OCT-Guided Robotic Ophthalmic Positioning With Encoder Drift Correction
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Solution Overview
Problem
Existing OCT systems suffer from thermal drift and angular position errors due to galvanometer scanners and bearing friction, leading to inaccurate tissue positioning during robotic ophthalmic procedures, which can result in errors up to 100 microns and hinder precise robotic guidance.
Innovation Solution
Incorporation of absolute and incremental encoders with the galvanometer scanners to provide accurate angular position data, allowing for precise determination of tissue positions in a 3D coordinate system, and a controller to transform these positions into a coordinate system for a robotic device, enabling precise robotic instrument movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If galvanometer scanners are used in OCT systems, then scanning capability is achieved, but thermal drift causes angular position errors leading to tissue positioning inaccuracies
Solution Approach 1:
The patent replaces the mechanical angular sensing system (capacitive sensors coupled to galvanometer scanners) with an optical encoder system. The optical encoders provide angular position measurements that are immune to thermal drift effects, thereby substituting a thermal-sensitive mechanical system with a thermally-stable optical measurement system.
Solution Approach 2:
The patent introduces optical encoders as intermediary devices between the galvanometer scanners and the control system. These encoders act as mediators that provide accurate angular position feedback without being affected by the thermal drift of the galvanometer scanners, thus decoupling the positioning accuracy from thermal effects.
2Measurement precision
If analog capacitive angle sensors are used with galvanometer scanners, then angular position measurement is achieved, but thermal drift cannot be corrected resulting in up to 100 microns positioning error
Solution Approach 1:
The patent substitutes the analog capacitive angle sensors with optical encoders. The optical encoding mechanism is inherently immune to thermal drift, replacing a thermal-vulnerable capacitive sensing system with a thermally-stable optical measurement system that provides accurate angular position data despite temperature variations.
Solution Approach 2:
The patent changes the measurement parameter from capacitive coupling (sensitive to thermal drift) to optical encoding (immune to thermal drift). By transitioning to a different physical domain for measurement, the system achieves thermal stability while maintaining angular position measurement capability.
Data Source
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AI summary
The systems and methods described herein provide improved techniques for OCT guided robotic ophthalmic procedures. A method includes receiving, during OCT scanning of an eye, position data of a plurality of galvanometer scanners from a plurality of absolute and incremental encoders coupled to the corresponding galvanometer scanners. The method further includes receiving scan data related to one or more tissues of the eye. The method further includes determining, a set of first positions of the one or more tissues of the eye in a first 3D coordinate system. The method further includes determining, based on the set of first positions and a mapping between the first and a second 3D coordinate systems, a position in the second 3D coordinate system for a surgical instrument coupled to a robotic device. The method includes causing the robotic device to move the surgical instrument to the position in the second 3D coordinate system.