Product Roundup – LED Accessories: Lenses and Reflectors

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With fluorescent lights, most of the light’s spread is directed away from the intended focus of the light. LEDs solve this problem with the primary LED optic that both protects the LED and gives shape to the light output. This spread of light from the central axis is why LEDs are considered more efficient than fluorescents and metal halide lamps that must use reflectors to properly direct light output. Along the central axis of the device, LEDs boast 100 percent intensity emitted, illuminating 180 degrees, but the light intensity wanes farther from this axis.

Light output from LEDs—while concentrated—still requires lenses, reflectors, diffusers, or total internal reflection (TIR) optics for optimal performance. A TIR consists of a refractive lens nestled inside a reflector; it is typically cone-shaped with optical efficiencies up to 92 percent.

An LED package is comprised of a semiconductor chip mounted on heat-conducting material and a lens to enclose the die. Heat and power regulating components are also integrated, since heat dissipation, thermal stresses and cost are key LED concerns. Heat dissipation limits power levels. Applications such as solid-state lighting, and backlighting for flat-panel monitors and TVs depend on brighter LEDs that run hotter and operate at higher wavelengths. Packages may come in a variety of shapes.

The FA10339_NIS83-MX-M optical lens by Ledil Oy, for example, features a square shape, optic and holder polycarbonate material, and has a diameter of 21.6 x 21.6 mm and a height of 13.5 mm. The device has an efficiency of 86 percent, a full width at half maximum bandwidth of 30 percent, and a candela/lumen factor of 2.300.

Reflectors are simpler to implement and less expensive to manufacture than TIR optics, and light propagation depends on shape. Faceting, segmenting, and applying different textures or finishes can further diffuse light.

The C10920_BRIDGET-W reflectors are designed for the Bridgelux BXRA-C/N/W 0400 series of LEDs. The goal is a uniform white or warm white illumination; however, the lenses work well with other colors as well. Featuring compact dimensions and optical-grade metalized polycarbonate material, the device can be used in high current and temperature conditions.

 C10920_BRIDGET W reflector front and bottom views

Figure 1: C10920_BRIDGET-W reflector front and bottom views. (Source: Ledil Oy)

In comparison, CA11402_BRITNEY-W reflectors target the Bridgelux Bxra C4500 and W3000 series of LEDs. They are easily and accurately assembled to the PCB and are shipped with a PU foam adhesive tape of automotive grade attached for easy mounting. The reflector material is optical-grade metal and protective lacquer-coated polycarbonate, enabling use in high-current and temperature conditions.

Advances in LED accessories include films that are applied onto a plastic substrate and are non-conductive and highly reflective, and can be superior to aluminum. In addition, specular polymer can be custom-molded into reflectors to add precision, enhance surface reflectance, and sit very close to the LED. Silicones are the material of choice for high-brightness LED packaging given their electrical, mechanical and thermal performance as well as their ability to provide stability, longevity and stress-relieving properties.

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