Dynamic Gain Control for Distance Measuring Receiver
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Solution Overview
Problem
Conventional distance measuring devices face challenges with wide dynamic ranges in return signals, leading to saturation, noise, and reduced accuracy, and require expensive custom components for high dynamic range, limiting measurement rate and efficiency.
Innovation Solution
The use of a variable optical or electrical attenuator/amplifier to regulate the optical power in the time domain, adjusting gain based on elapsed time since the optical pulse emission, reduces the dynamic range requirements of the readout electronics and maintains measurement accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional readout electronics are used to detect reflected light pulses, then the device structure remains simple, but the dynamic range is limited (about 25 dB) causing saturation when return signal amplitude varies by 60-100 dB
Solution Approach 1:
The patent applies dynamics by making the gain of the readout electronics variable rather than fixed. A control unit dynamically adjusts the gain based on the detected amplitude of the return signal, allowing the system to adapt to signals spanning 60-100 dB dynamic range without saturation. This transforms a static system into a dynamic one that can handle varying signal conditions.
Solution Approach 2:
The patent changes the parameter of gain in the readout electronics from a fixed value to a variable value that can be adjusted in response to signal conditions. By modifying the gain parameter dynamically based on detected signal amplitude, the system extends its effective dynamic range beyond the inherent 25 dB limitation of conventional electronics.
2Measurement precision
If a two-step measurement with variable gain is performed to handle wide dynamic range, then measurement accuracy improves, but measurement rate decreases and overall efficiency is reduced
Solution Approach 1:
The patent applies preliminary action by performing a first measurement step to detect the amplitude of the return signal before performing the second measurement step to determine distance. This preliminary detection of signal strength allows the system to adjust gain appropriately for accurate distance measurement, solving the dynamic range problem without requiring separate two-step measurements for different gain settings.
Solution Approach 2:
The patent maintains continuity of useful action by integrating the amplitude detection and distance measurement into a continuous process rather than requiring separate two-step measurements. The system continuously monitors signal amplitude and adjusts gain in real-time, allowing uninterrupted distance measurements at high measurement rates while maintaining accuracy across wide dynamic ranges.
3Ease of manufacture
If high-speed A/D converters with limited dynamic range (25 dB) are used, then the device remains cost-effective and simple, but measurements with return signals varying by 60-100 dB suffer from saturation or excessive noise
Solution Approach 1:
The patent introduces an intermediary element - a variable gain amplifier controlled by a control unit - between the return signal detection and the A/D converter. This intermediary adjusts the signal amplitude to match the limited dynamic range of the A/D converter, preventing saturation while maintaining measurement reliability across 60-100 dB signal variations without requiring expensive high-dynamic-range converters.
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 increases the dynamic range of the receiver, reduces measurement time, and enhances scanning rate and resolution without the need for expensive components, improving overall efficiency and cost-effectiveness.
Implementation Method 1
an optical radiation source (2) adapted to emit optical pulses (2a)... a receiver unit (3) adapted to receive reflected optical pulses (3a)
Implementation Method 2
The use of a variable optical or electrical attenuator/amplifier to regulate the optical power in the time domain, adjusting gain based on elapsed time since the optical pulse emission
Implementation Method 3
a time-measuring unit (4) adapted to measure a traveling time of at least one optical pulse emitted from the optical radiation source (2)
Data Source
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AI summary
It is disclosed an optical device that may be employed in distance measuring devices, the optical device comprising a control unit that is adapted to cause at least one control signal generator unit to generate at least one control signal according to a predetermined temporal function on the basis of an elapsed time from a predetermined point in time. On the basis of the generated at least one control signal, at least one parameter of a receiver unit may be adjusted during the travel time of the optical pulse, wherein the at least one parameter affects the dynamic range of the receiver unit. In this way, the dynamic range of the receiver unit may be increased. It is further disclosed a method for operating such an optical device, a distance measuring device comprising such an optical device and a surveying instrument comprising such a distance measuring device.