Optical disk drives are readily available for purchase as computer peripheral devices. However, considerable additional engineering and programming expertise may be required for the hardware customization and software development necessary to combine scanners, computers, optical media, video displays, printers, and other components into an effective document storage and retrieval system. Write-once optical disks record unremovable information. Erasable optical disks, like their magnetic counterparts, permit reuse of previously recorded media segments. There has been very little standardization in disk design.
Optical disks differ in materials, construction, thickness, etc.
Regardless of recording technology or media source, write-once optical disks are enclosed in plastic cartridges to facilitate handling and protect them from environmental contaminants. The information is represented on the disk by a change in the surface reflectivity and is read by using a low-powered laser to sense the changes. Optical disks have recording surfaces on either one side or both sides, with dual sides being the most common. State and federal historical legislation, which allowed for the admissibility of microfilm as evidence, had to gradually develop. Paper copies of microfilmed records are admissible if microfilm is created with proper certification and standardized procedures.