Container Wall Thickness Measurement Using Diffusing Screen
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Solution Overview
Problem
Existing methods for measuring the thickness of transparent or translucent containers, such as glass bottles, face challenges with significant deviations in reflected beam angles and positional deviations due to non-parallel surfaces, leading to optical aberrations and operational inefficiencies.
Innovation Solution
An optical system combining a light source, a dimension light sensor, and a focusing system with a diffusing screen, capable of handling beams with angles up to 40°, and a second objective to image the diffusing screen on a light sensor, allowing for accurate thickness measurement across a wide range of containers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a narrow light beam is projected onto the container wall at an angle to measure thickness, then the thickness measurement can be obtained through triangulation, but significant deviations in reflected beam angles and positional deviations occur due to non-parallel surfaces, leading to optical aberrations
Solution Approach 1:
A diffusing screen is introduced as an intermediary element between the light beam and the light sensor. The screen receives the light beam and diffuses it in multiple directions, allowing the optical system to recover beams that have undergone significant angular deviations due to non-parallel container walls. This mediator enables reliable thickness measurement even when direct beam recovery would fail.
Solution Approach 2:
The optical system parameters are specifically designed to handle large angular deviations. The first objective lens is configured with a numerical aperture and focal length that enable it to recover and focus beams entering at angles up to 40° relative to the optical axis. This parameter optimization allows the system to maintain measurement precision despite significant geometric variations in container shapes.
2Adaptability or versatility
If the optical system recovers reflected beams with large angles relative to the optical axis, then thickness measurement is possible for containers with non-parallel surfaces, but optical aberrations increase and light losses occur
Solution Approach 1:
The diffusing screen acts as a mediator that redistributes light energy. Instead of attempting to directly recover highly angled reflected beams (which would cause significant optical losses and aberrations), the screen diffuses the incident beam in multiple directions, creating new propagation paths that are more easily captured by the optical system with reduced aberrations.
Solution Approach 2:
The problem is shifted from the angular domain to the spatial domain. Rather than trying to recover beams at extreme angles (angular dimension), the diffusing screen creates a spatial distribution of light spots on its surface. The optical system then images these spatially distributed spots, effectively transforming the angular deviation problem into a spatial imaging problem that is easier to handle optically.
3Measurement precision
If a lens is moved to recover reflected rays when surface angle changes, then the reflected ray can be recovered, but the system becomes complex and impractical for industrial use
Solution Approach 1:
Instead of moving the lens to track the reflected ray (active tracking approach), the diffusing screen is used to create a stationary pattern of light spots that automatically adapts to surface angle changes. The optical system remains fixed while the diffusing screen passively generates the necessary light distribution, inverting the problem-solving approach from active adjustment to passive adaptation.
Solution Approach 2:
The diffusing screen automatically adapts to different container geometries and surface angles without requiring external control or adjustment mechanisms. When the container geometry changes, the light spots on the diffusing screen automatically shift position, and the optical system continuously images these spots, providing self-adjusting measurement capability without complex control systems.
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 economical thickness measurement of container walls with significant deviations, reducing optical aberrations and improving operational reliability.
Implementation Method 1
These light reflections on these two surfaces occur according to the laws of specular reflection of the incident beams, that is to say symmetrically to the incident beam with respect to the normal to the surface at the point of impact of the incident beam.
Implementation Method 2
part of the beam is refracted in the wall then reflected by the inner surface of the wall
Implementation Method 3
an optical system for recovering and focusing on the detection plane of the light sensor, light beams reflected by the exterior and interior surfaces of the wall
Data Source
Figure 1~1A
Figure 2~3
Figure 4~5
AI summary
The invention relates to a facility for measuring the thickness of the wall of containers, comprising: an optical system (15) for collecting light beams reflected by the outer and inner surfaces of the wall and focussing same on the detection plane of the light sensor (14). According to the invention, the optical system (15) for collecting and focussing the light beams comprises: a first objective (21) having an object plane located in the vicinity of the point of impact of the light beam incident on the wall (3); an at least translucent diffusing screen (23) arranged in the image plane of the first objective (21) in such a way as to physically represent the light beams collected by the first objective (21) in the form of hot spots (Ti); and a second objective (25) comprising the diffusing screen (23) as the object plane and the light sensor (14) as the image plane.