Light Guide Member Positioning for Uniform Illumination
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Solution Overview
Problem
In image reading devices, the use of LEDs as light sources can lead to non-uniform illuminance distribution due to the small light emitting surface, and the thermal expansion of light guide members can cause deformation, making it challenging to achieve high accuracy and cost-effective assembly.
Innovation Solution
A light irradiation device with a light guide member featuring an engagement lug structure at one end and a fastening structure at the other end, allowing for precise positioning and securement, even when the light guide member is deformed, and incorporating a light diffusion surface to prevent glare and improve illuminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light guide member is used to guide light from an LED point source, then illuminance distribution uniformity is improved, but thermal expansion causes deformation and assembly precision deteriorates
Solution Approach 1:
The light guide member is pre-heated before assembly to anticipate thermal expansion. By heating the light guide member in advance to a temperature close to its operating temperature, the expansion occurs before assembly, allowing components to be assembled in their expanded state. This preliminary action eliminates deformation after assembly and maintains both illuminance uniformity and assembly precision.
Solution Approach 2:
The temperature parameter of the light guide member is changed before assembly. By controlling the temperature at which the light guide member is assembled (heating it to reduce thermal stress), the physical state of the material is altered to prevent subsequent deformation. This parameter change ensures the light guide member maintains its shape and positioning accuracy during operation.
2Productivity
If injection molding is used to manufacture the light guide member, then cost and mass productivity are improved, but assembly alignment and positional accuracy deteriorate
Solution Approach 1:
A holding member is introduced as an intermediary component between the injection-molded light guide member and the housing. The holding member features precise positioning structures (such as recesses or guide features) that align the light guide member accurately during assembly. This intermediary element compensates for the lack of precision in injection molding while maintaining the cost-effectiveness and productivity of the molding process.
3Stability of the object's composition
If the light guide member is secured tightly to prevent deformation, then positional stability is improved, but light utilization efficiency and assembly cost deteriorate
Solution Approach 1:
The light guide member is pre-heated to expand it before assembly, creating a interference fit that provides positional stability without requiring additional fastening elements. The thermal expansion allows the member to be inserted and then contracts upon cooling to create a secure, deformation-free connection. This approach maintains light utilization efficiency by avoiding extra components while ensuring positional stability.
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 high positional accuracy and cost-effective assembly of the light guide member, while enhancing light utilization efficiency and preventing thermal deformation, resulting in improved image quality and reduced operational costs.
Implementation Method 1
The light guide member includes a transparent material to guide light from the light source
Implementation Method 2
a light guide member including a transparent material, such as a transparent resin including polymethyl methacrylate (PMMA), is used
Implementation Method 3
The securing structure in one end portion is an engagement lug structure protruding to penetrate into a through-hole of the holding member, including a lug on a leading end, and engaging the holding member. The securing structure on another end portion is a fastening structure having a fastening hole penetrated with a fastening member and being secured to the holding member with the fastening member.
Data Source
AI summary
A light irradiation device includes a light source, a light guide member, and a holding member. The light guide member includes an incident surface, an exit surface, and a held surface. The incident surface has an elongated shape in a main scanning direction and faces a light emitting surface of the light source. The light guide member includes a securing structure in each of both end portions in the main scanning direction, which are out of a light guide area of the light guide member. The securing structure in one end portion is an engagement lug structure protruding to penetrate into a through-hole of the holding member, including a lug on a leading end, and engaging the holding member. The securing structure on another end portion is a fastening structure having a fastening hole penetrated with a fastening member and being secured to the holding member with the fastening member.