Non-uniform Illumination for Imaging Vignetting
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Solution Overview
Problem
Conventional scanning devices suffer from vignetting, where corner areas of the imaging surface appear darker due to the longer distance light from these areas must travel to reach the lens, leading to reduced illumination and image quality.
Innovation Solution
A system with light sources arranged around the perimeter of the imaging surface to non-uniformly illuminate corner areas more brightly than non-corner areas, achieving a photo response non-uniformity (PRNU) level of between 10% and 50%, using a lens with a field of view angle of 50 degrees or greater and a focal length between 200 mm and 500 mm to ensure uniform illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the imaging unit is placed close to the imaging surface to reduce device size, then the device size is reduced, but the corner areas appear darker due to vignetting
Solution Approach 1:
The patent applies local quality by implementing non-uniform illumination where corner areas receive higher illumination intensity compared to central areas. This is achieved by positioning light sources at specific locations and angles to compensate for the vignetting effect, ensuring that corner regions are adequately illuminated while maintaining close proximity of the imaging unit to the imaging surface.
2Illumination intensity
If light sources are positioned to illuminate corner areas more brightly, then corner illumination is improved, but the illumination becomes non-uniform
Solution Approach 1:
The patent applies parameter changes by carefully controlling the illumination parameters including the position, angle, and intensity of light sources. By adjusting these parameters, the system achieves non-uniform illumination patterns that compensate for the optical vignetting effect, ensuring uniform overall illumination across the imaging surface while maintaining the compact configuration.
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 effectively addresses vignetting by ensuring corner areas are illuminated to the same intensity as non-corner areas, resulting in improved image quality with reduced darkness at the edges and enhanced photo response uniformity.
Implementation Method 1
a lens positioned on the plurality of light sources and operative to diverge light from the light source to illuminate the corner areas of the imaging surface sufficiently to achieve a photo response non-uniformity (PRNU) level of between 10% and 50% at the imaging member
Data Source
AI summary
An imaging device having an imaging unit for illuminating and capturing an original positioned on the imaging surface. The imaging surface is illuminated by an illumination system including a plurality of light sources that non-uniformly illuminates the imaging surface such that the corner areas of imaging surface is illuminated more than the non-corner areas of the imaging surface. In one embodiment the light sources are arranged around the perimeter of the imaging surface. In an alternate embodiment the light sources are located outside the field of view of a lens of the image capturing unit.