Holographic Memory Reproduction via Phase-Modulated Interference
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Solution Overview
Problem
Holographic memory systems face challenges in efficiently recording and reproducing multi-valued phase information due to noise interference and limitations in detecting phase modulation signals, which restricts the recording capacity and accuracy.
Innovation Solution
A holographic memory reproduction apparatus that produces a second hologram from diffracted light of a recorded hologram and reference light, allowing for precise demodulation of spatial phase modulation signals or spatial quadrature amplitude modulation signals by detecting intensity distributions and processing them to extract phase information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If phase modulation signals are used to increase recording capacity, then the recording capacity is improved, but the detection accuracy deteriorates due to noise interference and inability to directly detect phase signals
Solution Approach 1:
The patent introduces a local oscillator signal as an intermediary to convert the undetectable phase modulation signal into a detectable intensity signal. The local oscillator interferes with the signal light containing phase information, and through photodetection, the phase information is extracted as intensity variations. This intermediary conversion process enables accurate detection of phase signals that cannot be directly measured.
Solution Approach 2:
The patent replaces direct phase detection (which is impossible with conventional detectors) with an intensity-based detection system. By using optical interference to convert phase information into intensity variations, the system substitutes an unworkable direct measurement approach with a workable indirect measurement approach that uses intensity detection to infer phase information.
2Ease of manufacture
If conventional intensity modulation is used, then the system construction is simple, but the exposure intensity difference between central and peripheral portions causes dynamic range consumption and reduced recording efficiency
Solution Approach 1:
The patent changes the modulation parameter from intensity modulation to phase modulation. Instead of varying the intensity of light to encode information, the system varies the phase of the light wave. This parameter change eliminates the exposure intensity difference problem because phase modulation maintains more uniform intensity distribution across the beam profile, thereby improving recording efficiency without significantly complicating the system.
3Quantity of substance
If multi-valued intensity signals are used to increase code rate, then the recording capacity is improved, but the signal-to-noise ratio deteriorates due to detection system accuracy and noise
Solution Approach 1:
The patent uses a local oscillator signal as an intermediary to enable reliable detection of multi-valued phase signals. The local oscillator provides a strong reference signal that interferes with the weak signal containing phase information. This interference process amplifies the signal components and allows the detection system to resolve multiple phase levels with high signal-to-noise ratio, enabling multi-valued modulation without sacrificing reliability.
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
Enables accurate reproduction of multi-valued phase information without noise interference, enhancing the recording capacity and accuracy of holographic memories.
Implementation Method 1
a hologram diffracted light production section that produces diffracted light of the first hologram by irradiating the holographic memory with first reference light
Implementation Method 2
a hologram production section that changes a phase of second reference light capable of interfering with the diffracted light of the first hologram, and produces a second hologram from the diffracted light of the first hologram and the second reference light of which the phase is changed
Data Source
AI summary
The present invention relates to a reproduction device of a holographic memory capable of precisely reproducing multi-value phase information without being influenced by noise. This holographic memory reproduction device comprises: a hologram diffraction ray generation unit which irradiates a first reference ray to the holographic memory and generates a diffraction ray of the first hologram; a hologram generation unit which changes the phase of a second reference ray which may interfere with the diffraction ray of the first hologram and generates a second hologram from the diffraction ray of the first hologram and the second reference ray to which the phase has been changed; a detection unit which detects the intensity distribution of the second hologram; and a processing unit which demodulates the phase modulation signal or the space quadrature amplitude modulation signal on the basis of the intensity distribution.