Rod-Shaped Light Guide Thermal Conductor for Image Sensor Uniformity
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Solution Overview
Problem
In image reading devices using contact image sensor units, local heat applied to the light guide can cause distortion, leading to uneven light distribution and potential image issues like black lines, even when dust or dirt is not present, due to incorrect shading correction.
Innovation Solution
An image sensor unit design that includes a thermal conductor covering the reflection surface of the light guide to maintain uniform temperature distribution, preventing distortion and ensuring consistent light distribution by using a rod-shaped light guide with a reflection surface and an emission surface, along with a thermal conductor and an image forming element to form images on a photoelectric conversion element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light guide is used in a CIS unit, then light distribution uniformity is improved, but local heat causes distortion of the light guide
Solution Approach 1:
A thermal conductor is introduced as an intermediary component between the light guide and the heat source (sensor substrate). This thermal conductor acts as a heat dissipation mediator that conducts heat away from the light guide, preventing local heat accumulation and distortion while maintaining the light guide's structural integrity and optical performance.
Solution Approach 2:
The patent replaces the mechanical/structural approach to heat management (relying on passive heat dissipation or thermal insulation) with a thermal conduction-based solution. By using a thermal conductor that actively conducts heat away from the light guide, the system substitutes passive mechanical heat management with an active thermal conduction mechanism, effectively controlling heat distribution.
2Measurement precision
If shading correction is performed based on distorted light guide, then dust and dirt are detected, but image unevenness occurs due to incorrect adjustment
Solution Approach 1:
The thermal conductor provides preliminary heat dissipation action before heat can cause distortion of the light guide. By continuously conducting heat away from the light guide, the system prevents the distortion that would otherwise lead to incorrect shading correction and image unevenness, thereby protecting image quality reliability in advance.
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 solution maintains uniform light distribution across the image sensor unit, preventing image unevenness and ensuring accurate shading correction, even when local heat is applied, thereby reducing the occurrence of image defects like black lines.
Implementation Method 1
a thermal conductor provided so as to cover the reflection surface of the light guide
Implementation Method 2
a rod-shaped light guide including a reflection surface that reflects light from the light source
Implementation Method 3
an emission surface provided on a side opposite to the reflection surface that emits light reflected by the reflection surface to the document
Data Source
AI summary
An image sensor unit includes: a light source that illuminates a document; a rod-shaped light guide including a reflection surface that reflects light from the light source and an emission surface provided on a side opposite to the reflection surface that emits light reflected by the reflection surface to the document; a thermal conductor provided so as to cover the reflection surface of the light guide; an image forming element that forms an image of reflected light from the document on a photoelectric conversion element; a sensor substrate on which the photoelectric conversion element is mounted; and a frame including a locator for mounting the light guide.