Patent ID: 7280453
Filing Date: 2007-10-09
Classification: G11B

Abstract:
1. A drive for reading and/or writing data from/on an optical data storage medium loaded, including a first data storage layer and a second data storage layer that are stacked in this order from the surface thereof toward the depth thereof, by radiating light through the surface toward the depth of the optical data storage medium, the drive comprising: a light source for emitting the light; a lens for producing a focal spot by converging the light that has been emitted from the light source; a light detector, which includes at least one photodetector for receiving the light and generating a light quantity signal representing quantity of the light received, the at least one photodetector being used as a layer-sensing photodetector that is designed so as not to receive the light reflected from the second data storage layer when the focal spot is located on the first data storage layer and so as to receive the light reflected from the first data storage layer when the focal spot is located on the second data storage layer; and a layer sensor for determining, in accordance with the light quantity signal representing the quantity of the light received at the layer-sensing photodetector, where the focal spot is now located, on the first data storage layer, on the second data storage layer, or in the vicinity thereof.