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Blu-Ray: What is it? & How Does it Work?

written by: Daniel Barros•edited by: Michele McDonough•updated: 6/2/2009

We take you inside the machine to explain how this latest advance on the DVD technology we all take for granted actually works. Curious? Read on to learn more about the workings of Blu-ray.

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    Blu Lights

    Blu-Ray Among the many mysteries our universe has to offer us, there is the question I always get when showing off the new movie room, “What’s so different about Blu-ray?” Blu-ray isn’t a radical departure from a DVD the way a CD was from a Cassette, but that doesn’t mean that the technology isn’t radically different. What exactly does a Blu-ray disc have that’s so different from a DVD? Let’s investigate.

    Starting with the CD and then eventually with the DVD, the laser technology used inside the readers and writers was the usual cheaper, red lasers we’re all accustomed to. These red lasers read the grooves in the disc and manage to relay the information back to the processor which then interprets it into a video and/or audio signal. The difference between BD (abbreviation for Blu-Ray) and CD or DVD is that it uses a blue laser instead of a red one.

    The question then becomes, “Why is that significant?” Blue lasers are much more powerful than red lasers when it comes to reading the grooves and dents in a typical DVD disc. The easiest way to understand it is in terms of glasses and a sheet of paper.

    If I print out written information on a sheet of paper at 12 pt font, most people can read it unassisted (this would be the CD player) using just their regular reading glasses. However, I can take those same reading glasses and curve the lens even further, causing the person to be able to read even more information because now I can print it out in 8 pt font (this would be the DVD). However, if I can change the glasses in a way that allows them to zoom in, I can now print out information on that same sheet of paper at 2 pt font and have the person read it, allowing for much more information to be printed.

    This is a crude analogy, but the only purpose was to explain that Blu-ray discs are read on a much smaller scale than the traditional DVD. This allows for more information to be “burnt” onto a single layer, meaning that when you double up the layers in the disc, like you are able to do with a traditional 4.5 Gb disc, you manage to multiply the capacity by 2.

    This is why a single-layer BD-R disc can hold 25 GB of information and a dual-layer BD-R disc can hold up to 50 GB of information. This is a marvel when you consider that it was only about 20 years ago that most hard drives were just megabytes in size.

    On an interesting side note, because of the architecture of a Blu-Ray disc, you can print out the disc on a single 1.1 mm layer. This is different from a DVD because in a DVD, you need to press together two 0.6 mm layers. In this sense, the BD harkens back to the technology found in most 1.2 mm layered CDs.

    The tech inside the disc player is essentially the same it’s always been, but the addition of the blue laser is what drives the cost of the reader up so much – add to that the fact that newer Profile 2.0 players have built-in Wi-Fi antennas and you’re talking about a $200 increase from the most high-end DVD players.

    That’s how a Blu-ray disc works – it’s not much different from a DVD, but a simple blue laser is what makes all this technology work in perfect harmony. And if you’re wondering about the future of Blu-ray, Pioneer was able to increase the size up to 400 Gb by stacking 16 layers together. Can you imagine fitting an almost 500 Gb HDD into a single disc? That’s definitely a future I want to live in.