Acousto-Optic Modulator Laser Power Control
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Solution Overview
Problem
High-power laser systems used in defect inspection tools face challenges in efficiently controlling laser power due to settling time issues with pump diode current changes and reliability concerns with motorized rotary mounts, which impact system operation and reliability.
Innovation Solution
A laser-beam power-modulation system utilizing an acousto-optic modulator (AOM) to separate the laser beam into a primary beam and diffracted beams based on an input signal, with a controller generating feedback-based control signals to adjust the power of the primary beam, eliminating the need for moving parts and pump diode modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If pump diode current is changed to adjust input-stage power, then laser power control is achieved, but settling time increases and negatively impacts system operation
Solution Approach 1:
The patent replaces the mechanical/electrical system of pump diode current modulation with an acousto-optic modulator (AOM) that uses acoustic waves to diffract and modulate the laser beam. The AOM uses sound waves (acoustic field) to create a diffraction grating in the optical path, allowing rapid power modulation without the settling time issues of pump diode current changes. This substitutes an acoustic-optical system for an electrical-pump system.
2Power
If a motorized rotary mount with half-wave plate is used to attenuate power, then input-stage power is changed, but reliability decreases due to moving parts
Solution Approach 1:
The patent eliminates the motorized rotary mount and half-wave plate mechanical system by using an acousto-optic modulator. The AOM has no moving parts - it uses acoustic waves to create a controllable diffraction grating that can rapidly modulate beam power. This acoustic-optical system replaces the mechanical rotation system, dramatically improving reliability while maintaining power attenuation capability.
Solution Approach 2:
The patent transitions from a static mechanical system (fixed half-wave plate requiring motorized rotation) to a dynamic acoustic-optical system. The AOM can rapidly change its diffraction properties by modulating the acoustic wave frequency and amplitude, enabling fast, reliable power control without mechanical movement. The system becomes dynamically adjustable through acoustic field control rather than mechanical repositioning.
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 solution enables precise and reliable control of laser power without moving parts, maintaining power stability with minimal noise and increased system reliability, effectively addressing the limitations of existing high-power laser systems.
Implementation Method 1
an acousto-optic modulator (AOM) to receive a laser beam and separate the laser beam into a primary beam and a plurality of diffracted beams based on an input signal
Data Source
AI summary
A laser-beam power-modulation system includes an acousto-optic modulator (AOM) to receive a laser beam and separate the laser beam into a primary beam and a plurality of diffracted beams based on an input signal. The power of the primary beam depends on the input signal. The system also includes a slit to transmit the primary beam and dump the plurality of diffracted beams, a controller to generate a control signal based at least in part on feedback indicative of the power of the primary beam or the power of a beam generated using the primary beam, and a driver to generate the input signal based at least in part on the control signal.