Optical disk with sector servo patterns compensating for variations in pattern size and/or radial velocity

An optical data storage system comprising:

• an optical storage disk divided into a plurality of circumferentially spaced sectors numbered in sequence, each even-numbered sector including a plurality of features, in the form of depressions or embossments, in a preselected ordered pattern which constitutes a permutation of their arrangement in each intervening odd-numbered sector;
• laser means for directing a spot of coherent light at selectable tracks on the disk during rotation of the disk;
• a single photodetector for sensing, during rotation of the disk, the change in amplitude of light reflected from the disk as the spot passes over one of the features for generating a position sensing signal corresponding to the pattern;
• and
• means for generating for each sector, from the light reflected, at least three phases of the position sensing signal, each of which phases for a particular sector is determined by adjacent concentric edges on the disk offset circumferentially with respect to each other and separated radially from each other by a preselected distance that is chosen to optimize linearity of the position sensing signal for a preselected size of said spot and is independent of the pitch of said tracks so as to provide a track error signal that is substantially linear within a desired range to either side of a point at which the track error signal changes polarity.

An optical data storage system comprising:

• an optical storage disk divided into a plurality of circumferentially spaced sectors numbered in sequence, each even-numbered sector including a plurality of features, in the form of depressions or embossments, in a preselected ordered pattern which constitutes a permutation of their arrangement in each intervening odd-numbered sector;
• laser means for directing a spot of coherent light at selectable tracks on the disk during rotation of the disk;
• a single photodetector for sensing, during rotation of the disk, the change in amplitude of light reflected from the disk as the spot passes over one of the features for generating a position sensing signal corresponding to the pattern;
• and
• means for generating for each sector, from the light reflected, at least three phases of the position sensing signal, each of which phases for a particular sector is determined by said two pairs of equally radially spaced concentric edges on the disk, the concentric edges of each pair being offset circumferentially with respect to corresponding edges of the other pair, and the edges of each pair being separated radially from the edges of the other pair by a preselected distance that is chosen to optimize linearity of the position sensing signal for a preselected size of said spot and is independent of the pitch of said tracks so as to provide a track error signal that is substantially linear within a desired range to either side of a point at which the track error signal changes polarity.

In an optical storage system, the combination of:

• an optical storage disk that has a plurality of recording tracks;
• means including laser means for directing a spot of coherent light at selectable tracks on the disk during rotation of the disk;
• said disk being divided into a plurality of circumferentially spaced sectors numbered in sequence, said sectors having imprinted servo patterns, each even-numbered sector comprising a plurality of features in the form of depressions or embossments constituting a permutation of the arrangement of such features in intervening odd-numbered sectors, said features being arranged in a preselected spot position sensing pattern defined in part by edges offset circumferentially with respect to each other and offset radially from each other by a preselected distance that is chosen to optimize linearity of a track error signal for a preselected size of said spot and is independent of the pitch of said tracks;
• a single photodetector for sensing, during rotation of the disk, the change in amplitude of light reflected from the disk as the spot passes over one of the features for generating a position sensing signal corresponding to the pattern, said single photodetector providing, for each of at least three phases of the position sensing signal, two amplitude signals separated in time according to circumferential distance between two adjacent ones of said features, and including
• means for calculating a position sensing signal for each of said phases by computing the difference in said two amplitude signals divided by the sum of said two amplitude signals;
• means including comparators for determining and selecting from said phases the one phase which is within its linear range;
• a counter;
• means for incrementing or decrementing the counter as the spot moves from said one phase to an adjacent phase during rotation of the disk;
• means for converting the output of the counter to an amplitude signal which together with the position sensing signal for the selected phase provides the track error signal;
• and
• means for generating, from the light reflected, at least three phases of the position sensing signal, each of which phases is determined by said edges so as to cause the track error signal to be substantially linear within a desired range to either side of a point at which said track error signal changes polarity.