Curved Surface Thin Film Analysis Using Polarization Detectors
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Solution Overview
Problem
Existing thin film coating measurement techniques are limited to flat surfaces and static coatings, making it difficult to accurately measure dynamic and curved surfaces, such as the lipid layer of the human eye, due to strict alignment requirements and the inability to measure extended regions simultaneously without a reference optical path.
Innovation Solution
A method and apparatus using a two- or three-detector system with non-polarizing beamsplitters and analyzers to measure thin film coatings on curved surfaces, allowing for extended area analysis with relaxed alignment tolerances and the use of a reference phantom for calibration, enabling the measurement of dynamic and multiple-layer coatings without the need for a reference optical path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional thin film measurement techniques are used on flat surfaces with strict alignment requirements, then measurement precision is maintained, but the ability to measure curved and dynamic surfaces is lost
Solution Approach 1:
The invention divides the measurement task into multiple detector channels (at least two detectors) that simultaneously capture different polarization components of reflected light from curved surfaces. This segmentation allows each detector to handle a specific aspect of the measurement, enabling accurate thickness and refractive index measurement across extended curved areas without requiring the entire surface to be in perfect alignment
Solution Approach 2:
The invention transitions from measuring only flat surfaces to measuring curved surfaces by introducing multiple detection angles and polarization dimensions. The use of at least two detectors with different polarization analyzers creates an additional measurement dimension that compensates for surface curvature, allowing the system to maintain measurement precision while extending adaptability to curved and dynamic surfaces
2Area of stationary object
If a reference optical path is used to measure extended regions simultaneously, then measurement coverage is improved, but device complexity increases
Solution Approach 1:
The invention merges the measurement of extended regions into a single optical path without requiring a separate reference path. By using at least two detectors that simultaneously detect different polarization components of light reflected from the sample, the system achieves extended area measurement while avoiding the complexity of additional reference optical paths
Solution Approach 2:
The system uses the sample itself (or a reference phantom with similar curvature) to provide the necessary measurement information through its reflected light properties. The curvature of the sample surface is utilized rather than fought against, and the reflected light naturally contains the information needed for extended area measurement, eliminating the need for complex reference paths
3Measurement precision
If strict alignment requirements are imposed on measurement systems, then measurement precision is maintained, but ease of operation deteriorates
Solution Approach 1:
The invention changes the measurement parameters from requiring precise geometric alignment to utilizing polarization state analysis. By measuring the polarization components of reflected light with at least two detectors, the system maintains measurement precision while becoming much more tolerant of alignment variations and suitable for dynamic surfaces that cannot be precisely positioned
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 accurate measurement of thin film thickness and refractive index over curved areas, including dynamic and multiple-layer coatings, with improved alignment flexibility and reduced calibration complexity, effectively addressing the limitations of prior art.
Implementation Method 1
at least two analyzers, one for receiving one of the optical branches from the beamsplitter and analyzing a polarization state of the reflected light
Implementation Method 2
at least one non-polarizing beamsplitter to receive the reflected light from the imaging group and split the reflected light into more than one optical branch
Data Source
AI summary
A thin film analysis apparatus and method for a curved surface is disclosed. The apparatus includes an illuminator, a sample, an imaging group, one or more beamsplitters, optional focusing groups, polarization analyzers, detectors and optional display and analysis systems. The image series are recorded, preferably substantially synchronously. The system can be calibrated by as few as one reference phantom that has the same or substantially similar geometry as the sample under test. Based on calibration, a lookup table of the effective reflectance can be created, which is proportional to the portion of the light that reaches the detectors, or the mutual subtraction of the effective reflectance values of all possible combinations of the unknown optical parameters within certain search ranges of the sample. The experimentally measured results are compared with the lookup table, and optical properties, for example, the thicknesses and refractive indices of the thin film can be determined.