Machine Vision Basics for Robot Cells
Lighting first
Most vision failures are lighting failures. A stable, directional light source with the part presented consistently beats a higher-resolution camera with poor illumination. Test with production parts, including the dusty and dented ones.
| Component | Function | Typical pitfall |
|---|---|---|
| Lighting | Make the feature visible and repeatable | Ambient light changes through the day |
| Camera | Resolution, frame rate, interface | Ignoring the field of view needed |
| Lens | Working distance and magnification | Distortion left uncorrected |
| Calibration | Map pixels to millimetres | Calibrated once, never rechecked |
Calibration and tolerance
Calibrate at the same working distance and temperature as production, and define the tolerance the cell needs, for example 0.3 mm at the gripper. Then measure the real distribution, not a single good sample.
Design for failure
Decide what happens when vision is not confident: reject, retry, or ask a human. A cell that silently acts on a low-confidence result is the one that eventually ships the wrong part.