Handheld Rangefinder Distance Stabilization via Motion Sensor Filtering

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Solution Overview

Problem

Handheld observation devices with rangefinders face challenges in maintaining accurate distance measurements due to instability and movement during use, leading to incorrect or imprecise readings, especially at long distances, as they rely on combining signal information from multiple pulses which can be affected by noise and incorrect targeting.

Innovation Solution

The device employs a motion sensor to detect instability and control the rangefinder, ensuring that only signal information from pulses meeting specific criteria related to the device's spatial position is used for distance measurement, thereby stabilizing the measurement process and improving signal quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple pulses are combined for distance measurement to improve signal quality, then measurement reliability improves, but measurement precision deteriorates due to device movement and instability during the measurement period

Engineering Contradiction:
Improvemeasurement reliabilityVSAvoiddistance measurement precision
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The patent determines the mean value of the oscillation before the distance measurement takes place. This preliminary determination of the central area of oscillation allows the system to establish a reference frame for selecting valid pulses, ensuring that only pulses corresponding to the intended target are used while excluding those affected by device movement.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent applies different quality criteria to different pulses based on their temporal association with device stability. Pulses are evaluated individually based on whether their instantaneous oscillation values fall within the predetermined range around the central area. This local quality assessment ensures that only high-quality pulses from stable periods contribute to the distance measurement.

Inventive Principle:
Principle #3Local quality

2Loss of information

If the measurement time window is extended to accumulate more signal information, then signal-to-noise ratio improves, but device instability increases leading to incorrect targeting

Engineering Contradiction:
Improvesignal information accumulationVSAvoidtargeting accuracy
Core Design Contradiction:
Loss of informationVSMeasurement precision

Solution Approach 1:

The patent uses a minimum number of pulses (e.g., 50 or 100) to determine distance, which may be fewer than the total pulses available during the extended time window. This partial action approach ensures sufficient signal accumulation while avoiding the inclusion of pulses from periods of excessive device movement, thus maintaining targeting accuracy.

Inventive Principle:
Principle #16Partial or excessive action

Solution Approach 2:

The system preliminarily determines the central area of oscillation and establishes selection criteria before the measurement begins. This allows the system to pre-identify which pulses will be valid, enabling the extension of the measurement window without compromising accuracy, as invalid pulses can be easily excluded based on pre-established criteria.

Inventive Principle:
Principle #10Preliminary action

3Measurement precision

If device movement compensation is implemented to maintain targeting accuracy, then measurement precision improves, but device complexity increases

Engineering Contradiction:
Improvetargeting accuracyVSAvoidsystem complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical stabilization systems with an electronic/software-based solution. Instead of using moving components to physically stabilize the device, the system uses a motion sensor and electronic processing to detect and compensate for device movement by selecting appropriate pulses for measurement, significantly reducing mechanical complexity.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The device uses its own motion sensor data to automatically compensate for its movements without requiring external stabilization equipment. The system self-regulates by using the detected oscillation patterns to determine which pulses are valid, making the device self-sufficient and avoiding additional complex stabilization mechanisms.

Inventive Principle:
Principle #25Self-service

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 and reliability of distance measurements by filtering out unstable signal information, reducing noise, and ensuring that only relevant data from the intended target is used, leading to more precise and reliable distance determination even under adverse conditions.

Implementation Method 1

a motion sensor (17) for detecting an instability of a spatial position of the observation device (99)

Methodology Applied
Scientific EffectMotion detection: Accelerometer

Implementation Method 2

a transmitter unit (5) for emitting a temporal sequence of pulses of optical radiation (10)

Methodology Applied
Scientific EffectOptical radiation emission: Laser

Implementation Method 3

a receiver unit (1) for receiving a portion (12) of the optical radiation (10) reflected by the target object (11)

Methodology Applied
Scientific EffectPhotoelectric conversion: Photoelectric Effect

Implementation Method 4

a electronic evaluation unit (4) with which a distance (13) to the target object (11) can be determined on the basis of a signal propagation time between transmission and reception of the optical radiation (10)

Methodology Applied
Scientific EffectTime of flight measurement: Time of Flight

Data Source

PatentEP2843440B1Stabilised distance measurement in an observation device
Publication Date: 2018.11.28 VECTRONIX AG
  • EP2843440B1 patent drawingFigure 1~2
  • EP2843440B1 patent drawingFigure 3~6
  • EP2843440B1 patent drawingFigure 7~8

AI summary

The invention relates to a handheld observation device with an observation path for optically targeting a target object and with an optoelectronic rangefinder for measuring the distance in the direction of the target. The rangefinder has a transmitter unit for emitting a temporal sequence of pulses of optical radiation, a receiver unit for receiving a portion of the optical radiation reflected by the target object and determining signal information, and an electronic evaluation unit which determines the distance to the target object based on the signal propagation time between the emission and reception of the optical radiation. The distance is determined by manually actuating a trigger, taking into account the signal information from a specific minimum number of pulses, which define a minimum length of a time window for the distance measurement.The observation device has a motion sensor for detecting instability in the spatial orientation of the observation device and a control unit with which the distance meter is controlled based on spatial orientation data from the motion sensor in such a way that the pulses counting towards the minimum number meet predefined criteria with regard to this temporally assigned spatial orientation data.