 A week after the launch, "The Dark Knight" BD had sold over 1.7 million copies worldwide, making it the first Blu-ray Disc title to sell over a million copies in the first week of release.According to Singulus Technologies AG, Blu-ray is being adopted faster than the DVD format was at a similar period in its development.This conclusion was based on the fact that Singulus Technologies has received orders for 21 Blu-ray dual-layer replication machines during the first quarter of 2008, while 17 DVD replication machines of this type were made in the same period in 1997.