Slim Optical Element for Uniform Illuminance Using Inclined Surfaces
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Solution Overview
Problem
Existing illumination units using LEDs struggle to achieve both slimness and evenness of illuminance on a plane, with previous designs either failing to provide sufficient slimness or resulting in uneven illuminance due to direct light emission from lenses, which creates outlines on the illuminated surface.
Innovation Solution
An optical element with a concave reflecting surface and specific inclination conditions to ensure that 80% or more of emitted light is reflected, and the light exit surface is designed to prevent direct emission from small angles, using expressions to determine the optimal inclination of the light receiving surface to achieve high evenness of illuminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a planar light source device with optical elements is used to achieve slimness, then the illumination unit becomes thinner, but unevenness of illuminance occurs due to direct light emission from lenses
Solution Approach 1:
The optical element is divided into three distinct functional surfaces: a light receiving surface for capturing light, a reflecting surface for redirecting light, and a light exit surface for emitting light. This segmentation allows each surface to be optimized independently, with the reflecting surface specifically designed to prevent direct light transmission and ensure uniform illuminance distribution while maintaining the slim profile of the illumination unit.
2Ease of manufacture
If conventional lens structures are used, then light can pass through directly, but outlines of lenses become visible on the illuminated plane
Solution Approach 1:
Different regions of the optical element are assigned different optical functions. The light receiving surface has a specific inclination angle θp to control light entry, the reflecting surface is positioned to intercept and redirect light paths, and the light exit surface is configured to emit light uniformly. This local differentiation of optical properties eliminates visible lens outlines while maintaining manufacturing feasibility.
3Device complexity
If the light receiving surface is made perpendicular to the emitting surface, then light transmission is simple, but direct light exits without reflection causing illuminance unevenness
Solution Approach 1:
The inclination angle θp of the light receiving surface is optimized to a specific value that satisfies particular mathematical expressions. This parameter optimization ensures that light entering the optical element is properly directed toward the reflecting surface, which then redirects the light to achieve uniform illuminance distribution on the illuminated plane while preventing direct light transmission.
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 effectively eliminates unevenness of illuminance, allowing for a slim and even illumination unit with high evenness of light distribution across the illuminated surface, enhancing the optical element's design to maintain slimness while ensuring uniform illuminance.
Implementation Method 1
lights emitted from the point O are reflected on an area of 80% or more of the reflecting surface
Implementation Method 2
refractive index of a material of the optical element is designated as n, inclination of the light receiving surface with respect to the first plane is determined
Data Source
AI summary
An optical element according to the present invention includes a light receiving surface which is designed to cover an emitting surface of a planar light source device, a reflecting surface, a light exit surface which is contiguous to the periphery of the reflecting surface. When the center of the emitting surface is designated as a point O and an axis which passes through the point O and is perpendicular to the emitting surface is designated as an optical axis of the optical element, the reflecting surface has a concave portion around the optical axis and an outer edge surrounding the concave portion.