Objective Lens Multi-Format Compatibility Aberration Control
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Solution Overview
Problem
Existing optical pickup devices face challenges in achieving compatibility with Blu-ray, DVD, and CD discs using a common objective lens, as previous solutions suffer from high-order aberrations due to temperature and wavelength changes, and difficulties in balancing diffraction efficiency and manufacturing errors.
Innovation Solution
A single objective lens with a central, intermediate, and peripheral region, utilizing blazed structures in the central and intermediate regions to manage diffraction orders and pitch relationships, ensuring continuous spherical aberration and inhibiting high-order aberrations, while maintaining high diffraction efficiency across different wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common objective lens is used for BD, DVD, and CD optical discs, then device complexity and cost are reduced, but high-order aberrations occur due to temperature and wavelength changes
Solution Approach 1:
The objective lens is divided into three distinct regions: a central region for BD compatibility, an intermediate region for DVD compatibility, and a peripheral region for CD compatibility. Each region has independently optimized diffraction structures that address the specific aberration characteristics of each disc type, allowing the single lens to maintain high reliability across all three disc formats without requiring multiple separate optical systems
Solution Approach 2:
Each region of the objective lens is赋予 different local optical properties: the central region uses a first diffraction structure optimized for BD wavelengths, the intermediate region uses a second diffraction structure optimized for DVD wavelengths, and the peripheral region uses a third diffraction structure optimized for CD wavelengths. This local differentiation allows the lens to maintain optimal performance for each disc type while remaining a single integrated component
2Adaptability or versatility
If diffraction structures are designed for wavelength dependency of spherical aberration, then compatibility with multiple disc types is achieved, but manufacturing precision becomes difficult to control
Solution Approach 1:
The diffraction structures are segmented into three distinct zones with clearly defined boundaries. Each zone's diffraction pattern is independently designed and optimized for its specific disc type, which simplifies the manufacturing process by allowing each region to be fabricated and tested separately before integration into the complete lens assembly
Solution Approach 2:
The patent optimizes specific parameters of the diffraction structures including pitch ratios between regions, duty cycles, and grating depths to achieve the desired wavelength-dependent spherical aberration correction. By carefully controlling these parameters within specified ranges, the design achieves both multi-format compatibility and manufacturability
3Productivity
If the objective lens is optimized for high numerical aperture to increase recording capacity, then recording density improves, but coma aberration due to disc inclination increases
Solution Approach 1:
The objective lens employs different local diffraction structures in different regions to address the coma aberration problem. The central region's first diffraction structure is optimized for high NA BD operation with minimal coma, while the intermediate and peripheral regions use second and third diffraction structures respectively optimized for DVD and CD formats, each compensating for the specific coma characteristics of their target disc type
Solution Approach 2:
The diffraction structures are designed to dynamically adapt their optical function based on the wavelength and angle of incident light. When BD light enters the central region, the first diffraction structure provides the appropriate phase correction for high NA focusing. When DVD or CD light enters the intermediate or peripheral regions, the respective diffraction structures provide appropriate corrections, effectively making the static lens structure dynamically responsive to different operating conditions
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
The solution enables compatible recording and reproduction of Blu-ray, DVD, and CD discs with improved balance between wavelength and temperature properties, reducing manufacturing errors and maintaining high light use efficiency.
Implementation Method 1
utilizing blazed structures in the central and intermediate regions to manage diffraction orders and pitch relationships, ensuring continuous spherical aberration and inhibiting high-order aberrations
Data Source
AI summary
An objective lens for an optical pickup device is characterized in that compatibility of three types of optical discs, which are a BD, a DVD, and a CD, may be realized by a common objective lens, and a flare can be created by providing an over-spherical aberration when a third optical disc is used from a size relationship between a pitch on a central region side and a pitch on an intermediate region side across a boundary and a relationship of a direction of a step in the base structures superimposed in a central region and an intermediate region of the objective lens.