How Optical Storage Works
ASSIGNMENT 4 WEEK 1 - STORAGE DEVICES
Describe the main working features of ONE of the following storage devices.
Hard disk drive
Optical storage
Flash memory
Include any relevant diagrams that help explain your answer.
Optical Storage
The optical storage device that most of us are familiar with is the compact disc (CD). A CD can store huge amounts of digital information (783 MB) on a very small surface that is incredibly inexpensive to manufacture. The design that makes this possible is a simple one: The CD surface is a mirror covered with billions of tiny bumps that are arranged in a long, tightly wound spiral. The CD player reads the bumps with a precise laser and interprets the information as bits of data.
The spiral of bumps on a CD starts in the centre. CD tracks are so small that they have to be measured in microns (millionths of a meter). The CD track is approximately 0.5 microns wide, with 1.6 microns separating one track from the next. The elongated bumps are each 0.5 microns wide, a minimum of 0.83 microns long and 125 nanometres (billionths of a meter) high.
Most of the mass of a CD is an injection-moulded piece of clear polycarbonate plastic that is about 1.2 millimetres thick. During manufacturing, this plastic is impressed with the microscopic bumps that make up the long, spiral track. A thin, reflective aluminium layer is then coated on the top of the disc, covering the bumps. The tricky part of CD technology is reading all the tiny bumps correctly, in the right order and at the right speed. To do all of this, the CD player has to be exceptionally precise when it focuses the laser on the track of bumps.
When you play a CD, the laser beam passes through the CD's polycarbonate layer, reflects off the aluminium layer and hits an optoelectronic device that detects changes in light. The bumps reflect light differently than the flat parts of the aluminium layer, which are called lands. The optoelectronic sensor detects these changes in
Describe the main working features of ONE of the following storage devices.
Hard disk drive
Optical storage
Flash memory
Include any relevant diagrams that help explain your answer.
Optical Storage
The optical storage device that most of us are familiar with is the compact disc (CD). A CD can store huge amounts of digital information (783 MB) on a very small surface that is incredibly inexpensive to manufacture. The design that makes this possible is a simple one: The CD surface is a mirror covered with billions of tiny bumps that are arranged in a long, tightly wound spiral. The CD player reads the bumps with a precise laser and interprets the information as bits of data.
The spiral of bumps on a CD starts in the centre. CD tracks are so small that they have to be measured in microns (millionths of a meter). The CD track is approximately 0.5 microns wide, with 1.6 microns separating one track from the next. The elongated bumps are each 0.5 microns wide, a minimum of 0.83 microns long and 125 nanometres (billionths of a meter) high.
Most of the mass of a CD is an injection-moulded piece of clear polycarbonate plastic that is about 1.2 millimetres thick. During manufacturing, this plastic is impressed with the microscopic bumps that make up the long, spiral track. A thin, reflective aluminium layer is then coated on the top of the disc, covering the bumps. The tricky part of CD technology is reading all the tiny bumps correctly, in the right order and at the right speed. To do all of this, the CD player has to be exceptionally precise when it focuses the laser on the track of bumps.
When you play a CD, the laser beam passes through the CD's polycarbonate layer, reflects off the aluminium layer and hits an optoelectronic device that detects changes in light. The bumps reflect light differently than the flat parts of the aluminium layer, which are called lands. The optoelectronic sensor detects these changes in