Lens for LED optic needed?

by | Feb 17, 2021 | Optics explained

When we think about an LED optic we think about a clear plastic lens that is on top of the LED to focus or spread the light. A lens for LED will function as an optic to collect light and magnify its intensity towards the target.

Primary optics and secondary optics

A LED has a small protective dome over the diode, this is called the primary optic which serves both to protect and shape the output of the diode. However, the light from the primary optic is still too broad for most uses and it lacks intensity over distance. That is why most LEDs use a secondary optic as well, like reflectors and TIR optics. These secondary optics are also used to collect light and magnify its intensity  towards the intended target.

Creating lenses for LED

Creating reflectors and lenses for LEDs (solid-state lighting) is different than just adjusting designs from other light sources. For instance, incandescent bulbs illuminate in 360 degrees, but LEDs are directional lighting, illuminating 180 degrees. The maximum angle LEDs can emit is 180 degrees as the substrate is on the back of the die.

Spatial distribution

Spatial distribution is used to describe the light coming from an LEDs primary optic. It refers to the shape, or spread, of the light from the center of the LED. You can imagine a line running straight down the center of the diode. Spatial distribution is measured in degrees from this center point. The emitted light will be stronger in the center. Along the center the diode emits 100% of its relative luminous intensity and it will lose intensity farther away from the center. The use of a secondary lens or optic is needed to intensify the light and use the brightness and efficiency of the diode to full capacity.

Focusing lenses for LEDs

High power LEDs give off a Lambertian light distribution. Meaning that the brightness is the same for an observer, regardless of his or her position. Even when looking at the light source from the far side it is noticeable that the light source is extremely bright. This is where secondary optics can help, they collimate the light into a controlled beam that will bring the intensity to the area where needed. Collimated light rays will spread in parallel (however, it is impossible to make the light exactly parallel because of finite physical size of the emitter and diffraction).

Full width half maximum (FWHM)

FWHM is the angular width of the beam when the intensity at the edge is half the intensity in the center of the beam. This does not take into account the differences between optical platforms (e.g. varying diode sizes), nonetheless it is a handy way to classify optics. Even optics with identical viewing angles can differ in intensity and quality of the light beam, depending on the emitters optical design.

LED lens design and manufacturing

There are various factors to take into account when designing an optic for your project.

Beam Angle

The angle over which the emitted light is distributed. Lenses and reflectors are used to help create the desired beam angle. For example, narrow beam angles (e.g. 40°) have a tight light beam and are commonly used for LED spotlights. Wide beam angles (e.g. 120°) have a large coverage for wide area lighting.

Diffusion

Clear lenses provide a crisp beam of light. However, sometimes you might want a softer edge. Diffusion can help offer a more uniform light output, especially when multiple LEDs are utilized.

Amount of LEDs per lens

Are you designing for a single LED or array? Multiple LED lenses are ideal for wide area lighting (e.g. street lighting).

Attaching

How will the lens or reflector be attached? Will you twist or snap it onto a LED holder? Or will you use screws or special clips?

Custom lens for LED

Are you looking for a custom lens for your LEDs? Most of the available stock optics for LEDs might not be perfect for your project. And making changes to stock optics can be costly and time consuming. However, with our unique solution you no longer have to settle for sub-par optics. Addoptics offers smart manufacturing of polymer optics. Meaning you send us your optics design and we manufacture a batch within a matter of days. Our unique approach is ideal for both prototyping as well as series production.

Check our datasheet for our most up-to-date capabilities and material properties.

With our technology you can make use of rapid prototyping for your optics project. For instance, you can send a couple of different optical designs. We can manufacture all of them, ship them to you within a couple of working days and you can test and optimize the parts. After testing and optimization we can move on to series production with the finalized design.

If you would like to work with Addoptics and have your optics manufactured within a couple of days, please feel free to reach out to us so we can discuss your project.