TOF Camera Multipath Error Correction via Dark Area Detection
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Solution Overview
Problem
Time of flight (TOF) cameras experience erroneous distance measurements due to the 'multipath' phenomenon, where external objects cause large distance measurement values, leading to incorrect determination of monitored objects' presence or absence in the monitoring area, especially when external objects are placed near the monitoring area after installation.
Innovation Solution
An object monitoring system that uses a TOF camera to determine the arrangement relationship and influence degree of external objects on the distance measurement within the monitoring area by calculating the phase difference and light intensity values, outputting warning signals when the influence exceeds set thresholds, and displaying the influence degree on the monitoring area's image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If TOF camera measures distance using phase difference method, then distance measurement capability is achieved, but multipath phenomenon causes erroneous large distance measurement values
Solution Approach 1:
The patent replaces physical light path control mechanisms with image processing and calculation methods. Specifically, it uses dark area detection in captured images to identify multipath-affected regions, and applies computational algorithms to correct distance measurement values based on the detected dark areas, thereby eliminating multipath errors without modifying the optical system.
Solution Approach 2:
The patent introduces dark area detection as an intermediary step between light capture and distance calculation. By detecting dark areas in the captured image that indicate multipath reflection, the system can identify and correct erroneous measurement points before final distance determination, acting as a mediator to filter out multipath interference.
2Area of stationary object
If external objects are present near monitoring area, then monitoring coverage is maintained, but distance measurement values become erroneously large leading to incorrect object presence determination
Solution Approach 1:
The patent implements a feedback mechanism where the captured image is analyzed to detect dark areas indicating multipath effects. This detection feedback is then used to correct the distance measurement values, creating a closed-loop system that continuously monitors and corrects for external object interference, thereby maintaining reliable object presence determination even when external objects are present.
Solution Approach 2:
The patent performs preliminary detection of dark areas in the captured image before final distance measurement determination. By identifying multipath-affected regions in advance through dark area detection, the system can pre-correct measurement values or flag affected areas, preventing erroneous object presence/absence determination before it occurs.
3Duration of action of stationary object
If monitoring system operates continuously after installation, then ongoing object detection is provided, but external objects arranged after installation cause erroneous measurements
Solution Approach 1:
The patent enables continuous multipath correction by continuously analyzing captured images for dark areas and applying corrections to distance measurements in real-time. This continuous operation ensures that regardless of when external objects are introduced into the monitoring area, the system maintains accurate distance measurements through ongoing detection and correction, preserving measurement precision throughout the entire monitoring duration.
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
Accurately assesses the influence of external objects on distance measurements, preventing erroneous object presence determinations and allowing for corrective actions, such as moving external objects, thereby ensuring reliable monitoring area integrity.
Implementation Method 1
the measurement value of the target space is output based on a phase difference between the irradiated measurement light and the light reflected from the target space
Implementation Method 2
TOF (time of flight) cameras which output a distance on a basis of the time of flight of light as distance measuring devices
Implementation Method 3
the phenomenon (so-called 'multipath') wherein distance measurement values are erroneously large when certain distance measurement points are strongly influenced by reference light which has been multi-reflected via other objects
Data Source
AI summary
An object monitoring system includes means for determining an arrangement relationship between a monitoring area and an external object on a basis of a distance measurement value of the external object, and calculating an influence degree of the external object on an object distance measurement in the monitoring area in accordance with the determined arrangement relationship.