Chromatic Sensor System for Ophthalmic Lens Coating Quality
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Solution Overview
Problem
Current methods for inspecting the quality of ophthalmic lenses, particularly contact lenses, are subjective and inaccurate, especially when it comes to determining wettability and resistance to proteinaceous deposits, due to the cumbersome nature of contact angle measurements and the variability of coating thickness and hydrophilicity.
Innovation Solution
A method using a chromatic sensor system to immerse the lens in a fluid and measure reflectivity values by illuminating segments of the lens with white light, determining the dominant wavelength and reflectivity, and comparing these values to reference values to assess the lens's quality, including the use of modulated light intensities and wavelength dispersive optical elements for precise measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact angle measurement is used to determine wettability, then wettability can be assessed, but the method is cumbersome and inaccurate especially for coated lenses
Solution Approach 1:
The patent replaces the mechanical contact angle measurement method with an optical measurement system using a chromatic sensor and spectrometer. The system illuminates the lens surface with white light and analyzes the reflected light spectrum to determine the dominant wavelength, which correlates with wettability. This substitution eliminates the need for manual liquid application and contact angle measurement, providing automated, objective, and more accurate results for both coated and uncoated lenses.
Solution Approach 2:
The patent changes the measurement parameter from contact angle to dominant wavelength of reflected light. By analyzing the spectral composition of reflected white light and identifying the dominant wavelength, the system provides a more sensitive and accurate indicator of surface wettability. This parameter change enables better detection of coating properties and variations in hydrophilicity that contact angle measurements miss.
2Reliability
If manual rubbing tests are performed to assess coating quality, then qualitative results can be obtained, but the results are subjective and inaccurate
Solution Approach 1:
The patent replaces subjective manual rubbing tests with an objective optical measurement system. The chromatic sensor system with spectrometer analyzes the reflected light spectrum to determine the dominant wavelength, providing quantitative and reproducible coating quality assessment. This eliminates human subjectivity and variability while maintaining operational simplicity through automated measurement and comparison with reference values.
Solution Approach 2:
The patent creates an optical signature (dominant wavelength and reflectivity values) that serves as a fingerprint for coating quality. By comparing the measured optical characteristics against reference values from known good coatings, the system objectively assesses coating quality without requiring physical contact or subjective evaluation. This copying approach transforms tactile rubbing tests into precise optical measurements.
3Manufacturing precision
If coating thickness and hydrophilicity are varied to improve lens properties, then desired lens characteristics can be achieved, but repeatability of polymer type and coating thickness becomes problematic
Solution Approach 1:
The patent implements a feedback mechanism where the dominant wavelength and reflectivity values of the coating are measured and compared against reference values. This feedback loop enables real-time quality control and adjustment of coating parameters during manufacturing. By monitoring the optical properties and comparing them to established references, the system ensures consistent coating thickness and hydrophilicity while maintaining the ability to adjust parameters to achieve desired lens characteristics.
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 method provides objective, reproducible, and non-destructive assessments of ophthalmic lens quality, allowing for the determination of wettability, coating efficiency, and mechanical endurance, reducing the reliance on subjective tribological methods and improving the accuracy of coating characterization.
Implementation Method 1
determining a dominant wavelength of the reflected light, which corresponds to the transition from the fluid to the at least one segment of the front surface or the back surface of the ophthalmic lens
Implementation Method 2
directing light reflected from the at least one segment of the front surface or of the back surface of the ophthalmic lens to a spectrometer
Implementation Method 3
at the determined dominant wavelength of the reflected light measuring a reflectivity value of the least one segment of the front surface or the back surface of the ophthalmic lens
Data Source
Figure 1
Figure 2~3
AI summary
A method for characterizing an ophthalmic lens having a front surface and a back surface comprises the steps of: - immersing the ophthalmic lens in a fluid, and with the aid of a chromatic sensor system: - determining a transition from the fluid to the front surface or to the back surface to identify the location of the front surface or back surface, - by illuminating at least one segment of the front surface or the back surface with incident white light; - directing light reflected from the at least one segment to a spectrometer; - determining a dominant wavelength of the reflected light, which corresponds to the transition from the fluid to the at least one segment; - at the determined dominant wavelength measuring a reflectivity value of the least one segment; - storing each measured reflectivity value, - comparing each stored measured reflectivity value with a corresponding reference reflectivity value, and - from a difference between the respective stored measured reflectivity value and the corresponding reference reflectivity value determining the quality of the inspected surface.