Dispersive Laser Scanning for Long-Range LIDAR Distance Measurement
Solution Overview
Problem
Existing LIDAR systems face challenges in achieving accurate, reliable, and fast distance measurements, especially for objects at large distances, due to limited tuning ranges of DFB lasers and the need for movable components, which affect scanning speed and reliability.
Innovation Solution
A laser array comprising DFB, DBR, FDML, or VCSEL lasers with a dispersive scanning device, utilizing a frequency-selective deflection mechanism to enhance tuning range and coherence, combined with a two-dimensional dispersive scanning device for fast and accurate distance measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single DFB laser is used as the light source, then the coherence properties are good, but the tuning range is limited (comparatively tightly delimited)
Solution Approach 1:
The patent divides the light source into multiple DFB lasers, each operating at a different wavelength within the C-band (e.g., 1520 nm to 1565 nm). Each laser maintains good coherence properties independently, while the combination of multiple lasers provides an extended tuning range of approximately 4 THz, resolving the contradiction between coherence and tuning range.
2Productivity
If the tuning range of the light source is increased to enable fast scanning, then the measurement speed improves, but the measurement time increases due to the requirement for opposing time-dependent frequency profiles
Solution Approach 1:
The patent segments the frequency modulation process across multiple lasers. Each laser is modulated with a simpler frequency profile (without requiring opposing segments), but the collective output of multiple lasers with different center frequencies achieves the equivalent of a large tuning range scan, reducing the total measurement time.
Solution Approach 2:
The patent uses periodic frequency modulation of multiple lasers simultaneously. Each laser is modulated periodically at its own center frequency, and the combined signal provides the necessary frequency diversity for fast scanning without requiring complex opposing frequency profiles, thus reducing measurement time.
3Adaptability or versatility
If movable components such as scanning mirrors are used for scanning the object, then the scanning flexibility is good, but the reliability decreases and service life is reduced
Solution Approach 1:
The patent replaces the mechanical scanning mirror system with an optical approach using multiple DFB lasers with different wavelengths. The wavelength diversity of the lasers provides scanning capability without any moving parts, eliminating mechanical wear and improving reliability and service life while maintaining scanning flexibility.
4Reliability
If DFB lasers with limited tuning range are used, then the coherence properties are maintained, but the scanning process cannot be sufficiently fast for applications in road traffic
Solution Approach 1:
The patent segments the required frequency range into multiple smaller ranges, each covered by an individual DFB laser. By using multiple lasers with center frequencies spaced across the C-band (e.g., 1520 nm, 1530 nm, 1540 nm, 1550 nm, 1565 nm), the system achieves an aggregate tuning range of 4 THz while each individual laser maintains its coherence properties, enabling fast scanning speeds suitable for road traffic applications.
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 a large tuning range of up to 10 THz, allowing for fast and accurate distance measurement with reduced measurement time, even for objects several hundred meters away, while avoiding movable components.
Implementation Method 1
a measurement principle also referred to as LIDAR is known, amongst others, in which an optical signal whose frequency changes in time is emitted to the relevant object and evaluated after back-reflection has taken place at the object
Implementation Method 2
a dispersive scanning device which brings about a frequency-selective deflection of the measurement signals that are steered to the object
Data Source
AI summary
An apparatus and method for scanning ascertainment of a distance to an object are disclosed. Lasers of a light source emit a plurality of optical signals each having a time-varying frequency. At a given time, the frequencies of the optical signals are different. An evaluation device ascertains the distance to the object on the basis of measurement optical signals that were emitted by the light source and reflected or scattered at the object, and of reference optical signals that were emitted by the light source and were not reflected or scattered at the object. A dispersive scanning device simultaneously deflects the optical signals in different frequency-dependent directions.