Light Guide Positioning Structure for Stable Image Reading
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Solution Overview
Problem
The positioning misalignment between a light guide member and a supporting member in an image reading apparatus can lead to insufficient illuminating light amount and image blurring due to warpage and adhesive peeling, resulting from variations in LED and light guide member positions.
Innovation Solution
The image reading apparatus incorporates a light guide unit with projections and concave portions that allow for precise alignment and attachment to a supporting member, using projections and concave shapes to maintain positional accuracy even with warpage, ensuring consistent light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the light guide member is attached to the supporting member using adhesive only, then the attachment is simple, but warpage causes adhesive peeling and positional misalignment
Solution Approach 1:
The supporting member is divided into multiple opposing portions (first opposing portion and second opposing portion) that independently engage with corresponding end portions of the light guide member. This segmentation allows each portion to independently maintain positioning, preventing cumulative error and adhesive peeling while keeping the overall structure simple.
Solution Approach 2:
The light guide member is nested between the first and second opposing portions of the supporting member, with each end portion inserted into a corresponding opposing portion. This nesting structure provides mechanical constraint that prevents warpage-induced misalignment while maintaining a compact, simple attachment design.
2Manufacturing precision
If the light guide member is made rigid to prevent warpage, then positional accuracy is maintained, but the light guide member cannot accommodate manufacturing tolerances and LED variations
Solution Approach 1:
The supporting member is designed with opposing portions that can accommodate dimensional variations and warpage within a certain range. The engagement structure allows for parameter changes in the light guide member's position and orientation while maintaining functional accuracy, thus adapting to manufacturing tolerances and LED variations.
Solution Approach 2:
The opposing portions are positioned asymmetrically along the light guide member's length, with each opposing portion tailored to engage with specific end portions. This asymmetric arrangement allows differential accommodation of warpage and variations at different locations, maintaining overall positional accuracy despite local deviations.
3Strength
If multiple adhesive portions are used to prevent peeling, then attachment strength is improved, but the complexity of the attachment structure increases
Solution Approach 1:
Instead of using a continuous adhesive layer that requires multiple reinforcement portions, the attachment is segmented into discrete engagement points at the end portions. This segmentation concentrates the bonding strength at critical locations while keeping the overall structure simple and avoiding the need for multiple complex reinforcement elements.
4Measurement precision
If the contacting surfaces are made large to improve positioning accuracy, then alignment precision is improved, but the light guide member becomes more prone to warpage
Solution Approach 1:
The contacting surfaces are segmented into multiple discrete engagement areas at different end portions rather than one large continuous surface. This segmentation provides sufficient alignment precision through distributed contact points while reducing the overall warpage-prone area, as smaller segmented surfaces are more stable than large continuous surfaces.
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 design reduces positional misalignment and maintains consistent illuminating light amount, preventing image blurring and ensuring high-quality image reading performance.
Implementation Method 1
a transparent light guide member made of resin, etc. is provided to the illuminating device. This light guide member guides a light, which is emitted from the plurality of LEDs and diffused in a circular shape, toward the original surface along a main scanning direction
Implementation Method 2
a configuration which enables positioning between the light guide member and a supporting member with high accuracy by making contacting surfaces, which are provided to both end portions in a longitudinal direction of the light guide member, respectively, contact and adhere to contacting surfaces of the supporting member
Data Source
AI summary
An image reading apparatus includes a light guide unit provided with a light guide member, a reading portion, and a supporting member including a supporting portion to support the light guide unit, first and second opposing portions opposing first and second ends of the light guide member in a longitudinal direction, respectively. One of the first end and the first opposing portion includes a first projection projecting in the longitudinal direction, and the other includes a first concave portion of which a width is wider than that of the first projection and into which the first projection is inserted with a gap. One of the second end and the second opposing portion includes a second projection, and the other includes a second concave portion of which width is wider than that of the second projection and into which the second projection is inserted with a gap.