OPTICAL SCANNING DEVICE

摘要

A optical scanning device ( 1 ) for scanning an information layer ( 2 ) with a radiation beam ( 25 ) in a writing mode and a reading mode comprises a radiation source ( 7 ) for emitting the beam and an objective lens ( 10 ) for converging the beam so as to form a scanning spot ( 19 ) in the information layer. The device also includes a scanning spot power switch ( 20 ) for switching the size of the cross-section of the beam between a first size at the writing mode and a second, larger size at the reading mode so as to switch the rim intensity of the beam between a first intensity level (Irim,writing) at the writing mode and a second, higher intensity level (Irim,reading) at the reading mode, thereby switching the light power of the scanning spot between a first power level (Pwriting) at the writing mode and a second, lower power level (Preading) at the reading mode.