Oblique Front Lighting for Transparent Media Decoration Inspection
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Solution Overview
Problem
Existing inspection systems for transparent media decorations at edges are inadequate, as they often obscure decoration visibility, fail to accurately measure opacity, and struggle with distinguishing decoration defects from other defects due to issues like uneven contrast and glare, especially when the decoration is wet or glossy.
Innovation Solution
A system and method that utilize an illuminator directing light at an oblique angle relative to the surface opposite the decoration, combined with an optical element and sensor to capture and process light, allowing for improved visibility of decoration edges and accurate measurement of opacity, while suppressing unwanted artifacts and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional backlighting is used to inspect decoration, then opacity measurement is enabled, but edge contours and surface defects direct light away from the image sensor resulting in dark areas that obscure decoration and interfere with measurement
Solution Approach 1:
The patent inverts the conventional backlighting approach by using front lighting instead. The light source is positioned on the same side as the image sensor, illuminating the decoration directly rather than from behind. This inversion eliminates the problem of edge contours directing light away from the sensor, as light now travels through the decoration toward the sensor without being blocked by edge geometry.
Solution Approach 2:
The patent applies local quality by using oblique lighting at specific angles (e.g., 45 degrees) relative to the surface normal. This angled illumination creates optimal contrast for decoration features while minimizing the impact of surface defects and edge contours. The lighting angle is specifically chosen to highlight decoration edges and patterns without being affected by gloss or highlights.
2Difficulty of detecting and measuring
If dark field lighting is used to emphasize edge contours, then defects become more visible, but decoration margins become essentially invisible and opacity measurement is not provided
Solution Approach 1:
The patent inverts the dark field lighting approach by using front illumination instead of oblique backlighting. The light source and image sensor are positioned on the same side, allowing direct illumination of decoration features. This inversion ensures that decoration margins are visible while still enabling defect detection through controlled lighting angles that create appropriate contrast.
Solution Approach 2:
The patent changes the lighting parameters by using front lighting at oblique angles rather than conventional dark field illumination. This parameter change allows the system to capture both decoration features and defects simultaneously, as the lighting geometry is optimized to illuminate decoration margins while still highlighting surface imperfections through shadow and contrast effects.
3Measurement precision
If front lighting is used for in-line inspection, then decoration color and reflectance can be measured, but gloss and highlights obscure the decoration particularly when wet
Solution Approach 1:
The patent applies local quality by using oblique front lighting at specific angles (e.g., 45 degrees) rather than normal incidence lighting. This angled illumination reduces the impact of gloss and highlights by minimizing specular reflections that occur at normal incidence. The lighting angle is specifically chosen to illuminate decoration features while reducing the visibility of glossy surfaces, particularly important for wet or freshly applied decoration.
4Difficulty of detecting and measuring
If conventional edge inspection systems are used, then edge quality (chips, cracks) can be detected, but decoration features are obscured and it is difficult to discriminate decoration defects from other defects
Solution Approach 1:
The patent inverts the inspection approach by using front lighting instead of conventional backlighting for edge inspection. This inversion allows both edge quality and decoration features to be visible simultaneously in the same image. The lighting geometry is specifically designed to illuminate decoration on the surface while still highlighting edge defects through shadow and contrast, enabling discrimination between decoration defects and other defects.
Solution Approach 2:
The patent creates a universal inspection system that can detect both edge quality and decoration features using the same lighting and imaging configuration. The front oblique lighting approach serves multiple functions: it illuminates decoration margins, highlights edge contours, and reveals both decoration defects and other defects in a single image, eliminating the need for separate inspection 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
The solution enhances the visibility of decoration edges and accurately measures opacity, enabling better qualification of decoration quality and coverage, even on edges with complex profiles or minor defects, and is suitable for both interior and exterior edges.
Implementation Method 1
an illuminator to direct light to the transparent media for inspection, wherein the illuminator directs light to the transparent media at an oblique angle relative to a surface of the transparent media which is opposite the surface with the decoration
Data Source
AI summary
There is provided a system for inspecting an edge area of a transparent media, the transparent media having a decoration on a surface, the system includes: an illuminator to direct light to the transparent media for inspection, wherein the illuminator directs light to the transparent media at an oblique angle relative to a surface of the transparent media which is opposite the surface with the decoration; an optical element to capture light transmitted through the transparent media; and a sensor to obtain an image from the light captured by the optical element. There is also provided a method for inspecting an edge area of a transparent media, where the transparent media has a decoration on a surface.