Silicon Photomultiplier Calibration for Portable FD-DOS Systems
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Solution Overview
Problem
Current frequency domain diffuse optical spectroscopy (FD-DOS) systems are limited by the large footprint of high-voltage modules required for avalanche photodiodes (APDs) and photomultiplier tubes (PMTs), which restricts their portability and dynamic range due to the need for high voltage bias, and have limited sensitivity and dynamic range.
Innovation Solution
The use of silicon photomultipliers (SiPMs) as optical detectors, which operate at a lower voltage bias and have a smaller footprint, coupled with a radio frequency signal generator, light source, analog to digital conversion circuit, and electronic processing circuit, enabling modulated light detection and analysis for tissue characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If avalanche photodiodes (APDs) or photomultiplier tubes (PMTs) are used as optical detectors, then detection sensitivity is improved, but device footprint increases due to large high-voltage modules
Solution Approach 1:
The patent changes the operating voltage parameter from high voltage (required by APDs and PMTs) to lower voltage (operating range of SiPMs, typically 10-50V). This parameter change enables the use of SiPMs which provide comparable detection sensitivity to APDs/PMTs but with significantly reduced high-voltage module footprint, resolving the contradiction between sensitivity and device size
Solution Approach 2:
The patent replaces expensive, bulky APDs/PMTs with more compact, cost-effective SiPMs. While SiPMs have different operational characteristics, they provide equivalent or superior performance in FD-DOS applications with reduced size and cost, effectively substituting the previous detector technology
2Measurement precision
If high voltage bias is supplied to APDs or PMTs, then optical detection performance is improved, but system portability deteriorates
Solution Approach 1:
The patent changes the voltage bias parameter from high voltage to lower voltage operation. SiPMs operate at lower voltages (10-50V) compared to APDs/PMTs, which simplifies the high-voltage module design and enables portable FD-DOS systems while maintaining optical detection performance through the inherent gain mechanism of SiPMs
3Adaptability or versatility
If the dynamic range is extended beyond linear response range, then measurement capability is improved, but measurement accuracy deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the system operates the SiPM in its nonlinear response region and uses electronic feedback to linearize the output. The feedback circuit adjusts the operating point or compensates for nonlinearities, enabling extended dynamic range while maintaining measurement accuracy through active correction
Solution Approach 2:
The patent changes the operational regime by deliberately operating the SiPM outside its traditional linear region and using parameter adjustment through feedback control to achieve both extended dynamic range and maintained accuracy, representing a fundamental change in how the detector is utilized
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 configuration enhances the portability and sensitivity of FD-DOS systems by allowing extended source-detector separations and increased depth penetration, with improved signal-to-noise ratios and the ability to accurately recover optical properties at higher wavelengths, facilitating more effective tissue imaging.
Implementation Method 1
The silicon photomultiplier is configured to detect analog signals indicative of amplitude and phase of radio frequency modulation components of detected optical signals
Implementation Method 2
The light source is coupled to the driver and is configured to generate modulated light at a plurality of different wavelengths and a plurality of different modulation frequencies
Data Source
AI summary
A frequency domain diffuse optical spectroscopy (FD-DOS) device and calibration method. The FD-DOS device includes a radio frequency signal generator, a driver, a light source, a silicon photomultiplier, an analog to digital conversion circuit, and an electronic processing circuit. The light source is configured to generate modulated light at a plurality of different wavelengths and modulation frequencies. The silicon photomultiplier is configured to generate analog detection signals indicative of detected optical signals. The analog to digital conversion circuit is configured to generate digital sample values from the analog detection signals. The electronic processing circuit is configured to determine absorption values and scattering values based on the digital sample values. The electronic processing circuit is also configured to determine concentration values based on the absorption values and the scattering values. The electronic processing circuit is further configured to determine an image stream based on the concentration values.