LED Illumination Uniformity via Optical Axis Orientation
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Solution Overview
Problem
LEDs do not approximate well as a point source, leading to non-uniform far-field illumination, which is exacerbated by internal structural characteristics and requires the use of additional optics like reflectors, mirrors, and lenses, resulting in light intensity losses and manufacturing complexities.
Innovation Solution
A light source comprising multiple LEDs mounted on a substrate with their optical axes oriented towards a central point, each with a unique preferential direction, eliminating the need for specific optics by leveraging the inherent spatial radiation patterns to achieve uniform irradiance distribution on a selected surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If additional optics such as reflectors, lenses, and condensers are used to achieve uniform illumination, then illumination uniformity is improved, but light intensity losses increase and device complexity increases
Solution Approach 1:
The patent extracts and eliminates the additional optics (reflectors, lenses, condensers) from the illumination system. By using multiple LEDs with specifically oriented optical axes that all converge on a common central point, the system achieves uniform illumination without requiring external optical components, thereby removing the source of light intensity losses associated with these components
Solution Approach 2:
The patent divides the single light source into multiple LED elements arranged in a specific configuration. Each LED contributes to the overall illumination pattern, and by orienting their optical axes toward a common central point, they collectively produce uniform illumination on the target surface without needing additional optics
2Illumination intensity
If additional optics such as reflectors, lenses, and condensers are used to achieve uniform illumination, then illumination uniformity is improved, but device complexity increases
Solution Approach 1:
The patent removes the complex optical train (reflectors, lenses, condensers) from the system design. The uniform illumination is achieved purely through the geometric arrangement and orientation of multiple LED optical axes, significantly simplifying the device structure and manufacturing process
Solution Approach 2:
By segmenting the light source into multiple LEDs with controlled orientations, the system achieves complex illumination uniformity through simple geometric arrangement rather than complex optical components, reducing device complexity while maintaining illumination quality
3Speed
If focused LEDs with parabolic reflectors are used to achieve small opening angles, then beam directionality is improved, but far-field illumination uniformity deteriorates due to very long depths of field
Solution Approach 1:
The patent uses multiple LED segments with their optical axes oriented toward a common central point. This segmentation approach creates overlapping radiation patterns that fill in the depth of field issues associated with focused LEDs, achieving both directionality and far-field uniformity
Solution Approach 2:
The patent merges the radiation patterns of multiple LEDs oriented toward a common point. This combination of multiple directional beams creates a unified illumination pattern that maintains directionality while achieving uniform far-field illumination through the superposition of overlapping cones
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 simplifies manufacturing, reduces weight, and achieves uniform illumination without external optics, effectively mitigating non-uniformities and light intensity losses, suitable for applications in Time of Flight cameras and 3D imaging.
Implementation Method 1
each of the plurality of LEDs having an optical axis and generating a radiation pattern propagating along the optical axis
Implementation Method 2
the preferential direction is an orientation of the LED's spatial radiation pattern which is linked to physical and geometrical properties of the LED
Data Source
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AI summary
A light source for illuminating a selected surface, the light source comprising a plurality of Light Emitting Diodes (LED) mounted on a substrate; each of the plurality of LEDs having an optical axis and generating a radiation pattern propagating along the optical axis. The plurality of LEDs are arranged so that each optical axis is oriented substantially towards a determined far-field central point; and the plurality of LEDs provide a predetermined irradiance distribution on the selected surface. Each of the radiation patterns defines a preferential direction; and each of the plurality of LEDs is arranged so that the preferential direction of each of the plurality of LEDs is unique.