For read-out of the twin beam/the optical data read-out which possesses the beam for writing/the writing device

摘要

The manner which makes the design of stationary state of the optical pickup unit (OPU) which gives two output beams (30 and 32), possible is proposed. It brings the spot where the both laser beams (30 and 32) have appropriate property, continue as the result. With the concept of this OPU, both of read-out spot and writing spot, being alienated by focus direction sufficiently, it exists simultaneously. This configuration makes that it changes to a state where it writes from a state where it reads out by introducing the appropriate focus offset in the electronic circuit, possible.