TOF Ranging Correction for Close-Range Scattering Interference
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Solution Overview
Problem
Existing time of flight (TOF) sensors face significant accuracy issues when close objects interfere with the measurement of distant objects due to light scattering and intensity differences, leading to systematic errors in distance estimation.
Innovation Solution
A ranging method and system that employs scattering detection to calculate pixel scattering coefficients, corrects initial measurement values using these coefficients, and adjusts charge accumulation windows to minimize the influence of close-range objects on far-range measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If TOF sensor performs distance measurement in a detection field with both close and distant objects, then the measurement covers a wide range, but the measurement accuracy of distant objects deteriorates due to light scattering from close objects
Solution Approach 1:
The patent segments the detection process into two distinct phases: a scattering detection phase to measure light scattering coefficients, and a distance measurement phase to obtain initial distance values. This segmentation allows the system to separately characterize and compensate for scattering effects, thereby improving distant object measurement accuracy while maintaining wide detection range capability
Solution Approach 2:
The patent performs scattering detection as a preliminary action before distance measurement. By pre-measuring the scattering coefficients of close objects and storing them, the system prepares the necessary compensation data in advance, which is then applied during the distance measurement phase to correct inaccuracies caused by light scattering
2Device complexity
If TOF sensor uses conventional measurement method, then the system structure is simple, but systematic errors occur due to light scattering from close objects
Solution Approach 1:
The patent introduces scattering coefficients as an intermediary parameter that mediates between the raw detection signals and the final distance measurements. These coefficients act as a correction factor that accounts for light scattering effects, improving measurement reliability without requiring fundamental changes to the TOF sensor structure
Solution Approach 2:
The patent implements a feedback mechanism where scattering coefficients measured in the first phase are used to correct distance measurements in the second phase. This feedback loop continuously compensates for scattering-induced errors, enhancing measurement reliability while maintaining relatively simple system architecture
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
The method effectively reduces systematic errors caused by close-range objects, enhancing the accuracy of distance measurements for far-range objects by correcting measurement values based on scattering coefficients.
Implementation Method 1
Time of flight (TOF) detects a three-dimensional structure or a three-dimensional profile of a detected object by detecting the time interval of the pulse signal sent by the detecting instrument from transmission to reception
Implementation Method 2
the detection light is reflected on the surface of the detected object, and the reflected light is received by the photosensitive module
Implementation Method 3
the detection result of the TOF sensor may produce relatively large errors. For example, when there are both a close object and a distant object in the detection field of view, the detected distance of the distant object will be relatively small
Data Source
AI summary
The present disclosure relates to a time of flight ranging system and a ranging method thereof, the ranging method comprising: performing scattering detection, and obtaining a scattering coefficient of each pixel unit in the sensing array, specifically comprising: emitting scattering detection light into a detection field of view, the detection field of view includes detected objects at different distances and is divided into a close-range area and a far-range area; obtaining a detection value of each pixel unit generated by reflected light and scattered light generated by the reflected light, calculating a ratio of the detection value generated by each pixel unit to a sum of the detection values generated by all pixel units of the entire sensing array as a pixel scattering coefficient corresponding to the pixel unit; performing distance measurement, and obtaining an initial measurement value output by each pixel unit; correcting initial measurement values output by at least part of the pixel units according to the scattering coefficients to obtain corrected measurement values; and calculating corrected measurement distance according to the corrected measurement values. The ranging method can eliminate the influence of a close-range object on the measurement result to a far-range object.