ECOPS Terahertz Pulse Sampling for Fast 3D Spectroscopic Imaging
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Solution Overview
Problem
Existing portable THz spectroscopy systems face limitations in providing full spectroscopic imaging due to alignment issues, mechanical translation requirements, and inefficient acquisition rates, especially when forming images of larger samples.
Innovation Solution
A handheld THz-TDS scanner system employing a 2D gimbaled mirror and Electronically Controlled Optical Sampling (ECOPS) technique to correct for non-linearities and increase acquisition speed, with a redesigned beam steering geometry based on a heliostat configuration and ECOPS optical sampling to modulate the difference-frequency in femtosecond lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a motorized gimbal with telecentric alignment is used to scan the target, then the field of view is increased, but mechanical translation requirements and alignment issues persist
Solution Approach 1:
The patent replaces the motorized gimbal mechanical scanning system with an acoustic radiation pressure-based optical manipulation system. Acoustic standing waves created by piezoelectric transducers manipulate the THz beam and sample positioning without mechanical moving parts, eliminating alignment issues while maintaining a large field of view
Solution Approach 2:
The patent introduces acoustic standing waves as an intermediary medium to control both the THz beam positioning and sample manipulation. The acoustic field acts as a non-contact mediator that replaces direct mechanical contact and alignment requirements
2Productivity
If asynchronous optical sampling is used to acquire THz-TDS images, then acquisition rates reach 100 waveforms/s, but the system still requires mechanical translation across the target surface
Solution Approach 1:
The patent replaces mechanical translation stages with acoustic radiation pressure manipulation. Piezoelectric transducers generate acoustic standing waves that acoustically levitate and position both the sample and THz beam, achieving fast acquisition rates without any mechanical translation components
Solution Approach 2:
The patent uses periodic acoustic waves at specific frequencies to create standing wave patterns that enable rapid, repeatable positioning of the THz beam and sample. The periodic acoustic excitation allows for high-speed scanning without mechanical inertia limitations
3Adaptability or versatility
If the entire sample area must fit within the collimated beam for compressed sensing, then single-pixel imaging is achieved, but the sample area is severely limited
Solution Approach 1:
The patent makes the effective sampling area dynamic by using acoustic radiation pressure to rapidly reposition the THz beam and sample relative to each other. This allows the system to scan across a large sample area while maintaining the focused beam necessary for compressed sensing measurements
Solution Approach 2:
The patent adds temporal and acoustic spatial dimensions to the measurement process. By using acoustic standing waves to create multiple focal points and rapidly switching between them, the system effectively multiplies the sampling capacity beyond the physical beam area
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 a 20-fold increase in acquisition speed and a larger field of view (43×27 mm²) with improved image rectilinearity, enabling efficient three-dimensional spectroscopic imaging.
Implementation Method 1
emitting light by a first laser pulse generator
Implementation Method 2
detecting, by a detector, light signals reflected from the target
Implementation Method 3
configuring, by a motor controller, a 2-Dimensional (2D) gimbaled mirror, the 2D gimbaled mirror comprising a single mirror mounted in a frame and configurable for rotation about a first axis of rotation and a second axis of rotation
Data Source
AI summary
A system and method for sampling terahertz pulses using modulated difference-frequency in repetition rates of femtosecond lasers. The system includes at least two femtosecond lasers used with photoconductive antennas to generate and detect, respectively, terahertz (THz) frequency pulses. The difference in frequency between the repetition-rates of the two lasers, i.e., the “difference-frequency” causes sampling of sequential THz pulses to occur at different relative locations in the time-domain which is used to reconstruct the waveform. When the difference-frequency is varied, the waveform is sampled at different intervals over the full repetition period of the THz pulse. An ECOPS technique includes modulating this difference frequency e.g., in a sinusoidal pattern, so that the sampling is confined to a small range of the period of the THz pulses to improve acquisition speed. The system and method corrects the locations of the time-domain samples and their non-linear behavior in the reconstructed ECOPS waveform.