An optical head device for an optical disk apparatus for optically reading and writing information by irradiating a light spot onto an information recording surface of an optical recording medium, which is capable of moving an objective lens to a predetermined position even when part of the drive coil is included in an neutral area n in the vicinity of the magnetic boundary. There are provided two driving force generating units, including two magnets 50a and 50b disposed in the tangential direction of an optical disk separately on the opposite sides of an objective lens 10, and coil units 60a and 60b for generating the driving force directed against the magnets 50a and 50b disposed on a lens holder 20, and the magnets 50a and 50b and the coil units 60a and 60b are arranged in such a manner that the driving force other than the driving force generated for tracking movement and the moment act against each other at the two driving force generating units.

 
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> System and method for using timestamps to detect attacks

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