Optical Head Design for Multi-Disk Compatibility
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Solution Overview
Problem
Existing optical information processors face challenges in reducing the size of the optical head while maintaining stability and compatibility with multiple optical disk types, including high-density disks like BDs and HD-DVDs, due to insufficient gap between objective lenses, interference issues, and the need for efficient spherical aberration correction.
Innovation Solution
The optical head design incorporates a condenser lens to enhance light intensity monitoring, a vertical reflecting prism for compactness, and a drive motor to correct spherical aberration, allowing for stable read/write operations on multiple disk types with high numerical aperture objective lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple objective lenses are provided for high-density optical disks, then storage density increases, but the gap between lenses becomes insufficient and device size increases
Solution Approach 1:
The patent combines multiple objective lenses (first and second objective lenses with different numerical apertures) into a single optical head assembly that can be positioned close to the disk surface. The lenses are integrated with common optical components (collimator lens, beam splitter, photodetector) to share space efficiently, reducing the overall optical head volume while maintaining high storage density capability.
Solution Approach 2:
The patent arranges optical components in a nested configuration where the first and second objective lenses are positioned at different heights along the optical axis, with intermediate optical elements (collimator lens, beam splitter) nested between them. This layered nesting allows multiple lenses to coexist in a compact vertical space, minimizing the gap requirements while maintaining optical performance.
2Quantity of substance
If blue laser beam with wavelength of 405 nm is used, then storage density increases five times, but heat generation increases causing stability issues
Solution Approach 1:
The patent introduces a beam splitter as an intermediary optical element that divides the blue laser beam into separate optical paths for the first and second objective lenses. This allows the high-density blue laser light to be distributed and utilized efficiently across multiple storage layers, reducing concentrated heat generation at any single point while maintaining high storage density.
Solution Approach 2:
The patent segments the blue laser beam path into multiple independent optical channels using the beam splitter, with each channel serving a different objective lens for different disk types. This segmentation distributes the optical energy and heat generation across multiple paths, preventing localized overheating while enabling high-density storage operations.
3Quantity of substance
If numerical aperture of objective lens is increased to 0.85, then spot size decreases for high density, but working distance becomes too short for DVD/CD compatibility
Solution Approach 1:
The patent assigns different numerical aperture characteristics to different objective lenses based on their specific functions: the first objective lens has NA=0.85 optimized for high-density BD/HD-DVD with short working distance, while the second objective lens has NA=0.6 optimized for DVD/CD with longer working distance. Each lens is locally optimized for its target disk type, and the system switches between them based on the inserted disk.
Solution Approach 2:
The patent creates a universal optical head that can handle multiple disk types (BD, HD-DVD, DVD, CD) by providing multiple objective lenses with different numerical apertures. The system maintains compatibility across all disk formats by selecting the appropriate lens for each disk type, achieving multi-functionality without compromising the high-density performance of the NA=0.85 lens for BD/HD-DVD.
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 design achieves stable and high-frequency light intensity monitoring, reduces the optical head's size, and enables efficient read/write operations on high-density disks without significant temperature increase, ensuring compatibility with various storage densities.
Implementation Method 1
a first collimator lens for changing degrees of divergence of the first light beam
Implementation Method 2
a first objective lens for converging the first light beam, which has had its traveling directions changed, toward a storage layer of a first optical disk
Implementation Method 3
a condenser lens for condensing the second light beam
Implementation Method 4
a first photodetector that receives the first light beam that has been reflected from the storage layer of the first optical disk and converts the first light beam into an electrical signal
Implementation Method 5
a second photodetector that receives the second light beam that has been condensed by the condenser lens and converts the second light beam into an electrical signal
Implementation Method 6
a vertical reflecting prism for compactness
Data Source
AI summary
An optical head according to the present invention includes: a first light source that emits light with a first wavelength; a beam splitter that splits the light emitted from the first light source into a first light beam traveling in a first direction and a second light beam traveling in a second direction different from the first direction; a first collimator lens for changing degrees of divergence of the first light beam; a first mirror that changes the traveling directions of the first light beam, of which the degrees of divergence have been changed; a first objective lens for converging the first light beam, which has had its traveling directions changed, toward a storage layer of a first optical disk; a mover that holds the first objective lens; a first photodetector that receives the first light beam reflected from the storage layer of the first optical disk and converts it into an electrical signal; a condenser lens for condensing the second light beam; and a second photodetector that receives the second light beam condensed by the condenser lens and converts it into an electrical signal.