Light Guide Plate Uniform Illumination via Extraction and Merging
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Solution Overview
Problem
Existing image reading devices using LEDs face challenges with light distribution, particularly in illuminating only the intended document region, leading to inaccurate reproduction of solid black portions and increased energy consumption due to the need for higher LED intensity and complex mounting methods that hinder total reflection and increase manufacturing costs.
Innovation Solution
A light projecting device comprising a base board with a line of light-emitting elements, a light guiding member, a holding member, a cover, and a positioning member that positions the light guiding member between the holding member and cover, ensuring even light distribution and reducing the need for screw holes, which simplifies manufacturing and maintains light intensity across the document surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple LEDs are arranged in an array and obliquely mounted to increase light intensity, then the light intensity is improved, but the illumination distribution becomes uncontrolled and light spills outside the irradiation region causing inaccurate image reproduction
Solution Approach 1:
A light guide plate is introduced as an intermediary component between the LED array and the document surface. The light guide plate receives light from the LEDs and distributes it uniformly across the irradiation region through internal reflection and diffusion, preventing light spill while maintaining high illumination intensity where needed.
Solution Approach 2:
The light guide plate has non-uniform optical properties with different regions designed to perform different functions: some regions facilitate total internal reflection to redirect light, while other regions allow controlled light extraction. This local differentiation enables precise control over illumination distribution, ensuring light is concentrated in the irradiation region and prevented from spilling outside.
2Reliability
If screw holes are formed on the light guide plate to secure mounting components, then the mounting reliability is improved, but light loss occurs due to disruption of total reflection at the screw hole locations
Solution Approach 1:
The mounting function is extracted from the light guide plate itself. Instead of forming screw holes in the light guide plate, separate mounting structures are provided on the housing that hold the light guide plate in place. This extraction eliminates the need for screw holes through the light guide plate, preventing light loss while maintaining secure mounting.
3Stability of the object's composition
If the light guide plate is secured with multiple screws to ensure stable positioning, then the positioning stability is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The mounting function is merged into the housing structure itself. The housing includes integrated mounting features such as recesses, clips, or interference-fit structures that directly hold the light guide plate in place without requiring separate screws or fasteners. This merging simplifies the overall structure, reduces part count, and maintains positioning stability.
4Illumination intensity
If LED intensity is increased to compensate for light attenuation over long distance, then the light intensity at the image pickup device is improved, but the energy consumption increases
Solution Approach 1:
The light guide plate creates a continuous optical path from the LED array to the document surface, maintaining light intensity throughout the illumination region. By using total internal reflection and controlled light extraction, the system maintains efficient light transmission without requiring excessive LED intensity, thereby reducing energy consumption while ensuring sufficient illumination at the image pickup device.
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 solution provides efficient and uniform light distribution across the document, preventing light loss and maintaining light intensity, while reducing manufacturing complexity and costs by eliminating the need for screw holes and allowing for easier assembly and heat dissipation.
Implementation Method 1
The light guiding member guides light projected from the light-emitting elements onto a target irradiation region of a target object
Data Source
AI summary
A light projecting device includes a base board, a light guiding member, a holding member, a cover, and a positioning member. A plurality of light-emitting elements are arranged in a line on the base board in a main scan direction. The light guiding member faces a radiation surface of the light-emitting elements and guides light projected from the light-emitting elements to an irradiation region of an illuminated object. The holding member holds the base board. The cover covers the base board and the light guiding member. The positioning member positions the light guiding member on the holding member. The holding member and the cover sandwich the light guiding member positioned by the positioning member. The light projecting device includes the holding member, the light guiding member, the base board, and the cover as a single unit which is detachably mountable relative to a chassis of the light projecting device.