OCT Path Length Switching for Precise Eye Length Measurement
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Solution Overview
Problem
Existing optical coherence tomography (OCT) systems face challenges in reconciling high resolution or image quality with manageable data rates, particularly when measuring large distances like the human eye, where uninteresting regions like the vitreous humor contribute to high data rates and increased costs.
Innovation Solution
A path length switching unit alternates optical path lengths to focus on relevant regions (cornea and retina) with high precision, optimizing signal-to-noise ratio and reducing data rates by alternating imaging between these regions, using adjustable telescopes and dispersive elements to enhance focus and signal differentiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full OCT bandwidth is used to measure the entire eye length, then measurement precision is improved, but data rates increase excessively
Solution Approach 1:
The measurement process is segmented into two distinct phases: a first measurement phase capturing the corneal region at full resolution, and a second measurement phase capturing the retinal region at full resolution. The path length switching unit alternates between these phases, allowing the system to segment the data acquisition process and only collect data from regions of interest rather than the entire eye depth, thereby reducing overall data rates while maintaining measurement precision for the critical structures.
Solution Approach 2:
The invention extracts and focuses measurement effort on the most critical regions (cornea and retina) by using the path length switching unit to selectively direct the OCT beam to these regions. The system extracts only the necessary data from these regions rather than collecting data from the entire eye including the uninteresting vitreous humor, thus reducing data volume while preserving measurement precision for the structures that matter.
2Quantity of substance
If the measurement depth is reduced to lower data rates, then data rates are improved, but image quality and resolution suffer
Solution Approach 1:
The path length switching unit dynamically adjusts the optical path length between the first and second measurement phases. This dynamic adjustment allows the system to adapt the measurement depth and focus based on the specific measurement phase, ensuring that when measuring the cornea, the system focuses on the corneal region, and when measuring the retina, it focuses on the retinal region, thereby maintaining high image quality and resolution for the regions of interest while managing data rates.
3Quantity of substance
If the path length switching unit alternates between corneal and retinal imaging, then data rates are reduced, but measurement precision for eye length must be maintained
Solution Approach 1:
The evaluation unit processes signals from both the first and second measurement phases and uses feedback to determine the positions of the cornea and retina. By combining the positional information from both phases and using the known offset between the path lengths, the system can accurately calculate the eye length. This feedback mechanism ensures that even though data is collected alternately from different regions, the final measurement precision for eye length is maintained.
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 precise measurement of eye length with high precision and optimized image quality while maintaining low data rates, allowing for reproducible and accurate measurements.
Implementation Method 1
The light reflected by the sample or object interferes with the reference beam. Signals from the interference can be used to examine the sample with a depth resolution
Implementation Method 2
The term 'optical coherence tomography' (usually abbreviated by OCT) is understood to be an imaging method. With this method, two-dimensional and three-dimensional images can be obtained from light-scattering structures
Implementation Method 3
The path length is modified by diverting beam paths over different geometric paths
Data Source
AI summary
In view of the problem of making the intrinsically competing objects of high resolution or image quality and generation of the smallest possible data rates when measuring object lengths as compatible as possible, a device (1) for determining the length of an object (6) when carrying out optical coherence tomography comprising an interferometer with a light source (2), a sample arm (4) and a reference arm (5), wherein the light emitted by the light source (2) is splitable by a beam splitter (3) such that first light (4a) is guidable in an outward and return direction on the sample arm (4) and second light (5a) is guidable in an outward and return direction on the reference arm (5), wherein the first and the second returning light (4a, 5a) can be made to interfere, wherein an evaluation unit (8) for acquiring and processing signals from the interfering first and second light (4a, 5a) is arranged and wherein a path length switching unit (13a, 13b) is arranged in the beam path of the sample arm (4) and/or in the beam path of the reference arm (5) and modifies the optical path length of the respective light (4a, 5a) passing through the path length switching unit (13a, 13b), is characterized in that at least one path length switching unit (13a, 13b) changes an optical path length from a first value to a second value alternately in time.