Inclined Light Guide for Image Reader Illumination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional light irradiators, such as those using LEDs, face challenges in achieving high light use efficiency without deteriorating captured images, particularly when the light source is positioned apart from the reading optical axis to prevent direct reflecting light from causing image defects like white spots, smear, or flare.
Innovation Solution
A light irradiator design featuring a light guide with a long shape in the main scanning direction and a specific cross-sectional shape, where the emission surface is inclined relative to the reading optical axis, ensuring that the divided cross-sectional areas near and far from the axis satisfy certain relations, optimizing light distribution and reducing light wastage while maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the light source is positioned apart from the reading optical axis to prevent direct reflecting light from causing image defects, then image quality is improved, but light use efficiency deteriorates
Solution Approach 1:
The light guide is positioned at an inclination angle of 10 to 45 degrees relative to the reading optical axis, introducing a spatial dimension change that allows light to reach the document surface from an optimized angle. This dimensional adjustment enables the light guide to illuminate the document effectively while avoiding direct reflection into the reader, thus resolving the contradiction between image quality and light use efficiency
Solution Approach 2:
The patent optimizes specific parameters including the inclination angle of the light guide (10-45 degrees), the cross-sectional area ratio (S1/S2 between 0.5-2.0), and the position of the light guide relative to the optical axis. These parameter changes enable the system to achieve both high light use efficiency (31% improvement) and good image quality by finding the optimal balance point
2Illumination intensity
If high brightness LED is used to achieve high document surface illuminance, then illuminance is improved, but device complexity increases
Solution Approach 1:
The light guide features a non-uniform cross-sectional area design where the area varies along the length of the light guide. This local quality variation allows different sections of the light guide to optimize light distribution to different areas of the document surface, achieving high illuminance without requiring excessively bright LEDs that would increase device complexity
Solution Approach 2:
The light guide cross-sectional area is designed to change dynamically along its length, with the area at position x given by S(x) where S1(x)≥S2(x) and S1(L)＞S2(L). This dynamic variation in cross-sectional area allows the light guide to adaptively distribute light intensity, achieving high document surface illuminance while maintaining manageable device complexity
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 enhances light use efficiency by approximately 31% compared to conventional systems, ensuring high illuminance on the document surface while preventing image deterioration, thus improving the overall performance of image readers and scanners.
Implementation Method 1
two side surfaces reflecting light from the incident surface to the emission surface
Data Source
AI summary
A light irradiator includes a light source and a light guide to guide a light flux from the light source to an illumination area. The light guide has an incident surface, an emission surface and two side surfaces. The emission surface is located apart from a reading optical axis with an inclination relative to the reading optical axis. The following relations are satisfied:S1(x)≧S2(x)S1(L)>S2(L)wherein S1 represents a divided cross-sectional area near the reading optical axis and S2 represents a divided cross-sectional area far from the reading optical axis when a virtual cross-sectional area S parallel to the incident surface of the light guide is divided by a plane passing the center of the incident surface, formed by a direction perpendicular thereto and the incident surface and the main scanning direction; S (x) represents a virtual cross-sectional area distant from the incident surface of the light guide by x; L is a distance from the incident surface to the emission surface; and 0≦x<L.