Light Guide Diffuse Reflection Pattern for Uniform Illuminance
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Solution Overview
Problem
Conventional lighting apparatuses for image reading devices suffer from uneven illuminance distribution along the longitudinal direction of the light guide body, leading to inconsistencies in image density and reduced image quality, especially when the original document surface is not flat.
Innovation Solution
A lighting apparatus with a rod-shaped light guide body featuring a first diffuse reflection pattern with a discontinuous pattern intermittently along the longitudinal direction and a second diffuse reflection pattern to reduce variations in light quantity, combined with a light source at the end of the light guide body to enhance uniformity of illuminance distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a discontinuous diffuse reflection pattern is applied to the light guide body surface, then light quantity near end portions is suppressed to uniformize output light intensity, but uneven illuminance occurs on the original document read surface along the longitudinal direction
Solution Approach 1:
The light guide body is divided into multiple sections along its longitudinal direction, with each section having a specific diffuse reflection pattern (continuous or discontinuous) tailored to its position. This segmentation allows different parts of the light guide body to control light distribution independently, achieving both end portion suppression and overall illuminance uniformity.
Solution Approach 2:
Different regions of the light guide body are assigned different diffuse reflection pattern characteristics. The end portions use discontinuous patterns for light suppression, while middle portions use continuous patterns for uniform illumination. This local differentiation resolves the contradiction between suppressing end light and maintaining overall illuminance uniformity.
2Illumination intensity
If a concavo-convex portion for light diffusion is provided near the end portion close to the light source, then the irradiation peak near the light source is resolved, but a considerable quantity of output light scatters outside the reading region in the sub-scanning direction
Solution Approach 1:
A diffuse reflection pattern is applied specifically to the region near the light source end portion, creating local light diffusion exactly where the irradiation peak occurs. This localized approach uniformizes illumination near the source without causing widespread scattering outside the reading region, as the pattern is confined to the specific problem area.
3Manufacturing precision
If the original document surface is not flat, then reading accuracy decreases, but conventional lighting apparatus cannot maintain uniform illuminance distribution
Solution Approach 1:
The light guide body is segmented into multiple sections with different diffuse reflection patterns along its longitudinal direction. This segmentation enables precise control of light distribution to compensate for illuminance variations caused by non-flat document surfaces, maintaining both uniform illuminance and reliable image quality.
Solution Approach 2:
The diffuse reflection pattern parameters (continuity, density, distribution) are varied along the longitudinal direction of the light guide body to adapt to different illuminance requirements. This parameter modification allows the lighting system to maintain uniform illuminance distribution even when the document surface is not flat.
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
The solution significantly improves the uniformity of illuminance distribution across the original document surface, reducing inconsistencies in image density and maintaining high image quality even when the document surface is not flat.
Implementation Method 1
a light guide body (14) having a first diffuse reflection pattern (35) for performing diffuse reflection on the light including a discontinuous pattern formed intermittently at predetermined intervals along the longitudinal direction
Implementation Method 2
for a period during which light incident from the end face of the light guide body propagates toward an end portion on the opposite side, while repeating total reflection inside the light guide body
Data Source
AI summary
To suppress unevenness in intensity distribution of output light in a longitudinal direction of a light guide body, a lighting apparatus includes a rod-shaped light guide body, and light source units provided in end faces of the body, where the light guide body includes first and second reflecting surfaces that perform diffuse reflection on light input from the light source, and a light output surface that outputs reflected light from both of the reflecting surfaces to the outside. The first reflecting surface includes a first diffuse reflection pattern having discontinuous pattern portions provided near the end faces in the longitudinal direction of the light guide body and a continuous pattern portion in the center portion, and the second reflecting surface includes a second diffuse reflection pattern to reduce a ripple in the longitudinal direction of a quantity of the light reflected from the first diffuse reflection pattern and output.