Distance Measurement Instrument Deflection Module Attenuation
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Solution Overview
Problem
Electronic distance measurement (EDM) units face challenges in achieving faster scanning and adapting to the dynamic range of power levels in distance measurements, particularly in surveying instruments, where the power level of received pulses can vary significantly with distance, leading to saturation issues in detection elements.
Innovation Solution
Incorporating a deflection module that deflects the transmit and receive paths at a specific angle relative to the optical axis, coupled with a processor unit that applies a time-dependent attenuation function based on the deflection angle to improve detection sensitivity and accurately determine distance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the power level of received pulses is measured over a large dynamic range, then distance measurements can be made from both near and far targets, but detection elements become saturated due to the high power levels of nearby targets
Solution Approach 1:
The patent applies preliminary action by implementing time-dependent attenuation that is applied in advance based on predicted return times. The system calculates expected return times for different distances and pre-applies appropriate attenuation levels before the actual signal arrives, preventing saturation while maintaining sensitivity for distant targets
Solution Approach 2:
The patent implements dynamics by using time-dependent attenuation that dynamically adjusts the attenuation level based on the expected return time of the light signal. The attenuation function changes over time, being more aggressive for early-arriving signals (near targets) and less aggressive for later-arriving signals (distant targets), allowing the system to adapt to varying power levels throughout the measurement cycle
2Measurement precision
If traditional attenuation methods are used without time-dependency, then the device complexity is lower, but the detection sensitivity is insufficient for accurate distance measurements across varying power levels
Solution Approach 1:
The patent applies feedback by using the measured time of flight information to adjust the attenuation levels for subsequent measurements. The system continuously monitors return times and uses this feedback to optimize the time-dependent attenuation function, improving detection sensitivity while maintaining a relatively simple device architecture
Solution Approach 2:
The patent implements parameter changes by varying the attenuation parameter as a function of time rather than using a fixed attenuation value. This allows the system to maintain high detection sensitivity across different power levels by dynamically changing the attenuation parameter based on the expected signal characteristics at different time points
3Measurement precision
If surveying instruments operate at lower repetition rates to allow amplitude determination and attenuation setting, then measurement accuracy is maintained, but scanning speed is reduced
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-setting the time-dependent attenuation function based on known operational parameters before measurements begin. This eliminates the need for time-consuming amplitude determination and attenuation setting during the measurement process, allowing the instrument to operate at higher repetition rates while maintaining accuracy
Solution Approach 2:
The patent implements dynamics by enabling the instrument to dynamically switch between different time-dependent attenuation functions based on the current measurement mode (scanning vs. precise measurement). This allows the system to optimize for speed during scanning operations while maintaining precision when detailed amplitude determination is required
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 detection sensitivity by compensating for the dynamic range of power levels, reducing saturation effects and allowing for more precise distance calculations, enabling faster scanning and improved measurement accuracy in surveying instruments.
Implementation Method 1
In time-of-flight distance measurement, the time delay between emission and reception of a laser pulse allows for distance calculation. An emitted pulse travels to a target, e.g. a reflector, and back to a detector where it is received. The time delay between emission and reception of the laser pulse is proportional to the pulse travel distance.
Implementation Method 2
The receiver unit is configured to receive at a receive time a return light signal along a receive path and to convert the return light signal to a return electrical signal.
Data Source
AI summary
A distance measurement instrument and a method of operating a distance measurement instrument are disclosed. According to some embodiments, a transmit light signal is transmitted by a transmitter unit along a transmit path at an emission time and a return light signal is received by a receiver unit at a receive time along a receive path. The return light signal is converted to a return electrical signal. At least one of the transmit path and the receive path is deflected by a deflection module at a deflection angle relative to an optical axis of the instrument. A time-dependent attenuation function is selected based on information relative to the deflection angle and attenuation is applied by an attenuator to at least one of the return light signal and the return electrical signal according to the selected time-dependent function. A measured distance may be determined by a processor unit based on at least the emission time and the receive time.