Eye-shield heating with segmented resistive zones
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Solution Overview
Problem
Existing eye-shields with thin-film heating elements face issues of uneven heating due to variations in resistance across and between shields, leading to hot spots and inefficient fog prevention, particularly on irregularly-shaped lenses.
Innovation Solution
A multiple-region eye-shield design with optically-transparent substrates and electrically conductive regions of varying resistivity, allowing for even or customized heating across the lens surface, using a powered circuit to prevent fogging and hot spots without the need for complex PWM systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thin-film heating element is applied uniformly across the eye-shield, then the manufacturing process is simple, but the heating becomes uneven due to variations in resistance across and between shields
Solution Approach 1:
The heating element is divided into multiple discrete regions with different resistivity values. Each region is independently controlled to compensate for variations in resistance across the eye-shield surface and between different shields, achieving uniform heating despite manufacturing variations.
Solution Approach 2:
Different regions of the heating element are assigned different resistivity characteristics tailored to their specific location and heating requirements. This allows each region to be optimized for its local conditions, compensating for resistance variations and preventing hot spots while maintaining overall heating uniformity.
2Device complexity
If a single heating zone is used across the entire eye-shield, then the device complexity is low, but hot spots occur on irregularly-shaped lenses
Solution Approach 1:
The single heating zone is segmented into multiple independent heating regions. Each region can be independently controlled to prevent hot spots on irregularly-shaped lenses by adjusting the power distribution to match the local thermal requirements of different areas.
Solution Approach 2:
Each heating region is assigned specific resistivity characteristics and power control parameters tailored to its location on the irregularly-shaped lens. This local optimization prevents hot spots by ensuring each area receives appropriate heating power based on its geometric and thermal properties.
3Measurement precision
If PWM systems are used to control heating, then temperature control precision is improved, but the device complexity increases
Solution Approach 1:
Instead of using complex PWM control systems, the invention achieves temperature control by varying the resistivity parameters of different heating regions. This parameter-based approach provides sufficient temperature control precision while maintaining simpler device architecture.
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 balanced or customized heating of eye-shields, preventing fogging and hot spots while optimizing power usage, allowing for effective fog prevention and vision correction without excessive space between the eye-shield and the user's eyes.
Implementation Method 1
heating systems employing resistive heating elements on eye-shields
Data Source
AI summary
Eye-shield condensation prevention system for use in a ski goggle, dive mask, medical or testing face shield or the like, that prevents undesirable hot spots on the eye-shield and maintains constant heat, with the ability to compensate for variations in resistance encountered from one eye-shield region to another, and/or one eye-shield to another, comprising a power source, a pulse-width modulator, a microcomputer, a heating element, and a sensing circuit. The microcomputer uses the sensing circuit to sense voltage and determine a value of resistance of the heating element. The microcomputer then uses this value to adjust the duty cycle of the pulse-width modulator, and may employ a two-dimensional table in assisting calculation. Multiple pulse-width modulators may be employed that correspond to a plurality of eye-shield regions and a corresponding plurality of heating elements.