CN111751828A - lidar system - Google Patents

Abstract

The invention relates to a laser radar system, which comprises a light source module, a receiving lens, a detection module and a processing module, wherein the light source module is used for receiving light; the light source module emits a laser beam; irradiating the laser beam to an object to be detected, and reflecting the laser beam by the object to be detected to form a reflected beam; the receiving lens receives the reflected light beam; the detection module comprises a photosensitive unit with a preset area, is arranged on a focal plane of the receiving lens or between the receiving lens and the focal plane, and detects the intensity of the reflected light beam to obtain an echo energy signal; the detection module also reduces the difference between a detected first echo energy signal and a detected second echo energy signal, wherein the first echo energy signal is an echo energy signal of an object to be detected within a preset distance of the receiving lens, and the second echo energy signal is an echo energy signal of the object to be detected outside the preset distance of the receiving lens; the processing module is electrically connected with the detection module and is used for processing the echo energy signal to obtain target information of the object to be detected.

Description

lidar system

technical field

The present invention relates to the technical field of radar, in particular to a laser radar system.

Background technique

When lidar measures object information, the object to be measured is illuminated by laser light, and the reflected light carrying the object information is received by the receiving lens, and the detector is used to convert the optical signal into an electrical signal, which is read and recorded by a digital circuit.

The difference between the echo energy of the near object detected by the traditional lidar detector and the echo energy of the distant object is too large. When the echo energy of the distant object is detected, the echo energy of the detected near object is too large. The energy may have been saturated, or even the detector has been broken.

SUMMARY OF THE INVENTION

Based on this, it is necessary to provide a lidar system for the problem that the echo energy of a near object detected by a traditional lidar detector is too different from the echo energy of a distant object.

A lidar system, comprising:

A light source module for emitting a laser beam;

The laser beam is irradiated to the object to be measured, and the laser beam is reflected by the object to be measured to form a reflected beam;

a receiving lens for receiving the reflected light beam;

a detection module, comprising a photosensitive unit with a preset area, the detection module is arranged on the focal plane of the receiving lens or between the receiving lens and the focal plane, and is used for detecting the intensity of the reflected light beam, get the echo energy signal;

The detection module is also used to reduce the difference between the detected first echo energy signal and the second echo energy signal, and the first echo energy signal is the echo of the object to be measured located within the preset distance of the receiving lens. wave energy signal, the second echo energy signal is the echo energy signal of the object to be measured located outside the preset distance of the receiving lens;

The processing module is electrically connected to the detection module, and the processing module is used for processing the echo energy signal to obtain target information of the object to be measured.

In the above-mentioned lidar system, a detection module with a photosensitive unit with a preset area is arranged on the focal plane of the receiving lens or between the receiving lens and the focal plane, and the detection module can detect the object to be measured located outside the preset distance of the receiving lens. Most of the echo energy, that is, the second echo energy signal, the detection module can only detect a small part of the echo energy of the object to be tested located within the preset distance of the receiving lens, that is, the first echo energy signal, so it can reduce The difference between the detected first echo energy signal and the second echo energy signal is small, so that when the detection module can detect the echo energy of the distant object, that is, when the second echo energy signal can be detected, the detection module The echo energy of detecting nearby objects will not be saturated, which can prevent the detection module from being damaged.

其中，ω为所述接收镜头的视场角，f为所述接收镜头的等效焦距。In one embodiment, the preset area is

Wherein, ω is the field angle of the receiving lens, and f is the equivalent focal length of the receiving lens.

In one embodiment, the target information includes reflectivity, distance, position, speed, attitude and shape of the object to be measured.

In one embodiment, the light source module includes:

lasers for emitting laser beams; and

The lens unit is arranged on the optical path of the laser beam, and is used for shaping and collimating the laser beam.

In one embodiment, the receiving lens is further used for converging and shaping the reflected light beam, so that the spot size of the reflected light beam is adapted to the photosensitive unit of the preset area of the detection module.

In one embodiment, the receiving lens includes a converging mirror and a shaping mirror, the converging mirror is used for converging the reflected light beam, and the shaping mirror is used for shaping the converged reflected light beam respectively.

In one embodiment, the detection module is one of an avalanche photodiode, a charge coupled element, a complementary metal oxide semiconductor and a multi-pixel photon counter.

In one embodiment, the detection module includes a filter, and the filter is used for filtering the echo energy signal, and transmitting the filtered echo energy signal to the processing module.

In one of the embodiments, the receiving lens comprises a single lens or a cemented lens or a lens group.

In one of the embodiments, the single lens, the cemented lens and/or the lens group are made of metamaterials.

Description of drawings

FIG. 1 is a schematic structural diagram of a lidar system in an embodiment provided by this application;

FIG. 2 is a schematic structural diagram of a lidar system in an embodiment provided by the present application;

3 is a schematic structural diagram of a lidar system in an embodiment provided by the present application;

4 is a schematic diagram of the positions of a first object to be measured, a second object to be measured, a receiving lens, and a detection module in an embodiment provided by the present application.

Detailed ways

In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the related drawings. The preferred embodiments of the present application are shown in the accompanying drawings. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the disclosure of this application is provided.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used herein in the specification of the present application are for the purpose of describing particular embodiments only, and are not intended to limit the present application.

When the laser sensor emits a narrow beam to the scattering object, the spot area of the beam irradiated on the scattering object can be approximated by the following formula:

Among them, A _taser is the spot area, R is the laser detection distance, that is, the distance between the lidar system and the object to be measured, and β _t is the beam width, which corresponds to the divergence angle of the laser.

Therefore, the energy density of the laser beam irradiated on the scattered objects is:

Among them, S _s is the energy density of the laser beam irradiated on the scattered objects, and P _t is the laser emission energy.

Since the wavelength of the laser is generally much smaller than the size of the scattering object, the effective area irradiated on the object can be simplified as the projected area of the scattering object. Part of the energy projected to the scattering object is absorbed, and the rest is scattered in all directions. The energy is:

Among them, P _s is the scattering energy, ρ is the reflectivity, and A _s is the irradiated area of the scattering objects.

Assuming that the incident laser light is uniformly scattered into a cone with a solid angle of Ω, if the receiver can receive energy, the energy density S _r received by the receiver is:

The energy _Pr entering the receiver is:

where _Dr is the receiver optical aperture.

近似于1时，落在接收器上的能量可以近似为：In traditional lidar systems, the receiving field of view is generally greater than or equal to the transmitting field of view.

When approximated to 1, the energy falling on the receiver can be approximated as:

It can be determined from the above formula that, for a fixed lidar system, the transmitting power of the laser remains unchanged and the aperture of the receiving lens remains unchanged. If the object to be tested with the same reflectivity is measured, the energy detected by the detector is squared with R inverse relationship. For example, objects with the same reflectivity are located at 0.1m (meters) and 100m, respectively. The echo energy of the object located at 0.1m detected by the detector is 10 ⁶ times the echo energy of the object located at 100m detected by the detector. Therefore, , when the detector can detect the echo energy of the distant object to be measured, the echo energy of the near object to be measured detected by the detector may have reached saturation, or even the detector may have been damaged. The receiving device includes a receiving lens and a detector.

Referring to FIG. 1 , an embodiment of the present application provides a lidar system, including a light source module 10 , a receiving lens 20 , a detection module 30 , and a processing module 40 . The light source module 10 is used for emitting laser beams. The laser beams are respectively irradiated to the object to be measured 100 , and the laser beams are reflected by the object to be measured 100 to form a reflected beam. The receiving lens 20 is used to receive the reflected light beam. The detection module 30 includes a photosensitive unit with a preset area, and the detection module 30 is arranged on the focal plane of the receiving lens 20 or between the receiving lens 20 and the focal plane, and is used to detect the intensity of the reflected beam to obtain an echo energy signal . The detection module 30 is further configured to reduce the difference between the detected first echo energy signal and the second echo energy signal, where the first echo energy signal is the echo of the object to be tested 100 located within a preset distance of the receiving lens 20 The energy signal, the second echo energy signal is the echo energy signal of the object to be measured 100 located outside the preset distance of the receiving lens 20 . The processing module 40 is electrically connected to the detection module 30 , and the processing module 40 is used for processing the echo energy signal to obtain target information of the object to be measured 100 .

The object to be measured 100 includes a first object to be measured 101 and a second object to be measured 102 . All the objects to be measured 100 located within the preset distance of the receiving lens 20 are the first objects to be measured 101 , and all the objects to be measured 100 located outside the preset distance of the receiving lens 20 are the second objects to be measured 102 .

因此，将具有预设面积的感光单元的探测模块30设置于接收镜头20的焦平面上或接收镜头20与焦平面之间，探测模块30能够探测到由第二待测物体102反射的大部分回波能量，即第二回波能量信号，探测模块30只能探测到由第一待测物体101反射的小部分回波能量，即第一回波能量信号，因而能够减小探测模块30探测到的第一回波能量信号与第二回波能量信号的差异，从而当探测模块30能够探测到远处物体的回波能量时，即能够探测到第二回波能量信号时，探测模块30探测到近处物体的回波能量不至于饱和，能够防止探测模块30被打坏。Within the field of view of the receiving lens 20, as the object to be measured 100 gradually moves away from the receiving lens 20, the image plane of the object to be measured 100 gradually approaches the focal plane from the far side, and the size of the image gradually decreases. When the image is located in the focal plane of the receiving lens 20, the size of the image of the object to be measured 100 is

Therefore, if the detection module 30 having a photosensitive unit with a preset area is disposed on the focal plane of the receiving lens 20 or between the receiving lens 20 and the focal plane, the detection module 30 can detect most of the reflections from the second object to be detected 102 The echo energy, that is, the second echo energy signal, the detection module 30 can only detect a small part of the echo energy reflected by the first object to be tested 101, that is, the first echo energy signal, so the detection module 30 can reduce the detection rate. The difference between the obtained first echo energy signal and the second echo energy signal, so that when the detection module 30 can detect the echo energy of the distant object, that is, when the second echo energy signal can be detected, the detection module 30 The echo energy of detecting a nearby object will not be saturated, which can prevent the detection module 30 from being damaged.

Referring to FIG. 2 , in one embodiment, the light source module 10 includes a laser 11 and a lens unit 12 . The laser 11 is used to emit a laser beam. The lens unit 12 is arranged on the optical path of the laser beam, and is used for shaping and collimating the laser beam. The lens unit 12 may be a lens assembly, a single lens with a single aperture, a lens group, a plurality of cylindrical mirrors, a plurality of spherical mirrors, or the like. Since the laser beam emitted by the laser 11 may be relatively divergent, the space shaping by the lens unit 12 can achieve the effect of efficient collimation and shaping. Thus, the lens unit 12 projects the shaped and collimated laser beam onto the object to be measured 100 .

In one of the embodiments, the receiving lens 20 is further used for converging and shaping the reflected light beam, so that the spot size of the reflected light beam is adapted to the photosensitive unit of the preset area of the detection module 30 .

Referring to FIG. 3 , in one embodiment, the receiving lens 20 includes a converging mirror 21 and a shaping mirror 22 . The converging mirror 21 is used for converging the reflected light beams, and the shaping mirrors 22 are used for shaping the converged reflected light beams respectively. In this embodiment, the converging mirror 21 converges the reflected light beam, and the converged reflected light beam is shaped by the shaping mirror 22, so that the spot size of the reflected light beam is adapted to the photosensitive unit of the preset area of the detection module 30, and the reflected light beam is approximately a plane wave In the form of irradiating directly on the photosensitive unit of the detection module 30, the difference of the pixel points caused by the difference of the detection area and the different illumination is eliminated, so as to improve the imaging quality.

In one embodiment, the receiving lens 20 includes a single lens for receiving the reflected light beam, and the reflected light beam enters the detection module 30 after passing through the single lens. Alternatively, the receiving lens 20 includes a cemented lens for receiving the reflected light beam, and the reflected light beam enters the detection module 30 through the cemented lens. Alternatively, the receiving lens 20 includes a lens group, the lens group includes a plurality of lenses, and the plurality of lenses are sequentially arranged on the optical path of the reflected beam transmission in a preset order for receiving the reflected beam, and the reflected beam enters the detection module 30 through the lens group. Single lenses, cemented lenses and/or lens groups can be made of metamaterials. Any combination of single lenses, cemented lenses, and lens groups is possible.

其中，ω为接收镜头20的视场角，f为接收镜头20的等效焦距，待测物体100在接收镜头20的焦平面处的像的大小为

因此，探测模块30的感光单元面积为

且设置于接收镜头20的焦平面，探测模块30能够探测到成像于该焦平面处的待测物体100的全部回光能量，能够减小探测模块30探测到的第一回波能量信号与第二回波能量信号的差异，而且探测模块30的感光单元面积设置为

可以使得探测模块30的感光单元具有较高的利用率，不至于造成浪费。In one of the embodiments, the preset area is

Among them, ω is the field of view of the receiving lens 20, f is the equivalent focal length of the receiving lens 20, and the size of the image of the object to be measured 100 at the focal plane of the receiving lens 20 is

Therefore, the area of the photosensitive unit of the detection module 30 is

And set at the focal plane of the receiving lens 20, the detection module 30 can detect all the echo energy of the object to be tested 100 imaged at the focal plane, and can reduce the first echo energy signal detected by the detection module 30 and the second echo energy signal. The difference between the two echo energy signals, and the area of the photosensitive unit of the detection module 30 is set to

This can make the photosensitive unit of the detection module 30 have a higher utilization rate, so as not to cause waste.

当将感光单元的面积大于或等于

的探测模块30设置于接收镜头20的焦平面，探测模块30能够探测到由第二待测物体102反射的全部回波能量，只能探测到由第一待测物体101反射的小部分回波能量，从而能够减小探测模块30探测到的第一回波能量信号与第二回波能量信号的差异。当将感光单元的面积大于或等于

的探测模块30设置于接收镜头20与接收镜头20的焦平面之间，探测模块30能够探测到由第二待测物体102反射的大部分回波能量，只能探测到由第一待测物体101反射的小部分回波能量，从而能够减小探测模块30探测到的第一回波能量信号与第二回波能量信号的差异。Please refer to FIG. 4 . In FIG. 4 , the first object to be measured 101 is located within the preset distance of the receiving lens 20 , that is, the second object to be measured 102 is located outside the preset distance of the receiving lens 20 relative to the near object of the receiving lens 20 . , that is, relative to the distant object of the receiving lens 20 , a near object forms a first real image 201 through the receiving lens 20 , and a distant object forms a second real image 202 through the receiving lens 20 . Within the field of view of the receiving lens 20, as the object to be measured 100 gradually moves away from the receiving lens 20, the image plane of the object to be measured 100 gradually approaches the focal plane from the far side, and the size of the image gradually decreases. A real image 201 and a second real image 202. The second real image 202 is located at the focal plane of the receiving lens 20 and the size of the second real image 202 is

When the area of the photosensitive unit is greater than or equal to

The detection module 30 is arranged on the focal plane of the receiving lens 20. The detection module 30 can detect all the echo energy reflected by the second object to be measured 102, and can only detect a small part of the echo reflected by the first object to be measured 101. energy, so that the difference between the first echo energy signal and the second echo energy signal detected by the detection module 30 can be reduced. When the area of the photosensitive unit is greater than or equal to

The detection module 30 is arranged between the receiving lens 20 and the focal plane of the receiving lens 20. The detection module 30 can detect most of the echo energy reflected by the second object to be measured 102, and can only detect the energy of the first object to be measured. A small part of the echo energy reflected by 101 can reduce the difference between the first echo energy signal and the second echo energy signal detected by the detection module 30 .

In one of the embodiments, the detection module 30 includes a filter, and the filter is used for filtering the echo energy signal and transmitting the filtered echo energy signal to the processing module 40 . It can be understood that the echo energy signal output by the detection module 30 contains the DC component of the common mode and the noise signal, so it is necessary to filter the echo energy signal through a filter to eliminate the common mode in the echo energy signal. DC components and high-frequency signals to improve the signal-to-noise ratio of the echo energy signal.

In one of the embodiments, the filter is a passive filter. It can be understood that a passive filter, also known as an LC filter, is a filter circuit composed of a combination of inductance, capacitance and resistance, which can filter out one or more harmonics, and has the advantages of simple structure, low cost, and reliable operation. Therefore, the passive filter is adopted in this embodiment, which is beneficial to simplify the structural design of the lidar system and reduce the production cost. It can be understood that the filter may also be an active filter, and the type of the filter is not limited in this embodiment.

The detection module 30 may be one of an avalanche photodiode, a charge coupled element, a complementary metal oxide semiconductor, and a multi-pixel photon counter. Avalanche photodiodes can amplify the echo energy signal to improve detection sensitivity. Charge-coupled devices, avalanche photodiodes, and CMOS sensors all have the ability to convert optical signals into electrical signals, so CCDs, avalanche photodiodes, and CMOS sensors can be used as detectors to convert reflected light beams into the echo energy signal. In addition, other devices having the function of converting optical signals into electrical signals can also be used as the detection module 30 , and the present invention does not specifically limit the implementation of the detection module 30 .

The target information includes the reflectivity, distance, position, speed, attitude and shape of the object to be measured 100 . The processing module 40 can convert the echo energy signal into a digital signal, and then calculate the target information of the object to be measured 100 , so as to detect, track and identify the object to be measured 100 . In one embodiment, the processing module 40 may be a micro-control unit or a computer or the like.

In the lidar system provided by the above embodiment, the detection module with a photosensitive unit with a preset area is arranged on the focal plane of the receiving lens or between the receiving lens and the focal plane, and the detection module can detect the detection module located outside the preset distance of the receiving lens. Most of the echo energy of the object to be measured, namely the second echo energy signal, the detection module can only detect a small part of the echo energy of the object to be measured located within the preset distance of the receiving lens, namely the first echo energy signal, Therefore, the difference between the detected first echo energy signal and the second echo energy signal can be reduced, so that when the detection module can detect the echo energy of the distant object, that is, when the second echo energy signal can be detected , the echo energy detected by the detection module of the nearby object will not be saturated, which can prevent the detection module from being damaged.

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are more specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims (10)

1. a lidar system, is characterized in that, comprises: A light source module for emitting a laser beam; The laser beam is irradiated to the object to be measured, and the laser beam is reflected by the object to be measured to form a reflected beam; a receiving lens for receiving the reflected light beam; a detection module, comprising a photosensitive unit with a preset area, the detection module is arranged on the focal plane of the receiving lens or between the receiving lens and the focal plane, and is used for detecting the intensity of the reflected light beam, get the echo energy signal; The detection module is also used to reduce the difference between the detected first echo energy signal and the second echo energy signal, and the first echo energy signal is the echo of the object to be measured located within the preset distance of the receiving lens. wave energy signal, the second echo energy signal is the echo energy signal of the object to be measured located outside the preset distance of the receiving lens; The processing module is electrically connected to the detection module, and the processing module is used for processing the echo energy signal to obtain target information of the object to be measured. 2. The lidar system according to claim 1, wherein the preset area is

Wherein, ω is the field angle of the receiving lens, and f is the equivalent focal length of the receiving lens. 3 . The lidar system according to claim 1 , wherein the target information includes reflectivity, distance, position, speed, attitude and shape of the object to be measured. 4 . 4. The lidar system according to claim 1, wherein the light source module comprises: lasers for emitting laser beams; and The lens unit is arranged on the optical path of the laser beam, and is used for shaping and collimating the laser beam. 5 . The lidar system according to claim 1 , wherein the receiving lens is further used for converging and shaping the reflected light beams, so that the spot size of the reflected light beams can be adapted to the size of the detection module. 6 . A photosensitive unit with a preset area. 6 . The lidar system according to claim 5 , wherein the receiving lens comprises a converging mirror and a shaping mirror, the converging mirror is used to condense the reflected light beam, and the shaping mirror is used to respectively The reflected beam is shaped. 7 . The lidar system according to claim 1 , wherein the detection module is one of an avalanche photodiode, a charge-coupled element, a complementary metal oxide semiconductor, and a multi-pixel photon counter. 8 . 8 . The lidar system according to claim 1 , wherein the detection module comprises a filter, and the filter is used for filtering the echo energy signal and filtering the echo energy signal after filtering. 9 . The energy signal is transmitted to the processing module. 9 . The lidar system according to claim 1 , wherein the receiving lens comprises a single lens or a cemented lens or a lens group. 10 . 10 . The lidar system according to claim 9 , wherein the single lens, the cemented lens and/or the lens group are made of metamaterials. 11 .

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