LED Array Illumination Positioning via Mechanical Intermediaries
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Solution Overview
Problem
Image reading apparatuses using LED arrays face issues with non-uniform illumination due to misalignment between light guide members and LEDs, leading to potential damage and detachment during assembly and usage, as well as insufficient luminance.
Innovation Solution
Incorporating a positioning unit with a frame that fixes the light guide member and array substrate, ensuring the incident surface of the light guide member is in proximity or contact with the LEDs, preventing pressing forces and ensuring uniform illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the light guide member is pressed onto the LEDs during assembly operations to determine positional relationship, then the positional relationship between the light guide member and LEDs is determined, but the LEDs may be damaged or mounting detachment may be produced due to pressing force
Solution Approach 1:
A positioning protrusion on the light guide member fits into a positioning groove on the array substrate to establish the positional relationship between the light guide member and LEDs without requiring pressing force. The positioning protrusion and groove act as mechanical intermediaries that define position through geometric constraint rather than force application.
Solution Approach 2:
The patent replaces the mechanical pressing system with a positioning protrusion-groove system. Instead of using frictional force from pressing to maintain positional relationship, the invention uses geometric fitting where the positioning protrusion fits into the positioning groove, eliminating the need for continuous pressing force and preventing LED damage.
2Reliability
If the incident surface of the light guide member is parallel to the LED array but the interval is excessively large, then the LEDs are protected from damage, but the luminance on the document surface becomes insufficient
Solution Approach 1:
The positioning protrusion and groove are designed in advance to establish the optimal interval between the light guide member and LEDs during assembly. This preliminary positioning ensures that the light guide member is positioned close enough to the LEDs to receive sufficient light for adequate luminance, while maintaining a safe distance to prevent damage from pressing force.
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 maintains the LEDs' integrity during assembly and usage, preventing damage and detachment, while ensuring uniform luminance distribution on the document surface.
Implementation Method 1
a light guide member formed from a translucent resin, glass, or the like is disposed for example between a plurality of LEDs and a document to guide light emitted from the LEDs onto the document surface
Implementation Method 2
a plurality of low cost, durable, and high luminance point light sources such as a LED (light-emitting diode) is arrayed at a predetermined interval along a main scanning direction
Data Source
AI summary
An image reading apparatus includes an array substrate in which a plurality of point light sources is mounted along the main scanning direction, a light guide member disposed on a surface of the array substrate that mounts the plurality of point light sources, and guiding light from the plurality of point light sources to the document surface, a frame for fixing the light guide member and the array substrate, a positioning unit that determines the positional relationship of the frame with the light guide member and the array substrate in a configuration in which the incident surface of the light guide member is in proximity to or in contact with the plurality of point light sources; and an image reading unit that uses reflected light when illuminating light from the plurality of point light sources through the light guide member onto the document surface to thereby read the document image.