Since the arrival of Blu-ray, many manufacturers started to try to increase the capacity of these media to exceed the 50 GB offered by two layers. Essentially, the increase is dependent on increasing the number of layers to 4,8 and even 10. But even though these achievements are possible in laboratory, they are delicate to implement since it is necessary to make the layers transparent enough to let the light from the laser pass through and at the same time make it opaque enough so that the light is reflected. In addition, one has to create a system that allows focusing of the laser with enough precision on a given layer so that a clear signal is recovered and that is not parasitized too much by the reflections from the adjacent layers. Another approach that is easier to implement is now proposed. A document presented at the time of the International symposium of the optical storage held last October in Nagasaki, Japan, described a new method allowing the increase of the capacity of each layer t
