Non-Invasive Optical Fluid Level Sensing in Surgical Cassettes
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Solution Overview
Problem
Existing methods for sensing fluid levels in surgical cassettes used in ophthalmic surgery are invasive, prone to errors due to float sticking and orientation sensitivity, and undesirable as they require adding chemicals or color to the fluid.
Innovation Solution
A non-invasive system using a surgical console with vertically arranged light sources and sensor arrays to project and detect light, differentiating between air and fluid interfaces based on reflection and refraction, allowing continuous level sensing without direct contact with the fluid or the need for floats or coloration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coloring the fluid is used to mark the fluid air interface, then the fluid level can be detected, but additional chemicals are added to the surgical fluid which is undesirable
Solution Approach 1:
The patent replaces chemical-based level detection (coloring the fluid) with an optical detection system. Light sources project through the chamber wall and sensor arrays detect light transmission changes at the fluid-air interface, enabling level measurement without adding any chemicals to the surgical fluid.
Solution Approach 2:
The patent introduces an intermediary optical system (light sources and sensor arrays positioned outside the chamber) to detect fluid level. This intermediary method allows level detection through the chamber wall without direct contact with or contamination of the surgical fluid.
2Measurement precision
If floats are used to mark the fluid air interface, then the fluid level can be detected, but floats can stick in the chamber and are sensitive to chamber orientation
Solution Approach 1:
The patent replaces mechanical float-based level detection with an optical detection system. By using light transmission principles through the chamber wall, the system eliminates mechanical components that can stick or be affected by orientation, providing reliable level detection in any chamber position.
Solution Approach 2:
The patent extracts the level detection function from the fluid interior (where floats would operate) and relocates it to the exterior of the chamber. The light sources and sensors are positioned outside the chamber wall, eliminating the need for floating components within the fluid or chamber.
3Object-affected harmful factors
If non-invasive optical sensing is used, then no chemicals or floats are required, but the system requires precise optical alignment and angle of incidence control
Solution Approach 1:
The patent performs preliminary action by pre-configuring the light sources and sensor arrays with specific geometric relationships to the chamber. The optical components are positioned and angled during system assembly to optimize detection, eliminating the need for complex real-time alignment adjustments during operation.
Solution Approach 2:
The patent utilizes parameter changes in light transmission based on the refractive indices of different media (air vs. surgical fluid). By detecting changes in light transmission characteristics as the fluid level changes, the system achieves accurate level detection without mechanical or chemical interventions.
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 high-resolution, continuous, and sensitive fluid level detection, reducing errors and improving flow rate determination, while being insensitive to orientation and not affecting the surgical fluid.
Implementation Method 1
each of the plurality of light sources is positioned to project a corresponding light ray along a corresponding transmission path that has an angle of incidence with a chamber surface so that the corresponding light ray is reflected if a cassette material/first fluid (AIR) interface intersects the corresponding transmission path
Implementation Method 2
a majority of the corresponding light ray is not reflected if a cassette material/second fluid (Balanced salt solution BSS) interface intersects the corresponding transmission path
Data Source
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AI summary
The present invention provides a system and method for detecting the level or presence of a fluid in a surgical cassette (150,500) by projecting light from a linear light source into a wall of a cassette. Depending on the amount a light reflected (220',330,360) or refracted (220,330',360') in the cassette (i.e., due to the cassette material/fluid interface or cassette material/air interface (or other interface)) various portions of a linear sensor array (206,508,314,352) will be more or less illuminated. By examining the illumination of the linear sensor array, the level of fluid in the chamber can be determined.