Medical Microscope Optical Axis Calibration via Zoom Neutral Point
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Solution Overview
Problem
Accurate determination of the optical axis of a main observer camera in a medical microscope arrangement is crucial for maintaining high tracking quality and object correlation between cameras, but existing methods face challenges due to angular errors and calibration inaccuracies, especially when capturing at different magnification levels.
Innovation Solution
A method involving the use of a zoom system to capture and evaluate image representations of a test object at various magnification levels, determining a neutral point in the environment camera's coordinate system, and using this point to estimate the optical axis, which can be updated and corrected for precise extrinsic calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods are used to determine the optical axis, then the calibration process is simple, but the measurement precision of the optical axis position deteriorates due to angular errors
Solution Approach 1:
The patent applies the dynamics principle by capturing image representations at multiple magnification levels rather than using a single static calibration approach. The zoom system dynamically changes magnification to capture the test object from different scales, allowing the determination of the neutral point through comparison of these dynamic states. This dynamic multi-magnification approach significantly improves optical axis position precision by eliminating angular errors that plague traditional single-point calibration methods.
2Measurement precision
If the optical axis is determined at multiple working distances to improve accuracy, then the measurement precision improves, but the loss of time increases due to repeated calibration
Solution Approach 1:
The patent applies preliminary action by performing the comprehensive multi-magnification, multi-working-distance calibration procedure once during the initial setup phase. The neutral point determined through this preliminary comprehensive calibration is then stored and reused for subsequent tracking operations. This eliminates the need to repeat the time-consuming calibration process at each working distance during actual surgical procedures, thereby reducing time loss while maintaining high measurement precision.
3Reliability
If the neutral point is determined through multiple magnification levels to eliminate angular errors, then the reliability of object tracking improves, but the device complexity increases due to the zoom system requirements
Solution Approach 1:
The patent applies universality by designing the zoom system to serve multiple functions: it is used both for the initial calibration phase (capturing images at multiple magnification levels to determine the neutral point) and for the actual surgical observation phase. The same main observer camera with zoom capability performs both calibration and surgical imaging tasks, eliminating the need for separate calibration and observation systems. This multi-functionality improves object tracking reliability through accurate neutral point determination while avoiding the additional device complexity of separate calibration equipment.
Data Source
AI summary
A method for determining an optical axis of a main observer camera of a medical microscope arrangement in a reference coordinate system includes capturing a capture region with a main observer camera and at least partly with an environment camera. The environment camera is configured to track objects and its coordinate system or a coordinate system of an optical marker forms the reference coordinate system. A test object is captured at at least one working distance where a neutral point of a zoom system of the main observer camera is determined in the coordinate system of the environment camera by capturing and evaluating image representations of the test object at different magnifications. The optical axis is determined proceeding from the neutral point. At least one item of descriptive information describing the determined optical axis in the reference coordinate system is generated and provided. Furthermore, a medical microscope arrangement is provided.