Transparent Foil Surface Inspection for Top-Bottom Particle Separation
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Solution Overview
Problem
Existing methods for inspecting the surfaces of thin flat glass or transparent film cannot distinguish between particles on the top and bottom sides, necessitating a solution to separately determine particle size and distribution on one side of the transparent object.
Innovation Solution
A device and method using a camera and light source with a small illumination angle and predominantly s-polarized electromagnetic radiation to illuminate a line-shaped area, allowing the camera to detect particles on one side by distinguishing reflections based on polarization and reflection behavior, while minimizing light penetration through the transparent object.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a camera-based method with strong dark-field illumination is used to detect contamination, then particles on the top and bottom of the thin flat glass can be detected simultaneously, but it cannot distinguish between particles on the top side and the bottom side
Solution Approach 1:
The inspection system is divided into two separate inspection paths: one for detecting particles on the top surface and another for detecting particles on the bottom surface. Each path uses dedicated light sources and cameras with specific illumination angles, allowing independent detection and side identification of particles on each surface.
Solution Approach 2:
Different illumination conditions are applied to different sides of the transparent object. The top surface is illuminated from above at a specific angle, while the bottom surface is illuminated from below at a different angle. This creates distinct reflection patterns for particles on each side, enabling side identification.
2Measurement precision
If strong dark-field illumination is used to detect particles, then particle detection capability is improved, but light penetration through the transparent object causes interference from the opposite side
Solution Approach 1:
The illumination angles for detecting particles on the top and bottom surfaces are made asymmetric and non-equal. The top surface is illuminated at one angle while the bottom surface is illuminated at a different angle. This asymmetry ensures that light reflected from particles on one side does not reach the camera detecting the other side, eliminating cross-interference.
Solution Approach 2:
Instead of using a single illumination direction, the system uses opposite illumination directions from top and bottom sides with different angles. This inversion approach ensures that reflected light from each side travels in different directions and does not interfere with detection of the opposite side.
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
Effectively distinguishes and determines the location and size of particles on one side of the transparent object by enhancing reflection contrast, reducing interference from the opposite side, and providing precise contamination assessment.
Implementation Method 1
the camera being set up in such a way that it detects the intensity of the electromagnetic radiation reflected back from the line-shaped area
Implementation Method 2
the electromagnetic radiation is predominantly linear and s-polarized (i.e. transversely electrically polarized)
Data Source
AI summary
A device for inspecting a foil-type transparent object. The device has a camera and at least one light source. The light source is arranged such that the electromagnetic radiation emitted by the light source illuminates a line-shaped area of a first surface of the object from above or a second surface of the object from below. The illumination is at a predetermined angle (α) to the respective illuminated surface. The camera is arranged to detect the intensity of the back-reflected electromagnetic radiation in at least a portion of the line-shaped area. The predetermined angle (α) is less than or equal to 15° and the electromagnetic radiation emitted by the light source (20) is predominantly linear and s-polarized. Also a method of inspection.