Infinity Storage Media has released the first Blu-Ray/DVD hybrid disc in Japan. According to My Digital Life,
The new technology, which embeds both Blu-ray and DVD compatible contents on the same disc is believed to be able to smoothen the migration process from DVD to most desired full HD (High Definition) Blu-ray standard especially for those users that still stick with existing DVD standard.
The benefit is obvious, now users will be able to run the same copy of DVD disc in both conventional DVD players and Blu-ray players without worrying about the old favorite movies compatibility with new Blu-ray machines. The mechanism behind is it is based on the different laser wavelength that can penetrate into different layers (isolated by semi-reflective film) embedded in the disc to read DVD and Blu-ray media contents respectively. For instance, it reflects blue light on upper layer for Blu-ray contents readings while able to pass through red light to the DVD layer underneath.
I’m not sure if there will be performance impact compared to using either just Blu-Ray or DVD.