Contact-Based Spatial Frequency Domain Imaging Sheet

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Solution Overview

Problem

Existing spatial frequency domain imaging (SFDI) systems are complex and limited in their application due to the need for projection optics and are not well-suited for imaging curved or variable shapes, and they suffer from blurring and light absorption in air.

Innovation Solution

A contact-based SFDI system using a flexible sheet with integrated lighting and sensor elements, including a collimating structure, allows direct imaging of a medium with precise control over illumination patterns and improved light measurement, eliminating the need for projection optics and enhancing image resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If projection-based SFDI systems are used, then imaging capability is achieved, but device complexity increases due to requirement of projection optics and spatial modulators

Engineering Contradiction:
Improvesystem complexityVSAvoidimaging capability
Core Design Contradiction:
Device complexityVSReliability

Solution Approach 1:

The patent extracts and removes the projection optics and spatial modulators from the SFDI system, replacing them with a flexible sheet containing integrated lighting elements that directly contact the medium. This elimination of complex optical components directly reduces device complexity while maintaining imaging capability through the sheet's ability to project patterns via direct contact.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The flexible sheet with integrated lighting elements serves multiple functions simultaneously: it acts as the light source, the projection medium, and the contact interface with the sample. This self-service approach eliminates the need for separate projection optics and spatial modulators, reducing system complexity while preserving imaging functionality.

Inventive Principle:
Principle #25Self-service

2Adaptability or versatility

If projection optics are used, then illumination patterns can be projected, but imaging of curved or variable shapes is limited

Engineering Contradiction:
Improveadaptability to curved surfacesVSAvoidimage quality
Core Design Contradiction:
Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent employs a flexible sheet as the core imaging component that can conform to curved and variable shapes of the medium being imaged. This flexible contact interface allows the system to adapt to diverse sample geometries while maintaining precise spatial relationships between lighting elements, sensors, and the sample surface, thereby preserving image quality across different surface topographies.

Inventive Principle:
Principle #30Flexible shells and thin films

3Measurement precision

If projection optics are used, then illumination can be provided, but blurring occurs in the projected patterns

Engineering Contradiction:
Improvespatial resolutionVSAvoidoptical system complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent removes the projection optics that cause blurring and replaces them with a direct-contact flexible sheet architecture. The lighting elements are positioned in immediate proximity to the medium surface, eliminating optical path-related blurring while maintaining spatial resolution through precise control of lighting element activation patterns.

Inventive Principle:
Principle #2Taking out (Extraction)

4Adaptability or versatility

If standard wavelengths are used in projection systems, then imaging is possible, but light absorption in air limits the available wavelengths

Engineering Contradiction:
Improvewavelength selection flexibilityVSAvoidlight absorption
Core Design Contradiction:
Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The flexible sheet acts as an intermediary medium that eliminates air as the transmission path between the light source and the sample. By providing direct contact illumination, the system bypasses atmospheric absorption, enabling the use of wavelengths that would otherwise be absorbed by air, thereby expanding the available wavelength range for imaging.

Inventive Principle:
Principle #24Intermediary (Mediator)

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 provides precise, simplified, and adaptable imaging capable of continuous monitoring on curved surfaces, with improved resolution and reduced blurring, and enables use of wavelengths otherwise absorbed in air.

Implementation Method 1

The sheet comprise an array of lighting elements generating illumination light patterns illuminating the medium

Methodology Applied
Scientific EffectLight emission from lighting elements: Light Emitting Diode

Implementation Method 2

measuring spatially resolved images of resulting light patterns reflected back after interaction of the illumination light patterns with the medium

Methodology Applied
Scientific EffectLight reflection: Reflection

Implementation Method 3

The system further comprises a collimating structure arranged between the lighting elements and the contact surface

Methodology Applied
Scientific EffectLight collimation: Lens

Data Source

PatentEP4469784B1Spatial frequency domain imaging system and method
Publication Date: 2026.03.11 NEDERLANDSE ORG VOOR TOEGEPAST NATUURWETENSCHAPPELIJK ONDERZOEK TNO
  • EP4469784B1 patent drawingFigure 1A~1C
  • EP4469784B1 patent drawingFigure 2A~2D
  • EP4469784B1 patent drawingFigure 3A~3B

AI summary

A system and method for contact-based spatial frequency domain imaging (SFDI). A medium (M) to be imaged is contacted by a sheet (10) comprising an array of lighting elements (11) generating illumination light patterns (Li) illuminating the medium (M), and comprising an array of sensor elements (12) measuring spatially resolved images of resulting light patterns (Lr) reflected back after interaction of the illumination light patterns (Li) with the medium (M). The lighting elements (11) generate illumination light patterns (Li) that are spatially modulated in light intensity along a surface of the illuminated medium (M) according to a respective different spatial frequency (Fn). A set of spatially modulated images (In) is determined based on the measured resulting light patterns (Lr) caused by the different illumination light patterns (Li). An image (Im) of the medium (M) can be generated based on a combination of the spatially modulated images (In).