Variable Wavelength Laser Coherency Control for Holographic Recording
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Solution Overview
Problem
Existing optical information recording and reproducing apparatuses based on holography face challenges in maintaining high coherency and wavelength accuracy, particularly due to temperature variations and material expansion/shrinkage in photopolymer media, leading to fluctuations in light source power and wavelength, which affect signal quality and capacity.
Innovation Solution
The apparatus employs an external resonator type variable wavelength laser with finely adjustable wavelength and power, combined with an optical path length difference adjustment mechanism, to ensure high coherency in the recording mode and precise wavelength control in the reproducing mode, reducing fluctuations and enhancing signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable wavelength laser is used to compensate for photopolymer material expansion/shrinkage, then wavelength adaptability is improved, but wavelength accuracy deteriorates due to fluctuations
Solution Approach 1:
The patent employs a feedback control system where the actual wavelength of the laser is detected and compared with a reference wavelength. Based on the detection result, the laser wavelength is adjusted to match the reference wavelength, thereby compensating for fluctuations and maintaining high wavelength accuracy while using a variable wavelength laser for adaptability.
Solution Approach 2:
The patent changes the operating parameters of the laser by adjusting its temperature and driving current based on detected wavelength deviations. This dynamic parameter adjustment allows the laser to maintain accurate wavelength despite being a variable wavelength type, resolving the contradiction between adaptability and precision.
2Reliability
If high coherency is prioritized in the laser, then recording quality is improved, but wavelength control accuracy deteriorates
Solution Approach 1:
The patent dynamically adjusts the laser's operating conditions by independently controlling temperature and driving current. This dynamic control allows the system to optimize both coherency and wavelength accuracy simultaneously, rather than having to prioritize one over the other, resolving the technical contradiction through adaptive parameter management.
Solution Approach 2:
The patent changes the physical parameters of the laser (temperature and current) in a coordinated manner to achieve both high coherency and accurate wavelength control. By adjusting these parameters based on real-time detection, the system can maintain optimal performance for both recording quality and wavelength precision.
3Measurement precision
If temperature control is applied to stabilize laser wavelength, then wavelength accuracy is improved, but device complexity increases
Solution Approach 1:
The patent makes the temperature control mechanism serve multiple functions: it not only stabilizes the laser wavelength but also optimizes the laser's coherency and overall performance. This multi-functionality justifies the added complexity by providing benefits beyond simple wavelength stabilization.
Solution Approach 2:
The patent uses temperature as a controllable parameter to achieve wavelength stabilization. By implementing a temperature control mechanism that works in conjunction with current control, the system achieves high wavelength accuracy through a manageable level of complexity that is integrated into the laser's operation.
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 stabilizes the coherency and wavelength accuracy, enabling reliable high-capacity recording and reproducing with improved signal quality and reduced fluctuations in the reproducing mode, while allowing for efficient data storage and retrieval.
Implementation Method 1
a laser having a high coherency is required as a light source
Implementation Method 2
In order to cope with expansion/shrinkage of the photopolymer material caused by variations in the temperature of the material
Implementation Method 3
In order to stable secure a high coherency in the external resonator type of variable wavelength laser, it is necessary to finely adjust its wavelength and power
Data Source
AI summary
An optical information recording/reproducing apparatus for recording an interference pattern between signal light and reference light information-multiplexed as a hologram in an optical information recording medium and for reproducing information recorded in the optical information recording medium on the basis of the recorded hologram with use of the reference light. The apparatus includes a light source for emitting light and a coherency controller for controlling a coherency of the light source. The apparatus controls the coherency controller in such a manner as to switch between a coherency required in a recording mode and a coherency required in a reproducing mode.