Asymmetric LED Lens Rectangular Illumination
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Solution Overview
Problem
Imaging-based bar code readers face challenges in achieving uniform illumination across a rectangular field of view, leading to inefficient light usage and potential misidentification of bar codes due to non-uniform light patterns.
Innovation Solution
The use of a light emitting diode (LED) in conjunction with a specially designed lens having a non-rotationally symmetric polynomial surface, which redirects light to create a uniform illumination pattern across a rectangular field of view, optimizing light efficiency and reducing stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional lens is used to focus LED light, then the illumination pattern becomes more concentrated, but the pattern remains round and non-uniform across the rectangular FOV, wasting light and reducing energy efficiency
Solution Approach 1:
The patent applies asymmetry by designing a lens with non-rotationally symmetric surfaces (aspheric and/or free-form) that are specifically shaped to match the rectangular field of view. This asymmetric lens geometry transforms the round illumination pattern from a conventional spherical lens into a uniform rectangular pattern, ensuring even light distribution across the entire FOV while minimizing light waste in directional applications.
Solution Approach 2:
The patent employs parameter changes by optimizing the aspheric and free-form surface parameters of the lens to control light distribution. By adjusting these geometric parameters, the lens achieves precise control over the illumination pattern, transforming it from a round shape to a uniform rectangular pattern that matches the sensor array geometry and maximizes light utilization efficiency.
2Productivity
If a conventional lens is used to illuminate the bar code, then the light is focused, but stray light is generated that provides no useful function and reduces energy efficiency
Solution Approach 1:
The asymmetric lens design with non-rotationally symmetric surfaces is specifically engineered to eliminate stray light by directing all light uniformly across the rectangular field of view. This asymmetric geometry ensures that no light is wasted in directions outside the FOV, thereby improving energy efficiency without compromising reading accuracy.
Solution Approach 2:
By optimizing the aspheric and free-form surface parameters of the lens, the system achieves precise control over light propagation. These parameter adjustments ensure that light is focused exactly where needed (across the rectangular FOV) while eliminating stray light, thus improving both productivity and energy efficiency simultaneously.
3Area of stationary object
If the LED generates a wide illumination pattern without a lens, then the entire area is covered, but light is wasted and the pattern is not uniform enough for accurate bar code reading
Solution Approach 1:
The asymmetric lens with non-rotationally symmetric surfaces is designed to transform the wide but non-uniform illumination pattern into a uniform rectangular pattern. This asymmetric geometry ensures that light is distributed evenly across the entire FOV while maintaining compact beam control, eliminating the need for excessive light spread and reducing energy waste.
Solution Approach 2:
The optimization of aspheric and free-form surface parameters enables precise control over the illumination pattern. By adjusting these parameters, the lens achieves uniform light distribution across the rectangular FOV while maintaining efficient beam confinement, thus covering the required area without wasting light in unnecessary directions.
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 ensures efficient and uniform illumination of the bar code, enhancing the ability to accurately capture and decode bar codes by minimizing light wastage and maintaining high energy efficiency.
Implementation Method 1
an illumination system having a light source such as a light emitting diode (LED) for illuminating a target within a field of view defined by the optical system
Implementation Method 2
This lens bends the light to create a field of view with good efficiency and having uniformity across the field of view
Data Source
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AI summary
The disclosed bar code reader has an imaging system that includes a light monitoring pixel array and a focusing lens that is fixed with respect to the pixel array for transmitting an image of the target object onto the pixel array. The bar code reader also includes an illumination system for illuminating the target having a light source for emitting a diverging light outwardly from a light source location and a lens for bending the light including a first surface facing the light source and a second surface facing the target for bending the light emitted by the light source to more uniformly illuminate a rectangular, generally planar region at the target within the barcode reader's field of view.