Spatial Light Modulator Laser Targeting for Millisecond Cell Stimulation
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Solution Overview
Problem
Current high-speed optical systems are limited in their ability to target large populations of cells with millisecond time resolution, restricting their application in neuroscience research and other domains like laser ranging for autonomous vehicles.
Innovation Solution
The development of a high-speed optical targeting system using a spatial light modulator and a femtosecond pulsed laser source, enabling sequential scanning through 10^3 point-wise targets at microsecond intervals and providing independent two-photon excitation of multiple locations at high revisit rates, combined with galvo scanning and phase synchronization to achieve millisecond time resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional scanning systems are used to densely cover an area, then high resolution sampling is achieved, but the refresh rate is reduced
Solution Approach 1:
The patent segments the scanning process into two independent dimensions: fast horizontal scanning (galvo mirror) and slow vertical scanning (SLM row addressing). This segmentation allows the system to achieve high spatial resolution by systematically addressing each row while maintaining high refresh rates through the fast horizontal scan, resolving the contradiction between dense sampling and fast refresh.
Solution Approach 2:
The patent introduces a temporal dimension by using pulsed laser excitation synchronized with the scanning process. By delivering excitation pulses only at specific moments during the scan (when the beam is at the correct horizontal position), the system achieves high spatial resolution without requiring continuous scanning, thereby maintaining high refresh rates.
2Area of stationary object
If conventional two-photon microscopes are used to target multiple neurons, then dense area coverage is achieved, but the number of targetable neurons is limited to less than 100
Solution Approach 1:
The patent makes the SLM universally applicable to all rows simultaneously. By programming the SLM to diffract light to different vertical positions for each row, the system can target any neuron in the field of view regardless of its position, enabling dense area coverage with high neuron targeting capacity beyond the limit of conventional microscopes.
Solution Approach 2:
The SLM acts as an intermediary between the laser beam and the sample, enabling precise control of light direction and focus. This intermediary device allows the system to target multiple neurons at once by diffracting light to different vertical positions, overcoming the limitation of conventional microscopes that can only target a limited number of neurons even with dense area coverage.
3Loss of time
If fast scanning is implemented to achieve millisecond time resolution, then temporal precision is improved, but the system cannot target large populations of cells
Solution Approach 1:
The patent uses periodic pulsed laser excitation synchronized with the scanning process. By delivering excitation pulses at regular intervals (at the laser repetition rate) and coordinating these pulses with the scanning timing, the system achieves millisecond time resolution while being able to target large populations of cells through the SLM's multi-position capability.
Solution Approach 2:
The patent maintains continuous useful action by ensuring that every laser pulse contributes to imaging or stimulation. The SLM is continuously updated with the appropriate phase patterns to direct light to the correct vertical positions, and the galvo mirror continuously scans horizontally, creating a continuous flow of useful excitation events that can target large numbers of cells with millisecond precision.
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 a 10-fold improvement in scanning speed, enabling large-scale optically targeted electrical recording and stimulation at millisecond timescales, effectively overcoming the limitations of conventional systems.
Implementation Method 1
configuring a spatial light modulator to direct either even or odd rows to diffract a pulsed laser beam
Implementation Method 2
scanning the beam of light across the spatial light modulator
Implementation Method 3
placing a pick-off mirror in an optical path of a laser scanning system to reflect a fraction of light from a laser onto a photodiode
Implementation Method 4
synchronizing timing of pulses of light from the laser with galvo scanning of the light from the laser across the face of a spatial light modulator
Implementation Method 5
providing independent two-photon excitation of multiple locations at high revisit rates
Implementation Method 6
Imaging of neural activity using fluorescence microscopy
Data Source
AI summary
High-speed optical targeting systems and methods are described, wherein a light source, e.g., a laser, is optically coupled with a spatial light modulator. Some embodiments include a device for two-dimensional light steering. In some embodiments, the device comprises a spatial light modulator, and a laser in optical communication with the spatial light modulator. In some exemplary methods, an area is scanned withing a microscope with millisecond revisit time, such as with at least 500 individually targeted points of light. In other exemplary methods, a beam of light is directed from a laser light source into an optical system, through which the light may be focused into a line on a spatial light modulator, wherein the light can be scanned across the spatial light modulator, and directed from the spatial light modulator onto a sample. Other exemplary methods are drawn to the construction and use of the embodiments escribed herein.