Pulse Oximeter Simulator Using Optical Waveguide and Mechanical Shutter
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Solution Overview
Problem
Current pulse oximeters face challenges in accurately simulating the light transmission characteristics of living tissue, which is essential for calibration and performance evaluation, as existing simulators often rely on simple attenuators and amplitude modulators that do not accurately replicate the complex light absorption and modulation patterns of human tissue.
Innovation Solution
A living tissue light transmission simulator using an optical waveguide with infrared and red light-sensitive elements, separator circuits, and mechanical shutters controlled by a processing unit to mimic the light transmission and modulation patterns of oxygenated tissue, allowing for precise simulation of blood oxygen saturation and heart rate signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple attenuators and amplitude modulators are used to simulate light transmission, then the device complexity is reduced, but the measurement precision of simulating living tissue light transmission characteristics deteriorates
Solution Approach 1:
The patent uses an optical waveguide to create a physical copy of living tissue's light transmission path, replicating the complex interaction between light and tissue without needing to physically use actual tissue. The waveguide copies the optical properties and geometric characteristics of tissue, enabling accurate simulation while maintaining device simplicity.
Solution Approach 2:
The patent employs variable attenuators and amplitude modulators that can dynamically change optical parameters (transmission intensity, modulation depth) to match different tissue conditions. By adjusting these parameters, the system accurately simulates various tissue types and physiological states without increasing structural complexity.
2Measurement precision
If an optical waveguide with multiple receiving elements and separator circuits is used, then the measurement precision of distinguishing red and infrared light components is improved, but the device complexity increases
Solution Approach 1:
The patent divides the detection function into separate specialized components: an infrared receiving element for detecting infrared light and a broadband receiving element for detecting both red and infrared light. This segmentation allows each component to be optimized for its specific function, improving measurement precision while keeping individual components relatively simple.
Solution Approach 2:
The patent introduces a separator circuit as an intermediary that processes the combined signal from the broadband receiving element and subtracts the infrared component (obtained from the infrared receiving element) to isolate the red light component. This intermediary approach enables precise spectral separation without requiring complex optical filtering mechanisms.
3Measurement precision
If mechanical shutters are used to modulate LED light output, then the simulation accuracy of heartbeat-modulated light signals is improved, but the device complexity and mechanical component requirements increase
Solution Approach 1:
The patent replaces the mechanical shutter system with electronic control of the LEDs. By using voltage-to-current amplifiers and electronic switching circuits, the system achieves the same light modulation effect without moving parts. This substitution maintains heartbeat signal simulation accuracy while eliminating mechanical complexity and improving reliability.
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 simulator effectively replicates the light transmission and modulation patterns of living tissue, enabling accurate calibration and performance testing of pulse oximeters by simulating various oxygen saturation values and heart rates, thereby improving the reliability of blood oxygen measurement.
Implementation Method 1
an infrared receiving element sensitive in at least a portion of the infrared light spectrum and wherein the infrared receiving element may output one or more electrical signals in response to sensed infrared light
Implementation Method 2
a broadband receiving element sensitive in a least a portion of the infrared and red light spectrum wherein the broadband receiving element may output one or more electrical signals in response to sensed broadband light
Implementation Method 3
a first shutter interposed in a light path between the first LED and the optical waveguide, where the first shutter is typically responsive to one or more actuating signals from a processing unit and where the first shutter may mechanically modulate the light emitted from the first LED
Data Source
AI summary
A living tissue light transmission simulator system (208, 308) includes receptors of light (215, 216, 315, 316) in portions of the infrared and red spectral bands and the receptors (215, 216, 315, 316), together with amplification (217, 218, 317, 318), infrared detection (239, 371), spectral separation circuitry (219, 319), and post-separation amplification (220, 221, 338, 339, 340, 320, 321), that may be used to drive at least one light source (222, 223, 322, 361). The living tissue light transmission simulator system (208, 308) includes at least one shutter (225, 235, 324, 363, 450) to mechanically modulate generated light from the at least one driven light source (222, 223, 322, 361) where the modulated light may be directed to a pulse oximeter.