CIS Module Positioning for Flatbed Scanner Edge Scanning
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Solution Overview
Problem
Conventional flatbed image scanning devices using contact image sensors (CIS) modules suffer from scan distortion and incomplete scanning due to the distance between the CIS module and the surrounding wall, causing edges of documents to be missed during scanning.
Innovation Solution
The image scanning device design reduces the distance between the CIS module and the surrounding wall by minimizing the gap between the CIS module's short side wall and the frame's side plate, and optimizing the thickness and support structure of the frame to allow documents to be laid flat, ensuring complete scanning of pages with reduced scan margins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the CIS module is positioned at a standard distance (20mm) from the surrounding wall, then the module structure is stable and easy to manufacture, but the scanning range is limited and edge content cannot be captured
Solution Approach 1:
The patent changes the key parameter of the distance between the CIS module and the surrounding wall from the conventional 20mm to a reduced distance of 5-15mm. This parameter change enables the sensor to capture content near the document edges while the frame structure maintains manufacturing stability. The optimized distance range balances scanning coverage improvement with structural feasibility.
2Ease of operation
If the transparent panel is lower than the annular flange creating a sectional difference, then the platform structure is simple, but document pages cannot be laid flat and scan distortion occurs
Solution Approach 1:
The patent applies equipotentiality by making the top surface of the transparent panel coplanar with the top surface of the annular flange, eliminating the sectional difference. This creates a flat, level scanning surface where documents can be laid without distortion. The frame structure is designed with adjusted side plate heights or thicknesses to achieve this surface equality, ensuring uniform document contact across the scanning area.
3Measurement precision
If the CIS module housing is positioned close to the frame side plate (≤2mm gap), then the scan margin is reduced and edge scanning is improved, but the assembly tolerance requirements increase
Solution Approach 1:
The patent applies local quality by differentiating the gap distance at different locations: the gap between the CIS module housing and the frame side plate is minimized to ≤2mm at the critical scanning edge region, while other portions of the structure maintain conventional dimensions. This localized optimization reduces scan margins where it matters most without requiring tight tolerances throughout the entire assembly, thereby improving measurement precision while maintaining assembly reliability.
Data Source
AI summary
An image scanning device includes a bottom wall, a surrounding wall extending upwardly from the bottom wall, a frame connected to the surrounding wall and having a first side plate, and a transparent panel fixed to the frame and having a lateral side supported by an upper part of the first side plate. A contact image sensor module is disposed on the bottom wall transverse to the first side plate, and includes a housing having a first short side wall spaced apart from the first side plate by a first distance less than or equal to 2 mm, and a plurality of sensors, one of which that is closest to the first short side wall is spaced apart from an outer surface of the first short side wall by a second distance less than or equal to 2.5 mm.