Uniform Illumination Pattern for Imaging Reader
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Solution Overview
Problem
Existing solid-state imaging systems face challenges in generating a uniform distributed illumination pattern, leading to optical aberrations, non-uniform intensity, and reduced reading performance, especially at far ranges and in dimly lit environments, due to the use of single LEDs and cylindrical lenses, which also result in poor ergonomic design and increased operator fatigue.
Innovation Solution
The implementation of a plurality of LEDs with an optical component comprising a first lens portion for intercepting and aligning illumination light at an acute angle, and a second lens portion for collimating it, along with an aperture stop to limit vertical height, generates a substantially uniform distributed illumination pattern, improving coupling efficiency and reducing optical aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single LED and single cylindrical lens are used to generate distributed illumination pattern, then device complexity is reduced, but illumination uniformity deteriorates with non-uniform intensity distribution and optical aberrations
Solution Approach 1:
The illumination assembly is segmented into multiple LED sources (at least two LEDs) arranged in a linear array, with each LED contributing to different portions of the illumination pattern. This segmentation allows for better control of the overall illumination distribution, reducing the non-uniformity that occurs with a single LED while maintaining manageable device complexity.
Solution Approach 2:
Different regions of the illumination pattern are addressed by different LEDs or portions of the optical system. The patent employs optical elements with varying properties across the illumination path to locally adjust intensity distribution, ensuring more uniform illumination across the entire pattern while accounting for the natural falloff characteristics of individual LEDs.
2Manufacturing precision
If aperture stop is added to improve sharpness of illumination pattern, then illumination pattern height is reduced, but coupling efficiency deteriorates and illumination intensity decreases
Solution Approach 1:
The patent employs aspherical optical surfaces that dynamically adjust the light path geometry to optimize both sharpness and coupling efficiency. The aspherical surfaces are designed to redirect light rays in a manner that maintains pattern definition while preserving more light throughput compared to traditional spherical surfaces with aperture stops.
Solution Approach 2:
The optical design changes the geometric parameters of the illumination path by using aspherical surfaces with specific curvature variations. This parameter optimization allows the system to achieve sharp pattern edges without the need for aggressive aperture stopping that would otherwise be required with spherical surfaces, thereby maintaining higher coupling efficiency.
3Illumination intensity
If pair of spaced-apart LEDs and pair of cylindrical lenses are used to increase illumination brightness, then illumination intensity is improved, but device complexity increases and optical aberrations worsen
Solution Approach 1:
Multiple LED sources are merged into a coordinated linear array configuration, where the individual light outputs are combined through a unified optical system. This merging approach increases overall illumination brightness while avoiding the complexity of multiple separate optical assemblies, as the patent uses a integrated lens structure that serves the entire LED array.
Solution Approach 2:
The optical elements in the patent are designed with multi-functionality to handle illumination from multiple LED sources simultaneously. The aspherical surfaces and optical train are configured to perform multiple functions: collimating light from different LED positions, shaping the overall illumination pattern, and reducing aberrations across the entire array, thereby managing complexity while achieving high brightness.
4Adaptability or versatility
If field of view is widened for near range reading, then near range reading capability is improved, but far range resolution deteriorates and illumination intensity decreases
Solution Approach 1:
The patent employs an anamorphic optical system that treats the horizontal and vertical dimensions differently. The illumination and imaging optics are designed with different focal ratios in orthogonal directions, allowing a wide field of view horizontally for near-range adaptability while maintaining higher vertical resolution for far-range reading accuracy. This dimensional differentiation resolves the trade-off between field of view and resolution.
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 solution enhances reading performance by providing a uniform illumination pattern with improved light throughput and ergonomics, reducing operator fatigue and maintaining readability at far ranges without sacrificing resolution.
Implementation Method 1
an optical component including a first lens portion for intercepting, bending and aligning the emitted illumination light to generate the substantially uniform distributed illumination pattern of light along the symbol in a scan direction
Implementation Method 2
a second lens portion for collimating the aligned illumination light in a transverse direction generally perpendicular to the scan direction to generate the substantially uniform distributed illumination pattern of light on the symbol
Implementation Method 3
An aperture stop is positioned between each LED and the optical component, preferably in close proximity to the LED, for limiting the vertical extent or height of the emitted illumination light incident on the optical component
Implementation Method 4
The light source includes at least one light emitting diode (LED) and, preferably, a plurality of LEDs
Data Source
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Figure 5
AI summary
A substantially uniform distributed illumination pattern of light is generated on and along a symbol to be read by image capture. A solid-state imager is mounted on a tilted printed circuit board in a tilted handle of an ergonomic reader. An imaging lens assembly captures return light over a field of view from the symbol along an imaging axis, and projects the captured return light onto the imager. An illumination light source is mounted on the board for emitting illumination light at an acute angle of inclination relative to the imaging axis. An optical component includes a first lens portion with a polynomial incident surface for intercepting, bending and aligning the emitted illumination light to generate the pattern in a scan direction along the symbol, and a second lens portion with a toroidal or cylindrical aspherical surface for collimating the aligned illumination light to generate the pattern in a transverse direction.