Top-View and Side-View LED Illumination for Document Scanners
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Solution Overview
Problem
Conventional image reading apparatuses using LEDs face challenges in achieving linear light distribution and efficient illumination of a cubic area without shading, as LEDs have strong directivity and require complex setups or result in diffused light and reduced efficiency when trying to illuminate from both sides.
Innovation Solution
An image reading apparatus employing a combination of top-view and side-view LEDs on a single substrate, with a light guide for converging light and a reflection plate for balanced illumination from both sides, allowing efficient illumination of a document from both sides and reducing light quantity unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LEDs are disposed at both sides of scanning direction to illuminate object from both sides, then illumination of cubic area without shading is improved, but device complexity and cost increase due to large substrate and complicated wiring
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement of LEDs on a substrate to a three-dimensional configuration where LEDs are mounted on the side surface of the housing. This vertical mounting approach eliminates the need for a large substrate and complex wiring, while still achieving illumination from both sides of the scanning direction through strategic placement of LEDs at different heights and angles.
2Illumination intensity
If convergent member is provided between LED and object to reflect light, then illumination from both sides is improved, but light efficiency decreases due to diffused light and stray light occurs
Solution Approach 1:
The patent removes the convergent member from the optical path between the LED and the object. Instead of using a convergent member to redirect light, the invention relies on the direct emission characteristics of LEDs mounted on the housing side surface, eliminating the source of diffused light and stray light that causes energy loss.
3Ease of manufacture
If LED is used as light source, then cost reduction is achieved compared to fluorescent lamp, but illumination from both sides becomes difficult due to strong directivity of LED
Solution Approach 1:
The patent exploits the directional emission特性 of LEDs dynamically by mounting them on the side surface of the housing rather than on a planar substrate. This allows the light to reach the object from multiple angles and positions, effectively using the LED's strong directivity to achieve comprehensive illumination without requiring multiple LEDs or complex optical systems.
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 configuration enables efficient illumination of a cubic area without shading, reduces costs by simplifying wiring, and maintains high light usage efficiency while suppressing stray light and temperature rise.
Implementation Method 1
the light emitted from an LED must be changed to have linear light distribution by use of a light guide member
Implementation Method 2
only one fluorescent lamp and a reflection mirror that are located opposite each other are provided
Data Source
AI summary
An image reading apparatus for reading an image of a document optically by illuminating a document with light emitted from a plurality of light emitting elements arranged linearly and by reading light reflected from the document. The image reading apparatus has a first light emitting element for emitting light in a first direction, a second light emitting element for emitting light in a second direction and one substrate for supporting the first light emitting element and the second light emitting element thereon.