Phase Detection in Optical Data Storage Using CMOS Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current page-based optical data storage technologies, particularly those using CMOS active pixel sensors, are not optimized for phase detection, leading to higher hardware complexity and sensitivity to alignment issues, despite offering advantages like higher dynamic range and lower bit error rates with phase modulation.
Innovation Solution
A system comprising a CMOS active pixel sensor array and a coherent phase-shift keyed detection system, coupled with a feedback control system and differential detection, optimized for phase detection in page-based optical data storage, which includes alignment sensors and beam-splitter configurations to improve bit value determination and reduce misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase modulation is used in page-based optical data storage, then dynamic range and storage density are improved, but hardware complexity and alignment sensitivity increase
Solution Approach 1:
The patent replaces complex mechanical alignment systems with an electronic feedback control system that uses alignment sensors to detect beam position and electronically adjusts the reference beam phase, substituting mechanical precision requirements with electronic control
Solution Approach 2:
The patent implements a feedback control system that continuously monitors alignment using dedicated sensors and automatically adjusts the reference beam phase to maintain optimal alignment, eliminating the need for high mechanical precision
2Reliability
If phase modulation is used in page-based optical data storage, then storage density improves, but alignment sensitivity increases
Solution Approach 1:
The patent implements a feedback control system with alignment sensors that continuously monitor beam alignment and automatically adjust the reference beam phase, replacing the need for high manufacturing precision with electronic correction
Solution Approach 2:
The patent dynamically changes the phase parameter of the reference beam based on feedback from alignment sensors, allowing the system to adapt to alignment variations without requiring precise mechanical alignment
3Measurement precision
If heterodyne detection is used for phase detection, then detection accuracy improves, but DC offset and noise increase
Solution Approach 1:
The patent extracts and removes the DC offset component from the heterodyne detection signal through differential detection, separating the useful phase information from the harmful DC component
Solution Approach 2:
The patent introduces differential detection as an intermediary processing stage that cancels DC offsets by comparing signals from adjacent pixels, eliminating the harmful DC component while preserving phase information
4Measurement precision
If heterodyne detection is used for phase detection, then detection accuracy improves, but noise increases
Solution Approach 1:
The patent introduces differential detection as an intermediary that cancels common-mode noise by comparing signals from adjacent pixels, reducing noise while preserving the phase detection capability
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 system enhances phase detection accuracy, reduces bit error rates, and improves dynamic range utilization by aligning beams precisely and canceling DC offsets, resulting in more efficient data retrieval with lower hardware complexity.
Implementation Method 1
The photodetector sensor array is positioned to receive a data page when the data page is optically read from the storage medium (e.g., by optical diffraction, reflection or transmission through the storage medium)
Implementation Method 2
Phase detection is typically performed by aligning a signal beam with a reference beam and coherently mixing the two, resulting in a mixed signal proportional in amplitude to the phase of the signal beam, in a process commonly known as heterodyne detection
Implementation Method 3
aligning a signal beam with a reference beam and coherently mixing the two
Implementation Method 4
A plurality of alignment sensors are positioned about the pixel array. Differences in sensor signals are indicative of angular misalignment between the reference beam and the signal beam. The feedback control system processes the differences in sensor signals and aligns the heterodyne reference beam with respect to the signal beam
Implementation Method 5
The first and second photodetector sensor arrays may be configured to cancel a DC offset by balancing the inputs to the differential detection system
Data Source
AI summary
A system for phase detection in page-based optical data storage involves a number of features that may be used individually or in combination to provide optimizations and to facilitate the heterodyne detection of the modulated readout signal beam. In one aspect, alignment sensors provide signals indicative of angular misalignment between the heterodyne reference beam and the signal beam, and a feedback control system aligns the reference beam with respect to the signal beam. In another aspect, a differential detection approach is utilized. In yet another aspect, a scanning approach is used wherein the reference beam is scanned over approximately a wavelength of phase difference to cause interference fringes to shift over the photodetector pixel array. Each pixel detects the signal at the phase value that cancels out localized variations of the wavefront, thus increasing the tolerance of the system to phase errors and to angular misalignments.