What is the spacing between ridges on a standard DVD?

I'm trying to find out how far apart the ridges are on the back of a DVD.What is the spacing between ridges on a standard DVD?
I think you're asking about track pitch -- the distance between the data tracks on a DVD.





From an Imation (disk manufacturer) web site (http://www.imation.com/products/dvd_medi鈥?/a>





';On a 3.95GB DVD-R, track pitch is 0.8 microns; CD track pitch is 1.6 microns. On 4.7GB DVD-R media, an even smaller track pitch of 0.74 microns helps boost storage capacity. ...';





Of the next-generation blue-laser disks, Blue-Ray has the shortest track pitch: 0.32 microns!





(Source: http://www.blu-ray.com/faq/ )





I hope this is the info that you were looking for, and that it is useful to you.What is the spacing between ridges on a standard DVD?
Pl. visit the source link.





READ BELOW:


*At first glance, a DVD disc can easily be mistaken for a CD: both are plastic discs 120mm in diameter and 1.2mm thick and both rely on lasers to read data stored in pits in a spiral track. And whilst it can be said that the similarities end there, it's also true that DVD's seven-fold increase in data capacity over the CD has been largely achieved by tightening up the tolerances throughout the predecessor system.





Firstly, the tracks are placed closer together, thereby allowing more tracks per disc. The DVD track pitch (the distance between each) is reduced to 0.74 micron, less than half of CD's 1.6 micron. The pits, in which the data is stored, are also a lot smaller, thus allowing more pits per track. The minimum pit length of a single layer DVD is 0.4 micron as compared to 0.834 micron for a CD. With the number of pits having a direct bearing on capacity levels, DVD's reduced track pitch and pit size alone give DVD-ROM discs four times the storage capacity of CDs.





The packing of as many pits as possible onto a disc is, however, the simple part and DVD's real technological breakthrough was with its laser. Smaller pits mean that the laser has to produce a smaller spot, and DVD achieves this by reducing the laser's wavelength from the 780nm (nanometers) infrared light of a standard CD, to 635nm or 650nm red light.





Secondly, the DVD specification allows information to be scanned from more than one layer of a DVD simply by changing the focus of the read laser. Instead of using an opaque reflective layer, it's possible to use a translucent layer with an opaque reflective layer behind carrying more data. This doesn't quite double the capacity because the second layer can't be quite as dense as the single layer, but it does enable a single disc to deliver 8.5GB of data without having to be removed from the drive and turned over. An interesting feature of DVD is that the discs' second data layer can be read from the inside of the disc out, as well as from the outside in. In standard-density CDs, the information is always stored first near the hub of the disc. The same will be true for single- and dual-layer DVD, but the second layer of each disc can contain data recorded ';backwards';, or in a reverse spiral track. With this feature, it takes only an instant to refocus a lens from one reflective layer to another. On the other hand, a single-layer CD that stores all data in a single spiral track takes longer to relocate the optical pickup to another location or file on the same surface.





http://www.pctechguide.com/34DVD_Technol鈥?/a>

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