Optical Pickup Speed Control Using Track Crossing Pulse Half-Period Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical disc apparatuses face challenges in accurately controlling the movement speed of optical pickups during multitrack jump due to defects in reproduced signals caused by damage or dirt on the disc, leading to erroneous detection of track crossing and failure to stop over the target track.
Innovation Solution
The apparatus includes a defect detector and an average-period generator that measure and correct the half-period of track crossing pulses to generate a reference speed for the optical pickup, allowing for accurate movement control even with defective signals, using a servo mechanism to adjust the pickup's speed based on calculated average and corrected average half periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If track crossing pulses are used to control optical pickup speed, then moving speed control is achieved, but signal defects cause erroneous detection and failure to stop at target track
Solution Approach 1:
The patent implements feedback by continuously monitoring track crossing pulse periods and using the most recent valid period to adjust speed control. The system feeds back the measured half-period information to the speed control unit, enabling real-time correction of pickup movement based on actual track crossing rates, thereby maintaining accuracy even when some pulses are defective.
Solution Approach 2:
The patent applies preliminary action by pre-establishing a lookup table that maps half-period values to corresponding speed control parameters. This allows the system to quickly retrieve appropriate speed adjustments based on measured periods without complex real-time calculations, enabling rapid response to signal defects while maintaining stable speed control during multitrack jump operations.
2Stability of the object's composition
If interpolated dummy pulses are used to compensate for dropped track crossing pulses, then pulse continuity is maintained, but moving speed adjustment becomes slow and inaccurate
Solution Approach 1:
The patent extracts and utilizes the most recent valid track crossing pulse period information separately from the defective or interpolated pulses. By isolating the reliable period measurement and using it for speed control decisions, the system avoids the delays and inaccuracies associated with interpolated dummy pulses, achieving both signal continuity and rapid speed adjustment.
Solution Approach 2:
The patent changes the control parameter from relying on interpolated pulse timing to using measured half-period values directly. This parameter change allows the system to adapt speed control based on actual physical measurements of track crossing intervals, providing more responsive and accurate speed adjustment even when some pulses are missing or defective.
3Device complexity
If conventional speed control based on track crossing pulse period is used, then speed regulation is simple, but accuracy deteriorates when reproduced signals have defects
Solution Approach 1:
The patent replaces the conventional mechanical counting method of track crossing pulses with an electronic measurement system that directly measures half-period values. This substitution enables more precise speed measurement by capturing actual time intervals between track crossings, improving accuracy while maintaining relatively simple control logic through electronic timing circuits and digital processing.
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 solution enables stable and accurate optical pickup movement control, ensuring the pickup can be accurately stopped over the target track even when reproduced signals suffer drop-outs or level decreases due to disc defects, improving the reliability of multitrack jump operations.
Implementation Method 1
Tracking error signals are generated based on reproduced signals gained from light beams reflected from an optical disc
Data Source
AI summary
A light beam is emitted to an optical disc from an optical pickup. The optical pickup is moved over the optical disc so that a light spot of the light beam crosses tracks formed on the optical disc. Detected are tracking error signals carried by a light beam reflected from the optical disc. Each tracking error signal is detected when the light spot crosses a corresponding track among the tracks formed on the optical disc. Track crossing pulses are generated based on the tracking error signals. Each track crossing pulse is generated for the corresponding track. Measured next is a half period of each track crossing pulse. It is determined whether a defect occurs to each track crossing pulse, based on a latest half period measured at present and an anterior half period measured one half-period before the latest half period. Generated when determined that no defect occurs is an average half period of the latest and the anterior half periods. Generated when determined that the defect occurs is a corrected average half period based on the latest half period and a plurality of anterior half periods measured before the latest half period. A reference half period is generated that indicates a predetermined speed for the optical pickup to move over the optical disc. The optical pickup is then moved at the predetermined speed based on the reference half period and the average half period or the corrected average half period.