| Blu-ray is a cutting-edge, high-definition | | | | flaws in standard DVD's. One of these flaws |
| optical disc that can store significantly | | | | is birefringence. In a standard DVD, the |
| more data than a standard DVD. A | | | | recorded data is set between two |
| single-layer Blu-ray disc can store | | | | polycarbonate layers. The laser must shine |
| approximately 25 gigabytes of data: five | | | | through a layer of polycarbonate in order to |
| times the amount of a standard single-layer | | | | reach the data. |
| DVD. Dual-layer Blu-ray discs can store | | | | |
| twice the amount as single-layer discs, and | | | | Occasionally, the polycarbonate can split the |
| about eight times the amount of a standard | | | | laser into two beams instead of allowing it |
| dual-layer DVD. | | | | to penetrate, making the player unable to |
| | | | read the disc. The process of lining up the |
| A standard DVD contains enough space for a | | | | polycarbonate layers must be done with great |
| two-hour, non-high-definition movie, plus a | | | | precision to prevent birefringence. In |
| few extra features. A Blu-ray disc allows | | | | addition, the laser beam can become distorted |
| enough space for 13 hours of standard footage | | | | if the disc is not perfectly level inside the |
| or two hours of high-definition video. In | | | | player, a problem called "disc tilt." |
| addition, Blu-ray discs allow you to skip | | | | |
| instantly anywhere on the disc; record one | | | | On a Blu-ray disc, the data is printed on top |
| show while watching another; edit and reorder | | | | of the polycarbonate layer. With the data on |
| the footage on the disc; and access the web | | | | top, the laser does not have to shine through |
| to download subtitles and other extras. | | | | polycarbonate in order to read it-and the |
| | | | problem of birefringence is eliminated. This |
| All DVD's and CD's store information as a | | | | simplifies the manufacturing process, and |
| series of grooves on the recording surface of | | | | keeps the cost of Blu-ray discs down. In |
| the disc. The grooves are written in a | | | | addition, the data's location brings it |
| spiral that winds from the center of the disc | | | | closer to the lens that reads the laser. |
| to the outside edge. On one side, the | | | | This makes disc tilt much less of an issue. |
| grooves appear as pits; on the other, they | | | | |
| stand out as bumps. To read the disc, a | | | | Blu-ray stores more data, reads more clearly, |
| player shines a laser over the bumpy side of | | | | and provides interactive features you can't |
| the disc. The bumps cause the laser to | | | | get on a standard DVD. There aren't many |
| bounce back and register on a sensor. | | | | drawbacks to Blu-ray, but there are a few. |
| | | | |
| Standard CD and DVD players use a red laser | | | | Blu-ray discs require different equipment to |
| to read the information on a disc. Blu-ray | | | | manufacture. Despite the ease of making |
| compatible players use a blue laser. Blue | | | | these discs in comparison with standard |
| light has a shorter wavelength than red | | | | DVD's, manufacturers still have to invest in |
| light. This makes the laser itself more | | | | new machinery to make them. This may give a |
| sensitive and capable of detecting much | | | | slight edge to Blu-ray's major competitor: |
| smaller grooves than a red laser can. | | | | HD-DVD. HD-DVD is another type of |
| | | | high-definition DVD that can be manufactured |
| Because the blue laser can detect smaller | | | | using the same equipment used for standard |
| grooves, the information on a Blu-ray disc | | | | DVD's. It stores less information, but it's |
| can be written much smaller than on a | | | | also less expensive. |
| standard disc. This is why a Blu-ray disc | | | | |
| can contain so much more information than a | | | | Blu-ray discs aren't more expensive than |
| standard CD or DVD, even though the discs are | | | | standard discs, but Blu-ray players tend to |
| the same size. | | | | be significantly more expensive than HD-DVD |
| | | | players. You can buy players that will play |
| Blu-ray discs are constructed differently | | | | standard formats along with either HD-DVD or |
| than standard discs. These differences in | | | | Blu-ray, but no player can read both HD-DVD |
| construction eliminate some of the design | | | | and Blu-ray. |