Chromatic Range Sensor Calibration Using Spherical Reference
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Solution Overview
Problem
Chromatic range sensors face challenges with component stability and calibration, requiring complex and impractical procedures for end-users, especially when attached to measuring machines, leading to measurement errors and the need for factory recalibration.
Innovation Solution
A method for determining distance calibration data using a chromatic range sensor optical pen configured to focus different wavelengths at various distances, performed in a spiral scan pattern relative to a spherical calibration object, allowing for simplified and reliable calibration on a measuring machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chromatic range sensors are calibrated using known methods, then measurement accuracy is maintained, but calibration complexity and impracticality increase for end-users
Solution Approach 1:
A spherical calibration object with known radius is introduced as an intermediary tool between the chromatic range sensor and the calibration process. This sphere serves as a simple, recognizable reference target that enables automated feature detection and simplifies the calibration procedure, making it practical for end-users to perform without requiring complex equipment or expertise.
Solution Approach 2:
The calibration system performs self-calibration by automatically detecting the spherical calibration object and computing calibration parameters without requiring manual intervention or complex user operations. The system uses the known geometry of the sphere and automated image processing to determine the optical center and other calibration parameters autonomously.
2Measurement precision
If chromatic range sensors are recalibrated at the factory, then measurement errors are corrected, but operational efficiency and user convenience decrease
Solution Approach 1:
The system enables self-calibration capability that allows users to perform recalibration themselves without sending the device back to the factory. This eliminates downtime and maintains operational efficiency while ensuring measurement accuracy through automated calibration procedures using the spherical reference object.
3Reliability
If component stability is improved, then measurement reliability increases, but device complexity and cost increase
Solution Approach 1:
The calibration parameters (optical center, focal length, distortion coefficients) are determined in advance through automated calibration and stored in the system. This preliminary characterization of the optical components allows the system to compensate for component variations and stability issues without requiring complex real-time adjustments or higher-cost components.
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 accurate and efficient calibration of chromatic range sensors, reducing measurement errors and enabling on-site recalibration without factory intervention, improving operational efficiency and user convenience.
Implementation Method 1
an optical element having axial chromatic aberration, also referred to as axial or longitudinal chromatic dispersion, may be used to focus a broadband light source such that the axial distance to the focus varies with the wavelength
Implementation Method 2
Upon reflection from the surface, the light is refocused onto a small detector aperture, such as a pinhole or the end of an optical fiber
Data Source
AI summary
A method provides distance calibration data for a chromatic range sensor system with a chromatic range sensor optical pen configured to focus different wavelengths at different distances along a distance measurement axis. The chromatic range sensor optical pen is arranged in a relationship relative to a spherical calibration object that has a nominally spherical calibration surface. Relative movement of the chromatic range sensor optical pen in relation to the nominally spherical calibration surface is controlled so as to perform a spiral scan of a portion of the nominally spherical calibration surface. Distance indicating data is determined as corresponding to the distances between the chromatic range sensor optical pen and surface points on the nominally spherical calibration surface as the spiral scan is performed. Distance calibration data for the chromatic range sensor system is determined based on the distance indicating data.