Surveying Instrument Reference Light Path Attenuation
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Solution Overview
Problem
Existing surveying devices, such as tachymeters and laser scanners, face challenges in achieving precise distance measurements due to systematic errors caused by varying signal strengths, especially when dealing with objects having reflective or shiny surfaces. The limited dynamic range of previous reference light paths prevents adequate compensation for these errors, particularly at low or high signal intensities.
Innovation Solution
The implementation of an optical reference channel that generates a 'self-illuminating' reference goal with temporally and/or locally varying intensity, allowing for the use of a weakening device to adjust the reference radiation. This configuration ensures that the reference light path has a dynamic range of at least five magnitudes, enabling precise corrections for systematic errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference light path with reflective external reference target is used, then reference measurements can be performed, but parasitic scattered light is coupled into the reference path causing interference and distorting the nominal light transit time
Solution Approach 1:
The patent extracts the reference light path from the external reflective target configuration and relocates it to an internal position within the measuring device. The reference light path is established inside the device housing, using internal reflective surfaces and a light source positioned at a known location, thereby eliminating external environmental contaminants and parasitic scattered light from the reference measurement path.
Solution Approach 2:
The patent introduces an intermediary light guide or optical fiber to transmit the reference light from the internal light source to the detector. This intermediary medium isolates the reference light path from external interference while maintaining a controlled and known light transmission path, preventing parasitic scattered light from affecting the reference measurements.
2Adaptability or versatility
If the signal dynamic range of the measurement light path is greater than the reference light path, then a wide distance range can be covered, but systematic signal strength-dependent measurement errors cannot be adequately compensated
Solution Approach 1:
The patent employs dynamic attenuation elements (such as variable optical attenuators or neutral density filters) in the reference light path that can be adjusted to match the signal strength of measurement signals across different distance ranges. This dynamic adjustment ensures that the reference light path maintains the same signal dynamic range as the measurement path, enabling accurate error compensation across the full operational range.
Solution Approach 2:
The patent changes the optical parameters (intensity, attenuation level) of the reference light path dynamically to match the measurement signal conditions. By adjusting the attenuation of the reference light to correspond to different signal strengths encountered during measurement, the system maintains parameter consistency between reference and measurement paths, enabling accurate compensation of signal strength-dependent errors.
3Measurement precision
If prisms with known varying brightnesses are used for reference measurements, then measurement errors dependent on signal intensity can be detected, but the attenuation achievable is limited due to high reflectivity of prisms
Solution Approach 1:
The patent replaces the mechanical prism-based attenuation system with electronic or electro-optical attenuation mechanisms. Instead of using prisms with fixed reflectivity characteristics, the system employs electronically controllable attenuators (such as liquid crystal可变 attenuators or acousto-optic modulators) that can provide continuous and extensive attenuation ranges, overcoming the limited attenuation capability of passive prism systems.
Solution Approach 2:
The patent changes the attenuation mechanism from passive geometric reflection (prisms) to active controllable attenuation. By using variable optical attenuators that can be electronically adjusted, the system achieves a much wider attenuation range while maintaining the ability to create reference measurements at different signal intensities, thereby improving both error detection capability and attenuation versatility.
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
The solution allows for trouble-free reception signals across a wide dynamic range, enabling exact corrections of distance measurement values. This results in improved precision and accuracy of distance measurements, even for signals with small or large amplitudes.
Implementation Method 1
an optical transmission channel (5) with a transmitting unit (7) and an optical receiving channel (17) with an optical inlet element (18) and a receiving unit (17). The optical transmission channel (5) has at least one optical fiber (23, 24)
Implementation Method 2
a measuring light path (5) for laser measuring radiation is formed between the transmitting channel and the receiving channel
Implementation Method 3
a receiving unit (17) for receiving laser measuring radiation
Data Source
Figure 1~2
Figure 3~4
Figure 5~9
AI summary
A surveying instrument (1) for performing distance measurements to an object, comprising an optical transmitting channel, an optical receiving channel, a reference light path (6), and an evaluation unit. The optical transmitting channel includes a transmitting unit (7) and an optical outlet element (20), and the optical receiving channel includes an optical inlet element (18) and a receiving unit (17). The surveying instrument (1) enables distance measurements via a measuring light path (5) to and from the object and via a reference light path (6). An attenuator (11) achieves the desired signal attenuation in the reference light path. The reference light path (6) is designed to receive laser measurement radiation before it passes through the optical outlet element (20), guides it to the attenuator (11) without contact with the surroundings, and transmits an attenuated portion through the optical inlet element (18) to the receiving unit (17).