Analytic function expression of signal wave for data retrieve in holographic data storage (Conference Presentation)

Abstract

Holographic data storage is a data storage with large data amount recorded by volume holography. Holography is well known as a method to record three-dimensional scenes. The principle is roughly established and major characteristics are well understood. In the case of three-dimensional scenes, some noises are acceptable because they are compensated by our brain. However, in the case of holographic data storage, the recording images are minute two-dimensional coded patterns so that the images are not robust for noises. Therefore, rigorous expressions of recording signal is required. In this study, the recording signal wave is expressed by Taylor expansion for small argument and asymptotic expansion for large argument. Then, the filling factor of pixels in a spatial light modulator (SLM), the size and the position shift of a rectangular aperture at a Fourier plane are considered. When the signal wave is ideally reconstructed, the signal wave at an image plane is captured by using an image sensor. Then, the signal wave is integrated by the area of pixels in the image sensor. In this study, the integral is analytically calculated whereas it is numerically calculated in general because the signal wave is expressed by analytic functions. Therefore, interpixel crosstalk is easily evaluated. In our previous study, high-density recording method of binary data pages is proposed by using four-step phase mask. The high-density recording characteristics are evaluated by analytic functions. When parameters such as the filling factor of pixels in a SLM and an image sensor and the size and the position shift of a rectangular aperture can be known, the analytic functions are obtained. Then, the analytic functions are expected for error corrections.