TOF Sensor Calibration Using Stray Reflections
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Solution Overview
Problem
Existing optical time-of-flight (TOF) sensing systems face inaccuracies due to inherent delays in system electronics, which are exacerbated by stray reflections, leading to uncertainties in depth mapping measurements.
Innovation Solution
The system calibrates TOF measurements by measuring the delay of stray reflections to account for inherent delays in the electronics, allowing for accurate computation of the time of flight by subtracting the baseline delay from actual measurements, thus enhancing the accuracy of depth mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical time-of-flight measurement is used for depth mapping, then depth information can be obtained, but measurement precision deteriorates due to inherent delays in system electronics and stray reflections
Solution Approach 1:
The patent converts the harmful stray reflections into a useful calibration signal. By measuring the time delay of stray reflections (which are caused by electronic delays in the system), the system can calculate a baseline delay value that is then subtracted from the total measured time of flight. This transforms the previously harmful electronic delays into a correctable parameter, enabling accurate depth measurement.
Solution Approach 2:
The system uses the stray reflection measurements to generate feedback about the electronic delays in the system. By continuously monitoring the time delay of stray reflections and using this information to adjust the time of flight calculations, the system compensates for electronic delays in real-time, improving measurement precision.
2Measurement precision
If additional calibration hardware is added to correct for electronic delays, then measurement precision improves, but device complexity increases
Solution Approach 1:
The system performs self-calibration by using its own stray reflections to determine the electronic delays. Instead of requiring external calibration equipment or additional hardware, the system uses the stray reflections that are already present in the optical path to measure and compensate for electronic delays, thereby improving accuracy without increasing device complexity.
Solution Approach 2:
The stray reflection measurement serves multiple functions: it characterizes the electronic delays in the system, provides calibration data for time of flight measurements, and enables compensation for measurement errors. This multi-functional use of the stray reflection signal eliminates the need for separate calibration hardware.
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 improves the accuracy of depth mapping by effectively eliminating inaccuracy introduced by system electronics delays, using existing components without additional hardware, and dynamically adjusts for changes in baseline delays over time.
Implementation Method 1
a receiver, which is configured to receive reflections of the optical pulses and to output electrical pulses in response thereto
Implementation Method 2
to generate a measure of a time of flight of the optical pulses to and from points in the scene by taking a difference between the respective first and second times of output of the first and second electrical pulses
Data Source
AI summary
Sensing apparatus includes a transmitter, which emits a beam comprising optical pulses toward a scene, and a receiver, which receives reflections of the optical pulses and outputs electrical pulses in response thereto. Processing circuitry is coupled to the receiver so as to receive, in response to each of at least some of the optical pulses emitted by the transmitter, a first electrical pulse output by the receiver at a first time due to stray reflection within the apparatus and a second electrical pulse output by the receiver at a second time due to the beam reflected from the scene, and to generate a measure of a time of flight of the optical pulses to and from points in the scene by taking a difference between the respective first and second times of output of the first and second electrical pulses.