Reducing the uncertainty of laser straightness measurements via local saturation of imaging sensors

This paper investigates causes of center detection errors in laser straightness measurements for precision positioning applications and proposes the calibration of these errors by utilizing the reversal method after reducing the center detection uncertainty. The uncertainty arising from unknown imaging errors, such as spatially varying pixel sensitivity and sensor pollution, is diminished by saturating the imaging sensor. The results demonstrate that the uncertainty can be reduced by a factor of 4.8, from $2.19 \mu \mathrm{m}$ to $0.45 \mu \mathrm{m}$. This reduction justifies the application of the reversal method to calibrate the remaining center detection error, attributed to the shape of the laser beam cross-section in the image. Consequently, this enables straightness measurements with a repeatability of $0.34 \mu \mathrm{m}$.