Optical Pressure Sensor Readout Circuitry for Stray Light Rejection
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Solution Overview
Problem
Pressure sensing systems using optical fibers face limitations in signal-to-noise ratio due to stray light interference, necessitating rigorous optical shielding, which complicates their use in clinical settings.
Innovation Solution
The implementation of readout circuitry that controls light sources to inject pulsed signals into optical waveguides, synchronizes detection with pulsation parameters, and employs techniques like lock-in detection and near-IR light to enhance signal-to-noise ratio and reduce sensitivity to environmental light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If continuous wave visible light is used for pressure sensing, then the system can operate with simple components, but the signal-to-noise ratio is limited due to stray light interference
Solution Approach 1:
The patent applies periodic action by using pulsed light sources instead of continuous wave light. The light source emits light in periodic pulses, and the detection system synchronizes with these pulses to detect signals only during the pulse windows. This temporal gating effectively rejects continuous stray light background, dramatically improving signal-to-noise ratio while maintaining system simplicity.
2Reliability
If rigorous optical shielding is implemented to block stray light, then signal integrity is improved, but device complexity and ease of operation are compromised
Solution Approach 1:
The patent replaces complex continuous optical shielding with simple temporal gating using pulsed light and synchronized detection. The shielding requirement is dramatically reduced because the system detects signals only during brief pulse windows when the light source is active, naturally rejecting continuous stray light without requiring elaborate physical shielding structures.
3Reliability
If pulsed light signals are used to improve signal-to-noise ratio, then stray light interference is reduced, but synchronization complexity increases
Solution Approach 1:
The patent implements feedback by using the same pulsed signal that drives the light source also as a reference for the detection system. The detection electronics are synchronized to the pulse timing, creating a feedback loop where the system automatically adjusts its detection window to match the light source pulsing. This self-referencing approach minimizes synchronization complexity while maximizing signal-to-noise ratio.
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 significantly improves signal integrity by reducing stray light interference, allowing for relaxed shielding requirements and enhanced performance in clinical environments.
Implementation Method 1
the light coupling structure is configured to permit inter-waveguide light coupling at the at least one crosspoint when pressure is applied to the at least one crosspoint, wherein the extent of the light coupling depends on the applied pressure
Implementation Method 2
The readout circuitry is further configured to control the at least one light source to implement pulsation of the forward signals and to synchronize acquisition of the return signals by the at least one light detector with the pulsation of the forward signals
Implementation Method 3
employs techniques like lock-in detection and near-IR light to enhance signal-to-noise ratio and reduce sensitivity to environmental light
Implementation Method 4
the at least one light detector is connectable to the at least one second optical waveguide
Data Source
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AI summary
Pressure sensing systems which use intersecting optical waveguides as pressure sensors suffer from limited signal-to-noise ratio (SNR) due to the influence of background light. Disclosed is readout circuitry (105) for such a pressure sensing system (100). The readout circuitry comprises at least one light source (114) and at least one light detector (118), wherein the at least one light source is connectable to at least one first optical waveguide (108) in the pressure sensing system, and wherein the at least one light detector is connectable to at least one second optical waveguide (110). The readout circuitry is configured to control the at least one light source to inject forward signals into the at least one first optical waveguide and to acquire return signals from the at least one second optical waveguide using the at least one light detector. The readout circuitry is further configured to control the at least one light source to implement pulsation of the forward signals and to synchronize acquisition of the return signals by the at least one light detector with the pulsation of the forward signals. By pulsing signals in this manner, the readout circuitry enhances SNR by drastically improving suppression of background light.