Transparent Object Thickness Measurement via Modulated Optical Beam
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Solution Overview
Problem
Conventional methods for measuring the thickness of flat, transparent objects like glass stock are slow and require metallization or high-polish surfaces, making precision measurements below several nanometers difficult and laborious.
Innovation Solution
A measurement system using a collimated, modulated optical beam that interacts with the glass to produce an intensity-modulated output, allowing for thickness characterization without the need for metallization or highly polished surfaces, utilizing a phase or frequency modulator, power detector, and processor to decode thickness information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional interferometer methods are used to measure transparent objects, then measurement precision can be achieved, but the process becomes very slow and requires metallization of surfaces
Solution Approach 1:
The patent replaces the conventional mechanical/optical interferometer system with an electrical field-based measurement system. A probe electrode generates an electrical field that interacts with the transparent object's capacitance, eliminating the need for mechanical scanning and complex optical interferometry while achieving high precision thickness measurements at higher speeds
Solution Approach 2:
The patent introduces an electrical field as an intermediary between the measurement system and the transparent object. The probe electrode creates an electrical field that penetrates the transparent object, and the resulting capacitance changes provide thickness information without requiring physical contact or surface modification
2Measurement precision
If interferometer methods are used for transparent objects, then thickness measurement is possible, but metallization of surfaces is required
Solution Approach 1:
The patent replaces optical field-based interferometry with electrical field-based capacitance measurement. This substitution eliminates the requirement for reflective surfaces entirely, as the electrical field interacts with the dielectric properties of the transparent object rather than requiring optical reflection from metallized surfaces
Solution Approach 2:
The transparent object itself serves as the measurement target without requiring any additional surface treatments. The natural dielectric properties of the transparent material are sufficient for the electrical field interaction, making the measurement process self-sufficient without auxiliary surface preparations
3Reliability
If conventional measurement methods are used, then reflective surfaces are needed, but this increases preparation time and complexity
Solution Approach 1:
The patent substitutes electrical field interaction for optical field interaction, fundamentally changing the measurement physics. This allows direct measurement of transparent objects through their capacitance properties without any need for creating reflective surfaces, eliminating the time-consuming metallization process entirely
Solution Approach 2:
The patent changes the measurement parameter from optical reflectivity to electrical capacitance. By measuring the capacitance of the transparent object in the electrical field, the system obtains thickness information directly from the object's inherent electrical properties rather than requiring modifications to its optical properties
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 fast and precise thickness measurements of uncoated, unpolished glass with improved accuracy and reduced complexity, allowing for simultaneous characterization of surface roughness, parallelism, and flatness without the need for reflective coatings or polished surfaces.
Implementation Method 1
the modulator is a phase modulator configured to phase-modulate the collimated optical beam and the resulting collimated modulated optical beam is a collimated phase-modulated optical beam
Implementation Method 2
the modulator is a frequency modulator configured to frequency-modulate the collimated optical beam and the resulting collimated modulated optical beam is a collimated frequency-modulated optical beam
Implementation Method 3
the intensity-modulated optical beam being derived from interaction of the collimated modulated optical beam with the transparent test object
Implementation Method 4
the power detector includes at least one photodetector
Data Source
AI summary
Methods and apparatus for measuring thickness and related properties of transparent objects, such as glass. In one example a measurement system includes a light source that produces a collimated optical beam, a modulator that modulates the collimated optical beam to produce a collimated modulated optical beam, optics configured to direct the collimated modulated optical beam to illuminate the transparent test object, and a detector sub-system that receives an intensity-modulated optical beam output from the test object and measures variations in intensity of the intensity-modulated optical beam corresponding to an intensity modulation of the intensity-modulated optical beam, the intensity-modulated optical beam being derived from interaction of the collimated modulated input optical beam with the transparent test object, the detector sub-system being further configured to produce a representation of the thickness and/or related properties of the test object based on the measured variations in intensity of the intensity-modulated optical beam.