Three-dimensional imaging laser radar

Abstract

The invention discloses a three-dimensional imaging laser radar, and the radar comprises a light source part which is used for emitting a pulse light beam; the beam splitting part is used for splitting the pulse light beam into a first light beam and a second light beam, the first light beam enters the telescopic optical system, and the second light beam enters the beam combining part; the telescopic optical system enables the first light beam to be emitted to irradiate a target and obtains echo light reflected by the target, and the echo light enters the beam combining part; the beam combining part is used for converging the echo light and the second light beam and enabling the converged light to enter the area array detection part; the pixels of the area array detection unit record the light intensity of the received merged light and the arrival time of the merged light. The image processing device is used for obtaining a first image, a second image and a third image, the first image describes the distribution of the echo intensity along with the longitudinal position of the upper site of the target, the second image describes the distribution of the echo intensity along with the transverse position of the upper site of the target, and the third image describes the distribution of the echo intensity along with the orientation of the target. According to the invention, three-dimensional imaging of the target can be realized.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a three-dimensional imaging laser radar. Background Art

[0002] Synthetic Aperture Lidar (SAL) is an active imaging radar that combines synthetic aperture technology with Lidar technology, extending synthetic aperture technology from the microwave band to the optical band, breaking through the diffraction limit and having extremely high imaging resolution. Therefore, deploying synthetic aperture Lidar imaging systems near the geostationary orbit plays an important role in space target monitoring, satellite fault diagnosis, etc., and has broad application prospects.

[0003] However, current space situational awareness requires both higher-resolution imaging and the acquisition of more dimensional information, so the technology to achieve multi-dimensional imaging has gradually become one of the main directions in the field of space situational awareness. Summary of the invention

[0004] The purpose of the present invention is to provide a three-dimensional imaging laser radar that can realize imaging of space targets in three dimensions.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A three-dimensional imaging laser radar, comprising:

[0007] A light source part, used for emitting a pulse light beam;

[0008] A beam splitter, disposed on the light-emitting side of the light source, for splitting the pulse light beam into a first light beam and a second light beam, so that the first light beam is incident on the telescopic optical system, and the second light beam is incident on the beam combining unit;

[0009] The telescopic optical system is used to emit the first light beam, irradiate the first light beam to a target, obtain echo light reflected by the target, and make the obtained echo light incident on the beam combining part;

[0010] The beam combining unit is used to combine the echo light with the second light beam and make the combined light incident on the area array detection unit;

[0011] The area array detection unit is provided with a plurality of pixels, and the pixels are used to record the light intensity of the received converged light and the arrival time of the converged light;

[0012] An image processing device is connected to the area array detection unit, and is used to obtain the longitudinal position of the site on the target according to the arrival time of the converged light recorded by the pixel, and obtain a first imaging in combination with the light intensity data recorded by the pixel, the first imaging describing the distribution of echo intensity with the longitudinal position of the site on the target, and is used to obtain a second imaging according to the light intensity data recorded by the multiple pixels corresponding to the same arrival time, the second imaging describing the distribution of echo intensity with the lateral position of the site on the target, and is used to obtain a spectrum according to the echo time series, and obtain a third imaging according to the spectrum, the third imaging describing the distribution of echo intensity with the direction of the target, the echo time series is formed by arranging the light intensity data recorded by the pixel according to the arrival time, and the target moves relative to the three-dimensional imaging lidar.

[0013] Optionally, it also includes:

[0014] A first polarizing unit is disposed on the optical path of the first light beam, and is used to change the first light beam into a first polarization state, so that the first light beam changed into the first polarization state is incident on the second polarizing unit;

[0015] The second polarization section is used to change the phase of the first light beam that has been changed into the first polarization state by a quarter wavelength, so that the first light beam after the phase change is incident on the telescopic optical system, and to make the echo light from the telescopic optical system incident on the second polarization section, so that the phase of the echo light changes by a quarter wavelength after passing through the second polarization section, and the echo light after the phase change is incident on the beam combining section;

[0016] The third polarization unit is arranged on the optical path of the second light beam, and is used to change the second light beam into a second polarization state, so that the second light beam changed into the second polarization state is incident on the beam combining unit, and the vibration direction of the light in the first polarization state is perpendicular to the light in the second polarization state.

[0017] Optionally, it also includes:

[0018] A polarization beam splitter is arranged between the first polarization section and the second polarization section, and is used to allow the first light beam that has been changed into a first polarization state to pass through or to reflect the first light beam that has been changed into the first polarization state so that the first light beam that has been changed into the first polarization state is incident on the second polarization section, and is used to reflect the echo light from the second polarization section or to allow the echo light from the second polarization section to pass through so that the echo light from the second polarization section is incident on the beam combining section.

[0019] Optionally, the telescopic optical system comprises:

[0020] A first telescopic optical system is disposed on the optical path of the first light beam and is used to emit the first light beam so that the first light beam irradiates the target;

[0021] The second telescopic optical system is used to obtain the echo light reflected by the target and make the obtained echo light incident on the beam combining part.

[0022] Optionally, the image processing device is used to obtain the longitudinal position of the point on the target according to the arrival time of the converged light recorded by the pixel, including:

[0023] The image processing device is used to obtain the distance between two points on the target along the longitudinal direction according to the following formula, so as to obtain the longitudinal position of the point on the target according to the distance:

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

[0025] Among them, d represents the longitudinal distance between two points on the target, t1 represents the arrival time of the convergent light formed by the echo light corresponding to the first point on the target, t2 represents the arrival time of the convergent light formed by the echo light corresponding to the second point on the target, and c represents the speed of light.

[0026] Optionally, the image processing device is also used to set the gating time of the area array detection unit when acquiring the first image according to the earliest arrival time and the latest arrival time of the converged light corresponding to the target received by the pixel before acquiring the first image, so that when acquiring the first image, the area array detection unit records the converged light corresponding to the target, does not record the converged light whose arrival time is earlier than the earliest arrival time of the converged light corresponding to the target, and does not record the converged light whose arrival time is later than the latest arrival time of the converged light corresponding to the target.

[0027] Optionally, the image processing device is further used to control the area array detection unit to start working or shut down working, when the area array detection unit starts working, the area array detection unit can receive the converged light, and when the area array detection unit shuts down working, the area array detection unit cannot receive the converged light;

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

[0029] A shutter is arranged on the light incident side of the area array detection unit. When the shutter is opened, the area array detection unit can receive the converged light. When the shutter is closed, the area array detection unit cannot receive the converged 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 detection unit.

[0030] Optionally, the image processing device is used to obtain a spectrum according to the echo time series, and obtaining the third imaging according to the spectrum includes:

[0031] The image processing device is used to obtain a frequency spectrum according to an echo time series, and obtain the direction of the target according to a peak frequency included in the frequency spectrum. The amplitude corresponding to the peak frequency in the frequency spectrum reflects the echo intensity.

[0032] Optionally, the image processing device is used to obtain a spectrum according to the echo time series, and obtaining the third imaging according to the spectrum includes:

[0033] The image processing device is used to obtain the echo time series based on the light intensity data and arrival time recorded by the pixel when the target is in multiple orientations during the movement of the target relative to the three-dimensional imaging lidar, so as to obtain the spectrum based on the echo time series.

[0034] Optionally, the telescopic optical system has a larger aperture in the first dimension than in the second dimension.

[0035] It can be seen from the above technical scheme that a three-dimensional imaging laser radar provided by the present invention includes: a light source part, which is used to emit a pulse light beam; a beam splitting part, which is arranged on the light output side of the light source part, and is used to split the pulse light beam into a first light beam and a second light beam, so that the first light beam is incident on the telescopic optical system, and the second light beam is incident on the beam combining part; the telescopic optical system is used to emit the first light beam, so that it irradiates the target, and obtain the echo light reflected by the target, so that the obtained echo light is incident on the beam combining part; the beam combining part is used to merge the echo light with the second light beam and make the merged light incident on the area array detection part; the area array detection part is provided with a plurality of pixels, and the pixels record the light intensity of the received merged light and the arrival time of the merged light. The image processing device is used to obtain the longitudinal position of the point on the target according to the arrival time of the converged light recorded by the pixel, and to obtain the first imaging in combination with the light intensity data recorded by the pixel, the first imaging describing the distribution of the echo intensity with the longitudinal position of the point on the target, and to obtain the second imaging according to the light intensity data recorded by the plurality of pixels corresponding to the same arrival time, the second imaging describing the distribution of the echo intensity with the lateral position of the point on the target, and to obtain the spectrum according to the echo time sequence, and to obtain the third imaging according to the spectrum, the third imaging describing the distribution of the echo intensity with the azimuth of the target, the echo time sequence is formed by arranging the light intensity data recorded by the pixel with the arrival time. The three-dimensional imaging laser radar of the present invention can obtain the imaging of the target in the longitudinal dimension, the imaging of the target in the lateral dimension, and the imaging of the target in the dimension of the moving azimuth, so that the three-dimensional imaging of the space target can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] FIG1 is a schematic diagram of a three-dimensional imaging laser radar provided by an embodiment of the present invention;

[0038] FIG2 is a schematic diagram of a three-dimensional imaging laser radar provided by another embodiment of the present invention;

[0039] 3 is a schematic diagram of the principle of obtaining the longitudinal position of a point on a target by a three-dimensional imaging laser radar provided by an embodiment of the present invention;

[0040] Figure 4-1 is a schematic diagram of imaging two point targets when the optical system has a square aperture;

[0041] Figure 4-2 is a schematic diagram of imaging two point targets when the optical system has a long strip aperture;

[0042] FIG. 5 is a schematic diagram of the movement of a target relative to a three-dimensional imaging laser radar in one embodiment of the present invention.

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

[0044] 1-light source unit, 2-beam splitting unit, 3-first polarization unit, 4-polarization beam splitting unit, 5-second polarization unit, 6-telescopic optical system, 7-target, 8-beam combining unit, 9-third polarization unit, 10-reflective element, 11-array detection unit, 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 enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0046] This embodiment provides a three-dimensional imaging laser radar, including:

[0047] A light source part, used for emitting a pulse light beam;

[0048] A beam splitter, disposed on the light-emitting side of the light source, for splitting the pulse light beam into a first light beam and a second light beam, so that the first light beam is incident on the telescopic optical system, and the second light beam is incident on the beam combining unit;

[0049] The telescopic optical system is used to emit the first light beam, irradiate the first light beam to a target, obtain echo light reflected by the target, and make the obtained echo light incident on the beam combining part;

[0050] The beam combining unit is used to combine the echo light with the second light beam and make the combined light incident on the area array detection unit;

[0051] The area array detection unit is provided with a plurality of pixels, and the pixels are used to record the light intensity of the received converged light and the arrival time of the converged light;

[0052] An image processing device is connected to the area array detection unit, and is used to obtain the longitudinal position of the site on the target according to the arrival time of the converged light recorded by the pixel, and obtain a first imaging in combination with the light intensity data recorded by the pixel, the first imaging describing the distribution of echo intensity with the longitudinal position of the site on the target, and is used to obtain a second imaging according to the light intensity data recorded by the multiple pixels corresponding to the same arrival time, the second imaging describing the distribution of echo intensity with the lateral position of the site on the target, and is used to obtain a spectrum according to the echo time series, and obtain a third imaging according to the spectrum, the third imaging describing the distribution of echo intensity with the direction of the target, the echo time series is formed by arranging the light intensity data recorded by the pixel according to the arrival time, and the target moves relative to the three-dimensional imaging lidar.

[0053] The light source emits a pulse beam, and the beam splitter splits the pulse beam into a first beam and a second beam, so that the first beam is incident on the telescopic optical system, and the telescopic optical system emits the first beam to the target, and obtains the echo light reflected by the target, and the obtained echo light is incident on the beam combining unit. The second beam emitted by the beam splitter is incident on the beam combining unit, and the beam combining unit merges the echo light with the second beam and makes the merged light incident on the area array detection unit.

[0054] The light intensity of the combined light can reflect the light intensity of the echo light, which represents the light intensity of the echo light reflected by the target. The arrival time recorded by the pixel for the combined light can reflect the arrival time of the corresponding echo light returning to the three-dimensional imaging laser radar.

[0055] The image processing device can obtain the first imaging of the target. The longitudinal position of the point on the target refers to the position of the point on the target along the direction from the three-dimensional imaging laser radar to the target. Points at different longitudinal positions on the target have different distances from the three-dimensional imaging laser radar. Therefore, the echo light reflected from points at different longitudinal positions on the target returns to the three-dimensional imaging laser radar at different arrival times. Based on this, the longitudinal position of the point on the target is obtained according to the arrival time recorded by the pixel.

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

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

[0058] The three-dimensional imaging laser radar of this embodiment can obtain imaging of the target in the longitudinal dimension, imaging of the target in the lateral dimension, and imaging of the target in the dimension of motion direction, thereby realizing three-dimensional imaging of space targets.

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

[0060] In practical applications, the pulse width of the pulse beam can be selected based on the requirements for the resolution in the distance direction (i.e., the longitudinal dimension). The smaller the resolution, the shorter the pulse width. The power of the pulse beam can be selected based on the requirements for the imaging distance. The power of the pulse beam can be selected based on the relationship that the optical power emitted by the laser radar is proportional to the fourth power of the distance. As the distance increases, the requirements for the beam power increase rapidly.

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

[0062] The beam combining part may adopt but is not limited to a beam combining mirror, a light combining prism or a light combining film, and may adopt a polarization-maintaining light 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 may further include:

[0064] A first polarizing unit is disposed on the optical path of the first light beam, and is used to change the first light beam into a first polarization state, so that the first light beam changed into the first polarization state is incident on the second polarizing unit;

[0065] The second polarization section is used to change the phase of the first light beam that has been changed into the first polarization state by a quarter wavelength, so that the first light beam after the phase change is incident on the telescopic optical system, and to make the echo light from the telescopic optical system incident on the second polarization section, so that the phase of the echo light changes by a quarter wavelength after passing through the second polarization section, and the echo light after the phase change is incident on the beam combining section;

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

[0067] In this embodiment, the transmitting optical path and the receiving optical path of the three-dimensional imaging laser radar share the same telescopic optical system, and the transmitting optical path and the receiving optical path are configured as a common optical path, so that the three-dimensional imaging laser radar has a compact structure. For example, reference may be made to FIG. 1, which is a schematic diagram of a three-dimensional imaging laser radar provided by an embodiment, and the solid line with an arrow in the figure represents the light propagation path. As shown in the figure, the pulse light beam emitted by the light source unit 1 is incident on the beam splitter 2, and the beam splitter 2 splits the pulse light beam into a first light beam and a second light beam. After the first light beam passes through the first polarization unit 3 and the second polarization unit 5 in sequence, it is emitted to the target 7 through the telescopic optical system 6. The telescopic optical system 6 obtains the echo light reflected back by the target 7, and the obtained echo light passes through the second polarization unit 5 and is incident on the beam combining unit 8. The second light beam passes through the third polarization unit 9 and is incident on the beam combining unit 8. The beam combining unit 8 merges the echo light with the second light beam and makes the merged light incident on the array detection unit 11.

[0068] The first polarization state may be a p polarization state, and the second polarization state may be an s polarization state. The first light beam becomes p polarization state light after passing through the first polarization unit 3, and is emitted after passing through the second polarization unit 5. The reflected echo light becomes s polarization state light after passing through the second polarization unit 5, and is further incident on the beam combining unit 8. The second light beam becomes s polarization state light after passing through the third polarization unit 9.

[0069] In some embodiments, the three-dimensional imaging laser radar may also include: a polarization beam splitter 4, which is arranged between the first polarization section 3 and the second polarization section 5, and is used to allow the first light beam that has been changed into the first polarization state to pass through or to reflect the first light beam that has been changed into the first polarization state so that the first light beam that has been changed into the first polarization state is incident on the second polarization section 5, and is used to reflect the echo light from the second polarization section 5 or to allow the echo light from the second polarization section 5 to pass through so that the echo light from the second polarization section 5 is incident on the beam combining section 8.

[0070] In some embodiments, the three-dimensional imaging laser radar may further include: a reflective element 10, which is disposed between the beam splitter 2 and the beam combiner 8, and is used to reflect the second light beam from the beam splitter 2 to the beam combiner 8. As shown in FIG1, a polarization beam splitter 4 is disposed between the first polarization section 3 and the second polarization section 5, and the first light beam from the first polarization section 3 that has been changed to the first polarization state passes through the polarization beam splitter 4 and further enters the second polarization section 5. The polarization beam splitter 4 reflects the echo light from the second polarization section 5 to the beam combiner 8. A reflective element 10 is disposed between the third polarization section 9 and the beam combiner 8, and the second light beam from the third polarization section 9 that has been changed to the second polarization state enters the reflective element 10 and is reflected to the beam combiner 8.

[0071] The first polarization unit 3 or the third polarization unit 9 may adopt but is not limited to a polarizer, a polarization prism or a polarization film, and specifically a linear polarizer. The second polarization unit 5 may adopt but is not limited to a quarter wave plate, and its operating wavelength is consistent with the wavelength of the pulse light beam emitted by the light source unit 1. A wave plate with an optical path difference of 1 / 4 wavelength between the fast axis and the slow axis may be used. The polarization beam splitting unit 4 may adopt but is not limited to a polarization beam splitter, and may adopt 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. The reflective element 10 may adopt but is not limited to a reflector.

[0072] The telescopic optical system 6 realizes the function of imaging 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 may include:

[0074] A first telescopic optical system 13 is disposed on the optical path of the first light beam, and is used to emit the first light beam so that the first light beam irradiates the target 7;

[0075] The second telescopic optical system 14 is used for acquiring the echo light reflected by the target 7 and making the acquired echo light incident on the beam combining unit 8 .

[0076] In this embodiment, a light beam is emitted by the first telescopic optical system 13, and the echo light is received by the second telescopic optical system 14, and a structure in which the emission light path and the receiving light path are separated is adopted. The interference of stray light and backscattered light under high-power laser conditions can be suppressed. For example, reference can be made to FIG. 2, which is a schematic diagram of a three-dimensional imaging laser radar provided by another embodiment, and the solid line with an arrow in the figure represents the light propagation path. As shown in the figure, the pulse light beam emitted by the light source unit 1 is incident on the beam splitter 2, and the beam splitter 2 splits the pulse light beam into a first light beam and a second light beam. The first light beam is emitted toward the target 7 through the first telescopic optical system 13. The second telescopic optical system 14 obtains the echo light reflected by the target 7, and the obtained echo light is incident on the beam combining unit 8. The separated second light beam is incident on the beam combining unit 8, and the beam combining unit 8 merges the echo light with the second light beam and makes the merged light incident on the array detection unit 11.

[0077] The second telescopic optical system 14 realizes the function of imaging 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 based on the coverage of the target area, according to the aperture-limited far-field spot size 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, on the premise of ensuring that the target does not deviate from the far-field illumination area, the spot size is as small as possible, 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 transmitting optical path and the receiving optical path are separated, which is suitable for scenes where the target is at a long distance. According to the relationship that the optical power emitted by the laser radar is proportional to the fourth power of the distance, when the target is at a long distance, the optical power emitted by the laser radar is high, and even a very small optical transmittance can produce large stray light and backscatter interference, affecting the detection of weak echoes. If the transmitting optical path and the receiving optical path share the same optical path, large stray light and backscatter interference will be generated. Therefore, in this case, it is preferred to adopt a structure in which the transmitting optical path and the receiving optical path are separated.

[0079] In some embodiments, a light intensity multiplier is provided on the light incident side of the area array detection unit 11 to enhance the light intensity of the converged light to be incident on the area array detection unit 11. In this way, the detection of dim echoes can be improved, and the detection capability of dim targets can be improved.

[0080] The detection sensitivity, working spectrum 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 use but is not limited to a charge-coupled device (CCD) area array camera, a complementary metal oxide semiconductor (CMOS) area array camera, a photodiode array (PDA), an avalanche photodiode array (APDA) or a microchannel plate (MPPC).

[0081] The image processing device 12 processes a series of light intensity data and arrival time data generated and reconstructs the image. 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 a computer 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 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 point on the target according to the distance:

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

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

[0085] Please refer to FIG3, which is a schematic diagram of the principle of obtaining the longitudinal position of a point on a target by a three-dimensional imaging laser radar provided by an embodiment. The light beam emitted by the three-dimensional imaging laser radar is a pulsed light beam. After the light beam is irradiated to the target 7, the echo light reflected by the front point and the rear point at different longitudinal positions on the target 7 arrives at the array detection unit 11 at different times. The front point is closer to the three-dimensional imaging laser radar than the rear point. The arrival time of the echo light reflected by the rear point is delayed than the arrival time of the echo light reflected by the front point. The time difference between the arrival time of the echo light at the front point and the arrival time of the echo light at the rear point is generated by the light beam being transmitted back and forth between the front point and the rear point. Then, the distance between the echo light reflected by the front point and the echo light reflected by the rear point is d0, and the distance between the front point and the rear point in the longitudinal direction is d, then d0=c*(t2-t1), d=d0 / 2.

[0086] It should also be noted that when the distance between the echo light corresponding to the front and rear positions of target 7 is exactly equal to the distance length corresponding to the echo pulse width, the echo light corresponding to the front and rear positions of target 7 overlap and are difficult to distinguish, thus obtaining a range resolution of Δl range =c*W pulse / 2, where c is the speed of light, W pulse Indicates the echo pulse width. The frontmost position of target 7 refers to the position on target 7 with the shortest distance to the three-dimensional imaging laser radar, and the rearmost position of target 7 refers to the position on target 7 with the longest distance to the three-dimensional imaging laser radar.

[0087] In some embodiments, the image processing device 12 is also used to set the gating time of the area array detection unit 11 when acquiring the first imaging according to the earliest arrival time and the latest arrival time of the converged light corresponding to the target 7 received by the pixel before acquiring the first imaging, so that when acquiring the first imaging, the area array detection unit 11 records the converged light corresponding to the target 7, does not record the converged light whose arrival time is earlier than the earliest arrival time of the converged light corresponding to the target 7, and does not record the converged light whose arrival time is 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 position on the target 7, and the latest arrival time of the converged light corresponding to the rearmost position on the target 7 is the arrival time of the converged light corresponding to the rearmost position on the target 7. During the gating time of the area array detection unit 11, the area array detection unit 11 can receive the converged light and record the light intensity and arrival time accordingly. Outside the gating time of the area array detection unit 11, the area array detection unit 11 cannot receive the converged light and cannot record the light intensity and arrival time.

[0089] Before obtaining the first imaging, the earliest arrival time and the latest arrival time of the converged light corresponding to the target 7 received by the pixel are obtained according to the light intensity data and arrival time recorded by the pixel of the array detection unit 11 after emitting a pulse light beam to the target 7, and the gating time of the array detection unit 11 when obtaining the first imaging is obtained according to this setting. Furthermore, when obtaining the first imaging, the echo light before the echo light corresponding to the target 7 arrives is prevented from being received by the array detection unit 11, and the echo light returned after all the echo lights corresponding to the target 7 arrive is prevented from being received by the array detection unit 11. The array detection unit 11 is enabled to receive the echo light of the target 7 and record the light intensity data and arrival time accordingly. In this embodiment, the range gating technology is used to reduce the stray light detected by the array detection unit 11, and the influence of the stray light and the backscattering of the emitted light beam can be reduced.

[0090] The gating time of the area array detection unit 11 is limited by the opening time and the closing time. In practical applications, the opening time of the gating time of the area array detection unit 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 gating time of the area array detection unit 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 used to control the area array detection unit 11 to start working or shut down working. When the area array detection unit 11 starts working, the area array detection unit 11 can receive the converged light. When the area array detection unit 11 shuts down working, the area array detection unit 11 cannot receive the converged light.

[0092] In some embodiments, the three-dimensional imaging laser radar may also include: a shutter, which is arranged on the light input side of the area array detection unit 11, and when the shutter is opened, the area array detection unit 11 can receive the converged light, and when the shutter is closed, the area array detection unit 11 cannot receive the converged light; the image processing device 12 is used to control the opening or closing of the shutter to control the gating time of the area array detection unit 11.

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

[0094] According to the principle of optical imaging, if the aperture of an optical system is large in a certain dimension, a smaller spot image of a point target can be formed in this dimension, that is, the size of the spot image is smaller in this dimension, so the surface target can reflect clearer detail information in this dimension. Please refer to Figures 4-1 and 4-2. Figure 4-1 is a schematic diagram of imaging two point targets when the optical system has a square aperture, and Figure 4-2 is a schematic diagram of imaging two point targets when the optical system has a long strip aperture. If the apertures of the two dimensions of the optical system are equal and both are small, such as the optical system has a square optical aperture, it is easy for the two point targets to be imaged as two larger spot images that overlap with each other and are difficult to distinguish. For example, in 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 both large and overlap. If the aperture of one dimension of the optical system is large, the spot image formed by the point target is small in this dimension, which makes it easy to separate the two spot images formed by the two point targets in this dimension, and high-resolution imaging in this dimension can be achieved. For example, in FIG4-2, the optical system has a long optical aperture. In the dimension where the optical aperture is larger, the spot image formed by the first point target 101 is narrower in this dimension, and the spot image formed by the second point target 102 is narrower in this dimension, and the two can be separated.

[0095] The telescopic optical system has a larger aperture in the first dimension than in the second dimension, and the imaging resolution of the telescopic optical system in the first dimension is larger than the imaging resolution in the second dimension, and high-resolution optical imaging is achieved in the first dimension, and low-resolution optical imaging is achieved in the second dimension. For the three-dimensional imaging laser radar shown in FIG1 , the telescopic optical system 6 can use an optical whole mirror with two different dimensions, or an optical splicing mirror, that is, a larger aperture is generated by optical splicing technology in a larger aperture dimension. For the three-dimensional imaging laser radar shown in FIG2 , the second telescopic optical system 14 can use an optical whole mirror with two different dimensions, or an optical splicing mirror, that is, a larger aperture is generated by optical splicing technology in a larger aperture dimension.

[0096] In some embodiments, the image processing device 12 is used to obtain a spectrum according to the echo time sequence, and obtaining the third imaging according to the spectrum includes: the image processing device 12 is used to obtain a spectrum according to the echo time sequence, and obtain the position of the target 7 according to the peak frequency included in the spectrum, and the amplitude corresponding to 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] 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 will change 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 the target 7 and the three-dimensional imaging laser radar, and the velocity component of target 7 in the direction of the line connecting the 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 spectrum. The velocity component of target 7 in the direction of the line connecting the target 7 and the three-dimensional imaging laser radar can be considered as the radial velocity of target 7. For example, since the velocity component of target 7 in the direction of the line connecting the 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 the target 7 and the three-dimensional imaging laser radar relative to the movement direction of target 7, then 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 the target 7 and the three-dimensional imaging laser radar relative to the movement direction of target 7. When target 7 moves relative to the three-dimensional imaging lidar, the position of target 7 is different, the velocity component of target 7 in the direction of the line connecting the three-dimensional imaging lidar is different, and the frequency of the echo light received by the three-dimensional imaging lidar is different. Therefore, the position of target 7 can be obtained based on the peak frequency included in the obtained spectrum.

[0098] Please refer to Figure 5, which is a schematic diagram of the movement of a target relative to a three-dimensional imaging laser radar in one embodiment. The target 7 moves in a uniform straight line, and the target 7 will be at different positions of the three-dimensional imaging laser radar. The frequency of the echo light returned by the target 7 and received by the three-dimensional imaging laser radar can be expressed as: , where v represents the target's moving speed, λ represents the laser center wavelength, and θ represents the angle between the line connecting the target 7 and the three-dimensional imaging laser radar relative to the moving direction of the target 7. According to the formula, the angle θ corresponding to the target 7 at different azimuth positions is different, and the velocity component of the target 7 in the direction of the line connecting the target 7 and the three-dimensional imaging laser radar is different. Therefore, when the target 7 is located at different azimuth positions, different Doppler frequency shifts will be generated. Figure 5 is illustrated by taking the target 7 doing uniform linear motion as an example. In other embodiments, the target 7 can rotate relative to the three-dimensional imaging laser radar, so as to realize imaging of the target 7 in the moving azimuth dimension.

[0099] In some embodiments, the image processing device 12 is used to obtain a spectrum based on an echo time series, and obtaining a third image based on the spectrum includes: the image processing device 12 is used to obtain the echo time series based on the light intensity data and arrival times recorded by the pixels when the target 7 is at multiple orientations during the movement of the target 7 relative to the three-dimensional imaging lidar, so as to obtain the spectrum based on the echo time series.

[0100] In some embodiments, the image processing device 12 is used to obtain a spectrum according to the echo time sequence, including: the image processing device 12 is used to match filter the echo time sequence, perform Fourier transform on the echo time sequence, and obtain the spectrum. The essence of matched filtering 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 laser radar for a moving target, the received signal is a superposition of echo lights at different azimuth positions, and it is difficult to obtain the complex conjugate of the corresponding signal of 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 echo time sequence is Fourier transformed to obtain the spectrum of the echo time sequence. Different peak frequencies in the spectrum correspond to different azimuth positions, and the amplitudes of different peak frequencies correspond to the strength of the reflectivity of the target 7 at different azimuth positions, thereby realizing imaging in the 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 performed on the echo time series may be a fast Fourier transform.

[0101] This three-dimensional imaging laser radar can realize imaging of the target in three dimensions, namely, a distance dimension (corresponding to the longitudinal dimension) and two azimuth dimensions (lateral dimension and motion azimuth dimension respectively). Both azimuth dimensions are perpendicular to the distance dimension, and the two azimuth dimensions are perpendicular to each other. The imaging process is actually to obtain resolvable information of the target in three dimensions, that is, the target reflectivity characteristics corresponding to different longitudinal positions of the target are resolvable, and the target reflectivity characteristics corresponding to different positions in the two azimuth directions are also resolvable, thereby realizing three-dimensional resolvable imaging of the target. This three-dimensional imaging laser radar can organically integrate the high-resolution imaging technologies in the above three dimensions, thereby realizing high-resolution three-dimensional imaging.

[0102] The three-dimensional imaging laser radar realizes three-dimensional imaging by emitting a laser pulse beam to illuminate the target 7 when the target 7 is located at a fixed position, and then using the array detection unit 11 to receive the echo light of the target 7. When the echo light of the front and rear positions of the target 7 are received by the 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 obtain the optical image slices of the target 7 in the distance direction at different times through the optical image data obtained by the array detection unit 11 at different times, that is, the light intensity distribution of the target 7 at different longitudinal positions is obtained, thereby realizing the imaging in the distance dimension. At this time, a rough three-dimensional image can be generated, but it is high-resolution only in the distance dimension and the optical dimension, and low-resolution in the motion synthetic aperture dimension (corresponding to the motion azimuth dimension). This is because the optical aperture of this dimension is small, so the optical resolution is low. Finally, to generate a synthetic aperture image in the motion azimuth, it is necessary to obtain the light intensity data corresponding to the echo light of the target 7 at different azimuth positions, obtain the echo time series, and then perform matched filtering on the echo time series to obtain a high-resolution image of this dimension, which takes a long time to image. The high-resolution image of this dimension replaces the low-resolution image of this dimension in the rough three-dimensional image generated previously, and a three-dimensional high-resolution image can be obtained.

[0103] The above is a detailed introduction to a three-dimensional imaging laser radar provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A three-dimensional imaging laser radar, characterized in that: include: A light source part, used for emitting a pulse light beam; A beam splitter, disposed on the light-emitting side of the light source, for splitting the pulse light beam into a first light beam and a second light beam, so that the first light beam is incident on the telescopic optical system, and the second light beam is incident on the beam combining unit; The telescopic optical system is used to emit the first light beam, irradiate the first light beam to a target, obtain echo light reflected by the target, and make the obtained echo light incident on the beam combining part; The beam combining unit is used to combine the echo light with the second light beam and make the combined light incident on the area array detection unit; The area array detection unit is provided with a plurality of pixels, and the pixels are used to record the light intensity of the received converged light and the arrival time of the converged light; An image processing device is connected to the area array detection unit, and is used to obtain the longitudinal position of the site on the target according to the arrival time of the converged light recorded by the pixel, and obtain a first imaging in combination with the light intensity data recorded by the pixel, the first imaging describing the distribution of echo intensity with the longitudinal position of the site on the target, and is used to obtain a second imaging according to the light intensity data recorded by the multiple pixels corresponding to the same arrival time, the second imaging describing the distribution of echo intensity with the lateral position of the site on the target, and is used to obtain a spectrum according to the echo time series, and obtain a third imaging according to the spectrum, the third imaging describing the distribution of echo intensity with the direction of the target, the echo time series is formed by arranging the light intensity data recorded by the pixel according to the arrival time, and the target moves relative to the three-dimensional imaging lidar.

2. The three-dimensional imaging laser radar according to claim 1, characterized in that: Also includes: A first polarizing unit is disposed on the optical path of the first light beam, and is used to change the first light beam into a first polarization state, so that the first light beam changed into the first polarization state is incident on the second polarizing unit; The second polarization section is used to change the phase of the first light beam that has been changed into the first polarization state by a quarter wavelength, so that the first light beam after the phase change is incident on the telescopic optical system, and to make the echo light from the telescopic optical system incident on the second polarization section, so that the phase of the echo light changes by a quarter wavelength after passing through the second polarization section, and the echo light after the phase change is incident on the beam combining section; The third polarization unit is arranged on the optical path of the second light beam, and is used to change the second light beam into a second polarization state, so that the second light beam changed into the second polarization state is incident on the beam combining unit, and the vibration direction of the light in the first polarization state is perpendicular to the light in the second polarization state.

3. The three-dimensional imaging laser radar according to claim 2, characterized in that: Also includes: A polarization beam splitter is arranged between the first polarization section and the second polarization section, and is used to allow the first light beam that has been changed into a first polarization state to pass through or to reflect the first light beam that has been changed into the first polarization state so that the first light beam that has been changed into the first polarization state is incident on the second polarization section, and is used to reflect the echo light from the second polarization section or to allow the echo light from the second polarization section to pass through so that the echo light from the second polarization section is incident on the beam combining section.

4. The three-dimensional imaging laser radar according to claim 1, characterized in that: The telescopic optical system comprises: A first telescopic optical system is disposed on the optical path of the first light beam and is used to emit the first light beam so that the first light beam irradiates the target; The second telescopic optical system is used to obtain the echo light reflected by the target and make the obtained echo light incident on the beam combining part.

5. The three-dimensional imaging laser radar according to claim 1, characterized in that: The image processing device is used to obtain the longitudinal position of the point on the target according to the arrival time of the converged light recorded by the pixel, including: The image processing device is used to obtain the distance between two points on the target along the longitudinal direction according to the following formula, so as to obtain the longitudinal position of the point on the target according to the distance: d = c * (t2-t1) / 2; Among them, d represents the longitudinal distance between two points on the target, t1 represents the arrival time of the convergent light formed by the echo light corresponding to the first point on the target, t2 represents the arrival time of the convergent 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 laser radar according to any one of claims 1 to 5, characterized in that: The image processing device is also used to set the gating time of the area array detection unit when acquiring the first image according to the earliest arrival time and the latest arrival time of the converged light corresponding to the target received by the pixel before acquiring the first image, so that when acquiring the first image, the area array detection unit records the converged light corresponding to the target, does not record the converged light whose arrival time is earlier than the earliest arrival time of the converged light corresponding to the target, and does not record the converged light whose arrival time is later than the latest arrival time of the converged light corresponding to the target.

7. The three-dimensional imaging laser radar according to any one of claims 1 to 5, characterized in that: The image processing device is further used to control the area array detection unit to start working or shut down working. When the area array detection unit is started working, the area array detection unit can receive the converged light. When the area array detection unit is shut down working, the area array detection unit cannot receive the converged light. Alternatively, the three-dimensional imaging laser radar further includes: A shutter is arranged on the light incident side of the area array detection unit. When the shutter is opened, the area array detection unit can receive the converged light. When the shutter is closed, the area array detection unit cannot receive the converged 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 detection unit.

8. The three-dimensional imaging laser radar according to any one of claims 1 to 5, characterized in that: The image processing device is used to obtain a frequency spectrum according to the echo time sequence, and obtaining the third imaging according to the frequency spectrum includes: The image processing device is used to obtain a frequency spectrum according to an echo time series, and obtain the direction of the target according to a peak frequency included in the frequency spectrum. The amplitude corresponding to the peak frequency in the frequency spectrum reflects the echo intensity.

9. The three-dimensional imaging laser radar according to claim 8, characterized in that: The image processing device is used to obtain a frequency spectrum according to the echo time sequence, and obtaining the third imaging according to the frequency spectrum includes: The image processing device is used to obtain the echo time series based on the light intensity data and arrival time recorded by the pixel when the target is in multiple orientations during the movement of the target relative to the three-dimensional imaging lidar, so as to obtain the spectrum based on the echo time series.

10. The three-dimensional imaging laser radar according to claim 1, characterized in that: The telescopic optical system has a larger aperture in the first dimension than in the second dimension.

Images