Spectral Domain OCT with 2D Lenslet Array for Single-Shot Imaging
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Solution Overview
Problem
Current spectral domain OCT systems face limitations in achieving high-resolution, single-shot 3D imaging with extended depth of field and reduced motion artifacts, particularly for in vivo applications, due to constraints in laser safety regulations and susceptibility to crosstalk and spurious reflections.
Innovation Solution
The development of a multi-wavelength optical source with an angularly variable illumination system and a processor that generates 3D composite images by simultaneously measuring phase and amplitude of light reflected from multiple volumes of the retina, using a 2D lenslet array and wavelength dispersive element to capture interferometric data in the Fourier or image plane, enabling digital refocusing and aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If scanning speed is increased by reducing dwell time, then acquisition speed is improved, but signal to noise ratio is degraded
Solution Approach 1:
The invention segments the illumination into multiple discrete spots across the sample area, allowing parallel acquisition of multiple A-scans simultaneously. This segmentation enables the system to maintain adequate dwell time per spot (preserving signal quality) while achieving high overall acquisition speed through parallel processing of multiple spots.
Solution Approach 2:
The invention transitions from sequential scanning in one dimension to two-dimensional spot array illumination. By distributing illumination across multiple spots in the lateral dimension, the system achieves parallel acquisition, effectively adding a spatial dimension to the acquisition process and eliminating the trade-off between speed and signal quality.
2Reliability
If laser power is increased to maintain signal quality during fast scanning, then signal to noise ratio is improved, but laser safety limits are exceeded
Solution Approach 1:
The total optical power is segmented and distributed across multiple discrete spots rather than concentrating it in a single scanning beam. This allows the system to maintain low power per spot (within safety limits) while achieving adequate total signal through parallel detection from multiple spots simultaneously.
Solution Approach 2:
The invention maintains continuous illumination of multiple spots simultaneously, ensuring that useful signal acquisition continues throughout the exposure period without the interruptions and power fluctuations associated with sequential scanning. This continuous parallel illumination maintains signal quality while adhering to safety limits.
3Measurement precision
If conventional spectral domain OCT is used, then depth resolution is achieved, but crosstalk and spurious reflections limit imaging quality
Solution Approach 1:
The invention extracts and isolates the interference signal from each individual spot using spatially-resolved detection. By separating the detection of interference patterns from different spatial locations, the system eliminates crosstalk between adjacent regions and removes spurious reflections that would otherwise contaminate the depth-resolved measurements.
Solution Approach 2:
The invention introduces a spatial encoding intermediary (the array of discrete spots with unique spatial positions) between the sample and detector. This spatial encoding allows the system to distinguish and separate signals from different locations, acting as a mediator that prevents signal contamination and enables clean depth resolution.
4Loss of time
If single-shot acquisition is implemented, then motion artifacts are reduced, but achieving high resolution with extended depth of field becomes difficult
Solution Approach 1:
The invention segments the imaging task into simultaneous acquisition from multiple discrete spots within a single shot. This segmentation allows the system to capture depth-resolved information from multiple locations simultaneously, achieving high resolution and extended depth of field without requiring sequential scanning that would introduce motion artifacts.
Solution Approach 2:
The invention adds the spatial dimension of multi-spot illumination to the single-shot acquisition approach. By illuminating and detecting from multiple spots simultaneously in the lateral dimension, the system achieves both the speed of single-shot acquisition (reducing motion artifacts) and the resolution of depth-resolved 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 allows for high-resolution, single-shot 3D imaging with improved depth of field and reduced motion artifacts, maintaining phase coherence and enhancing lateral resolution while minimizing crosstalk and spurious reflections.
Implementation Method 1
interfering light reflected from a sample with a reference beam provided by the same source
Implementation Method 2
dispersing the different wavelengths with a grating or other spectral demultiplexer
Implementation Method 3
a 2D lenslet array and wavelength dispersive element to capture interferometric data
Data Source
AI summary
Methods and apparatus are presented for obtaining high-resolution 3-D images of a sample over a range of wavelengths, optionally with polarisation-sensitive detection. In preferred embodiments a spectral domain OCT apparatus is used to sample the complex field of light reflected or scattered from a sample, providing full range imaging. In certain embodiments structured illumination is utilised to provide enhanced lateral resolution. In certain embodiments the resolution or depth of field of images is enhanced by digital refocusing or digital correction of aberrations in the sample. Individual sample volumes are imaged using single shot techniques, and larger volumes can be imaged by stitching together images of adjacent volumes. In preferred embodiments a 2-D lenslet array is used to sample the reflected or scattered light in the Fourier plane or the image plane, with the lenslet array suitably angled with respect to the dispersive axis of a wavelength dispersive element such that the resulting beamlets are dispersed onto unique sets of pixels of a 2-D sensor array.