Light Guide Curved Optical Surfaces Illumination Uniformity
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Solution Overview
Problem
Conventional image reading apparatuses experience uneven illuminance on the original surface due to the arrangement of light emitting elements and toric surface arrays, leading to issues like unevenness due to light emitting points and pitch bright points, especially when reading glossy originals.
Innovation Solution
The image reading apparatus incorporates a light guide with a deflection surface featuring a first curved optical surface array and an emission surface with a second curved optical surface array, both arranged in the longitudinal direction, which diffuse light to reduce unevenness. The second pitch of the toric surfaces is set larger than the first pitch to minimize edge chipping and enhance surface texturing, resulting in a more uniform illuminance distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If light emitting elements are arranged at predetermined intervals, then the illumination device can be constructed with discrete light sources, but uneven illuminance occurs on the original surface
Solution Approach 1:
The light guide is divided into multiple light guide units, each containing a subset of light emitting elements. This segmentation allows the illumination system to maintain discrete light sources while reducing the impact of individual element positioning on overall uniformity, as each unit contributes to a distributed illumination pattern
Solution Approach 2:
The invention introduces a two-dimensional array of light emitting elements arranged in both main scanning and sub-scanning directions, rather than simply linear arrangement. This dimensional expansion creates a more distributed light source pattern that reduces unevenness on the original surface
2Illumination intensity
If a toric surface array is formed on the emission surface, then unevenness due to light emitting points is reduced, but pitch bright points occur on read images
Solution Approach 1:
Different regions of the emission surface are assigned different functions: some areas have toric surfaces for diffusing light to reduce unevenness, while other areas have flat surfaces that prevent the formation of pitch bright points. This local differentiation allows the system to achieve uniform illumination without introducing harmful artifacts
Solution Approach 2:
The invention converts what would normally be harmful pitch bright points into beneficial flat illumination areas. By strategically placing flat emission surfaces in specific locations, the system eliminates the pitch bright point problem while maintaining the uniformity benefits of toric surfaces in other regions
3Illumination intensity
If multiple toric surface arrays are used, then unevenness due to light emitting points is reduced, but device complexity increases
Solution Approach 1:
Multiple light guide units are merged into a single integrated illumination device. Each unit contains light emitting elements and emission surfaces (both toric and flat), and their combined operation achieves uniform illumination without requiring separate complex systems for each function
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 effectively reduces both unevenness due to light emitting points and pitch bright points, achieving a more uniform illuminance on the original surface, thereby improving image reading quality.
Implementation Method 1
The light beam 107 propagates while repeating total reflection on an inner wall of a light guide portion 504 of the light guide 502
Implementation Method 2
a deflection surface configured to deflect the light emitted from the plurality of light emitting elements to direct the light toward the original
Implementation Method 3
an emission surface configured to emit the light deflected by the deflection surface toward the original
Data Source
AI summary
An image reading apparatus including: an illumination device configured to illuminate an original; and a solid-state image sensor configured to receive and convert a reflected light from the original into an image signal, wherein the illumination device includes: a plurality of light emitting elements; and a light guide configured to guide light emitted from the light emitting elements toward the original, wherein the light guide includes: a deflection surface configured to deflect the light emitted from the light emitting elements to direct the light toward the original; and an emission surface configured to emit the light deflected by the deflection surface toward the original, wherein the deflection surface has a plurality of first curved optical surfaces provided side by side in a longitudinal direction of the light guide, and wherein the emission surface has a plurality of second curved optical surfaces provided side by side in the longitudinal direction.