Parabolic Mirror Lighting Unit for Uniform Illumination
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Solution Overview
Problem
Image scanners face challenges in achieving uniform illumination with large lighting depth when scanning documents with uneven surfaces, such as book manuscripts or wrinkled paper, due to fluctuations in brightness along the lighting depth direction, which existing lighting devices struggle to address effectively.
Innovation Solution
A lighting unit comprising a light source array in the main scanning direction, a parabolic mirror with a cylindrical paraboloid shape clipped by an axial plane, and a housing that supports the light source and mirror, where the light source is positioned at the focal position of the parabolic mirror, ensuring parallel light emission and efficient illumination across the document surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple reflective surfaces are used to guide light from point light sources to the document surface, then lighting coverage is improved, but uniformity of illumination across the lighting depth direction deteriorates
Solution Approach 1:
The patent employs a parabolic mirror with a specific curved surface geometry to reflect and guide light from the light source array. The parabolic curvature is designed to redirect light rays at precise angles, ensuring that illumination remains uniform across the entire lighting depth direction while covering a large document area. This curved reflective surface replaces multiple flat reflective surfaces, achieving both coverage and uniformity.
2Illumination intensity
If a parabolic mirror with light source at focal position is used to achieve parallel light emission, then illumination uniformity is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple light-emitting elements into a single light source array positioned at the focal position of the parabolic mirror. This merging approach allows the entire array to function as one unified light source, simplifying the optical system while achieving parallel light emission and uniform illumination across the document surface.
Solution Approach 2:
The parabolic mirror serves multiple functions simultaneously: it reflects light from the focal position, redirects rays to create parallel illumination, and maintains uniformity across the lighting depth direction. This multi-functionality reduces the need for additional optical components, thereby decreasing overall device complexity.
3Adaptability or versatility
If lighting depth is increased to accommodate uneven document surfaces, then adaptability to different documents is improved, but brightness distribution uniformity deteriorates
Solution Approach 1:
The parabolic mirror's curved surface is specifically designed to maintain consistent illumination intensity across varying depths. The geometric properties of the parabola ensure that light rays reflected at different angles maintain uniform intensity distribution, allowing the system to accommodate uneven document surfaces while preserving brightness uniformity throughout the lighting depth direction.
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 provides efficient and uniform lighting with minimal changes in light quantity along the lighting depth direction, enabling clear imaging of documents regardless of distance from the document stand, and allows for compact and cost-effective implementation.
Implementation Method 1
a parabolic mirror that is adapted to reflect light emitted from the light source on a document surface
Data Source
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AI summary
A lighting unit (2) is provided with: LED arrays (220) in which light-emitting elements are positioned in an array in a main scanning direction; cylindrical parabolic mirrors (20) that project light emitted from the LED arrays (220) on an illumination region of an illuminated item; and a housing that houses or holds the LED arrays (220) and the cylindrical parabolic mirrors (20). Each cylindrical parabolic mirror (20) forms a shape in which a cylindrical paraboloid having curvature with respect to a sub-scanning direction (12) has been clipped by an axial plane that is perpendicular to the vertex of the cylindrical paraboloid in the main scanning direction (11). The LED arrays (220) are positioned so as to include the focal position of the cylindrical paraboloid in the light-emitting region, the central axis in the light-emitting direction being perpendicular to the axial plane.