Optical Liquid Sensor Using Internal Reflection
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Solution Overview
Problem
Existing liquid sensing technologies face challenges with low conductivity liquids, corrosion issues, and malfunctioning in bright ambient light environments, particularly in UV water treatment devices and other applications where reliable liquid detection is crucial.
Innovation Solution
An optical liquid sensor using an LED semiconductor material surrounded by a transparent encapsulant that internally reflects light, with a strategically placed photo sensor to detect changes in light intensity, and optional pulsing of the LED to filter out ambient light, eliminating the need for costly precision lenses and prisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductivity sensing is used to detect liquid presence, then liquid detection capability is achieved, but the sensor fails to reliably detect low conductivity liquids such as distilled water or snowmelt water
Solution Approach 1:
The patent replaces the electrical conductivity sensing system with an optical sensing system. Instead of measuring electrical current between electrodes, the invention uses a light source and photodetector to detect changes in light transmission or reflection when liquid is present, thereby avoiding the limitations of conductivity-based methods for low conductivity liquids.
2Measurement precision
If high sensitivity is increased to detect low conductivity liquids, then detection capability improves, but false triggers occur due to latent moisture on electrodes
Solution Approach 1:
The patent eliminates the electrode-based conductivity sensing system entirely and replaces it with optical sensing. The photodetector detects light signals rather than electrical currents, which prevents false triggering from latent moisture while maintaining high sensitivity for detecting the presence of liquid through optical property changes.
3Reliability
If current flows between sensor electrodes to detect liquid, then liquid presence is detected, but electrolysis occurs causing electrode corrosion and system failure
Solution Approach 1:
The patent replaces the electrical conductivity sensing mechanism with an optical sensing mechanism. A light source emits light through or toward the liquid, and a photodetector detects changes in light intensity or properties when liquid is present. This substitution eliminates current flow between electrodes, preventing electrolysis and electrode corrosion entirely.
4Reliability
If conventional optical sensors with precision lenses and prisms are used, then liquid detection is achieved, but manufacturing cost increases significantly
Solution Approach 1:
The patent extracts and eliminates the complex precision conical lens and prism components from the optical sensing system. By using a simplified optical arrangement with a light source and photodetector that detects light transmission or reflection changes, the invention maintains liquid detection accuracy while removing expensive optical elements, thereby significantly reducing manufacturing costs.
Solution Approach 2:
The patent replaces expensive precision optical components (conical lenses and prisms) with simpler, cheaper optical elements such as standard lenses or even diffuse reflectors. This substitution maintains adequate detection accuracy while dramatically reducing the cost of the sensing system, making it economically viable for consumer applications.
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 solution provides reliable liquid detection across various conductivities and ambient light conditions, reducing costs and preventing false triggers, while minimizing corrosion and enhancing operational reliability in UV water treatment and other applications.
Implementation Method 1
an optical liquid sensor using an LED semiconductor material surrounded by a transparent encapsulant that internally reflects light
Implementation Method 2
a strategically placed photo sensor to detect changes in light intensity
Data Source
AI summary
The inventive optical sensor consists of an LED semiconductor material and elements (herein after the LED components) surrounded by a transparent encapsulant that allows much of the light produced by the LED components to pass while a certain small percentage of the light is internally reflected. The percentage of light internally reflected, depends upon whether at least a front face of the encapsulant is immersed in liquid or in air. The optical liquid sensor also consists of a strategically placed photo sensor that detects the intensity of light that is internally reflected by at least the front face of the encapsulant surrounding the LED. The photo sensor is able to detect the change in intensity of light being internally reflected by at least the front face of the encapsulated LED when the front face, for example, emerges from immersion in a liquid.