Lasers are used to read CDs, DVDs, and other optical discs because of their unique properties that make them ideal for this purpose. Regular light, such as from a conventional light bulb, is not suitable for this application due to several reasons:
Wavelength Precision: Lasers emit light at a specific wavelength, which can be precisely controlled. This characteristic is crucial for optical disc reading because the information on these discs is stored as microscopic pits and lands on the surface. The laser's wavelength is chosen to match the size of these features, allowing for accurate reading of the encoded data.
Coherence: Laser light is coherent, meaning it consists of waves that are synchronized and have a well-defined phase relationship. This coherence property allows for the formation of a focused, narrow beam that can accurately scan the surface of the disc. It helps to minimize interference and maximize the resolution of the reading process.
Intensity: Lasers can generate a highly concentrated beam of light with high intensity. This concentrated beam is essential for detecting and interpreting the tiny variations in reflection from the pits and lands on the disc's surface. The high intensity enables reliable detection of these small changes, enabling accurate reading of the encoded data.
Stability: Lasers provide a stable and consistent light source. The intensity and wavelength of the laser beam remain relatively constant over time, ensuring reliable and consistent reading of the disc. This stability is crucial for maintaining the accuracy and integrity of the data retrieval process.
Focusability: Laser beams can be easily focused to a very small spot size. This property is important because the pits and lands on the surface of optical discs are incredibly small, often measuring only a fraction of a micron. The ability to focus the laser beam precisely allows for the detection and differentiation of these minute features.
Overall, lasers offer precise wavelength control, coherence, intensity, stability, and focusability, making them the ideal light source for reading optical discs. These characteristics enable the accurate retrieval of data stored on CDs, DVDs, and other similar media.