Strip-shaped Density Reference Members for Shading Correction
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Solution Overview
Problem
Existing image reading apparatuses face challenges in achieving uniform brightness across scanned documents due to light amount variations in both the main and sub scanning directions, which current shading correction methods do not adequately address.
Innovation Solution
The image reading apparatus incorporates a light source device that moves in the sub scanning direction and strip-shaped density reference members positioned at multiple points, including upstream, center, and downstream areas, to calculate and apply shading correction data on a pixel-to-pixel basis, ensuring uniform brightness across the scanned document.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single white reference plate is located in the upstream sub-scanning direction, then shading correction can be performed for main scanning direction density variation, but uniform brightness cannot be achieved across the entire readable area including sub-scanning direction variations
Solution Approach 1:
The single reference plate is segmented into multiple strip-shaped density reference members positioned at different locations (upstream, center, downstream) in the sub-scanning direction. Each strip independently captures density characteristics for its specific region, enabling localized correction across the entire readable area while maintaining a relatively simple overall structure.
Solution Approach 2:
The reference members are arranged not only in the main scanning direction but also distributed across the sub-scanning direction at multiple positions. This two-dimensional distribution allows the system to capture and correct density variations in both scanning directions, achieving comprehensive brightness uniformity.
2Measurement precision
If multiple reference members are positioned at upstream, center, and downstream locations in the sub-scanning direction, then uniform brightness across the readable area is achieved, but the device complexity increases
Solution Approach 1:
Each strip-shaped density reference member is specifically positioned to capture density characteristics of its local region (upstream, center, or downstream area). This localized measurement approach ensures high correction accuracy for each specific zone while using a minimal number of reference members - only three strategically positioned strips are needed to cover the entire readable area.
3Reliability
If strip-shaped density reference members are used instead of a single white reference plate, then shading correction in both main and sub-scanning directions is achieved, but the ease of operation decreases
Solution Approach 1:
The strip-shaped density reference members are pre-positioned at optimal locations (upstream, center, downstream) during system setup or manufacturing. This preliminary arrangement ensures that during normal operation, the system automatically captures density data from all critical regions without requiring complex real-time adjustments or manual intervention, thereby maintaining high reliability while simplifying operation.
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 solution effectively corrects for light amount variations in both scanning directions, resulting in high-quality image data with uniform brightness, even with directional light sources, and allows for automatic shading correction, enhancing the accuracy and reliability of image reading.
Implementation Method 1
a light source device configured to move an irradiated region in a sub scanning direction and irradiate a printed document placed on a platen glass of a document table with a light
Implementation Method 2
a reader configured to convert a light reflected from the printed document into the image data so as to read
Data Source
AI summary
An image reading apparatus includes a light source device, a reader, a plurality of strip-shaped density reference members, and a shading corrector. The plurality of strip-shaped density reference members that extend along main scanning direction. The plurality of strip-shaped density reference members are separately disposed in at least three positions including an upstream end portion, a center portion, and a downstream end portion in the moving direction of the sub scanning direction within a readable area of the reader. The shading corrector is configured to calculate shading correction data using density distribution data obtained by reading the plurality of strip-shaped density reference members with the reader and correct image data of the printed document on a pixel to pixel basis, based on the shading correction data.