LIDAR Frequency Modulation for Unambiguous Distance and Speed
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Solution Overview
Problem
Existing LIDAR systems face challenges in accurately determining object distances and speeds in a visual field without complex equipment or processing, as they struggle to unambiguously separate Doppler and distance frequencies within a single frequency ramp.
Innovation Solution
The method employs a laser device with an optical modulator for frequency modulation, optically superimposing secondary light with non-modulated light to form detection light, and electronically mixing the detection signal with the modulation signal to generate a beat frequency, which represents the sum of Doppler and distance frequencies, allowing for precise determination of object parameters using FMCW technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single frequency ramp is used for distance measurement, then the measurement process is simplified and speed is improved, but the ability to unambiguously determine both distance and speed deteriorates
Solution Approach 1:
The patent segments the frequency modulation function into multiple segments (first segment and second segment) with different slopes. By comparing the beat frequencies from these different segments, the system can unambiguously determine both distance and speed parameters that would be indistinguishable in a single frequency ramp measurement.
Solution Approach 2:
The patent employs periodic frequency modulation with alternating segments of different slopes. This periodic variation in modulation slope allows the system to capture multiple measurements over time, enabling the separation of distance and speed components through comparison of beat frequencies from different periods.
2Loss of information
If FMCW method is used, then information flow is increased, but the complexity of separating Doppler and distance frequencies increases
Solution Approach 1:
The patent uses feedback by comparing the beat frequency from the first frequency ramp segment with the beat frequency from the second segment. This feedback mechanism allows the system to resolve the ambiguity between Doppler and distance frequencies by iteratively determining which combination of parameters matches the observed beat frequencies from both segments.
Solution Approach 2:
The patent dynamically adjusts the evaluation process by first determining a preliminary distance value from the first segment, then using this information to evaluate and resolve the speed and distance parameters from the second segment. This dynamic, multi-stage evaluation reduces processing complexity compared to attempting to solve all parameters simultaneously.
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 enables accurate and efficient detection of object distances and speeds within a single frequency ramp, reducing the need for additional measurements and equipment, and allows for unambiguous association of distances and speeds, even with multiple targets in the scene.
Implementation Method 1
a laser device that includes an optical modulator, coupled thereto, for receiving and for modulating the frequency of non-modulated light emitted by the laser device, using a frequency modulation function
Implementation Method 2
secondary light received from the visual field and non-modulated light of the laser device are optically superimposed to form superimposed detection light
Implementation Method 3
the superimposed detection light is photoelectrically detected by generating and outputting a primary electrical detection signal
Implementation Method 4
for the evaluation, the primary electrical detection signal is electrically mixed with an electrical signal that is representative of the frequency modulation function of the optical modulator to form a first evaluation signal
Implementation Method 5
The beat frequency is understood in particular as the sum of a Doppler frequency that is representative of a speed of an object in the visual field, and a distance frequency that is representative of a distance of the object
Data Source
AI summary
An operating method for a LIDAR system. A laser device that includes an optical modulator optically coupled thereto for receiving and modulating the frequency of non-modulated light emitted by the laser device, using a frequency modulation function, and for outputting frequency-modulated light as primary light into a visual field, is used as a light source unit. Secondary light received from the visual field and non-modulated light of the laser device are optically superimposed to form superimposed detection light. The superimposed detection light is photoelectrically detected by generating and outputting a primary electrical detection signal that is representative of the detection light. For the evaluation, the primary electrical detection signal is electrically mixed with an electrical signal that is representative of the frequency modulation function of the optical modulator to form a first evaluation signal, and is assessed.