Thin Stackup for Diffuse Fluorescence Imaging
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Solution Overview
Problem
Conventional fluorescence imaging systems face challenges in achieving deep tissue imaging due to tissue scattering and absorption, limiting depth to about 1 mm, and require significant volume and thickness for wavelength separation, which is not suitable for compact wearable devices.
Innovation Solution
A thin optical stackup system using edge-coupled light sources, a light guiding layer with total internal reflection, and an output coupler to direct excitation light to the tissue, combined with a thin film filter to separate excitation and emission wavelengths, allowing for compact, lens-less diffuse fluorescence imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional fluorescence imaging systems use off-axis illumination or folded illumination with dichroic optical elements to separate excitation and emission wavelengths, then wavelength separation is achieved, but the system requires considerable volume and thickness along the optical axis
Solution Approach 1:
The patent transitions from conventional optical path separation in three-dimensional space (off-axis or folded illumination) to two-dimensional planar light propagation within a light guiding layer. By coupling light at the edge of a planar waveguide and utilizing total internal reflection, the system achieves wavelength separation through a thin film filter in a compact configuration, reducing the optical axis thickness from millimeters to micrometers while maintaining effective excitation and emission separation.
Solution Approach 2:
The patent introduces a thin film filter as an intermediary element disposed between the light guiding layer and the image sensor. This thin film filter selectively transmits emission wavelengths while blocking excitation wavelengths, enabling effective wavelength separation without requiring bulky dichroic optical elements or complex optical paths. The thin film filter acts as a spectral mediator that resolves the wavelength separation requirement in a space-efficient manner.
2Measurement precision
If conventional fluorescence imaging systems are designed to achieve deep tissue imaging, then imaging depth is limited to about 1 mm due to tissue scattering and absorption, but increasing device volume is not suitable for compact wearable devices
Solution Approach 1:
The patent employs a light guiding layer with thickness on the order of micrometers (e.g., 10-100 μm) instead of conventional millimeter-scale optical components. This thin-film waveguide structure enables compact wearable device integration while maintaining effective light guidance and coupling to tissue, allowing diffuse fluorescence imaging at depths up to 2 mm without requiring large device volume.
Solution Approach 2:
The patent changes the scale parameter of the optical system from millimeter-scale conventional optics to micrometer-scale thin-film waveguides. By reducing the characteristic dimension of the light guiding layer to the micrometer range while maintaining appropriate optical properties (refractive index, thickness), the system achieves both compact form factor for wearable devices and sufficient imaging depth through diffuse light propagation in tissue.
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
Enables imaging up to 2 mm depth with reduced device size and improved spatial resolution, effectively separating excitation and emission wavelengths for enhanced contrast and detection efficiency.
Implementation Method 1
a light guiding layer with total internal reflection, and an output coupler to direct excitation light to the tissue
Implementation Method 2
a thin film filter to separate excitation and emission wavelengths, allowing for compact, lens-less diffuse fluorescence imaging
Implementation Method 3
Fluorescence imaging involves a fluorophore marker or tag that emits light at an emission wavelength in response to interacting with light at an excitation wavelength
Data Source
AI summary
The present disclosure relates to optical systems for fluorescence-based imaging. An example optical system includes an image sensor. The image sensor is sensitive to at least a first wavelength of light and a second wavelength of light. The optical system also includes a light guiding layer optically coupled to the image sensor and a light source positioned to emit light into a side surface of the light guiding layer. The emitted light includes light at the first wavelength and the emitted light is transmitted in an in-plane direction in the light guiding layer. The optical system further includes a thin film filter and an output coupler optically coupled to the light guiding layer. At least a portion of the emitted light transmitted in an in-plane direction in the light guiding layer is coupled out of the light guiding layer in an out-of-plane direction via the output coupler.