A laser radar transceiver

Abstract

The present invention provides a transceiver for a laser radar, comprising a transmitting waveguide, a receiver, and a transceiver multiplexer. The receiver comprises a free diffraction zone, a first receiving waveguide, a second receiving waveguide, a coupler, and a third receiving waveguide. One side of the free diffraction zone receives the light beam received by the transceiver multiplexer, and the outlets on the other opposite side are respectively connected to the first receiving waveguide and the second receiving waveguide. The width of the free diffraction zone is at least greater than the sum of the widths of the first receiving waveguide and the second receiving waveguide. The coupler comprises three ports, wherein the first port and the second port are located on the same side and are respectively connected to the first receiving waveguide and the second receiving waveguide, and the third port is located on the other opposite side and is connected to the third receiving waveguide. This solves the contradiction between the scanning speed of a frequency modulated continuous wave laser radar and the light receiving efficiency of the system, greatly extending the scanning speed or detection range of the frequency modulated continuous wave laser radar.

Description

Technical Field

[0001] The present invention relates to optical sensing technology, and in particular to a transceiver of a laser radar. Background Art

[0002] In a frequency-modulated continuous-wave lidar (FMCW) for long-distance ranging, the beam transceiver typically consists of three parts: a transmitter, a receiver, and a transceiver multiplexer. To complete the laser radar's beam scanning function, a rotating mirror or other means is often required to quickly synchronize the beam emitted by the transmitter and the beam received by the receiver. Due to the long ranging range, the return light often has a certain degree of delay. By the time the return light reaches the receiving system, the direction of the receiving device has changed, resulting in the received beam being unable to accurately return to the center of the receiving waveguide (or optical fiber). This causes a certain offset. The offset is related to the scanning angular velocity and the distance to the reflecting object. The faster the scanning speed and the farther the distance to the reflecting object, the greater the offset. Furthermore, the offset of the return light center relative to the center of the receiving waveguide will reduce the waveguide's efficiency in receiving the return light, reducing the overall light receiving efficiency of the system.

[0003] To solve the above problem, patent US11024669B2 minimizes the offset caused by the fast-rotating mirror scanning by placing the fast-rotating mirror at the internal image point. However, this prior art sacrifices the scanning speed of the emitted light beam and does not actually solve the problem in essence.

[0004] Another method that is easier to think of is to widen the size of the receiving waveguide, such as Figure 1 As shown in the figure, due to the larger fundamental mode field of the receiving waveguide, the drop in receiving efficiency is smaller for the same offset of the received beam, which can alleviate the problem of reduced scanning efficiency caused by return light deviation to a certain extent. However, this method of increasing the offset tolerance by widening the receiving waveguide mode field comes at the expense of reduced optimal coupling efficiency. Furthermore, since the farther the reflecting object is, the smaller the return light power is, the greater the offset is, and the greater the drop in receiving efficiency caused by the offset is. The combined effect of these two factors leads to a sharp deterioration in the system's light collection efficiency for distant return light. Summary of the Invention

[0005] In response to the above problems, the present invention provides a laser radar transceiver, which effectively solves the technical problem that the efficiency of existing laser radars deteriorates sharply with target distance.

[0006] The technical solutions provided by the present invention are as follows:

[0007] A laser radar transceiver device includes a transmitting waveguide, a receiver, and a transceiver multiplexer. The transmitting waveguide and the receiver are respectively connected to the transceiver multiplexer. The light beam generated by the transmitting waveguide is emitted through the transceiver multiplexer, and after being transmitted by an external object, it returns to the entrance of the receiver through the transceiver multiplexer.

[0008] The receiver includes: a free diffraction zone, a first receiving waveguide, a second receiving waveguide, a coupler and a third receiving waveguide, wherein:

[0009] One side of the free diffraction zone receives the light beam received by the transceiver multiplexer, and the outlet on the other opposite side is connected to the first receiving waveguide and the second receiving waveguide respectively, and the width of the free diffraction zone is at least greater than the sum of the widths of the first receiving waveguide and the second receiving waveguide;

[0010] The coupler includes three ports, wherein the first port and the second port are located on the same side and are connected to the first receiving waveguide and the second receiving waveguide respectively, and the third port is located on the other opposite side and is connected to the third receiving waveguide.

[0011] The transceiver device of the laser radar provided by the present invention utilizes a configuration of first and second receiving waveguides offset from the center, along with a free diffraction zone, to ensure that the maximum return light intensity and the maximum receiving efficiency occur at different locations. This flattens the overall receiving efficiency curve of the system, ensuring relatively high system receiving efficiency across the entire target distance range. This avoids the technical problem of a sharp deterioration in system efficiency with target distance in prior art. This resolves the conflict between the scanning speed of a frequency-modulated continuous-wave laser radar and the system's light-receiving efficiency, significantly extending the scanning speed or detection range of a frequency-modulated continuous-wave laser radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The preferred implementation scheme will be described below in a clear and understandable manner with reference to the accompanying drawings to further illustrate the above characteristics, technical features, advantages and their implementation methods.

[0013] Figure 1 A transceiver device for a laser radar with a widened receiving waveguide in the prior art;

[0014] Figure 2 Schematic diagram of the structure of the transceiver of the laser radar in the present invention;

[0015] Figure 3 Schematic diagram of the working principle of the transceiver device of the laser radar in the present invention;

[0016] Figure 4 This is a schematic structural diagram of an example of a transceiver device of a laser radar in the present invention;

[0017] Figure 5Schematic diagram of another example structure of the transceiver device of the laser radar in the present invention;

[0018] Figure 6 Schematic diagram of the received beam offset when the scanning speed of the transceiver device of the laser radar of the present invention is positive, negative and zero respectively;

[0019] Figure 7 For example Figure 1 The prior art and the present invention are shown as follows Figure 2 The comparison chart of the laser radar's transceiver's return light intensity, receiver's receiving efficiency, and the system's overall receiving efficiency is shown;

[0020] Figure 8 Graph showing simulation results of the relationship between light return intensity, system efficiency, and reflection distance in an example of the present invention.

[0021] Reference numerals:

[0022] 1-transmitting waveguide, 2-receiver, 2.1-free diffraction zone, 2.2-first receiving waveguide, 2.3-second receiving waveguide, 2.4-coupler, 2.4.1-first port, 2.4.2-second port, 2.4.3-third port, 2.5-third receiving waveguide, 2.6-cascaded direct coupler, 2.7-Y-coupler, 3-transceiver multiplexer. DETAILED DESCRIPTION

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings and other embodiments can be obtained based on these drawings without inventive work.

[0024] The laser radar transceiver of the present invention is as follows: Figure 2As shown, it includes a transmitting waveguide 1, a receiver 2 and a transceiver multiplexer 3. The transmitting waveguide 1 and the receiver 2 are respectively connected to the transceiver multiplexer 3. The light beam generated by the transmitting waveguide 1 is emitted through the transceiver multiplexer 3, and after being transmitted by an external object, it returns to the entrance of the receiver 2 through the transceiver multiplexer 3. The receiver 2 includes: a free diffraction zone 2.1, a first receiving waveguide 2.2, a second receiving waveguide 2.3, a coupler 2.4, and a third receiving waveguide 2.5. One side of the free diffraction zone 2.1 receives the light beam received by the transceiver multiplexer 3, and the outlet on the other opposite side is connected to the first receiving waveguide 2.2 and the second receiving waveguide 2.3, respectively. The width of the free diffraction zone 2.1 is at least greater than the sum of the widths of the first receiving waveguide 2.2 and the second receiving waveguide 2.3. The coupler 2.4 includes three ports, a first port 2.4.1 and a second port 2.4.2 are located on the same side and are connected to the first receiving waveguide 2.2 and the second receiving waveguide 2.3, respectively. The third port 2.4.3 is located on the other opposite side and is connected to the third receiving waveguide 2.5.

[0025] In this embodiment, the transmitting waveguide 1 guides the light received from the laser light source to generate a light beam. After passing through the transceiver multiplexer 3, the light beam is emitted into space to form a scanning light beam. After being reflected by the target object, the light beam returns to the entrance of the receiver 2 through the transceiver multiplexer 3. Figure 3 shown.

[0026] The transceiver multiplexer 3 can be a polarization multiplexer, a power multiplexer or an optical circulator, etc., which can be selected according to the actual application. The coupler 2.4 is preferably a 3dB coupler 2.4, a cascaded direct coupler 2.4 or a Y-type coupler 2.4. In the example where the coupler 2.4 is a cascaded direct coupler 2.6, the structural diagram is as shown in FIG. Figure 4 In the example where the coupler 2.4 is a Y-type coupler 2.7, the structural diagram is as shown. Figure 5 shown.

[0027] The first receiving waveguide 2.2 and / or the second receiving waveguide 2.3 in the receiver are arranged offset from the central axis of the free diffraction zone. The central axis represents the orientation of the first or second receiving waveguide. Preferably, they are arranged symmetrically along the central axis of the free diffraction zone 2.1. The widths of the free diffraction zone 2.1, the first receiving waveguide 2.2, and the second receiving waveguide 2.3 can also be configured based on actual conditions. To meet the requirements of the free diffraction zone 2.1, the width can be configured to be 2.5-2000 times the width of the first and second receiving waveguides 2.2, 2.3 (the width here specifically refers to the width of the first and second receiving waveguides 2.2, 2.3 in the width direction. The length direction of the first and second receiving waveguides 2.2, 2.3 is the direction from the exit of the free diffraction zone to the entrance of the coupler. This width direction of the free diffraction zone 2.1 is defined as the first width direction). For the transmitting waveguide 1, the materials for preparing the first receiving waveguide 2.2, the second receiving waveguide 2.3 and the third receiving waveguide 2.5 in the receiver 2 can also be selected according to actual conditions, as long as they can meet the purpose of this embodiment and realize guided light wave transmission.

[0028] The free diffraction zone is essentially a waveguide with a relatively wide width, and the width is sufficient to ensure that the light beam will not be reflected on the two side walls of the waveguide after diffracting in it (different from the aforementioned width, the width here refers to the width between the light beam entrance and exit of the free diffraction zone 2.1, which is defined here as the second width direction).

[0029] During this process, when the laser radar beam is pointed without scanning, the emitted beam can return to the center of the receiver after being reflected by the target object; when the laser beam is pointed to scan quickly and the object is far away, due to the time delay from emission to reception, when the target object reflects the beam back to the receiver, an offset will be generated, so that the received beam is no longer in the center of the receiver, and the degree of offset is proportional to the scanning speed and the distance to the target object, such as Figure 6 shown.

[0030] Under the premise of a certain scanning speed, the degree of deviation of the return light reaching the receiver is proportional to the target distance, while the intensity of the return light reaching the receiver entrance is inversely proportional to the square of the target distance. Figure 1 In the method shown in FIG, in which the receiver receives a light beam with a certain offset through a wide receiving waveguide, the receiver receiving efficiency is distributed as a Gaussian function with respect to the return light offset degree / target distance (maximum when the offset is 0). Since the return light intensity of the transmitted light beam reaching the receiver entrance is inversely proportional to the square of the target distance, the total receiving efficiency of the system is equal to the return light intensity multiplied by the efficiency of the receiver. Therefore, the receiving efficiency of the system will deteriorate sharply with the increase of the target distance, as shown in FIG. Figure 7 As shown in (a) in .

[0031] In this embodiment, when the received light beam reaches the receiver entrance, it will first diffuse freely for a distance in the free diffraction zone. At the same time, because the positions of the first receiving waveguide and the second receiving waveguide are offset from the center of the receiver, the optimal value of the receiver's receiving efficiency does not appear when the offset is 0, that is, when the target distance is 0, but there is an offset. This structure ensures that the maximum value of the receiver's return light intensity and the maximum value of the receiving efficiency do not occur at the same position, thereby flattening the overall receiving efficiency curve of the system, and achieving a relatively high system receiving efficiency across the entire range of the measured target distance. Figure 7 As shown in (b) in .

[0032] In one example, Figure 3 The laser radar transceiver is simulated, and the results are as follows Figure 8 As shown in the figure, when the reflection distance is between 1 and 250m, the return light intensity changes by 15dB (curve A), while the system receiving efficiency only changes by about 5dB (curve B). The simulation parameters are shown in the following table:

[0033] Parameter name Numerical First receiving waveguide width 26μm The second receiving waveguide width 26μm Length of the free diffraction zone (corresponding to the aforementioned first width direction) 200μm Beam wavelength 1.31μm The distance between the first receiving waveguide and the second receiving waveguide 20μm Emission spot size 7x7μm Received spot size 12x12μm

[0034] It should be noted that the above embodiments can be freely combined as needed. The above are only preferred embodiments of the present invention. It should be pointed out that ordinary relevant personnel in this technical field can make several improvements and modifications without departing from the principles of the present invention. Such improvements and modifications should also be considered as the scope of protection of the present invention.

Claims

1. A laser radar transceiver, characterized in that: The device comprises a transmitting waveguide, a receiver and a transceiver multiplexer, wherein the transmitting waveguide and the receiver are respectively connected to the transceiver multiplexer, and the light beam generated by the transmitting waveguide is emitted through the transceiver multiplexer, and after being emitted by an external object, it returns to the entrance of the receiver through the transceiver multiplexer; The receiver includes: a free diffraction zone, a first receiving waveguide, a second receiving waveguide, a coupler and a third receiving waveguide, wherein: One side of the free diffraction zone receives the light beam received by the transceiver multiplexer, and the outlet on the other opposite side is connected to the first receiving waveguide and the second receiving waveguide respectively, and the width of the free diffraction zone is at least greater than the sum of the widths of the first receiving waveguide and the second receiving waveguide; The coupler includes three ports, a first port and a second port are located on the same side and are connected to the first receiving waveguide and the second receiving waveguide respectively, and a third port is located on the other opposite side and is connected to the third receiving waveguide; The first receiving waveguide and / or the second receiving waveguide are arranged away from the central axis of the free diffraction zone, and the central axis is the arrangement direction of the first receiving waveguide or the second receiving waveguide; The first receiving waveguide and the second receiving waveguide are symmetrically arranged on both sides of the central axis of the free diffraction zone, and the central axis is the arrangement direction of the first receiving waveguide or the second receiving waveguide.

2. The transceiver according to claim 1, wherein: The coupler is a 3dB coupler.

3. The transceiver according to claim 1 or 2, wherein: The coupler is a cascade direct coupler or a Y-type coupler.

4. The transceiver according to claim 1, wherein: The transceiver multiplexer is a polarization multiplexer, a power multiplexer or an optical circulator.

5. The transceiver according to claim 1, 2 or 4, wherein: The width of the free diffraction zone is 2.5-2000 times the width of the first receiving waveguide and the second receiving waveguide.

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