Electronic Distance Meter Optical Guide for High Peak Power Reflections
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Solution Overview
Problem
Existing electronic distance meters face challenges in accurately measuring distances to target objects with extremely large peak power reflections due to signal degradation from high peak power pulsed light, leading to inaccurate round-trip time calculations.
Innovation Solution
The electronic distance meter employs a combination of multi-mode graded index fiber and multi-mode step index fiber in the optical path extender, with a lower limit of 50 mm for the step index fiber, to guide and disperse the reflected pulsed light, preventing signal degradation and maintaining waveform integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-mode graded index fiber is used to transmit reflected pulsed light, then waveform changes are prevented over long transmission distances, but signal degradation occurs when the target object reflects extremely large peak power
Solution Approach 1:
The optical guide is divided into two segments: a first optical guide (graded index fiber) connected to the light receiving element, and a second optical guide (step index fiber) connected to the light receiving system. This segmentation allows each segment to perform its specialized function - the graded index fiber maintains waveform integrity while the step index fiber handles high peak power dispersion.
Solution Approach 2:
The step index fiber acts as an intermediary component between the light receiving system and the graded index fiber. It receives the reflected light with extremely large peak power, disperses it to prevent degradation, and then transmits it to the graded index fiber for waveform-preserving transmission to the light receiving element.
2Reliability
If the step index fiber length is increased to disperse peak power, then signal degradation is prevented, but transmission distance increases causing waveform changes
Solution Approach 1:
Different sections of the optical guide have different local qualities optimized for different functions. The step index fiber section has high mode dispersion properties ideal for peak power dispersion, while the graded index fiber section has waveform-preserving properties ideal for accurate distance measurement. Each section's length and characteristics are locally optimized for its specific role.
Solution Approach 2:
The patent specifies that the step index fiber length should be 1 mm to 100 mm, with 5 mm to 50 mm being more desirable. By controlling the length parameter within these ranges, the system achieves optimal balance between peak power dispersion and waveform preservation, preventing both signal degradation and excessive waveform changes.
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 configuration allows for precise distance measurement by reducing peak power dispersion and maintaining waveform integrity, even with high peak power reflections, enhancing the accuracy and reliability of distance calculations.
Implementation Method 1
an optical guide which guides the light condensed by the light receiving system to the light receiving element, including a multi-mode graded index fiber and a multi-mode step index fiber coupled with each other
Implementation Method 2
A mode dispersion amount in the multi-mode step index fiber is larger than a mode dispersion amount in the multi-mode graded index fiber
Data Source
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Figure 2
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AI summary
An electronic distance meter includes an optical unit which emits light to a target object and receives the light reflected by the target object with a light receiving element, a measuring unit which calculates a length of round-trip time taken for the light to reciprocatively travel to the target object and measures a distance to the target object according to the round-trip time of the received light, a light receiving system which receives and condenses the light reflected by the target object, and an optical guide which guides the light condensed by the light receiving element to the light receiving system, including a multi-mode graded index fiber and a multi-mode step index fiber coupled with each other.