Using Optical Guidance for a Hard Disk Drive Head Assembly
Original Publication Date: 2001-Aug-01
Included in the Prior Art Database: 2003-Jun-20
Disclosed is a method for optically guiding the read/write head for a computer hard disk drive. Rather than relying on the drive head assembly motor to position the drive head over the drive surface, the proposed method uses a low-power laser to read the current drive-head position and guide the drive head assembly to the proper position above the drive surface using a servo-controller in the motor. The preferred implementation adds a very thin reflective polymer substrate to the surface of the hard disk drive. This substrate is magnetically and electrically neutral so that it cannot interfere with the drive heads and cannot induce spurious magnetic fields. By using a low-power laser to read predefined patterns in the substrate, it can accurately determine its position relative to the substrate. By adding a servo-controller to the hard-disk drive motor that responds to the position data from the laser, the drive head can be positioned with greater accuracy. In addition to reading the horizontal (x-y, r-theta) position of the drive head, the preferred implementation also splits the beam so that the laser can also read the vertical (z) position of the drive head, thus allowing the drive head to adjust the magnetic field applied while reading and writing data on the drive surface. Such accuracy in the x-y (r-theta) position increases the density of data that can be read and written to the disk. The increased accuracy in the z position, in addition to increasing the density of the data that can be read and written, can also reduce the spread in the data track. As a possible improvement to the preferred implementation, the substrate could contain read-only data, in addition to the position markers. Such read-only data could represent computer ROM data, such as BIOS or operating system extensions. It could also represent physical drive characteristics, such as track numbers and so on. Or it could store manufacturer-supplied encryption keys or digital certificates for secure authentication.