Blu-ray disc wins the DVD reading issue by placing the data on top of a 1.1-mm-thick polycarbonate layer. Because it store data on the top of prevents birefringence, so prevents the readability problems happen. .In recording layer sitting near the objective lens, this question actually read mechanism is to eliminate plate tilt. Because this data is close to the ground, hard coating is installed in the disc to protect it from scratch and fingerprints.
The design of Blu-ray discs in manufacturing cost. The traditional DVD is based on two 0.6 mm discs injection molding machine which CD records layer sandwiched between. This process must be very carefully to prevent birefringence.
The two discs are molded.
The two discs are glued together.
The recording layer is added to one of the discs.
Blu-ray discs only on a single injection molding process 1.1 mm disc, thereby reducing costs. The balance of the cost price increases, so finally the ultimate price is no higher than the price fixed protection of the DVD.
Additionally, as to the data transfer rate, Blu-ray has a higher data transfer rate 36 Mbps (megabits per second), while DVD is only 10 Mbps. A Blu-ray disc can record 25 GB of material in just more than an hour and a half.