Optical Illumination System for Shadow-Free Document Reading
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Solution Overview
Problem
Existing image reading apparatuses face challenges in illuminating raised portions of documents, such as open books, resulting in shadows due to unidirectional illumination, and suffer from low light use efficiency and increased costs when attempting to provide illumination from two directions.
Innovation Solution
The apparatus employs a light concentration optical system with reflective members and an optical member, dividing the illumination area into two regions by a virtual plane perpendicular to the document surface, ensuring illumination from both directions without compromising light concentration, using a light-emitting diode (LED) source and reflective plates to optimize light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If illumination is provided from one direction using LED array, then light concentration is achieved, but shadow formation occurs on raised document portions
Solution Approach 1:
The illumination system is segmented into multiple LED arrays positioned at different locations, with each array providing illumination from a different direction. This segmentation allows simultaneous achievement of light concentration and shadow prevention by dividing the illumination function across multiple directional sources.
Solution Approach 2:
Different regions of the document surface receive illumination with different characteristics - raised portions receive additional illumination from opposing directions to prevent shadows, while flat portions receive concentrated illumination for high intensity. This local differentiation of illumination quality resolves the contradiction between concentration and shadow prevention.
2Object-affected harmful factors
If opposed reflective plates are disposed in second area, then illumination from two directions is attempted, but light use efficiency is severely decreased
Solution Approach 1:
The patent merges the functions of direct LED illumination and reflective plate illumination into a unified system. LEDs and reflective plates are positioned and coordinated to work together, with reflective plates directing LED light to create additional illumination paths without requiring separate light sources, thereby maintaining light use efficiency while achieving shadow prevention.
Solution Approach 2:
Reflective plates serve as intermediaries that redirect light from LED sources to illuminate shadow-prone areas. Instead of using opposing reflective plates as independent light sources (which would halve the light budget), the reflective plates mediate by redirecting existing LED light to create the effect of multi-directional illumination while preserving overall light use efficiency.
3Object-affected harmful factors
If number of LEDs is increased for two-directional illumination, then shadow prevention is improved, but device complexity and cost increase
Solution Approach 1:
The reflective plates serve multiple functions: they redirect light to prevent shadows, they concentrate light from LED sources, and they help define the optical path geometry. This multi-functionality allows the system to achieve shadow prevention without requiring proportionally more LEDs, thereby controlling device complexity while improving illumination uniformity.
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 prevents shadow formation and achieves high light use efficiency while maintaining concentrated illumination, even when documents are raised, and allows for a downsized apparatus with improved illumination uniformity and intensity.
Implementation Method 1
an optical illumination system which leads light emitted from a light source to a reading target area with a plurality of reflective members and an optical member having a light concentration effect
Implementation Method 2
an optical member having a light concentration effect
Data Source
AI summary
An image reading apparatus includes a light source that illuminates light on an original document surface, an optical illumination system that leads the light emitted from the light source towards a reading target region, an imaging optical system that images the light reflected from the original document surface, the image optical system, and a sensor provided in an imaging part of the imaging optical system, for reading an image of an original document on the original document surface. The optical illumination system comprises an optical member and a plurality of reflective members, and an area for disposing the members of the illumination optical system is divided into two areas by a virtual plane perpendicular to the original document surface, parallel to the length direction, and passing through the area for disposing the members, and at least one of the reflective members is disposed in each of the areas.