Surveying Apparatus Multiple Reflection Filtering

Solution Overview

Problem

Laser scanning systems face errors in distance measurement due to multiple reflections, where beams emitted at one time are incorrectly received as reflections from subsequent emissions, leading to incorrect distance calculations.

Innovation Solution

A surveying apparatus and method that determine whether a received beam after the (K+1)th light emission is a repeatedly reflected beam by analyzing the time interval from light emission to reception, using a processor to differentiate between regular and repeatedly reflected beams based on their timing and intensity, and excluding incorrectly received beams from measurement calculations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If laser scanning is used to measure distance, then distance measurement capability is provided, but multiple reflections cause measurement errors

Engineering Contradiction:

Improvedistance measurement accuracyVSAvoidmultiple reflections

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary identification of repeatedly reflected beams by analyzing time intervals between light emission and reception. Before using a received beam for distance calculation, the system checks whether the time interval corresponds to an integer multiple of the period, and if so, excludes it from measurement. This preliminary filtering prevents measurement errors caused by multiple reflections.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback from timing analysis to identify and exclude erroneously received beams. By continuously monitoring the time interval between light emission and reception, and comparing it with the expected period, the system provides feedback to determine whether a received beam should be used for measurement or excluded as a repeatedly reflected beam.

Inventive Principle:

Principle #23Feedback

2Productivity

If beams are received continuously after light emission, then measurement data is obtained, but repeatedly reflected beams are incorrectly identified as valid reflections

Engineering Contradiction:

Improvemeasurement efficiencyVSAvoidbeam identification accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system performs preliminary identification of repeatedly reflected beams by analyzing time intervals between light emission and reception. Before using a received beam for distance calculation, the system checks whether the time interval corresponds to an integer multiple of the period, and if so, excludes it from measurement. This preliminary filtering prevents measurement errors caused by multiple reflections.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses feedback from timing analysis to identify and exclude erroneously received beams. By continuously monitoring the time interval between light emission and reception, and comparing it with the expected period, the system provides feedback to determine whether a received beam should be used for measurement or excluded as a repeatedly reflected beam.

Inventive Principle:

Principle #23Feedback

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 reduces the impact of multiple reflections on distance measurement accuracy by correctly identifying and excluding repeatedly reflected beams, thereby preventing errors in distance calculations and improving measurement precision.

Implementation Method 1

A light emission unit emits pulses of scanning light (distance measuring light)

Methodology Applied

Scientific EffectLight: Light

Implementation Method 2

The scanning light is transmitted through an incident light reflection-and-separation optical system, such as a half mirror or a dichroic mirror

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS20230314610A1Surveying apparatus, surveying method, and surveying program

Publication Date: 2023.10.05 TOPCON CORPORATION

AI summary

Effects of multiple reflections in distance measurement using a laser are reduced. A surveying method for measuring a distance to a reflection point that reflects distance measuring light, based on emission and reception of the distance measuring light, includes assuming that a symbol “K” represents a natural number, excluding zero, and determining whether a beam that is received after the (K+1)th light emission is a repeatedly reflected beam of light that has been emitted before the (K+1)th light emission. The beam that is received, after the (K+1)th light emission, at a time corresponding to a period based on a time interval from light emission at or before the Kth light emission until first reception of a beam related to the light emission at or before the Kth light emission, is determined as being the repeatedly reflected beam.