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