A long-range measuring laser radar optical system

Abstract

The application discloses a laser radar optical system for wide-range measurement, wherein main and auxiliary laser emitting diodes are installed in a transmitting system, the main and auxiliary laser emitting diodes are cyclically switched through an electronic control circuit to meet the ranging of objects at different distances. Meanwhile, a cylindrical compensation area is added at a receiving lens to compensate for the offset error caused by an optical cover, so that more light received by the receiving lens is on the laser receiver, and the final measurement is more accurate while the measurement range is enlarged.

Description

Technical Field

[0001] This invention relates to the field of laser measurement technology, and more specifically to a lidar optical system for large-scale measurement. Background Technology

[0002] LiDAR mainly includes pulsed LiDAR, phase-detection LiDAR, and triangulation LiDAR. Pulsed LiDAR includes a laser transmitter and receiver module and is primarily used for medium- to long-range laser ranging. The process of pulsed laser ranging is as follows: the laser emitted by the rangefinder is reflected by the object being measured and then received by the rangefinder. The rangefinder simultaneously records the round-trip time of the laser. Half the product of the speed of light and the round-trip time is the distance between the rangefinder and the object being measured. This distance information is then transmitted to an electronic chip for processing. The electronic software controls the radar to perform the next operation based on the received signal.

[0003] LiDAR products have many inherent limitations. For example, a LiDAR with excellent long-range measurement capabilities may have significant errors when measuring close-range objects, while a LiDAR with excellent close-range measurement capabilities may not be able to measure distant objects. The measurable distance of a LiDAR is related to the design of its optical system; conventional optical systems cannot simultaneously meet the requirements for both close-range and long-range ranging.

[0004] Currently, a single LiDAR on the market cannot simultaneously measure objects at both near and far distances. To achieve both near and far distance measurements, multiple LiDARs are often required in combination, which results in higher product costs and larger size.

[0005] Therefore, how to expand the measurement range of lidar, reduce the size of the equipment, and lower the equipment cost are problems that urgently need to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a lidar optical system for large-range measurement. A primary and secondary laser emitting diode are installed in the transmitting system, and the primary and secondary laser emitting diodes are switched cyclically by electronic control to meet the requirements of both near and far distance measurements. Simultaneously, a cylindrical compensation lens is cemented and added at the receiving lens as a cylindrical compensation area to compensate for the deflection distance of the receiving optical path during near-range measurements. This ensures that more light received by the receiving lens hits the laser receiver, expanding the measurement range and making the final measurement more accurate. Therefore, lidar equipped with this optical system can achieve large-range measurements at both near and far distances.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A lidar optical system for wide-range measurement includes a laser emitting optical system, a laser receiving optical system, an optical housing, and an electronic control board;

[0009] The laser emitting optical system and the laser receiving optical system are housed inside the optical housing and are both electrically connected to the electronic control board;

[0010] The laser emitting system includes a primary and a secondary laser emitting diode; the laser receiving system is provided with a cylindrical compensation area; the primary and secondary laser emitting diodes are electrically connected to the electronic control board.

[0011] The technical effects of the above-described solution are as follows: the laser emitting optical system and the laser receiving optical system are mainly used to measure the distance to the object being measured. They emit light signals to the object and receive the reflected light signals. The electronic control board controls the cyclic switching of the primary and secondary laser emitting diodes, collecting reflected light signals from the object that are suitable for the distance measurement of the primary and secondary laser emitting diodes, and calculating the measured distance based on these reflected light signals. The laser emitting system, with its primary and secondary light sources, enables a single system to simultaneously measure both distant and near objects. However, this also means that at least one light source is off-axis; therefore, the receiving system determines the location of the cylindrical compensation area based on the actual system requirements.

[0012] Preferably, the laser receiving optical system further includes a receiving lens and a laser receiver. The laser reflected by the object being measured passes sequentially through the optical housing, the receiving lens, and the cylindrical compensation area, and is received by the laser receiver, which is electrically connected to the electronic control board. The cylindrical compensation area is located on the upper part of one side of the receiving lens, and a mirror compensation lens is cemented onto the receiving lens to serve as the cylindrical compensation area.

[0013] Preferably, the main and auxiliary laser emitting diodes include a main laser emitting diode and an auxiliary laser emitting diode; the laser emitting system also includes an emitting lens, through which the main laser emitting diode and the auxiliary laser emitting diode emit laser light; the main laser emitting diode and the auxiliary laser emitting diode are arranged side by side, with the main laser emitting diode facing the optical axis of the emitting lens, and the auxiliary laser emitting diode located on the side of the optical axis of the emitting lens away from the receiving system; the auxiliary laser emitting diode is not on the optical axis of the emitting lens, but is placed at the end away from the receiving system, so that the emitted laser light at close range can be successfully reflected by the object being measured and hit the laser receiver, meeting the measurement requirements within 1 meter;

[0014] The technical effect of the above technical solution is that when the laser radar is used for close-range measurement, because the object being measured is close and the divergence angle of the light source is fixed, the reflected laser light path will shift away from the laser receiver. When the laser receiver is fixed, the use of a secondary laser emitting diode that is far away from the receiving lens can ensure that the downward-shifted receiving laser light path hits the laser receiver.

[0015] When the laser radar is used for long-distance measurement, because the object being measured is far away and the divergence angle of the light source is fixed, the reflected laser light path will be deflected towards the direction of the laser light source. At the same time, the presence of the optical cover will also cause the receiving laser light path to be deflected towards the direction of the laser light source, and the laser receiver will be deflected towards the direction of the laser light source. The cylindrical compensation area is mainly used to compensate for the optical path deflected at close range, ensuring that the receiving laser light path hits the laser receiver.

[0016] For long-distance measurements of 1 meter or more, a main laser emitting diode is used; for short-distance measurements of less than 1 meter, a secondary laser emitting diode is used.

[0017] Preferably, the electronic control board controls the automatic cyclic switching of illuminating the main laser emitting diode and the secondary laser emitting diode. The laser receiver of the laser receiving optical system receives the reflected light signal and, according to a preset signal intensity range, filters out the effective light signal from the reflected light signal, transmitting it to an external device for distance calculation. This makes the final detection result more accurate and expands the range of measurement distances. When the main laser emitting diode emits a light signal that illuminates a nearby object, the returned light signal intensity is strong, exceeding the preset signal intensity range; when the secondary laser emitting diode emits a light signal that illuminates a distant object, the returned light signal intensity is weak, and the received light signal is less than the preset signal intensity range. The reflected light signal filtered according to the preset signal intensity range basically meets the design requirements of using the main laser emitting diode for long-distance ranging and using the secondary laser emitting diode for short-distance ranging.

[0018] As can be seen from the above technical solution, compared with the prior art, this invention discloses a lidar optical system for large-range measurement. A main and secondary laser emitting diode are installed in the emission system. Electronic software cycles through the switching of the main and secondary laser emitting diodes, filtering out light signals that meet the signal strength range to satisfy the ranging needs of objects at different distances. The electronic control circuit controls the automatic cyclic switching of the main and secondary laser emitting diodes. The main laser emitting diode is mainly used for long-distance measurement; the secondary light source is not located at the center of the optical axis, enabling ranging of objects within 1 meter. To improve the ranging capability of the lidar, a defocused cylindrical compensation area is added to the receiving lens, achieved through a cemented cylindrical compensation lens. When measuring nearby objects, the light is deflected due to the incident angle. The cylindrical compensation area can change the angle of the light, ensuring that the received laser signal hits the laser receiver correctly. This allows the electronic control board to receive sufficient laser signal and then filter the received laser signal according to a preset signal strength range, selecting the effective light signal that meets the ranging range to complete the ranging. This makes the final detection result more accurate and expands the measurement distance range without increasing the size of the lidar. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 The attached figure is a schematic diagram of the overall structure of the large-area measurement lidar optical system provided by the present invention;

[0021] Figure 2 The attached figure is a schematic diagram of the optical path of the lidar transmitting system provided by the present invention;

[0022] Figure 3 The attached figure is a schematic diagram of the optical path of the lidar receiving system provided by the present invention;

[0023] Figure 4 The attached figure is a schematic diagram of the main and secondary laser emitting diode light source switching circuit of the lidar provided by the present invention.

[0024] In the attached diagram: 11-Main laser emitting diode, 12-Secondary laser emitting diode, 2-Emitting lens, 3-Optical housing, 4-Receiving lens, 5-Cylindrical compensation area, 6-Laser receiver. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention discloses a large-range measurement lidar optical system, including a laser emitting optical system and a laser receiving optical system installed within an optical housing. The laser emitting system includes a main laser emitting diode, a secondary laser emitting diode, and an emitting lens, with the main and secondary laser emitting diodes emitting laser light through the emitting lens. The laser receiving optical system includes a receiving lens, a defocused cylindrical compensation area, and a laser receiver arranged sequentially. The cylindrical compensation area is located on the receiving lens, using a cylindrical compensation lens cemented onto the receiving lens as the cylindrical compensation area. The laser light reflected from the object being measured passes sequentially through the optical housing, the receiving lens, and the cylindrical compensation area, and is received by the laser receiver. The main laser emitting diode, the secondary laser emitting diode, and the laser receiver are all electrically connected to an electronic control board. The electronic control board cyclically controls the activation of either the main or secondary laser emitting diode, thereby achieving long-range or short-range measurement.

[0027] The electronic control board cycles through the primary and secondary laser emitting diodes to complete the measurement of near and far distances; a defocused cylindrical compensation area is added to the receiving system so that more of the laser light received by the receiving lens hits the laser receiver, thereby enhancing the radar's receiving capability and enabling wide-range ranging.

[0028] like Figure 1 As shown, the main laser emitting diode 11, the secondary laser emitting diode 12, the emitting lens 2, the optical housing 3, the receiving lens 4, the cylindrical compensation lens 5, and the laser receiver 6 constitute the laser emitting system and the laser receiving system of the lidar. The laser receiver 6 has a built-in filter. The laser emitting diode and the laser receiver are connected to the electronic control board. The ranging process is as follows: the electronic control board sends a signal to the laser emitting diode through APC_GATE, and cyclically controls the main laser emitting diode and the secondary laser emitting diode to switch between emitting lasers. The laser light passes through the emitting lens, passes through the optical housing, and hits the object being measured. The object reflects the laser light, which passes through the optical housing, passes through the receiving lens, is compensated by the cylindrical compensation area, and hits the laser receiver. The electronic control board filters the reflected light signal received by the laser receiver according to the preset signal strength range. The reflected light signal carries the propagation time information and is sent to the external device to calculate the actual measured distance. The actual measured distance = the speed of light in air * the propagation time / 2. When the actual measurement distance is less than or equal to 1 meter, the reflected light signal of the light signal emitted by the secondary laser emitting diode is filtered and retained; otherwise, the reflected light signal of the light signal emitted by the primary laser emitting diode is filtered and retained.

[0029] like Figure 2As shown, the light source in the laser emission system includes a main laser emitting diode 11 and a secondary laser emitting diode 12. The main laser emitting diode 11 is located on the optical axis of the emitting lens 3 and is mainly used to measure distant objects beyond 1 meter. The secondary laser emitting diode 12 is located at the end away from the receiving lens and is not on the optical axis of the emitting lens 3. It is mainly used to measure nearby objects within 1 meter.

[0030] like Figure 3 As shown, in the laser receiving system, the reflected laser passes through the optical housing 3, then through the receiving lens 4, and finally through the cylindrical compensation area 5 to hit the laser receiver 6. The cylindrical compensation area 5 and the laser receiver 6 are located slightly closer to the emitting lens than the optical axis of the receiving lens.

[0031] like Figure 4 As shown, the electronic control circuit is set on the electronic control board. In the electronic control circuit, LASER_P1_EN and LASER_P2_EN are connected to the main laser emitting diode 11 and the auxiliary laser emitting diode 12, respectively. The electronic control circuit sends a signal to the laser emitting diode through APC_GATE according to the signal strength received by the software, and controls the switching of the main and auxiliary laser emitting diodes.

[0032] Method for determining the location of the cylindrical compensation area:

[0033] If the laser emitted by the laser emitting optical system is perpendicular to the target object, and the laser reflected from the target object forms a certain angle with the emitted laser, and is transmitted to the laser receiver through a receiving lens, with a minimum distance of approximately 100mm between the target object and the receiving lens, and let A be the vertical distance between the target object and the center of the optical axis of the receiving lens, and B be the distance between the center of the optical axis of the receiving lens and the laser receiver, then let x be the distance between the lower edge of the cylindrical compensation area and the center of the optical axis of the receiving lens when the excitation receiver receives the reflected laser. The calculation formula is as follows:

[0034] but

[0035] The dimensions near the outermost edge of the lens are mainly for lens assembly. There should be at least a 0.8-1mm margin between the compensation area and the edge for structural assembly.

[0036] However, the actual cylindrical compensation area in the design is appropriately expanded or reduced according to the actual energy received by the receiver. The final area will be adjusted according to the system energy. Influencing factors include the curvature of the receiving lens and the compensation area, the response energy of the laser receiver (APD), etc.

[0037] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0038] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A lidar optical system for large-area measurement, characterized in that, Includes a laser emitting optical system, a laser receiving optical system, an optical housing, and an electronic control board; The laser emitting optical system and the laser receiving optical system are housed inside the optical housing and are both electrically connected to the electronic control board; The laser emitting system includes a primary and a secondary laser emitting diode; the laser receiving system is provided with a cylindrical compensation area; the primary and secondary laser emitting diodes are electrically connected to the electronic control board; The laser receiving optical system also includes a receiving lens and a laser receiver. The laser reflected by the object being measured passes sequentially through the optical housing, the receiving lens, and the cylindrical compensation area, and is received by the laser receiver. The laser receiver is electrically connected to the electronic control board. The cylindrical compensation area is located on the upper part of one side of the receiving lens, and a mirror compensation lens is cemented onto the receiving lens to serve as the cylindrical compensation area. The main and auxiliary laser emitting diodes include a main laser emitting diode and an auxiliary laser emitting diode; the laser emitting system also includes an emitting lens, through which the main laser emitting diode and the auxiliary laser emitting diode emit laser light; the main laser emitting diode and the auxiliary laser emitting diode are arranged side by side, with the main laser emitting diode facing the optical axis of the emitting lens, and the auxiliary laser emitting diode located on the side of the optical axis of the emitting lens away from the receiving system; The electronic control board controls the automatic cyclic switching of lighting the main laser emitting diode and the auxiliary laser emitting diode. The laser receiver of the laser receiving optical system receives the reflected light signal and, according to a preset signal intensity range, filters out the effective light signal from the reflected light signal and transmits it to an external device for distance calculation.

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