Street Light Fixture S/P Ratio Distribution
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Solution Overview
Problem
Existing street light fixtures for mesopic lighting conditions do not effectively address the need for uniform illumination along a road axis, as they fail to vary the Scotopic/Photopic (S/P) ratio in a direction parallel to the axis, leading to uneven perceived light intensity.
Innovation Solution
A street light fixture comprising multiple light sources with varying S/P ratios, arranged to emit a light bundle that changes S/P ratio from the central to peripheral areas, with higher ratios in peripheral areas to compensate for lower light intensity, creating a more uniform illumination experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high S/P ratio light sources (cyan range) are used to improve mesopic vision, then vision acuity under mesopic lighting conditions is improved, but the light appears unpleasant to humans
Solution Approach 1:
The patent applies local quality by assigning different S/P ratio characteristics to different spatial regions of the light bundle. The central region uses lower S/P ratio light (white or orange) for pleasant perception, while peripheral regions use higher S/P ratio light (cyan) for improved mesopic vision acuity. This spatial differentiation resolves the contradiction by providing both pleasant overall perception and enhanced vision where needed.
2Illumination intensity
If uniform light intensity is provided across the roadway, then illumination uniformity is improved, but light intensity in peripheral areas is insufficient for mesopic vision
Solution Approach 1:
The patent changes the S/P ratio parameter spatially across the light bundle to compensate for the inverse square law衰减 of light intensity. By increasing the S/P ratio in peripheral regions where intensity naturally decreases, the patent maintains effective mesopic vision acuity across the entire roadway without requiring uniform high intensity illumination everywhere.
3Illumination intensity
If street lights are placed closer together to improve perceived uniformity, then illumination uniformity is improved, but installation and operational costs increase
Solution Approach 1:
The patent reduces the number of required light fixtures by implementing local quality variations within each fixture's light bundle. By concentrating higher S/P ratio light in peripheral regions, each fixture effectively illuminates a larger area with adequate mesopic vision quality, reducing the need for additional fixtures while maintaining perceived uniformity.
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 provides improved perceived uniformity of light intensity along the road axis by increasing vision acuity in peripheral areas, reducing the need for closer street lighting placement and associated costs, while maintaining energy efficiency.
Implementation Method 1
a plurality of light sources of at least two types, each type being characterized by a Scotopic/Photopic ratio
Implementation Method 2
the rods in the eye's retina make an important contribution to overall vision. The rods are most sensitive to light in the scotopic range of the spectrum
Data Source
AI summary
A light fixture is disclosed having a plurality of light sources belonging to at least two types emitting light of different S/P ratio. The light sources are placed in the light fixture so that the light fixture, when in use, emits a light bundle having varying S/P ratios within the bundle. In an embodiment the light bundle has a central area with low S/P ratio, and peripheral areas having higher S/P ratio. The S/P ratio in the peripheral areas can be as high as 5 or even higher. In an alternate embodiment the light bundle has a central area with relatively S/P ratio, and peripheral areas having lower S/P ratio. The S/P ratio in the peripheral areas can be as low as 2 or even lower.The light fixtures are particularly suitable for outdoor lighting, for example street lighting.