Optical System for 3D Spatiotemporal Wavefront Shaping
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Solution Overview
Problem
Current two-photon microscopy techniques face challenges in generating shaped illumination targets across three-dimensional volumes with micrometer lateral and axial precision, particularly in applications like 3D lithography and imaging, due to limitations in axial displacement and the presence of intensity speckles from computer-generated holography (CGH) and group velocity dispersion.
Innovation Solution
An optical system comprising a beam shaper for initial spatial modulation, a diffraction grating for temporal focusing, and a reconfigurable spatial light modulator (SLM) to replicate and position illumination patterns in three dimensions, allowing for independent control of lateral and axial coordinates and overcoming previous limitations by enabling a theoretically unlimited number of extended illumination targets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If computer-generated holography (CGH) is used to generate shaped illumination patterns, then lateral precision and robustness to scattering are improved, but intensity speckles are introduced and axial displacement capability is limited
Solution Approach 1:
The patent extracts and removes the harmful speckle effect by using a different illumination generation approach. Instead of using CGH which inherently produces speckles, the system uses a spatial light modulator with a lens to directly generate speckle-free illumination patterns, thereby taking out the harmful factor while preserving the lateral precision benefit
Solution Approach 2:
The patent creates multiple copies of the illumination pattern at different axial positions using the spatial light modulator. By programming the SLM with appropriate phase patterns, the system can replicate the same lateral illumination pattern at multiple depth positions, enabling axial displacement without the limitations of CGH-based approaches
2Speed
If dual-prism grating is used for temporal focusing and axial displacement, then axial shifts of focus plane are enabled, but displacement velocity is limited and only single plane shifting is achieved
Solution Approach 1:
The patent introduces dynamic control of axial displacement by using a spatial light modulator that can be rapidly reprogrammed. Unlike the static dual-prism grating approach, the SLM can dynamically change the axial position of the focus plane at high speeds, enabling fast axial scanning and high displacement velocity while maintaining temporal focusing
Solution Approach 2:
The patent extends the system from single-plane axial displacement to multi-plane 3D illumination by combining the spatial light modulator with temporal focusing. The SLM can independently control illumination at multiple axial positions simultaneously, adding the dimension of multiple addressable planes while maintaining high axial resolution through temporal focusing
3Adaptability or versatility
If two spatial light modulators are used for independent lateral and axial control, then multiple planes can be addressed, but the number of planes is limited to about 6 due to tiling requirements
Solution Approach 1:
The patent makes a single spatial light modulator perform multiple functions that previously required two SLMs. By using phase modulation and temporal focusing together, one SLM can independently control both lateral positioning and axial displacement of illumination patterns, eliminating the need for SLM tiling and enabling a much larger number of addressable planes without increasing device complexity
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 system achieves precise, decoupled axial and lateral control of illumination patterns, significantly increasing the number of addressable planes and enabling the creation of complex 3D patterns with superior axial resolution, enhancing applications such as 3D photopolymerization, imaging, and optogenetics.
Implementation Method 1
a beam shaper (1), for instance a spatial light modulator (SLM), configured to give one illumination pattern (P)
Implementation Method 2
a dispersive grating placed at a plane conjugated with the sample plane, diffracts the different spectral frequencies comprising the ultra-short excitation pulse toward different directions
Implementation Method 3
temporal focusing (TF) was proposed as an elegant scan-less solution to simultaneously illuminate large areas with micrometer axial confinement
Implementation Method 4
a reconfigurable spatial light modulator (SLM) to replicate and position illumination patterns in three dimensions
Data Source
AI summary
The present invention concerns an optical system for spatiotemporally shaping the wavefront of the electric field of a light beam (1) to be projected into a target volume (5), where the propagation axis is axis z, to create 3D patterned illumination in the target volume (5), comprising a pulsed laser source, configured to have an illumination pattern whose transversal surface at the target volume being superior to the diffraction limit of the optical system, at least one intermediate optical element (4) which is a dispersive grating for performing temporal focusing of the light beam (1), located, on the propagation axis (z), where an image of the illumination pattern is formed, for modulating the phase and/or the amplitude of the electric field of the light beam, and a second optical element (3) which is a spatiallight modulator for modulating the phase of the electric field of the input light beam, and for realizing spatiotemporal multiplexing to create 3D patterned illumination in the target volume (5) by replicating the illumination pattern, so as to have several replicated illumination patterns in the target volume (5), and controlling the position with transversal coordinates X, Y and axial coordinate Z of each replicated illumination pattern in the target volume (5).