Adjustable Aperture Mitigates Multipath Interference in Time-of-Flight Dimensioning
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Solution Overview
Problem
Time-of-flight (TOF) dimensioning systems suffer from multipath distortion in mobile environments due to large field of view, leading to dimensioning errors, as light beams reach items via multiple paths, causing reflections that result in inaccurate distance measurements.
Innovation Solution
A TOF dimensioning system with an adjustable aperture that limits the spatial extent of the light beam based on image analysis of the item, ensuring the light beam reaches the item directly without reflections, using components like liquid crystal displays or digital micro-mirror devices to control the illumination pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large field of view is used in TOF dimensioning systems, then the system can capture more of the scene and item, but multipath distortion increases leading to dimensioning errors
Solution Approach 1:
The patent segments the field of view by using an adjustable aperture to divide the large FOV into a smaller region of interest that precisely matches the item boundaries. This segmentation allows the system to maintain a large overall FOV capability while selectively illuminating only the relevant area, thereby preventing multipath distortion from out-of-bound reflections.
Solution Approach 2:
The patent applies local quality by configuring the illumination region to have different properties than the rest of the scene. The adjustable aperture creates a localized illumination pattern that concentrates light only on the item of interest, giving that specific region different optical characteristics (direct illumination) compared to the surrounding area (no illumination), thereby eliminating multipath effects.
2Measurement precision
If an adjustable aperture is used to limit the light beam spatial extent, then multipath distortion is reduced, but device complexity increases
Solution Approach 1:
The patent achieves universality by making the aperture serve multiple functions: it acts as both a mechanical component to physically limit the light beam spatial extent and as a control element that can be dynamically adjusted based on item detection. The same aperture mechanism that controls illumination geometry also enables the system to adapt to different item sizes and positions, reducing the need for additional specialized components.
Solution Approach 2:
The patent applies dynamics by making the aperture adjustable rather than fixed. The aperture can dynamically change its configuration in response to detected item characteristics, allowing the system to optimize the illumination region for each specific measurement scenario. This dynamic adjustment capability reduces complexity compared to having multiple fixed apertures or complex optical switching mechanisms.
3Measurement precision
If the light beam spatial extent is reduced to match the item, then multipath interference is minimized, but the system loses ability to measure items of varying sizes
Solution Approach 1:
The patent applies dynamics by making the aperture adjustable rather than fixed. The aperture can dynamically change its configuration in response to detected item characteristics, allowing the system to optimize the illumination region for each specific measurement scenario. This dynamic adjustment capability reduces complexity compared to having multiple fixed apertures or complex optical switching mechanisms.
Solution Approach 2:
The patent applies preliminary action by first detecting the item's position and boundaries using the imager before configuring the aperture and TOF sensor for precise dimensioning. This preliminary detection step allows the system to pre-establish the appropriate illumination region size and position, ensuring the aperture is correctly configured before the actual measurement begins, thereby maintaining both precision and adaptability.
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 effectively reduces multipath distortion, enabling accurate and fast dimensioning of various items in diverse environments by ensuring the light beam only illuminates the item of interest, eliminating errors caused by reflections from the background.
Implementation Method 1
One such optical range sensor employs time-of-flight (TOF) measurements to measure range
Implementation Method 2
If the field of view is large compared to the item of interest, then the light beam may reach the item of interest along several different paths. Some paths, for example, may be experience one or more reflections prior to reaching the item of interest
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A system and method for measuring an item's dimensions using a time-of-flight dimensioning system is disclosed. The system and method mitigate multipath distortion and improve the accuracy of the measurements, especially in a mobile environment. To mitigate the multipath distortion, an imager captures an image of an item of interest. This image is processed to determine an illumination region corresponding item-of-interest's size, shape, and position. Using this information, an adjustable aperture's size, shape, and position are controlled so the light beam used in the time-of-flight analysis substantially illuminates the illumination region without first being reflected.