Hyperspectral Retinal Imaging Using Structured Beamlets
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Solution Overview
Problem
Current hyperspectral imaging and fluorescence spectroscopy techniques for the human eye face challenges such as long acquisition times, motion blur artifacts, high costs due to the need for spatially coherent broadband optical sources, and limited ability to efficiently capture spectral information, especially in vivo.
Innovation Solution
An apparatus and method utilizing a spatially incoherent light source to generate a structured illumination field with a two-dimensional array of beamlets, projected onto the eye, and analyzed using a spectrometer with a two-dimensional sensor array, allowing for efficient spectral mapping and hyperspectral imaging, including confocal and fluorescence spectroscopy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If point-scanning systems are used for hyperspectral imaging, then spectral information can be obtained, but acquisition times are long and motion blur artifacts occur
Solution Approach 1:
The invention divides the broadband spectrum into multiple wavelength bands using a dispersive element, creating multiple beamlets that simultaneously illuminate different regions of the retina. This segmentation of the spectral information allows parallel acquisition of spectral data across multiple wavelength bands, dramatically reducing acquisition time compared to sequential point-scanning methods.
Solution Approach 2:
The invention transitions from one-dimensional point scanning to two-dimensional spectral imaging by using a 2-D sensor array that captures spatial and spectral information simultaneously. The dispersive element spreads light in one dimension while the sensor array captures spatial distribution in another dimension, enabling parallel acquisition of spectral data across the entire field of view.
2Productivity
If spatially coherent broadband optical sources are used, then hyperspectral imaging can be performed efficiently, but system cost increases
Solution Approach 1:
The invention replaces expensive spatially coherent broadband sources (such as supercontinuum lasers) with inexpensive spatially incoherent sources (such as LED arrays). Although incoherent sources have lower brightness, the use of a 2-D sensor array and dispersive element compensates for this by enabling simultaneous detection of multiple wavelength bands, achieving comparable hyperspectral imaging efficiency at much lower cost.
Solution Approach 2:
The invention substitutes the need for complex optical coherence control mechanisms with a direct detection approach using a 2-D sensor array. Instead of relying on the spatial coherence properties of the light source, the system uses geometric optics and detector array geometry to achieve spectral separation and detection, eliminating the need for expensive coherent sources.
3Measurement precision
If confocal detection is used for autofluorescence imaging, then stray light from different sample locations is reduced, but system complexity increases
Solution Approach 1:
The invention creates a confocal arrangement where the illumination beamlets and detection apertures are spatially matched. Each beamlet illuminates a specific retinal location and is detected by a corresponding aperture-sensor pair, ensuring that only light from the intended focal plane is detected. This equipotential matching of illumination and detection paths provides confocal rejection of stray light without requiring complex additional optical elements.
4Loss of information
If lifetime measurements are used for fluorescence characterization, then molecular information can be obtained, but very high speed processing is required and only point by point imaging is possible
Solution Approach 1:
The invention changes the measurement parameter from fluorescence lifetime to fluorescence spectrum. Instead of measuring the temporal decay of fluorescence (which requires high-speed processing and point-by-point scanning), the system measures the spectral distribution of fluorescence emission using a dispersive element and 2-D sensor array. This spectral approach provides molecular characterization information while enabling rapid full-field imaging.
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 enables faster, more accurate, and cost-effective hyperspectral imaging and fluorescence spectroscopy, capable of capturing detailed spectral information from the eye, improving diagnostic capabilities and patient comfort.
Implementation Method 1
a light source configured to generate an input irradiance field having a wavelength band consisting of a plurality of wavelengths
Implementation Method 2
a structured light generator for converting the input irradiance field into a structured illumination field comprising an array of beamlets
Implementation Method 3
an optical system for projecting the structured illumination field onto a region of the sample, including angularly encoding the beamlets such that each beamlet is projected onto a position of the sample corresponding to the encoded angle
Implementation Method 4
a spectrometer comprising a two-dimensional sensor array configured to spectrally analyze a portion of light that is reflected, backscattered or fluoresced from the region of the sample
Implementation Method 5
a spectral mapping module configured to map, based on a predefined mapping function, positions on the sensor array to a two-dimensional position on the sample and a wavelength of the light within a plurality of predefined wavelength bins
Implementation Method 6
a hyperspectral image generator configured to generate a hyperspectral image from sensor signals of the sensor array and the predefined mapping function, the hyperspectral image comprising two or more en-face images of the region of the sample, the two or more en-face images including spectral response information of the sample from each beamlet of the structured illumination field
Implementation Method 7
The optical system includes a dispersive element for angularly dispersing each of the beamlets into an elongated band of beamlet spectral components corresponding to each of the plurality of wavelengths
Implementation Method 8
The apparatus includes a confocal aperture array spatially filtering the reflected, backscattered or fluoresced light from the region of the sample before detection by the spectrometer
Implementation Method 9
a second light source configured to generate a second input irradiance field having a second wavelength band, the second wavelength band being an excitation wavelength band for fluorophores in the sample
Implementation Method 10
Blue light excited AF of the retina preferably uses confocal detection rather than a fundus photo to identify the AF signal
Data Source
AI summary
The present invention relates to a hyperspectral apparatus and method. One aspect of the invention provides an apparatus for analyzing a sample. The apparatus comprises a light source configured to generate a broadband input irradiance field. The apparatus also comprises a structured light generator for converting the input irradiance field into a structured illumination field including an array of beamlets. An optical system projects the structured illumination field onto a region of the sample such as the retina. A spectrometer is configured to spectrally analyze a portion of light that is reflected, backscattered or fluoresced from the region of the sample. A processor is operatively associated with the spectrometer and configured to generate a hyperspectral image comprising two or more en-face images of the region of the eye. The en-face images include spectral response information of the sample from each beamlet of the structured illumination field.