Mechatronics and Algorithms to Analyse and Control the Laser Beam Spot Size for 3D Micro-printing Machine

Recent developments in digital manufacturing see widespread use of lasers of various kinds be it additive or subtractive methods.All laser beam-based technologies require control over the laser beam spot size to get the desired outcome.For systems requiring a frequent change of focusing optics or in-situ change of spot size while processing, a system having automatic control over laser spot size would be required.This paper proposes a mechatronic solution for the same (named as laser beam focusing system (LBFS)) specifically for an in-house micro-stereolithography (MSL) setup and proposes algorithms for detection of focus, estimation of spot size, and depth of focus (DOF) of laser.In this setup, a laser beam steered by mirrors is scanned over a photodiode positioned at a target plane or printing plane of MSL.This photodiode is masked partially with a sharp-edged metal sheet.Algorithms for scanning and processing the data obtained from photodiode are developed for automatic detection of the focal distance (i.e., focusing lens position) at the target position.Finally, the effectiveness of detection of focus spot is demonstrated fabricating high-resolution micro-features in MSL system.