Optical Pickup Device Coma Aberration L2 Playback
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Solution Overview
Problem
Existing optical pickup devices face challenges in improving playback performance, particularly in the L2 layer of triple-layer structure Blu-ray discs, due to issues with jitter and coma aberration.
Innovation Solution
The optical pickup device incorporates a semiconductor laser and an object lens with an inclined optical axis to generate coma aberration on the entrance side of pits, utilizing a diffraction element with a first diffraction grating that corrects the laser beam's intensity distribution to reduce the optical spot size, thereby enhancing playback performance in the L2 layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the optical axis of the object lens is aligned with the optical axis of the laser beam, then coma aberration is minimized, but playback performance in the L2 layer deteriorates due to increased jitter
Solution Approach 1:
The patent intentionally introduces coma aberration by inclining the object lens optical axis relative to the laser beam optical axis. This harmful aberration is converted into a beneficial effect that improves playback performance in the L2 layer by reducing jitter, demonstrating the principle of converting a harmful factor into a useful one.
Solution Approach 2:
The patent changes the parameter of optical axis alignment by introducing a specific inclination angle between the object lens optical axis and the laser beam optical axis. This parameter change optimizes the coma aberration to improve L2 layer playback performance while managing its impact on other layers.
2Reliability
If coma aberration is increased to improve L2 layer playback, then jitter is reduced, but performance in L0 and L1 layers may deteriorate
Solution Approach 1:
The patent applies local quality by optimizing the optical system specifically for the L2 layer through controlled coma aberration, while using layer-specific correction strategies to maintain acceptable performance in L0 and L1 layers. The diffraction element with asymmetric grating provides localized correction tailored to different layer requirements.
Solution Approach 2:
The patent employs dynamic adjustment mechanisms including layer-specific correction values and adjustable diffraction element configurations that adapt the coma aberration compensation based on which layer is being read, allowing optimization for L2 while preserving L0 and L1 performance.
3Measurement precision
If a diffraction element with asymmetric grating is added to correct intensity distribution, then optical spot size is reduced, but device complexity increases
Solution Approach 1:
The patent merges the coma aberration compensation function with the intensity distribution correction function into a single integrated optical path design. The diffraction element with asymmetric grating simultaneously addresses both issues, reducing the need for separate correction components and minimizing overall system complexity.
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 configuration effectively improves playback performance in the L2 layer of triple-layer structure Blu-ray discs by optimizing the optical spot size and reducing Integrated-Maximum Likelihood Sequence Estimation (i-MLSE) error rates, while maintaining performance in the L0 and L1 layers.
Implementation Method 1
an object lens that concentrates the laser beam on an optical disc
Implementation Method 2
a diffraction element having an asymmetric grating structure with respect to an optical axis of the laser beam
Implementation Method 3
utilizing a diffraction element with a first diffraction grating that corrects the laser beam's intensity distribution
Implementation Method 4
an optical axis of the object lens is inclined with respect to an optical axis of the laser beam that is incident on the object lens so as to generate flares caused by coma aberration
Data Source
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AI summary
An optical pickup device capable of improving playback performance in L2-layer at a time of playback of a triple-layer structure optical disc is provided. The optical pickup device includes a semiconductor laser that emits a laser beam, and an object lens that concentrates the laser beam emitted from the semiconductor laser on the optical disc. In this optical pickup device, an optical axis of the object lens is inclined with respect to an optical axis of the laser beam that is incident on the object lens so as to generate flares caused by coma aberration on an entrance side in a forward direction of pits of the optical disc.