Wavelength-Variable Laser for LIDAR Ambient Light Rejection
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Solution Overview
Problem
Optical systems for detecting scanning fields, such as LIDAR sensors, face challenges with reduced field-of-view due to narrow bandwidth band-pass filters, leading to increased ambient light interference, reduced dynamic range, and signal-to-noise ratio, especially when trying to cover the entire angular range of the scanning optical system.
Innovation Solution
The system varies the wavelength of electromagnetic radiation emitted by the source in response to beam path deflection, allowing for a narrower band-pass filter without reducing the scan-angle range, and uses a wavelength-variable laser or optical phased array to ensure the radiation remains within the filter's transmittance range, reducing ambient light interference and enhancing detection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a narrow bandwidth band-pass filter is used to block ambient light, then the filtering of unwanted light is improved, but the field-of-view of the receiver is reduced
Solution Approach 1:
The patent applies dynamics by making the filter characteristics adjustable rather than fixed. The band-pass filter's central wavelength and/or bandwidth can be dynamically adapted to match the transmitter's emission characteristics, allowing the system to optimize both ambient light rejection and field-of-view coverage across different scanning angles.
Solution Approach 2:
The patent implements parameter changes by varying the central wavelength and bandwidth of the band-pass filter according to the scanning angle. This allows the filter to maintain optimal performance across the entire field-of-view by adjusting its parameters to compensate for the angle-dependent transmittance characteristic shifts.
2Area of moving object
If a wide bandwidth band-pass filter is used to cover the entire scanning field, then the field-of-view is maintained, but ambient light interference increases
Solution Approach 1:
The system dynamically adjusts the filter bandwidth and central wavelength based on the current scanning angle and transmitter emission characteristics. This dynamic adaptation allows the use of narrower effective bandwidth filters while maintaining full field-of-view coverage, as the filter parameters are optimized for each specific viewing angle.
Solution Approach 2:
By changing the filter parameters (central wavelength and bandwidth) as functions of the scanning angle, the system achieves narrow bandwidth filtering at each angle without sacrificing overall field-of-view coverage. The parameter changes compensate for the angular shift in transmittance characteristics.
3Reliability
If the half width of the band-pass filter is reduced to improve signal-to-noise ratio, then ambient light rejection is improved, but the scan-angle range is reduced
Solution Approach 1:
The patent makes the filter half-width dynamically adjustable rather than fixed. By adapting the half-width to the current scanning angle and maintaining it as a function of angle, the system achieves high signal-to-noise ratio across the entire scan-angle range, rather than sacrificing angular coverage for improved filtering.
Solution Approach 2:
The system varies the half-width parameter of the band-pass filter according to the scanning angle, allowing narrow filtering (high signal-to-noise ratio) at each angle while maintaining comprehensive angular coverage through coordinated parameter changes.
4Device complexity
If a fixed central wavelength source is used, then the system is simpler, but manufacturing fluctuations reduce detection reliability
Solution Approach 1:
The patent implements feedback by using the known transmittance characteristic of the band-pass filter to determine and adjust the central wavelength of the electromagnetic radiation. This feedback mechanism compensates for manufacturing fluctuations in both the source and filter, ensuring reliable detection by maintaining wavelength alignment.
Solution Approach 2:
The system adjusts the central wavelength parameter of the radiation source as a function of the band-pass filter's characteristics, compensating for manufacturing variations. This parameter change ensures that the source wavelength always optimally matches the filter's peak transmittance.
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 allows for a marked reduction in band-pass filter half-width, maintaining the scan-angle range while reducing ambient light interference, improving signal quality, and increasing the reliability of object detection by ensuring the radiation remains within the filter's transmittance range, thus enhancing the dynamic range and signal-to-noise ratio.
Implementation Method 1
at least one optical filter element for filtering the electromagnetic radiation backscattered and/or reflected in the scanning field
Implementation Method 2
at least one deflection unit for deflecting the beam path of the electromagnetic radiation emitted by the source into the scanning field
Implementation Method 3
at least one source for emitting electromagnetic radiation, and the wavelength of the electromagnetic radiation emitted by the source is variable
Data Source
AI summary
An optical system for detecting a scanning field, a system for controlling the optical system as well as a method for controlling the optical system, the optical system having at least one transmitter comprising at least one source for emitting electromagnetic radiation and at least one deflection unit for deflecting the beam path of the electromagnetic radiation emitted by the source into the scanning field. The optical system furthermore has at least one optical receiver comprising at least one optical filter element for filtering the electromagnetic radiation scattered back and/or reflected in the scanning field and at least one detector element for detecting the filtered electromagnetic radiation. The essence of the invention lies in the fact that it is possible to vary the wavelength of the electromagnetic radiation emitted by the source and that the variation of the wavelength occurs as a function of the deflection of the beam path.