According to report by Tech-On, Sony recently presented their results
on four-layer Micro-Reflector recording at this year's ODS meeting. A type of holographic recording, Micro-Reflector irradiates a disc
on both sides, creating a set of virtual layers. Sony claims that this method is affected less by heat and is cheaper implement due to
the use of existing blue-violet laser diodes.
In the Micro-Reflector recording, light beams are irradiated on both sides of
the recording medium. Two light beams are then interfered on the recording layer by aligning their focal points, thereby recording an
interference fringe which corresponds to 1-bit information capacity. The information is reproduced by emitting light on the front side of
the medium. Interference fringes with different depths can be recorded by changing the depth of the focal points as in the case of
recording on a multilayered medium.
In addition to multilayer recording, the company points out advantages in that the method is
less likely to be influenced by the expansion/contraction of photopolymer due to heat, thus preventing signal reading errors. This is
because the interference fringes are smaller than those used in other holographic recording methods where recording is performed on a
page basis. The company expects that the Micro-Reflector system will easily facilitate reductions in equipment cost because it can
utilize existing blue-violet semiconductor laser diodes and eliminate the need of a spatial phase modulator, CMOS sensor or other parts.
Micro-Reflector isn't without its problems. Along with slow data transfer rates, Sony has found that when recording to
deeper layers, the signal gets weaker. Once Sony resolves these problems, they plan to introduce 20 layer discs with a total capacity of
500GB. If you'd like to read more, Tech-On's entire report can be found here.
