LED optical design technology: from lens light distribution to free-form surface light pattern and efficiency control

Keywords: LED optical design, lens light distribution, free-form surface, TIR lens, light efficiency optimization

abstract

Optical design is the core of LED lighting performance. This article analyzes the technical principles and engineering applications of lens materials, light distribution curves, and free-form surface design.

3.1 Limitations of Traditional Lens Light Distribution

Spherical lens: There is spherical aberration, blurred edges of the light spot, and a light efficiency utilization rate of only 70% (such as replacing PAR30 halogen lamps with LEDs to increase light efficiency by three times, but the light type needs to be redesigned).

Fresnel lens: reduces thickness through a stepped structure, but there are diffraction fringes (affecting color rendering), and high processing accuracy is required (surface error<0.01mm).

3.2 TIR lens and total reflection principle

Total Internal Reflection (TIR) structure: By using a parabolic reflective surface to refract the lateral light of the LED to the front, the light efficiency utilization rate is increased to 90% (such as the Cree XP-G3 LED combined with a TIR lens, with a light intensity of up to 12000cd).

Light output angle control: By adjusting the top angle of the TIR lens (30 ° -120 °), flexible light distribution from narrow beam (10 °) to wide beam (120 °) can be achieved.

3.3 Freeform Surface Optical Design

Non imaging optical theory: Based on the Edge Ray Principle, the contour of free-form surfaces is optimized using ZEMAX software to achieve rectangular light spots with a uniformity greater than 90% (such as street light distribution requiring an aspect ratio of 4:1).

3D printing lens: Using Nanoscribe photolithography 3D printing technology, with a resolution of 200nm, it can manufacture complex free-form surfaces (such as the ADB lens for car headlights, which requires 2000 microstructure units).

3.4 Anti glare and color rendering optimization

Matte diffusion plate: By adding 20% barium sulfate particles to PC material, the uniform glare value (UGR) is reduced from 25 to 19 (meeting the office lighting UGR<19 standard).

High Color Rendering Index (CRI): Optimized fluorescent powder ratio (such as YAG: Ce 3 ⁺ and LuAG: Ce 3 ⁺ mixing) is used to achieve Ra>95 and R9>90 (museum lighting requirements).

3.5 Simulation and Testing Verification

LightTools simulation: Using Monte Carlo ray tracing method, predict spot uniformity, illuminance distribution, and stray light ratio (such as controlling stray light<5% for tunnel lights).

Integral sphere test: Using the Labsphere integral sphere system, measure the total luminous flux, light intensity distribution curve (C - γ graph), and spatial color uniformity (Δ u'v '<0.004).

conclusion

Optical design needs to shift from "simple light distribution" to "precise light pattern control". Efficient and comfortable lighting effects can be achieved through TIR lenses, free-form surfaces, and 3D printing technology.