Handheld Metal Detector Depth Measurement Using Optical Flow
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Solution Overview
Problem
Current metal detectors face challenges in accurately determining the depth of buried targets due to environmental factors, soil complexity, and variations in target size and type, leading to false alarms and inefficient excavation processes.
Innovation Solution
A handheld metal detector equipped with a horizontal position tracking unit using the optical flow method, combined with sensors like optical flow sensors, IMU, and height sensors, processes metal detection signals to calculate target depth independently of target type and size, correcting for user movements and ground irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal intensity is used to predict target depth with constant target assumptions, then depth estimation can be made, but accuracy decreases when target size or type changes
Solution Approach 1:
The patent applies dynamics by transitioning from static depth estimation (based on fixed target assumptions) to dynamic tracking of signal variations as the search head moves. The system continuously monitors signal intensity changes during horizontal movement to calculate depth, adapting to different target types and sizes through real-time signal analysis rather than relying on pre-calibrated static values.
Solution Approach 2:
The patent changes the approach from using absolute signal intensity values to analyzing signal variation patterns and derivatives. By examining how the signal changes during movement (first and second derivatives), the system can determine depth independently of target type and size, effectively changing the measurement parameter from static intensity to dynamic variation rate.
2Measurement precision
If multiple sensors and processing units are added to improve depth measurement accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent makes the position tracking unit multi-functional by using it for both horizontal position tracking and depth measurement. The same sensors (optical flow sensors, IMU, height sensors) that track the search head's position are also used to calculate depth by analyzing signal variations during movement. This eliminates the need for separate dedicated depth sensors and reduces overall system complexity.
Solution Approach 2:
The patent merges the position tracking function with the depth measurement function into a single integrated system. The processor unit combines position data from optical flow sensors, IMU, and height sensors with metal detection signals to simultaneously determine both location and depth, reducing the number of separate components needed.
3Adaptability or versatility
If horizontal position tracking with optical flow method is used, then depth calculation becomes independent of target type and size, but device complexity increases due to additional sensors
Solution Approach 1:
The position tracking unit performs multiple functions: horizontal position tracking, vertical height measurement, and depth calculation. By making these components multi-functional, the patent reduces the need for separate dedicated sensors for each function, thereby mitigating the increase in device complexity while achieving target-type-independent depth measurement.
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 solution provides accurate and reliable depth measurements, reducing the time and effort required for excavation by minimizing false alarms and improving target detection precision across varying environmental conditions.
Implementation Method 1
A handheld metal detector equipped with a horizontal position tracking unit using the optical flow method
Implementation Method 2
At least one contactless distance sensor providing height measurement to detect elevation changes
Implementation Method 3
gyroscope, accelerometer and magnetometer combination (IMU) sensors are used to detect angular displacements resulting from axial movements
Implementation Method 4
the intensity of the signal received from the target varies with an inverse proportion to the distance of the target
Data Source
AI summary
The present invention, thanks to the horizontal positional tracking unit (20)—mounted to a hand-held metal detector (10)—consisting of optical flow sensor lens (22), an optical flow sensor camera (21), an optical flow sensor processor (23), a height sensor (24) and an IMU sensor (25); allows the calculation of the depth of the target (60) by tracking the horizontal position while the user freely sweeps the search head (11) of the metal detector (10) with the “optical flow” method and using the metal detection signals received from many point positions around the detected target center with this position; so it relates to a method of measuring a target depth and a metal detector using this method, which allow calculation to be made independently of the type and practical the size of the metal.