LED Board Alignment in Image Reading Apparatus
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Solution Overview
Problem
Deformations in LED boards, such as waviness and bending, can lead to non-uniform light distribution in image reading apparatuses, resulting in suboptimal image quality and color stability due to misalignment between the exit and entrance surfaces of the light guide and LED board.
Innovation Solution
The image reading apparatus incorporates a light guide unit with a support member that includes projecting portions between holding slots to secure and correct the LED board, ensuring uniform light emission by regulating the LED board's position and preventing deviations during assembly and thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light guide is used to guide light from LEDs to the document, then light can be directed along the main scanning direction, but deformations in the LED board cause the exit surface of the LED to deviate from the entrance surface of the light guide, resulting in non-uniform light distribution
Solution Approach 1:
The patent applies preliminary action by providing holding slots and support members with projecting portions that pre-position and constrain the LED board in the correct alignment with the light guide before thermal expansion or deformation can occur. This preventive positioning ensures the exit surface of the LED remains aligned with the entrance surface of the light guide, maintaining uniform light distribution despite manufacturing variations or thermal effects.
2Reliability
If the LED board is held in a fixed position during assembly, then alignment can be achieved, but thermal expansion and deformation may cause misalignment between the LED exit surface and light guide entrance surface
Solution Approach 1:
The patent applies parameter changes by designing the support member with a specific thermal expansion coefficient that differs from the LED board material. This allows the support member to compensate for thermal expansion and deformation of the LED board, maintaining the alignment between the LED exit surface and light guide entrance surface across varying temperature conditions. The holding slots and projecting portions work together to provide constrained positioning that accounts for dimensional changes.
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 consistent light distribution along the main scanning direction, enhancing image quality and color stability by maintaining the LED board's alignment and correcting potential deformations, thereby achieving high-quality read images.
Implementation Method 1
a light guide guides light emitted from the plurality of LEDs disposed on an LED board to the document. This light guide guides the light, which is emitted from the plurality of LEDs and diffused in a circular shape, toward a document surface
Implementation Method 2
an image reading unit configured to read image information by performing photoelectric conversion on reflected light reflected by a sheet which has received light emitted from the light guide portion
Data Source
AI summary
An image reading apparatus includes a circuit board on which a plurality of light sources are disposed in a longitudinal direction, a light guide portion including a first holding portion configured to hold the circuit board, and a second holding portion configured to hold the circuit board, a support member configured to support the light guide portion, and an image reading unit configured to read image information by performing photoelectric conversion on reflected light reflected by a sheet which has received light emitted from the light guide portion. The support member includes a projecting portion disposed between the first holding portion and the second holding portion in the longitudinal direction, the projecting portion facing and projecting toward the circuit board held by the first holding portion and the second holding portion.