at the available WD. Lens + sensor size close that triangle.
Approach
Practical sequence
Keep depth of field, lens distortion and mount angle in the same conversation, otherwise the geometry works on paper but not on the line.
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01
Lock FOV and WD
Measure the real mount position and clearance, not the ideal catalogue WD.
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02
Choose sensor + lens
Pick a sensor size and focal length that deliver FOV at that WD, with room for focus and depth.
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03
Check pixel size
Compute pixels/mm or pixels across the feature; check whether gauging or detection needs that density.
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04
Validate optics and lighting
Samples under line conditions: motion blur, glare and depth of field can make ‘enough pixels’ useless.
Limits
What this guide does not promise
No universal megapixel table. No substitute for lens calculation or feasibility testing on real parts.
Gauging ≠ detection
Sub-pixel gauging needs different margins than presence/absence.
Lens first when WD is tight
Sometimes another lens or a second camera beats a more expensive sensor.
Depth of field
Thicker parts or tilt need DOF awareness, resolution alone will not fix it.
Work the numbers on your part
Send feature size, FOV sketch and available WD, we check whether the stack holds.