Uniform Illumination for Point-of-Transaction Imagers
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Solution Overview
Problem
Point-of-transaction workstations with imager-based readers face challenges in uniformly illuminating fields of view, leading to bright areas that can blind the imager and dim areas that reduce imaging performance, especially at varying working distances.
Innovation Solution
The solution involves an apparatus with a solid-state imager and optical system that splits the field of view into intersecting subfields, each illuminated by a dedicated illumination assembly with light-modifying elements to ensure uniform light intensity across the subfields, using LEDs and lenses or baffles to condition the illumination light for consistent intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple imagers with intersecting fields of view are used to provide full coverage scan zone, then imaging coverage and reliability are improved, but device complexity and cost increase
Solution Approach 1:
The patent divides the field of view of a single imager into multiple subfields using optical beam splitters and mirrors, creating multiple viewing angles from one imager. This segmentation allows the system to achieve coverage equivalent to multiple imagers while using only one, thereby reducing complexity while maintaining reliability
Solution Approach 2:
A single imager is made to perform multiple functions by capturing images from different angles and positions through the split subfields. This multi-functional approach replaces what would traditionally require multiple specialized imagers, reducing system complexity while maintaining comprehensive imaging capability
2Measurement precision
If illumination light intensity is increased to improve imaging in far field, then imaging performance at distance is improved, but bright areas blind the imager and cause saturation
Solution Approach 1:
The patent applies different illumination intensities to different subfields based on their specific requirements. Near-field subfields receive lower illumination intensity to prevent saturation, while far-field subfields receive higher intensity to ensure adequate lighting. This localized quality adjustment optimizes imaging precision without causing harmful saturation effects
Solution Approach 2:
The illumination intensity for each subfield is dynamically adjusted based on the working distance and imaging requirements. The system can adaptively modify the brightness of individual illumination assemblies to match the actual imaging needs, preventing both saturation in bright areas and insufficient lighting in dim areas
3Productivity
If illumination light is emitted at all times to ensure continuous imaging capability, then imaging availability is improved, but power consumption increases and operational lifetime decreases
Solution Approach 1:
The illumination assemblies are activated periodically only when needed, such as when a product is detected in the scan zone or when imaging is actually required. This periodic activation pattern maintains imaging availability when necessary while dramatically reducing power consumption and extending the operational lifetime of the illumination sources
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 approach provides sufficient and uniform illumination in both near and far fields, enabling successful and rapid imaging of indicia across a wide dynamic range of working distances, improving imaging performance and reducing system complexity.
Implementation Method 1
an optical system supported by the housing and operative for splitting the field of view of the imager into a plurality of intersecting subfields of view
Implementation Method 2
a plurality of light-modifying elements, one for each illumination assembly. Each light-modifying element is operative for conditioning the illumination light from the plurality of illumination light sources to be generally uniform in light intensity over the at least one illuminated subfield of view
Implementation Method 3
Each illumination assembly has a plurality of illumination light sources for illuminating a respective subfield of view with illumination light
Implementation Method 4
The image sensors detected the return illumination light reflected and/or scattered from the indicia
Data Source
AI summary
Indicia are imaged at a workstation having windows arranged in intersecting planes. The workstation also has solid-state imagers with fields of view that are split into intersecting subfields that look out through the windows, as well as illumination assemblies each having multiple light sources that illuminate each subfield with illumination light over an illumination field that overlaps a respective subfield. Light-modifying elements, such as lenses or baffles that are radially offset from the multiple light sources, condition the illumination light from the multiple light sources to be generally uniform in light intensity over at least one illuminated subfield.