Fluorescence Lifetime Imaging with Gaussian Beam Shaping
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Solution Overview
Problem
Confocal fluorescence microscopy faces challenges in maintaining optical resolution and signal strength while minimizing photobleaching and phototoxicity, particularly in samples with weak fluorescence signals, and existing beam shaping techniques are bulky, costly, or inefficient.
Innovation Solution
A spatial beam attenuator and pinhole beam splitter are used to convert non-Gaussian laser beams into Gaussian profiles and enable dual imaging modes, allowing simultaneous collection of photons through and around the pinhole, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If traditional beam shaping techniques (single-mode fibers, prism pairs, beam expanders) are used to convert non-Gaussian laser beams into Gaussian profiles, then beam quality is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts only the essential function of beam shaping from complex optical systems. By using a simple amplitude mask with transmission function T(x,y) that directly impinges on the non-Gaussian beam, the invention achieves Gaussian beam conversion without requiring single-mode fibers, prism pairs, or beam expanders. This extraction of the core beam shaping function resolves the contradiction between beam quality improvement and device complexity reduction.
Solution Approach 2:
The patent introduces an amplitude mask as an intermediary element between the non-Gaussian laser beam and the sample. This mask, with specifically designed transmission function, acts as a mediator that transforms the beam profile without requiring complex optical components. The intermediary mask simplifies the optical path while achieving the desired Gaussian beam shape, thereby reducing device complexity.
2Measurement precision
If confocal pinhole is used to maintain optical resolution, then imaging resolution is improved, but signal strength decreases due to photon rejection
Solution Approach 1:
The patent implements a dual-mode detection system where the confocal pinhole configuration can be dynamically switched with a non-confocal mode. In confocal mode, the pinhole maintains optical resolution by rejecting out-of-focus photons. In non-confocal mode, the pinhole is bypassed to collect maximum photons from the sample. This dynamic switching capability resolves the contradiction between maintaining optical resolution and preserving signal strength.
Solution Approach 2:
The patent applies partial confocal filtering by allowing some out-of-focus light to pass through while still maintaining resolution. The amplitude mask in the beam path pre-conditioned the illumination, which reduces the severity of pinhole filtering needed. This partial application of confocal principles maintains adequate resolution while preserving more signal compared to traditional confocal microscopy.
3Quantity of substance
If high excitation intensity is used to improve signal strength, then fluorescence signal is improved, but photobleaching and phototoxicity increase
Solution Approach 1:
The patent changes the spatial distribution parameter of excitation intensity by using an amplitude mask to create a Gaussian beam profile. This optimized spatial distribution ensures that excitation energy is concentrated where needed while reducing overall energy consumption. The Gaussian profile matches the confocal pinhole acceptance pattern, maximizing signal collection efficiency and allowing lower excitation intensities to achieve the same effective signal, thereby reducing photobleaching and phototoxicity.
Solution Approach 2:
The patent replaces the mechanical/physical approach of increasing laser power with an optical design approach using amplitude masks and dual-mode detection. Instead of brute-force increasing excitation intensity, the system uses optimized optical paths and detection modes to maximize signal efficiency. This substitution allows achieving high fluorescence signals through efficient light collection rather than high excitation power, thereby reducing harmful photobleaching and phototoxicity effects.
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
Enhances imaging performance by maintaining optical resolution and signal strength, reducing complexity and cost, and minimizing photobleaching, especially in samples with weak fluorescence.
Implementation Method 1
A spatial beam attenuator and pinhole beam splitter are used to convert non-Gaussian laser beams into Gaussian profiles
Implementation Method 2
enable dual imaging modes, allowing simultaneous collection of photons through and around the pinhole
Implementation Method 3
Fluorophores are molecules that can absorb light at one wavelength and emit light at a longer wavelength
Data Source
AI summary
This invention presents a frequency-domain fluorescence lifetime imaging system, enhancing capabilities with a spatial beam attenuator and pinhole beam splitter. The spatial beam attenuator reshapes any beam into a circular Gaussian beam profile, being compact, cost-effective, with low loss and back reflection. Using digital printing technology, a thin optical film is deposited onto an optical substrate for precise local attenuation of the beam in either transmission or reflection mode. The pinhole beam splitter consists of an optical beam splitter with an active region the size of a pinhole, positioned near the beam's focus, which directs focused light into two paths based on acceptance or rejection by the pinhole. This configuration allows for two detectors to collect photons from both paths concurrently, facilitating dual-mode imaging. Consequently, the system can generate both confocal and conventional non-confocal laser scanning fluorescence lifetime images of the sample at the same time.