| 摘要 |
PURPOSE:To measure the speed change of the reflectivity of a recording material at the time of writing and erasure, by providing a laser beam irradiation means, a laser beam irradiation condition setting means and a reflectivity measuring means to an object to be irradiated. CONSTITUTION:When the switch of an operation panel 18 is closed, the power setting signal of reading laser beam is outputted to a power control circuit 11 from the panel 18 and power is further stabilized by an LD control circuit 10 and reading laser beam is allowed to irradiate from the semiconductor laser 8 in an optical pickup 1. Next, when the switch on the panel 18 is closed, a focus servo circuit 9 functions to move the actuator 4 in the pickup 1 and an objective lens 7 is moved to match the focus thereof with an object 3 to be irradiated. Subsequently, when a start signal is outputted to a pulse timing circuit 13 from the panel 18, a writing/erasure timing signal is simultaneously outputted to the circuit 11 and a pulse width control circuit 12 from the circuit 13. The circuit 10 receiving said signal allows pulse beam to irradiate from the laser 8 and writing/erasure is performed to the same place of the sensitive material of the object 3 to be irradiated. |
