| 摘要 |
<p>Apparatus useful in maintaining focus in a disk data-storage system, comprising: a radiation source (10) for producing a read/write beam of radiation; controllable focus means including an objective lens system (18) for focusing said read/write beam on the disk, a portion of said read/write beam being reflected form the disk to produce a reflected beam (129); an optical element (130) for simultaneously producing from said reflected beam, first (135) and second (136) beams, said first beam at a detector plane having at least a portion non-overlapping in relation to said second beam; first detector means (a,b,c and d) at said detector plane for producing a first signal related to said first beam (135); second detector means (e,f,g and h) to produce a second signal related to said second beam; (136) and electronic means for combining said first signal and said second signal to produce a third signal, said third signal being related to said degree of focus and said third signal being substantially constant in response to optical faults.</p> |
