Journal of the Optical Society of America · 1979 · 230 citations · 1 references
Optical MaterialsEngineeringWave OpticOptic DesignOptical TestingLaser ApplicationsOptical MetrologyDiffraction TheoryBeam OpticOptical PropertiesOptical Systemsλ/4-Deep PitsPhotonicsPhysicsApodized AperturesLaser Beam PropagationClassical OpticsLength ModulationGeometrical OpticApplied PhysicsOptical System AnalysisDiffractive Optic
The discs studied feature λ/4‑deep pits whose spacings and lengths are modulated along the track. The authors develop diffraction theory for this laser read‑out system, addressing both simple periodic and more complex disc structures. A high‑aperture objective focuses a laser beam onto the track, detects backscattered light, and the analysis includes focus‑error, aberrations, cross‑talk between tracks, and intermodulation of pit‑spacing and length‑modulation frequencies. They derive analytical formulas for the fundamental and harmonic read‑out signals and provide numerical results illustrating the effects of focus error and aberrations.
The form of discs considered has λ/4-deep pits along the track, the spacings and lengths of which are modulated. A laser beam is focused on the track by means of a high-aperture objective, and the light which is scattered back through the objective is detected. The diffraction theory of this system is treated, both for simple periodic and for more complicated forms of disc. Formulas are obtained for the fundamental and harmonics of the read-out signal. The influences of focus error and aberrations are studied, for certain cases of which numerical results are given. Also treated are cross-talk between adjacent tracks and intermodulation between the pit-spacing frequencies and those of the length modulation of the pits.
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