Meta-optic Accelerator for Object Classification

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Solution Overview

Problem

Deep neural networks (DNNs) require increasing computational resources, leading to unsustainable energy consumption and limitations in real-time decision-making, while existing optical processors for image analysis are limited by the need for coherent illumination and enlarged systems that do not utilize additional information channels like polarization.

Innovation Solution

A meta-optic accelerator system combining a metalens and a metasurface optical front end that duplicates images and generates feature maps, enabling fast and energy-efficient object classification with a digital back end, capable of operating under incoherent ambient lighting and leveraging polarization information.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If deep neural networks are used to increase classification accuracy and capability, then the performance of machine-based tasks is improved, but energy consumption increases unsustainably and real-time decision making is restricted

Engineering Contradiction:
Improveclassification accuracyVSAvoidenergy consumption
Core Design Contradiction:
Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The system divides the neural network processing into two segments: optical convolution layers performed by the meta-optic accelerator and digital activation function layers performed by the digital neural network. This segmentation allows computationally intensive linear operations to be offloaded to the low-power optical system while retaining non-linear transformations in the digital domain, thereby reducing overall energy consumption while maintaining classification accuracy.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent replaces digital mechanical computation (FLOPs) with optical field operations for convolution layers. The meta-optic accelerator uses light propagation and interference to perform matrix-vector multiplications and convolutions physically, eliminating the need for digital computation in these layers and dramatically reducing energy consumption while preserving the ability to achieve high classification accuracy.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Use of energy by moving object

If optical processors are used to reduce energy consumption and increase processing speed, then energy efficiency and speed are improved, but the systems require coherent illumination and enlarged imaging systems

Engineering Contradiction:
Improveenergy consumptionVSAvoidsystem size
Core Design Contradiction:
Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent changes the illumination parameter from coherent to incoherent light, enabling the use of ambient lighting conditions. The metalens and metasurface designs are specifically optimized to function with incoherent illumination, eliminating the need for complex coherent light sources and associated optical components, thereby reducing system size and complexity while maintaining energy efficiency.

Inventive Principle:
Principle #35Parameter changes

3Productivity

If diffractive neural networks are used to achieve fast processing and low power consumption, then processing speed and energy efficiency are improved, but additional information channels such as polarization cannot be utilized

Engineering Contradiction:
Improveprocessing speedVSAvoidinformation channel utilization
Core Design Contradiction:
ProductivityVSAdaptability or versatility

Solution Approach 1:

The metasurface in the meta-optic accelerator is designed to be multi-functional, simultaneously manipulating amplitude, phase, and polarization of light. This allows the system to process multiple information channels in parallel, including polarization information, while maintaining fast processing speeds. The universal design enables the same optical component to extract features from different physical properties of light.

Inventive Principle:
Principle #6Universality (Multi-functionality)

4Ease of operation

If free-space optical correlators are used to enable spatial multiplexing and direct integration with imaging systems, then ease of integration is improved, but the systems are enlarged and do not achieve compact form factors

Engineering Contradiction:
Improveintegration with imaging systemVSAvoidsystem size
Core Design Contradiction:
Ease of operationVSVolume of moving object

Solution Approach 1:

The patent integrates the metalens and metasurface directly onto the imaging sensor, nesting the optical processing functions within the existing imaging system architecture. This eliminates the need for separate optical correlator systems and their associated components, achieving compact integration while maintaining ease of operation and direct compatibility with imaging systems.

Inventive Principle:
Principle #7Nested doll (Nesting)

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 achieves superior processing speed and reduced power consumption, allowing for compact, high-speed computer vision systems by offloading computationally expensive convolution operations into the optical front end and optimizing neural network architecture.

Implementation Method 1

a metalens that duplicates a received image into multiple images

Methodology Applied
Scientific EffectDiffraction: Diffraction

Implementation Method 2

a metalens that duplicates a received image into multiple images

Methodology Applied
Scientific EffectLens focusing: Lens

Implementation Method 3

a metasurface that receives the duplicate images and outputs a feature map based on the received images

Methodology Applied
Scientific EffectOptical interference: Interference

Implementation Method 4

The current optical approach is limited to linear operations, which prevents the use of activation functions, but these types of layers could be added in the future based on non-linear media

Methodology Applied
Scientific EffectPolarization: Polarisation

Data Source

PatentUS20230237790A1META-optic accelerators for object classifiers
Publication Date: 2023.07.27 VANDERBILT UNIV
  • US20230237790A1 patent drawing
  • US20230237790A1 patent drawing
  • US20230237790A1 patent drawing

AI summary

A system for identifying objects in images is provided. The system may include an optical front end and a digital back end. The optical front end includes a metalens that duplicates a received image into multiple images, and a metasurface that receives the duplicate images and outputs a feature map based on the received images. The feature map may be equivalent to the computationally expensive convolution operations previously performed by a neural network. The feature map is provided to the digital back end, which uses a neural network to classify the object. Because the feature map included the convolution operations, the digital back end can classify the object more quickly and using fewer computing resources than previous systems.