In the GeSbTe system, there is a pseudo-line as shown upon which most of the alloys lie.
Optical substrates expert Chad R. Sandstrom of Imation Corporation provides the following explanation: This digital format was very quickly accepted as the standard because it provided compact size, high fidelity and tremendous durability.
But soon the consumer, accustomed to recording LPs onto magnetic tapes, demanded the same ability in the new compact disc format. The regular topography on the disc see atomic force microscope scan, top right causes the reflected light to "modulate" from bright to dark as the laser beam scans from an area with no pit to one with a pit as the disc spins under the focused laser beam in the drive.
To make a recordable disc, you start with a plastic substrate that has blank grooves rather than a predefined pattern of pits.
The blank grooves can keep the drive on track before the data is written. In addition to a layer of metal, the media includes a thin layer of dye.
Pulsing at high power, the laser in the drive can ablate or "burn" marks in the dye. Read back with the laser at the normal, lower read power, those marks look like pits to the detectors in the drive. Because the high laser power permanently changes the dye, this format can be written only once.
For additional rewriteable capability CD-RWa thin layer of so-called phase-change metal replaces the dye layer.
That material requires two extra "dielectric," or glassy, layers for protection. The drive employs a high-power laser to write amorphous marks in the metal layer, an intermediate-power level to write crystalline marks and a low-power level to read the recorded data.
To the drive, the crystalline areas appear bright and the amorphous areas appear dark. The crystalline-to-amorphous transition is reversible. CD-RW media see atomic force microscope scan, bottom right can thus be rewritten approximately 1, times.
But newer drives tend to be able to read the various formats. Gordon Rudd of Clover Systems offers this answer: All CDs and DVDs work by virtue of marks on the disc that appear darker than the background and can thus be detected by shining a laser on them and measuring the reflected light.
In the case of molded CDs, these marks consist of "pits" molded into the surface of the disc. Destructive interference of the laser beam caused by the difference in path length between the bottom of the pit and the surrounding "land" causes the pits to appear darker than the background.
These marks, too, appear dark compared with the background. Instead of dye or pits, these discs feature a layer of phase-change material.
This material can exist in two different solid states: Most solids have a crystalline structure in which the atoms are close packed in a rigid and organized array. But some materials can have an amorphous state in which the atoms are organized not into arrays but randomly, as in a liquid.
A common example of such a material is ordinary window glass, an amorphous form of silica.
The phase-change material can change from one phase to the other when it is heated and cooled. The material used is chosen because the two solid states reflect light differently. The amorphous state reflects less light than the crystalline state does. Therefore, by starting with a disc surface in the crystalline state, heating with the laser can change small spots to the amorphous state, which will appear dark upon playback.
Heating the material with the laser beam above its melting point transforms it from crystalline to amorphous. The rapid cooling of the spot causes the material to freeze in the amorphous state. These spots can then be erased in a process known as annealing.
This is accomplished by heating the material to a lower temperature, which transforms it back to its crystalline state.
Existing data can be overwritten by turning the laser on continuously to the erase power, which will erase any existing marks. Switching the laser to a higher power, one sufficient to melt the material, enables the creation of a new mark.
Sony Electronics marketing manager Robert DeMoulin writes: Once an area of the disc has been written to, it cannot be erased. The recordable layer is an organic cyanine or pthalocyanine dye.On the other hand, a CD rewritable drive enables you to write data to rewritable CDs (CD-RWs).
DVD-recordable drives write data to recordable DVDs. Similarly, DVD-RW drives can record, erase, and rerecord data on rewritable DVDs. Requirements. To record a CD, make sure your PC is fitted with a CD recorder drive. These drives are similar to regular CD drives but have a special laser inside that, besides reading the contents of a disc, can also record discs.
Oct 29, · When using a rewritable CD, you can burn it multiple times, and erase the contents on your CD. Their are ways of using a writable CD many times too.
if by ny chance, your burning program gives you a option of not finalizing a CD, then you can add and overwrite contents on that timberdesignmag.com: Resolved. I know it's kind of a dead / dying technology, but I was wondering what stops a CD-R from being rewritten like a CD-RW.
Is it some sort of firmware on the disc, essentially in place to make people buy more CDs? How to Erase or Overwrite a CD. March 31, By: Contributing Writer. Share; Share on Facebook; Erasing a CD is a simple process, but it can only be done with a CD-RW disk. The data on a CD-R is permanently written on the disc.
You are being eco-friendly when you use a CD-RW, because you are reusing a disc rather then burning a disc that. USA Office Supplies CD-RW High-Speed Rewritable Disc, MB, 12x, Slim Jewel Case, 20/Pack [VER] - Certified 4XX ultra speed rewrite timberdesignmag.comed Super Eutectic Recording technology, a Verbatim patented phase change recording layer, enhances archivability for superior durability and reliability at higher rewrite timberdesignmag.comable up to 1, timberdesignmag.com compatible with .