OPTICAL SCANNING DEVICE

摘要

An 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.