Optical disk unit
AssigneeKabushiki Kaisha Toshiba
InventorsTamane Takahara, Hideaki Osawa, Naobumi Seo
Life of this patent
Estimating the term…
Abstract
An optical disk unit having a light spot incident upon an optical disk. The light spot is radially moved to cross tracks formed on the optical disk. The tracks are provided with specific access marks. The number of access marks passed by the light spot as well as the number of tracks crossed by the light spot until a change is found in a detected access mark are counted. The latter number is divided by the former number and multiplied by a coefficient to provide a speed signal indicative of a speed of the light spot relative to the optical disk.
Claims8
An optical disk unit for transmitting a light spot upon a surface of an optical disk provided with concentrical or spiral tracks on which a plurality of sample servo pits involving access marks specific for every predetermined number of tracks are formed, and detecting said access marks to recognize a moving state of said light spot on said optical disk, said optical disk unit comprising:
- access mark pattern storage means for storing both access mark patterns corresponding to said access marks formed on said tracks and combined access mark patterns, said combined access mark patterns representing combinations of said access marks formed on adjacent tracks;
- and
- position detecting means for checking to see whether a detected access mark pattern matches one of said access mark patterns and said combined access mark patterns stored in said access mark pattern storage means, and for determining that said light spot is located between two adjacent tracks when a detected access mark pattern matches one of said combined access mark patterns stored in said access mark pattern storage means.
A method of determining movement characteristics of a light spot upon the surface of an optical disk having a plurality of tracks, said method comprising the steps of:
- storing a predetermined number of unique access mark patterns in a memory;
- dividing said plurality of tracks into groups, a number of tracks in said groups being equal to said predetermined number;
- marking said optical disk on each track in each of said groups with an access mark corresponding to one of said unique access mark patterns;
- additionally storing combination access mark patterns in said memory, each of said combination access mark patterns corresponding to a combined pattern of two of said access marks, said two of said access marks being marked on two adjacent tracks;
- detecting a first access mark and storing a first detected access mark pattern representative of said first access mark;
- checking whether said first detected access mark pattern matches one of said access mark patterns in said memory and checking whether said first detected access mark pattern matches one of said combination access mark patterns stored in said memory;
- and
- determining a first relative position of said light spot when said checking step indicates a match of said first detected access mark pattern, wherein when said first detected access mark pattern matches one of said combination access mark patterns corresponding to said combined patterns of said two of said access marks, said light spot is located between said two adjacent tracks.
Dependencies are inferred from the claim text.