Spatial Light Modulator Phase Multiplexing Holographic Storage
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Solution Overview
Problem
Conventional holographic data storage systems face limitations in data resolution and storage capacity due to mechanical indexing requirements and the need for high precision, which also reduces reliability and increases the complexity of data retrieval.
Innovation Solution
A spatial light modulator system capable of modulating both amplitude and phase of light, allowing for phase multiplexing and increased resolution, eliminating the need for mechanical indexing by using phase modulation to store multiple pages in the same physical volume of the storage medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If angular multiplexing is used to store multiple hologram pages, then storage capacity is improved, but mechanical indexing precision and reliability deteriorate
Solution Approach 1:
The patent replaces the mechanical indexing system with an optical phase modulation system. Instead of using mechanical devices to physically index and retrieve specific hologram pages, the invention uses a spatial light modulator to apply phase codes to the reference beam, enabling non-mechanical access to stored data pages through optical interference patterns.
Solution Approach 2:
The patent changes the parameter used for multiplexing from angular position (mechanical) to phase modulation (optical). By encoding multiple hologram pages with different phase codes on the reference beam, the system achieves angular multiplexing functionality without mechanical movement, improving both reliability and access speed.
2Measurement precision
If pixel size is reduced to increase resolution, then data resolution is improved, but contrast and reliability deteriorate
Solution Approach 1:
The patent changes the modulation parameter from amplitude-only to complex amplitude (including phase). By modulating both the amplitude and phase of the reference beam, the system can encode more information per pixel and maintain higher contrast even when pixel size is reduced, thereby improving resolution without sacrificing reliability.
Solution Approach 2:
The patent adds the phase dimension to the traditional amplitude modulation. Instead of only varying the intensity (one dimension) of the reference beam, the system now varies both amplitude and phase (two dimensions), effectively doubling the information capacity per pixel and enabling higher resolution storage with maintained contrast.
3Device complexity
If conventional amplitude modulators are used, then device complexity is reduced, but storage density and retrieval speed deteriorate
Solution Approach 1:
The patent changes the modulation capability from amplitude-only to complex amplitude modulation. The spatial light modulator now controls both the magnitude and phase of the reference beam, enabling phase multiplexing and increasing storage density without significantly increasing device complexity, as the same SLM hardware can perform both amplitude and phase modulation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances data storage density, improves retrieval reliability, and extends the life of the storage medium by enabling non-mechanical multiplexing and increased resolution, reducing the need for precision mechanical devices and improving access times.
Implementation Method 1
the SLM can modulate both the amplitude and phase of light from every pixel on the SLM
Implementation Method 2
beam-forming optics for forming the light into collimated object and reference beams
Implementation Method 3
the reference beam and the object (or data) beam interfere inside the recording volume of a holographic storage medium
Implementation Method 4
The storage medium will diffract the reference beam reconstructing the stored object beam
Data Source
AI summary
A holographic data storage (HDS) system and method are provided. Generally, the system includes: a light source for generating a coherent light; beam-forming optics for forming the light into collimated object and reference beams; holographic storage medium; a spatial light modulator (SLM) located in a path of the object beam from the beam-forming optics to the storage medium, the SLM having a number of pixels for encoding data to be stored in the medium into the object beam. Preferably, the SLM can modulate both the amplitude and phase of light from every pixel on the SLM. More preferably, the SLM is also located in a path of the reference beam to the storage medium to modulate the phase of the light to store multiple holographic pages of data in the same physical volume of medium through phase multiplexing. Other embodiments are also described.