LED Illumination Device with Angled Axis and Conic Reflector
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Solution Overview
Problem
Conventional LED illumination devices create hot spots and non-uniform illumination patterns due to the Cos 3θ effect, which results in high illuminance ratios exceeding 10:1, making it difficult to achieve uniform illumination in applications like high-bay, low-bay, and street lighting.
Innovation Solution
The LED central axis is positioned away from the target area, and a reflector with segmented, curved, or conic sections is used to redirect light, avoiding hot spots by diverting light from the central axis to specific angles, thereby creating a more uniform illumination pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the LED central axis is aligned with the light fixture optical axis pointing directly toward the target area, then the illuminance directly in front of the fixture is maximized, but a hot spot is created resulting in non-uniform illumination pattern
Solution Approach 1:
The LED central axis is deliberately misaligned with the light fixture optical axis, creating an asymmetric configuration. The LED is positioned at an angle (e.g., 30-60 degrees) relative to the optical axis, which prevents direct light from creating a hot spot on the target surface while still providing adequate illumination through the reflector's light redirecting capability.
Solution Approach 2:
Instead of aligning the LED to maximize direct illuminance (conventional approach), the invention inverts the approach by intentionally misaligning the LED. This inversion prevents the hot spot formation by ensuring that the LED's central axis does not point directly at the target area, thereby achieving uniform illumination as the primary goal.
2Area of stationary object
If a reflector is used to redirect light and increase illuminance at various areas, then the illumination coverage is improved, but the hot spot directly in front of the LED cannot be reduced
Solution Approach 1:
The reflector is designed with asymmetric geometry relative to the LED position and orientation. The reflector's shape and positioning are optimized to capture and redirect light from the misaligned LED source, distributing it evenly across the target area while preventing concentration of light that would create hot spots.
Solution Approach 2:
Different portions of the reflector are designed with different geometric properties to handle light from different regions of the LED emission pattern. The reflector creates localized illumination zones with appropriate intensity levels, ensuring that no single area receives excessive light while maintaining overall coverage.
3Adaptability or versatility
If the LED emits light in a hemispherical pattern, then the light distribution is naturally wide, but the Cos 3θ effect causes rapid drop-off in illuminance at higher angles
Solution Approach 1:
The reflector employs curved surfaces with specific geometric profiles (e.g., parabolic, elliptical, or free-form curves) to redirect light rays. These curved surfaces are designed to intercept light at various angles from the LED's hemispherical emission and redirect them to achieve a more uniform angular distribution on the target surface, compensating for the Cos 3θ drop-off.
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 reduces or eliminates hot spots and achieves a highly uniform illumination pattern with a maximum to minimum illuminance ratio of 10:1 or less, ensuring effective light distribution in various applications.
Implementation Method 1
A reflector is used and a reflector portion may reflect light and direct only an appropriate amount of light directly in front of the fixture
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
An LED (light emitting diode) illumination device that can generate a uniform light output illumination pattern. The illumination device includes an array of LEDs, each having a LED central axis. The LED central axis of the array of LEDs is angled approximately toward a central point. The illumination source includes a reflector with a conic or conic-like shape. The reflector wraps around the front of the LED to redirect the light emitted along a LED central axis.