Time-of-Flight Phase-Offset Calibration Using Compact Reflector
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Solution Overview
Problem
Current time-of-flight depth camera calibration methods are complex, costly, and impractical for field recalibration due to manufacturing tolerances, asymmetric illumination, and the need for large reflective target panels, limiting their usability and flexibility in different depth ranges.
Innovation Solution
A method involving a compact reflector and optical diffuser for calibrating the imaging array, where modulated emission from the camera reflects off the compact reflector and passes through the diffuser, allowing for phase offset correction independent of lens imperfections, enabling calibration in two steps and making field recalibration feasible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional calibration methods using large reflective target panels are used, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the essential calibration function from the complex traditional system by using a compact reflector that can be positioned at a known distance from the camera. This small reflector replaces the large reflective target panel, maintaining calibration accuracy while dramatically reducing system complexity and cost.
Solution Approach 2:
The patent introduces an optical diffuser as an intermediary element between the compact reflector and the imaging array. The diffuser scatters the reflected light to ensure uniform illumination across the imaging array, enabling accurate phase offset measurement without requiring the complex traditional calibration setup.
2Manufacturing precision
If factory calibration using expensive precision equipment is used, then manufacturing precision is improved, but ease of manufacture decreases
Solution Approach 1:
The patent employs a compact, inexpensive reflector that can be easily positioned and removed, replacing the need for expensive factory calibration equipment. This simple, low-cost component enables accurate calibration to be performed in the field without requiring specialized manufacturing facilities.
Solution Approach 2:
The calibration system is designed to be self-contained and portable, allowing the imaging array to be calibrated in the field without requiring external factory facilities. The compact reflector and optical diffuser form a complete calibration kit that can be operated independently, making the system self-sufficient and easy to manufacture.
3Measurement precision
If calibration is performed in factory using fixed setup, then measurement precision is improved, but adaptability decreases
Solution Approach 1:
The patent transforms the static factory calibration setup into a dynamic, portable system. The compact reflector and optical diffuser can be easily repositioned and reconfigured for calibration at different locations and depths, enabling the system to adapt to various field conditions while maintaining calibration precision.
Solution Approach 2:
The calibration system is designed with universal applicability, allowing the same compact reflector and optical diffuser to be used for calibration across different imaging arrays, depths, and environmental conditions. This multi-functional design eliminates the need for specialized calibration equipment for each application, greatly enhancing adaptability.
4Device complexity
If asymmetric illumination is present, then device complexity increases, but ease of operation decreases
Solution Approach 1:
The patent addresses asymmetric illumination by using an optical diffuser that creates locally uniform light distribution across the imaging array. The diffuser ensures that each pixel receives appropriate illumination regardless of the overall asymmetric lighting conditions, simplifying the calibration operation without requiring complex compensation algorithms.
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
This approach simplifies the calibration process, reduces costs, and allows for flexible recalibration in various depth ranges without the need for large reflective target panels, enhancing the usability and adaptability of time-of-flight depth cameras.
Implementation Method 1
passes through an optical diffuser en route to the imaging array
Implementation Method 2
time-of-flight phase-offset calibration
Implementation Method 3
the modulated emission reflects from a compact reflector
Data Source
AI summary
A method to calibrate an imaging array of a time-of-flight depth camera includes the act of modulating emission from a light source of the camera while synchronously biasing the imaging array. In this method, the modulated emission reflects from a compact reflector positioned a known distance from the camera and passes through an optical diffuser en route to the imaging array. For each pixel of the imaging array, a correction term is stored, which brings the output from that pixel into agreement with the actual distance between the camera and the compact reflector.