Video rate mid-infrared photothermal microscopy system using synchronized laser scanning
Inventors
Cheng, Ji-Xin • Lan, Lu • Yin, Jiaze
Assignees
Publication Number
US-12298238-B2
Publication Date
2025-05-13
Expiration Date
2043-08-15
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Abstract
A mid-infrared photothermal microscopy system images a sample. A mid-infrared optical source generates a mid-infrared beam which is directed along a first optical path to reach the substrate on a first side and heat the sample. A probe light source generates a probe light which is directed along a second optical path to reach the substrate on a second side and illuminate the sample. A first laser scanner is positioned along the first optical path and configured to rotate to redirect light and scan the sample with the mid-infrared beam. A second laser scanner is positioned along the second optical path and configured to rotate to redirect light and scan the sample with the probe light. The laser scanners each include at least one mirror driven to rotate such that the mid-infrared beam and the probe light scan the sample synchronously.
Core Innovation
The invention provides a mid-infrared photothermal microscopy (MIP) system capable of video-rate imaging. The system utilizes a mid-infrared optical source that generates a mid-infrared beam directed along a first optical path to reach and heat a sample, while a probe light source generates probe light along a second, counter-propagating optical path to illuminate the sample. Importantly, the system employs two laser scanners—each comprising at least one movable mirror—to synchronously scan both the mid-infrared beam and the probe light across the sample, ensuring overlapping and uniform excitation and probing during imaging.
The background highlights the challenges of existing mid-infrared and photothermal microscopy techniques, which face limitations in spatial resolution, susceptibility to water background noise, and slow imaging speed—often restricted to milliseconds or minutes per frame. These limitations prevent effective imaging of fast dynamics or high-throughput characterization in living systems. There is a need for an MIP system that significantly increases imaging speed without sacrificing sensitivity or spatial resolution.
This disclosure introduces several innovations to overcome those problems. First, it replaces conventional lock-in amplifier–based demodulation with a high-speed digitization and wideband amplifier scheme to resolve photothermal signals at nanosecond-level system response. Second, the dual synchronized galvo-based laser scanning enables microsecond-scale pixel acquisition, achieving line rates over 2.5 kHz and uniform large field-of-view scanning. Together, these features result in single-pulse, video-rate chemical imaging of dynamic processes in living biological samples, with three orders of magnitude higher speed compared to prior art.
Claims Coverage
There are two independent claims outlining three main inventive features for the system and method.
Synchronized dual-path laser scanning for mid-infrared photothermal microscopy
A mid-infrared photothermal microscopy system comprising: - A mid-infrared optical source to generate a mid-infrared beam along a first optical path to heat the sample. - A probe light source to generate probe light along a second, counter-propagating, and overlapping optical path. - First and second laser scanners (each comprising at least one movable mirror) positioned along the respective optical paths and configured to rotate for scanning. - A reflective objective lens on the first path and a second objective lens on the second path. - The laser scanners are driven to rotate such that both beams scan the sample synchronously, achieving overlap and alignment during scanning.
Method for synchronized dual-beam scanning and rapid photothermal imaging
A method of operating a photothermal infrared microscope to image a sample, comprising: 1. Illuminating the sample with a mid-infrared beam along a first optical path to heat the sample. 2. Simultaneously illuminating the sample with a probe light beam along a counter-propagating, overlapping second optical path. 3. Providing first and second laser scanners with at least one movable mirror each to scan the respective beams. 4. Arranging reflective and second objective lenses along the respective paths. 5. Driving the laser scanners so that both beams scan the sample synchronously for overlapped illumination and excitation.
Single pulse photothermal detection and wide field high-throughput imaging
The system and method enable: - Single-pulse photothermal detection through synchronized scanning and high-speed digitization. - Imaging a field of at least 10–200 micrometers on a side in 0.1 seconds or less. - Measuring dynamic changes within biological cells and producing images with signal-to-noise ratio greater than 50 without requiring sample movement or stitching.
The independent claims cover the architecture and operation of a synchronized dual-laser scanning MIP system, the method for dual-beam scanning with high-speed demodulation, and its capabilities for video-rate, high-sensitivity, and large-field photothermal imaging.
Stated Advantages
Enables high-sensitivity and high-speed imaging at video-rate, allowing microsecond-scale acquisition of photothermal signals.
Increases imaging speed by three orders of magnitude compared to prior sample-scanning MIP microscopes, from millisecond to microsecond per pixel.
Allows uniform illumination of large fields of view (over 200–400 μm) for high-throughput chemical imaging.
Bypasses the water background issue in IR imaging, enabling label-free imaging of living biological samples.
Supports volumetric (3D) imaging with strong sectioning capability and submicron spatial resolution.
Enhances chemical specificity through high-speed hyperspectral and spectroscopic imaging.
Documented Applications
Video-rate chemical imaging and analysis of living cells, including real-time observation of lipid dynamics in fungal cells.
Hyperspectral imaging to dissect layered ultrastructure of fungal cell walls and resolve chemical composition.
Mapping fat storage in free-moving C. elegans and live embryos with high spatial resolution.
Measurement of cellular dynamics and tracking of fast biomolecular processes in living organisms at multiple scales.
Spectroscopic decomposition of biological cell walls, revealing ultrastructures like outer wall, inner wall, and membrane.
Interested in licensing this patent?