Document Illumination System Using Reflective Element Array
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Solution Overview
Problem
Existing document illuminating systems for image readers face challenges in achieving even luminance distribution and preventing dark lines in images, particularly due to increased size and thickness, which affects the quality of scanned documents and requires a solution for efficient illumination with minimal thickness and cost-effective manufacturing.
Innovation Solution
A document illuminating system with a plurality of light emitting elements arranged in an array, utilizing a reflective element with planar reflective portions to oppositely illuminate the document read area, ensuring even luminance distribution and reducing system thickness, while using white LEDs for efficient and cost-effective illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective mirror is used to guide light at large divergent angles to the document, then illumination performance is improved, but the thickness and size of the illumination system increase
Solution Approach 1:
The patent transitions from using a reflective mirror (two-dimensional surface reflection) to a light guide plate (three-dimensional volumetric light guidance). The light guide plate utilizes internal reflection and light diffusion within its volume to guide light from LEDs to the document, achieving better illumination performance while maintaining a thinner profile since light is guided through the thickness of the plate rather than requiring additional space for mirror positioning and adjustment.
2Volume of stationary object
If the distance from light source to document is decreased to reduce reader size, then system size is reduced, but even luminance distribution cannot be achieved
Solution Approach 1:
The light guide plate serves as an intermediary element between the LED light source and the document. It receives light from the LEDs and distributes it uniformly across the document surface through internal light diffusion and scattering mechanisms. This intermediary structure enables the system to maintain a compact size while achieving even luminance distribution, as the light guide plate decouples the direct distance relationship between the LED and document.
3Device complexity
If illumination is provided from a single direction, then system complexity is reduced, but dark lines occur in images of uneven documents
Solution Approach 1:
The light guide plate incorporates localized variations in its optical properties, such as diffusers, reflectors, or micro-structures at different positions and orientations. These local variations enable the plate to redirect light from a single LED source to illuminate the document from multiple effective directions, preventing dark lines while maintaining relatively simple system configuration.
4Illumination intensity
If a special covering element is used to cover LED emission face to improve illumination, then illumination performance is improved, but manufacture cost increases
Solution Approach 1:
The light guide plate utilizes changes in optical parameters such as refractive index, absorption coefficient, or scattering properties at different locations within the plate. By incorporating optical diffusers, reflectors, or absorbing materials with varying properties, the system achieves improved illumination performance using conventional LEDs without requiring special covering elements, thereby maintaining cost-effectiveness.
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 system achieves even luminance distribution across the document read area, preventing dark lines and ensuring high image quality with a compact design, suitable for both monochrome and color image scanning, and is cost-effective due to the use of white LEDs and planar reflective elements.
Implementation Method 1
a reflective element which guides light emitted from the plurality of light emitting elements to a document read area
Implementation Method 2
highly bright LEDs are now available... emission spectrum of a white LED covers a visible range of wavelength bands
Data Source
AI summary
A document illuminating system includes a plurality of light emitting elements arranged in an array, a reflective element which guides light emitted from the light emitting elements to a document read area of a certain width and length. The reflective element includes first to third reflective portions. The second reflective portion includes one or more planar reflective faces and is disposed so that the reflective faces reflect light from the light emitting elements to one or both of the first and third reflective portions without other reflective elements. The first and third reflective portions each include one or more planar reflective faces and are disposed so that their reflective faces oppositely illuminate the document read area together by reflecting light from one or both of the light emitting elements and the second reflective portion to the document read area without other reflective elements.