Document Reader Variable Optical Filter for Balanced Illumination
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Solution Overview
Problem
Existing document readers face challenges with non-uniform illumination, leading to reduced dynamic range and difficulty in removing unwanted marks, which affects image quality and processing efficiency.
Innovation Solution
A document reader system with a transparent scan area, a light source, an optical filter with variable light transmission, and an image sensor, which balances illumination intensity using a Graduated Neutral Density (GND) filter to enhance dynamic range and signal-to-noise ratio, allowing for improved image capture and processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If illumination sources are placed close to one side of the document, then the illumination intensity is sufficient for the document, but the illumination becomes non-uniform across the document surface
Solution Approach 1:
The illumination system is divided into multiple independent illumination sources positioned at different locations (first side and second side of the document). Each source contributes to illuminating different portions of the document, and their combined effect achieves uniform illumination across the entire document surface while maintaining sufficient intensity.
2Measurement precision
If exposure time is decreased to reduce overexposure in brighter areas, then the brighter areas are not overexposed, but the dynamic range of the image is reduced
Solution Approach 1:
The illumination uniformity is established in advance through the strategic placement of multiple illumination sources before image capture. This preliminary illumination setup ensures that the document receives uniform lighting across all areas, allowing the image sensor to capture the full dynamic range without requiring post-capture exposure adjustment or flattening operations.
3Stability of the object's composition
If multiple illumination sources are placed on opposite sides of the document, then uniform illumination is achieved, but the device complexity increases
Solution Approach 1:
The illumination sources are designed to serve multiple functions: they provide uniform illumination across the document, enable the document to be viewed from different angles, and can be independently controlled to accommodate different document types and lighting requirements. This multi-functionality justifies the added complexity by delivering superior performance across multiple tasks.
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 system achieves balanced illumination, increasing the dynamic range and signal-to-noise ratio, facilitating easier image flattening and removal of unwanted marks, resulting in higher-quality document images.
Implementation Method 1
The optical filter is positioned between the light source and the transparent scan area and has a variable light transmission configured to modify light intensity of the light emitted by the light source
Data Source
AI summary
A document reader system configured to capture an image of a document is described. The document reader system includes a document reader having a transparent scan area, a light source, an optical filter, and an image sensor. The transparent scan area is configured to receive the document on a first side of the transparent scan area. The light source is positioned on a second side of the transparent scan area opposite the first side and is configured to emit light towards the transparent scan area. The optical filter is positioned between the light source and the transparent scan area and has a variable light transmission configured to modify light intensity of the light emitted by the light source. The image sensor positioned on the second side of the transparent scan area and configured to capture the image of the document on the first side of the transparent scan area.