LED Array Positioning for Uniform Illumination in Image Scanners
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Solution Overview
Problem
Conventional image reading apparatuses with LEDs arranged in a straight line suffer from uneven illumination due to variable distances between LEDs and light leading members, leading to non-uniform document illumination along the main scanning direction.
Innovation Solution
Incorporating positioning means such as holding parts, contact standard surfaces, and insertion concave parts in the light leading member to ensure consistent gaps between LEDs and the light leading member, aligning the LED array substrate with the longitudinal direction of the light leading member, and using a photoelectric conversion element to receive reflection light from the document.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the distance between LEDs and light leading member is not constant, then the structure is simpler to manufacture, but the document illumination becomes non-uniform along the main scanning direction
Solution Approach 1:
The patent introduces a positioning member as an intermediary component between the LED array substrate and the light leading member. This positioning member includes positioning protrusions that engage with positioning recesses, serving as a mediator to establish and maintain a constant gap without requiring complex direct coupling mechanisms between the LED substrate and light leading member.
Solution Approach 2:
The patent applies local quality by providing positioning protrusions at specific locations on the positioning member corresponding to the positions of individual LEDs. Each positioning protrusion locally ensures the correct gap distance for its associated LED, allowing the system to achieve uniform illumination through localized positioning features rather than requiring uniform structural complexity throughout the entire assembly.
2Manufacturing precision
If positioning means is added to ensure constant gap between LEDs and light leading member, then uniform illumination is achieved, but device complexity increases
Solution Approach 1:
The patent merges the positioning function with the support function by integrating the positioning member into the existing structural framework. The positioning member is combined with the holder that supports the LED array substrate, so that a single component performs both positioning and support functions, reducing the need for separate positioning mechanisms and minimizing overall device complexity.
Solution Approach 2:
The positioning protrusions and positioning recesses are designed to automatically align and engage during assembly, allowing the positioning function to be self-executing without requiring additional adjustment mechanisms or complex control systems. The structural features themselves provide the positioning capability, making the system self-servicing in terms of maintaining the constant gap.
3Ease of manufacture
If LEDs are arranged in a straight line with variable distances to light leading member, then manufacturing is easier, but illuminance ripple occurs on the document
Solution Approach 1:
The positioning member acts as an intermediary that decouples the simplicity of straight-line LED arrangement from the requirement of constant gap maintenance. The LED array substrate can be manufactured with LEDs in a straight line using simple techniques, while the positioning member with its positioning protrusions ensures that each LED maintains the correct constant distance from the light leading member, eliminating illuminance ripple without complicating the LED arrangement manufacturing process.
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 ensures uniform illumination of the document along the main scanning direction by uniformly incident light beams from the LEDs, improving image reading quality and reducing maintenance costs by allowing for easy replacement of faulty LEDs.
Implementation Method 1
a light leading member made of transparent resin, glass, or the like is arranged between the object to be lighted and the point light sources. The light leading member leads light irradiating from the point light sources and diffusing in a circle toward a surface of the document along a main scanning direction
Implementation Method 2
a CCD (photoelectric conversion element) via a mirror 106 or lens (not shown) so that image information corresponding to the image of the document D can be obtained
Data Source
AI summary
An image reading apparatus, including point light sources, arranged in a straight line state, configured to output light to light a document, and a light leading member, positioned in front in a light outputting direction of the light output from the point light sources, configured to receive the light incident on a surface of the light leading member, and to lead the received light so as to irradiate along a main scanning direction toward the document. The light leading member includes a positioning unit configured to make a gap between one of the point light sources arranged in a line state and the light leading member the same as a gap between another of the point light sources and the light leading member, and to make an arrangement direction of the point light sources be positioned along a longitudinal direction of the light leading member.