Document Edge Extraction Using Line Sensor Brightness Detection
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Solution Overview
Problem
Existing document scanning techniques fail to effectively correct excessive reflected light issues, leading to inaccurate document edge extraction due to shadows and bright reflections caused by uneven light distribution during scanning.
Innovation Solution
An image processing method that extracts the document area by detecting excessive light areas at the edges and removing them, using a line sensor to illuminate the document from the upstream or downstream side, and calculating the width of bright reflections based on document thickness, luminance, and tilt to correct for these issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the document is obliquely irradiated with scanner light to enable edge detection, then the document edge can be extracted, but shadows and excessive reflected light are generated causing inaccurate extraction
Solution Approach 1:
The patent performs preliminary detection of shadow and excessive reflected light areas before final document edge extraction. By identifying these problematic areas in advance and excluding them from the extraction process, the system achieves accurate document edge detection without being affected by lighting artifacts.
Solution Approach 2:
The patent converts the harmful effect of excessive reflected light and shadows into a useful detection signal. By detecting the characteristics of these light anomalies (brightness thresholds, spatial distribution), the system identifies and excludes them from document edge extraction, transforming a previously problematic factor into a basis for improved extraction accuracy.
2Device complexity
If conventional edge extraction processing is applied to the entire document positioning plate area, then the process is simple, but shadows and bright areas cause inaccurate document area extraction
Solution Approach 1:
The patent segments the document positioning plate area into multiple regions based on luminance characteristics. By dividing the processing area into regions with different lighting conditions and applying appropriate extraction methods to each segment, the system achieves both processing efficiency and extraction accuracy without requiring complex global processing.
Solution Approach 2:
The patent applies different extraction strategies to different local regions of the document positioning plate. Areas with excessive reflected light or shadows use specialized detection and exclusion methods, while normal areas use standard edge extraction, optimizing both accuracy and processing efficiency for each local condition.
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 method accurately extracts the document area by removing excessive light areas, improving the precision of edge detection and reducing processing time by using pre-calculated correction coefficients for document tilt and luminance.
Implementation Method 1
an image read by a scanner on the whole surface of the document positioning plate
Implementation Method 2
the document is obliquely irradiated with the light of the scanner, so that such shadow and excessive reflected light are generated
Data Source
AI summary
An image processing method in which the image of a document is extracted from an image including the image of the document on a document positioning table, acquired by a line sensor scanning the document placed on the document positioning table while illuminating the document from the upstream side or the downstream side of the scanning includes extracting the edge of the image on the document positioning table to set a provisional document area based on the edge, detecting a bright area where light incident on the line sensor is excessive, at the illuminated edge on the upstream side or the downstream side in the scanning direction from the image of the provisional area, and determining the area of the document by removing the area where light is excessive from the provisional area.