Acousto-Optic Modulator Pulse Energy Control
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Solution Overview
Problem
Conventional methods for controlling laser power or pulse energy in laser processing are slow, prone to variations, and lack coordination with other operations, affecting the efficiency and quality of feature formation in materials like printed circuit boards.
Innovation Solution
A laser processing apparatus with a pulse energy control system that adjusts pulse energy on a pulse-by-pulse basis using an open loop feedforward control path and a laser energy monitor for feedback, enabling rapid changes in pulse energy and repetition frequency, coordinated with beam position control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional attenuation optics or direct control of laser optical output power are used, then laser power or pulse energy can be controlled, but the control speed is slow and coordination with other operations is lacking
Solution Approach 1:
The patent replaces mechanical attenuation optics with an acousto-optic modulator (AOM) that uses acoustic waves to diffract and control laser pulses. This substitution enables electronic control of pulse energy with microsecond response times, dramatically increasing control speed and allowing precise coordination with beam positioning and other processing operations on a pulse-by-pulse basis.
2Ease of operation
If mechanically-adjusted polarization optics are used, then laser power can be controlled, but the adjustment speed is slow
Solution Approach 1:
The patent replaces mechanically-adjusted polarization optics with an acousto-optic modulator driven by electronic signals. The AOM uses radio frequency acoustic waves to create periodic refractive index changes in the crystal, enabling rapid modulation of laser pulse energy without mechanical movement. This achieves ease of operation through electronic control while increasing adjustment speed to microsecond timescales.
3Adaptability or versatility
If conventional methods of controlling laser power are used, then pulse energy can be adjusted, but variation in laser delivery occurs
Solution Approach 1:
The patent implements a feedback control system using a photodiode detector to monitor the actual energy of each laser pulse. The measured pulse energy is compared with the desired setpoint, and the error signal is used to adjust the AOM drive signal in real-time. This closed-loop feedback compensates for variations in laser output and AOM transmission, maintaining consistent pulse energy delivery across the full adjustment range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise control of laser pulse energy and repetition frequency, improving the speed and accuracy of feature formation in laser processing, reducing errors and enhancing the quality of processed materials.
Implementation Method 1
An acousto-optic modulator (AOM) is provided in the beam path between the laser and the workpiece. The AOM is configured to receive a drive signal having a frequency corresponding to a resonance frequency of the AOM.
Data Source
AI summary
Systems and methods provide laser pulse energy control and/or monitoring. An example laser processing apparatus includes a laser system to generate a beam of laser pulses and a pulse energy control system to adjust the pulse energy of each laser pulse in the beam on a pulse-by-pulse basis. The pulse energy control system includes an open loop feedforward control path that selects a pulse energy transmission value for each laser pulse based on a calibrated transmission curve that maps laser pulse energy as a function of pulse repetition frequency. A laser energy monitor measures the laser pulse energy of each laser pulse in the beam of laser pulses. A power control loop may further adjust the pulse energy of one or more laser pulses in the beam of laser pulses based on feedback from the laser energy monitor.