Light tube

A light tube brings sun inside.

It starts with a dome on a roof. This dome catches the sunlight. The light goes into a tube. The inside of the tube is very shiny.

This shine helps the light bounce. The light bounces down the tube. It can even go around bends. The light travels to a room.

A part at the end spreads the light. This makes the room bright. It can light up a dark space. It is a cool way to use the sun.

A light tube brings sunlight into a building.

These tubes help light rooms that do not have windows. They work in two main ways. Some are hollow tubes with shiny walls. Others are solid blocks that use total internal reflection. This is a way light stays inside a clear material.

Most light tubes start with a dome on a roof. This dome catches as much sun as possible. The light enters a tube. The inside of the tube is very reflective. Some tubes use a coating of gold to reflect light. This helps the light bounce down the tube. The tubes do not have to be straight. They can have bends and still work well.

At the end of the tube, a diffuser spreads the light. A diffuser is a part that makes light spread out. This makes the room bright and even. Some systems use a heliostat to help. A heliostat is a device that tracks the sun. It moves to catch the sunlight all day long. This keeps the light flowing into the tube.

A light tube is a clever way to bring sunshine into a building.

These tools are often called solar pipes or sun tunnels. They act as waveguides, which are paths that guide light from one place to another. Some light tubes are hollow structures with very shiny walls. Other types are made of solid, clear materials. These solids use a trick called total internal reflection to keep light trapped inside.

This helps light reach rooms that do not have windows.

How does the light travel through these tubes? Most systems start with a dome on a roof called a cupola. This dome catches as much sunlight as it can. The light then enters a tube lined with a highly reflective material. Some special tubes use a coating of gold to reflect infrared light.

This helps the light bounce down the path toward the floor. Even if the tube has bends, the light can still move through it. At the very end, a part called a diffuser spreads the light out. This makes the brightness feel even throughout the room.

People have been working on these systems for a long time. In the 1850s, Paul Emile Chappuis sold mirror designs in London. His company made these reflectors until 1943. Later, a company called Solatube International from Australia rediscovered the idea. They patented a new version in 1986 for homes and offices. Scientists also study new ways to move light. In 1994, researchers at Lawrence Berkeley National Laboratory made horizontal light pipe prototypes. These were designed to spread light deep into a room.

There are many interesting facts about how these tubes perform. Manufacturers say their tube linings can reflect up to 99.5 percent of light. Some systems use a heliostat to track the sun's movement. This device can even be set to catch moonlight at night! Other systems use optical fibers made of plastic or glass. One system can move light through 100 meters of a building. This is like traveling up 30 floors!

These fibers can carry light to places like Stockholm University.

You might already know about things that use similar ideas. A periscope uses mirrors to help you see around corners. A light tube is different because it does not try to make a clear image. It just wants to move the brightness. You can also think of optical fibers like the tiny wires used in high-tech tools. Some light tubes even use special layers to catch ultraviolet light. This helps them work well even on cloudy days. It is a wonderful way to use the sun to light our lives.

A light tube is an optical waveguide used to transmit or distribute natural or artificial light.

These structures are also known as solar pipes, sun tunnels, or tubular daylighting devices. They serve the important purpose of providing illumination to indoor spaces. There are two primary categories of these devices. The first type consists of hollow structures with highly reflective internal surfaces. The second type consists of transparent solids that use total internal reflection to contain light.

Total internal reflection is a process where light stays trapped inside a material. These systems are governed by the principles of nonimaging optics. This means they focus on moving light intensity rather than creating a clear image.

The mechanism of a standard light tube begins at an entrance point. This point is usually located on a roof or an outer wall. It often uses a dome, called a cupola, to collect sunlight.

Some systems add collectors, reflectors, or Fresnel lens devices to gather more directional light. Once the light enters, it travels through a tube lined with reflective material. This lining guides the light rays through the building. In some specialized cases, tubes are lined with a gold coating to reflect infrared light. This gold layer can be thick enough to resist highly corrosive atmospheres. While most pipes are round, some use square or hexagonal cross-sections. Hexagonal pipes are used to create a more homogenized type of infrared light.

There are several distinct ways to transport light using these technologies. One method uses hollow waveguides with highly polished linings. Another method uses optical fibers, which are thin strands of glass or plastic. For example, a system using plastic optical fibers was developed at Oak Ridge National Laboratory. These fibers can be designed to let some light leak through their cladding to distribute it. Another approach involves fluorescence-based systems. These use polymer layers to capture ultraviolet light. This light is then converted into red and green light. When mixed with blue artificial light, it creates white light. This method is very effective on overcast days because ultraviolet light passes through clouds easily.

The history of light tubes shows a long period of innovation. The first commercial reflector systems were patented in the 1850s. A man named Paul Emile Chappuis marketed these in London. He used various angled mirror designs for his products. His company, Chappuis Ltd, produced these reflectors until 1943. The concept was later rediscovered and patented in 1986 by Solatube International of Australia. This modern version is used widely in homes and businesses. In 1994, the Windows and Daylighting Group at Lawrence Berkeley National Laboratory developed horizontal prototypes. These were designed to move light deeper into rooms than traditional windows or skylights. In 2003, researchers in Brisbane won an innovation award for a light pipe system. This system used laser-cut panels to spread light throughout a building.

The efficiency and scale of these systems are quite impressive. Light transmission is highest when the tube is short and straight. To prevent loss, manufacturers use linings with reflectivities up to 99.5 percent. Some researchers at Texas A&M University tested pipes with a 99.3% reflective film. These systems can provide consistent light levels between 300 and 2,500 lux. This light can reach distances between 7.6 and 10 meters. Some optical fiber systems are even more powerful. They can transport light through 100 meters, which is roughly 30 floors.

To maximize light, a heliostat can be used to track the sun. A heliostat is a device that moves to follow the sun's path. It can even be used to capture moonlight at night.

Different applications show the versatility of light transport. In the Copper Box venue, light tubes are used to reduce energy use.

In commercial settings, modular fiber optic collectors can be used. These collectors come in different sizes, such as 4, 6, 8, 12, or 20 cables. These systems have been installed in places like Kastrup Airport and Stockholm University. Other specialized tools include prism light guides. A physics professor named Lorne Whitehead developed a prism light guide in 1981. These hollow guides lead light through air rather than a solid core. Even Disney has experimented with 3D printing internal light guides for toys.

Light tubes relate to many broader scientific and environmental fields. They are a key part of daylighting, which is the practice of using natural light in architecture. Using these tubes can provide better heat insulation than standard windows. This makes them useful for energy-efficient building design. They also connect to the study of photonics, which is the science of light particles. By using solar light, these systems help reduce the need for artificial electricity. This connects to larger goals of sustainability and resource management in modern cities.