Holographic Memory Reference Beam Angle Adjustment
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Solution Overview
Problem
Existing holographic recording technologies face challenges in accurately adjusting the incident angle of the reference beam, leading to deteriorated reproduction quality and inability to adjust the angle when a hologram is not previously recorded, especially when the disk is tilted.
Innovation Solution
The optical information recording/reproducing apparatus includes a mechanism to accurately adjust the incident angle of the reference beam using a galvanometer mirror and optical detectors to calculate and correct the angle shift, allowing for precise alignment without the need for prior hologram recording, even when the disk is tilted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SNR-based adjustment method is used to estimate optimum incident angle, then reproduction quality can be evaluated, but the method requires pre-recorded holograms and cannot adjust angle when hologram is not yet recorded
Solution Approach 1:
The patent introduces a light quantity detection circuit as an intermediary device that detects the light quantity of reference beam reflected from the recording medium surface. This intermediary measurement method enables incident angle adjustment without requiring pre-recorded holograms, solving the adaptability problem while maintaining measurement precision through optical feedback.
2Measurement precision
If offset angle is intentionally added for SNR detection, then variation in SNR can be detected, but reproduction quality is always deteriorated due to angle shift from optimum
Solution Approach 1:
The patent extracts the light quantity detection function from the reproduction process and applies it specifically to incident angle adjustment. By separating the angle detection function from the reproduction quality evaluation, the system can accurately measure and adjust the incident angle without introducing offset angles that would deteriorate reproduction quality.
Solution Approach 2:
The system uses the reflected reference beam itself to provide feedback for angle adjustment, rather than requiring separate test signals or pre-recorded holograms. The light quantity detection circuit measures the reflected light to generate feedback signals that automatically adjust the reference beam angle to the optimum position.
3Manufacturing precision
If angle detection signal is used to adjust reference beam angle, then angle alignment can be achieved, but the method does not reflect disk tilt and cannot strictly estimate relative tilt
Solution Approach 1:
The patent implements a feedback mechanism where the light quantity detection circuit continuously monitors the reflected reference beam light quantity and generates feedback signals to the reference beam angle adjuster. This closed-loop feedback system automatically compensates for disk tilt by adjusting the reference beam angle to maintain optimal alignment, eliminating the harmful effect of disk tilt on recording precision.
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 solution enables accurate adjustment of the reference beam angle, improving hologram reproduction quality and enabling angle adjustment without pre-recorded holograms, thus enhancing the capacity and efficiency of holographic storage.
Implementation Method 1
a mechanism to accurately adjust the incident angle of the reference beam using a galvanometer mirror
Implementation Method 2
optical detectors to calculate and correct the angle shift
Data Source
AI summary
A holographic memory apparatus includes an optical detector which receives reflected light of reference beam from the surface of a hologram recording medium. An incident angle of the reference beam is estimated on the basis of information on a focused position on the optical detector. When the incident angle is different from a target incident angle, the incident angle of the reference beam is adjusted according to a difference between the incident angle and the target incident angle.