Confocal Detection for 3D Optical Data Storage

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Solution Overview

Problem

Current optical data storage systems face limitations in increasing areal density due to interlayer and intralayer crosstalk, particularly in multilayer media, which restricts the separation of data tracks and layers, and the finite fluorescence emission lifetime of emissive media limits read speed and signal-to-noise ratio.

Innovation Solution

A confocal detection system is developed using fiber optics to restrict the field of view (FOV) to 0.3 to 2 Airy disk diameters, reducing interlayer and intralayer crosstalk by isolating the desired signal from stray fluorescence and allowing for easier alignment and maintenance, while also employing differential confocal focus-error signal detection to improve axial resolution and signal-to-noise ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the field of view is reduced to limit intralayer crosstalk, then areal storage density is improved, but the signal-to-noise ratio deteriorates due to reduced light collection

Engineering Contradiction:

Improveareal storage densityVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent introduces a confocal pinhole aperture as an intermediary element in the detection path. This pinhole spatially filters the collected light, allowing only in-focus signals to pass through while blocking out-of-focus crosstalk from adjacent tracks. The pinhole acts as a mediator that selectively transmits desired signals while rejecting harmful crosstalk, thereby improving areal storage density without sacrificing signal-to-noise ratio.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If multilayer media are used to increase volume storage density, then storage capacity is improved, but interlayer crosstalk increases and limits layer separation

Engineering Contradiction:

Improvestorage capacityVSAvoidinterlayer crosstalk

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The confocal pinhole aperture serves as a spatial filter that selectively transmits light from the focused layer while blocking light from adjacent layers. This intermediary element enables multilayer storage by effectively isolating signals from different layers, allowing closer layer spacing without suffering from interlayer crosstalk interference.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces mechanical separation of layers with optical sectioning using confocal detection. Instead of relying on physical distance to prevent interlayer interference, the system uses optical principles (confocal filtering) to electronically isolate signals from different layers, enabling higher layer density.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If high numerical aperture objective lenses are used to increase areal density, then resolution is improved, but spherical aberration increases and limits focus precision

Engineering Contradiction:

Improveareal densityVSAvoidfocus precision

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The patent employs a focus error signal (FES) detection system that provides real-time feedback on focus accuracy. By monitoring the FES and adjusting the objective lens position accordingly, the system compensates for spherical aberration effects, maintaining precise focus despite using high numerical aperture lenses for increased areal density.

Inventive Principle:

Principle #23Feedback

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 confocal detection system enhances areal and axial resolution, reduces crosstalk, and increases the signal-to-noise ratio, enabling higher read speeds and storage density in optical data storage media by effectively isolating the desired signal and eliminating stray fluorescence, thus improving the performance of optical data storage systems.

Implementation Method 1

A confocal detection system is developed using fiber optics to restrict the field of view (FOV) to 0.3 to 2 Airy disk diameters

Methodology Applied

Scientific EffectConfocal detection:

Implementation Method 2

restricting the field of view (FOV) of the reading beam on an associated image plane to 0.3 to at least 2 Airy disk diameters

Methodology Applied

Scientific EffectAiry disk:

Implementation Method 3

FL data storage schemes include media that emit light across a spectral band when excited by a source in the absorption band of the luminescent media

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 4

employing differential confocal focus-error signal detection to improve axial resolution and signal-to-noise ratio

Methodology Applied

Scientific EffectFocus error signal detection:

Data Source

PatentUS12027178B2Systems and methods for increasing data rate and storage density in 3-dimensional optical data storage media

Publication Date: 2024.07.02 FOLIO PHOTONICS INC

AI summary

Systems and methods, e.g., optical apparatuses, for digital optical information storage systems that improve the speed, signal to noise, controllability, and data storage density for fluorescent and reflective multilayer optical data storage media. The systems and methods include an optical system for a reading beam of a data channel from a moving single or multi-layer or otherwise 3-dimensional optical information storage medium that comprises at least one optical element characterized by restricting the field of view (FOV) of the reading beam on an associated image plane to 0.3 to 2 Airy disk diameters in a first direction.