Optical Drive Focus Control Using Pre-stored Signal Relations
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Solution Overview
Problem
Conventional drive devices for optical discs require a significant amount of time to generate signals for correcting crosstalk during start-up, leading to unstable focus control when dealing with focus and tracking errors.
Innovation Solution
A drive device that includes an optical pickup with a light source, objective lens, photodetector, and control section, which generates balance information and uses pre-stored relation information to adjust the focus of the objective lens based on focus and tracking error signals, enabling stable focus control during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the drive device rotates the optical disc at start-up to detect focus error signal and perform focus control and tracking control, then the drive device can achieve focus and tracking control, but the drive device requires a large amount of time to generate signal data for correcting crosstalk
Solution Approach 1:
The invention performs preliminary actions by pre-storing relation information in the storage section before actual operation. The relation information, which represents the relationship between signal differences and balance information, is prepared in advance and stored in non-volatile memory. This eliminates the need to generate and store this complex relation data during each start-up sequence, significantly reducing the time required for focus control signal generation while maintaining control stability.
2Object-generated harmful factors
If the drive device uses push-pull signal and focus crosstalk signal to generate corrected signal for offsetting track crossing crosstalk, then the drive device can suppress crosstalk, but the drive device requires a large amount of time to generate corrected signal data
Solution Approach 1:
The invention extracts the essential relationship information from the complex process of generating corrected signals. Instead of regenerating the complete corrected signal data during each operation, the system extracts and stores only the critical relation information (the relationship between signal differences and balance information) in the storage section. This extracted relation information is then reused during operation to quickly generate corrected signals, eliminating the time-consuming regeneration process while maintaining crosstalk suppression effectiveness.
3Reliability
If the drive device stores relation data for correcting crosstalk in memory, then the drive device can achieve stable focus control, but the drive device requires a large amount of time to generate and store the relation data during start-up
Solution Approach 1:
The invention applies preliminary action by pre-computing and storing the relation information in non-volatile memory before the drive device operates. This relation information, which captures the essential relationship between signal differences and balance information, is prepared in advance during manufacturing or initialization. During actual operation, the system simply retrieves this pre-stored relation information rather than performing complex real-time calculations, significantly reducing processing complexity and start-up time while maintaining focus control stability.
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 allows for stable focus control by adjusting the objective lens using relation information between focus and tracking error signals, reducing the time required for signal generation and improving operational stability when dealing with crosstalk.
Implementation Method 1
an objective lens which converges light from the light source onto an optical disc
Implementation Method 2
a photodetector section which detects light reflected from the optical disc
Data Source
AI summary
An optical drive includes: an optical pickup; a preprocessing circuit which processes an optical signal detected by the optical pickup; nonvolatile memory having stored therein relation information which represents the relation of a signal balance with respect to a signal difference between a TE signal and an FE signal at the time of a predetermined operation of the optical pickup; and a central processing circuit which performs focus control of the optical pickup. The preprocessing circuit generates the signal balance of the optical pickup. The preprocessing circuit also obtains the FE signal and the TE signal with respect to the optical disc. The central processing circuit derives a phase difference and an amplitude difference from the signal balance and the relation information, and calculates, based on the differences and the TE signal, a FE signal suitable for the predetermined operation.