Optical transceiver, frequency modulated continuous wave lidar and method of detection thereof

Abstract

The application provides an optical transceiver for a laser radar, comprising: a circulator crystal having a plurality of optical channels, each optical channel comprising at least a first port, a second port and a third port, the first port, the second port and the third port being configured to input or output a light beam in a preset manner; an optical transmission device comprising a plurality of groups of optical transmission units corresponding to the plurality of optical channels, each group of optical transmission units comprising a first optical transmission medium and a third optical transmission medium optically coupled to the first port and the third port, respectively; and a field of view adjusting unit arranged at the second port and configured to increase a field of view range of the light beam output from the second port. The optical transceiver of the application can realize a large field of view with a minimum core, thereby reducing the cost and assembly difficulty.

Description

Technical Field

[0001] This invention relates generally to the field of lidar, and more particularly to an optical transceiver device, a frequency-modulated continuous wave lidar, and a detection method thereof. Background Technology

[0002] A circulator is a non-reciprocal device commonly used in optical communication, meaning that a light beam can only be transmitted in a specific direction. For example... Figure 1 As shown, a circulator typically has three ports. A signal input from port 1 is output from port 2, and a signal input from port 2 is output from port 3. Applying it to an FMCW (Frequency Modulated Continuous Wave) lidar system enables coaxial transmission and reception. To increase the field of view of an FMCW lidar, multiple transceiver channels are required. Figure 2a This is a schematic diagram of an existing single-channel circulator package structure, including three ports and a core crystal. The price of the core crystal is proportional to its size, making it very expensive. For array circulators, the existing technology basically involves directly arraying a single circulator, such as... Figure 2b As shown, the shortcomings of existing technologies result in large size, inflexible control, and very high cost for lidar.

[0003] The content in the background section is merely technology known to the public and does not necessarily represent existing technology in this field. Summary of the Invention

[0004] In view of at least one deficiency of the prior art, the present invention provides an optical transceiver for lidar, comprising:

[0005] A circulator crystal having multiple optical channels, each optical channel including at least a first port, a second port and a third port, the first port, the second port and the third port being configured to input or output a light beam in a preset manner;

[0006] An optical transmission device comprising multiple sets of optical transmission units corresponding to the plurality of optical channels, each set of optical transmission units comprising a first optical transmission medium and a third optical transmission medium optically coupled to the first port and the third port, respectively; and

[0007] A field-of-view adjustment unit is provided at the second port and configured to increase the field of view of the beam output from the second port.

[0008] According to one aspect of the present invention, both the first optical transmission medium and the third optical transmission medium comprise optical fibers.

[0009] According to one aspect of the invention, the field-of-view adjustment unit includes a plurality of fourth ports and fifth ports corresponding to the plurality of optical channels, wherein each second port is close to and corresponds to one of the fourth ports, an optical path is formed between one of the fourth ports and a corresponding fifth port, and the spacing between the fifth ports is greater than the spacing between the fourth ports.

[0010] According to one aspect of the invention, each optical transmission unit further includes a second optical transmission medium optically coupled to the second port, the field-of-view adjustment unit includes at least a first clamp and a second clamp, each of the second optical transmission media is held by the first clamp and the second clamp and extends between one of the fourth ports and one of the fifth ports, wherein the first clamp is close to the circulator crystal, and the spacing of the second optical transmission media at the first clamp is smaller than the spacing of the second optical transmission media at the second clamp, the second optical transmission medium comprising an optical fiber.

[0011] According to one aspect of the present invention, the field-of-view adjustment unit includes a planar optical waveguide device having a fan-out structure, wherein the plurality of fourth ports are located on the side with a smaller size of the fan-out structure, and the fifth port is located on the side with a larger size of the fan-out structure.

[0012] According to one aspect of the invention, the circulator crystal comprises a first polarizing beam splitter, a Faraday rotator, a quarter-wave plate, and a second polarizing beam splitter arranged in sequence.

[0013] According to one aspect of the present invention, the optical transceiver further includes a first microlens array, a second microlens array, and a third microlens array, wherein the first microlens array includes a plurality of first collimating microlenses disposed between the first port and the first optical transmission medium, the second microlens array includes a plurality of second collimating microlenses disposed between the second port and the field-of-view adjustment unit, and the third microlens array includes a plurality of third collimating microlenses disposed between the third port and the third optical transmission medium.

[0014] The present invention also provides a frequency-modulated continuous wave lidar, including the optical transceiver device described above.

[0015] According to one aspect of the present invention, the frequency-modulated continuous wave lidar further includes a shaping lens and a scanner, wherein the light-emitting end face of the field-of-view adjustment unit is disposed at the focal plane of the shaping lens, and the scanner is configured to receive a light beam from the shaping lens and reflect it to the outside of the lidar for scanning, and / or receive a light beam from the outside and reflect it to the shaping lens.

[0016] According to one aspect of the present invention, the frequency-modulated continuous wave lidar further includes:

[0017] A laser, configured to emit a laser beam;

[0018] A first coupler is configured to receive the laser beam and split it into a local oscillator beam and a probe beam. The optical transceiver receives the probe beam through a first port and outputs it from a second port. The probe beam passes through the field-of-view adjustment unit and is emitted into the surrounding environment via the shaping lens and the scanner. The echo of the probe beam on the obstacle passes through the scanner and the shaping lens and is incident on the second port of the circulator crystal through the field-of-view adjustment unit, and is output from a third port.

[0019] A second coupler, configured to receive the local oscillator light and the echo and mix them to obtain a mixed signal; and

[0020] A processing unit configured to calculate the distance and velocity of the obstacle based on the mixing signal.

[0021] According to one aspect of the present invention, the probe light is incident on the first port of the optical transceiver through the first optical transmission medium, and the echo is emitted from the third port and then incident on the third optical transmission medium.

[0022] According to one aspect of the invention, the processing unit includes a filter configured to filter the mixing signal to remove stray light mixing signals obtained by mixing stray light with local oscillator light.

[0023] The present invention also provides a detection method for frequency-modulated continuous wave lidar, comprising:

[0024] S201: Emits a laser beam;

[0025] S202: Split the laser beam into a local oscillator beam and a probe beam;

[0026] S203: Receive the probe light through the first port of the optical transceiver device as described above and output it from the second port;

[0027] S204: The field of view of the probe light output from the second port is increased by the field of view adjustment unit of the optical transceiver;

[0028] S205: The probe light emitted from the field adjustment unit is emitted into the surrounding environment via the shaping lens and the scanner;

[0029] S206: The scanner and shaping lens cause the echo of the probe light on the obstacle to be incident on the second port of the circulator crystal through the field adjustment unit and output from the third port;

[0030] S207: Mix the local oscillator light with the echo to obtain a mixed signal; and

[0031] S208: Calculate the distance and speed of the obstacle based on the mixed signal.

[0032] The optical transceiver device of the present invention can achieve a large field of view with a minimal core, reducing cost and assembly difficulty. Attached Figure Description

[0033] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute an undue limitation of this disclosure. In the drawings:

[0034] Figure 1 A schematic diagram of the circulator's structure is shown;

[0035] Figure 2a A schematic diagram of an existing single-channel circulator package structure is shown;

[0036] Figure 2b A schematic diagram of circulator arraying is shown;

[0037] Figure 3 An optical transceiver apparatus according to an embodiment of the present invention is shown;

[0038] Figure 4 A schematic diagram showing the beam field of view with and without a field of view adjustment unit is provided.

[0039] Figure 5 A field-of-view adjustment unit according to a preferred embodiment of the present invention is shown;

[0040] Figure 6 A field-of-view adjustment unit according to another embodiment of the present invention is shown;

[0041] Figure 7 An optical transceiver apparatus according to a preferred embodiment of the present invention is shown;

[0042] Figure 8a and 8b This illustrates the working principle of a circulator crystal;

[0043] Figure 9 A frequency-modulated continuous wave lidar according to an embodiment of the present invention is shown;

[0044] Figure 10 It shows Figure 6 The frequency versus transmittance curves of the beat frequency signal obtained in the embodiment; and

[0045] Figure 11A detection method for a frequency-modulated continuous wave lidar according to an embodiment of the present invention is shown. Detailed Implementation

[0046] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0047] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0048] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0049] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0050] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0051] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0052] Figure 3 An optical transceiver 10 according to an embodiment of the present invention is shown, which can be used in lidar, such as FMCW lidar, and is described in detail below with reference to the accompanying drawings.

[0053] like Figure 3 As shown, the optical transceiver 10 includes a circulator crystal 11, an optical transmission device 12, and a field-of-view adjustment unit 13. The circulator crystal 11 has multiple optical channels, each optical channel including at least a first port, a second port, and a third port, the first port, the second port, and the third port being configured to input or output light beams according to a preset method. Figure 3 The diagram schematically shows that the circulator crystal 11 has eight optical channels, such as... Figure 3 The optical channels C1, C2, ..., C8 are shown. The first optical channel C1 has a first port P11, a second port P12, and a third port P13; the second optical channel C2 has a first port P21, a second port P22, and a third port P23, and so on for the other optical channels. According to one embodiment, the first port of each optical channel can be used for input beams, the second port can be used for both input and output beams, and the third port can be used for output beams. When an input beam is received, the optical channel of the circulator crystal will transmit in a specific direction; for example, a signal input from the first port will be output from the second port, and a light signal input from the second port will be output from the third port. This transmission is typically limited to multiple ports within the same optical channel; light signal transmission usually does not occur between different optical channels.

[0054] The optical transmission device 12 includes multiple sets of optical transmission units corresponding to the plurality of optical channels. Each set of optical transmission units includes a first optical transmission medium and a third optical transmission medium optically coupled to the first port and the third port, respectively. Figure 3 As shown, the optical transmission device 12 includes eight sets of transmission units 12-1, 12-2, ..., 12-8 corresponding to eight optical channels C1, C2, ..., C8. Taking the first set of transmission units 12-1 as an example, it includes a first optical transmission medium 12-11 and a third optical transmission medium 12-13. The first optical transmission medium 12-11 is optically coupled to the first port P11 of the first optical channel C1, and optical signals can be coupled into the first port P11 of the first optical channel C1 through the first optical transmission medium 12-11. The second optical transmission medium 12-13 is optically coupled to the third port P13 of the first optical channel C1, and optical signals coupled out from the third port P12 of the first optical channel C1 can be received through the third optical transmission medium 12-13. According to a preferred embodiment of the present invention, both the first optical transmission medium and the third optical transmission medium include optical fibers. The diameter and spacing of the optical fibers can be made very small, thus effectively reducing the size of the circulator crystal 11.

[0055] The field-of-view adjustment unit 13 is disposed adjacent to the circulator crystal 11 and at the second port of the circulator crystal 11, configured to increase the field of view of the light beam output from the second port. When an optical signal is input from the first port of the circulator crystal 11, the optical signal will be output from the second port. Because the circulator crystal 11 has a relatively compact structure, the field of view of the optical signals output from the multiple second ports P12, P22, ..., P82 is relatively small. This invention, by distributing the field-of-view adjustment unit 13 at the second port of the circulator crystal 11, can increase the field of view of the light beam output from the second port.

[0056] like Figure 3 As shown, the field-of-view adjustment unit 13 includes a plurality of fourth ports and fifth ports corresponding to the plurality of optical channels, wherein each second port is close to and corresponds to one of the fourth ports, and an optical path is formed between one of the fourth ports and its corresponding fifth port, and the spacing between the fifth ports is greater than the spacing between the fourth ports. Figure 3As shown, the field-of-view adjustment unit 13 includes eight fourth ports, 131i, 132i, ..., 138i, each corresponding to one of the second ports of the circulator crystal 11. Taking the second port P12 and the fourth port 131i as an example, they form an optical path coupling. The optical signal output from the second port P12 is coupled into the fourth port 131i, and the optical signal output from the fourth port 131i is also coupled into the second port P12. The field-of-view adjustment unit 13 also includes eight fifth ports, 131o, 132o, ..., 138o. Each fifth port forms an optical path with one of the fourth ports. For example, the fifth port 131o forms an optical path with the fourth port 131i, and the optical signal can be transmitted bidirectionally in this optical path. The fifth port constitutes the optical signal output end face of the field-of-view adjustment unit 13, from which the optical signal is emitted. Figure 3 As shown, the spacing between the fifth ports is greater than the spacing between the fourth ports, which is more sparse in the figure. Compared with the beam output from the second port, this can increase the field of view of the beam.

[0057] Figure 4 A schematic diagram showing the beam field of view range with and without the field of view adjustment unit 13 is provided. Figure 4 The diagram also shows a shaping lens and a scanning mirror. Without the field-of-view adjustment unit 13, the light beam from the second port of the circulator crystal 11 (shown by the dashed line in the diagram) directly illuminates the shaping lens, is collimated, and then incident on the scanning mirror, where it is reflected. With the field-of-view adjustment unit 13, the light beam from the second port of the circulator crystal 11 first enters the fourth port of the field-of-view adjustment unit 13, exits through the fifth port, then illuminates the shaping lens (shown by the solid line in the diagram), is collimated, and then incident on the scanning mirror, where it is reflected. Figure 4 As shown, the area covered by the beam on the scanning mirror by the solid line is larger than the area covered by the beam on the scanning mirror by the dashed line, indicating that the field of view of the beam is effectively increased by adding the field of view adjustment unit 13.

[0058] According to a preferred embodiment of the present invention, the light-emitting end face of the field-of-view adjustment unit 13 is disposed on the focal plane of the shaping lens, and its outermost emission port (circled in the figure) is far from the center ( Figure 4In this configuration, the height difference h between the center of the field-of-view adjustment unit (located on the optical axis OO of the shaping lens) and the exit field of view is proportional. Due to the presence of the field-of-view adjustment unit, the spacing between the fifth ports is greater than the spacing between the fourth ports. Therefore, the height difference between the outermost exit ports and the center is greater compared to the case without the field-of-view adjustment unit. It is evident that the field of view is significantly increased after passing through the field-of-view adjustment unit. Furthermore, the ratio of the channel spacing between the fourth and fifth ports can be changed according to actual needs to achieve flexible control of the vertical exit field of view.

[0059] Figure 5 A field-of-view adjustment unit 13 according to a preferred embodiment of the present invention is shown. For example... Figure 5 As shown, the field-of-view adjustment unit 13 includes at least a first clamp 13a and a second clamp 13b. The first clamp 13a is close to the circulator crystal 11, and the fourth ports 131i, 132i, ..., 138i are located on the first clamp 13a. The second clamp 13b is relatively far from the circulator crystal 11, and the fifth ports 131o, 132o, ..., 138o are located on the second clamp 13a. Each group of optical transmission units 12 also includes a second optical transmission medium, which is optically coupled to the second port. Figure 5 The diagram schematically illustrates eight second optical transmission media, denoted as 12-12, 12-22, ..., 12-82. Each second optical transmission medium is held by a first clamp 13a and a second clamp 13b, and extends between one of its fourth ports and one of its fifth ports, such that the spacing of the second optical transmission media at the first clamp 13a is smaller than the spacing of the second optical transmission media at the second clamp 13b. The second optical transmission media may, for example, include optical fibers. In this embodiment, multiple optical fibers (channels) have different spacings on the first and second clamps, and are fixed by V-grooving or bonding. The spacing of the multiple optical fibers (channels) in the optical fiber fixing unit can be flexibly adjusted, and the light-emitting end face of the optical fiber is positioned on the focal plane of the shaping lens. Figure 3 For optical channel C1, the optical signal output from the second port P12 enters the second optical transmission medium (such as optical fiber) 12-12 through the fourth port 131i, and is output from the fifth port 131o. Figure 4 After the shaping lens and scanning mirror, the light is emitted into the surrounding environment and diffusely reflected on the obstacle. The reflected echo enters the second optical transmission medium 12-12 through the fifth port 131o, and then enters the second port P12 through the fourth port 131i, and is output from the third port P13 of the circulator crystal 11.

[0060] Figure 6A field-of-view adjustment unit 13 according to another embodiment of the present invention is shown, wherein the field-of-view adjustment unit 13 includes a planar optical waveguide (PLC) device 13c having a fan-shaped structure, with a smaller spacing (or structural size) on one side (left side in the figure) and a larger spacing (or structural size) on the other side (right side in the figure). The plurality of fourth ports 131i, 132i, ..., 138i are located on the side with the smaller fan-shaped structure size, and the fifth ports 131o, 132o, ..., 138o are located on the side with the larger fan-shaped structure size.

[0061] Planar optical waveguide devices can be made of materials such as lithium niobate waveguides, InP waveguides, silicon dioxide waveguides, SOI waveguides, polymer waveguides, and glass waveguides. The application of planar optical waveguide devices allows for flexible changes in the spacing between their two ports, thus enabling flexible changes in the output field of view. Furthermore, the thickness of the planar optical waveguide (PLC) device (e.g., ...) can be adjusted. Figure 6 (As shown in d2) can be controlled to a few centimeters or smaller.

[0062] Figure 7 An optical transceiver apparatus according to a preferred embodiment of the present invention is shown, wherein for clarity only eight sets of transmission units 12-1, 12-2, ..., 12-8 are shown, and the first optical transmission medium and the third optical transmission medium are not shown separately.

[0063] like Figure 7 As shown, the circulator crystal 11 includes a first polarizing beam splitter 112, a Faraday rotator 113, a quarter-wave plate 114, and a second polarizing beam splitter 115 arranged sequentially. According to a preferred embodiment of the present invention, the circulator crystal 11 further includes a first microlens array 111, a second microlens array 116, and a third microlens array 117. Because the first microlens array 111 and the third microlens array 117... Figure 7 The positions overlap, so they are not shown separately. Each port of the circulator crystal 11 is provided with a microlens. For example, the first microlens array includes a plurality of first collimating microlenses disposed between the first port and the first light transmission medium, the second microlens array includes a plurality of second collimating microlenses disposed between the second port and the field adjustment unit, and the third microlens array includes a plurality of third collimating microlenses disposed between the third port and the third light transmission medium.

[0064] The following is for reference. Figure 8a and 8b The working principle of the circulator crystal 11 is described using an optical channel (optical channel C1) as an example.

[0065] like Figure 8aAs shown, the laser beam emitted from the laser is transmitted, for example, through a first optical transmission medium. After being collimated by the first collimating microlens in the first microlens array 111, the beam is incident on the first port P11 of the circulator crystal 11. After passing through the polarization beam splitter 112, it is split into two linearly polarized beams with mutually perpendicular polarization states (the dots and lines on the arrows of the beams in Figure 8 represent vertically polarized light and horizontally polarized light, respectively). The horizontally polarized light continues to propagate along the incident direction, while the vertically polarized light is reflected by the polarization beam splitter 112 to the oblique waist of the first polarization beam splitter 112 and then reflected by its high-reflection film to the Faraday rotator 113. After passing through the Faraday rotator 113 and the quarter-wave plate 114, the horizontally polarized light rotates clockwise by π / 2 and becomes vertically polarized light. The original vertically polarized light, after passing through the Faraday rotator 113 and the quarter-wave plate 114, has its polarization direction rotated clockwise by π / 2 to become horizontally polarized light. The two line-polarized lights are then combined into a single polarization-independent beam after passing through the second polarization beam splitter 115, and exit from the second port P12. The beam is then collimated by the second microlens in the second microlens array 116, and subsequently coupled into the field-of-view adjustment unit 13 (see [link]). Figure 3 ).

[0066] like Figure 8b As shown, the echo ECHO reflected by an external object is incident on the second port P12 after passing through the second microlens of the second microlens array 116. After passing through the polarization beam splitter of the second polarization beam splitter 115, it is split into two linearly polarized beams with mutually perpendicular polarization states. The horizontally polarized beam continues to propagate along the incident light direction, while the vertically polarized beam is reflected by the polarization beam splitter of the second polarization beam splitter 115 to the oblique waist of the second polarization beam splitter 115 and then reflected by its high-reflection film to the quarter-wave plate 114. Subsequently, the polarization states of these two linearly polarized beams remain unchanged after passing through the quarter-wave plate 114 and the Faraday rotator 113. At this point, the two linearly polarized beams are combined into a single polarization-independent beam after passing through the first polarization beam splitter 112. This beam then passes through the oblique waist of the first polarization beam splitter 112 and is reflected by its high-reflection film before exiting from the third port P13. It is then collimated by the third microlens of the third microlens array 117, enters the third light transmission medium, and is finally detected by the detector.

[0067] The optical transceiver apparatus according to a preferred embodiment of the present invention has been described above. The circulator array of the present invention can achieve a large field of view with a minimal core, reducing cost and assembly difficulty, and the field of view can be flexibly changed.

[0068] The optical transceiver described above in this invention can be manufactured in a relatively small size. Taking an eight-channel example, each channel includes three ports, where the first and second ports correspond to a 2*8 fiber array, with the fiber array serving as the optical transmission medium. The size of the fiber array can be very small; for example, the spacing between two fibers can be as small as hundreds of micrometers. The beam is then collimated or focused by a 2*8 microlens array. The eight channels share a first PBS (first polarization beam splitter) / Faraday Rotator / 1 / 4 waveplate / second PBS (second polarization beam splitter), and are then coupled to a field-of-view adjustment unit via a second microlens array. The field-of-view adjustment unit includes eight optical channels, with the channel spacing at the end of the field-of-view adjustment unit closest to the second microlens array (the first end) being smaller than the channel spacing at the other end (the second end). Therefore, a very small core crystal can be used to achieve a large field of view, resulting in low cost and flexible adjustment of the field of view.

[0069] The present invention also provides a frequency-modulated continuous wave lidar 20, including the optical transceiver 10 as described above, as referred to below. Figure 9 describe.

[0070] like Figure 9 As shown, the frequency-modulated continuous wave lidar 20 includes a laser 21, a first coupler 22, an optical transceiver 10, a shaping lens 23, a scanner 24, a second coupler 25, a processing unit 26, and a detector 27. The numbers 1, 2, and 3 surrounding the optical transceiver 10 represent the first port, second port, and third port of the optical transceiver 10, respectively. The operation of the frequency-modulated continuous wave lidar 20 is as follows.

[0071] Laser 21 emits a frequency-modulated beam, which is split into a local oscillator beam and a probe beam by a first coupler 22. The probe beam is input from the first port of the optical transceiver 10 and output from the second port of the optical transceiver 10, then enters the field-of-view adjustment unit of the optical transceiver 10. The light emitted from the field-of-view adjustment unit is then emitted after passing through a shaping lens 23 (the light-emitting end face of the field-of-view adjustment unit of the optical transceiver 10 is preferably located at the focal plane of the shaping lens 23), and scanned into space by a scanning mirror 24. The echo reflected by the target is reflected by the scanning mirror 24 and received by the shaping lens 23, then enters the field-of-view adjustment unit of the optical transceiver 10. The light emitted from the field-of-view adjustment unit enters the second port of the optical transceiver 10, and is then output from the third port of the optical transceiver 10. After being received by the detector and undergoing photoelectric conversion, it coherently beats with the local oscillator beam. The distance and velocity information of the target can be analyzed based on the frequency of the beat signal. Figure 9The mid-wave echo is received by detector 27 after passing through optical transceiver 10. The echo is then mixed with the local oscillator light in second coupler 25. Processing unit 26 includes, for example, a filtering unit and an A / D sampling unit. After mixing the echo with the local oscillator light, the signal is filtered. The filter is configured to filter the mixed signal to remove stray light (caused by the system, not the probe light echo) from the stray light mixed signal obtained by mixing with the local oscillator light. The source of stray light will be described in detail below. After filtering, a beat frequency signal is obtained. After analog-to-digital conversion, a Fast Fourier Transform (FFT) is performed to obtain the frequency and corresponding amplitude of the beat frequency signals of the transmitted signal (probe light) and the received signal (probe light echo).

[0072] Specifically, for the optical transceiver 10, combined with Figure 3 The probe light is incident on the first port of the optical transceiver through the first optical transmission medium, and the echo is emitted from the third port and then incident on the third optical transmission medium. The light emitted from the third optical transmission medium is received by the detector.

[0073] Furthermore, the inventors of this application discovered that the beam-splitting end face of the circulator crystal typically results in reflected stray light (first stray light) from this channel and other channels. This first stray light mixes with the local oscillator light in the second coupler to obtain a first beat frequency signal. Reflected stray light (second stray light) also occurs at the end face of the second optical transmission medium. This second stray light mixes with the local oscillator light in the second coupler 2 to obtain a second beat frequency signal. The first and second beat frequency signals undergo a Fast Fourier Transform (FFT) to obtain the frequencies f1 and f2 of the first and second beat frequency signals. When calculating the distance to obstacles, the first and second beat frequency signals f1 and f2 are useless signals and need to be filtered out. The closer their frequencies are, the easier it is to filter them. Moreover, the difference between the first and second beat frequency signals f1 and f2 is positively correlated with the thickness of the field-of-view adjustment unit. The thickness of the field-of-view adjustment unit is as follows: Figure 5 d1 and Figure 6 In the context of d2, specifically, the smaller the thickness of the field-of-view adjustment unit, the smaller the difference between the first beat frequency signal f1 and the second beat frequency signal f2, meaning they are closer together; conversely, the larger the thickness of the field-of-view adjustment unit, the greater the difference between the first beat frequency signal f1 and the second beat frequency signal f2, meaning they are further apart. Therefore... Figure 6 The field-of-view adjustment unit 13 in the embodiment is very advantageous for filtering. Figure 10 It shows Figure 6 The frequency versus transmittance curve of the beat frequency signal obtained in the embodiment is shown below. Figure 10As shown, the frequencies of the first beat frequency signal f1 and the second beat frequency signal f2 are very close, even close to 0. Therefore, a filter can be set to simultaneously filter out both the first beat frequency signal f1 and the second beat frequency signal f2. In this case, the thickness of the field-of-view adjustment unit can be designed to be very small. Therefore, using planar optical waveguide devices as the optical transceiver device for the field-of-view adjustment unit in FMCW lidar can simultaneously solve the problems of core crystal size limitations and stray light effects at the light-emitting end face.

[0074] like Figure 11 As shown, the present invention also provides a detection method 200 for frequency-modulated continuous wave lidar, the detection method 200 comprising:

[0075] In step S201: Emit a laser beam;

[0076] In step S202: the laser beam is split into a local oscillator beam and a probe beam;

[0077] In step S203: the probe light is received through the first port of the optical transceiver device as described above and output from the second port;

[0078] In step S204: the field of view of the probe light output from the second port is increased by the field of view adjustment unit of the optical transceiver as described above;

[0079] In step S205: The probe light emitted from the field adjustment unit is emitted into the surrounding environment via the shaping lens and the scanner;

[0080] In step S206: The scanner and shaping lens cause the echo of the probe light on the obstacle to be incident on the second port of the circulator crystal through the field adjustment unit and output from the third port;

[0081] In step S207: the local oscillator light and the echo are mixed to obtain a mixed signal; and

[0082] In step S208: Calculate the distance and speed of the obstacle based on the mixing signal.

[0083] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An optical transceiver for lidar, comprising: A circulator crystal having multiple optical channels, each optical channel including at least a first port, a second port and a third port, the first port, the second port and the third port being configured to input or output a light beam in a preset manner; An optical transmission device, the optical transmission device comprising multiple sets of optical transmission units corresponding to the plurality of optical channels, each set of optical transmission units comprising a first optical transmission medium and a third optical transmission medium optically coupled to the first port and the third port respectively; and A field-of-view adjustment unit is disposed at the second port and configured to increase the field of view range of the beam output from the second port; The circulator crystal includes a first polarizing beam splitter, a Faraday rotator, a quarter-wave plate, and a second polarizing beam splitter arranged in sequence. The multiple optical channels share the first polarizing beam splitter, the Faraday rotator, the quarter-wave plate, and the second polarizing beam splitter.

2. The optical transceiver as claimed in claim 1, wherein both the first optical transmission medium and the third optical transmission medium comprise optical fibers.

3. The optical transceiver as claimed in claim 1 or 2, wherein the field-of-view adjustment unit includes a plurality of fourth ports and fifth ports corresponding to the plurality of optical channels, wherein each second port is close to and corresponds to one of the fourth ports, an optical path is formed between one of the fourth ports and a corresponding fifth port, and the spacing between the fifth ports is greater than the spacing between the fourth ports.

4. The optical transceiver apparatus of claim 3, wherein each optical transmission unit further comprises a second optical transmission medium optically coupled to the second port, the field-of-view adjustment unit comprises at least a first clamp and a second clamp, each of the second optical transmission media is held by the first clamp and the second clamp and extends between one of the fourth ports and one of the fifth ports, wherein the first clamp is close to the circulator crystal, and the spacing of the second optical transmission media at the first clamp is less than the spacing of the second optical transmission media at the second clamp, the second optical transmission medium comprising an optical fiber.

5. The optical transceiver as claimed in claim 3, wherein the field-of-view adjustment unit includes a planar optical waveguide device, the planar optical waveguide device having a fan-out structure, the plurality of fourth ports being located on the side with the smaller size of the fan-out structure, and the fifth port being located on the side with the larger size of the fan-out structure.

6. The optical transceiver as described in claim 1 or 2 further includes a first microlens array, a second microlens array, and a third microlens array, wherein the first microlens array includes a plurality of first collimating microlenses disposed between the first port and the first optical transmission medium, the second microlens array includes a plurality of second collimating microlenses disposed between the second port and the field-of-view adjustment unit, and the third microlens array includes a plurality of third collimating microlenses disposed between the third port and the third optical transmission medium.

7. A frequency-modulated continuous wave lidar, comprising the optical transceiver as described in any one of claims 1-6.

8. The frequency-modulated continuous wave lidar of claim 7 further includes a shaping lens and a scanner, wherein the light-emitting end face of the field-of-view adjustment unit is disposed at the focal plane of the shaping lens, and the scanner is configured to receive a light beam from the shaping lens and reflect it to the outside of the lidar for scanning, and / or receive a light beam from the outside and reflect it to the shaping lens.

9. The frequency-modulated continuous wave lidar as described in claim 8, further comprising: A laser, configured to emit a laser beam; A first coupler is configured to receive the laser beam and split it into a local oscillator beam and a probe beam. The optical transceiver receives the probe beam through a first port and outputs it from a second port. The probe beam passes through the field-of-view adjustment unit and is emitted into the surrounding environment via the shaping lens and the scanner. The echo of the probe beam on the obstacle passes through the scanner and the shaping lens and is incident on the second port of the circulator crystal through the field-of-view adjustment unit, and is output from a third port. A second coupler is configured to receive the local oscillator light and the echo and mix them to obtain a mixed signal; and A processing unit configured to calculate the distance and velocity of the obstacle based on the mixing signal.

10. The frequency-modulated continuous wave lidar as claimed in claim 9, wherein the probe light is incident on the first port of the optical transceiver through the first optical transmission medium, and the echo is emitted from the third port and then incident on the third optical transmission medium.

11. The frequency-modulated continuous wave lidar of claim 9, wherein the processing unit includes a filter configured to filter the mixing signal to remove stray light mixing signal obtained by mixing stray light with local oscillator light.

12. A detection method for a frequency-modulated continuous wave lidar, comprising: S201: Emits a laser beam; S202: Split the laser beam into a local oscillator beam and a probe beam; S203: The probe light is received through the first port of the circulator crystal of the optical transceiver as described in any one of claims 1-6 and output from the second port; S204: The field of view of the probe light output from the second port of the circulator crystal is increased by the field of view adjustment unit of the optical transceiver; S205: The probe light emitted from the field adjustment unit is emitted into the surrounding environment via the shaping lens and the scanner; S206: The scanner and shaping lens cause the echo of the probe light on the obstacle to be incident on the second port of the circulator crystal through the field adjustment unit, and output from the third port of the circulator crystal; S207: Mix the local oscillator light with the echo to obtain a mixed signal; and S208: Calculate the distance and speed of the obstacle based on the mixed signal.

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