Split LED Array for Accurate Document Length Detection
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Solution Overview
Problem
Conventional image reader units face challenges in accurately identifying the length of documents with leading ends having solid images, leading to erroneous detection due to reduced light reflection, and require lengthy processes that may not complete within the half-open period of the document cover, resulting in inefficient and sometimes incorrect length identification.
Innovation Solution
The image reader unit employs a movable exposure unit with a split LED array that selectively activates only the necessary LED elements for document length identification in the main scanning direction, moving in the sub-scanning direction to obtain reflected light quantities, allowing for precise length determination based on received light intensity without unnecessary light exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all LED elements are activated for document length identification, then the light coverage is sufficient, but the process time increases and may not complete within the half-open period
Solution Approach 1:
The LED array is divided into multiple independently controllable LED elements arranged in the main scanning direction. Instead of activating all LED elements simultaneously, the controller selectively activates only the necessary subset of LED elements based on the detected document position and required measurement accuracy, thereby reducing the total lighting time while maintaining sufficient light coverage for accurate length identification within the half-open period
Solution Approach 2:
The system activates only the minimum necessary number of LED elements required for accurate document length identification rather than all available elements. This partial activation approach reduces the cumulative lighting duration and allows the light-receiving process to complete within the document cover half-open period, preventing time overflow while maintaining measurement reliability
2Area of stationary object
If LED elements are positioned over solid images at the leading end, then light coverage is maximized, but light reflection is reduced causing erroneous detection
Solution Approach 1:
The system implements spatially selective LED activation where different LED elements are activated based on their position relative to the document. When a solid image is detected at the leading end, the controller avoids activating LED elements positioned over the solid image area, as these would receive insufficient reflected light. Instead, LED elements positioned over lighter or reflective areas are activated, ensuring adequate light reflection for accurate length measurement while maintaining appropriate light coverage
Solution Approach 2:
The system performs preliminary detection of the document leading end characteristics before activating the LED elements. By first identifying whether a solid image exists at the leading end and determining the document position, the controller can pre-select which LED elements to activate, avoiding those that would cause erroneous detection due to insufficient light reflection from solid images
3Stability of the object's composition
If the document cover remains closed during length identification, then the document is properly pressed, but light reflection from the pressing surface causes detection errors
Solution Approach 1:
The system dynamically adjusts the document cover state during the length identification process. The controller opens the document cover to a controlled extent (half-open position) during the lighting and light-receiving process, preventing light reflection from the pressing surface that would occur when the cover is fully closed. This dynamic state change ensures both sufficient document stability and accurate length detection by eliminating false light reflection signals
4Measurement precision
If the lighting and light-receiving process is extended to ensure complete measurement, then accuracy is improved, but the process exceeds the half-open period causing inefficiency
Solution Approach 1:
The system implements periodic or pulsed LED element activation rather than continuous lighting. The controller activates specific LED elements in timed intervals during the document cover half-open period, synchronizing the lighting pulses with the available measurement window. This periodic action ensures complete and accurate length measurement within the constrained time period while maximizing operational efficiency by avoiding unnecessary extended processing
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 prevents erroneous length detection by moving the LED elements away from solid images and reduces the time required for the lighting and light-receiving process, ensuring accurate length identification even with large documents, and avoids errors caused by light reflection from the document pressing surface.
Implementation Method 1
an optical mount including an LED array that includes a plurality of LED elements disposed in a main scanning direction along a surface of the document platen
Implementation Method 2
receiving reflected light from the surface of the document
Implementation Method 3
causes a charge-coupled device (CCD) used as an image sensor to receive the reflected light and scan the image of the document
Data Source
AI summary
An image reader unit includes a platen on which to place a document; a light source including a plurality of split light sources to emit light beams toward a surface of the document; a movable exposure unit moving in a sub-scanning direction while obtaining reflected light reflected from the surface of the document; an image sensor to scan an image of the document by receiving the reflected light; and a reader processor to identify a length of the document in the main scanning direction based on a received light quantity from the image sensor obtained by activating fewer than all of the plurality of split light sources necessary for identifying the length of the document in the main scanning direction while moving the movable exposure unit in the sub-scanning direction.