Hybrid Stress Characterization of Chemically Strengthened Substrates
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Solution Overview
Problem
Existing methods for characterizing stress in chemically strengthened transparent substrates require separate systems for evanescent prism coupling spectroscopy (EPCS) and light-scattering polarimetry (LSP), leading to time-consuming and risky handling of the substrates between measurements, and lack the capability to fully characterize stress profiles from the surface to the center.
Innovation Solution
A hybrid measurement system combining EPCS and LSP capabilities in a single setup, allowing simultaneous measurement of surface and near-surface stress profiles, central tension, and depth of compression without substrate handling, using a scattered light polarimetry (LSP) subsystem with a light source, optical compensator, and support plenum for full stress characterization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate EPCS and LSP measurement systems are used to characterize stress in chemically strengthened substrates, then near-surface stress properties can be measured by EPCS and central tension properties can be measured by LSP, but the process requires moving the substrate between systems which increases handling time and risk of breakage
Solution Approach 1:
The patent combines EPCS and LSP measurement capabilities into a single integrated hybrid measurement system. The system includes both EPCS optical components (prism, detector) and LSP optical components (polarizer, compensator, detector) arranged to measure both near-surface and central tension stress properties of chemically strengthened substrates without requiring physical movement of the substrate between separate measurement systems, thereby eliminating handling time and breakage risks
2Measurement precision
If separate EPCS and LSP measurement systems are used, then each system can be optimized for its specific measurement type, but the complexity of operating and transitioning between two systems increases
Solution Approach 1:
The hybrid measurement system is designed as a universal platform that performs both EPCS and LSP measurements. The system includes a substrate holder that can position the substrate for both measurement modes, optical components for EPCS (prism, spectral detector) and LSP (polarizer, compensator, intensity detector), and control logic that automatically switches between measurement modes, providing multi-functionality in a single integrated device
3Measurement precision
If the substrate is moved between EPCS and LSP measurement systems, then full stress characterization can be achieved, but the risk of substrate breakage during handling increases
Solution Approach 1:
The patent merges EPCS and LSP measurement capabilities into a single hybrid system where the substrate remains stationary on the substrate holder throughout both measurements. The system acquires near-surface stress data via EPCS and central tension data via LSP without requiring substrate removal or repositioning, thereby maintaining substrate integrity and eliminating handling-induced breakage risks
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 efficient and reliable full stress characterization of chemically strengthened substrates, reducing handling risks and time, and providing comprehensive stress profile data including surface compressive stress, near-surface compressive stress profile, depth of layer, central tension, and depth of compression.
Implementation Method 1
The optical compensator includes a half-wave plate and a half-wave plate actuator operable to rotate the half-wave plate
Implementation Method 2
a diffuser and a diffuser actuator operable to translate the diffuser along the optical path
Implementation Method 3
Stress in the CS substrate causes optical retardation along the light path, with the amount of stress being proportional to the derivative of the optical retardation
Data Source
AI summary
A scattered light polarimetry (LSP) sub-system of a hybrid system for characterizing stress in a chemically-strengthened (CS) substrate having a top-surface and a near-surface waveguide, includes a LSP light source system, an LSP light source actuator coupled to the LSP light source system, and an optical compensator within an optical path of a LSP laser beam emitted by the LSP light source system. The optical compensator includes a half-wave plate, a half-wave plate actuator, a diffuser, and a diffuser actuator. The LSP sub-system further includes a LSP detector system in optical communication with the optical compensator through an LSP coupling prism having a LSP coupling surface, a focusing lens and a focusing lens actuator, and a support plenum having a surface and a measurement aperture, the support plenum configured to support the CS substrate at a measurement plane at the measurement aperture, and to operably support the LSP coupling prism.