AMCW Lidar Mixed Pixel Separation via Multi-Frequency Correlation
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Solution Overview
Problem
AMCW lidar systems face issues with mixed pixels, multipath, and crosstalk, which result in erroneous range and intensity measurements due to multiple objects at different distances contributing to a single pixel's signal, causing phase shifts and intensity changes.
Innovation Solution
The method involves emitting first and second modulation signals at different frequencies, sampling the correlation of the backscattered signal, and using a processor to determine range and intensity characteristics by comparing these measurements, including those at non-zero frequencies and the zeroth spatial frequency, with phase and intensity normalization to reduce the effects of mixed pixels and crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If a single range/intensity measurement is composed of multiple objects at different distances, then the system can capture more scene information in a single pixel, but mixed pixels, multipath, and crosstalk occur causing erroneous range and intensity values
Solution Approach 1:
The patent segments the mixed signal from multiple objects by taking measurements at two or more different modulation frequencies. Each frequency provides a different phase relationship for signals from objects at different distances, allowing the processor to separate and identify individual component returns within a pixel through frequency-based signal decomposition
Solution Approach 2:
The patent adds a frequency dimension to the measurement process by conducting range imaging at multiple modulation frequencies. This transforms the problem from a single 2D measurement (range and intensity) to a 3D measurement space that includes frequency as an additional dimension, enabling separation of mixed pixel contributions
2Measurement precision
If measurements are taken at two or more different modulation frequencies, then component returns can be separated to reduce mixed pixel effects, but the complexity of the measurement and processing system increases
Solution Approach 1:
The patent merges multiple measurements taken at different frequencies into a unified processing framework. The processor combines the frequency-domain data from multiple measurements to extract component return information, effectively merging the information content while managing system complexity through integrated signal processing
Solution Approach 2:
The patent creates multiple copies of the range imaging measurement at different modulation frequencies. Each frequency provides a redundant but differently phased version of the scene information, allowing the system to copy the measurement process across frequency domains to achieve separation of mixed 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
This approach accurately determines the range and intensity properties of objects within a pixel by minimizing the impact of mixed pixels and crosstalk, leading to improved measurement accuracy and reduced errors in range imaging systems.
Implementation Method 1
the illuminator is operable to illuminate the at least one object by the first modulation signal, wherein the first modulation signal is backscattered from the at least one object to create a first backscattered signal
Implementation Method 2
the sensor comprises at least one pixel and is operable to create a sampled correlated signal by sampling the correlation of the first backscattered signal with the second modulation signal within the at least one pixel
Data Source
AI summary
An apparatus for measuring intensity and/or range characteristics of an object(s), comprising: a signal source to emit modulation signals at a frequency(s); an illuminator to illuminate the object(s) by a first modulation signal; a sensor comprising a pixel(s), wherein the sensor creates a sampled correlated signal by sampling the correlation of a backscattered signal with a second modulation signal within the pixel; and a processor to determine range/intensity characteristics of component returns within the pixel(s) by comparing sampled correlated signals using measurements(s), wherein the measurement(s) comprise first and second modulation signals having a characteristic(s) selected from: (a) two or more different modulation frequencies, (b) a different modulation frequency(s) and an offset of the correlation waveform, and (c) another different modulation frequency(s) and one selected from: the zeroth spatial frequency of the signal returns versus range and an approximation of the zeroth spatial frequency of the signal returns versus range.