Surface-Emitting Laser Pulses for Deep Tissue Signal Separation
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Solution Overview
Problem
Existing short pulse light sources are inadequate for measuring the inside of scattering or transparent bodies, particularly in near-infrared spectroscopy, as they are affected by skirts that interfere with accurate detection of deep tissue signals.
Innovation Solution
A light source device using a surface emitting laser with a time width of 200 picoseconds or less, where the light intensity is 1/e2 of the peak intensity, and a measurement system that includes a detector to process detection signals from multiple scattering light beams, allowing for precise detection of internal information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional light source is used in TD-NIRS, then the light beam can penetrate the subject, but the skirts of the light pulse interfere with accurate detection of deep tissue signals
Solution Approach 1:
The patent changes the temporal parameter of the light pulse by using a mode-locked laser to generate ultra-short pulses with a width of 100 femtoseconds to 10 picoseconds. This parameter change eliminates the skirts that interfere with deep tissue signal detection, thereby improving measurement precision without sacrificing penetration capability
2Measurement precision
If a short pulse light source is used to reduce skirts, then detection accuracy improves, but the light source technology is insufficient for scattering and transparent bodies
Solution Approach 1:
The patent employs parameter changes in two key aspects: (1) temporal width parameter reduced to 100 fs-10 ps range to eliminate skirts, and (2) wavelength parameter selected in the near-infrared region (700-2500 nm) to optimize penetration through scattering and transparent biological tissues. This combination enables reliable measurement in both scattering and transparent bodies
3Measurement precision
If conventional light sources are used, then the system is simpler, but shallow and deep tissue signals cannot be clearly differentiated
Solution Approach 1:
The patent uses periodic pulsed illumination with ultra-short pulses generated by a mode-locked laser. The time-domain separation of shallow and deep tissue signals relies on the periodic emission of short pulses, allowing photons to travel different path lengths and return at different times. This periodic action enables clear signal differentiation despite the increased complexity of the light source
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 accurate measurement of internal structures by minimizing the impact of skirts, allowing for clear differentiation between shallow and deep tissue signals, enhancing the accuracy of brain and skin blood flow measurements.
Implementation Method 1
a surface emitting laser to emit a light beam to a subject
Implementation Method 2
a detector to detect multiple scattering light beams propagating inside the subject and output a detection signal including information of a detection timing
Implementation Method 3
near-infrared spectroscopy (NIRS) is a technique to observe a blood flow state inside a subject from an optical signal returned after infrared light incident in the subject
Data Source
AI summary
A light source device includes; a surface emitting laser to emit a light beam to a subject; and circuitry to drive the surface emitting laser to emit a light having a time width, a light intensity of which is 1/e2 with respect to a peak of the light intensity, of 200 picoseconds or less.