Flat Retroreflector Using Quasi-Periodic Sub-Wavelength Arrays

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Solution Overview

Problem

Conventional retroreflector devices, such as corner cube retroflectors, contribute significantly to the size and weight of integrated transceiver assemblies due to their bulkiness, limiting their integration with optical modulators in applications like satellite and aircraft communications.

Innovation Solution

A retroreflector device fabricated using a binary lithography process on a flat substrate, incorporating a quasi-periodic array of sub-wavelength elements for the lens and mirror components, which are separated by a transparent spacer layer, allowing for integration with optical modulators and operation over a range of electromagnetic spectra.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional corner cube retroreflectors are used, then retroreflection function is achieved, but size and weight of the device increases significantly

Engineering Contradiction:

Improveretroreflection functionVSAvoidweight of retroreflector assembly

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The retroreflector is segmented into multiple functional layers (lens layer, retroreflective layer, substrate) that can be independently optimized and fabricated using standard planar processes, replacing the monolithic bulk structure with distributed thin-film functionality

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The mechanical bulk structure of corner cube retroreflectors is replaced with an optical thin-film system using lens arrays and retroreflective particles embedded in flat substrates, eliminating the need for thick mechanical housing while maintaining retroreflection function

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If conventional corner cube retroreflectors are used, then retroreflection function is achieved, but the device becomes bulky and difficult to integrate with optical modulators

Engineering Contradiction:

Improveretroreflection functionVSAvoidintegration complexity with optical modulators

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The retroreflector and optical modulator are merged into a single integrated device where the modulator is positioned in front of the retroreflector array, allowing both functions to operate within a compact unified structure that simplifies integration

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The flat substrate structure serves multiple functions simultaneously: it provides mechanical support, enables planar fabrication processes, allows integration with standard optical components, and maintains retroreflection functionality, making the device universally compatible with various optical system configurations

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Volume of moving object

If flat substrate retroreflectors with quasi-periodic arrays are used, then size is reduced and integration is improved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvevolume of retroreflectorVSAvoidprecision of quasi-periodic array fabrication

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The design transitions from periodic to quasi-periodic arrangements of retroreflective elements, allowing tolerance to manufacturing variations while maintaining optical functionality, and enables scaling of element sizes and spacing to optimize performance for different wavelength ranges

Inventive Principle:

Principle #35Parameter changes

4Ease of manufacture

If binary lithography process is used for fabrication, then manufacturing ease and cost are improved, but optical performance across wide spectral range must be maintained

Engineering Contradiction:

Improveease of fabrication using binary lithographyVSAvoidoptical performance across electromagnetic spectrum

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Different regions of the retroreflector array are designed with locally optimized element geometries and spacing to handle different wavelength ranges, allowing the same fabrication process to produce wavelength-selective regions that collectively cover a broad spectral range with high optical performance

Inventive Principle:

Principle #3Local quality

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 solution provides a compact, high-efficiency retroreflector that can be easily integrated with optical modulators, offering improved reflection efficiency and reduced size and weight, enabling efficient operation across various electromagnetic spectrum ranges.

Implementation Method 1

The lens component and/or the mirror component comprise a quasi-periodic array of elements, each of which comprises a dimension smaller than a wavelength of the radiation

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

a mirror component operable for reflecting the radiation focused by the lens component back along the angle of incidence

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS9891355B2Flat retroreflectors

Publication Date: 2018.02.13 CALIFORNIA INST OF TECH

AI summary

A retroreflector device is described, which includes a lens component operable for focusing radiation, which is incident thereto at an angle of incidence. The retroreflector also includes a mirror component operable for reflecting the radiation focused by the lens component back along the angle of incidence. The lens component and/or the mirror component includes a quasi-periodic array of elements, each of which comprises a dimension smaller than a wavelength of the radiation.