TOF Sensor Multipath Interference Correction
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Solution Overview
Problem
Time-of-flight (TOF) optical sensors face errors in distance measurements due to multipath illumination interference (MPII), where objects receive light via direct and indirect paths, leading to distorted signals and inaccurate distance calculations.
Innovation Solution
The TOF sensor models background objects as arrays of elementary point sources, estimates indirect irradiance contributions to target objects, and corrects distance values by subtracting the estimated indirect irradiance from measured signals, thereby isolating the direct illumination path and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional TOF sensors measure distance based on received light signals, then distance values can be obtained, but measurement precision deteriorates due to multipath illumination interference
Solution Approach 1:
The patent segments the received light signal into direct illumination components and indirect illumination components. By modeling the indirect irradiance separately and subtracting it from the total measured signal, the system isolates the direct path contribution, thereby improving distance measurement accuracy in the presence of multipath interference
Solution Approach 2:
The patent extracts the harmful indirect illumination component from the total received signal. Through elementary point source modeling and irradiance integration, the system identifies and removes the multipath interference contribution, leaving only the direct illumination signal for accurate distance calculation
2Measurement precision
If the sensor models background objects as elementary point sources and calculates indirect irradiance, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent creates a computational model (copy) of the background object as an array of elementary point sources. This virtual representation allows the system to calculate indirect irradiance contributions without physically modeling the actual object, enabling accurate multipath correction through mathematical computation rather than physical measurement
Solution Approach 2:
The patent transforms the complex problem of multipath interference correction into a series of parameter-based calculations. By defining parameters such as point source positions, irradiance values, and integration weights, the system systematically computes and subtracts indirect illumination effects, making the complex computational task manageable and structured
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 enhances the accuracy of distance measurements by effectively mitigating the impact of MPII, ensuring reliable object detection and preventing false alarms in industrial safety applications.
Implementation Method 1
a photo-sensor component comprising an array of pixels, wherein respective pixels of the array of pixels are configured to convert a subset of the light pulses received from the monitored scene to electrical energy proportional to the subset of the light pulses received at the pixels
Implementation Method 2
Time-of-flight (TOF) optical sensors face errors in distance measurements
Data Source
AI summary
A three-dimensional (3D) sensor device achieves accurate distance measurements in the presence of multipath illumination interference (MPII) by estimating the effect of indirect illumination on a given pixel's optical signal measurement and correcting the signal measurement to remove the estimated contribution from indirect illumination. After generating an initial point cloud image of a scene, the sensor device identifies target objects and background objects within the scene, where the background objects are potential sources of indirect illumination. The sensor device estimates the total amount of indirect illumination directed to a point on the target object by the background objects and received at a pixel corresponding to the point, and corrects the measured signal at the pixel to remove the contribution of this estimated indirect illumination. The sensor device performs this MPII estimation without a priori knowledge of the background objects' characteristics, and is therefore response to changes in the background.