The uniformity of the light distribution curve of an LED filament bulb directly affects its lighting effect. Uneven light distribution can easily lead to localized overbrightness or underbrightness, affecting visual comfort and the overall lighting environment of the space. As a core component for light control, the optical lens design must comprehensively consider the characteristics of the light source, the light emission angle, and the target lighting scene, achieving uniform light distribution through precise optical path control. This process involves multiple stages, including material selection, surface design, multi-layer structure optimization, and simulation verification, requiring systematic collaboration to achieve the desired effect.
The optical properties of the lens material are fundamental to the uniformity of light distribution. Traditional lens materials such as PMMA (polymethyl methacrylate) have high transmittance, but are prone to deformation at high temperatures, leading to optical path deviation. While PC (polycarbonate) has better heat resistance, its surface is easily scratched, affecting long-term transmittance. Therefore, materials with both high transmittance and weather resistance must be selected, such as modified PC or silicone with added UV-resistant additives. These materials not only maintain optical stability over a wide temperature range but also improve wear resistance through surface hardening treatment, ensuring long-term consistency of the light propagation path. Furthermore, the refractive index of the material must match the wavelength of the light source to reduce light reflection loss within the lens and improve light extraction efficiency.
The curved surface design of the lens is crucial for controlling light. LED filament bulbs typically use linearly arranged filaments, with their light emission directions distributed at multiple angles. The curved surface structure of the lens is necessary to redistribute the light. For example, a freeform surface design allows for customization of the surface shape based on the light-emitting characteristics of the light source, ensuring uniform light diffusion within the target area. Specifically, the incident surface of the lens must closely conform to the shape of the filament to reduce light scattering; the emitting surface must be designed as an asymmetrical curved surface, adjusting the light angle through local curvature changes to avoid excessive brightness in the center and darkness at the edges. Additionally, the transition between curved surfaces must be smooth to avoid abnormal light refraction caused by sharp angles, which could lead to fluctuations in the light distribution curve.
Multi-layered lens structures can further improve light distribution uniformity. A single lens cannot simultaneously meet the needs of wide-angle diffusion and central light intensity control. However, by stacking lens layers with different functions, staged control of light can be achieved. For example, the bottom layer lens collects the raw light emitted by the filament and directs it in a specific direction through total internal reflection or refraction; the middle layer lens initially diffuses the light, reducing the intensity of the central light spot; and the top layer lens softens the light through microstructure or frosted treatment, resulting in a smoother light distribution curve. The synergistic effect of the multi-layer structure effectively compensates for the design limitations of a single lens, improving overall light distribution uniformity.
The coupling design between the lens and the light source requires precise matching. The luminous characteristics of the LED filament and the optical performance of the lens must be highly compatible; otherwise, it can easily lead to decreased light utilization or light distribution distortion. For example, the lens installation position must be aligned with the filament center to avoid light deflection caused by misalignment; the focal length of the lens must be adjusted according to the filament length to ensure effective focusing and diffusion of light within the lens. Furthermore, the gap between the lens and the filament must be filled with potting compound to reduce abnormal light refraction caused by air gaps and improve structural stability.
Simulation verification is an important tool for optimizing lens design. Optical simulation software can simulate the propagation path of light within a lens, identifying dark or overly bright areas in the light distribution curve in advance, and allowing for targeted adjustments to lens parameters. For example, adjusting the local curvature of a freeform surface can optimize the distribution of light rays at the edges; modifying the thickness ratio of multilayer lenses can balance the intensity difference between the center and edges. Simulation verification can significantly reduce the number of physical prototype trials, lower development costs, and improve design efficiency.
Actual testing and iterative optimization are crucial for ensuring the design's successful implementation. Simulation results must be verified through laboratory testing, including light intensity distribution testing, illuminance uniformity testing, and glare assessment. If the test results deviate from the simulation, the cause must be analyzed and the lens design adjusted, such as optimizing surface accuracy, improving the multilayer structure, or adjusting material parameters. Through multiple iterations, the ideal light distribution curve can be gradually approximated, ensuring that the LED filament bulb meets the uniform lighting requirements in practical applications.
Optimizing the uniformity of the LED filament bulb's light distribution curve requires collaborative design across the entire process, including materials, structure, simulation, and testing. By selecting high-transmittance, weather-resistant materials, customizing freeform surfaces, stacking multi-layer lenses, precisely coupling light sources, and conducting simulation verification and iterative optimization, efficient and uniform light distribution can be achieved, providing a comfortable, dark-free lighting environment for indoor lighting. This process requires not only professional knowledge of optical design but also a deep understanding of the characteristics of LED light sources and the needs of lighting scenarios, representing a deep integration of optical engineering and lighting design.
