Lidar, vehicle, and detection method

Abstract

The present disclosure provides a laser radar, a vehicle and a detection method. The laser radar comprises: a light source configured to emit probe light, the probe light being polarized light; and a receiver configured to receive a return wave of the probe light reflected by an object and convert the return wave into an electrical signal, the receiver comprising at least one polarization detection unit, the polarization detection unit comprising a plurality of polarization detectors, output signals of the plurality of polarization detectors being related to a polarization direction of the return wave.

Description

Technical Field

[0001] This disclosure generally relates to the field of lidar technology, and more particularly to a lidar, a vehicle, and a detection method. Background Technology

[0002] LiDAR (Light Detection and Ranging) is a radar system that uses laser beams to detect the position, velocity, and other characteristics of targets. It is an advanced detection method that combines laser technology with photoelectric detection technology. Due to its advantages such as high resolution, good concealment, strong resistance to active interference, good low-altitude detection performance, small size, and light weight, LiDAR is widely used in fields such as autonomous driving, transportation communication, drones, intelligent robots, and resource exploration.

[0003] Existing lidar systems generally cannot perform polarization detection, or if they can, the complex optical path design increases their size and cost. Therefore, designing a lidar system capable of polarization detection while reducing its design complexity, size, and cost is the technical problem this application aims to solve.

[0004] The content of the background section is merely the technology known to the inventor and does not necessarily represent the prior art in this field. Summary of the Invention

[0005] To address one or more of the problems existing in the prior art, this disclosure provides a lidar, comprising: a light source configured to emit probe light, the probe light being polarized light; and a receiver configured to receive an echo of the probe light reflected by an object and convert the echo into an electrical signal, the receiver including at least one polarization detection unit, the polarization detection unit including a plurality of polarization detectors, the output signals of the plurality of polarization detectors being related to the polarization direction of the echo.

[0006] Optionally, the polarization detector includes a photosensitive element and a polarizer, the polarizer being disposed upstream of the photosensitive surface of the photosensitive element, and the polarizers of the plurality of polarization detectors having different polarization directions.

[0007] Optionally, the amplitude of the output signal of the polarization detector is related to the transmittance of the polarizer to the echo, and the transmittance is related to the polarization direction of the polarizer and the polarization direction of the echo.

[0008] Optionally, the transmittance is inversely related to the angle between the polarization direction of the polarizer and the polarization direction of the echo.

[0009] Optionally, the polarization detection unit includes four polarization detectors, and the polarization direction of the polarizers of two adjacent polarization detectors is 45°.

[0010] Optionally, the polarizer includes a grating comprising a plurality of metal nanowires, the metal nanowires being made of at least one of gold, silver, aluminum, or copper.

[0011] Optionally, the polarization detector further includes a micro-optical element disposed upstream of the optical path of the polarizer.

[0012] Optionally, the polarization detector further includes an antireflection coating located between the polarizer and the photosensitive element.

[0013] Optionally, the lidar further includes a processor connected to the receiver and configured to determine the polarization information of the echo based on at least a portion of the electrical signal.

[0014] Optionally, the processor is configured to determine the polarization information based on the amplitude of the output signals of the plurality of polarization detectors.

[0015] Optionally, the processor is configured to determine at least one of the material, surface information, or shape of the object based on the polarization information.

[0016] This disclosure also provides a vehicle including the lidar described above.

[0017] This disclosure also provides a detection method for a lidar as described above, comprising: emitting a probe light using a light source, the probe light being polarized light; receiving an echo of the probe light reflected by an object using a receiver, and converting the echo into an electrical signal; determining polarization information of the echo based on at least a portion of the electrical signal; and determining at least one of the material, surface information, or shape of the object based on the polarization information.

[0018] This disclosure also provides a computer-readable storage medium including computer-executable instructions stored thereon, which, when executed by a processor, implement the detection method described above.

[0019] The lidar disclosed herein uses polarized light as the detection light. Based on the output signal of the polarization detector, the polarization information of the echo can be determined. According to the polarization information of the echo, the shape, surface information, or material of an object can be determined. This helps improve the detection performance of lidar, increase the accuracy of object recognition, and reduce the design complexity, size, and cost of lidar. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be introduced as examples below. The drawings described below are merely embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort. The drawings are used to provide a further understanding of this disclosure and constitute a part of the specification. They are used together with the embodiments of this disclosure to explain this disclosure and do not constitute a limitation of this disclosure. In the drawings:

[0021] Figure 1 A schematic diagram of an exemplary lidar consistent with some embodiments of this disclosure is shown.

[0022] Figure 2 A schematic diagram of an exemplary polarization detector consistent with some embodiments of this disclosure is shown.

[0023] Figure 3 A schematic diagram showing the transmittance of an exemplary polarizer for light at different polarization angles, consistent with some embodiments of this disclosure.

[0024] Figure 4 A schematic diagram of an exemplary polarization detector consistent with some embodiments of this disclosure is shown.

[0025] Figures 5a-5d This diagram illustrates the relationship between the output signals of an exemplary plurality of polarization detectors, consistent with some embodiments of the present disclosure, and the polarization direction of the echo.

[0026] Figure 6 A schematic diagram showing the transmittance of an exemplary polarizer to the echo according to some embodiments consistent with this disclosure is provided.

[0027] Figure 7 A schematic diagram of an exemplary polarization detection unit consistent with some embodiments of this disclosure is shown.

[0028] Figure 8 A schematic diagram of an exemplary lidar consistent with some embodiments of this disclosure is shown.

[0029] Figure 9 A schematic diagram of an exemplary vehicle consistent with some embodiments of this disclosure is shown.

[0030] Figure 10 A flowchart illustrating an exemplary detection method consistent with some embodiments of this disclosure is shown. Detailed Implementation

[0031] In the following description, only certain exemplary embodiments are shown. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of this disclosure. Therefore, the drawings and description are to be considered exemplary in nature and not restrictive.

[0032] In the description of this disclosure, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0033] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "coupling" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections, electrical connections, or connections that allow for communication; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0034] In this disclosure, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0035] The following provides numerous different embodiments or examples for implementing various structures of this disclosure. To simplify this disclosure, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit this disclosure. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, this disclosure provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0036] The following description, in conjunction with the accompanying drawings, illustrates some embodiments of this disclosure. It should be understood that the embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of this disclosure.

[0037] This disclosure provides a lidar. The lidar includes a light source and a receiver. The light source is configured to emit probe light. The probe light is polarized light. The receiver is configured to receive the echo of the probe light reflected by an object and convert the echo into an electrical signal. The receiver includes at least one polarization detection unit. The polarization detection unit includes multiple polarization detectors. The output signals of the multiple polarization detectors are related to the polarization direction of the echo. The lidar of this disclosure can achieve polarization detection. Based on the output signals of the polarization detectors, the polarization information of the echo can be determined. Based on the polarization information, rich object information can be determined, which helps to improve the detection performance of the lidar, increase the accuracy of object recognition, and reduce its design complexity, size, and cost. Details are described below.

[0038] Figure 1 A schematic diagram of an exemplary lidar consistent with some embodiments of this disclosure is shown. Figure 1 As shown, the lidar 10 includes a light source 11 and a receiver 12.

[0039] Light source 11 is configured to emit a probe light L. The probe light L is polarized light. Light source 11 may include a laser that emits polarized light. Alternatively, light source 11 may include a laser that emits unpolarized light and a polarizer. The polarizer can convert the unpolarized light emitted by the light source into polarized light. Light source 11 may include one or more lasers. When light source 11 includes multiple lasers, the multiple lasers may be arranged in a one-dimensional array or a two-dimensional array. The lasers may include semiconductor lasers, such as one or more of vertical-cavity surface-emitting lasers (VCSELs), edge-emitting lasers (EELs), and distributed feedback lasers (DFBs). In some embodiments, the lasers may also include solid-state lasers or fiber lasers.

[0040] Receiver 12 is configured to receive the echo E reflected by the probe light L from the object OB and convert the echo E into an electrical signal. Receiver 12 includes at least one polarization detection unit 13. Polarization detection unit 13 includes multiple polarization detectors 14. The output signals of the multiple polarization detectors 14 are related to the polarization direction of the echo E. For example, for the same polarization state of the echo E, the multiple polarization detectors 14 output signals of different amplitudes (or intensities). When receiver 12 receives the echo E, at least some of the polarization detectors 14 of polarization detection unit 13 can be triggered to output signals. LiDAR 10 can determine the polarization direction of the echo E based on the output signals of said at least some polarization detectors.

[0041] Figure 2 A schematic diagram of an exemplary polarization detector consistent with some embodiments of this disclosure is shown. Figure 2 As shown, the polarization detector 14 includes a polarizer 141 (green area) and a photosensitive element 142. The polarizer 141 is disposed upstream of the photosensitive surface of the photosensitive element 142. Exemplarily, the polarizer 141 can be integrated onto the photosensitive surface of the photosensitive element 142. The photosensitive element 142 can include one or more of the following: a single-photon avalanche diode (SPAD), a silicon photomultiplier (SiPM), or an avalanche photodiode (APD).

[0042] like Figure 2As shown, polarizer 141 may include a grating. The grating may include a plurality of metal nanowires 1410. The material of the metal nanowires 1410 includes at least one of gold, silver, aluminum, or copper. That is, the material of the metal nanowires 1410 may include one of the metals or alloys selected from gold, silver, aluminum, or copper.

[0043] like Figure 2 As shown, multiple metal nanowires 1410 in the grating are arranged periodically. The grating parameters include period d, width l, thickness t, and number N. It can be understood that the parameters of the metal nanowires 1410 can be used as grating parameters.

[0044] It should be noted that Figure 2 This is a cross-sectional view of the polarization detector. On a plane parallel to the photosensitive surface of the photosensitive element 142, the metal nanowires 1410 are strip-shaped. Multiple metal nanowires 1410 included in the grating are arranged in parallel. The spacing between adjacent metal nanowires 1410 is equal, but not limited to this.

[0045] The period 'd' is related to the wavelength of the probe light and the limitations of the manufacturing process. The upper limit of period 'd' can be determined by the wavelength of the probe light. The longer the wavelength of the probe light, the larger the upper limit of period 'd'. Probe light wavelengths including 905nm or 1550nm are suitable for lidar detection applications. The lower limit of period 'd' can be determined by the limitations of the manufacturing process. The more precise the manufacturing process, the higher the lower limit of period 'd'.

[0046] The thickness t can be determined by both the width l and the period d. The thickness t can be optimized after the width l and period d are determined. The optimization target could be that the transmittance of TE polarized light is >95%, and the transmittance of TM polarized light is <2%.

[0047] The number N can be determined by the period d and the width p of the polarization detector 14. The width p of the polarization detector can be 100 nm, but is not limited to this.

[0048] Table 1 uses silver nanowires as an example to illustrate the grating parameters for both 905 nm and 1550 nm wavelength probe light. It should be noted that the parameters shown in Table 1 are merely illustrative and this disclosure is not limited thereto. Furthermore, the grating parameters for other metal nanowires such as gold, aluminum, or copper can be designed in a similar manner. In practical applications, adjustments can be made as needed, and these adjustments are all within the scope of this disclosure.

[0049] Table 1

[0050]

[0051] Figure 3A schematic diagram showing the transmittance of light at different polarization angles for an exemplary polarizer consistent with some embodiments of this disclosure is provided. Figure 3 As shown in the figure, the horizontal axis represents the polarization angle θ of light. The vertical axis represents the transmittance P1 of the polarizer for light with different polarization angles. The polarization angle of the polarizer is 90°. It can be seen from the figure that the transmittance of the polarizer varies for light with different polarization angles. As the polarization angle increases, the transmittance of the polarizer first decreases and then increases. When the polarization angle is 0° or 180°, the transmittance reaches its maximum, approximately 98%. When the polarization angle is 90°, the transmittance is lowest, approximately 2%. Therefore, the polarizer of this disclosure can achieve good polarization transmission effect by using metal nanowires. It should be noted that this example uses silver nanowires with a period d = 0.4 μm, width l = 0.2 μm, thickness t = 0.21 μm, and a light wavelength of 905 nm to illustrate how the polarizer of this disclosure can achieve a polarization effect by using metal nanowires. Metal nanowires made of other metallic materials can also achieve good polarization effects.

[0052] In some embodiments, such as Figure 2 As shown, the polarization detector 14 may further include a protective layer 143 (light blue area) and an isolation layer 144 (dark gray area). The protective layer 143 covers the photosensitive surfaces of the polarizer 141 and the photosensitive element 142, protecting the surfaces of the polarizer 141 and the photosensitive surface of the photosensitive element 142 from damage. The protective layer 143 may comprise a silicon compound (such as silicon dioxide or silicon nitride) or a polymer. The isolation layer 144 is disposed around the photosensitive element 142 for isolation between different photosensitive elements 142, preventing mutual interference. The material of the isolation layer 144 can block photons. Exemplarily, the isolation layer 144 comprises oxides and metals. For example, oxides include silicon dioxide. Metals include tungsten or aluminum, or metal compounds, etc.

[0053] In some embodiments, such as Figure 2 As shown, the photosensitive element 142 also includes an absorption layer 1425 (pink area), a metal layer 1426 (yellow area), and an avalanche region 1427 (red area). The absorption layer 1425 is located downstream of the optical path of the polarizer 141 and is used to absorb photons transmitted through the polarizer 141. The absorption layer 1425 may include weakly doped silicon. The avalanche region 1427 is used to sense photons. The avalanche region 1427 includes a PN junction. When a reverse bias voltage is applied to the PN junction, photons incident on it can be absorbed by the PN junction to form a photocurrent. The metal layer 1426 can provide a reverse bias voltage to the polarization detector 14 and can also conduct the photocurrent to external circuitry. The material of the metal layer 1426 may include aluminum, copper, silver, or gold, etc.

[0054] Figure 4A schematic diagram of an exemplary polarization detector consistent with some embodiments of this disclosure is shown. Figure 4 As shown, the polarization detector 14 may also include a micro-optical element 147 (light gray area). The micro-optical element 147 is disposed upstream of the optical path of the polarizer 141. The micro-optical element 147 can focus the incident echo beam onto the absorption layer 1425 or the avalanche region 1427. The micro-optical element 147 can enable the photosensitive element 142 to sense more photons, thereby improving the photon detection efficiency and enhancing the detection performance of the lidar. The micro-optical element 147 may include microlenses or metasurface lenses, etc. The material of the micro-optical element 147 may include polymers, such as polymethyl methacrylate (PMMA) or polycarbonate (PC), etc.

[0055] In some embodiments, such as Figure 4 As shown, the polarization detector 14 may further include an antireflection coating 148 (dark blue area). The antireflection coating 148 is located between the polarizer 141 and the photosensitive element 142. The antireflection coating 148 can increase the transmittance of the incident echo beam and reduce beam reflection on the surface of the protective layer 143. The antireflection coating 148 can further improve photon detection efficiency and further improve the detection performance of the lidar. The material of the antireflection coating 148 may include one or more of silicon nitride, magnesium fluoride, titanium dioxide, and silicon dioxide. By optimizing the thickness of the antireflection coating, the beam reflectivity on the surface of the protective layer can be reduced. This disclosure does not limit the specific thickness of the coating layer, and it can be set according to requirements in practical applications.

[0056] Some polarization detectors use superconducting nanowires for polarization detection. Superconductivity refers to the fact that certain materials have zero electrical resistance when the temperature drops to a critical value (commonly absolute zero). When a single photon strikes a nanowire, it causes a localized superconducting phase transition, causing that region to lose its superconductivity and enter a "normal" state. This results in a sharp increase in the nanowire's resistance, generating an electrical signal. However, polarization detection using superconducting nanowires relies on extremely low temperatures, making it unsuitable for everyday lidar applications.

[0057] Unlike superconducting nanowires, the lidar disclosed herein uses metallic nanowires for polarization detection. This eliminates the limitations of extremely low temperatures, making it suitable not only for photoelectric detection applications at room temperature but also for harsh outdoor environments such as extreme cold and heat. This improves the environmental adaptability of the lidar and makes it suitable for automotive lidar applications. The metallic nanowires are easily integrated with the photosensitive element, increasing the receiver's integration density, reducing the lidar's size and cost, and facilitating its mounting on various platforms such as vehicles and robots.

[0058] In some embodiments, the polarization detection unit 13 includes a plurality of polarization detectors 14. The output signals of the plurality of polarization detectors 14 are related to the polarization direction of the echo E. Figures 5a-5dThis diagram illustrates the relationship between the output signals of an exemplary plurality of polarization detectors, consistent with some embodiments of this disclosure, and the polarization direction of the echo. Assuming... Figure 5a and Figure 5d The polarizers 141 are polarizers for two polarization detectors, and the polarization directions of the polarizers for these two polarization detectors are perpendicular. Figure 5a and Figure 5d The polarization directions of the echo E are vertical and horizontal, respectively. For example... Figure 5a As shown, most of the echo E can pass through polarizer 141, and most of the echo photons can be sensed by the photosensitive element downstream of the polarizer's optical path. The polarization detector where the polarizer is located can output a relatively strong signal. Figure 5d As shown, the echo E is essentially unable to pass through polarizer 141, and very few, if any, echo photons can be sensed by the photosensitive element downstream of the polarizer's optical path. The polarization detector containing this polarizer essentially cannot output a signal or outputs a very weak signal. Furthermore, assuming... Figure 5b and Figure 5c The polarizers 141 are polarizers for two polarization detectors, and the polarization direction of the polarizers for these two polarization detectors is horizontal. Figure 5b and Figure 5c The polarization directions of the echo E are horizontal and vertical, respectively. For example... Figure 5b As shown, most of the echo E can pass through polarizer 141. The polarization detector containing this polarizer can output a relatively strong signal. Figure 5c As shown, the echo E can hardly pass through the polarizer 141, which makes the polarization detector where the polarizer is located basically unable to output a signal or output a weak signal.

[0059] In some embodiments, the polarizers of the multiple polarization detectors have different polarization directions. After the echo passes through polarizers with different polarization directions, the light intensity received by the multiple polarization detectors is different, and the output signals are also different. For example, the amplitude (or intensity) of the output signals from the multiple polarization detectors is different.

[0060] In some embodiments, the output signals of the plurality of polarization detectors 14 are related to the polarization direction of the polarizer 141. For example... Figure 5a and Figure 5c As shown, the polarization direction of the echo E is always vertical, and the polarization directions of the polarizer 141 are both vertical and horizontal. Figure 5a Most of the echo E can pass through polarizer 141, and the polarization detector where the polarizer is located can output a strong output signal. Figure 5c The echo E is essentially unable to pass through polarizer 141, and the polarization detector containing this polarizer can barely output a signal or outputs a very weak signal. For example... Figure 5b and Figure 5dAs shown, the polarization direction of the echo E is horizontal, and the polarization directions of the polarizer 141 are horizontal and vertical. Figure 5b Most of the echo E can pass through polarizer 141, and the polarization detector where the polarizer is located can output a strong output signal. Figure 5d The echo E is basically unable to pass through polarizer 141, and the polarization detector where the polarizer is located can basically not output a signal or output a very weak output signal.

[0061] In some embodiments, the amplitude (or intensity) of the polarization detector's output signal is related to the transmittance of the polarizer to the echo. The higher the transmittance of the polarizer to the echo, the more photons the downstream photosensitive element can sense, and the greater the amplitude (or intensity) of the polarization detector's output signal. Conversely, the lower the transmittance of the polarizer to the echo, the fewer photons the downstream photosensitive element can sense, and the smaller the amplitude (or intensity) of the polarization detector's output signal. Exemplarily, the amplitude (or intensity) of the polarization detector's output signal is positively correlated with the transmittance of the polarizer to the echo.

[0062] In some embodiments, the transmittance of the polarizer to the echo is related to both the polarization direction of the polarizer and the polarization direction of the echo. For example... Figure 5a As shown, the polarization direction of polarizer 141 is parallel to the polarization direction of echo E, and both are perpendicular, allowing most of the echo E to pass through polarizer 141. Figure 5b As shown, the polarization direction of polarizer 141 is parallel to the polarization direction of echo E, and both are horizontal, allowing most of the echo E to pass through polarizer 141. Figure 5c As shown, the polarization direction of polarizer 141 is horizontal, while the polarization direction of echo E is vertical. Since their polarization directions are different and perpendicular to each other, echo E is essentially unable to pass through polarizer 141. Figure 5d As shown, the polarization direction of polarizer 141 is vertical, while the polarization direction of the echo E is horizontal. Since their polarization directions are different and perpendicular to each other, the echo E is essentially unable to pass through polarizer 141. Therefore, the transmittance of the polarizer to the echo is related to the polarization directions of both the polarizer and the echo. When the polarization direction of the polarizer is parallel to the polarization direction of the echo, the transmittance is high. When the polarization direction of the polarizer is perpendicular to the polarization direction of the echo, the transmittance is low. The different transmittances of the polarizer to the echo result in different amplitudes (or intensities) of the output signal of the polarization detector.

[0063] In some embodiments, the transmittance of the polarizer to the echo is inversely related to the angle between the polarization direction of the polarizer and the polarization direction of the echo. This angle ranges from 0 to 90°. Figure 6 A schematic diagram showing the transmittance of an exemplary polarizer to the echo according to some embodiments consistent with this disclosure is provided. Figure 6 As shown in the figure, the horizontal axis represents the angle α between the polarization direction of the polarizer and the polarization direction of the echo. The vertical axis represents the transmittance P2 of the polarizer to the echo. It can be seen from the figure that the larger the angle between the polarizer's polarization direction and the echo's polarization direction, the lower the transmittance of the polarizer to the echo. When the angle between the polarizer's polarization direction and the echo's polarization direction is 90°, the transmittance of the polarizer to the echo is the lowest, approximately 2%. The smaller the angle between the polarizer's polarization direction and the echo's polarization direction, the higher the transmittance of the polarizer to the echo. When the angle between the polarizer's polarization direction and the echo's polarization direction is 0°, the transmittance of the polarizer to the echo is the highest, approximately 96%. The smaller the angle between the polarizer's polarization direction and the echo's polarization direction, the higher the transmittance of the polarizer to the echo, and the greater the amplitude (or intensity) of the polarization detector's output signal. Conversely, the larger the angle between the polarizer's polarization direction and the echo's polarization direction, the lower the transmittance of the polarizer to the echo, and the smaller the amplitude (or intensity) of the polarization detector's output signal.

[0064] The lidar disclosed herein includes a receiver comprising one or more polarization detection units. Each polarization detection unit includes multiple polarization detectors. The output signals of these multiple polarization detectors are related to the polarization direction of the echo. Since the polarizers of the multiple polarization detectors have different polarization directions, their angles with the polarization direction of the echo are different, resulting in different transmittances of the echo and different numbers of photons that can be sensed by the downstream photosensitive element, thus causing the output signals of the multiple polarization detectors to differ. Therefore, multiple polarization detectors with different polarization directions can be set in the polarization detection unit of the receiver, utilizing the differences in absorption of echoes with different polarization directions by these detectors to achieve the detection of the echo's polarization information.

[0065] In some embodiments, the polarization detection unit may include four polarization detectors. Assume the polarizers of the four polarization detectors are positioned at the horizontal (0°), vertical (90°), +45°, and -45° directions, respectively. Based on the electrical signals output by these four polarization detectors, the echo intensity measured by each detector can be determined. Based on the measured echo intensity, the Stokes parameters of the echo incident on the polarization detection unit can be calculated. The Stokes parameters S0, S1, S2, and S3 describe the state of polarized light. Based on the Stokes parameters, the polarization state of the echo can be determined.

[0066] The Stokes parameter S0 represents the total light intensity. The total light intensity S0 is the sum of the horizontal polarization component I0 and the vertical polarization component I... 90 The sum of the light intensities. Or, the total light intensity S0 is the sum of the +45° polarization component I. +45 With -45° polarization component I -45 The sum of light intensities. The total light intensity S0 can be calculated according to (Equation 1) or (Equation 2).

[0067] S0=I0+I 90 ... (Equation 1).

[0068] S0 = I +45 +I -45 ... (Equation 2).

[0069] Stokes parameter S1 represents the horizontal polarization component I0 and the vertical polarization component I... 90 The difference in light intensity. S1 can be calculated according to (Equation 3).

[0070] S1 = I0 - I 90 ... (Equation 3).

[0071] Stokes parameter S2 represents the +45° polarization component I. +45 With -45° polarization component I -45 The difference in light intensity. S2 can be calculated according to (Equation 4).

[0072] S2=I +45 -I -45 ... (Equation 4).

[0073] The Stokes parameter S3 represents the intensity difference between the right-hand circularly polarized component and the left-hand circularly polarized component. In some embodiments, when calculating the intensity difference between the right-hand and left-hand circularly polarized components, a combination of a quarter-wave plate (λ / 4) and a polarizer can be used to measure the intensity of right-hand and left-hand circularly polarized light.

[0074] In some embodiments, the polarization characteristics of the echo can be calculated based on the Stokes parameters. For example, the degree of polarization (DoP) can be calculated according to (Equation 5). The degree of polarization (DoP) represents the total degree of polarization of light, and its value ranges from 0 to 1. A DoP value of 0 indicates completely unpolarized light. A DoP value of 1 indicates completely polarized light. A DoP value between 0 and 1 indicates partially polarized light (or partially unpolarized light).

[0075]

[0076] For example, the polarization angle β can be calculated according to (Equation 6). The polarization angle β represents the polarization direction of light and the vibration direction of linearly polarized light.

[0077]

[0078] Figure 7 A schematic diagram of an exemplary polarization detection unit consistent with some embodiments of this disclosure is shown. For example... Figure 7As shown, the polarization detection unit 13 includes four polarization detectors 14-1, 14-2, 14-3, and 14-4. Each polarization detector includes a polarizer composed of multiple metal nanowires 1410. The polarization direction of the polarizer is related to the arrangement direction of the metal nanowires 1410. The arrangement direction of the metal nanowires can be understood as the angle between the metal nanowires and the positive horizontal direction. For example, the angles between the metal nanowires 1410 and the positive horizontal direction of polarization detectors 14-1, 14-2, 14-3, and 14-4 are 0°, 45°, 90°, and 135°, respectively. The arrangement directions of the metal nanowires 1410 of these four polarization detectors are 0°, 45°, 90°, and 135°, respectively. Exemplarily, the polarization direction of the polarizer is related to the arrangement direction of the metal nanowires. Different polarization directions of the polarizer of the polarization detector can be achieved by metal nanowires with different arrangement directions. For example, the polarization directions of polarization detectors 14-1, 14-2, 14-3, and 14-4 are spaced 45° apart. The polarization directions of the polarizers of two adjacent polarization detectors are within a 45° angle. For example, the polarization directions of the polarizers of polarization detectors 14-1 and 14-2 are within a 45° angle. The polarization directions of the polarizers of polarization detectors 14-2 and 14-3 are within a 45° angle. The polarization directions of the polarizers of polarization detectors 14-3 and 14-4 are within a 45° angle. The polarization directions of the polarizers of polarization detectors 14-4 and 14-1 are within a 45° angle. This 45° angle between the polarization directions of the polarizers of two adjacent polarization detectors results in differences in absorption for echoes with different polarization directions, which helps to efficiently and accurately determine the polarization information of the echo.

[0079] In some embodiments, the lidar also includes a processor. The processor is connected to the receiver and configured to determine the polarization information of the echo based on at least a portion of the electrical signal. Figure 8 A schematic diagram of an exemplary lidar consistent with some embodiments of this disclosure is shown. Figure 8 As shown, the lidar 10 also includes a processor 15. The processor 15 is connected to the receiver 12 and configured to determine the polarization information of the echo E based on at least a portion of the electrical signal. The processor 15 can be connected to a polarization detector 14 to determine the polarization information of the echo E based on the electrical signal output by at least a portion of the polarization detector 14.

[0080] like Figure 7 and Figure 8 As shown, the output signal of polarization detector 14-1 can characterize the horizontal polarization component I0 of the echo E. The output signal of polarization detector 14-3 can characterize the vertical polarization component I0 of the echo E. 90 The output signal of polarization detector 14-2 can characterize the +45° polarization component I of the echo E. +45The output signal of polarization detector 14-4 can characterize the -45° polarization component I of the echo E. -45 When the lidar emits probe light, and the probe light is reflected by an object to form an echo, at least some of the polarization detectors 14-1, 14-2, 14-3, and 14-4 receive the echo and output an electrical signal after photoelectric conversion. The processor 15 can determine the polarization information of the echo E based on the electrical signal output by the at least some polarization detectors. The polarization information may include one or more of the following: degree of polarization, polarization type, polarization direction, or polarization angle. The polarization type may include linear polarization, circular polarization, or elliptic polarization. For example, the processor 15 can determine the degree of polarization of the echo E based on the output signals of the polarization detectors 14-1, 14-2, 14-3, and 14-4, and according to (Equation 5), that is, determine the degree of polarization of the echo E, and determine whether the echo E is fully polarized light, fully unpolarized light, or partially polarized light. As another example, the processor 15 can determine whether the echo E is linearly polarized light based on the output signals of the polarization detectors 14-1 and 14-4. For example, processor 15 can determine whether echo E is circularly polarized light and its polarization direction based on the output signals of polarization detectors 14-2 and 14-3. As another example, processor 15 can determine the polarization angle of echo E based on the output signals of polarization detectors 14-1, 14-2, 14-3, and 14-4, and according to equations (3), (4), and (6).

[0081] In some embodiments, the processor 15 can determine the polarization information of the echo based on the amplitude (or intensity) of the output signals from the multiple polarization detectors. For example, the processor 15 can determine whether the echo is polarized light based on the difference in amplitude (or intensity) of the output signals from the multiple polarization detectors. If the difference in amplitude (or intensity) of the output signals from the multiple polarization detectors is large (e.g., greater than a threshold), the processor 15 can determine that the echo is polarized light. If the difference in amplitude (or intensity) of the output signals from the multiple polarization detectors is small (e.g., not greater than a threshold), the processor 15 can determine that the echo is unpolarized light.

[0082] For example, processor 15 can determine the polarization type of the echo based on the amplitude (or intensity) of the output signals from multiple polarization detectors. Figure 7 As shown, the processor 15 can determine whether the echo E is linearly polarized light and its polarization direction based on the amplitude (or intensity) of the output signals from polarization detectors 14-1 to 14-4. If the amplitude (or intensity) of the output signals from multiple polarization detectors differs significantly, the processor 15 can determine that the echo is linearly polarized light. The processor 15 can also determine the polarization direction of the echo based on the differences or proportions in the amplitude (or intensity) of the output signals from different polarization detectors.

[0083] For example, processor 15 can determine whether echo E is circularly polarized light based on the output signals of multiple polarization detectors. If the amplitude (or intensity) of the output signals of multiple polarization detectors is substantially the same, processor 15 can determine that the echo is circularly polarized light.

[0084] In some embodiments, the processor 15 is configured to determine the time of flight based on the echo, and then determine the distance to the object based on the time of flight. For example, the processor 15 may determine the distance to the object based on principles such as time-of-flight, phase method, etc.

[0085] In some embodiments, the processor 15 is configured to determine the reflectivity of an object based on the echo.

[0086] In some embodiments, the processor 15 can determine the reflectivity of an object based on the polarization information of the probe light and the echo. For example, the reflectivity of the object's reflective surface can be derived based on the Fresnel reflectance coefficient by multi-angle measurement or modulation of polarized light.

[0087] In some embodiments, the processor 15 can determine at least one of the material, surface information, or shape of an object based on the polarization information of the probe light and the echo.

[0088] In some embodiments, the processor 15 can determine the material of an object based on the polarization information of the echo. For example, the surface of a metallic material causes a large phase delay and ellipsometric polarization. The P-polarization component has a large amplitude (or intensity) and phase difference relative to the S-polarization component. Dielectric materials, such as glass and plastic, show less change in the polarization state of the echo after surface reflection. Reflectivity is related to the incident angle and wavelength. For example, near Brewster's angle, P-deflection is almost non-reflective. The processor 15 can determine the material of the object based on the changes in the polarization state of the probe light and the echo.

[0089] In some embodiments, the processor 15 can determine the roughness of an object's surface based on the polarization information of the echo. For example, a smooth object has high reflectivity, while a rough object has low reflectivity. Polarized light incident on a smooth object will still produce a polarized echo, while light incident on a rough object will produce an unpolarized echo. The processor 15 can determine the roughness of the object's surface based on the polarization state of the probe light and the echo.

[0090] In some embodiments, the processor 15 can determine the shape or geometric features of an object based on the polarization information of the echo. A planar surface can maintain the polarization state of the probe light essentially. For curved surfaces such as spheres and cylinders, the incident angles at different reflection points are different, causing variations in the spatial distribution of the echo's polarization state. The processor 15 can reconstruct the three-dimensional shape of the object through multi-angle polarization imaging.

[0091] In some embodiments, the processor 15 can determine one or more of the material, surface information, or shape of an object based on the polarization information of the echo. In some embodiments, the processor 15 can determine one or more of the material, surface information, or shape of an object based on one or more of the polarization information of the echo, including the degree of polarization, polarization type, polarization direction, or polarization angle.

[0092] In some embodiments, the processor 15 may include processing circuitry, a central processing unit (CPU), a micro control unit (MCU), a graphics processing unit (GPU), a digital signal processor (DSP), other general-purpose processors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), complex programmable logic devices (CPLDs) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, and other components or circuits.

[0093] In some embodiments, the lidar 10 may further include a memory (not shown) and a display (not shown). The memory and the display may be coupled to the processor 15 respectively. The memory may store the polarization information of the echo, the distance information of the object, the reflectivity information, the material, surface information or shape of the object, etc. The display may display the polarization information of the echo, the distance information of the object, the reflectivity information, the material, surface information or shape of the object, etc., for visualization output.

[0094] In some embodiments, the memory may include random access memory (RAM) or non-volatile memory. Further, the memory may include at least one of phase-change random access memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), read-only memory (ROM), and electrically erasable programmable read-only memory (EEPROM).

[0095] In some embodiments, the display may include a liquid-crystal display (LCD), an LED display (light emitting diode, LED), an OLED display (organic light emitting diode, OLED), or other displays.

[0096] The lidar disclosed herein uses polarized light as the detection light. Based on the output signal of the polarization detector, the polarization information of the echo can be determined. According to the polarization information of the echo, the shape, surface information, or material of an object can be determined. This helps improve the detection performance of lidar, increase the accuracy of object recognition, and reduce the design complexity, size, and cost of lidar.

[0097] This disclosure also provides a vehicle. Figure 9 A schematic diagram of an exemplary vehicle consistent with some embodiments of this disclosure is shown. Figure 9 As shown, vehicle 20 includes lidar 10 as described above.

[0098] In some embodiments, the controller of vehicle 20 (not shown) can communicate with the processor 15 of lidar 10, and the two can exchange data. Information such as the polarization information of the echo, the distance to the object, reflectivity, shape, surface information, or material determined by the processor 15 of lidar 10 can be communicated to the controller of vehicle 20 and displayed on the central control display, head-up display, or other locations of vehicle 20. The controller of vehicle 20 can control lidar 10 to perform object detection.

[0099] In some embodiments, the lidar 10 can be installed at any location on the vehicle 20, including but not limited to the front, roof, front, rear, side, interior, exterior, windshield, rearview mirror, headlights, etc.

[0100] In some embodiments, the vehicle may include a device equipped with lidar, such as a car, autonomous vehicle, truck, van, electric vehicle, bus, train, high-speed train, motorcycle, golf cart, off-road vehicle, agricultural vehicle, engineering vehicle, or any other vehicle (e.g., robot, logistics vehicle, unmanned delivery vehicle, suitcase, trolley, boat, airplane, helicopter, drone, lawnmower, submarine, amusement park equipment or vehicle, warehouse equipment or vehicle, production equipment, etc.).

[0101] The vehicle disclosed herein, equipped with the lidar described above, has a wide range of applications and strong environmental adaptability, enabling the detection of echo polarization information. Based on the echo polarization information, the shape, surface information, or material of objects around the vehicle can be determined. This helps improve the vehicle's environmental perception capabilities and enhance driver and passenger safety.

[0102] This disclosure also provides a detection method for lidar as described above. Figure 10 A flowchart illustrating an exemplary detection method consistent with some embodiments of this disclosure is shown. Figure 10 As shown, detection method 30 includes steps S310 to S370. Step S310 involves emitting a probe light using a light source; the probe light is polarized light. Step S330 involves receiving the echo of the probe light reflected by the object using a receiver, and converting the echo into an electrical signal. Step S350 involves determining the polarization information of the echo based on at least a portion of the electrical signal. Step S370 involves determining at least one of the object's material, surface information, or shape based on the polarization information. The light source and receiver used in detection method 30 are the light source 11 and receiver 12 of the lidar 10 as described above. Detection method 30 and its various steps can be executed by the processor 15 of the lidar 10 as described above, or by the controller of the vehicle 20, or by a remote controller. The detection method disclosed herein can achieve object information detection in multiple dimensions, improving the accuracy of the detection results.

[0103] This disclosure also provides a computer-readable storage medium including computer-executable instructions stored thereon, which, when executed by a processor, implement the detection method 30 as described above.

[0104] This disclosure can take the form of a computer program product implemented on one or more storage media containing program code. Computer storage media include permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to: PRAM, SRAM, DRAM, other types of RAM, ROM, EEPROM, flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital video disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transfer medium that can be used to store information accessible by a computing device.

[0105] It should be noted that this specification provides method operation steps as shown in the embodiments or diagrams, but based on conventional or non-inventive labor, more or fewer operation steps may be included. The order of steps listed in the embodiments is merely one possible execution order among many steps and does not represent the only execution order. In actual system or device products, the methods shown in the embodiments or flowcharts can be executed sequentially or in parallel.

[0106] It should be noted that although several modules of the lidar have been mentioned in the detailed description above, this division is not mandatory. In fact, according to embodiments of this disclosure, the features and functions of two or more modules described above can be implemented in one module. Conversely, the features and functions of one module described above can be further divided and embodied by multiple modules.

[0107] It should be noted that this disclosure may only include Figure 1-10 Any one or more features of any one or more embodiments. In other words, not all of the features shown need to be implemented simultaneously in the lidar / vehicle / detection method of this disclosure.

Claims

1. A lidar, characterized in that, include: A light source is configured to emit probe light, wherein the probe light is polarized light; and The receiver is configured to receive the echo of the probe light reflected by the object and convert the echo into an electrical signal. The receiver includes at least one polarization detection unit, which includes multiple polarization detectors, the output signals of which are related to the polarization direction of the echo.

2. The lidar according to claim 1, characterized in that, The polarization detector includes a photosensitive element and a polarizer. The polarizer is disposed upstream of the photosensitive surface of the photosensitive element, and the polarizers of the multiple polarization detectors have different polarization directions.

3. The lidar according to claim 2, characterized in that, The amplitude of the output signal of the polarization detector is related to the transmittance of the polarizer to the echo, and the transmittance is related to the polarization direction of the polarizer and the polarization direction of the echo.

4. The lidar according to claim 3, characterized in that, The transmittance is inversely related to the angle between the polarization direction of the polarizer and the polarization direction of the echo.

5. The lidar according to claim 2, characterized in that, The polarization detection unit includes four polarization detectors, and the polarization direction of the polarizers of two adjacent polarization detectors is 45°.

6. The lidar according to claim 2, characterized in that, The polarizer includes a grating, which comprises a plurality of metal nanowires, the metal nanowires being made of at least one of gold, silver, aluminum, or copper.

7. The lidar according to any one of claims 2-6, characterized in that, The polarization detector also includes a micro-optical element, which is disposed upstream of the optical path of the polarizer.

8. The lidar according to any one of claims 2-6, characterized in that, The polarization detector also includes an antireflection coating, which is located between the polarizer and the photosensitive element.

9. The lidar according to any one of claims 1-6, characterized in that, It also includes a processor connected to the receiver and configured to determine the polarization information of the echo based on at least a portion of the electrical signal.

10. The lidar according to claim 9, characterized in that, The processor is configured to determine the polarization information based on the amplitude of the output signals from the plurality of polarization detectors.

11. The lidar according to claim 10, characterized in that, The processor is configured to determine at least one of the material, surface information, or shape of the object based on the polarization information.

12. A vehicle, characterized in that, Including the lidar as described in any one of claims 1-11.

13. A detection method for a lidar as described in any one of claims 1-11, characterized in that, include: A light source is used to emit detection light, which is polarized light; A receiver is used to receive the echo of the probe light reflected by the object and convert the echo into an electrical signal; The polarization information of the echo is determined based on at least a portion of the electrical signal; and Based on the polarization information, at least one of the material, surface information, or shape of the object is determined.

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