CMOS Sensor Array Servo-Tracking for Page-Based Optical Storage
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Solution Overview
Problem
Page-based optical data storage technologies, such as holographic data storage, face challenges in accurately tracking the focus, radial, and longitudinal shifts of the media with respect to the read/write optical head, as well as rotations, due to the sensitivity of two-dimensional pages, which existing sensors are not optimized to address effectively.
Innovation Solution
A CMOS active pixel sensor array is optimized for servo-tracking in page-based optical data storage by defining multiple alignment arrangements to achieve correct three-dimensional alignment between the data page and the sensor array, using a beam-splitter to align the sensor array and spatial light modulator, and generating servo-feedback signals for focus, tangential, radial, and azimuthal tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional charge-coupled device detectors are used, then imaging capability is adequate, but unit cost is high and design flexibility is limited
Solution Approach 1:
The patent replaces expensive charge-coupled device detectors with low-cost CMOS active pixel sensors. CMOS sensors are significantly cheaper to manufacture and offer greater design flexibility while maintaining adequate imaging capability for optical data storage applications.
Solution Approach 2:
The patent optimizes the CMOS sensor parameters specifically for optical data storage applications rather than general imaging. This includes tailoring the pixel architecture, well depth, and readout circuitry to match the specific requirements of detecting optical pages from storage media.
2Ease of manufacture
If CMOS active pixel sensors optimized for imaging are used, then unit cost is reduced and design flexibility is improved, but servo-tracking performance for data storage is insufficient
Solution Approach 1:
The patent modifies specific regions of the CMOS sensor to optimize for servo-tracking. This includes creating dedicated areas for focus error detection, radial tracking, and azimuthal tracking with specialized photodetector arrangements and signal processing circuits tailored for these functions.
Solution Approach 2:
The sensor array is divided into multiple functional zones: data detection regions, focus error detection regions, radial tracking regions, and azimuthal tracking regions. Each segment is optimized for its specific function, allowing the overall sensor to perform multiple servo-tracking tasks simultaneously.
3Device complexity
If standard sensor arrays are used, then device complexity is low, but alignment accuracy for three-dimensional tracking is insufficient
Solution Approach 1:
The patent extends the two-dimensional sensor array into three-dimensional space by incorporating multiple focal planes and depth-resolved detection capabilities. This allows simultaneous measurement of positional and focal depth information, enabling complete six-degree-of-freedom tracking.
Solution Approach 2:
The patent introduces alignment marks and reference patterns as intermediary elements between the optical page and the sensor array. These markers provide known reference points that facilitate precise calibration and real-time alignment measurement without requiring complex direct measurements.
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 provides improved alignment accuracy and stability in both recording and readout processes, enhancing the overall performance of page-based optical data storage systems by accurately tracking the necessary degrees of freedom, thereby improving data retrieval and storage efficiency.
Implementation Method 1
with the aid of a beam-splitter and combined in a single read/write optical head
Implementation Method 2
correct three-dimensional alignment between the data page and the sensor array
Data Source
AI summary
A system for page-based optical data storage includes a sensor array positioned to track a data page when the data page is optically read from or recorded to a storage medium. A servo mechanism is used to position the sensor array. A plurality of alignment points are defined relative to the photodetector pixel array. An alignment arrangement is located at each alignment point. The sensor array further includes servo-feedback signal generation logic operative to drive the servo mechanism based on error signals from the alignment arrangements, thereby aligning the two-dimensional photodetector array with respect to the two-dimensional data page.