Robotic Camera Optical Axis Calibration for Precise Target Alignment
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Solution Overview
Problem
Robotic camera systems in precision surgeries face significant position errors due to misalignment of the camera's optical axis with the robot's motion coordinate frame, especially at extended optical distances, leading to suboptimal results and extended surgery times.
Innovation Solution
An automated method generates a homogenous transformation matrix during calibration, allowing the robotic camera system to accurately align the camera's optical axis without prior knowledge of the camera's optics, using input signals and angular offsets to control subsequent motion sequences, thereby minimizing position errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the camera is mounted to the robot end-effector for precision surgery, then the surgical precision is improved, but position errors increase due to optical axis misalignment at extended optical distances
Solution Approach 1:
The patent performs preliminary calibration actions by capturing reference images at multiple known robot positions before actual surgery. This pre-calibration establishes transformation relationships between robot coordinates and camera coordinates, enabling accurate position compensation during extended optical distance operations without requiring real-time complex modeling.
Solution Approach 2:
The system implements feedback by continuously comparing expected camera positions (based on robot motion) with actual captured image features. The transformation matrix derived from calibration allows the system to feedback-correct position calculations, maintaining accuracy even when optical axis misalignment occurs at extended distances.
2Measurement precision
If full optical modeling is implemented to achieve high positional accuracy, then position error is reduced, but device complexity and programming difficulty increase significantly
Solution Approach 1:
The patent introduces a transformation matrix as an intermediary that bridges the robot coordinate system and camera coordinate system. This matrix serves as a simplified mediator that captures the essential geometric relationship without requiring complex optical modeling, thus reducing device complexity while maintaining position accuracy.
Solution Approach 2:
Instead of modeling the complex optical behavior directly, the system creates a simplified copy or representation of the coordinate transformation relationship through the transformation matrix. This matrix copy encapsulates the essential spatial relationship between robot and camera frames, avoiding the need for detailed optical parameter modeling.
3Ease of operation
If automated calibration method is used without optical parameters, then ease of operation is improved, but calibration accuracy may be compromised
Solution Approach 1:
The calibration system performs self-service by automatically capturing reference images and computing the transformation matrix without requiring manual optical parameter input or expert intervention. The system uses readily available robot position data and captured images to self-determine the coordinate relationship, simplifying operation while maintaining accuracy through automated computation.
Solution Approach 2:
The patent replaces manual optical measurement and modeling (mechanical/optical system) with automated image processing and computational geometry (information processing system). By substituting the complex optical parameter measurement process with automated image-based coordinate transformation computation, the system achieves both ease of operation and calibration accuracy.
Data Source
AI summary
A method, instructions for which are executed from a computer-readable medium, calibrates a robotic camera system having a digital camera connected to an end-effector of a serial robot. The end-effector and camera move within a robot motion coordinate frame (“robot frame”). The method includes acquiring, using the camera, a reference image of a target object on an image plane having an optical coordinate frame, and receiving input signals, including a depth measurement and joint position signals. Separate roll and pitch offsets are determined of a target point within the reference image with respect to the robot frame while moving the robot. Offsets are also determined with respect to x, y, and z axes of the robot frame while moving the robot through another motion sequence. The offsets are stored in a transformation matrix, which is used to control the robot during subsequent operation of the camera system.