Question

With the help of a block diagram, explain the working principle of disc recording system.

Hint:

Disc recording uses a laser to convert electrical signals into physical data marks on spinning discs for storage.

Answer 1

A disc recording system is used to record audio or video signals onto optical discs such as CDs or DVDs. The basic working principle involves converting electrical signals into optical signals to be stored on the disc surface. Block Diagram Components:

Input Signal: The audio or video signal to be recorded.
Encoder: Converts the input analog or digital signal into a digital format suitable for recording.
Error Correction and Control: Adds error detection and correction codes to ensure data integrity.
Modulator (e.g., HF Bias): Prepares the digital signal for optical recording by modulating it.
Laser Diode: Converts the modulated electrical signal into a focused laser beam.
Optical Pickup and Lens System: Focuses the laser beam onto the disc surface to create pits (data marks) during recording.
Disc Motor: Spins the disc at a constant speed to allow precise laser writing.
Working Principle: The input signal is first digitized and encoded with error correction data. The modulated digital signal controls the laser diode, which emits a laser beam that is focused onto the spinning disc’s recording layer. The laser intensity is varied to create marks (pits) and spaces representing the data. These marks are permanent physical changes on the disc surface. During playback, a lower power laser reads these marks by detecting reflected light changes.