The data are stored in the alternative pits and lands for present optical disk, which is similar to the grating. Accordingly, the grating theory becomes the basis theory for the optical disk. The work presented in this paper focused on several aspects of the following: outlining the optical disk models adopted by the theories in print, analyzing the foundation basis of the models, and bringing forward a model which can be used for the new-fashioned optical storage, multi-wavelength photochromic optical storage. The classical scalar diffraction theory supposed that the effects of the optical disk on the incident beam were introducing the local phase delay that could be described by the optical path difference Δ<i>s</i>, and the energy of the incident beam would not be absorbed. The two equations could respectively express the difference of the optical path: (1) Δ<i>s</i>=<i>n</i>*Δ<i>h</i> and (2) Δ<i>s</i>=Δ<i>n</i>*<i>h</i>. As the result of the analysis, we concluded that the tradition optical disk model fit for pit-land recording format and the cavity or bubble recording format. For the photochromic optical disk, the recording material, which absorbed the energy of the incident beam, was similar to the amplitude grating. The diffraction theory of this system was presented, and the equations for the readout signal were educed.
The diffraction theory, which includes scalar and vector diffraction theory, is an important basal theory in the field of optical storage. The purpose of this paper is to analyze the needs of using vector diffraction theory instead of scalar diffraction theory in the study of the digital versatile disk (DVD) or other high-density optical disks, and summarizes the effects of the optical disk pattern parameters on the readout signals. The grating is adopted as the physical model of optical disk in this research. And the readout signals are calculated only versus some parameters, involving the transverse dimensions, the depths and the slopes, of the information marks with vector diffraction theory. Accordingly some key factors to guarantee the optical disk manufacture quality are put forward, and these factors resulted from this study may be useful to improve the optical disk manufacture technica, furthermore, the vector analysis methods adopted herein are referable to higher density optical storage research.