iToF Camera Self-Calibration Using Static Delay Offsets
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Solution Overview
Problem
Existing iToF camera calibration methods require physical movement of the camera or target, which is time-consuming and costly, making them impractical for high-volume manufacturing.
Innovation Solution
A method for calibrating iToF cameras by applying delays to illumination and pixel modulation signals without moving the camera or target, using a look-up table to store correction values for distortion due to high harmonic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If physical movement of camera or target is used for calibration, then calibration accuracy can be achieved, but calibration time and cost increase significantly
Solution Approach 1:
The patent replaces the mechanical calibration system (physical movement of camera or target) with an electronic signal processing system. By applying delay signals to the modulation signals and processing the pixel responses through correlation operations, the system achieves calibration without any mechanical movement, thereby eliminating calibration time while maintaining accuracy
Solution Approach 2:
The patent changes the parameter being calibrated from spatial position (physical movement) to temporal delay (signal timing). By introducing controlled delay signals and measuring pixel responses at different delay values, the system determines distortion parameters electronically, achieving calibration without mechanical movement
2Measurement precision
If physical movement of camera or target is used for calibration, then calibration accuracy can be achieved, but manufacturing cost increases
Solution Approach 1:
The patent eliminates expensive mechanical calibration equipment and processes by substituting them with electronic signal processing. The calibration is performed using software-based correlation operations on pixel response data, removing the need for precision mechanical stages, multiple calibration targets, and manual intervention, thereby significantly reducing manufacturing cost
Solution Approach 2:
The system performs self-calibration by using its own pixel array and signal processing capabilities. The calibration process is automated through electronic delay signal generation and correlation operations, eliminating the need for external calibration equipment, manual positioning, and operator intervention, thereby reducing manufacturing complexity and cost
3Device complexity
If high harmonic components are present in modulation signals, then system complexity is reduced, but depth measurement accuracy deteriorates
Solution Approach 1:
The patent implements a feedback-based calibration process where pixel responses are measured at multiple delay values, correlation operations identify the delay corresponding to maximum response, and this information is used to determine distortion parameters. The system uses the measured distortion to correct depth measurements, creating a closed-loop feedback mechanism that compensates for high harmonic effects while maintaining simple modulation signals
Solution Approach 2:
The patent performs preliminary calibration operations by measuring pixel responses at multiple predetermined delay values before actual depth measurement. Through correlation operations on these preliminary measurements, the system determines distortion parameters and establishes correction factors that are then applied during normal operation, eliminating the need for complex modulation signals while achieving high accuracy
Data Source
AI summary
Systems, devices, and methods are described to statically calibrate a time-of-flight (TOF) imaging system requiring no movement during the calibration process and no external components. Methods may include placing a target at a set distance from the imaging system, delaying a modulation signal according to a distance offset, receiving a reflected light signal from the target, generating a pixel response based on the reflected light signal and modulation signal, calculating a distance-related value based on the pixel response, determining a correction value based on the distance-related value, and storing the correction value in a memory of the imaging system. The distance-related value may include a phase offset or a depth measurement. The method may be performed for a plurality of distance offsets and corresponding delays to generate a plurality of correction values that may be used when operating the imaging system to perform depth measurements.