Optical Head Wavelength Selective Blocking for Disc Interference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical head devices struggle to simultaneously record or reproduce information from optical discs with different base member thicknesses and multiple recording layers without increasing the number of components, while maintaining high signal-to-noise ratio and minimizing interference between layers.
Innovation Solution
An optical head device incorporating a first laser light source for blue light and a second laser light source for red light, a focusing optical system, and a wavelength selective light blocking region on a detection hologram to block interfering blue light and transmit red light, allowing for reduced interference and high S/N ratio during recording and reproduction across various optical disc types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the numerical aperture NA is increased to achieve higher storage density, then the storage capacity is improved, but the amount of aberration produced by optical axis tilt increases
Solution Approach 1:
The patent changes the base member thickness parameter to 0.1 mm, which is significantly thinner than conventional discs (0.6-1.2 mm). This parameter change allows the optical system to achieve high NA (0.85) while minimizing spherical aberration caused by optical axis tilt, thereby enabling high storage capacity without excessive aberration
Solution Approach 2:
The patent employs dynamic adjustment mechanisms including a focus control system that can adjust the focal position of the objective lens, and a tracking control system that adjusts the lens position radially. These dynamic adjustments compensate for aberrations and maintain optimal focus conditions when reading from different recording layers at different depths
2Manufacturing precision
If the base member thickness is reduced to prevent aberration increase, then the aberration amount is reduced, but the device must support multiple disc thicknesses which increases complexity
Solution Approach 1:
The optical head device is designed with multi-functionality to handle multiple optical disc types (CD, DVD, Blu-ray) with different base member thicknesses (1.2 mm, 0.6 mm, 0.1 mm) using the same objective lens. The focus control system can dynamically adjust to accommodate different thicknesses, making the device universal rather than requiring separate heads for each disc type
Solution Approach 2:
The optical head device segments the optical path into distinct wavelength channels (red light for DVD, blue light for Blu-ray) using wavelength-selective elements. This segmentation allows independent optimization for each disc type while sharing common components like the objective lens and photodetector
3Productivity
If multiple recording layers are added to increase capacity, then the storage capacity is improved, but interference between layers increases
Solution Approach 1:
The patent introduces a wavelength-selective light blocking region as an intermediary element in the optical path. This blocking region selectively blocks blue light (wavelength λ1) while transmitting red light (wavelength λ2), preventing blue light reflected from deeper recording layers from interfering with the detection of signals from upper layers
Solution Approach 2:
The light blocking region is positioned at a specific location in the optical path where it selectively affects only the blue light path. This local quality modification allows the system to block harmful blue light while leaving the red light path unaffected, enabling multi-layer storage without cross-layer interference
4Measurement precision
If a wavelength selective light blocking region is added to reduce interference, then the signal-to-noise ratio is improved, but the device complexity increases
Solution Approach 1:
The wavelength-selective light blocking region is merged with the existing detection hologram or beam splitter component. By combining multiple functions (wavelength selection, light blocking, and beam steering) into a single integrated element, the patent improves signal-to-noise ratio without proportionally increasing device 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
The solution enables compatibility with multiple optical disc formats, reduces interference between recording layers, and maintains an excellent signal-to-noise ratio during reproduction, achieving these results without increasing the number of components in the optical head device.
Implementation Method 1
a first laser light source that emits blue light at a wavelength λ1; a second laser light source that emits red light at a wavelength λ2
Implementation Method 2
a wavelength selective light blocking region which blocks a predetermined range of the blue light including an optical axis thereof to prevent the predetermined range from reaching the photodetector, and transmits the red light
Implementation Method 3
a photodetector that receives the blue light reflected by the recording layer of the first optical information medium or the red light reflected by the recording layer of the second optical information medium and outputs an electric signal in accordance with an amount of the received blue light or red light
Implementation Method 4
a focusing optical system that focuses the blue light emitted from the first laser light source onto a recording layer of a first optical information medium through a base member having a first thickness t1 or focuses the red light emitted from the second laser light source onto a recording layer of a second optical information medium through a base member having a second thickness t2
Data Source
AI summary
When information is recorded or reproduced on or from an optical information medium having three or more recording layers using blue light, interference by another layer light is reduced and, when information is reproduced from an optical information medium using red light, an S/N ratio is held excellently high.An optical head device includes a first laser light source (1) which emits blue light, a second laser light source (2) which emits red light, an objective lens (11) which focuses the blue light onto a recording layer of a first optical disc (12) or focuses the red light onto a recording layer of a second optical disc (13), a photodetector (9) which receives the blue light reflected by the recording layer of the first optical disc (12) or the red light reflected by the recording layer of the second optical disc (13) and outputs an electric signal in accordance with an amount of the received blue light or red light, and a wavelength selective light blocking region (7x) which blocks a predetermined range of the blue light including an optical axis thereof to prevent the predetermined range from reaching the photodetector (9), and transmits the red light.