The emitting angle of LED light emitting diode has an important influence on its lighting effect and practicality in different application scenarios, and optical design provides a variety of effective ways to change the emitting angle.
1. Lens design
Lens is the most common optical element used to change the emitting angle of LED. In terms of design, the first is the application of convex lens. By placing a suitable convex lens above the LED chip, the originally divergent light can be converged, thereby reducing the emitting angle. The radius of curvature of the convex lens determines its ability to converge light. A smaller radius of curvature will make the light converge more strongly and the emitting angle smaller. For example, in some LED lamps with spotlighting, the use of a convex lens with a high radius of curvature can reduce the emitting angle from about 120 degrees to less than 30 degrees, achieving a high concentration of light.
In contrast, a concave lens can be used to increase the emitting angle. A concave lens diverges light. When the concave lens is placed in front of the LED chip, the light will spread in a wider direction after passing through the concave lens. For occasions that require uniform illumination over a large area, such as basic indoor lighting fixtures, a reasonable design of the parameters of the concave lens can expand the luminous angle from the standard 60-90 degrees to 150 degrees or even wider, ensuring a wider lighting range.
2. Reflector design
Reflectors also play a key role in changing the luminous angle of LEDs. By designing a parabolic reflector to reflect the light emitted by the LED in a specific direction, the luminous angle can be effectively controlled. The position of the focal position of the parabolic reflector and the position of the LED chip are crucial. When the LED chip is located at the focus of the parabolic reflector, the light will be emitted in parallel after reflection, thereby achieving a smaller luminous angle, which is suitable for long-distance lighting.
For more flexible luminous angle control, an asymmetric reflector can be used. The shape of this reflector is not a traditional symmetrical structure. It can reflect light to different angle ranges according to actual needs. For example, in car headlights, an asymmetric reflector can project more light to one side of the road while ensuring a certain amount of front lighting to meet driving safety requirements.
3. Microstructure optical design
Microstructure optical surfaces can also change the luminous angle. For example, a microlens array is made on the surface of the LED packaging material, and each microlens can independently adjust the angle of a small part of the light. By accurately designing the shape, size and arrangement of the microlenses, the luminous angle of the entire LED can be precisely controlled. This microstructure design can not only change the luminous angle, but also improve the uniformity of luminescence, which is very effective in applications such as display backlight sources that require extremely high light uniformity.
