Optical Head Device Dual-Wavelength Resin Lens Protection
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Solution Overview
Problem
Optical head devices compatible with multiple optical disc standards, such as CDs, DVDs, and Blu-ray Discs, face durability issues due to the use of materials optimized for shorter wavelengths, which deteriorate when exposed to blue light used for Blu-ray Discs, leading to performance degradation.
Innovation Solution
The optical head device employs a dual light source system with a luminous flux separating section, a first objective lens for blue wavelengths, and a second objective lens made of resin for red and infrared wavelengths, with antireflection films on the second objective lens to reduce blue light transmittance and prevent deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an optical component made of material optimized for CDs and DVDs is used in a three-wavelength compatible optical head device, then the performance for CDs and DVDs is improved, but the durability against blue light for BDs deteriorates
Solution Approach 1:
The optical head device is divided into separate optical paths for BDs and for CDs/DVDs. The BD optical path includes a blue laser source and corresponding optical components optimized for blue light, while the CD/DVD optical path includes red/infrared laser sources and components optimized for those wavelengths. This segmentation allows each subsystem to use materials optimized for its specific wavelength without compromising durability from exposure to other wavelengths.
Solution Approach 2:
A dichroic mirror is introduced as an intermediary component to separate the blue light path from the red/infrared light path. This mirror reflects blue light while transmitting red and infrared light, effectively preventing blue light from reaching the resin objective lens used in the CD/DVD path, thereby protecting it from deterioration while maintaining optical performance.
2Ease of manufacture
If a resin objective lens is used for the optical path, then the manufacturing cost and ease of manufacture are improved, but the resistance to blue light deterioration worsens
Solution Approach 1:
The harmful blue light is extracted or removed from the optical path that contains the resin objective lens. By using the dichroic mirror to reflect blue light into a separate BD optical path, the resin lens is protected from blue light exposure, allowing it to maintain its manufacturing advantages without suffering from blue light-induced deterioration.
Solution Approach 2:
The potential harm of blue light exposure to resin lenses is converted into a benefit by using the dichroic mirror's wavelength-selective properties. The mirror that would otherwise be seen as adding complexity actually protects the resin lens by blocking blue light, thereby extending the lens's operational life while maintaining the cost-effectiveness of using resin material.
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 enhances the durability and performance of the optical head device by minimizing the impact of blue light on the resin objective lens, ensuring reliable recording and reproduction across different optical disc standards.
Implementation Method 1
an optical multilayer film is formed on an optical component such as a polarized hologram with a phase plate so as to prevent deterioration of the organic material used in the optical component by shielding blue stray light with the optical multilayer film
Implementation Method 2
a first filtering section that is provided on a beam exit face of the second objective lens, and reduces transmittance of the first light beam to be lower than transmittance of the second light beam
Data Source
AI summary
An optical head device includes a first light source and a second light source respectively emitting a first light beam and a second light beam, a luminous flux separating section selectively separating the first and second light beams for which the same optical path is used, to first and second optical paths, respectively, and a first objective lens converging the first light beam that has been separated to the first optical path on the first optical information recording medium. Further, the optical head device includes a second objective lens made of resin and converging the second light beam separated to the second optical path on the second optical information recording medium, and a first filtering section formed on a beam exit face of the second objective lens and reducing the transmittance of the first light beam to be lower than transmittance of the second light beam.