Optical Spectroscopy System Using Walsh Code Modulation
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Solution Overview
Problem
Current near-infrared spectroscopy systems face challenges in increasing light intensity while maintaining total energy and distinguishing light sources, and they require additional circuitry to minimize noise, which complicates the measurement of oxyhemoglobin and deoxyhemoglobin concentrations in brain tissues.
Innovation Solution
The system employs time-divided spread spectrum codes (TDSSC) to reduce the duration of Walsh codes per unit time, increasing light intensity, and uses Walsh codes for modulating and demodulating light from multiple sources without additional phase locked loop (PLL) circuitry, allowing for more intense light emission and accurate source differentiation, while accumulating signals using a reference clock for noise minimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light emission duration is increased to maintain total energy, then light intensity decreases, but measurement precision deteriorates
Solution Approach 1:
The patent applies periodic pulsed light emission instead of continuous emission, using Walsh codes to modulate the light source in time-divided intervals. This allows the system to emit intense light in short bursts while maintaining total energy delivery over time, resolving the contradiction between light intensity and measurement precision
Solution Approach 2:
The system dynamically changes the temporal parameters of light emission by varying the duty cycle and pulse width according to Walsh code sequences. This enables optimization of light intensity during measurement while maintaining adequate total energy for accurate hemoglobin concentration measurement
2Measurement precision
If additional circuitry such as phase locked loop is added to minimize noise, then noise reduction improves, but device complexity increases
Solution Approach 1:
The system uses the existing reference clock that generates the Walsh codes to also serve as the sampling clock for signal accumulation. This self-service approach eliminates the need for additional phase locked loop circuitry while still achieving effective noise minimization through synchronous detection
Solution Approach 2:
The reference clock is designed to perform multiple functions: generating the Walsh code sequences for light modulation and simultaneously serving as the sampling clock for signal accumulation. This multi-functionality reduces device complexity while maintaining noise minimization capabilities
3Measurement precision
If Walsh codes are used to modulate multiple light sources, then source differentiation improves, but device complexity increases
Solution Approach 1:
The patent divides the light emission into time segments using Walsh code sequences, where each light source is assigned a unique Walsh code pattern. This segmentation allows multiple light sources to operate simultaneously without interference, improving source differentiation while avoiding the need for complex switching mechanisms
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
This approach enables more intense light transmission with the same total energy, reduces white Gaussian noise, and accurately distinguishes light sources, improving the measurement of oxyhemoglobin and deoxyhemoglobin concentrations without the need for additional circuitry, enhancing the precision of brain tissue analysis.
Implementation Method 1
Hemoglobin is also a kind of the chromophores, and exhibits a larger degree of absorption than water in a near-infrared region. Since absorption coefficients of oxyhemoglobin and deoxyhemoglobin vary with wavelengths in the near-infrared region
Implementation Method 2
the emitted laser or light is detected by a detector (D)
Data Source
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AI summary
Disclosed are a time division spread spectrum code-based optical spectroscopy system capable of controlling irradiation power and a method for controlling the optical spectroscopy system. The optical spectroscopy system may comprise: a light transmission unit for irradiating light to a particular region of a subject by means of a light source, wherein the light is irradiated so that the overall energy is consistently maintained by reducing the light irradiation time and increasing the strength of the light; and a light receiving unit for collecting emergent light which has passed through the particular region.