Diffuse Illumination Grid for Handheld Symbology Readers
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Solution Overview
Problem
Existing handheld symbology readers face challenges with illumination systems that are either too large for portable use or result in uneven lighting, particularly when trying to illuminate irregular surfaces or surfaces with two-dimensional textures, as they require a central aperture and limited light sources, leading to dimly lit regions and spotting effects.
Innovation Solution
A compact illumination system for handheld symbology readers featuring a grid assembly with a transparent plate and a light source array mounted coaxially with the imager's optical axis, using a grid with transparent spaces between elements to minimize the reader's size and ensure uniform, diffuse illumination, combined with a dark field light pipe and optional diffuse illumination sources to address varying surface types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a central aperture and limited light sources are used in the illumination system, then the reader can be made more compact, but the illumination becomes uneven with dimly lit regions and spotting effects
Solution Approach 1:
The illumination system is segmented into multiple independent light sources arranged in an array, each contributing to the overall illumination. This segmentation allows light to be distributed more evenly across the field of view, eliminating the spotting effects and dim regions that occur with limited light sources, while still maintaining a compact form factor through the organized array structure.
Solution Approach 2:
Multiple light sources are merged into a single integrated illumination system that works collectively to provide uniform diffuse illumination. The combination of multiple LEDs in an array, coupled with the grid assembly and light pipe, creates a unified illumination field that covers the entire viewing area evenly, resolving the contradiction between compact size and illumination uniformity.
2Reliability
If diffuse illumination is provided for irregular surfaces, then image acquisition is enhanced, but the illumination system becomes too large for portable handheld use
Solution Approach 1:
The illumination components are nested within each other to minimize overall system volume. The grid assembly is positioned within the light pipe structure, and multiple light sources are arranged concentrically or in compact arrays. This nesting allows the portable reader to provide enhanced diffuse illumination for irregular surfaces while maintaining a handheld form factor.
Solution Approach 2:
The illumination system utilizes three-dimensional spatial arrangement of light sources and optical elements to achieve effective diffuse illumination in a compact footprint. By arranging LEDs in multiple layers or radial patterns and using the light pipe to distribute light volumetrically, the system provides comprehensive illumination coverage without increasing the external dimensions beyond handheld limits.
3Volume of moving object
If a grid assembly with transparent plate is used to minimize reader size, then portability is improved, but the grid elements become visible in the acquired image
Solution Approach 1:
The grid assembly is designed with locally optimized properties where the transparent plate and grid elements have specific geometric characteristics that minimize their visibility in the final image. The grid pattern is configured to fall outside the critical focus plane or use refractive index matching, allowing the compact structure to be maintained while preserving image quality by making the grid elements effectively invisible in the acquired imagery.
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 provides a compact, uniformly illuminated surface area with reduced visibility of the grid elements in the acquired image, minimizing dimly lit regions and enhancing image acquisition on both regular and irregular surfaces, while maintaining the ability to switch between bright and dark field illumination as needed.
Implementation Method 1
a light source array adapted to project light radially into a light pipe
Implementation Method 2
a grid assembly having a transparent plate with an imager-facing side and a subject-facing side, in which the imager-facing side includes an applied pattern of reflecting spots or elements adapted, to project a highly diffuse and uniform illumination on a subject
Implementation Method 3
an inner light pipe with a distal beveled edge (typically a 45-degree bevel) that bends light from the sources at a 90-degree angle radially into the perimeter edge of the transparent plate of the grid assembly
Data Source
AI summary
An illumination system and method for use in a handheld symbology reader that employs a grid of reflecting elements applied to a transparent plate adapted to project a highly diffuse and uniform illumination on a subject. The grid defines a geometry with a large number of transparent spaces between grid elements through which an image of the subject can be acquired. A light source array is configured to project light into the grid at a right angle via a light pipe having a distal beveled edge or side projecting light sources. Another light source may be employed to illuminate second light pipe with a chamfered edge to create low-angle illumination.