Optical Head Device for Multi-Format Disk Reading
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Solution Overview
Problem
Existing optical head devices face challenges in achieving interchangeable recording and reproduction of optical information media with different substrate thicknesses and recording densities, leading to aberrations and reduced miniaturization due to the need for multiple objective lenses and complex mechanisms.
Innovation Solution
The optical head device employs a dichroic polarization separation film, ¼ wavelength plates, and reflective surfaces to convert and focus light beams of different wavelengths, allowing for interchangeable recording and reproduction across various optical disks with different substrate thicknesses, while maintaining compactness and reducing aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the numerical aperture (NA) of the focusing optical system is increased to achieve higher recording density, then the recording density is improved, but the aberration due to slanting of the light axis (tilt) increases
Solution Approach 1:
The patent changes the physical parameter of substrate thickness to compensate for aberrations. By adjusting the substrate thickness, the optical path length is modified to correct spherical aberrations caused by high NA focusing, thereby maintaining recording precision while achieving high density
2Manufacturing precision
If the substrate thickness is thinned to prevent aberration from increasing with higher NA, then the aberration is reduced, but the device must be designed to handle multiple substrate thicknesses for compatibility
Solution Approach 1:
The patent designs the optical head device with multi-functionality to handle multiple substrate thicknesses. The objective lens and optical system are configured to accommodate different substrate thicknesses (e.g., 1.2mm for CD, 0.6mm for DVD, 0.1mm for high-density disks) through adjustable focusing mechanisms, allowing a single device to serve multiple optical disk formats
3Adaptability or versatility
If multiple objective lenses are used to focus light beams onto optical disks with different substrate thicknesses, then the adaptability is improved, but the device complexity and size increase
Solution Approach 1:
The patent merges multiple objective lenses into a single integrated objective lens structure. This unified lens incorporates multiple focal points or adjustable elements that can focus light beams onto optical disks with different substrate thicknesses, thereby reducing the number of separate components while maintaining compatibility across multiple disk formats
4Adaptability or versatility
If the focal length is increased to focus light beams onto the information recording surface of thick substrate optical disks, then the adaptability to thick substrates is improved, but the device size and complexity increase
Solution Approach 1:
The patent employs dynamic focusing mechanisms that allow the focal length to be adjusted in real-time. The optical system can dynamically change its focal length to match different substrate thicknesses, enabling a single optical head to handle both thin and thick substrate disks without requiring multiple fixed-focus lenses or complex mechanical interchange systems
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 enables efficient and accurate recording and reproduction of optical disks with varying substrate thicknesses, reduces spherical aberrations, and facilitates miniaturization by integrating the optical element and objective lens as a single piece, enhancing the optical head device's performance and manufacturing ease.
Implementation Method 1
a dichroic polarization separation film for passing a first light beam of wavelength λ1, reflecting linearly polarized light of a second light beam of wavelength λ2 that is polarized in a first polarizing direction
Implementation Method 2
a dichroic polarization separation film for passing a first light beam of wavelength λ1, reflecting linearly polarized light of a second light beam of wavelength λ2
Implementation Method 3
a first 1⁄4 wavelength plate for converting the linearly polarized light of the second light beam that is polarized in the first polarizing direction and reflected by the dichroic polarization separation film, into substantially circularly polarized light
Implementation Method 4
a first reflecting surface for reflecting the second light beam that is converted to circularly polarized light by the first 1⁄4 wavelength plate
Data Source
AI summary
Providing an objective lens with a large numerical aperture (NA), the present invention records or plays conventional optical disks such as CDs and DVDs using an optical head capable of recording or reproducing high-density optical disks. An optical element (8) is provided between a first and second laser light source and an objective lens (18) for the purpose of converting a wave front of a second optical beam 32. Furthermore, the optical element (8) and the objective lens (18) are fixed to move as a single piece.