Acousto-Optical Deflector Pairing for High-Speed Laser Scanning
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Solution Overview
Problem
Existing laser scanning systems, particularly those using acousto-optic deflectors, face limitations in scanning speed and efficiency due to fixed scanning speeds and alignment requirements, which hinder high-resolution imaging of biological phenomena like synaptic transmission.
Innovation Solution
A laser scanning system comprising two acousto-optical deflectors with frequency variations applied in specific laws of command, along with a compensating unit to address defocusing effects, allowing for tunable scanning speeds and improved scanning precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a single acousto-optic deflector is used for scanning, then the scanning speed can be increased, but the lensing effect degrades beam quality and scanning precision
Solution Approach 1:
The patent combines two acousto-optic deflectors in a push-pull configuration where they operate simultaneously in opposite directions. The first AOD deflects the beam in one direction while the second AOD deflects it in the opposite direction, merging their effects to cancel lensing while maintaining high scanning speed.
Solution Approach 2:
The patent uses the second acousto-optic deflector as a counterweight to the first AOD's lensing effect. By applying opposite frequency chirps to the two AODs, the diverging effect of one is compensated by the converging effect of the other, effectively canceling the net lensing effect on the beam.
2Manufacturing precision
If two acousto-optic deflectors are used in opposite directions to cancel lensing, then beam quality is maintained, but optical alignment becomes complex and power loss increases
Solution Approach 1:
The patent introduces a slight asymmetry in the optical path lengths of the two AODs, with the first AOD positioned slightly closer to the sample than the second AOD. This asymmetric configuration simplifies the optical alignment requirements while maintaining the push-pull lensing cancellation effect.
3Manufacturing precision
If acoustic frequency is changed in elementary steps for scanning, then the deflection angle changes, but the switching time is too long for high-resolution imaging
Solution Approach 1:
The patent applies periodic frequency chirps to the acousto-optic deflectors, where the frequency is continuously modulated in a periodic manner to achieve both precise angular control and fast switching. This periodic frequency modulation allows the system to maintain deflection precision while reducing switching time to the microsecond 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
Enables fast, precise, and repeatable scanning with speeds exceeding those of classical mechanical devices, achieving scanning speeds up to 500 radians per second and facilitating high-resolution imaging.
Implementation Method 1
based on the interaction between an acoustic compression wave propagating in an acousto-optical crystal and an electromagnetic wave. The resulting diffractive process deflects a fraction of the electromagnetic wave at an angle proportional to the acoustic frequency of the acoustic compression wave
Implementation Method 2
The resulting diffractive process deflects a fraction of the electromagnetic wave at an angle proportional to the acoustic frequency
Data Source
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Figure 5~6
AI summary
The present invention concerns a laser scanning system (18) comprising: - a first acousto-optical deflector (30) deflecting a beam in a first direction (X) to obtain a first deflected beam and comprising a first acousto-optical crystal on which is applied an acoustic wave whose frequency varies over time according to a first law of command, and - a second acousto-optical deflector (32) deflecting the first deflected beam in a second direction (Y), defining an angle comprised between 85° and 95° with the first direction, and comprising a second acousto-optical crystal on which is applied an acoustic wave whose frequency varies over time according to a second law of command, characterized in that the first law of command and the second law of command are chosen so that the average speed of the laser scanning system (18) is superior to 10 radians per second.