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LED diffusers: What to look for

October 19, 2016

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LED diffusers, LED light, India While direct light from LEDs can be very bright and intense, users might aim for softer, more customised lighting options for varied reasons. LED light diffusion is a great way to achieve the desired light intensity and colour. Here is everything one needs to know while choosing an LED light diffuser

By Baishakhi Dutta

Imagine a light diffusing material for LED products that eliminates hotspots, improves light output and reduces the number of LEDs required, resulting in cost savings. Imagine a material that allows you to control the quality of light the LED emits to meet specific needs. Traditional LEDs normally produce a pinpoint bright light called a hotspot. The latest developments in this field include new technology that provides uniform diffusion, resulting in a light source without hotspots.
LEDs are being increasingly used in signage, automotive components and architectural lighting, and their advantages are becoming apparent. These include energy-savings, reduced packaging, longer life and safer (lower heat) operation.
The option of using LED light diffusers, which can also control colour and contribute to design freedom, was not previously available when working with LEDs.

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The major purpose of diffusers
The major reasons why LED diffusers are used are:

Eliminates invisible hot spots
Very good light-scattering
Applicable in very flat, homogeneously illuminated light elements
Diffusion breaks straight beams of light from the source, scattering them in different directions and producing a glow, rather than a sharp beam, which is soothing to the eyes.
Diffusers mimic the soft natural light from the sun (diffused naturally by clouds and the atmosphere), eliminate harsh shadows, offer larger expanses of continuous illumination, and improve aesthetics and occupant comfort.

Light diffusing compounds
With the expert manipulation of dye and pigment combinations, the light diffusing compounds can change the colour of an illuminated graphic, for example, from blue to green by filtering specific wavelengths of the emitted light. This colour-converting technology provides designers with a wider range of colour options for interiors. It can also be used with white LEDs to fine tune the colour temperature in both warm white and cool white spectrums.

LED light diffusion – applications and advantages
Electronics, outdoor lighting, signage and automotive: LED lights are in huge demand, and hence, LED light diffusers have a major role to play. They are of great use in outdoor lighting and signage. Even in the automotive sector, LED diffusers play a very crucial role.
More consistent and pleasing light for consumers: LED diffusers offer a great aesthetic advantage as they ensure consistency of light output which is also pleasant to the eye.
Eliminates hotspots: LED diffusing compounds provide consistency by eliminating hotspots, which is critical to achieving compelling interior lighting harmony.
LED colour variation: LED diffusing compounds provide colour variation since the human eye is highly sensitive to differences in hue, and even perceives differences in intensity as a difference in colour.
Expands the design space: Lighting designs must be functional, attractive and lightweight while also delivering high optical efficiency and light uniformity.

Transmittance and its importance
Transmission is the property of light which helps it to pass through a transparent object after a part of it is absorbed and/or reflected. Transmitted light is what we see, and clear transmission depends on a number of properties of the incident object (size, shape, thickness, material, etc).
Total transmittance is a sum of the following components:

Direct transmittance, which is the amount of light that passes through a medium without being scattered or diffused. It is caused by irregularities on the surface or the interior of the medium.
Diffused transmittance is the portion of light that is scattered or diffused by irregularities. It is a measure of the degree of scatter.
Diffusion or haze is the measurement of wide-angle scattering and causes a loss of contrast.
Clarity is the measure of narrow-angle scattering. This can be best explained when the detail of an object is lost when viewed through the medium. Clarity is inversely proportional to distance, i.e., details disappear with increasing distance.

Key usage areas
The two most important uses of LED diffusers are:

To hide the light source, e.g., in backlit displays, signs and architectural lighting
To eliminate projected hotspots, e.g., in architectural lighting and light pipes

Types of LED diffuser solutions
LED diffusers are based on high-efficiency micro-lenses in optically clear materials, providing superb performance in angle control, efficiency, source hiding and aesthetics. They are available in a variety of materials and form factors, including UV-tolerant film and rigid sheets. Some of the available LED diffusers are:

UV stabilised polycarbonate diffusers
Tempered glass diffusers
PMMA optical diffusers
3D three-sided diffusers
Anti-glare diffusers
Transparent diffusers (DT)
Opaque diffusers (DO)
Satin diffusers (DS)

An LED diffuser sheet is, typically, a component in screen backlights. Its main purpose is to evenly distribute light from LEDs on the edge of the screen, so that there are no bright spots near them. It is usually composed of many sheets of plastic in varying thicknesses and opacity or reflectivity. It can also be used in larger scale lighting to balance out the output of an LED lamp and make the light more evenly cast.
Generally, LED diffusers are available with frosted (translucent) or opal (milky) surface finishes. The frosted diffuser allows good light transmission, but the LED lights are somewhat visible. The opal diffuser provides more uniform light diffusion and good LED concealment.

Application areas of LED diffusing compounds

Lenses
Buttons
Switches
Knobs
LED backlit signage
Channel lettering
Architectural accent lighting
LED light bulb lenses

A few Products available in the market

Optics glass diffusers from Cree
Features

Cree emitters
Diameter: 20mm
Angle of 30 degrees
Lens for Cree emitters
Plastic material
Ideal for lampshades, lighting, etc

Contact details: www.cree.com

Bright View Technologies’ C-series symmetric diffusers
Features

General-purpose symmetric diffusers
Lamp hiding, colour mixing and angle management
C-series diffusers efficiently hide lamps and provide smooth illumination in both LED and fluorescent applications. They provide excellent de-pixelation, angle control, colour mixing, and colour uniformity

Contact details: www.brightview.com

Dow Corning 30-424 Additive
Features