Optical Pickup Diffractive Grating Simultaneous Write Read
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Solution Overview
Problem
Conventional optical read/write drives face challenges in maintaining high write rates and data reliability, especially with low random accessibility storage media like optical tapes, and struggle with overwrite operations and bidirectional tracking stability.
Innovation Solution
The optical pickup uses a diffractive element with first and second diffraction gratings of different grating vector directions and pitches to split the light beam into zero-order and non-zero-order diffracted beams, allowing for simultaneous writing and reading with a photodetector that generates a differential signal for verification, ensuring stability during overwrite operations and bidirectional tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single light beam is used for both writing and reading, then device complexity is reduced, but writing and reading operations cannot be performed simultaneously
Solution Approach 1:
The single light beam is segmented into multiple diffracted beams (zero-order and non-zero-order) by a diffraction grating. The zero-order beam is used for writing data while the non-zero-order beams are used for reading/verifying data simultaneously, enabling concurrent write and verify operations without requiring separate light sources.
Solution Approach 2:
A single light beam serves multiple functions by being diffracted into different orders. The same light source generates both the write beam (zero-order) and the read/verify beams (non-zero-order), making the optical system multi-functional and eliminating the need for separate light sources for writing and reading.
2Reliability
If data is written on an optical storage medium, then data storage capacity is increased, but verification of written data requires additional time and reduces write speed
Solution Approach 1:
The verification (read) operation is performed simultaneously with the write operation using non-zero-order diffracted beams that read the data as it is being written. This preliminary verification happens in real-time during the write process, eliminating the need for separate post-write verification passes and maintaining high write speeds.
Solution Approach 2:
The verify operation continues continuously during the write operation without interrupting the writing process. The optical pickup simultaneously writes data with the zero-order beam and verifies it with non-zero-order beams, ensuring uninterrupted data storage at high speed while maintaining reliability through continuous verification.
3Adaptability or versatility
If overwrite operations are performed on optical storage medium, then data更新 capability is improved, but tracking stability deteriorates due to signal interference
Solution Approach 1:
The write modulated signal component is extracted and removed from the read signal by using non-zero-order diffracted beams that do not contain the write modulation. This separation allows the read signal to be free from write interference, enabling stable tracking and reliable data verification during overwrite operations without signal contamination.
4Ease of operation
If bidirectional tracking is implemented, then ease of operation is improved, but tracking precision deteriorates due to signal fluctuations
Solution Approach 1:
Non-zero-order diffracted beams serve as intermediary read beams that are not modulated by the write operation. These beams provide a clean reference signal for tracking verification that is independent of write modulation, enabling precise tracking control in both forward and reverse directions without signal interference or fluctuations.
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 high-speed writing and reading with improved reliability and stability, even during overwrite operations and bidirectional tracking, by canceling the write modulated signal component and maintaining data quality on optical storage media.
Implementation Method 1
a diffractive element for diffracting the light beam to split the light beam into multiple diffracted light beams, the multiple diffracted light beams including a zero-order diffracted light beam for writing data on a track
Implementation Method 2
a photodetector configured to receive at least part of the diffracted light beams reflected from the optical storage medium
Implementation Method 3
a lens for condensing the diffracted light beams onto the optical storage medium
Implementation Method 4
detecting the light that has been modulated by, and reflected from, the optical storage medium
Data Source
AI summary
In one embodiment of the present invention, an optical pickup for writing and reading data on an optical storage medium comprises a diffractive element for diffracting a light beam to split it into multiple light beams. The diffracted light beams includes a zero-order diffracted light beam for writing data on a track of the land or the groove of the optical storage medium and non-zero-order diffracted light beams for reading the data from the track. The diffractive element has first and second diffraction gratings that have mutually different grating vector directions and pitches. The first diffraction grating forms light beam spots on the same track by the non-zero-order and zero-order diffracted light beams. The second diffraction grating forms a light beam spot to extend to both sides of said track, or forms a light beam spot on one side of said track, by the non-zero-order diffracted light beams.