Code Reading on Stacked Transparent Sheets via Edge Reflection
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Solution Overview
Problem
Existing methods for reading codes on transparent sheets, such as glass, face challenges due to light refraction and distortion, especially when the camera angle is not perpendicular, making it difficult to acquire high-quality images, particularly with codes engraved by CO2 lasers or during slight laser defocusing due to vibrations.
Innovation Solution
A method utilizing an optical imaging system with a camera and a reflecting device, where the camera's viewing direction intersects the reflecting surface, and the normal to the reflecting surface is tilted relative to the camera's viewing direction, allowing the image of a code to be reflected and captured through the main edge of the sheet, enabling the acquisition of high-quality images by moving the system along the sheets' edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the camera angle is inclined with respect to the edge of the glass sheets to enable code reading through the edge, then the code can be read from stacked sheets, but light refraction causes deformation of the code making it difficult to read
Solution Approach 1:
A reflective device is introduced as an intermediary element between the camera and the code on the glass sheet. The reflective device redirects light from the code through the edge of the glass sheet to the camera, enabling code reading while maintaining optimal optical conditions. This mediator allows the system to achieve both stacked sheet reading capability and acceptable code image quality by controlling the light path.
Solution Approach 2:
The system changes the viewing angle parameter by using a reflective device positioned at a specific angle relative to the glass sheet edge. Instead of directly viewing the code at a high inclination angle (which causes refraction distortion), the reflective device enables viewing at a controlled angle that minimizes refraction effects while still allowing edge-based code reading through stacked sheets.
2Device complexity
If the camera views the code directly through the edge of the glass sheet, then the setup is simple, but strong refraction distortions make code reading impossible at high inclination angles
Solution Approach 1:
The reflective device serves as an intermediary that enables the camera to view the code through the glass sheet edge at optimized angles. This additional component, while increasing device complexity, resolves the refraction distortion problem by controlling the light path between the code, the glass edge, and the camera sensor.
Solution Approach 2:
The solution moves from direct linear viewing to a multi-dimensional light path involving reflection. The reflective device introduces an additional spatial dimension to the imaging geometry, allowing the system to bypass the refraction distortion issue by viewing the code through a different optical path that utilizes the glass sheet edge as a viewing window.
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
This approach allows for the successful acquisition and processing of high-quality images of codes on stacked transparent sheets, even when the camera angle is not perpendicular, overcoming light refraction issues and ensuring accurate code reading.
Implementation Method 1
the direction normal to the reflecting surface is unaligned and tilted with respect to the viewing direction of the camera such that an image of at least a portion of a major side edge of a sheet can be reflected by said reflective surface toward the camera
Implementation Method 2
Glass has a higher refractive index than air, which induces light refraction. This light refraction deforms the code which can be reconstructed by image processing
Data Source
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AI summary
The present invention relates to the reading of codes marked on transparent sheets (101,..., 105), for example sheets of glass, and more particularly on a plurality of transparent sheets arranged opposite one another. The invention aims to provide a method for acquiring images of codes (24) marked on a plurality of transparent sheets that makes it possible to deliver high-quality images and is furthermore easy to implement.