Time-of-Flight Distance Measuring System Offset Error Calibration
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Solution Overview
Problem
Current time-of-flight distance measuring systems suffer from offset errors due to non-ideal continuous square wave pulses and separate conduction times of transmission gates, leading to inaccuracies in distance measurement.
Innovation Solution
A time-of-flight distance measuring system that includes a delay unit generating delayed pulses, a light-emitting unit emitting delayed pulsed lights, and a photosensitive pixel circuit generating pixel signals, with a control unit storing correspondence between delay times and pixel signals to perform accurate distance measurement by simulating different simulation distances and obtaining optimal delay signals for measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two conduction times of two transmission gates are separated by a time interval, then the photosensitive pixel circuit can function properly, but an offset error occurs between measured distance and actual distance
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements at multiple known distances before actual distance measurement. The system pre-acquires pixel signals at different delay times corresponding to different simulation distances, and stores the correspondence between these parameters. This preliminary calibration data is then used to correct offset errors during actual measurement, resolving the contradiction between circuit functionality and measurement accuracy.
2Duration of action of stationary object
If pulse transferred to light-emitting units is a non-ideal continuous square wave, then the system can operate continuously, but offset error occurs between measured distance and actual distance
Solution Approach 1:
The patent applies periodic action by using delayed pulses with different delay times to generate periodic light emission patterns. Instead of using a continuous non-ideal square wave that causes offset errors, the system employs multiple discrete delayed pulses at specific time intervals. This periodic pulsed approach maintains continuous operation capability while eliminating the offset errors associated with non-ideal continuous waves.
3Measurement precision
If multiple delay times are used to simulate different distances, then calibration accuracy is improved, but system complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the calibration process into multiple discrete delay time segments. Instead of attempting to solve the entire calibration problem at once, the system segments the distance range into multiple simulation distances, each corresponding to a specific delay time. The calibration data from these segmented measurements are then combined to create a comprehensive correction model, improving accuracy without overwhelming system complexity.
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 allows for accurate time-of-flight distance measurement without human intervention, reducing operational complexity and improving measurement accuracy by eliminating offset errors, and enabling easy calibration.
Implementation Method 1
a light-emitting unit, coupled to the delay unit and configured to generate a plurality of delayed pulsed lights according to the plurality of delayed pulses
Implementation Method 2
a photosensitive pixel circuit, configured to receive a plurality of delayed reflected lights corresponding to the plurality of delayed pulsed lights to generate a plurality of pixel signals
Data Source
AI summary
The present application provides a time-of-flight distance measuring system (10), including a delay unit (12) configured to generate a plurality of delayed pulses according to a plurality of delay signals, wherein the plurality of delay signals correspond to a plurality of delay times; a light-emitting unit (13), configured to generate a plurality of delayed pulsed lights according to the plurality of delayed pulses; a photosensitive pixel circuit (14), configured to receive a plurality of delayed reflected lights to generate a plurality of pixel signals; a storage unit (16), configured to store a correspondence between the plurality of delay times and the plurality of pixel signals; and a control unit (18), configured to generate the plurality of delay signals; wherein, the time-of-flight distance measuring system performs a time-of-flight distance measuring according to the correspondence between the plurality of delay times and the plurality of pixel signals.