Laser Beam Positioner Synchronization with Constant Pulse Rate
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Solution Overview
Problem
Laser processing systems face issues with pulse energy variability and transient effects due to non-constant trigger signal timing, leading to inconsistent laser output and reduced processing quality.
Innovation Solution
A method and system that synchronize beam axis position and velocity with constant laser pulse repetition rate, using a pulse-picking device and controller to ensure stable and predictable laser pulse characteristics, reversing the master-slave relationship between the beam-positioning system and laser to maintain a constant frequency pulse train.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the beam-positioning system generates trigger signals to fire laser pulses only when the beam axis arrives at target locations (position-based control), then the laser pulses are delivered at the correct positions on the workpiece, but the timing of the trigger signal pulse train becomes non-constant, causing transients in laser output such as initial hot pulses, low-frequency average power drift, and increased pulse-to-pulse variability
Solution Approach 1:
The patent inverts the traditional master-slave relationship by making the laser the master system that generates pulses at a constant repetition rate, while the beam-positioning system becomes the slave that directs pulses to desired locations. This is achieved by using a pulse-picking device (acousto-optic modulator) controlled by the laser system to gate the constant-rate pulse train, allowing only selected pulses to reach the workpiece while maintaining constant laser operating conditions
Solution Approach 2:
The patent introduces a pulse-picking device (acousto-optic modulator) as an intermediary between the laser and the workpiece. This mediator selects which pulses from the constant-rate laser output are allowed to pass through to the workpiece, enabling position control without disrupting the laser's constant operation. The AOM acts as a gate that can be opened or closed for specific pulses based on beam position requirements
2Manufacturing precision
If the laser operates at low power with pulses fired only when beam positioner arrives at target locations (off by default approach), then the processing is precise at target locations, but the duty cycle of laser pulses is relatively low and the laser does not operate at steady state
Solution Approach 1:
The patent maintains continuous useful action by keeping the laser operating continuously at a constant repetition rate rather than turning it on and off. The laser produces a continuous train of pulses at steady-state conditions, and the pulse-picking device selectively gates these pulses to the workpiece based on beam position, ensuring the laser remains in its optimal steady-state operating regime throughout the process
3Device complexity
If the beam-positioning system is the master controlling laser firing timing, then the system architecture is simple with direct trigger signal generation, but the laser parameters become variable and control of laser parameters applied to the work surface is reduced
Solution Approach 1:
The patent inverts the control architecture so that the laser system becomes the master controlling its own pulse timing at a constant repetition rate, while the beam-positioning system becomes the slave that receives commands to direct pulses to specific locations. This inversion maintains simplicity in the laser control while dramatically improving laser parameter consistency and controllability
Data Source
AI summary
A laser machining system (20) employs a fast positioner (68), such as a pair of galvanometer mirrors (70), that directs a beam axis (24) at a specified velocity to a start position of a cutting path (92) in coincidence with one of multiple laser pulses emitted from a laser (28) a constant laser pulse repetition rate, which runs independently of the relative position of the beam axis (24) with respect to the workpiece (26).