| 摘要 |
A focus error detector for an optical head utilizes a transmission type diffraction grating and an optical system for converging a beam issuing from a light source onto an object and converting light reflected from the object to a collimated beam to cause the collimated beam to become incident to the diffraction grating at a proper angle of incidence. A photodetector having a plurality of light-sensitive sections, is positioned relative to the grating such that it receives rays diffracted substantially from the grating in the direction of reflection of the diffraction grating. Photodetector data are used to calculate focus correction signals which are supplied to servo-mechanisms providing physical adjustments to the optical system.
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