A three-dimensional imaging lidar

Abstract

The application discloses a kind of three-dimensional imaging laser radar, comprising: light source part, for emitting pulsed light beam;Beam splitting part, for pulsed light beam is divided into first light beam and second light beam, first light beam is incident to telescopic optical system, second light beam is incident to beam combining part;Telescopic optical system makes first light beam emit, irradiate to target, and obtain echo light reflected by target, echo light is incident to beam combining part;Beam combining part is used to make echo light and second light beam converge and make convergent light incident to surface array detection part;The image element of surface array detection part records the light intensity of received convergent light and the arrival time of convergent light.Image processing device is used to obtain first imaging, second imaging and third imaging, first imaging describes the distribution of echo intensity along the longitudinal position of target upper site, second imaging describes the distribution of echo intensity along the transverse position of target upper site, and third imaging describes the distribution of echo intensity along the position of target.The application can realize the three-dimensional imaging of target.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser radar, in particular to a three-dimensional imaging laser radar. BACKGROUND

[0002] Synthetic aperture lidar (SAL) is an active imaging radar, which combines synthetic aperture technology and lidar technology, and extends the synthetic aperture technology from the microwave band to the optical band, so as to break through the diffraction limit and have extremely high imaging resolution. Therefore, deploying a synthetic aperture lidar imaging system near the geostationary orbit has important roles in space target monitoring, satellite fault diagnosis and other aspects, and has a broad application prospect.

[0003] However, current space situation awareness requires higher resolution imaging and more dimensional information acquisition, so the technology of multi-dimensional imaging gradually becomes one of the main directions in the field of space situation awareness. SUMMARY

[0004] The purpose of the present application is to provide a three-dimensional imaging laser radar, which can realize imaging of a space target in three dimensions.

[0005] To achieve the above purpose, the present application provides the following technical scheme:

[0006] A three-dimensional imaging laser radar comprises:

[0007] A light source part for emitting a pulsed light beam;

[0008] A beam splitting part arranged on the light emitting side of the light source part, for splitting the pulsed light beam into a first light beam and a second light beam, so that the first light beam is incident to a telescope optical system and the second light beam is incident to a beam combining part;

[0009] The telescope optical system is used for emitting the first light beam, so that the first light beam irradiates to a target, and acquiring a return light reflected by the target, and the acquired return light is incident to the beam combining part;

[0010] The beam combining part is used for combining the return light and the second light beam, and making the combined light incident to a planar array detection part;

[0011] The planar array detection part is provided with a plurality of pixels, and the pixels are used for recording the light intensity of the received combined light and the arrival time of the combined light;

[0012] An image processing device, connected to the area array detector, is configured to obtain a longitudinal position of the target upper site according to the time-of-arrival of the converged light recorded by the picture element, and obtain a first image in combination with the light intensity data recorded by the picture element, the first image describing a distribution of echo intensity with respect to the longitudinal position of the target upper site, and obtain a second image according to the light intensity data recorded by the plurality of picture elements corresponding to the same time-of-arrival, the second image describing a distribution of echo intensity with respect to the lateral position of the target upper site, and obtain a third image according to a spectrum, the spectrum being obtained according to an echo time sequence formed by arranging the light intensity data recorded by the picture element with respect to the time-of-arrival, the third image describing a distribution of echo intensity with respect to the bearing of the target, the target moving relative to the three-dimensional imaging lidar.

[0013] Optionally, further comprising:

[0014] A first polarization part is arranged in the light path of the first light beam, configured to change the first light beam into a first polarization state, and make the first light beam changed into the first polarization state incident to a second polarization part.

[0015] The second polarization part is configured to change the phase of the first light beam changed into the first polarization state by a quarter of a wavelength, make the first light beam changed in phase incident to the telescope optical system, and make the echo light from the telescope optical system incident to the second polarization part, change the phase of the echo light passing through the second polarization part by a quarter of a wavelength, and make the echo light changed in phase incident to the beam combining part.

[0016] A third polarization part is arranged in the light path of the second light beam, configured to change the second light beam into a second polarization state, and make the second light beam changed into the second polarization state incident to the beam combining part, the vibration direction of the light changed into the first polarization state being perpendicular to the vibration direction of the light changed into the second polarization state.

[0017] Optionally, further comprising:

[0018] A polarization beam splitting part is arranged between the first polarization part and the second polarization part, configured to make the first light beam changed into the first polarization state transmit or reflect out, so as to make the first light beam changed into the first polarization state incident to the second polarization part, and make the echo light from the second polarization part reflect out or transmit, so as to make the echo light from the second polarization part incident to the beam combining part.

[0019] Optionally, the telescope optical system comprises:

[0020] a first telescopic optical system arranged in an optical path of the first light beam, configured to emit the first light beam and to irradiate the target with the first light beam;

[0021] a second telescopic optical system configured to acquire the echo light reflected by the target and to make the acquired echo light incident on the beam combining unit.

[0022] Optionally, the image processing device is configured to obtain the longitudinal position of the target site according to the arrival time of the converged light recorded by the image element.

[0023] The image processing device is configured to obtain the longitudinal distance between the two target sites according to the following formula:

[0024] d = c * (t2-t1) / 2;

[0025] wherein d represents the longitudinal distance between the two target sites, t1 represents the arrival time of the converged light corresponding to the first target site, t2 represents the arrival time of the converged light corresponding to the second target site, and c represents the speed of light.

[0026] Optionally, the image processing device is further configured to, before obtaining the first image, set the gating time of the area array detector when acquiring the first image according to the earliest arrival time and the latest arrival time of the converged light corresponding to the target, so that when acquiring the first image, the area array detector records the converged light corresponding to the target, does not record the converged light with an arrival time earlier than the earliest arrival time of the converged light corresponding to the target, and does not record the converged light with an arrival time later than the latest arrival time of the converged light corresponding to the target.

[0027] Optionally, the image processing device is further configured to control the area array detector to start working or to stop working, wherein when the area array detector starts working, the area array detector can receive the converged light, and when the area array detector stops working, the area array detector cannot receive the converged light.

[0028] Alternatively, the three-dimensional imaging laser radar further comprises:

[0029] a shutter arranged on the light receiving side of the area array detector, wherein when the shutter is opened, the area array detector can receive the converged light, and when the shutter is closed, the area array detector cannot receive the converged light, and the image processing device is further configured to control the shutter to be opened or closed to control the gating time of the area array detector.

[0030] Optionally, the image processing device is configured to obtain a spectrum from the echo time sequence, and obtain third imaging from the spectrum.

[0031] The image processing device is configured to obtain a spectrum from the echo time sequence, and obtain the position of the target from a peak frequency included in the spectrum, the peak frequency corresponding to an amplitude in the spectrum reflecting the echo intensity.

[0032] Optionally, the image processing device is configured to obtain a spectrum from the echo time sequence, and obtain third imaging from the spectrum.

[0033] The image processing device is configured to obtain the echo time sequence from the light intensity data and the arrival time recorded by the pixels when the target is at multiple positions during the movement of the target relative to the three-dimensional imaging lidar, and obtain the spectrum from the echo time sequence.

[0034] Optionally, the aperture of the telescope optical system in the first dimension is greater than the aperture in the second dimension.

[0035] According to the above technical solution, the three-dimensional imaging lidar provided by the application comprises: a light source part for emitting a pulsed light beam; a beam splitting part arranged on the light emitting side of the light source part for splitting the pulsed light beam into a first light beam and a second light beam, so that the first light beam is incident on the telescope optical system and the second light beam is incident on the beam combining part; the telescope optical system is used to emit the first light beam, irradiate the target, and obtain the echo light reflected by the target, and the obtained echo light is incident on the beam combining part; the beam combining part is used to combine the echo light and the second light beam and make the combined light incident on the surface array detection part; the surface array detection part is provided with a plurality of pixels, and the pixels record the light intensity of the received combined light and the arrival time of the combined light. The image processing device is configured to obtain the longitudinal position of the target upper point from the arrival time of the combined light recorded by the pixels, and obtain first imaging combined with the light intensity data recorded by the pixels, the first imaging describing the distribution of echo intensity with the longitudinal position of the target upper point, and obtain second imaging from the light intensity data recorded by the pixels corresponding to the same arrival time, the second imaging describing the distribution of echo intensity with the transverse position of the target upper point, and obtain third imaging from the spectrum obtained from the echo time sequence, the third imaging describing the distribution of echo intensity with the position of the target, and the echo time sequence is arranged by the light intensity data recorded by the pixels with the arrival time. The three-dimensional imaging lidar of the application can obtain imaging of the target in the longitudinal dimension, and can also obtain imaging of the target in the transverse dimension, and can also obtain imaging of the target in the movement position dimension, so as to realize three-dimensional imaging of the space target. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only need to be some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor.

[0037] Figure 1 A schematic diagram of a three-dimensional imaging laser radar provided by an embodiment of the present application;

[0038] Figure 2 A schematic diagram of a three-dimensional imaging laser radar provided by another embodiment of the present application;

[0039] Figure 3 A schematic diagram of a three-dimensional imaging laser radar provided by an embodiment of the present application for obtaining the longitudinal position of an upper point of a target;

[0040] Figure 4-1 A schematic diagram of imaging of two point targets by an optical system with a square aperture;

[0041] Figure 4-2 A schematic diagram of imaging of two point targets by an optical system with a long strip aperture;

[0042] Figure 5 A schematic diagram of movement of a target relative to a three-dimensional imaging laser radar in an embodiment of the present application.

[0043] The reference signs in the accompanying drawings of the specification include:

[0044] 1 - light source part, 2 - beam splitting part, 3 - first polarization part, 4 - polarization beam splitting part, 5 - second polarization part, 6 - telescopic optical system, 7 - target, 8 - beam combining part, 9 - third polarization part, 10 - reflecting element, 11 - area array detection part, 12 - image processing device, 13 - first telescopic optical system, 14 - second telescopic optical system, 101 - first point target, 102 - second point target. DETAILED DESCRIPTION

[0045] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only need to be some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor.

[0046] The present embodiment provides a three-dimensional imaging laser radar, comprising:

[0047] a light source unit configured to emit a pulsed light beam;

[0048] a beam splitting unit disposed on an emission side of the light source unit and configured to split the pulsed light beam into a first light beam and a second light beam, and to cause the first light beam to be incident on a telescope optical system and the second light beam to be incident on a beam combining unit;

[0049] the telescope optical system is configured to emit the first light beam, cause the first light beam to irradiate a target, and acquire return light reflected by the target, and to cause the acquired return light to be incident on the beam combining unit;

[0050] the beam combining unit is configured to combine the return light and the second light beam and cause the combined light to be incident on a planar array detection unit;

[0051] the planar array detection unit is provided with a plurality of pixels, and the pixels are configured to record the light intensity of the received combined light and the arrival time of the combined light;

[0052] an image processing device connected to the planar array detection unit, configured to obtain the longitudinal position of the target upper point according to the arrival time of the combined light recorded by the pixels, and obtain a first image according to the light intensity data recorded by the pixels, the first image describing the distribution of return intensity with respect to the longitudinal position of the target upper point, and to obtain a second image according to the light intensity data recorded by the plurality of pixels corresponding to the same arrival time, the second image describing the distribution of return intensity with respect to the lateral position of the target upper point, and to obtain a third image according to a return time sequence formed by arranging the light intensity data recorded by the pixels with respect to the arrival time, the third image describing the distribution of return intensity with respect to the bearing of the target, and the target moving relative to the three-dimensional imaging lidar.

[0053] The light source unit emits a pulsed light beam, the beam splitting unit splits the pulsed light beam into a first light beam and a second light beam, the telescope optical system emits the first light beam to a target, and acquires return light reflected by the target, and causes the acquired return light to be incident on the beam combining unit. The second light beam split by the beam splitting unit is incident on the beam combining unit, and the beam combining unit combines the return light and the second light beam and causes the combined light to be incident on the planar array detection unit.

[0054] The light intensity of the combined light can reflect the light intensity of the return light, and the return intensity represents the light intensity of the return light reflected by the target. The arrival time of the combined light recorded by the pixels can reflect the arrival time of the corresponding return light returned to the three-dimensional imaging lidar.

[0055] The image processing device can obtain a first imaging of the target. The longitudinal position of a point on the target refers to the position of the point on the target along the direction in which the three-dimensional imaging laser radar reaches the target. The distance from a point on the target at different longitudinal positions to the three-dimensional imaging laser radar is different, and thus the return time of the echo light reflected by the point on the target at different longitudinal positions to the three-dimensional imaging laser radar is different. Based on this, the longitudinal position of the point on the target is obtained according to the return time recorded by the pixel.

[0056] The image processing device can obtain a second imaging of the target. The lateral position of a point on the target refers to the position of the point on the target on a plane intersecting the direction in which the three-dimensional imaging laser radar reaches the target. The echo light reflected by a point on the target at different lateral positions is incident on the plurality of pixels of the planar array detection unit, so that the target is imaged on the planar array detection unit.

[0057] The image processing device can obtain a third imaging of the target. The target moves relative to the three-dimensional imaging laser radar, and the frequency spectrum of the echo light received by the three-dimensional imaging laser radar is related to the movement of the target due to the Doppler effect. Based on this, the frequency spectrum is obtained according to the time sequence of the echo, and the direction in which the target is located can be obtained according to the frequency spectrum.

[0058] The three-dimensional imaging laser radar of the embodiment can obtain the imaging of the target in the longitudinal dimension, can also obtain the imaging of the target in the lateral dimension, and can also obtain the imaging of the target in the dimension of the movement direction, and thus three-dimensional imaging of the space target can be realized.

[0059] In some embodiments, the light source unit can emit a pulsed light beam with a single frequency. The light source unit can use a laser, which can be a single-frequency pulsed laser, and is not limited to a specific type, and can be but is not limited to a solid-state laser, a semiconductor laser, or a fiber laser.

[0060] In actual applications, the pulse width of the pulsed light beam can be selected according to the requirement for the resolution in the distance direction (i.e., the longitudinal dimension), and the smaller the resolution, the shorter the pulse width. The power of the pulsed light beam can be selected according to the requirement for the imaging distance, and the power of the pulsed light beam can be selected according to the relationship that the power of the light emitted by the laser radar is proportional to the fourth power of the distance, and the requirement for the power of the light beam increases rapidly with the increase of the distance.

[0061] The beam splitting unit can use but is not limited to a beam splitter, a beam splitting prism, or a beam splitting film, and can use a polarization-maintaining beam splitting prism, which can ensure that the polarization states of the reflected light and the transmitted light are the same as those of the incident light. In some embodiments, the beam splitting ratio of the beam splitting unit for splitting the pulsed light beam into the first light beam and the second light beam can be 1:1.

[0062] The beam combining part can adopt, but is not limited to, a beam combining mirror, a beam combining prism or a beam combining film, and can adopt a polarization maintaining beam combining prism, which can ensure that the polarization state of the combined light is the same as that of the incident light.

[0063] In some embodiments, the three-dimensional imaging laser radar can further include:

[0064] The first polarization part is arranged on the light path of the first light beam, and is configured to change the first light beam into a first polarization state, and the first light beam changed into the first polarization state is incident to the second polarization part.

[0065] The second polarization part is configured to change the phase of the first light beam changed into the first polarization state by one quarter of a wavelength, and the first light beam changed in phase is incident to the telescope optical system, and the echo light from the telescope optical system is incident to the second polarization part, and the phase of the echo light passing through the second polarization part is changed by one quarter of a wavelength, and the echo light changed in phase is incident to the beam combining part.

[0066] The third polarization part is arranged on the light path of the second light beam, and is configured to change the second light beam into a second polarization state, and the second light beam changed into the second polarization state is incident to the beam combining part, and the vibration direction of the light in the first polarization state is perpendicular to the vibration direction of the light in the second polarization state.

[0067] In the embodiment, the transmitting light path and the receiving light path of the three-dimensional imaging laser radar share the same telescope optical system, and the transmitting light path and the receiving light path share the same light path, so that the three-dimensional imaging laser radar has a compact structure. For example, refer to Figure 1 , Figure 1 A schematic diagram of a three-dimensional imaging laser radar is provided in an embodiment, and the solid lines with arrows in the diagram represent the light propagation path. As shown in the diagram, the pulsed light beam emitted by the light source part 1 is incident to the beam splitting part 2, and the beam splitting part 2 splits the pulsed light beam into a first light beam and a second light beam. The first light beam passes through the first polarization part 3 and the second polarization part 5 in sequence, and is then transmitted to the target 7 through the telescope optical system 6. The echo light reflected by the target 7 is acquired by the telescope optical system 6, and the acquired echo light is incident to the beam combining part 8 after passing through the second polarization part 5. The second light beam is incident to the beam combining part 8 after passing through the third polarization part 9. The beam combining part 8 combines the echo light and the second light beam, and makes the combined light incident to the area array detector 11.

[0068] The first polarization state can be a p-polarization state, and the second polarization state can be an s-polarization state. The first light beam becomes p-polarized light after passing through the first polarization part 3, and is then transmitted after passing through the second polarization part 5. The reflected echo light becomes s-polarized light after passing through the second polarization part 5, and is then further incident to the beam combining part 8. The second light beam becomes s-polarized light after passing through the third polarization part 9.

[0069] In some embodiments, the three-dimensional imaging laser radar can further comprise a polarization beam splitting part 4 disposed between the first polarization part 3 and the second polarization part 5, for transmitting or reflecting the first light beam changed into the first polarization state, so that the first light beam changed into the first polarization state is incident to the second polarization part 5, and for transmitting or reflecting the echo light from the second polarization part 5, so that the echo light from the second polarization part 5 is incident to the beam combining part 8.

[0070] In some embodiments, the three-dimensional imaging laser radar can further comprise a reflecting element 10 disposed between the beam splitting part 2 and the beam combining part 8, for reflecting the second light beam from the beam splitting part 2 to the beam combining part 8. For reference, see Figure 1 As shown, the polarization beam splitting part 4 is disposed between the first polarization part 3 and the second polarization part 5, the first light beam changed into the first polarization state from the first polarization part 3 is transmitted through the polarization beam splitting part 4 and further incident to the second polarization part 5. The polarization beam splitting part 4 reflects the echo light from the second polarization part 5 to the beam combining part 8. The reflecting element 10 is disposed between the third polarization part 9 and the beam combining part 8, the second light beam changed into the second polarization state from the third polarization part 9 is incident to the reflecting element 10 and reflected to the beam combining part 8.

[0071] The first polarization part 3 or the third polarization part 9 can adopt but is not limited to a polarizer, a polarization prism or a polarization film, and specifically can adopt a linear polarizer. The second polarization part 5 can adopt but is not limited to a quarter-wave plate, and the working wavelength thereof is consistent with the wavelength of the pulsed light beam emitted by the light source part 1. A wave plate with an optical path difference of 1 / 4 wavelength between the fast axis and the slow axis can be adopted. The polarization beam splitting part 4 can adopt but is not limited to a polarization beam splitting mirror, and a beam splitting prism or a beam splitting film that reflects / transmits the first polarization state light and transmits / reflects the second polarization state light can be adopted. The reflecting element 10 can adopt but is not limited to a mirror.

[0072] The telescopic optical system 6 realizes the imaging function of the target. In some embodiments, the telescopic optical system 6 can be used to compress the divergence angle of the emitted first light beam.

[0073] In some embodiments, the telescopic optical system can comprise:

[0074] The first telescopic optical system 13 is disposed on the light path of the first light beam, for emitting the first light beam, and for irradiating the first light beam to the target 7;

[0075] The second telescopic optical system 14 is used to acquire the echo light reflected by the target 7, and for making the acquired echo light incident to the beam combining part 8.

[0076] In this embodiment, the first telescopic optical system 13 is used to emit the light beam, and the second telescopic optical system 14 is used to receive the echo light. The emission path and the receiving path are separated. The interference of stray light and backscattering light under high-power laser conditions can be suppressed. For example, reference can be made to Figure 2 , In this embodiment, the first telescopic optical system 13 is used to emit the light beam, and the second telescopic optical system 14 is used to receive the echo light. The emission path and the receiving path are separated. The interference of stray light and backscattering light under high-power laser conditions can be suppressed. For example, reference can be made to Figure 2 A schematic diagram of a three-dimensional imaging laser radar is provided for another embodiment, in which the solid arrows represent the light propagation path. As shown in the figure, the pulsed light beam emitted by the light source part 1 is incident on the beam splitting part 2, which splits the pulsed light beam into a first light beam and a second light beam. The first light beam is emitted by the first telescopic optical system 13 towards the target 7. The second telescopic optical system 14 acquires the echo light reflected by the target 7, and the acquired echo light is incident on the beam combining part 8. The split second light beam is incident on the beam combining part 8, which combines the echo light and the second light beam and makes the combined light incident on the planar array detection part 11.

[0077] The second telescopic optical system 14 realizes the imaging function of the target. In some embodiments, the first telescopic optical system 13 can be used to compress the divergence angle of the emitted first light beam. In some embodiments, the aperture of the first telescopic optical system 13 is mainly determined by the coverage of the target area. According to the formula D´=λ*z / D, where λ represents the central wavelength of the emitted light beam, z represents the imaging distance, and D represents the aperture of the first telescopic optical system, the smaller the aperture, the larger the far-field spot size, and the weaker the echo. Therefore, generally, the spot size is as small as possible under the premise that the target does not deviate from the far-field illumination area, that is, the aperture of the first telescopic optical system is appropriately increased.

[0078] In this embodiment, the three-dimensional imaging laser radar adopts a structure in which the emission path and the receiving path are separated, which is suitable for scenarios where the target is at a relatively long distance. According to the relationship that the light power emitted by the laser radar is proportional to the fourth power of the distance, when the target is at a relatively long distance, the light power emitted by the laser radar is high, and even a very small optical transmittance can produce a large amount of stray light and backscattering interference, affecting the detection of dark and weak echoes. Therefore, if the emission path and the receiving path share the same path, a large amount of stray light and backscattering interference will be generated, and therefore, in this case, the structure in which the emission path and the receiving path are separated is preferred.

[0079] In some embodiments, an optical intensity multiplication device is provided on the light entrance side of the planar array detection part 11, which is used to enhance the light intensity of the combined light to be incident on the planar array detection part 11. In this way, the detection of dark and weak echoes can be improved, and the detection capability of dark and weak targets can be improved.

[0080] The detection sensitivity, working spectral width, resolution, and pixel size of the area array detection unit 11 can be selected according to specific application requirements. The area array detection unit 11 can be, but is not limited to, a Charge-coupled Device (CCD) area array camera, a Complementary Metal Oxide Semiconductor (CMOS) area array camera, a Photo-Diode Array (PDA), an Avalanche Photodiodes Array (APDA), or a Multi-Pixel Photon Counter (MPPC).

[0081] The image processing device 12 implements processing of the generated series of light intensity data and arrival time data and performs image reconstruction. In some embodiments, the image processing device 12 can store the light intensity data and arrival time data recorded by the area array detection unit 11. The image processing device 12 can be, but is not limited to, a computer and can be considered as an image reconstruction computer.

[0082] In some embodiments, the image processing device 12 is configured to obtain the distance between two points on the target in the longitudinal direction according to the following formula, and to obtain the longitudinal position of the points on the target according to the distance:

[0083] d = c * (t2-t1) / 2;

[0084] wherein d represents the distance between two points on the target in the longitudinal direction, t1 represents the arrival time of the converged light formed by the echo light corresponding to the first point on the target, t2 represents the arrival time of the converged light formed by the echo light corresponding to the second point on the target, and c represents the speed of light.

[0085] Reference can be made to Figure 3 , Figure 3A schematic diagram of a principle of obtaining longitudinal position of an upper point on a target by a three-dimensional imaging laser radar provided in an embodiment. The light beam emitted by the three-dimensional imaging laser radar is a pulsed light beam. The arrival time of the echo light reflected back by the front point and the rear point on the target 7 at different longitudinal positions on the target 7 to the surface array detector 11 is different. The front point is closer to the three-dimensional imaging laser radar than the rear point. The arrival time of the echo light reflected back by the rear point lags behind the arrival time of the echo light reflected back by the front point. The time difference between the arrival time of the echo light reflected back by the front point and the arrival time of the echo light reflected back by the rear point is caused by the round trip transmission of the light beam between the front point and the rear point. Then, the distance between the echo light reflected back by the front point and the echo light reflected back by the rear point is d0, and the distance between the front point and the rear point along the longitudinal direction is d, so d0 = c*(t2-t1), and d = d0 / 2.

[0086] In addition, it needs to be noted that when the distance between the echo light corresponding to the frontmost point and the echo light corresponding to the rearmost point of the target 7 is exactly equal to the distance length corresponding to the echo pulse width, the echo light corresponding to the frontmost point and the echo light corresponding to the rearmost point of the target 7 overlap together and are difficult to distinguish, so the distance direction resolution of the three-dimensional imaging laser radar can be Δl range =c*W pulse / 2, where c represents the speed of light, W pulse represents the echo pulse width. The frontmost point of the target 7 refers to the point on the target 7 closest to the three-dimensional imaging laser radar, and the rearmost point of the target 7 refers to the point on the target 7 farthest from the three-dimensional imaging laser radar.

[0087] In some embodiments, the image processing device 12 is further configured to, before obtaining the first image, set the gate time of the surface array detector 11 when the first image is obtained according to the earliest arrival time and the latest arrival time of the converged light corresponding to the target 7 received by the image element, so that when the first image is obtained, the surface array detector 11 records the converged light corresponding to the target 7, does not record the converged light with an arrival time earlier than the earliest arrival time of the converged light corresponding to the target 7, and does not record the converged light with an arrival time later than the latest arrival time of the converged light corresponding to the target 7.

[0088] The earliest arrival time of the converged light corresponding to the target 7 is the arrival time of the converged light corresponding to the frontmost point on the target 7, and the latest arrival time of the converged light corresponding to the target 7 is the arrival time of the converged light corresponding to the rearmost point on the target 7. Within the gate time of the surface array detector 11, the surface array detector 11 can receive the converged light and record the light intensity and the arrival time accordingly. Outside the gate time of the surface array detector 11, the surface array detector 11 cannot receive the converged light and cannot record the light intensity and the arrival time.

[0089] Before the first imaging is obtained, according to the light intensity data and the arrival time recorded by the pixels of the area array detector 11 after the pulsed light beam is emitted to the target 7, the earliest arrival time and the latest arrival time of the convergent light corresponding to the target 7 received by the pixels are obtained, and the gate time of the area array detector 11 during the first imaging is set according to the above. Furthermore, the area array detector 11 cannot receive the echo light before the echo light corresponding to the target 7 arrives, and the area array detector 11 also cannot receive the echo light returned after the echo light corresponding to the target 7 arrives completely during the first imaging. The area array detector 11 can receive the echo light of the target 7, and record the light intensity data and the arrival time accordingly. In this embodiment, the distance gate technology is used to reduce the stray light detected by the area array detector 11, and reduce the influence of stray light and backscattering of the emitted light beam.

[0090] The gate time of the area array detector 11 is limited by the opening time and the closing time. In actual application, the opening time of the gate time of the area array detector 11 can be slightly earlier than the earliest arrival time of the convergent light corresponding to the target 7, and the closing time of the gate time of the area array detector 11 can be slightly later than the latest arrival time of the convergent light corresponding to the target 7.

[0091] In some embodiments, the image processing device 12 is configured to control the area array detector 11 to start working or stop working. When the area array detector 11 starts working, the area array detector 11 can receive the convergent light. When the area array detector 11 stops working, the area array detector 11 cannot receive the convergent light.

[0092] In some embodiments, the three-dimensional imaging laser radar can further comprise a shutter arranged on the light entrance side of the area array detector 11. When the shutter is opened, the area array detector 11 can receive the convergent light. When the shutter is closed, the area array detector 11 cannot receive the convergent light. The image processing device 12 is configured to control the shutter to be opened or closed, so as to control the gate time of the area array detector 11.

[0093] In some embodiments, the aperture of the telescopic optical system in the first dimension is greater than the aperture of the telescopic optical system in the second dimension. The imaging resolution of the telescopic optical system in the first dimension is greater than the imaging resolution of the telescopic optical system in the second dimension. The imaging resolution of the optical system is inversely proportional to the minimum distance between two point targets that can be distinguished after the two point targets pass through the optical system. The smaller the minimum distance, the higher the imaging resolution of the optical system. The imaging resolution of the telescopic optical system in any dimension is proportional to the aperture of the telescopic optical system in the dimension.

[0094] According to the principle of optical imaging, the optical system has a larger aperture in a certain dimension, and a smaller spot image can be formed in this dimension, so that the surface target can reflect more detailed information in this dimension. For reference Figure 4-1 and Figure 4-2 , Figure 4-1 is a schematic diagram of imaging two point targets by an optical system with a square aperture, Figure 4-2 is a schematic diagram of imaging two point targets by an optical system with a long strip aperture. If the optical system has equal apertures in two dimensions and the apertures are small, such as the optical system has a square optical aperture, it is easy to form two large spot images of the two point targets and overlap each other, which is difficult to distinguish. For example Figure 4-1 , the optical system has a square optical aperture, and the spot image formed by the first point target 101 and the spot image formed by the second point target 102 are large and overlap. If the optical system has a larger aperture in one dimension, the spot image formed by the point target is smaller in this dimension, which can easily separate the two spot images formed by the two point targets in this dimension, that is, high-resolution imaging in this dimension can be realized. For example Figure 4-2 , the optical system has a long strip optical aperture, in the dimension with a larger optical aperture, the spot image formed by the first point target 101 is narrow in this dimension, and the spot image formed by the second point target 102 is narrow in this dimension, and the two can be separated.

[0095] The aperture of the telescope optical system in the first dimension is larger than that in the second dimension, and the imaging resolution of the telescope optical system in the first dimension is larger than that in the second dimension, so that high-resolution optical imaging is realized in the first dimension and low-resolution optical imaging is realized in the second dimension. For Figure 1 , the three-dimensional imaging laser radar, the telescope optical system 6 can adopt two optical whole mirrors with different sizes in two dimensions, or can adopt an optical splicing mirror, that is, a larger aperture is generated in the larger aperture dimension by optical splicing technology. For Figure 2 , the three-dimensional imaging laser radar, the second telescope optical system 14 can adopt two optical whole mirrors with different sizes in two dimensions, or can adopt an optical splicing mirror, that is, a larger aperture is generated in the larger aperture dimension by optical splicing technology.

[0096] In some embodiments, the image processing device 12 is configured to obtain a spectrum from the echo time sequence, and the third imaging is obtained from the spectrum. The image processing device 12 is configured to obtain a spectrum from the echo time sequence, and obtain the azimuth of the target 7 from the peak frequency included in the spectrum, and the amplitude of the peak frequency in the spectrum reflects the echo intensity. The echo time sequence is formed by arranging the light intensity data recorded by the pixel with the arrival time.

[0097] Target 7 moves relative to the three-dimensional imaging laser radar, and the frequency of the echo light received by the three-dimensional imaging laser radar changes due to the Doppler effect. During the movement of target 7 relative to the three-dimensional imaging laser radar, the frequency of the echo light received by the three-dimensional imaging laser radar is related to the velocity component of target 7 in the direction of the line connecting target 7 and the three-dimensional imaging laser radar, and the velocity component of target 7 in the direction of the line connecting target 7 and the three-dimensional imaging laser radar is related to the position of target 7 relative to the three-dimensional imaging laser radar. Therefore, the position of target 7 can be obtained according to the peak frequency included in the obtained frequency spectrum. The velocity component of target 7 in the direction of the line connecting target 7 and the three-dimensional imaging laser radar can be considered as the radial velocity of target 7. For example, the velocity component of target 7 in the direction of the line connecting target 7 and the three-dimensional imaging laser radar is related to the movement speed of target 7 and the angle between the line connecting target 7 and the three-dimensional imaging laser radar and the direction of the movement of target 7. Therefore, the frequency of the echo light received by the three-dimensional imaging laser radar is related to the movement speed of target 7 and the angle between the line connecting target 7 and the three-dimensional imaging laser radar and the direction of the movement of target 7. During the movement of target 7 relative to the three-dimensional imaging laser radar, the position of target 7 is different, the velocity component of target 7 in the direction of the line connecting target 7 and the three-dimensional imaging laser radar is different, and the frequency of the echo light received by the three-dimensional imaging laser radar is different. Therefore, the position of target 7 can be obtained according to the peak frequency included in the obtained frequency spectrum.

[0098] Reference can be made to Figure 5 , Figure 5 FIG. 1 is a schematic diagram of the movement of target 7 relative to the three-dimensional imaging laser radar in an embodiment. Target 7 moves at a constant speed in a straight line, and target 7 will be at different positions of the three-dimensional imaging laser radar. The frequency of the echo light returned by target 7 received by the three-dimensional imaging laser radar can be represented as: wherein v represents the movement speed of target 7, λ represents the central wavelength of the laser, and θ represents the angle between the line connecting target 7 and the three-dimensional imaging laser radar and the direction of the movement of target 7. According to the formula, it can be seen that the angle θ corresponding to the different position of target 7 is different, and the velocity component of target 7 in the direction of the line connecting target 7 and the three-dimensional imaging laser radar is different. Therefore, different Doppler frequency shifts will be generated when target 7 is at different positions. Figure 5 The above is described by taking the example of target 7 moving at a constant speed in a straight line. In other embodiments, target 7 can rotate relative to the three-dimensional imaging laser radar, and the imaging of target 7 in the movement position dimension can be realized.

[0099] In some embodiments, the image processing device 12 is configured to obtain a frequency spectrum according to a time sequence of echoes, and to obtain a third image according to the frequency spectrum. The image processing device 12 is configured to obtain the time sequence of echoes according to the light intensity data and the arrival time recorded by the image element when the target 7 is at a plurality of positions during the movement of the target 7 relative to the three-dimensional imaging laser radar, and to obtain the frequency spectrum according to the time sequence of echoes.

[0100] In some embodiments, the image processing device 12 is configured to obtain the spectrum from the echo time sequence comprises: the image processing device 12 is configured to match filter the echo time sequence, Fourier transform the echo time sequence, and obtain the spectrum. The essence of the match filter is to multiply the received signal (generally a complex number with amplitude and phase) by the complex conjugate of the signal, however, for a three-dimensional imaging lidar on a moving target, the received signal is the superposition of echo light at different azimuth positions, and it is difficult to obtain the complex conjugate of the signal corresponding to the echo light at a single azimuth position. Therefore, the echo data corresponding to the echo light of the target 7 at different azimuth positions is obtained to form an echo time sequence, and the Fourier transform of the echo time sequence is performed, that is, the spectrum of the echo time sequence is obtained. Different peak frequencies in the spectrum correspond to different azimuth positions, and the amplitude of different peak frequencies corresponds to the strength of the reflectivity of the target 7 at different azimuth positions, thereby realizing imaging in this azimuth direction. Imaging the target 7 in the azimuth dimension can also be considered as imaging the target 7 in the synthetic aperture dimension. The Fourier transform of the echo time sequence can be a fast Fourier transform.

[0101] The three-dimensional imaging lidar can realize imaging of the target in three dimensions, which are a distance dimension (corresponding to a longitudinal dimension) and two azimuth dimensions (a transverse dimension and a motion azimuth dimension), both of which are perpendicular to the distance dimension, and the two azimuth dimensions are perpendicular to each other. The imaging process is actually to obtain distinguishable information of the target in three dimensions, that is, the target reflectivity characteristics corresponding to different longitudinal positions of the target are distinguishable, and the target reflectivity characteristics corresponding to different positions in the two azimuth directions are also distinguishable, thereby realizing three-dimensional distinguishable imaging of the target. The three-dimensional imaging lidar can organically integrate the high-resolution imaging technology of the above three dimensions, thereby realizing high-resolution three-dimensional imaging.

[0102] The three-dimensional imaging laser radar can realize three-dimensional imaging. When the target 7 is located at a certain fixed position, a laser pulse beam is first emitted to irradiate the target 7, and then the echo light of the target 7 is received by the surface array detection unit 11. When the echo light of the frontmost point and the rearmost point of the target 7 is received by the surface array detection unit 11, the imaging of the target 7 in the optical dimension (corresponding to the lateral dimension) can be formed. The imaging of the target 7 in the distance dimension can be obtained by the optical image data obtained by the surface array detection unit 11 at different times, that is, the optical image slices of the target 7 in different longitudinal positions are obtained, so that the imaging in the distance dimension is realized. At this time, a rough three-dimensional image can be generated, but only in the distance dimension and the optical dimension is high resolution, and in the motion synthetic aperture dimension (corresponding to the motion azimuth dimension) is low resolution, because the optical aperture of this dimension is small, so the optical resolution is low. Finally, the motion azimuth synthetic aperture image is generated, and the echo light corresponding to the recorded light intensity data of the target 7 located at different azimuth positions is obtained, the echo time sequence is obtained, and then the echo time sequence is matched and filtered to obtain a high-resolution image in this dimension, and the imaging time is long. Replace the low-resolution image in this dimension of the rough three-dimensional image generated in the front with the high-resolution image in this dimension, and a three-dimensional high-resolution image can be obtained.

[0103] The three-dimensional imaging laser radar provided by the present application is described in detail above. In this paper, specific examples are used to explain the principles and implementation methods of the present application. The above examples are only used to help understand the method of the present application and its core idea. It should be pointed out that for ordinary skilled persons in the technical field, some improvements and modifications can be made to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A three-dimensional imaging lidar, characterized in that, include: The light source section is used to emit pulsed beams; A beam splitter is disposed on the light-emitting side of the light source unit to split the pulse beam into a first beam and a second beam, so that the first beam is incident on the telescope optical system and the second beam is incident on the beam combiner. The telescope optical system is used to emit the first beam, illuminate the target with the first beam, acquire the echo light reflected back from the target, and incident the acquired echo light onto the beam combiner. The beam combining section is used to combine the echo light with the second beam and cause the combined light to be incident on the area array detector section. The area array detector is provided with multiple pixels, which are used to record the light intensity of the received converging light and the arrival time of the converging light. An image processing device, connected to the area array detector, is used to obtain the longitudinal position of the target location based on the arrival time of the converging light recorded by the pixels, and to obtain a first image by combining the light intensity data recorded by the pixels. The first image describes the distribution of echo intensity with the longitudinal position of the target location. The device is also used to obtain a second image based on the light intensity data recorded by the multiple pixels corresponding to the same arrival time. The second image describes the distribution of echo intensity with the lateral position of the target location. Furthermore, the device is used to obtain a spectrum based on the echo time series, and to obtain a third image based on the spectrum. The third image describes the distribution of echo intensity with the orientation of the target. The echo time series is formed by arranging the light intensity data recorded by the pixels according to the arrival time. The target moves relative to the three-dimensional imaging lidar.

2. The three-dimensional imaging lidar according to claim 1, characterized in that, Also includes: A first polarization section is disposed in the optical path of the first beam to change the first beam into a first polarization state, and to cause the first beam, which has changed into the first polarization state, to be incident on the second polarization section. The second polarization section is used to change the phase of the first beam, which has become a first polarization state, by a quarter wavelength, so that the phase-changed first beam is incident on the telescope optical system, and to cause the echo light from the telescope optical system to be incident on the second polarization section, so that the phase of the echo light is changed by a quarter wavelength after passing through the second polarization section, so that the phase-changed echo light is incident on the beam combining section. The third polarization section is disposed in the optical path of the second beam and is used to change the second beam into a second polarization state, so that the second beam in the second polarization state is incident on the beam combining section, and the vibration direction of the light in the first polarization state is perpendicular to that of the light in the second polarization state.

3. The three-dimensional imaging lidar according to claim 2, characterized in that, Also includes: A polarization beam splitter is disposed between the first polarization section and the second polarization section, for transmitting or reflecting the first beam that has become a first polarization state, so that the first beam that has become a first polarization state is incident on the second polarization section, and for reflecting or transmitting the echo light from the second polarization section, so that the echo light from the second polarization section is incident on the beam combiner.

4. The three-dimensional imaging lidar according to claim 1, characterized in that, The telescope optical system includes: A first telescopic optical system is disposed in the optical path of the first beam, and is used to emit the first beam so that the first beam illuminates the target. The second telescope optical system is used to acquire the echo light reflected back from the target and to incident the acquired echo light onto the beam combiner.

5. The three-dimensional imaging lidar according to claim 1, characterized in that, The image processing device is used to obtain the longitudinal position of the target site based on the arrival time of the converging light recorded by the pixel, including: The image processing device is used to obtain the longitudinal distance between two points on the target according to the following formula, so as to obtain the longitudinal position of the points on the target based on the distance: d = c * (t2 - t1) / 2; Where d represents the longitudinal distance between the two points on the target, t1 represents the arrival time of the converging light formed by the echo light corresponding to the first point on the target, t2 represents the arrival time of the converging light formed by the echo light corresponding to the second point on the target, and c represents the speed of light.

6. The three-dimensional imaging lidar according to any one of claims 1 to 5, characterized in that, The image processing device is further configured to, before acquiring the first image, set a gating time for the area array detector when acquiring the first image based on the earliest arrival time and the latest arrival time of the converging light corresponding to the target received by the pixel, such that when acquiring the first image, the area array detector records the converging light corresponding to the target, does not record converging light whose arrival time is earlier than the earliest arrival time of the converging light corresponding to the target, and does not record converging light whose arrival time is later than the latest arrival time of the converging light corresponding to the target.

7. The three-dimensional imaging lidar according to any one of claims 1 to 5, characterized in that, The image processing device is also used to control the area array detector to start working or stop working. When the area array detector is started working, the area array detector can receive the combined light. When the area array detector is stopped working, the area array detector cannot receive the combined light. Alternatively, the three-dimensional imaging lidar may further include: The shutter is located on the light-receiving side of the area array detector. When the shutter is open, the area array detector can receive the converging light. When the shutter is closed, the area array detector cannot receive the converging light. The image processing device is also used to control the opening or closing of the shutter to control the gating time of the area array detector.

8. The three-dimensional imaging lidar according to any one of claims 1 to 5, characterized in that, The image processing device is used to obtain a spectrum based on the echo time series, and to obtain a third image based on the spectrum includes: The image processing device is used to obtain a spectrum based on the echo time series, and to obtain the location of the target based on the peak frequency included in the spectrum, wherein the amplitude corresponding to the peak frequency in the spectrum reflects the magnitude of the echo intensity.

9. The three-dimensional imaging lidar according to claim 8, characterized in that, The image processing device is used to obtain a spectrum based on the echo time series, and to obtain a third image based on the spectrum includes: The image processing device is used to obtain the echo time series based on the light intensity data and arrival time of the pixels recorded by the target at multiple positions during the target's movement relative to the three-dimensional imaging lidar, so as to obtain the spectrum based on the echo time series.

10. The three-dimensional imaging lidar according to claim 1, characterized in that, The aperture of the telescope optical system in the first dimension is larger than that in the second dimension.

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