A CD is read by focusing a 780 nm wavelength (near infrared) semiconductor laser housed within the CD player, through the bottom of the polycarbonate layer. The change in height between pits and lands results in a difference in the way the light is reflected. By measuring the intensity change with a photodiode, the data can be read from the disc. In order to accommodate the spiral pattern of data, the semiconductor laser is placed on a swing arm within the disc tray of any CD player. This swing arm allows the laser to read information from the centre to the edge of a disc, without having to interrupt the spinning of the disc itself.
A CD is read by focusing a 780 nm wavelength ( near infrared ) semiconductor laser housed within the CD player , through the bottom of the polycarbonate layer . The change in height between pits and lands results in a difference in the way the light is reflected . By measuring the intensity change with a photodiode , the data can be read from the disc . In order to accommodate the spiral pattern of data , the semiconductor laser is placed on a swing arm within the disc tray of any CD player . This swing arm allows the laser to read information from the centre to the edge of a disc , without having to interrupt the spinning of the disc itself .
What is used to discern the change of intensity in light on a CD?
What is used to discern the change of intensity in light on a CD ?
photodiode
photodiode