Optical Tracking Apparatus Duty Ratio Adjustment
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Solution Overview
Problem
Conventional optical information reproduction apparatuses face instability in tracking due to warpage of recording media, deviations in optical characteristics, and tilts of the optical axis, leading to incorrect detection of tracking errors and unstable operation.
Innovation Solution
A tracking apparatus with a photoelectric detector, arithmetic unit, phase comparator, absolute value detector, level detector, sensitivity detector, and controller that adjusts detection conditions to optimize the output, reducing the impact of warpage and optical axis tilts, and maintaining stable tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the off-track signal is obtained from the tracking phase difference absolute value signal, then the tracking error detection is simplified, but the stability deteriorates due to excessive duty ratio increase under warpage or optical axis tilt conditions
Solution Approach 1:
A new intermediary component, the duty ratio adjusting circuit, is introduced between the level detector and the tracking control. This circuit receives the off-track signal and adjusts its duty ratio to a predetermined value, thereby mediating the impact of warpage and optical axis tilt on the tracking control. The duty ratio adjusting circuit acts as a buffer that prevents direct transmission of instability from the optical system to the tracking servo.
2Measurement precision
If the detection sensitivity of the level detector is increased to detect smaller tracking errors, then the measurement precision improves, but the reliability deteriorates due to false detection under warpage or optical deviation conditions
Solution Approach 1:
The invention changes the detection parameter from raw signal amplitude to duty ratio. The duty ratio adjusting circuit transforms the off-track signal by adjusting its duty ratio to a predetermined value, which provides a more stable detection characteristic. This parameter transformation allows the system to maintain high measurement precision while reducing false detection under warpage or optical deviation conditions, as the duty ratio is less sensitive to absolute signal level variations.
3Reliability
If the optical pickup is designed with higher precision to reduce warpage and optical axis tilt, then the reliability improves, but the manufacturing cost increases
Solution Approach 1:
The duty ratio adjusting circuit serves as a compensating intermediary that reduces the impact of optical pickup imperfections on tracking stability. By adjusting the duty ratio of the off-track signal to a predetermined value, the circuit compensates for warpage and optical axis tilt effects, thereby improving tracking reliability without requiring the optical pickup to be manufactured with extremely high precision.
4Measurement precision
If the off-track detection threshold is lowered to detect smaller deviations, then the measurement precision improves, but the device complexity increases due to additional adjustment mechanisms
Solution Approach 1:
The duty ratio adjusting circuit performs self-adjustment by automatically setting the duty ratio of the off-track signal to a predetermined value. This self-service mechanism eliminates the need for complex external adjustment mechanisms, as the circuit inherently maintains optimal detection conditions by regulating its own output characteristic.
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 apparatus achieves improved stability and accuracy in tracking by optimizing the detection conditions, allowing for successful operation with multi-layered recording media and reducing costs by minimizing performance requirements for optical axis alignment.
Implementation Method 1
a photoelectric detector (1) including four light-receiving cells A, B, C and D
Data Source
AI summary
A tracking apparatus for an optical information reproduction apparatus includes the following: a photoelectric detector (1) in which a far-field pattern of a light spot converged on a recording medium is formed across a divided light-receiving cell; an arithmetic unit (2) for outputting at least a pair of arithmetic signals from the output of the photoelectric detector (1); a phase comparator (4) for detecting a phase difference between the output signals of the arithmetic unit (2); an absolute value detector (8) for detecting an absolute value of the output signal of the phase comparator (4); a level detector (9) for generating a signal that indicates whether or not a convergence position of the light spot is located off an information track by detecting a predetermined number of times or more the output signal of the absolute value detector (8) has become larger than a predetermined value; a sensitivity detector (10) for detecting and outputting the sensitivity of the level detector (9) by observing the output signal of the level detector (9); and a controller (11) for adjusting the detection conditions of the level detector (9) so that the output of the sensitivity detector (10) is a predetermined value.