Optical Disc Reading Device Laser Modulation Control
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Solution Overview
Problem
Existing optical disc reading technologies face challenges in maintaining signal quality and preventing data erasure when increasing the linear velocity of optical discs, leading to a drop in the signal-to-noise ratio and potential damage to recorded marks.
Innovation Solution
A method and device that adjust the light modulation rate and average read power of the laser beam in accordance with the selected linear velocity, ensuring that the peak power is reduced proportionally to maintain signal quality and prevent data erasure, by prerecoding information on the disc for optimal reading conditions at multiple linear velocities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the linear velocity of the optical disc is increased to improve data transfer rate, then productivity is improved, but the signal-to-noise ratio drops and recorded marks may be erased
Solution Approach 1:
The patent applies dynamics by making the laser beam parameters (average read power and light modulation rate) variable rather than fixed. The control unit dynamically adjusts these parameters based on the detected linear velocity, allowing the system to adapt to different operating conditions and maintain optimal signal quality across varying speeds without erasing recorded marks.
Solution Approach 2:
The patent changes physical parameters of the laser beam (average read power and light modulation rate) in response to changing operating conditions (linear velocity). By adjusting these parameters, the system maintains adequate signal-to-noise ratio at higher speeds while preventing the laser power from becoming excessive and erasing the recording marks.
2Reliability
If the average read power of the laser beam is increased to improve signal quality at high linear velocity, then the signal-to-noise ratio improves, but the recorded marks may be erased
Solution Approach 1:
The system dynamically adjusts the average read power based on the detected linear velocity. At higher speeds, the control unit increases the average read power to maintain signal quality, but simultaneously adjusts the light modulation rate to prevent excessive peak power that would erase the marks. This dynamic balance prevents data erasure while maintaining adequate signal quality.
Solution Approach 2:
The patent uses periodic high-frequency modulation of the laser beam (light modulation) to create a rhythmic pattern of power delivery. This periodic action allows the system to maintain elevated average power for good signal quality while the modulation cycles prevent any single continuous high-power exposure that could erase the marks. The modulation rate is adjusted according to linear velocity to maintain optimal performance.
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 approach effectively prevents signal degradation and data loss by adjusting the light modulation rate and read power, maintaining high signal quality and reliability across varying disc speeds without erasing recorded marks.
Implementation Method 1
a semiconductor laser which emits a laser beam onto the recording medium
Implementation Method 2
focusing a powerful laser beam by means of the objective lens onto the recording film of the optical disc to raise the temperature of the recording film above the melting point
Implementation Method 3
the recording film changes between crystalline and amorphous states
Implementation Method 4
The objective lens focuses a laser beam on the optical disc to form a light spot at the diffraction limit
Implementation Method 5
the change in reflected light is detected to produce an analog read signal from the recorded data
Data Source
AI summary
A reading devices suppresses deterioration of the recording marks caused by increasing the output laser power to compensate for a drop in the S/N ratio when reading at a high speed information recorded to a high density recording medium. To read information recorded to an optical data recording medium that is written and read using a laser beam output from a semiconductor laser, the reading method modulates a high frequency current on the drive current of the semiconductor laser to output the laser beam, and changes the light modulation rate according to the selected linear velocity used for reading. The light modulation rate is the ratio Pp/Pave between the peak power Pp and the average read power Pave of the light intensity of the high frequency modulated laser beam.