Electro-optic Time-of-flight Receiver Chain Dynamic Range
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Solution Overview
Problem
Existing electro-optic distance meters face limitations in dynamic range, particularly with the threshold value method where weak backscattered pulses are undetectable and the waveform digitization method suffers from signal saturation and receiver electronics limitations, leading to measurement gaps and inaccurate distance determination.
Innovation Solution
An electro-optic distance meter with a receiver chain that includes a photodetector, transimpedance amplifier, and analog-to-digital converter, adapted to operate linearly even under non-linear conditions, allowing for digital signal processing through waveform digitization, signal reconstruction, and time delay determination, enabling accurate measurement across a wide dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the threshold value method is used for signal detection, then noise and interfering signals are prevented from being detected incorrectly, but weak backscattered pulses become undetectable when their intensity falls below the detection threshold
Solution Approach 1:
The patent changes the detection parameter from a fixed threshold value to a dynamic reference signal that adapts to the actual backscattered signal strength. By comparing the received signal against a reference signal of known characteristics rather than a fixed threshold, the system can detect weak pulses while maintaining noise rejection capabilities.
2Measurement precision
If the waveform digitization method is used for signal detection, then weak backscattered pulses can be detected with higher precision, but the receiver electronics become saturated by strong light pulses
Solution Approach 1:
The patent segments the signal processing into two distinct paths: an analog reference signal path that handles strong signals without saturation, and a digitized measurement path that provides high precision for weak signals. The reference signal is processed analogously to establish a robust comparison baseline, while the received signal undergoes waveform digitization for precise timing extraction.
Solution Approach 2:
The patent introduces a reference signal as an intermediary element that mediates between the strong transmitted pulse and the weak backscattered signal. This reference signal serves as a stable comparison standard that enables the system to handle both strong and weak signals simultaneously without saturation or loss of precision.
3Device complexity
If a single receiver chain is used to cover a wide dynamic range, then device complexity is reduced, but measurement accuracy deteriorates due to signal saturation or threshold limitations
Solution Approach 1:
The patent creates a universal receiver chain that performs multiple functions: it processes both strong and weak signals, generates reference signals, and enables both threshold-based and waveform-based detection methods. The single receiver chain is designed to handle the full dynamic range by incorporating signal conditioning circuits that prevent saturation while maintaining sensitivity for weak signals.
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 enables the detection and accurate measurement of both strong and weak light pulses, covering a wide dynamic range with a single receiver chain, improving resolution and precision, and correcting for range walk errors, thus eliminating measurement gaps and providing unambiguous optical and electrical signal relationships.
Implementation Method 1
a photodetector and a (first) gain stage, preferably a transimpedance amplifier or a current-mode electronic, for converting an input current from the photodetector associated to the returned light pulse into an analog output
Implementation Method 2
a (first) gain stage, preferably a transimpedance amplifier or a current-mode electronic, for converting an input current from the photodetector associated to the returned light pulse into an analog output
Data Source
AI summary
An electro-optic distance meter according to the time-of-flight principle with a receiver chain for generating a digital signal from a received light pulse, the receiver chain comprising a photodetector, a first gain stage, in particular a transimpedance amplifier or a current-mode electronic, for converting an input current from the photodetector associated to the returned light pulse into an output voltage, a filter and an analog-to-digital converter, whereby the digital signal provides an unambiguous relationship between intensity-time delay of the optical pulse and signalshape-time delay of the electrical signal, wherefore the photodetector, the first gain stage and the analog-to-digital converter are adapted to each other such that the analog-to-digital converter remains unclipped in a linear operating range even when the first gain stage shows a non-linear time-invariant response or a well-defined time-invariant saturation response to the input current of the photodetector.