Optical Element Stray Light Control via Total Internal Reflection
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Solution Overview
Problem
Conventional optical elements in luminaires, such as street lights and flood lights, face challenges in controlling stray light emissions, which can reach sensitive areas outside the intended target area, affecting lighting efficiency and nuisance reduction.
Innovation Solution
An optical element made of a transparent piece with a base plate acting as a light guide and a lens section, featuring a cavity with a flared circumferential redirection surface that utilizes total internal reflection to redirect stray light back into the optical element, preventing it from exiting in undesired directions, thus maintaining the primary beam's integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a base plate is used to carry lenses in an optical element, then the structural support and lens mounting are achieved, but stray light propagates through the base plate to reach other lenses and sensitive areas
Solution Approach 1:
The patent applies total internal reflection at the base plate-lens interface to redirect stray light that would otherwise propagate harmfully through the base plate. By utilizing the optical properties of the lens-material interface, the design converts the potentially harmful stray light into beneficial redirected light that exits within the primary beam limit, thus converting a harmful effect into a beneficial one without adding complex blocking structures
Solution Approach 2:
The patent extracts and redirects stray light paths from the base plate by designing lenses with specific angular characteristics that cause stray light to undergo total internal reflection at the base plate interface. This separates the stray light from its harmful propagation path through the base plate to sensitive areas, effectively removing it from the problematic optical path
2Object-generated harmful factors
If internal louvers or masks are added to block stray light, then stray light control is improved, but the primary beam and desired lighting characteristic are affected
Solution Approach 1:
Instead of using physical blockers like louvers or masks that would interrupt the primary beam, the patent utilizes total internal reflection to redirect stray light. This optical approach converts stray light into useful light that exits within the primary beam limit, avoiding the need for blocking structures that would compromise the desired lighting characteristics
Solution Approach 2:
The patent introduces the base plate-lens interface as an intermediary optical element that selectively redirects stray light through total internal reflection. This intermediary mechanism differentiates between stray light (which is redirected) and primary beam light (which passes through), avoiding the need for direct blocking that would affect both types of light
3Object-generated harmful factors
If external accessories like visors are added to block stray light, then stray light reaching sensitive areas is reduced, but device complexity, dimensions, weight and cost increase
Solution Approach 1:
The patent merges the stray light control function directly into the base plate and lens assembly by utilizing total internal reflection at their interface. This integration eliminates the need for separate external accessories like visors, thereby reducing device complexity, dimensions, weight and cost while maintaining effective stray light control
Solution Approach 2:
The optical element performs its own stray light control function through the inherent optical properties of the base plate-lens interface. The system is self-sufficient in controlling stray light through total internal reflection, eliminating the need for additional external components and simplifying the overall structure
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
Effectively reduces stray light influence on sensitive areas, enhancing lighting efficiency and minimizing nuisance by redirecting stray light within the desired primary beam limits without additional components or costs.
Implementation Method 1
When viewed along the geometric plane, an angle α of the redirection surface, with respect to the geometric plane, at any part along its circumference is defined such that light propagating through the base plate by internal total reflection (TIR; e.g. single or multiple TIR) towards the cavity is redirected at the redirection surface by total internal reflection (TIR) towards the geometric half-space
Implementation Method 2
The lens section (4) is configured to control the light distribution pattern of the light source (13) (at least partly) received in the cavity (5) to exit into the geometric half-space (H1)
Data Source
Figure 1~3
Figure 4
Figure 5~7
AI summary
The present invention refers to an optical element (1) for controlling a light distribution pattern of a light source (13) radiating light beams (L) to a geometric half-space (H1) being defined by a geometric plane (Pi), wherein the optical element (1) is integrally made of a transparent piece (2) and comprises a base plate (3) of the transparent piece (2), a lens section (4) of the transparent piece (2), and a cavity (5) in the transparent piece (2). The part of the cavity (5) extending through the base plate (3) defines a bottom cavity space (50) which is circumferentially delimited by a redirection surface of the transparent piece and continuously tapers towards the lens section. An angle α of the redirection surface (6), with respect to the geometric plane (P1), at any part along its circumference is defined such that light propagating through the base plate (3) by internal total reflection towards the cavity (5) is redirected at the redirection surface (6) by total internal reflection towards the geometric half-space (H1) and preferably directly into the lens section (4).