Display method of four-dimensional point cloud

Abstract

The invention provides a four-dimensional point cloud display method, which is applied to an FMCW laser radar and comprises the steps of determining position information of each point according to distance information and angle information of each point; determining color information of each point according to the speed information of each point; and displaying each point according to the position information, and displaying each point with a corresponding color according to the color information, the color information including hue and purity. The points with different speeds are displayed through different colors, that is, the speeds of the points are represented through hue or purity, so that the speeds of all the points can be visually distinguished, the accuracy of separation of adhered objects is improved, and the accuracy of object recognition of a sensing layer is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing, and specifically, to a method for displaying a 4D point cloud. Background Art

[0002] Currently, the mainstream lidars are divided into two major technical directions: TOF (Time of Flight) lidar and FMCW (Frequency Modulated Continuous Wave) lidar. FMCW lidar is a 4D lidar, where the 4D refers to four dimensions: horizontal viewing angle, vertical viewing angle, distance, and speed; while TOF lidar is a 3D lidar, where the 3D refers to three dimensions: horizontal viewing angle, vertical viewing angle, and distance. FMCW lidar has one more dimension than TOF lidar: speed. This is also one aspect of the advancement of FMCW lidar. FMCW lidar requires the display of point clouds during equipment debugging, production, and demonstration to customers.

[0003] Therefore, how to provide a method for displaying a 4D point cloud is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0004] This application aims to at least solve one of the technical problems existing in the prior art, and proposes a method for displaying a 4D point cloud, which realizes the display of the 4D point cloud by characterizing the speed of each point with hue and purity.

[0005] To achieve the purpose of this application, a method for displaying a 4D point cloud is provided, which is applied to an FMCW (Frequency Modulated Continuous Wave) lidar, and includes:

[0006] Determine the position information of each point according to the distance information and angle information of each point;

[0007] Determine the color information of each point according to the speed information of each point;

[0008] Display each point according to the position information, and display each point in a corresponding color according to the color information, where the color information includes hue and purity.

[0009] In some embodiments, the angle information includes a horizontal field of view angle θ and a vertical field of view angle ω, where the horizontal field of view angle θ is the angle between the projection of the point on the xy plane and the x-axis, and the vertical field of view angle ω is the angle between the point and the z-axis. The position information includes a first horizontal position DISTx, a second horizontal position DISTy, and a vertical position DISTz;

[0010] Determining the position information based on the distance information and angle information of each point includes:

[0011] Determining the first horizontal position according to the first formula;

[0012] The first formula is DISTx = sinω × cosθ × DIST;

[0013] Determining the second horizontal position according to the second formula;

[0014] The second formula is DISTy = sinω × sinθ × DIST;

[0015] Determining the vertical position according to the third formula;

[0016] The third formula is DISTz = cosω × DIST;

[0017] Where DIST is the distance between the point and the lidar.

[0018] In some embodiments, the color information includes at least two speed intervals and the hue and purity corresponding to each of the speed intervals;

[0019] Determining the color information of each point according to the speed information of each point includes:

[0020] Determining the speed interval in which the speed of each point is located according to the speed information of each point;

[0021] Determining the hue and purity of the point corresponding to the speed interval.

[0022] In some embodiments, the lidar includes an optical circulator 100, and the optical circulator 100 has a first port, a second port, a third port, a fourth port, and a fifth port; the optical circulator 100 includes two first birefringent crystals, a deflection plate group, and a second birefringent crystal arranged in sequence along the optical path direction; wherein,

[0023] The optical axis directions of the two first birefringent crystals are different, and the optical axis of the second birefringent crystal is the same as that of one of the first birefringent crystals;

[0024] When the optical circulator 100 is used for light output in the lidar, the first and second ports are used as light input ports; the first and second ports are configured to make the laser signals incident along the optical axes of the two first birefringent crystals respectively; the third port is arranged on the light output side of the second birefringent crystal, and the second birefringent crystal is configured to make laser with different polarization states converge to the third port; the third port is used as the light output port;

[0025] When the optical circulator 100 is used for receiving light in the lidar, the third port serves as the light input port; the deflection sheet group is configured to emit the received laser signals to the fourth and fifth ports respectively; the fourth and fifth ports are respectively disposed on the light output sides of the two first birefringent crystals and have different positions from the first and second ports; the fourth and fifth ports serve as light output ports.

[0026] In some embodiments, the first port and the second port are respectively located on the optical axes of the two first birefringent crystals, and the deflection sheet group is configured to emit the outgoing light rays entering the optical circulator 100 from the first port and the second port in the original polarization state.

[0027] In some embodiments, the thicknesses of the two first birefringent crystals and the second birefringent crystal in the light output direction of the optical path are equal.

[0028] In some embodiments, the surfaces of the two first birefringent crystals perpendicular to the light output direction of the optical path are flush.

[0029] In some embodiments, the deflection sheet group includes a Faraday rotator mirror and a half-wave plate, wherein,

[0030] The Faraday rotator mirror is configured to rotate the polarization planes of the forward incident light and the backward incident light of the same wavelength in the same direction by a specified angle, and the half-wave plate is configured to rotate the polarization planes of the forward incident light and the backward incident light by a specified angle, and the half-wave plate rotates the polarization plane in the opposite direction to the direction in which the Faraday rotator mirror rotates the polarization plane.

[0031] In some embodiments, the Faraday rotator mirror is configured to deflect the laser signal by 45°; the half-wave plate is configured to deflect the laser signal by 45°.

[0032] In some embodiments, the lidar further includes a laser, a beam splitting component, a bidirectional amplifier, and a receiving component, wherein,

[0033] The beam splitting component is respectively coupled to the laser, the first port and the second port of the optical circulator 100; the beam splitting component is configured to split the laser signal emitted by the laser into two laser signals with different polarization directions and respectively incident on the first port and the second port;

[0034] The bidirectional amplifier has a first transceiver end and a second transceiver end. The first transceiver end is coupled to the third port of the optical circulator 100, and the second transceiver end is configured to emit a laser signal and receive a laser echo signal; the bidirectional amplifier is configured to amplify the laser outgoing signal and the laser echo signal;

[0035] The receiving component is respectively coupled to the fourth port and the fifth port of the optical circulator 100, and the receiving component is configured to receive the laser signals in the fourth port and the fifth port respectively.

[0036] The present application has the following beneficial effects:

[0037] The method for displaying a 4D point cloud provided by the present application is applied to an FMCW lidar and includes:

[0038] Determine the position information of each point according to the distance information and the angle information of each point;

[0039] Determine the color information of each point according to the speed information of each point;

[0040] Display each point according to the position information, and display each point in a corresponding color according to the color information, where the color information includes hue and purity.

[0041] Points with different speeds are displayed in different colors, that is, the speed of the points is characterized by hue or purity, so that the speeds of each point can be intuitively distinguished, thereby improving the correct rate of separating sticky objects and enhancing the correct rate of object recognition in the perception layer. Description of the Drawings

[0042] Figure 1 It is a flowchart of the method for displaying a 4D point cloud provided by the present application;

[0043] Figure 2 It is a schematic diagram of the principle of the optical circulator 100 when the lidar emits light provided by a specific embodiment of the present application;

[0044] Figure 3 It is a schematic diagram of the principle of the optical circulator 100 when the lidar receives light;

[0045] Figure 4 It is a schematic structural diagram of the lidar provided by a specific embodiment of the present application.

[0046] Among them, Figures 1 to 4 the reference numerals in are:

[0047] 100, optical circulator; 110, first birefringent crystal; 120, second birefringent crystal;

[0048] 130, deflection plate group; 131, Faraday rotator mirror; 132, half-wave plate; 200, bidirectional amplifier; 300, laser; 400, beam splitting component; 500, receiving component. Specific Embodiments

[0049] To enable those skilled in the art to better understand the technical solution of this application, the following will describe in detail the method for displaying 4D point clouds provided by this application with reference to the accompanying drawings.

[0050] An object of this application is to provide a method for displaying 4D point clouds, which is applied to a lidar and includes:

[0051] S1. Determine the position information of each point according to the distance information and angle information of each point;

[0052] The 4D point cloud includes 3 spatial dimensions and 1 speed dimension of the points, that is, the display method needs to display the spatial positions and speeds of the points in the point cloud.

[0053] Each point in the point cloud is obtained by the lidar emitting laser signals around and then collecting the reflected signals of the object. Each point is related to the laser signal emitted by the lidar. The distance information of each point can be the distance measured by the lidar between the lidar and each measurement point on the object. The angle information of each point can be the horizontal field of view angle and vertical field of view angle of each laser signal emitted by the lidar. The position information of each point can include the three-dimensional coordinates of the point, and the position information of each point can be determined according to the position information and angle information of each point.

[0054] S2. Determine the color information of each point according to the speed information of each point;

[0055] The speed information of each point can be collected by the lidar. The speed of each point can correspond to different colors, and the speed of each point is characterized by the color information.

[0056] S3. Display each point according to the position information, and display each point in the corresponding color according to the color information, where the color information includes hue and purity.

[0057] After determining the position information and color information of each point, the positions of the points in the point cloud can be displayed through a three-dimensional coordinate system, and each point is displayed in the corresponding color. Points with different speeds can be distinguished by different hues or colors with the same hue but different purities. Characterize the speed of each point to realize the display of the 4D point cloud.

[0058] In this embodiment, the method for displaying 4D point clouds characterizes the speed of each point in the point cloud by color. According to the position information and color information of each point in the point cloud, it can be determined whether two adjacent points belong to the same object or different objects, which improves the correct rate of separating sticky objects and can also improve the correct rate of the perception layer in identifying objects. In addition, the color information includes hue and purity, so points with the same hue but different purities also have different speeds. The display method can display multiple speeds, and thus can more finely distinguish the speed differences of each point.

[0059] In some embodiments, the angular information includes the horizontal field of view angle θ and the vertical field of view angle ω. Among them, the horizontal field of view angle θ is the angle between the projection of the point on the xy plane and the x-axis, and the vertical field of view angle ω is the angle between the point and the z-axis. The angular information can be pre-stored in an angle file. The angle file may include multiple angular information, and the multiple angular information respectively corresponds to each point in the point cloud. The horizontal field of view angle θ and the vertical field of view angle ω in this embodiment are the angles in the horizontal plane and the vertical plane respectively. The user can also use the angles in other planes, which is not limited herein.

[0060] The position information includes the first horizontal position DISTx, the second horizontal position DISTy, and the vertical position DISTz. There may be multiple pieces of position information, which respectively correspond to each point in the point cloud. This embodiment uses the coordinates in the rectangular coordinate system to represent the positions of each point in the point cloud. The user can also use other methods to represent the positions of each point in the point cloud, such as the spherical polar coordinate system, etc., which is not limited herein.

[0061] Determining the position information according to the distance information and the angular information of each point includes:

[0062] Determining the first horizontal position according to the first formula;

[0063] The first formula is DISTx = sinω × cosθ × DIST;

[0064] Determining the second horizontal position according to the second formula;

[0065] The second formula is DISTy = sinω × sinθ × DIST;

[0066] Determining the vertical position according to the third formula;

[0067] The third formula is DISTz = cosω × DIST;

[0068] Among them, DIST is the distance between the point and the lidar. The position information of each point in the point cloud can be calculated through the above three formulas. If the user uses other methods to represent the positions of each point, the position information of each point can be calculated through the corresponding formulas, which will not be elaborated herein.

[0069] In some embodiments, the color information includes at least two velocity intervals and the hue and purity corresponding to each velocity interval; the display method of the 4D point cloud divides at least two velocity intervals and displays the points within each velocity interval range according to different hues and purities, so as to distinguish the velocity differences of each point.

[0070] Determining the color information of each point according to the velocity information of each point includes:

[0071] Determining the velocity interval where the velocity of each point is located according to the velocity information of each point;

[0072] Determine the hue and purity of each point corresponding to the speed range.

[0073] In a specific implementation manner of the present application, the color information includes 8 speed ranges, which are 0, (0, 5], (5, 10], (10, 15], (15, 20], (20, 30], (30, 50], (50, ∞] respectively. For example, 0 is a speed of 0 km / h, and (0, 5] is greater than 0 km / h and less than or equal to 5 km / h. The 8 speed ranges respectively correspond to green, one-eighth purity red, two-eighths purity red, three-eighths purity red, four-eighths purity red, five-eighths purity red, six-eighths purity red, and seven-eighths purity red. In this embodiment, a stationary object is displayed as green, and the remaining objects are displayed as red with different purities (saturations) according to different speeds. The user can set the number of speed ranges and the specific range division according to needs, and the user can also select the colors corresponding to each speed range according to needs, which is not limited here.

[0074] In some embodiments, the 4D point cloud may include more than two single-point clouds, and each point in the single-point cloud is located on the same object. In the subsequent data processing process, the perception layer can determine the range of the single-point cloud through the position information and color information of each point. Specifically, since the distance difference and speed difference between adjacent points in the single-point cloud are small, points with the distance difference between adjacent points within a certain range and the speed difference between adjacent points within a certain range can be used as one of the conditions for determining that the adjacent points are in the same single-point cloud. Let the distance difference between two adjacent points be Δd, the speed difference between two adjacent points be |Δv|, the distance difference determination threshold be d thre , and the speed difference determination threshold be v thre .

[0075] If the physically adjacent points in the point cloud meet the following conditions:

[0076] Δd < d thre , and |Δv| < v thre , then it is determined that the adjacent points are in the same single-point cloud, otherwise, it is determined that the adjacent points are not in the same single-point cloud.

[0077] In this embodiment, the display method of the 4D point cloud uses the same color to represent each point in the same speed range and different colors to represent each point in different speed ranges, which can better separate moving objects and stationary objects, faster moving objects and slower moving objects, promote the separation of adhered objects, and further improve the object recognition rate of the perception layer.

[0078] In some embodiments, the lidar includes an optical circulator 100, which can be used to transmit light from an input optical port to an output optical port. The optical circulator 100 has a first port a, a second port b, a third port c, a fourth port e, and a fifth port f. The first port a and the second port b are used as input optical ports when the lidar emits light, and the third port c is used as an output optical port when the lidar emits light. The optical circulator 100 includes two first birefringent crystals 110, a deflection sheet group 130, and a second birefringent crystal 120 that are arranged in sequence along the optical path direction. Among them,

[0079] the optical axis directions of the two first birefringent crystals 110 are different, and the optical axis of the second birefringent crystal 120 coincides with that of one of the first birefringent crystals 110.

[0080] A birefringent crystal is an anisotropic crystal. When a beam of light is incident on the interface of a birefringent crystal, generally, double refraction occurs and the light is refracted into two beams of light. One of the beams of light is the light refracted with a constant refractive index, that is, the ordinary light (abbreviated as O light), and the refractive index of the other beam of light in the medium changes with the incident angle and the polarization angle, that is, the extraordinary light (abbreviated as E light). When light is incident on the birefringent crystal along a special direction, double refraction does not occur, and this special direction is the optical axis of the birefringent crystal.

[0081] When the lidar emits light, the outgoing light passes through the optical circulator 100 and exits outward. The first port a and the second port b are used as input optical ports, and the first port a and the second port b are configured to make the outgoing light incident along the optical axes of the two first birefringent crystals 110 respectively; the third port c is arranged on the side of the second birefringent crystal 120 away from the first birefringent crystal 110, and the second birefringent crystal 120 is configured to make lasers with different polarization states converge to the third port c; the third port c is used as an output optical port. Specifically, the first port a and the second port b can be respectively located on the optical axes of the two first birefringent crystals 110. The two outgoing light rays passing through the first port a and the second port b do not undergo double refraction after passing through the two first birefringent crystals 110, but remain in the same direction and exit along the incident direction. After the two outgoing light rays pass through the deflection sheet group 130, they exit in the original polarization state. Finally, the two outgoing light rays converge to the third port c through the second birefringent crystal 120, and finally the two outgoing light rays exit along the same optical path.

[0082] In some embodiments, the lidar is also used to receive reflected light. When the lidar is used for receiving light, at this time, the third port c is used as an input optical port, the fourth port e and the fifth port f are used as output optical ports, and the incident light is incident into the optical circulator 100 from the third port c and exits from the fourth port e and the fifth port f.

[0083] Optionally, Figure 3 As shown, when the lidar is used for receiving light, the light incident direction of the optical circulator 100 is opposite to the light output direction of the optical path. The deflection sheet group 130 is configured to emit the received laser signals to the fourth port e and the fifth port f respectively; the fourth port e and the fifth port f are respectively arranged on one side of the two first birefringent crystals 110 away from the second birefringent crystal 120, and are different in position from the first port a and the second port b. The incident light sequentially passes through the second birefringent crystal 120, the deflection sheet group 130, and the first birefringent crystal 110 in the optical circulator 100. The second birefringent crystal 120 divides the incident light from the third port c into two paths by using its own birefringence characteristic and emits them from different positions. The deflection sheet group 130 is used to deflect the two paths of incident light so that the two paths of incident light enter the two first birefringent crystals 110 at a first preset angle and a second preset angle respectively. The two paths of incident light are respectively deflected by birefringence in the two first birefringent crystals 110, and the two paths of incident light can be emitted from the fourth port e and the fifth port f respectively after deflection. The lidar further includes a receiving component 500, and the receiving component 500 is used to receive the light emitted from the fourth port e and the fifth port f.

[0084] Optionally, in the light output state, two outgoing light rays with different polarization states are respectively incident from the first port a and the second port b. The two outgoing light rays do not undergo birefringence when passing through the first birefringent crystal 110, and the optical path does not deflect and the polarization state does not change when passing through the deflection sheet group 130. Since the optical axis of the second birefringent crystal 120 is arranged in the same direction as the optical axis of the lower first birefringent crystal 110, and the optical axis of the second birefringent crystal 120 is not arranged in the same direction as the optical axis of the upper first birefringent crystal 110, when the outgoing light ray incident from the first port a reaches the second birefringent crystal 120, its optical path direction is not parallel to the optical axis direction of the second birefringent crystal 120, and correspondingly its refractive index is different. That is to say, the outgoing light ray incident from the first port a is the E light, and the optical path of this outgoing light ray deflects towards the third port c. When the outgoing light ray incident from the second port b reaches the second birefringent crystal 120, its optical path direction is parallel to the optical axis direction of the second birefringent crystal 120, that is to say, the outgoing light ray incident from the second port b is the O light. After being refracted by the second birefringent crystal 120, the two outgoing light rays converge to the third port c together, so that the light rays with two different polarization states can be combined into the same path of light and emitted from the same port.

[0085] Optionally, in the light-incident state, the incident light rays entering from the third port c include two laser signals with different polarization states. In the second birefringent crystal , the refractive index of the extraordinary ray (E-ray) changes with the polarization angle. Therefore, the two laser signals with different polarization states are refracted by the second birefringent crystal and split into two incident light rays, which exit from different positions. Subsequently, the two incident light rays are deflected by a specified angle after passing through the deflection assembly and then respectively enter the two first birefringent crystals . Since the polarization states of the two laser signals are different from those of the outgoing light rays exiting from the first port a and the second port b after deflection, correspondingly, the refractive indices of the two incident light rays are also different from those of the two outgoing light rays, and the incident positions of the two incident light rays are also different from the exit positions of the two outgoing light rays. Therefore, the two incident light rays can respectively exit from the fourth port e and the fifth port f without occupying the first port a and the second port b.

[0086] In some embodiments, the thicknesses of the two first birefringent crystals and the second birefringent crystal in the light-exiting direction of the optical path are equal. Thus, it can ensure that the optical paths of the outgoing light rays in the first birefringent crystal and the second birefringent crystal are equal, so that the deflection angles of the outgoing light rays when passing through the first birefringent crystal and the second birefringent crystal are consistent, ensuring that the deflection degree of the optical path is consistent, and further ensuring that the incident light rays can return to the same horizontal axis after two deflections, thereby avoiding crosstalk between the incident light rays and the outgoing light rays.

[0087] In some embodiments, the surfaces of the two first birefringent crystals perpendicular to the light-exiting direction of the optical path are flush. Thus, the first port a, the second port b, the fourth port e, and the fifth port f of the optical circulator are all in the same plane, ensuring that no phase difference is generated between the two incident light rays and no phase difference is generated between the two outgoing light rays.

[0088] In some embodiments, the deflection sheet group 130 includes a Faraday rotator mirror 131 and a half-wave plate 132. Among them, the Faraday rotator mirror is a magneto-optical device with a deflection magnetic field inside. It can utilize the Faraday effect to rotate the polarization planes of the forward-incident light and the backward-incident light of the same wavelength in the same direction by the same specified angle. After the outgoing light passes through the Faraday rotator mirror 131, it will be deflected by the specified angle, and after the incident light passes through the Faraday rotator mirror 131, it will be deflected by a preset angle and then by the specified angle. Therefore, the incident light emitted from the optical circulator 100 is deflected by twice the specified angle compared to the outgoing light incident on the optical circulator 100. The half-wave plate 132 is used to rotate the polarization planes of the forward-incident light and the backward-incident light by the specified angle, and the rotation direction of the polarization plane is opposite to the rotation direction of the polarization plane by the Faraday rotator mirror 131. Specifically, after the outgoing light passes through the Faraday rotator mirror 131, it will be deflected by the specified angle, and then after passing through the half-wave plate 132, it will be deflected backward by the specified angle, so that the outgoing light returns to the original polarization state. After the incident light passes through the half-wave plate 132, it will be deflected by the specified angle, and after passing through the Faraday rotator mirror 131, it will be deflected by twice the specified angle. In a specific embodiment of the present application, the Faraday rotator mirror is configured to deflect the laser signal by 45°; the half-wave plate is configured to deflect the laser signal by 45°. Of course, the user can also use the Faraday rotator mirror 131 and the half-wave plate 132 with other specified angle values, such as 90°, etc., which are not limited here.

[0089] In this embodiment, the optical circulator 100 can be used to transmit the incident light and also to transmit the outgoing light, realizing the emission and incidence of the laser signal from the same port. When the optical circulator 100 is applied to a lidar, it can realize the coaxial transceiver of the laser signal, that is, the laser signal transmission and reception share the same optical path. Furthermore, it can greatly improve the signal-to-noise ratio, and can reuse optical devices such as optical amplifiers and optical lenses, reducing the equipment manufacturing cost and the equipment volume. In addition, the propagation paths of the incident light and the outgoing light in the optical circulator 100 are different, so it can avoid crosstalk between the incident light and the outgoing light, thus ensuring that the optical circulator 100 transmits and receives laser signals without interference, realizing signal transmission and reception isolation, improving the directivity of the optical circulator 100, and making the optical circulator 100 suitable for transmitting continuous-wave laser signals, such as frequency-modulated continuous-wave signals.

[0090] In some embodiments, it further includes a laser 300, a beam splitting component 400, a bidirectional amplifier 200, and a receiving component 500. As Figure 4As shown, the laser 300 is used to emit laser signals. The beam splitting component 400 is used to couple and connect the laser 300 with the first port a and the second port b of the optical circulator 100. The beam splitting component 400 can also split the laser signal into two laser sub-signals with different polarization directions, and the two laser sub-signals can be used as outgoing light rays and respectively incident on the first port a and the second port b of the optical circulator 100.

[0091] The bidirectional amplifier 200 is used to amplify the outgoing light ray and the incident light ray. The bidirectional amplifier 200 has a first transceiver end and a second transceiver end. The first transceiver end is coupled and connected to the third port c of the optical circulator 100, and the second transceiver end is configured to emit the laser signal and receive the laser echo signal. The laser echo signal is the laser signal reflected by the surface of the object to be measured and returned. Specifically, in the bidirectional amplifier 200, the emission and reception of the laser signal share the same optical path, which can greatly improve the signal-to-noise ratio of the lidar, and can enable the bidirectional amplifier 200 to be reused, reducing the equipment manufacturing cost and reducing the equipment volume. The bidirectional amplifier 200 is configured to amplify the laser outgoing signal and the laser echo signal, that is, the laser signal can be amplified twice by the bidirectional amplifier 200, so that the amplified laser signal is much higher than the background noise, further improving the signal-to-noise ratio and thus improving the detection accuracy.

[0092] The receiving component 500 is respectively coupled and connected to the fourth port e and the fifth port f of the optical circulator 100. The receiving component 500 is configured to respectively receive the laser signals emitted from the fourth port e and the fifth port f to analyze the laser echo signal, so as to realize lidar functions such as laser ranging.

[0093] In this embodiment, the lidar adopts the optical circulator 100 in the above embodiment. The optical circulator 100 can split the laser signal containing different polarization states into two laser signals. Therefore, there is no need to set an isolator in the bidirectional amplifier 200 of the lidar, and only signal enhancement needs to be achieved, simplifying the structure of the bidirectional amplifier 200, and thus reducing the manufacturing cost of the lidar.

[0094] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present application. However, the present application is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present application, and these modifications and improvements are also regarded as the protection scope of the present application.

Claims

1. A display method for 4D point clouds, applied to an FMCW (Frequency Modulated Continuous Wave) lidar, characterized in that, Including: Determine the position information of each point according to the distance information and angle information of each point; Determine the color information of each point according to the speed information of each point; Display each point according to the position information, and display each point in a corresponding color according to the color information, where the color information includes hue and purity.

2. The display method according to claim 1, wherein The angle information includes a horizontal field of view angle θ and a vertical field of view angle ω. Among them, the horizontal field of view angle θ is the angle between the projection of the point on the xy plane and the x axis, and the vertical field of view angle ω is the angle between the point and the z axis. The position information includes a first horizontal position DISTx, a second horizontal position DISTy, and a vertical position DISTz; The determining the position information according to the distance information and angle information of each point includes: Determine the first horizontal position according to the first formula; The first formula is DISTx = sinω × cosθ × DIST; Determine the second horizontal position according to the second formula; The second formula is DISTy = sinω × sinθ × DIST; Determine the vertical position according to the third formula; The third formula is DISTz = cosω × DIST; Where DIST is the distance between the point and the lidar.

3. The display method according to claim 1, wherein The color information includes at least two speed intervals and the hue and purity corresponding to each of the speed intervals; Determine the color information of each point according to the speed information of each point, including: Determine the speed interval in which the speed of each point is located according to the speed information of each point; Determine the hue and purity of the corresponding point according to the speed interval.

4. The display method according to any one of claims 1 to 3, characterized in that The lidar includes an optical circulator 100, and the optical circulator 100 has a first port, a second port, a third port, a fourth port, and a fifth port; the optical circulator 100 includes two first birefringent crystals, a deflection sheet group, and a second birefringent crystal arranged in sequence along the optical path direction; among them, The optical axis directions of the two first birefringent crystals are different, and the optical axis of the second birefringent crystal is the same as that of one of the first birefringent crystals; When the optical circulator 100 is used for light output in the lidar, the first and second ports are used as light input ports; the first and second ports are configured to make the laser signals incident along the optical axes of the two first birefringent crystals respectively; the third port is arranged on the light output side of the second birefringent crystal, and the second birefringent crystal is configured to make lasers with different polarization states converge to the third port; the third port is used as a light output port; When the optical circulator 100 is used for light reception in the lidar, the third port is used as a light input port; the deflection sheet group is configured to make the received laser signals respectively emit to the fourth and fifth ports; the fourth and fifth ports are respectively arranged on the light output sides of the two first birefringent crystals and are in different positions from the first and second ports; the fourth and fifth ports are used as light output ports.

5. The display method according to claim 4, characterized in that The thicknesses of the two first birefringent crystals and the second birefringent crystal in the light output direction of the optical path are equal.

6. The display method according to claim 4, wherein The surfaces of the two first birefringent crystals perpendicular to the light output direction of the optical path are flush.

7. The display method according to claim 4, wherein The deflection sheet group includes a Faraday rotator mirror and a half-wave plate, where the Faraday rotator mirror is configured to rotate the polarization planes of the forward incident light and the backward incident light of the same wavelength in the same direction by a specified angle, and the half-wave plate is configured to rotate the polarization planes of the forward incident light and the backward incident light by a specified angle, and the half-wave plate rotates the polarization plane in a direction opposite to the direction in which the Faraday rotator mirror rotates the polarization plane.

8. The display method according to claim 7, characterized in that, The Faraday rotator mirror is configured to deflect the laser signal by 45°; the half-wave plate is configured to deflect the laser signal by 45°.

9. The display method according to claim 4, wherein The lidar further includes a laser, a beam splitting component, a bidirectional amplifier, and a receiving component, where the beam splitting component is respectively coupled to the laser, the first port and the second port of the optical circulator 100; the beam splitting component is configured to split the laser signal emitted by the laser into two laser signals with different polarization directions and respectively incident on the first port and the second port; the bidirectional amplifier has a first transceiver end and a second transceiver end, the first transceiver end is coupled to the third port of the optical circulator 100, and the second transceiver end is configured to emit a laser signal and receive a laser echo signal; the bidirectional amplifier is configured to amplify the laser emission signal and the laser echo signal; the receiving component is respectively coupled to the fourth port and the fifth port of the optical circulator 100, and the receiving component is configured to respectively receive the laser signals in the fourth port and the fifth port.

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