Optical Disc Drive Lens Control for Multi-Format Detection
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Solution Overview
Problem
Existing optical disc drives lack a method to effectively distinguish and manage various types of optical discs, including those with different base material thicknesses and recording densities, leading to issues with focusing and groove-tracking controls, especially with increased numerical aperture values that reduce working distance and require measures to prevent lens impingement.
Innovation Solution
An optical disc drive equipped with multiple light sources emitting different wavelengths, an objective lens actuator, and a control device that searches for and focuses on information recording surfaces based on signals from a photo detector, determining disc type by moving the objective lens along the optical axis and adjusting wavelengths to maximize air-equivalent length or using the shortest wavelength for initial detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an objective lens with a greater numerical aperture (NA) is employed to increase recording density, then the recording capacity of the optical disc is improved, but the working distance is reduced and lens impingement on the disc surface occurs
Solution Approach 1:
The patent performs preliminary detection of the optical disc type and thickness before attempting to focus. By detecting whether the disc is a thin disc (BD/HD-DVD) or thick disc (DVD/CD) and adjusting the objective lens NA accordingly, the system prevents lens impingement on the disc surface while maintaining the necessary recording density for high-capacity discs.
Solution Approach 2:
The patent dynamically adjusts the numerical aperture of the objective lens based on the detected disc type. The system switches between different NA values (e.g., NA=0.85 for thin discs, NA=0.65 for thick discs) to optimize both working distance and recording density for different disc formats, resolving the contradiction between these two parameters.
2Adaptability or versatility
If multiple types of optical discs with different base material thicknesses are supported, then the adaptability of the optical disc drive is improved, but the complexity of focusing and groove-tracking controls increases
Solution Approach 1:
The patent performs preliminary detection of the optical disc type (thin disc vs. thick disc) before initiating focusing and groove-tracking operations. By identifying the disc type in advance and pre-configuring the appropriate objective lens NA and focusing parameters, the system simplifies the overall control complexity while maintaining support for multiple disc formats.
Solution Approach 2:
The patent implements a universal detection and control mechanism that handles multiple disc types (BD, HD-DVD, DVD, CD) through a single integrated system. The objective lens and control device are designed to accommodate different disc thicknesses and types by dynamically adjusting parameters, rather than requiring separate dedicated systems for each disc format.
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
Enables rapid and accurate identification of various optical disc types, preventing lens impingement and ensuring high-quality image replay and data retrieval from discs with mixed recording densities, even with increased numerical aperture values.
Implementation Method 1
an objective lens for converging light emitted from the light sources on an information recording layer in an optical disc
Implementation Method 2
a photo detector for receiving light reflected by the recording layer in the optical disc in the case where the light is converged on the recording layer by the objective lens and photoelectrically converts the light into electric signals
Implementation Method 3
an objective-lens actuator for moving the objective lens in the direction of an optical axis
Data Source
AI summary
An optical disc type is determined by detecting focus error signals and an amount of returned light, while (i) emitting light having a wavelength maximizing a focal length and (ii) moving an objective lens in a direction of an optical axis. If an S shape and AS immediately after a surface are greater than those at the surface, the optical disc is determined to have a largest capacity. It is also determined whether there is a reflective layer at a depth equal or less than 0.1 mm, if not, then it is determined whether there is a reflective layer at a depth of 0.6 mm. If there is a reflective layer at the depth of 0.6 mm, then the type of the reflective layer is determined based on TE/RF signals, using blue light. If the blue light is not adaptable, red light is emitted to replay at a depth of 0.6 mm.