Wide-Field Photothermal IR Imaging With Interferometric Probe Detection
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Solution Overview
Problem
Conventional infrared spectroscopy techniques face limitations in spatial resolution, require sample preparation, and suffer from artifacts that complicate material identification and quantification, particularly in opaque or biological substances.
Innovation Solution
A system utilizing a non-diffractive beam splitter and a 4f optical relay system for infrared analysis, which includes a probe beam to create an interferogram on an array detector, allowing for high-throughput, wide-field photothermal infrared absorption measurements without sample deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional FTIR microscopy is used to achieve spatially resolved measurements, then spectral information can be obtained, but spatial resolution is limited to the wavelength of IR light (on the order of 10 microns)
Solution Approach 1:
The patent uses a visible or near-IR probe beam as an intermediary to detect the photothermal changes caused by mid-IR absorption. The probe beam at a different wavelength (visible/near-IR) acts as a mediator that can achieve higher spatial resolution while the photothermal effect links it to the mid-IR absorption spectrum, thus resolving the contradiction between spatial resolution and spectral information quality
Solution Approach 2:
The patent changes the detection parameter from direct mid-IR detection to detection of photothermal changes (temperature-induced refractive index changes) using a probe beam. By modulating the mid-IR beam and detecting the resulting photothermal phase changes in the probe beam, the system achieves both high spatial resolution and accurate spectral information
2Measurement precision
If FTIR spectroscopy is used for opaque or biological substances, then spectral analysis can be performed, but significant sample preparation is required
Solution Approach 1:
The probe beam serves as an intermediary detection mechanism that does not require the sample to be transparent to the detection wavelength. Since the probe beam detects photothermal changes rather than direct transmission, opaque and biological samples can be analyzed without extensive preparation, while still obtaining accurate spectral information through the photothermal linkage to mid-IR absorption
3Measurement precision
If ATR spectroscopy is used to achieve higher spatial resolution, then resolution improves, but direct contact with the sample causes deformation and breaking
Solution Approach 1:
The probe beam acts as a non-contact intermediary for detection. Instead of requiring physical contact between the sample and the detection system (as in ATR), the probe beam detects photothermal changes remotely, achieving high spatial resolution through optical focusing while completely avoiding mechanical contact that would cause sample deformation or breaking
4Measurement precision
If conventional photothermal spectroscopy is used to achieve sub-micron resolution, then spatial resolution improves, but optical throughput efficiency is low
Solution Approach 1:
The patent uses a 4f optical relay system with spatial filtering to transform the detection approach. By relaying the probe beam through a 4f system and spatially filtering at the Fourier plane, the system maintains high optical throughput efficiency while achieving sub-micron spatial resolution through proper beam conditioning and focus control
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 rapid, artifact-free, and high-resolution infrared spectroscopy across a wide field area, enhancing signal-to-noise ratio and eliminating the need for burdensome sample preparation.
Implementation Method 1
illuminating a sample with a first beam of IR light having a wavelength of at least 2.5 microns to create a photothermal change in a region within the sample due to absorption of energy from the first beam
Implementation Method 2
illuminating at least a portion of the region within the sample with a second beam of light having a wavelength of less than 2.5 microns to detect the photothermal change in the region at a resolution smaller than a diffraction limit of the first beam
Data Source
AI summary
A system for infrared analysis over a wide field area of a sample is disclosed herein that relies on interference of non-diffractively separated beams of light containing image data corresponding to the sample, as well as a photothermal effect on the sample.