How to increase the optical efficiency of LED lenses to 99%?

Power LEDs are used in the field of lighting, and secondary optical lenses are used to achieve good light distribution. The lenses of various properties designed to meet different effects are mostly optical grade acrylic (PMMA). Its light transmittance is about 92%.

You may have to say, yeah, the material transmittance is 92%. Why do you say 99%?

The guest officer is in a hurry, listen to me:

There are two main reasons for causing light loss:

1. Reflection loss at the transmission interface

2. Absorption loss of optical material itself

The loss of light caused by interface reflection is often neglected, and everyone is more concerned with the absorption of the material itself.

In fact, for a lens with a high transmittance and a small volume, the loss caused by the interface reflection is far greater than the loss absorbed by the material itself.

What is the interface reflection loss?

When the light passes through the interface with different refractive index, interface reflection occurs, and there is a certain reflection loss.

The ratio of the reflected light flux to the incident light flux is called the reflection coefficient (reflectance).

Therefore, when the ordinary lens is used, the light is lost like this:

Suppose the light emitted by the chip is 104.

Through a lens (package), after a single interface loss of 4%, leaving 100;

When entering the secondary lens, another interface loss of 4%, leaving 96;

From the secondary lens, it is an interface loss of 4%, and finally 92.

Figure: Light loss of a normal lens

What if the gap between the primary and secondary lenses is filled?

It's a good idea to reduce the interface loss twice!

Thus, when the glue lens is in use, the light is lost like this:

The light emitted by the chip is still 104.

Out through a lens, no interface, no loss, leaving 104;

When entering the secondary lens, there is no interface, no loss, leaving 104;

From the secondary lens, this time there is interface loss, 4%, and finally 100!

Figure: Light loss during filling of the primary and secondary lens gaps

100%-92%=8%, light efficiency increased by 8%

This "filling up" method is the "adaptive colloid" technology.

Adaptive gel technology lens advantages:

1. The lens transmittance is over 99%, and some light sources can exceed 100%;

2. Compared with ordinary street lamp lens, the efficiency is improved by 8~10%;

The lens and colloid are like this:

Figure: Glue lens

Figure: Colloids that automatically fill the gap

Can't just blow the theory, actually measure it:

1. When the lamp is not equipped with a lens, enter the integrating sphere test and the results are as follows:

Reported by the test: bare light source luminous flux 618.2 lm color temperature 3672 K.

2. Install with a filled colloid lens and test again:

The test results show: luminous flux after lens: 615.8 lm color temperature: 3729 K.

From the above test results found:

1. The transmittance of the lens is: 615.8/618.2 = 99.61%

2. The color temperature drift of the lens is: 57 K, 1.5%