Interferometric Sensor for Transparent Container Wall Thickness
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Solution Overview
Problem
Existing non-contact methods for measuring the thickness of transparent thermoplastic containers, especially those with colored materials, face challenges in precision due to axial positioning requirements and reduced detection range, leading to inaccurate or impossible measurements.
Innovation Solution
Employing an interferometric sensor that emits a continuous spectrum light ray in the near-infrared range, allowing for precise measurement of container wall thickness without the need for precise axial positioning, and enabling detection through dyed materials by increasing the range and reliability of measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a confocal sensor with chromatic lens is used to measure wall thickness by interferometry, then measurement precision is improved, but axial positioning precision requirements become extremely stringent (measurement range less than 3mm)
Solution Approach 1:
The patent changes the spectral parameters of the light source from visible range to near-infrared range (780-900 nm). This parameter change allows measurement of dyed containers while maintaining measurement precision without requiring extremely tight axial positioning, as the near-infrared light is less affected by the dye absorption
2Measurement precision
If visible spectrum light is used for measurement, then the confocal sensor can detect wall thickness, but dyed materials absorb certain wavelengths reducing reflected ray intensity below detection threshold
Solution Approach 1:
The patent changes the spectral range parameter from visible light (0.4-0.7 μm) to near-infrared light (780-900 nm). This parameter change allows the light to pass through dyed thermoplastic materials with sufficient intensity, as the dye absorption is significantly reduced in the near-infrared range, enabling detection of both transparent and dyed containers
3Productivity
If measurement is performed during high-speed container transfer, then productivity is maintained, but axial positioning varies due to container shape and running speed affecting measurement accuracy
Solution Approach 1:
The patent changes the light wavelength parameter to near-infrared range, which provides a wider measurement range and reduced sensitivity to axial positioning variations. This allows accurate measurements to be taken during high-speed container transfer without requiring extremely precise positioning control
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 method provides reliable and precise measurements of container wall thickness across a wider range, reducing errors and ensuring accurate detection even for thin walls and dyed materials, while maintaining high-speed production processes.
Implementation Method 1
A continuous spectrum light ray is emitted towards the transparent wall of the container. The light ray passes through the wall and reflects off the internal face of the wall. The reflected light ray is detected by an interferometric sensor.
Data Source
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AI summary
The invention relates to a method for measuring, by interferometry, the thickness (s) of the transparent wall (16) of a container (12) made of a thermoplastic material, which comprises: a first step of emitting, from a light source (34), perpendicularly to the transparent wall (16) of the container (12), a light ray (E) having a continuous spectrum, the ray (E) emitted being partially reflected by the external face (18) of the wall (16) and then by the internal face (20) of the wall (16); and a second step of spectrometric analysis, using an interferometric sensor (38) of the interference produced by the superposition of the first and second reflected rays (R1, R2), the interference resulting in a periodic variation in the light intensity (I) of the light wave as a function of frequency (1/?), the variation having a period (P) that is proportional to the thickness (s) of the wall (16) of the container (12).