Solar filtering for atmospheric LiDAR
Patent Information
- Application Number
- JP2026023345
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-02-27
- Filing Date
- 2026-02-17
- Publication Date
- 2026-09-08
Smart Images
Figure 2026143352000001 
Figure 2026143352000002 
Figure 2026143352000003
Abstract
Description
[Technical Field]
[0001] Light Detection And Ranging (LiDAR) sensors use light to determine the distance to an object and / or atmospheric characteristics such as temperature, density, wind, humidity, aerosol measurements, and / or turbulence. [Summary of the Invention]
[0002] The airglow detection and ranging (LiDAR) system comprises: at least one laser source configured to transmit an emitted laser beam having a first polarization toward at least one measurement location; at least one detector configured to receive backscattered light having a second polarization, backscattered from at least one measurement location, and to determine the current intensity of the backscattered light; at least one polarization adjustment device configured to control the first polarization of the emitted laser beam, thereby controlling the second polarization of the backscattered light; at least one polarization filtering device configured to control the third polarization of the light received by at least one detector; and a processing circuit that identifies a first location of at least one detector, identifies a second location of the sun, and determines at least one location relative to the sun based on the first location of at least one detector and the second location of the sun. The system includes a processing circuit configured to determine a first orientation of an emitter, determine a fourth polarization of sunlight received from the sun based on the first orientation, determine a first desired configuration of at least one polarization adjustment device to cause the first polarization of the emitted laser light, and therefore the second polarization of the backscattered light and the fourth polarization of sunlight received from the sun, to be nearly perpendicular, and determine a second desired configuration of at least one polarization filtering device to cause the third polarization of at least one polarization filtering device to be nearly parallel to the second polarization of the backscattered light, and therefore the first polarization of the emitted laser light, and to control at least one polarization adjustment device to the first desired configuration and at least one polarization filtering device to the second desired configuration so as to maximize the transmission of backscattered light to at least one detector while minimizing the transmission of sunlight to at least one detector.
[0003] A method for performing airglow detection and ranging (LiDAR) sensing includes: transmitting an emitted laser beam having a first polarization from at least one laser source toward at least one measurement position; receiving a backscattered light having a second polarization, backscattered from at least one measurement position, using at least one detector; determining the current intensity of the backscattered light using at least one detector; controlling the first polarization of the emitted laser beam and thereby controlling the second polarization of the backscattered light using at least one polarization adjustment device; controlling the third polarization of the light received by at least one detector using at least one polarization filtering device; identifying a first location of at least one detector using a processing circuit; identifying a second location of the sun using a processing circuit; and determining a first orientation of at least one detector relative to the sun based on the first location of at least one detector and the second location of the sun using a processing circuit. The process includes: using a processing circuit to determine a fourth polarization of sunlight received from the sun based on a first orientation; using a processing circuit to determine a first desired configuration of at least one polarization adjustment device based on the fourth polarization of sunlight received from the sun so that the first polarization of the emitted laser light, and therefore the second polarization of the backscattered light and the fourth polarization of sunlight received from the sun are brought closer to perpendicular; using a processing circuit to determine a second desired configuration of at least one polarization filtering device based on the fourth polarization of sunlight received from the sun so that the third polarization of at least one polarization filtering device is brought closer to parallel with the second polarization of the backscattered light, and therefore the first polarization of the emitted laser light; and using a processing circuit to control at least one polarization adjustment device to the first desired configuration and at least one polarization filtering device to the second desired configuration so as to maximize the transmission of backscattered light to at least one detector while minimizing the transmission of sunlight to at least one detector.
[0004] The airglow detection and ranging (LiDAR) system comprises: at least one laser source configured to transmit an emitted laser beam having a first polarization toward at least one atmospheric region; at least one detector configured to receive backscattered light having a second polarization, which has been backscattered from at least one atmospheric region, and to determine the current intensity of the backscattered light; at least one polarization adjustment device configured to control the first polarization of the emitted laser beam, thereby controlling the second polarization of the backscattered light; at least one polarization filtering device configured to control the third polarization of the light received by at least one detector; and at least one antenna connected to a Global Navigation Satellite System (GSA).A GNSS receiver configured to receive GNSS signals from a GNSS satellite and determine its current position based on the GNSS signals from the GNSS satellite, and a processing circuit which, based on the current position determined by the GNSS receiver, identifies a first location of at least one detector, identifies a second location of the sun based on the current date and time, and information about the Earth's orbit around the sun and the Earth's rotation around its axis, determines a first orientation of at least one detector relative to the sun based on the first location of at least one detector and the second location of the sun, determines a fourth polarization of sunlight received from the sun based on the first orientation, and determines at least one polarization adjustment device based on the fourth polarization of sunlight received from the sun. The system comprises a processing circuit configured to determine a first desired configuration for causing the first polarization of the emitted laser light, and therefore the second polarization of the backscattered light and the fourth polarization of sunlight received from the sun to be nearly perpendicular, and a second desired configuration for causing the third polarization of at least one polarization filtering device to be nearly parallel to the second polarization of the backscattered light, and therefore the first polarization of the emitted laser light, and to control at least one polarization adjustment device to the first desired configuration and at least one polarization filtering device to the second desired configuration so as to minimize the transmission of sunlight to at least one detector while maximizing the transmission of backscattered light to at least one detector. [Brief explanation of the drawing]
[0005] With understanding that the drawings only illustrate exemplary embodiments and should not be considered limiting in scope, exemplary embodiments are described with further specificity and detail using the accompanying drawings. [Figure 1A] This is a block diagram illustrating an exemplary system with a LiDAR system. [Figure 1B] This is a block diagram illustrating an exemplary system with a LiDAR system. [Figure 1C]This is a block diagram illustrating an exemplary system with a LiDAR system. [Figure 2] This is an example of how to operate a LiDAR system.
[0006] Following convention, the various described features are not drawn to scale, but are drawn in a manner that highlights specific features relevant to the exemplary embodiment. [Modes for carrying out the invention]
[0007] The following detailed description will refer to the accompanying drawings, which form part of this specification, illustrating specific illustrative embodiments. However, it should be understood that other embodiments may be available and that logical, mechanical, and electrical modifications may be made. Furthermore, the methods presented in the drawings and specification should not be construed as limiting the order in which the individual steps may be performed. Accordingly, the following detailed description should not be construed as restrictive.
[0008] In the example, a light detection and ranging (LiDAR) sensor can be used to determine the distance to an object using light. In the example, a LiDAR sensor and system can generate a representation of the surrounding environment. In the example, a LiDAR system can generate a large amount of data, enabling a detailed representation of the environment based on measurements of distances to objects (including distances from the ground or distances from objects fixed to the ground). In the example, a LiDAR that uses measurement of distances to objects may be referred to as a hard-target LiDAR.
[0009] In an example, atmospheric LiDAR sensors and systems are used to determine atmospheric properties such as temperature, density, wind, humidity, aerosol measurements, and / or turbulence. In an example, LiDAR sensors and systems can be used to determine atmospheric properties by observing backscattered light from particles and molecules in the air. In an example, LiDAR sensors and systems can generate a representation of the surrounding environment from the ground to the thermosphere. In an example, LiDAR systems can generate large amounts of meteorological data and enable a detailed representation of the environment based on backscattered light measurements. In an example, LiDAR used to determine atmospheric properties may be referred to as atmospheric LiDAR and / or hard-target LiDAR.
[0010] For example, High-Altitude LiDAR Atmospheric Sensing (HALAS) technology faces challenges in performing measurements during daylight hours due to increased solar background. This limits range, signal-to-noise ratio, and algorithmic performance. Reducing this solar background enables simpler, more robust, and higher-performance data analysis and meteorological data. Reducing the solar background allows for higher-performance and simpler data analysis of HALAS technology. Humidity measurements are critical meteorological data for commercial weather forecasting. Humidity measurements, in particular, suffer from high solar background.
[0011] In this example, an airglow detection and ranging (LiDAR) system comprises a laser system that transmits laser light into the atmosphere, which interacts with molecules and aerosols in the air, causing backscatter of the light collected using the detector and / or telescope in the atmospheric LiDAR system. In this example, the performance of the atmospheric LiDAR system is limited by the solar background, which is based on the sun emitting light at the same (or similar) wavelength as the laser. In this example, the solar background limits the signal-to-noise ratio. In this example, it is desirable to reduce the solar background without reducing the signal to minimize signal loss as much as possible. In this example, the solar background is higher during the day. In this example, at night, the solar background is low (or nonexistent) because light from the sun is not received by the detector and / or telescope of the atmospheric LiDAR system and does not cause noise in the detection signal from the backscattered light.
[0012] In the example, the laser light transmitted by the laser system is ultraviolet (UV) light. In the example, solar background is still present in the UV region, even though the solar background is lower in the UV region. In the example, at low altitudes, solar background is not much of a problem, but at higher altitudes, solar background can result in dozens of solar background photons over a 20-minute measurement period, making it more likely that solar background photons from the sun will be collected by the detector and / or telescope, resulting in noise accompanied by signals from backscattered light. In the example, less air at higher altitudes results in reduced backscatter from molecules and a decrease in signal intensity.
[0013] In the example, a narrowband filter can be used to reduce solar background noise. In the example, the light from the laser has a narrow wavelength (e.g., several hundred nanometers), but the solar background is fairly broad and continuous. In the example, the laser is a pulsed laser, but it could also be a continuous-wave laser. In the example, a narrowband filter centered on the laser wavelength is used before the light is received by the detector and / or telescope to reduce noise. In the example, the use of a narrowband filter is lossy because it reduces the signal. In the example where a narrowband filter is used, up to 50% (or more) of the signal may be lost by passing through the narrowband filter. In the example, performance can be improved by eliminating or reducing the use of a narrowband filter.
[0014] In the example, the outgoing laser is polarized in a typical s-orientation or p-orientation (vertical or horizontal) depending on the laser mounting orientation and laser beam path. In the example, molecular scattering (signal) from the atmosphere is oriented parallel to this outgoing polarization when it returns to the telescope. In the example, the solar background can be either parallel or perpendicular to this outgoing polarization. In the example, the laser light is polarized. In the example, backscattered light may be polarized depending on what reflects it. In the example, sunlight returning from the sun is also polarized. In the example, if the polarizer is aligned perpendicular to the polarization direction of the light from the sun, the solar background can be attenuated to the same extent as it would be generated using a narrowband filter, without attenuating the signal from the backscattered light. In the example, reducing the solar background can potentially increase the signal-to-noise ratio (SNR) as long as the signal intensity is not attenuated by the same amount as the solar background. In the example, the solar background is sufficiently reduced without excessively reducing the signal from the backscattered light, and no narrowband filter is required. In the example, a narrowband filter can still be used to further reduce the solar background, but without an aligned polarizer, with a lower level of attenuation required. In the example, a widerband filter, which has less loss but is not as good at filtering out the solar background, can be used with an aligned polarizer. In the example, the filter itself typically allows light of a certain wavelength to pass through, regardless of polarization.
[0015] In the example, by placing a polarizer (input polarizer) at the fold of the telescope, it becomes possible to reject some of the sunlight while preserving all or most of the signal. In the example, the polarization of sunlight is oriented tangent to a circle with the sun as the origin, due to the principle of molecular Rayleigh scattering. In the example, depending on the orientation of the output laser relative to the location of the sun in the sky, there exists an optimal orientation of the input polarizer to minimize the sunlight background. In the example, this orientation is parallel to a line intersecting the sun. In the example, this input polarizer must still be oriented parallel to the output laser polarization to maximize the signal. In the example, both the laser polarization and the input polarization have an optimal orientation parallel to a line crossing the sun. In the example, this can be done in various ways. In the example, using additional degrees of freedom of the telescope and laser transmitter, the system can be physically rotated so that the natural s-orientation or p-orientation of the laser matches the optimal orientation. In the example, a half-wave plate is used in combination with a rotatable input polarizer to rotate the output laser polarization. In the example, a simpler method for switching between s- and p-orientation of the laser and input polarizer allows for a certain degree of basic control. In the example, with the laser polarization well understood, the input polarizer can be placed in a fixed position, and the system orientation can be selected to minimize the solar background.
[0016] In the example, it is desirable to have the laser and polarizer entering the telescope have the same polarization, and to make both the laser polarization and the polarizer polarization as perpendicular as possible to the polarization of sunlight. In the example, the laser polarization and the polarization of the return from backscattered light are adjusted so that they align. In the example, the laser light is polarized substantially horizontally, but the solar polarization of the sun is polarized substantially vertically, and the return light is also polarized substantially horizontally, and a substantially horizontally polarized polarizer can be used to filter out the substantially vertically polarized light from the sun and allow the substantially horizontally polarized return light to pass through. In the example, the polarization of the outgoing laser beam is changed to be as perpendicular as possible to the polarization of the light from the sun. In the example, at the receiving end, the outgoing and incident light have substantially similar polarization angles. In the example, when the laser polarization is adjusted, the polarizer for the received backscattered light is adjusted accordingly. In the example, determining how the polarization of the laser and polarizer for the detector and / or telescope should be adjusted is based on data regarding the location and orientation of the laser and detector and / or telescope, and the location of the sun in the sky.
[0017] In the example, the polarization of sunlight from the Sun is determined by and differs depending on where the laser and detector are pointed relative to the Sun. In the example, equations and / or formulas are used to calculate the polarization of light from the Sun based on the angle at which the laser and detector are pointed relative to the Sun's location in the sky. In the example, calculations can be made to determine what polarization is expected from the Sun. In the example, these calculations take into account the Earth's location relative to the Sun (based on the known orbits of celestial bodies at a given time), the Earth's rotation, and / or the location and orientation of the laser, detector, and / or telescope. In the example, these calculations also take into account atmospheric information relating to density and scattering physical properties. In the example, the calculations are based on analytical and / or computational models. In the example, inputs to the equations and / or formulas may include the location and pointing direction of the laser, detector, and / or telescope relative to the Sun. In the example, the system can determine its location and the direction in which the laser, detector, and / or telescope are pointed relative to the Sun with great accuracy. In the example of a stationary system, the locations of the laser, detector, and / or telescope may be fixed and known. In this example, the system knows the direction and / or angle to which the laser, detector, and / or telescope are pointed. In the example of a moving system (such as a system on an aircraft, satellite, or other moving vehicle), the system's position can be precisely determined using a Global Navigation Satellite System (GNSS) receiver.
[0018] In the example, the polarization of the light transmitted from the laser and the polarization of the light incident on the detector and / or telescope are adjusted to match each other and to be perpendicular to the solar polarization. In the example, the system is then aligned to have a polarization perpendicular to the polarization expected from the sun. In the example, the polarization of the light from the sun is calculated periodically, and the system is readjusted periodically. In the example, the polarization is generally constant with respect to a particular position, and the polarization is calculated and aligned once without subsequent readjustments. In the example, the laser and the detector and / or telescope are mounted together and rotated together. In other examples, the laser and the detector and / or telescope are mounted separately and rotated separately. In the example, the backscattered light returns in the same direction from which the laser light was transmitted.
[0019] Figures 1A–1C are block diagrams illustrating exemplary systems 100A–100C. In the examples, systems 100A–100C may be implemented in a stationary ground location, mounted on or coupled to a vehicle, or held by a person. The use of the term “vehicle” is not intended to be limiting and includes all classes of vehicles that fall within the ordinary meaning of the term. This includes, but is not limited to, airborne vehicles (e.g., civilian aircraft, non-civilian aircraft, or recreational aircraft), unmanned and / or space-based vehicles (e.g., satellites, urban air-based vehicles), waterborne vehicles (e.g., ships, submarines), and ground-based vehicles (e.g., automobiles, including passenger cars, trucks, and motorcycles). Throughout this disclosure, a vehicle may be described as an aircraft, with the understanding that the principles described herein apply to other vehicles where applicable.
[0020] Figure 1A is a block diagram of a system 100A having a LiDAR (Light Detection and Ranging) system 102A having components (optionally referred to as transmitter 104 and receiver 106) including at least one laser source 108, at least one detector 110, at least one polarization adjustment device 112, at least one polarization filtering device 114, and at least one processing circuit 116. In the example, at least one laser source 108 is configured to transmit emitted laser light 118 (or other light) toward at least one measurement location 120A (such as an atmospheric region, particle, object, ground, surface). In the example, at least one laser light has a first polarization. In the example, at least one laser source 108 can be any type of light source generator, including any type of laser. In the example, at least one laser source 108 is communicably coupled to at least one optional optical component 122 that focuses, amplifies, or otherwise adjusts the emitted laser light 118 (or other light) emitted from at least one laser source 108.
[0021] In the example, at least a portion of the emitted laser light 118 is backscattered as backscattered light 124 from at least one measurement position 120A. In the example, the measurement position includes at least one atmospheric region, and the backscattered light is backscattered from at least one atmospheric region and used to measure atmospheric properties (such as temperature, density, wind, humidity, aerosol measurements, and turbulence). In the example, at least one measurement position 120A includes at least one atmospheric region and / or at least one particle, and the light is backscattered from at least one atmospheric region and / or at least one particle. In the example, at least one measurement position 120A includes at least one object and / or at least one surface (such as the ground), and the backscattered light is reflected from at least one object and / or at least one surface and can be used to measure the distance to at least one object and / or at least one surface.
[0022] In the example, backscattered light 124 is received by at least one detector 110 via at least one polarization filtering device 114 and at least one optional optical component 126. In the example, light from the sun 128 is also received by at least one detector 110 via at least one polarization filtering device 114 and at least one optional optical component 126. In the example, at least one optional optical component 126 includes a telescope that magnifies the backscattered light 124. In the example, at least one optional optical component 126 includes other optical components that focus, magnify, or otherwise adjust the backscattered light 124. In the example, at least one optional optical component 126 includes optical fibers, interferometers, optical instruments, scientific instruments, or other optical components. In the example, at least one optional optical component 126 comprises at least one telescope positioned between at least one polarization filtering device and at least one detector. In the example, at least one telescope is configured to receive backscattered light from at least one measurement position, amplify the backscattered light, and provide the backscattered light to at least one detector.
[0023] In the example, at least one polarization adjustment device 112 is configured to control a first polarization of the emitted laser light, thereby controlling a second polarization of the backscattered light. In the example, at least one polarization adjustment device 112 is rotatable around an axis, and at least one laser source 108 and / or at least one detector 110 are mounted on the at least one polarization adjustment device 112 and are rotatable around an axis. In the example, at least one polarization adjustment device 112 comprises a half-wave plate, another wave plate, or another optical device. In the example, a first desired configuration of the at least one polarization adjustment device is determined to bring the first polarization of the emitted laser light, and therefore the second polarization of the backscattered light and the fourth polarization of sunlight received from the sun, closer to perpendicular. In the example, at least one polarization adjustment device 112 is configured to control the first polarization of the emitted laser light by rotating at least one laser source 108 around an axis. In the example, at least one polarization adjustment device 112 is configured to rotate at least one laser source 108 and at least one detector 110 around the same axis, so that the first polarization of at least one laser source 108 matches the second polarization of at least one detector 110. In the example, at least one laser source 108 and at least one detector 110 (and any at least one optional optical component 122) and at least one detector 110 (and any at least one optional optical component 126 and / or at least one polarization filtering device 114) are now mounted to each other such that at least one laser source 108 and at least one detector 110 rotate together and remain in a polarized state. In the example, at least one polarization adjustment device 112 includes a first device (such as a waveplate) for adjusting the polarization of laser light emitted from at least one laser source 108, and a second device for adjusting the polarization of incident light received by at least one detector 110, wherein the first and second devices are adjusted simultaneously. In the example, at least one polarization adjustment device 112 is adjusted electronically and / or mechanically.
[0024] In an example, the at least one polarization adjustment device 112 is rotatable. In an example, the at least one laser source 108 is mechanically coupled to the at least one polarization adjustment device 112. In an example, the at least one polarization adjustment device 112 is controlled to a first desired configuration by mechanically rotating the at least one polarization adjustment device 112 to rotate the at least one laser source 108, so that the first polarization of the emitted laser light, and thus the second polarization of backscattered light and the fourth polarization of sunlight received from the sun 128, are brought close to perpendicular to each other.
[0025] In an example, the at least one polarization filtering device 114 is configured to control the polarization of light received by at least one detector. In an example, the at least one polarization filtering device 114 comprises a rotatable polarization filter that is rotated electronically and / or mechanically. In an example, the at least one polarization filtering device 114 is configured to control light received by the at least one detector 110 such that a third polarization of the at least one polarization filtering device is brought close to parallel with the second polarization of backscattered light and the first polarization of emitted laser light. In an example, as the second polarization of backscattered light and the fourth polarization of sunlight received from the sun approach perpendicular to each other, the intensity of sunlight background noise from the sunlight received from the sun is greatly reduced by the at least one polarization filtering device 114, while the intensity of backscattered light backscattered from the at least one measurement position 120A and / or the at least one atmospheric region 120B does not decrease, or decreases to a much lesser extent. In an example, this occurs because the third polarization of the at least one polarization filtering device is substantially perpendicular to the fourth polarization of sunlight, while the third polarization of the at least one polarization filtering device is substantially parallel to the second polarization of backscattered light.
[0026] In an example, the at least one polarization filtering device 114 comprises a polarizing filter. In an example, the at least one polarization filtering device 114 is controlled to a second desired configuration by mechanically rotating the at least one polarization filtering device 114 to bring a third polarization of the at least one polarization filtering device closer to being parallel with a second polarization of backscattered light and thus a first polarization of the output laser beam.
[0027] In an example, a half-wave plate is used as the at least one polarization adjustment device 112 to rotate the polarization of the output laser light of the at least one laser source 108, in combination with a rotatable input polarizer used as the at least one polarization filtering device 114 positioned before the at least one detector 110 and / or the at least one polarization filtering device 114 and the at least one polarization filtering device 114 and at least one optional optical component (such as a telescope) 126. In an example, the at least one laser source 108 and / or the at least one detector 110 and / or the at least one optional optical component (such as a telescope) 126 are not physically rotated; rather, the polarization of the light is rotated in another manner (for example, using a half-wave plate in combination with a rotatable input polarizer positioned to rotate the received light before the at least one detector 110 to rotate the output polarization of the laser light).
[0028] In an example, the at least one polarization adjustment device 112 switches between two or more different static polarization options, such as switching between a 90-degree polarization option and a 0-degree polarization option. In an example, the at least one polarization adjustment device 112 can be switched between two or more static polarization options to attempt to make the second polarization of the backscattered light and a fourth polarization of sunlight received from the sun as close to perpendicular as possible by having a maximum angular difference between 0 degrees and 90 degrees. In these examples, this can improve the signal even when it does not result in an angular difference very close to 90 degrees.
[0029] In an example where the polarization relative to the sun is assumed to be at a relatively constant angle, a desired orientation can be determined that minimizes the average solar background at all pointing angles. In the example, the transmitted laser beam can always be aligned with the polarizer, and then the transmitted laser beam is aligned perpendicular to the sun on average. In the example, this is not very effective, but it can be a simple, robust, and cost-effective approach if a particular LiDAR system 102A is typically pointed at a particular part of the sky and provides acceptable performance in scenarios such as when the sun is usually in that part of the sky at a particular time of year.
[0030] In the example, the LiDAR system 102A is positioned on the ground as a ground system, but it can also be positioned on an aircraft or satellite. In the example, the ground-positioned LiDAR system 102A is stationary, but it can be portable and positioned on a vehicle or the like. In the example where the LiDAR system 102A is a stationary ground system, the calculations using the equations are based on our knowledge of the position of the sun 128 above the ground system. In the example where the LiDAR system 102A is in a moving vehicle, the location and movement of the vehicle can be taken into consideration in the calculations and in determining how often the calculations and readjustments should be performed.
[0031] In the example, the LiDAR system 102A may include additional photodetectors, optical sensors, cameras, or other sensors to actively determine the location of the sun 128 in the sky. In the example, a photodetector having a polarizer is pointed towards the sky, and the polarization of the polarizer is rotated to determine which angle has the most polarized light. In the example, a camera having a polarizer is pointed towards the sky, and the polarization of the polarizer is rotated to determine which angle has the most polarized light.
[0032] In the example, LiDAR system 100A includes an optional GNSS receiver 130 configured to (1) receive GNSS signals from a Global Navigation Satellite System (GNSS) satellite by at least one antenna, and (2) determine its current position based on the GNSS signals from the GNSS satellite, and a processing circuit 116 configured to identify a first location of at least one detector based on the current position determined by the GNSS receiver. In the example, the processing circuit 116 is configured to identify a second location of the sun based on the current date and time, as well as information about the Earth's orbit around the sun and the Earth's rotation around its axis. In the example, LiDAR system 102A includes an optional power supply 132 that provides power to various components of LiDAR system 102A.
[0033] Figure 1B is a block diagram of system 100B having an atmospheric light detection and ranging (LiDAR) system 102B having components similar to those of the LiDAR system 102A described with reference to Figure 1A and system 100A. The atmospheric LiDAR system 102B is a specific implementation of LiDAR system 102A that is used specifically to measure atmospheric properties (such as temperature, density, wind, humidity, aerosol measurements, and turbulence) of an atmospheric region 120B (which is a specific implementation of at least one measurement location 120A). In the example, the atmospheric LiDAR system 102B measures atmospheric properties of at least one atmospheric region 120B by emitting at least one laser into the air, where some amount of light interacts with particles and molecules in the air and is backscattered toward the atmospheric LiDAR system 102B, where it is collected and analyzed to determine atmospheric properties such as temperature, density, wind, humidity, aerosol measurements, and turbulence. In the example, the atmospheric LiDAR system 102B is directed to measure at a given location within at least one atmospheric region 120B, and the range of the atmospheric LiDAR system 102B is decomposed to measure simultaneously at multiple altitudes of interest (such as all altitudes). In the example, the atmospheric LiDAR system 102B is mounted on or integrated into an aircraft or other vehicle to measure altitude or other characteristics.
[0034] Figure 1C is a block diagram of system 100B having an airglow detection and ranging (LiDAR) system 102B having components similar to those of LiDAR system 102A described with reference to Figure 1A and system 100A, and LiDAR system 102B described with reference to Figure 1B and system 100C. Figure 1C shows an atmospheric LiDAR system 102B having at least one polarization adjustment device 112 used to direct at least one atmospheric region 120B.
[0035] Figure 2 shows an exemplary method 200 for operating a light detection and ranging (LiDAR) sensor (such as an atmospheric LiDAR system 102). In the example, method 200 begins in block 202, transmitting an outgoing laser beam having a first polarization from at least one laser source toward at least one measurement location. In the example, method 200 proceeds to block 204, receiving a backscattered light having a second polarization, backscattered from at least one measurement location, using at least one detector. In an example, method 200 further includes (1) receiving backscattered light from at least one measurement position using at least one telescope positioned between at least one polarization filtering device and at least one detector; (2) amplifying the backscattered light from at least one measurement position using at least one telescope positioned between at least one polarization filtering device and at least one detector; and (3) providing the backscattered light to at least one detector using at least one telescope positioned between at least one polarization filtering device and at least one detector.
[0036] In the example, method 200 proceeds to block 206, where at least one detector is used to determine the current intensity of the backscattered light. In the example, method 200 proceeds to block 208, where at least one polarization adjustment device is used to control the first polarization of the emitted laser light, thereby controlling the second polarization of the backscattered light. In the example, method 200 proceeds to block 210, where at least one polarization filtering device is used to control the third polarization of the light received by at least one detector.
[0037] In the example, method 200 proceeds to block 212, using a processing circuit to determine a first location of at least one detector. In the example, method 200 further includes (1) using a Global Navigation Satellite System (GNSS) receiver to receive GNSS signals from a GNSS satellite by at least one antenna; (2) using the GNSS receiver to determine the current position based on the GNSS signals; and (3) using a processing circuit to determine a first location of at least one detector based on the current position determined by the GNSS receiver.
[0038] In the example, method 200 proceeds to block 214, using a processing circuit to determine the second location of the sun. In the example, this includes using a processing circuit to determine the second location of the sun based on the current date and time, as well as information about the Earth's orbit around the sun and the Earth's rotation around its axis.
[0039] In the example, method 200 proceeds to block 216, where a processing circuit is used to determine a second orientation of at least one detector relative to the sun, based on a first location of at least one detector and a second location of the sun. In the example, method 200 proceeds to block 218, where a processing circuit is used to determine a fourth polarization of sunlight received from the sun, based on the first orientation.
[0040] In the example, method 200 proceeds to block 220, using a processing circuit to determine a first desired configuration such that at least one polarization adjustment device causes the first polarization of the emitted laser light, and therefore the second polarization of the backscattered light and the fourth polarization of the sunlight received from the sun to be brought closer to perpendicular, based on the fourth polarization of the sunlight received from the sun. In the example, method 200 proceeds to block 222, using a processing circuit to determine a second desired configuration such that at least one polarization filtering device causes the third polarization of at least one polarization filtering device to be brought closer to parallel with the second polarization of the backscattered light and therefore the first polarization of the emitted laser light, based on the fourth polarization of the sunlight received from the sun.
[0041] In the example, method 200 proceeds to block 224, using a processing circuit to control at least one polarization adjustment device to a first desired configuration and at least one polarization filtering device to a second desired configuration, such that transmission of backscattered light to at least one detector is maximized while transmission of sunlight to at least one detector is minimized. In the example, controlling at least one polarization adjustment device to a first desired configuration is done by mechanically rotating at least one polarization adjustment device to rotate at least one laser source, causing the first polarization of the emitted laser light, and therefore the second polarization of the backscattered light and the fourth polarization of sunlight received from the sun to be closer to perpendicular. In the example, controlling at least one polarization filtering device to a second desired configuration is done by mechanically rotating at least one polarization filtering device to cause the third polarization of at least one polarization filtering device to be closer to parallel with the second polarization of the backscattered light and therefore the first polarization of the emitted laser light.
[0042] In the example, the measurement location includes at least one atmospheric region, and the backscattered light is backscattered from at least one atmospheric region and used to measure atmospheric properties (such as temperature, density, wind, humidity, aerosol measurements, and turbulence).
[0043] The methods and techniques described herein may be implemented in digital electronic circuits or using programmable processors (e.g., dedicated processors or general-purpose processors such as computers), firmware, software, or various combinations thereof. Apparatus for implementing these techniques may include appropriate input and output devices, a programmable processor, and a storage medium that tangibly embodies program instructions for execution by the programmable processor. The process for implementing these techniques may be carried out by a programmable processor that executes a program of instructions to perform a desired function by acting on input data and generating appropriate outputs. These techniques may be advantageously implemented in one or more programs executable on a programmable system including a data storage system, at least one input device, and at least one output device, each coupled with at least one programmable processor to receive and transmit data and instructions to them. Generally, the processor receives instructions and data from read-only memory and / or random-access memory. Suitable storage devices for tangibly embodying computer program instructions and data include, for example, all forms of non-volatile memory and storage media, such as random access memory, memory storage devices, optical memory devices, magnetic media, floppy disks, magnetic tapes, hard drives, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), optical media (such as compact discs, DVDs, and Blu-ray discs), and magneto-optical disks.Any of the above may be complemented by or incorporated into any known processor, such as a general-purpose processor (GPP), a dedicated processor (field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or other integrated circuit or circuit), or any programmable logic device.
[0044] While a detailed description of one or more embodiments of the Disclosure is given above, various substitutes, modifications, and equivalents will be apparent to those skilled in the art without departing from the spirit of the Disclosure. For example, while the embodiments described above refer to specific features, the scope of the Invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the Disclosure is intended to encompass all such substitutes, modifications, and variations that fall within the scope of the Claims, along with all their equivalents. Therefore, the above description should not be construed as restrictive. [Examples]
[0045] Example 1 includes an atmospheric light detection and ranging (LiDAR) system, the atmospheric LiDAR system comprising: at least one laser source configured to transmit an emitted laser beam having a first polarization toward at least one measurement position; at least one detector configured to receive backscattered light having a second polarization, backscattered from at least one measurement position, and to determine the current intensity of the backscattered light; at least one polarization adjustment device configured to control the first polarization of the emitted laser beam, thereby controlling the second polarization of the backscattered light; at least one polarization filtering device configured to control the third polarization of the light received by at least one detector; and a processing circuit that identifies a first location of at least one detector, identifies a second location of the sun, and, based on the first location of at least one detector and the second location of the sun, determines the direction of the sun. The system comprises a processing circuit configured to determine a first orientation of at least one detector, determine a fourth polarization of sunlight received from the sun based on the first orientation, determine a first desired configuration of at least one polarization adjustment device to cause the first polarization of the emitted laser light, and therefore the second polarization of the backscattered light and the fourth polarization of sunlight received from the sun, to be nearly perpendicular, and determine a second desired configuration of at least one polarization filtering device to cause the third polarization of at least one polarization filtering device to be nearly parallel to the second polarization of the backscattered light, and therefore the first polarization of the emitted laser light, and to control at least one polarization adjustment device to the first desired configuration and at least one polarization filtering device to the second desired configuration so as to maximize the transmission of backscattered light to at least one detector while minimizing the transmission of sunlight to at least one detector.
[0046] Example 2 includes the atmospheric LiDAR system of Example 1, wherein at least one polarization adjustment device is rotatable, at least one laser source is mechanically coupled to the at least one polarization adjustment device, and the at least one polarization adjustment device is controlled to a first desired configuration by mechanically rotating the at least one polarization adjustment device to rotate the at least one laser source, thereby bringing the first polarization of the emitted laser light, and thus the second polarization of the backscattered light and the fourth polarization of sunlight received from the sun, closer to perpendicular.
[0047] Example 3 comprises an atmospheric LiDAR system according to any of Examples 1 to 2, further comprising: at least one polarization filtering device comprising a polarization filter, and at least one polarization filtering device being controlled to a second desired configuration by mechanically rotating the at least one polarization filtering device to bring the third polarization of the at least one polarization filtering device closer to parallel with the second polarization of the backscattered light, and thus the first polarization of the emitted laser light.
[0048] Example 4 includes an atmospheric LiDAR system from any of Examples 1 to 3, wherein at least one measurement location includes at least one atmospheric region, and the backscattered light is backscattered from at least one atmospheric region.
[0049] Embodiment 5 includes an atmospheric LiDAR system according to any of Embodiments 1 to 4, further comprising a GNSS receiver configured to receive GNSS signals from a Global Navigation Satellite System (GNSS) satellite via at least one antenna and to determine its current position based on the GNSS signals from the GNSS satellite, and a processing circuit configured to identify a first location of at least one detector based on the current position determined by the GNSS receiver.
[0050] Example 6 includes an atmospheric LiDAR system according to any of Examples 1 to 5, further comprising a processing circuit configured to determine a second location of the sun based on the current date and time, as well as information about the Earth's orbit around the sun and the Earth's rotation around its axis.
[0051] Embodiment 7 includes an atmospheric LiDAR system according to any of Embodiments 1 to 6, further comprising a GNSS receiver configured to receive GNSS signals from a Global Navigation Satellite System (GNSS) satellite via at least one antenna and to determine its current position based on the GNSS signals from the GNSS satellite, and a processing circuit configured to identify a first location of at least one detector based on the current position determined by the GNSS receiver and to identify a second location of the sun based on the current date and time, as well as information about the Earth's orbit around the sun and the Earth's rotation around its axis.
[0052] Example 8 comprises an atmospheric LiDAR system of any of Examples 1 to 7, further comprising at least one telescope positioned between at least one polarization filtering device and at least one detector, wherein the at least one telescope is configured to receive backscattered light from at least one measurement position, amplify the backscattered light, and provide the backscattered light to at least one detector.
[0053] Example 9 includes an atmospheric LiDAR system of any of Examples 1 to 8, the atmospheric LiDAR system further comprising at least a first optical component positioned between at least one laser source and at least one measurement position, and at least a second optical component positioned between at least one polarization filtering device and at least one detector.
[0054] Example 10 includes a method for performing airglow detection and ranging (LiDAR) sensing, the method comprising: transmitting an emitted laser beam having a first polarization from at least one laser source toward at least one measurement position; receiving a backscattered light having a second polarization, backscattered from at least one measurement position, using at least one detector; determining the current intensity of the backscattered light using at least one detector; controlling the first polarization of the emitted laser beam and thereby controlling the second polarization of the backscattered light using at least one polarization adjustment device; controlling the third polarization of the light received by at least one detector using at least one polarization filtering device; identifying a first location of at least one detector using a processing circuit; identifying a second location of the sun using a processing circuit; and determining a first orientation of at least one detector relative to the sun based on the first location of at least one detector and the second location of the sun using a processing circuit. The process includes: using a processing circuit to determine a fourth polarization of sunlight received from the sun based on a first orientation; using a processing circuit to determine a first desired configuration of at least one polarization adjustment device based on the fourth polarization of sunlight received from the sun so that the first polarization of the emitted laser light, and therefore the second polarization of the backscattered light and the fourth polarization of sunlight received from the sun are brought closer to perpendicular; using a processing circuit to determine a second desired configuration of at least one polarization filtering device based on the fourth polarization of sunlight received from the sun so that the third polarization of at least one polarization filtering device is brought closer to parallel with the second polarization of the backscattered light, and therefore the first polarization of the emitted laser light; and using a processing circuit to control at least one polarization adjustment device to the first desired configuration and at least one polarization filtering device to the second desired configuration so as to maximize the transmission of backscattered light to at least one detector while minimizing the transmission of sunlight to at least one detector.
[0055] Example 11 includes the method of Example 10, further comprising controlling at least one polarization adjustment device to a first desired configuration by mechanically rotating at least one polarization adjustment device to rotate at least one laser source and bringing the first polarization of the emitted laser light, and thus the second polarization of the backscattered light and the fourth polarization of sunlight received from the sun, closer to perpendicular.
[0056] Example 12 comprises any method of Examples 10 to 11, the method further comprising controlling at least one polarization filtering device to a second desired configuration by mechanically rotating at least one polarization filtering device to bring the third polarization of at least one polarization filtering device closer to parallel with the second polarization of the backscattered light, and thus the first polarization of the emitted laser light.
[0057] Example 13 comprises any method of Examples 10 to 12, wherein at least one measurement location includes at least one atmospheric region, and the backscattered light is backscattered from at least one atmospheric region.
[0058] Example 14 includes any method of Examples 10 to 13, the method further including: using a Global Navigation Satellite System (GNSS) receiver to receive GNSS signals from a GNSS satellite by at least one antenna; using the GNSS receiver to determine the current position based on the GNSS signals; and using a processing circuit to identify a first location of at least one detector based on the current position determined by the GNSS receiver.
[0059] Example 15 comprises any of the methods of Examples 10 to 14, the method further comprising using a processing circuit to determine a second location of the sun based on the current date and time, as well as information about the Earth's orbit around the sun and the Earth's rotation around its axis.
[0060] Example 16 includes any method of Examples 10 to 15, the method further including: using a Global Navigation Satellite System (GNSS) receiver to receive GNSS signals from a GNSS satellite by at least one antenna; using the GNSS receiver to determine the current position based on the GNSS signals; using a processing circuit to identify a first location of at least one detector based on the current position determined by the GNSS receiver; and using a processing circuit to identify a second location of the sun based on the current date and time, as well as information about the Earth's orbit around the sun and the Earth's rotation around its axis.
[0061] Example 17 includes any method of Examples 10 to 16, the method further including receiving backscattered light from at least one measurement position using at least one telescope positioned between at least one polarization filtering device and at least one detector, amplifying the backscattered light from at least one measurement position using at least one telescope positioned between at least one polarization filtering device and at least one detector, and providing the backscattered light to at least one detector using at least one telescope positioned between at least one polarization filtering device and at least one detector.
[0062] Example 18 includes an atmospheric light detection and ranging (LiDAR) system, the atmospheric LiDAR system comprising: at least one laser source configured to transmit an emitted laser beam having a first polarization toward at least one atmospheric region; at least one detector configured to receive backscattered light having a second polarization, backscattered from at least one atmospheric region, and to determine the current intensity of the backscattered light; at least one polarization adjustment device configured to control the first polarization of the emitted laser beam, thereby controlling the second polarization of the backscattered light; at least one polarization filtering device configured to control the third polarization of the light received by at least one detector; a GNSS receiver configured to receive GNSS signals from a Global Navigation Satellite System (GNSS) satellite by at least one antenna and to determine the current position based on the GNSS signals from the GNSS satellite; and a processing circuit configured to process at least one current position determined by the GNSS receiver. Identify a first location of at least one detector, identify a second location of the sun based on the current date and time, and information regarding the Earth's orbit around the sun and the Earth's rotation around its axis, determine a first orientation of at least one detector relative to the sun based on the first location of at least one detector and the second location of the sun, determine a fourth polarization of sunlight received from the sun based on the first orientation, determine a first desired configuration of at least one polarization adjustment device to cause the first polarization of the emitted laser light, and therefore the second polarization of the backscattered light and the fourth polarization of sunlight received from the sun to be nearly perpendicular, and determine a second desired configuration of at least one polarization filtering device to cause the third polarization of at least one polarization filtering device to be nearly parallel to the second polarization of the backscattered light, and therefore the first polarization of the emitted laser light, and configure at least one polarization adjustment device to the first desired configuration to maximize the transmission of backscattered light to at least one detector while minimizing the transmission of sunlight to at least one detector.and a processing circuit configured to control at least one polarization filtering device to a second desired configuration.
[0063] Example 19 includes the atmospheric LiDAR system of Example 18, wherein at least one polarization adjustment device is rotatable, at least one laser source is mechanically coupled to the at least one polarization adjustment device, and the at least one polarization adjustment device is controlled to a first desired configuration by mechanically rotating the at least one polarization adjustment device to rotate the at least one laser source, thereby bringing the first polarization of the emitted laser light, and thus the second polarization of the backscattered light and the fourth polarization of sunlight received from the sun, closer to perpendicular.
[0064] Example 20 includes an atmospheric LiDAR system of any of Examples 18-19, further comprising at least one polarization filtering device comprising a polarization filter, and the at least one polarization filtering device being controlled to a second desired configuration by mechanically rotating the at least one polarization filtering device to bring the third polarization of the at least one polarization filtering device closer to parallel with the second polarization of the backscattered light, and thus the first polarization of the emitted laser light.
Claims
1. An airglow detection and ranging (LiDAR) system, wherein the airglow LiDAR system is At least one laser source configured to transmit an emitted laser beam having a first polarization toward at least one measurement position, At least one detector, The system receives backscattered light having a second polarization, which is backscattered light from at least one of the measurement positions, and At least one detector configured to determine the current intensity of the backscattered light, At least one polarization adjustment device configured to control the first polarization of the emitted laser light and thereby control the second polarization of the backscattered light, At least one polarization filtering device configured to control the third polarization of light received by the at least one detector, A processing circuit, Identify the first location of the at least one detector, Identify the Sun's second location, Based on the first location of the at least one detector and the second location of the sun, the first orientation of the at least one detector with respect to the sun is determined. Based on the first orientation described above, the fourth polarization of sunlight received from the sun is determined, Based on the fourth polarization of the sunlight received from the sun, A first desired configuration in which the at least one polarization adjustment device causes the first polarization of the emitted laser light, and therefore the second polarization of the backscattered light and the fourth polarization of the sunlight received from the sun, to be brought closer to perpendicular, and The at least one polarization filtering device determines a second desired configuration such that the third polarization of the at least one polarization filtering device is brought closer to parallel with the second polarization of the backscattered light, and therefore with the first polarization of the emitted laser light, and An atmospheric LiDAR system comprising: a processing circuit configured to control the at least one polarization adjustment device to a first desired configuration and the at least one polarization filtering device to a second desired configuration, such that the transmission of sunlight to the at least one detector is minimized while the transmission of backscattered light to the at least one detector is maximized.
2. The at least one polarization adjustment device is rotatable, The at least one laser source is mechanically coupled to the at least one polarization adjustment device, and The atmospheric LiDAR system according to claim 1, further comprising the following: the at least one polarization adjusting device is mechanically rotated to rotate the at least one laser source, thereby controlling the at least one polarization adjusting device to a first desired configuration by bringing the first polarization of the emitted laser light, and therefore the second polarization of the backscattered light and the fourth polarization of the sunlight received from the sun, closer to perpendicular.
3. The at least one polarization filtering device comprises a polarization filter, and The atmospheric LiDAR system according to claim 1, further comprising the following: the at least one polarization filtering device is mechanically rotated to bring the third polarization of the at least one polarization filtering device closer to parallel with the second polarization of the backscattered light, and therefore the first polarization of the emitted laser light, thereby controlling the at least one polarization filtering device to a second desired configuration.