How do projectors work

archive

BY HANS-J√úRGEN HUMBERT

In contrast to the other beamer names, when naming the LED projector, the focus is not on the technology for image generation, but on the light source. Instead of a large, very hot, electricity-guzzling high-pressure gas lamp, which is used in all other projector variants, a small semiconductor diode, the so-called LED, generates the necessary light in the LED projector. LED is an artificial word and means Light Emitting Diode, translated - light emitting diode.

The advantage of this technology: an LED is satisfied with little electricity and does not get hot. This is why LED projectors can be built very small; ideally, they are no larger than two cigarette packets. These devices are extremely portable and do not require a fan. Battery operation is also possible for several hours. So much for the advantages. The biggest disadvantage of this projector variant: LEDs are nowhere near as bright as other lamps. The maximum screen size is therefore limited and the room must be darkened.

DLP technology

Since LEDs only offer a limited light output, the image-generating chip has to be very careful with the light energy supplied. Due to their technology, LC displays swallow a lot of light, which is why DLP chips are built into all LED projectors. They work reflexively and throw almost 100 percent of the incident light onto the screen.

Since LEDs can also shine in all colors, there is no need for a color wheel. With the LED projector, too, three images are projected onto the screen one after the other. An LED can be switched over in a flash, so that the rainbow effect disappears.

Future prospects

LED projectors have only been around for a short time. Although LEDs have been manufactured since the 1970s, the light output was rather poor until a few years ago. Today, LEDs are used as additional brake lights in every car. They are also increasingly used as lighting objects in apartments. Large companies such as Osram, Luxeon and others are working to further increase the efficiency of these semiconductors. Headlights for cars can even be admired as laboratory samples. This technology offers great future potential, especially for projectors. LEDs can also be manufactured very inexpensively and they have a service life of several 10,000 hours - no comparison with a conventional projector lamp.

In the next issues you will read:

What exactly is surround sound?

What does 5.1 and 7.1 mean?

What actually is THX?

How should the loudspeakers be positioned?

What are sound processors?