Do you remember that boring lectures you attended in your college delivered by those slide projectors? If not, you are lucky to experience the modern version of projectors.
In the past, we abhorred those nuisances that made our classes and presentations so tedious. However, today these devices have revolutionized those dull hours into an exciting and productive time.
Now, you see video projectors everywhere. There are LCD, DLP, and LCoS projectors. Office meetings have become animated, and the magic of cinema has come to homes.
Have you ever wondered how these devices work? What is the difference between the working of LCD and LED projectors? How do LCD and LED projectors work?
Let’s discuss their mechanics in detail. Don’t worry! We’ll keep it simple. Let’s take you on a magical ride to show what happens behind the scenes.
The physics of how a projector work
Before moving on to the specific projector types, let’s start with the basics. We all know that a projector displays images or videos on a bigger screen. So, in essence, a projector follows the path of a camera in the opposite direction.
In a camera, the image is outside, but the device captures it inside. How does a projector work? It takes the picture or video and displays it on a screen in a bigger size.
So, the physics is the same. The light travels in the reverse direction only. In a projector, a lamp or light source throws a powerful light beam on the image. Then, the reflected light goes through a lens to finally display the image on the screen.
Modern projectors have started using powerful lens and prisms to form larger and brighter images. Apart from some minor changes, the basics are the same for all projector types, including LCD, DLP, and LCoS projectors.
How an LED projector Works
Many people are confused between an LCD and an LED projector. Some consider LED projectors as a separate technology than LCD and DLP projectors. However, that is not the case.
LED projectors use LEDs as a light source only. In a projector, you can get light from several different sources. A metal halide lamp, UHP lamp, LED, or laser all work as a light source. The rest of the display technology depends on an LCD or DLP projector.
How does an LED projector work? It uses a light-emitting diode (LED) to produce light. Are you wondering about how an LED works? Let’s simplify the physics behind it.
An LED is a device that produces light when you pass an electric current through it. Electrons and holes carry this current. When the two meet, the electrons release energy in the form of photons.
The amount of light/photons emitted depend on the energy difference (bandgap) between the electrons and holes. The energy released determines the wavelength or the color.
So, to produce red, blue, or green colors, you can alter the bandgap. A projector uses three different LEDs of primary colors. Here, it uses a solid semi-conductor so, we have named this type of light production solid-state lightning.
The light produced will then go to the LCD or DLP chip to form the image. Read on to know more about how an LCD projector works.
You may be wondering about how LED light source is better than others? Let’s discuss some pros.
LED projectors consume lower energy than others and produce lesser heat. They can work in a small space, including pico projectors. Do you want long-lasting projectors?
LED projectors have the most lamp life and no fans. We guess you are wondering what’s the catch. It is their lower brightness. You get only 3,000 to 3,500 lumens only.
How an LCD projector works
As famous as LCD has become, you would be familiar with the technology. LCD is a liquid crystal display. Are you wondering that how can a crystal be liquid? Let’s clear up your ambiguity.
The working of LCD lies in this liquid crystal. It resembles both solid and liquid in its characteristics. Interestingly, its molecules maintain their position like a solid but move around like a liquid.
So, how does this state of matter is achieved? Do you know how you melt the ice to get water? If you melt the solid sufficiently until it is close to liquid but not quite there yet, you get these unique liquid crystals.
So, these crystals are closer to liquids than solids. What use does this give us? To tell you in simple terms, LCDs use these crystals and produce light when an electric current passes through them. They have numerous tiny, colorless pixels to allow light when there is a current.
Do you know when LCD became available for projectors? The usage of LCD in projectors started with the first LCD projector in 1984. They are older than DLP but still in demand.
Let’s come to how do LCD projectors work? Firstly, there is a light source. Unlike LED projectors, here, we use a metal halide lamp. The light from the lamp passes to dichroic mirrors.
These dichroic mirrors are covered with a film to reflect only a certain wavelength. So, the mirrors split the light into three primary colors.
The three beams of light pass through three prisms. The projector then reflects them onto the three LCD panels. We have discussed above how these LCD panels work.
So, the current stimulates the LCD panels and lets light pass through them. Here, it arranges the pixels in the appropriate image.
The three panels form three images but with different hues. Each image has the domination of a single primary color. However, we need a single image with all the colors. Right?
So, to get them fused into one, there is a second dichroic prism. Four triangular prisms combine to form a single dichroic prism. The three images converge into one with millions of colors.
Here, we get 16.8 million colors, including 256 shades of red, blue, and green separately. Finally, this image passes through the lens to get on the screen.
Let’s summarise. The light from the lamp goes to dichroic mirrors and forms three beams. They pass through prisms, go to LCD panels, and on to the second prism. After passing through the lens, it forms an image.
An interesting thing to note here is how the light transmits from one to another instead of reflecting off surfaces. So, how does the working of LCD projectors is better than others?
They have a zoom lens, lens shift, and more luminance. The best thing is how it uses no moving parts. So, you have no rainbow effect. They consume less power than DLP projectors, too.
The LCD technology is not foolproof, however. These projectors produce a screen-door effect when you display them on bigger displays.
What is the screen-door effect? The image looks like you are watching it through a screen door. If a projector stretches a display across a much wider field, you get this effect.
The most common complaint is about dust smudging and bad pixels. There are 2,359,296 transistors on a single laptop screen only. For a projector, their number is much more. As there are millions of transistors, a problem with any one of them results in a dead pixel.
Do you know that the sale of projectors is on the rise? They are used abundantly in classrooms, offices, and homes. While using these devices, we should get familiar with what happens inside them.
A projector is a reverse camera that uses light to display a large image using lenses and prisms. We have discussed the basics of how an LED and LCD projector works. Apart from the light source, they can be quite similar.
As for DLP projectors, they use a different technology to project. LCD projectors use dichroic mirrors to form three colors and then fuse them into a single image. They produce 16.8 million colors.
Apart from the basics, you’ll get a similar pathway inside any projector. We hope you understood how a magical image is formed on a screen using a small device.
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