Optical Pickup Phase Correcting Zones for Spherical Aberration
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Solution Overview
Problem
Conventional optical pickup devices face challenges in correcting spherical aberration when using a common objective lens for optical recording media with different wavelengths, numerical apertures, and substrate thicknesses, leading to exacerbated aberration during tracking and reduced flexibility in system configuration.
Innovation Solution
An optical pickup device with a common objective lens and phase correcting means, featuring concentric toric or disciform phase correcting zones and transparent regions with wavelength selectivity, ensures phase correction for each light beam without requiring a finite optical system, allowing for interchangeable mounting of optical recording media.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common objective lens is used for multiple optical recording media with different wavelengths, then device complexity is reduced, but spherical aberration correction becomes insufficient
Solution Approach 1:
The phase correcting element is divided into multiple independent phase correcting zones, each responsible for correcting spherical aberration for a specific wavelength. This segmentation allows the single element to handle multiple wavelengths effectively without requiring separate objective lenses for each medium.
Solution Approach 2:
Different regions of the phase correcting element are designed with different phase correction characteristics tailored to specific wavelengths. Each local zone optimizes correction for its designated wavelength, enabling the common objective lens to achieve precise focus across multiple optical recording media types.
2Manufacturing precision
If conventional phase correcting elements are used, then spherical aberration can be corrected for static conditions, but aberration exacerbates during tracking
Solution Approach 1:
The patent introduces dynamic compensation mechanisms that adapt to changes in optical conditions during tracking. The phase correcting zones are designed to maintain effective aberration correction even when the objective lens moves or when there are variations in the optical path, ensuring reliable performance throughout operation.
3Manufacturing precision
If a finite optical system is used to correct spherical aberration, then aberration correction is achieved, but flexibility in system configuration is reduced
Solution Approach 1:
The phase correcting element serves multiple functions simultaneously: it corrects spherical aberration for multiple wavelengths, maintains system compactness, and preserves configuration flexibility. This single component replaces what would traditionally require multiple separate elements, achieving universal applicability across different optical recording media types.
4Manufacturing precision
If separate optical systems are used for different wavelengths, then spherical aberration is corrected for each medium, but device complexity increases
Solution Approach 1:
Multiple phase correcting zones for different wavelengths are merged into a single phase correcting element. This integration maintains the aberration correction capabilities that would otherwise require separate optical systems, while significantly reducing overall device complexity and enabling the use of a common objective lens.
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 effectively corrects spherical aberration for multiple wavelengths, prevents aberration exacerbation during tracking, and enhances system flexibility by using a common objective lens with phase correcting elements that are integrated into a single piece, ensuring good point image light intensity distribution and reduced side lobes.
Implementation Method 1
the phase correcting means correct phases of the k light beams
Implementation Method 2
corrects spherical aberration for multiple wavelengths
Implementation Method 3
transparent regions having wavelength selectivity
Implementation Method 4
the light beam restriction means propagate each, of the k light beams
Implementation Method 5
a common objective lens which focuses the light beams radiated from the light emitting elements on the k optical recording media
Implementation Method 6
an optical system which transforms the light beams radiated from the light emitting elements into parallel light beams and guides the parallel light beams to the objective lens
Data Source
AI summary
An optical pickup device enables prevention of an increase of spherical aberration during tracking without needing any finite optical system. The diameters of parallel light beams (A, B, C) for the next-generation DVDs, DVDs, and CDs are limited to diameters of a, b, c (a>b>c) in accordance with the NA for each type by a light beam limiting element, the diameter of light beam B is limited to the diameter ranges of b to c and d (=0.85×c) to e (d>e>0), the diameter of the light beam C is limited to the diameter ranges of c to d and less than e. They are passed through a phase correcting element (13B) and focused on the corresponding optical recording medium signal planes by means of a common objective lens. The objective lens is so optimized that the wave front aberration to the light beam A is minimum on the signal plane of the next generation DVD. The phase correcting element (13B) has a phase correcting zones (Z1 to Z4) of diffraction optical structure exhibiting a pseudo-kinoform shape of a step constitution. The spherical aberration to the light beam B is corrected in the zones (Z1, Z3). The spherical aberration to the light beam C is corrected in the zones (Z2, Z4). The light beam A is passed through all the zones of the light beam diameter a without changing the parallel light beam state by optimizing the step heights of the zones (Z1 to Z4).