Temporal Focusing Microscopy for Fast Multi-Depth Tissue Imaging
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Solution Overview
Problem
Current two-photon scanning microscopy technologies face limitations in achieving high spatio-temporal resolution for large cortical volumes due to mechanical and optical constraints, resulting in low temporal resolution and limited effective volumetric field-of-view, which hampers the understanding of neural network activities in mammalian brains.
Innovation Solution
A tissue imaging system utilizing Multiplexed Scanned Temporal Focusing (MuST) with a laser module, optical delay module, and spatial multiplexing module to split and delay laser pulses, allowing for high-speed imaging with temporally and spatially multiplexed laser pulses, enabling simultaneous excitation of multiple depths or planes within the target volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If diffraction limited two-photon scanning microscopy is used, then optical resolution and signal to noise ratio are improved, but temporal resolution deteriorates due to mechanical scanning constraints
Solution Approach 1:
The laser pulse is segmented into multiple time-delayed sub-pulses, each focused at different depths within the tissue. This allows simultaneous excitation of multiple focal planes along the axial direction, effectively multiplying the imaging speed without compromising optical resolution at each focal point.
Solution Approach 2:
The invention transitions from scanning in the lateral plane to scanning along the axial direction by using temporal focusing. Multiple sub-pulses are focused at different depths (z-positions), enabling volumetric imaging by exploiting the axial dimension rather than being constrained by lateral scanning speed.
2Speed
If scanning speed is increased to improve temporal resolution, then frame rate is improved, but signal to noise ratio deteriorates due to reduced illumination time
Solution Approach 1:
Multiple sub-pulses are combined in time to excite different focal planes simultaneously. By coherently combining the signal from multiple focal points along the axial direction, the total signal is enhanced while maintaining high temporal resolution, as all excitations occur within a single laser pulse envelope.
Solution Approach 2:
The laser pulse is structured to provide continuous useful action across multiple depths through temporal multiplexing. Instead of sequentially scanning through z-planes, the system illuminates multiple depths simultaneously with time-delayed sub-pulses, maintaining continuous excitation across the volumetric field of view.
3Volume of stationary object
If conventional two-photon scanning is used to image large cortical volumes, then volumetric field-of-view is improved, but temporal resolution deteriorates due to mechanical scanning constraints
Solution Approach 1:
The laser beam is spatially segmented into multiple sub-beams using a microlens array, with each sub-beam focused at a different lateral position. This allows parallel excitation of multiple regions within the volumetric field of view, effectively multiplying the imaging speed while maintaining coverage of large cortical volumes.
Solution Approach 2:
The invention combines axial temporal focusing with lateral spatial multiplexing. By segmenting the beam laterally and delaying pulses temporally for different depths, the system achieves volumetric imaging at high speed by exploiting both axial and lateral dimensions simultaneously.
4Measurement precision
If mechanical scanning is used to achieve diffraction limited resolution, then optical sectioning is improved, but imaging speed deteriorates due to physical constraints of moving parts
Solution Approach 1:
The invention replaces mechanical scanning with optical temporal focusing. Instead of physically moving the focal point through space using galvanometric mirrors or piezoelectric actuators, the system uses optical path length differences to focus pulses at different depths, eliminating mechanical constraints and enabling faster imaging.
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
The system achieves high-speed, high-resolution imaging of tens of thousands of neurons with single-cell resolution across large cortical volumes, significantly improving the understanding of neural network dynamics and information processing in mammalian brains.
Implementation Method 1
The optical delay module is configured to split a laser pulse received from the laser module into a plurality of time-delayed sub-pulses
Implementation Method 2
The sub-pulses include a first sub-pulse and a second sub-pulse, wherein the second sub-pulse is delayed with respect to the first sub-pulse by more than 3 ns. The first sub-pulse may be focused at a first depth within the target volume and the second sub-pulse may be focused at a second depth within the target volume
Implementation Method 3
a photodetector configured to collect photons generated within the target volume in response to excitation of the target volume by the first and second sub-pulses
Implementation Method 4
The optical delay module preferably includes a beam-splitter configured to split the laser pulse into the plurality of sub-pulses
Data Source
AI summary
A tissue imaging system includes a laser module for outputting a laser pulse, an optical delay module configured to split a laser pulse received from the laser module into a plurality of time-delayed sub-pulses, a telescope for delivering the sub-pulses from the optical delay module to a target volume and a photodetector configured to collect photons generated within the target volume in response to excitation of the target volume by the first and second sub-pulses. The system may further include a spatial multiplexing module configured to receive the temporally multiplexed laser pulse from the optical delay module and splitting the temporally multiplexed laser pulse into a plurality of sub-beams including a first sub-beam and a second sub-beam, wherein the first sub-beam and the second sub-beam are spatially separated with respect to a first image plane formed at a first depth within the target volume and with respect to a second image plane formed at a second depth within the target volume.