Digital Celestial Sensor Calibration via Integrated Parameter Modeling
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Solution Overview
Problem
Current celestial sensor calibration methods are prone to errors due to installation inaccuracies and external factors, leading to reduced precision in estimating internal parameters such as focal length and distortion coefficients, especially when using simulated sunlight or starlight.
Innovation Solution
A high-precision calibration method and device for digital celestial sensors that incorporate an integrated external and internal parameters modeling approach, utilizing a two-step calibration process with nonlinear least square iterations to accurately determine calibration parameters, including radial and tangential distortion coefficients, without requiring complex installation adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a celestial simulator is used to provide simulated sunlight or starlight for calibration, then the calibration process becomes more convenient and the precision of estimating focal length and main point coordinate is improved, but installation errors and adjustment errors between the celestial sensor and rotator introduce errors in the calibration method
Solution Approach 1:
The patent introduces a mathematical model as an intermediary between the physical calibration system and the parameter estimation process. This model accounts for installation errors and external factors by incorporating them as adjustable parameters, allowing the system to compensate for these errors through computational correction rather than requiring perfect physical alignment.
Solution Approach 2:
The patent transforms the calibration approach by changing from a purely geometric parameter estimation to a comprehensive parameter estimation that includes external parameters (installation errors, rotator accuracy) alongside internal parameters (focal length, main point coordinate). This parameter expansion allows the system to adapt to real-world imperfections.
2Device complexity
If only internal parameters (focal length F and main point coordinate) are used in the calibration model, then the calibration process is simpler, but errors are introduced due to nonlinear distortion in the pinhole imaging model and external factors
Solution Approach 1:
The patent segments the calibration parameters into internal parameters (focal length, main point coordinate, distortion coefficients) and external parameters (installation errors, rotator axis accuracy, sunlight vector deviation). This segmentation allows the model to systematically address different sources of error while maintaining a structured calibration process.
Solution Approach 2:
The patent creates a composite calibration model that combines multiple parameter types (internal and external) into a unified mathematical framework. This composite approach integrates the pinhole imaging model with distortion models and external error sources, creating a more comprehensive and accurate calibration system.
Data Source
AI summary
A method for calibration of a digital celestial sensor is disclosed. First, an integrated mathematic model for imaging of a celestial sensor is established according to external and internal parameters of the calibration system of the celestial sensor. Second, by rotating two axes of a rotator by different angles, calibration points data are acquired and sent to a processing computer through an interface circuit. Finally, a two-step calibration program is implemented to calculate the calibration parameters by substituting calibration points' data to the integrated mathematic model. An application device of the calibration method is also provided. The device may include a celestial simulator to provide simulated sunlight or starlight, a two-axis rotator to acquire different calibration points' data, and a processing computer to record the calibration points' data and calculate the calibration parameters.