CN210690828U - Laser radar receiving device, laser radar transmitting device and laser radar transmitting system - Google Patents
Laser radar receiving device, laser radar transmitting device and laser radar transmitting system Download PDFInfo
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- CN210690828U CN210690828U CN201920327676.XU CN201920327676U CN210690828U CN 210690828 U CN210690828 U CN 210690828U CN 201920327676 U CN201920327676 U CN 201920327676U CN 210690828 U CN210690828 U CN 210690828U
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Abstract
The application relates to a laser radar receiving device, a laser radar transmitting device and a laser radar receiving system. The laser radar receiving apparatus includes: a light receiving device, an interference device, a photodetector; the optical receiving device is used for coupling the received echo signals to the interference device through free space; the interference device is used for receiving a local oscillator signal corresponding to the echo signal through a free space, interfering the echo signal with the local oscillator signal to obtain a difference frequency signal, and coupling the difference frequency signal to the photoelectric detector through the free space; and the photoelectric detector is used for carrying out photoelectric conversion on the difference frequency signal. The laser radar receiving device reduces the coupling loss of the received echo signals, improves the energy of the echo signals, enables the echo signals to interfere with local oscillation signals as much as possible, and improves the signal-to-noise ratio of a laser radar system.
Description
Technical Field
The application relates to the field of laser radars, in particular to a laser radar receiving device, a laser radar transmitting device and a laser radar receiving system.
Background
At present, Frequency Modulated Continuous Wave (FMCW) laser radar systems have been widely used in the field of ranging due to their advantages of high interference rejection, small required transmission energy, and the like. The FMCW laser radar system transmits frequency modulation continuous waves, interference is carried out by utilizing received echo signals and local oscillation signals, so that difference frequency signals of ranging information are obtained, and further the distance is measured and calculated by utilizing the difference frequency signals.
In the conventional technology, an FMCW lidar system couples an echo signal and a local oscillator signal into an optical fiber for interference, so as to generate a difference frequency signal.
However, the conventional method causes coupling loss of the return signal, so that the energy of the return signal during interference is smaller, and the signal-to-noise ratio of the FMCW lidar system is lower.
SUMMERY OF THE UTILITY MODEL
Therefore, it is necessary to provide a laser radar receiving apparatus, a laser radar transmitting apparatus, and a laser radar system, which solve the technical problems that the conventional method causes coupling loss of echo signals, and the energy of the echo signals during interference is small, thereby resulting in low signal-to-noise ratio of the FMCW laser radar system.
A laser radar receiving apparatus comprising: a light receiving device, an interference device, a photodetector;
the optical receiving device is used for coupling the received echo signals to the interference device through free space;
the interference device is used for receiving a local oscillator signal corresponding to the echo signal through a free space, interfering the echo signal with the local oscillator signal to obtain a difference frequency signal, and coupling the difference frequency signal to the photoelectric detector through the free space;
and the photoelectric detector is used for carrying out photoelectric conversion on the difference frequency signal.
In one embodiment, the interference device comprises a thin film beamsplitter.
In one embodiment, the thin film optical splitter comprises an antireflection film with a transmission reflectance larger than a preset threshold value.
In one embodiment, the thin film splitter has a 99:1 transmittance-reflectance.
In one embodiment, the photodetector comprises an avalanche photodetector array.
In one embodiment, the apparatus further comprises a beam-reducing diaphragm; the beam-shrinking diaphragm is used for converging the difference frequency signal to the photoelectric detector.
In one embodiment, the thin film beam splitter comprises a single layer thin film beam splitter or a multilayer thin film beam splitter.
A lidar transmission device comprising: an emission collimating device; the emission collimating device is connected with a laser radar light source;
the transmitting collimating device is used for coupling frequency modulated laser output by the laser radar light source, taking the frequency modulated laser as a local oscillator signal, and coupling the local oscillator signal to the interference device through a free space so that the interference device interferes the local oscillator signal with an echo signal; the echo signal is a signal which is reflected back by a target object after the frequency modulation laser is incident to the target object and is received by a light receiving device.
In one embodiment, the emission collimating means comprises a collimating mirror.
A lidar system comprising a lidar receiving apparatus as in the preceding embodiments, and a lidar transmitting apparatus as in the preceding embodiments.
The application provides a laser radar receiving arrangement, emitter and system because the interference device is through free space receiving echo signal and local oscillator signal to carry out coherent interference through the received echo signal of free space and local oscillator signal, like this, just no longer need carry out coherent interference in coupling echo signal and local oscillator signal to optic fibre. Compared with the prior art, the coupling loss of the received echo signals is reduced, the energy of the echo signals is improved, the echo signals and local oscillation signals interfere as much as possible, and the signal-to-noise ratio of the laser radar system is improved.
Drawings
Fig. 1 is a schematic structural diagram of a laser radar receiving apparatus according to an embodiment;
fig. 2 is a schematic structural diagram of a lidar transmitting device according to an embodiment;
FIG. 3 is a schematic diagram of a lidar system according to an embodiment;
fig. 4 is a schematic structural diagram of a lidar system according to another embodiment.
Description of reference numerals:
10: a light receiving device; 11: an interference device; 12: a photodetector;
20: an emission collimating device; 30: a laser radar light source; 31: a laser radar transmitting device;
32: a laser radar receiving device; 33: a correction device; 34: a digital processing circuit;
35: a third coupler; 301: a frequency-modulated laser; 302: an optical isolator;
311: a first coupler; 312: a collimating mirror; 313: a light emitting device;
322: a thin film beam splitter; 323: a beam-shrinking diaphragm; 324: an avalanche photodetector array;
331: a second coupler; 332: a Mach-Zehnder interferometer; 333: a fourth coupler;
334: a balance detector; 341: an analog-to-digital converter; 342: a signal analysis unit.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions in the embodiments of the present application are further described in detail by the following embodiments in combination with the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
Fig. 1 is a schematic structural diagram of a laser radar receiving apparatus according to an embodiment. As shown in fig. 1, the apparatus may include: a light receiving device 10, an interference device 11, and a photodetector 12. A light receiving device 10 for coupling the received echo signal to an interference device 11 through a free space; the interference device 11 is configured to receive a local oscillator signal corresponding to the echo signal through a free space, interfere the echo signal with the local oscillator signal to obtain a difference frequency signal, and couple the difference frequency signal to the photodetector 12 through the free space; and a photodetector 12 for photoelectrically converting the difference frequency signal.
Specifically, a light emitting device in the laser radar system emits frequency modulated laser to a target object, and after the frequency modulated laser touches the target object, a reflected light signal or a scattered light signal is formed. The optical signal reflected or scattered from the target object is received by the optical receiving device 10, and then an echo signal corresponding to the frequency modulated laser is obtained. Then, the light receiving device 10 couples the received echo signal to the interference device 11 through a free space. The light receiving device 10 is a device required to receive a reflected light signal or a scattered light signal, and may be a receiving lens. The above-mentioned free space refers to a space existing between the light receiving device 10 and the interference device 11.
The interference device 11 receives the echo signal propagated through the free space on one hand, and receives the local oscillation signal corresponding to the echo signal propagated through the free space on the other hand, and performs coherent interference on the received echo signal and the local oscillation signal to obtain a difference frequency signal. The interference device 11 receives the local oscillator signal through a free space, which is a space existing between the transmit collimating device 20 that generates the local oscillator signal and the interference device 11. Optionally, the interference device 11 is a thin film optical splitter, and the thin film optical splitter is an antireflection film with a transmittance-reflectance greater than a preset threshold. Optionally, the transmittance-reflectance ratio of the thin film splitter is 99:1, and the thin film splitter is a single-layer thin film splitter or a multi-layer thin film splitter. Taking the interference device 11 as a thin film optical splitter as an example, the light receiving device 10 receives the echo signal and transmits the received echo signal to the thin film optical splitter through a free space, so as to form a light spot on the thin film optical splitter. Meanwhile, the film optical splitter receives the local oscillation signal corresponding to the echo signal through the free space, so that the local oscillation signal forms a light spot on the film optical splitter, and the size of the light spot formed by the echo signal on the film optical splitter is basically consistent with that of the light spot formed by the local oscillation signal on the film optical splitter. Then, the thin film optical splitter performs coherent interference on the echo signal and the local oscillation signal to obtain a difference frequency signal, and the obtained difference frequency signal is transmitted to the photodetector 12 through a free space.
The photodetector 12 receives the difference frequency signal propagated by the interference device 11 through the free space, performs photoelectric conversion on the difference frequency signal, and inputs the photoelectric-converted difference frequency signal to the digital processing circuit to analyze the difference frequency signal carrying the distance information. The photodetector 12 may be a device capable of receiving a difference frequency signal through a free space, which refers to a space existing between the interference device 11 and the photodetector 12, and performing photoelectric conversion on the difference frequency signal. In one embodiment, photodetector 12 may comprise an avalanche photodetector array. Optionally, the laser radar receiving apparatus may further include a beam reduction diaphragm, in this case, the beam reduction diaphragm receives the difference frequency signal transmitted by the interference device 11 through a free space, and converges the received difference frequency signal onto the photosensitive surface of the avalanche photoelectric detection array. The avalanche photoelectric detection array performs photoelectric conversion on the received difference frequency signal and transmits the photoelectric-converted difference frequency signal to the digital processing circuit.
According to the laser radar receiving device provided by the embodiment, the interference device receives the echo signal and the local oscillator signal through the free space and performs coherent interference on the echo signal and the local oscillator signal received through the free space, so that the echo signal and the local oscillator signal do not need to be coupled into the optical fiber for coherent interference. Compared with the prior art, the coupling loss of the echo signals is reduced, the energy of the echo signals is improved, the echo signals and local oscillation signals interfere as much as possible, and the signal-to-noise ratio of the laser radar system is improved. In addition, when the interference device adopts the thin film optical splitter, the transmission reflection ratio of the adopted thin film optical splitter is higher, so that the energy of an echo signal can be improved, and the signal-to-noise ratio of the laser radar system is further improved.
Fig. 2 is a laser radar transmitting apparatus according to an embodiment, where the apparatus may include: an emission collimating device 20; the emission collimating device 20 is connected with a laser radar light source; the emission collimating device 20 is configured to couple frequency modulated laser output by a laser radar light source, use the frequency modulated laser as a local oscillation signal, and couple the local oscillation signal to the interference device 11 through a free space, so that the interference device 11 interferes the local oscillation signal with an echo signal; the echo signal is a signal that is reflected by the target object and received by the light receiving device 10 after the frequency-modulated laser is incident on the target object.
Specifically, the lidar light source is configured to generate a time-varying frequency-modulated laser, and to couple the generated frequency-modulated laser to the emission collimating device 20 via the coupler. The laser radar light source can be a semiconductor laser and a frequency modulation laser. Then, the transmitting collimator 20 transmits the coupled frequency-modulated laser as a local oscillation signal to the interference device 11 through a free space, so as to perform coherent interference on the received local oscillation signal and the echo signal on the interference device 11. The transmitting collimator 20 propagates the local oscillator signal to the interferometer 11 through a free space, where the free space refers to a space existing between the transmitting collimator 20 that generates the local oscillator signal and the interferometer 11. The echo signal corresponds to a local oscillator signal, which is a signal that is received by the interference device 11 through a free space, and is reflected back by the target object after the frequency-modulated laser is incident on the target object, and is received by the optical receiving device 10.
Optionally, the emission collimating device 20 includes a collimating mirror, which may be a fiber collimating mirror, or may be another type of collimating mirror. The collimating mirror can collimate the frequency-modulated laser coupled from the coupler, and emit the collimated frequency-modulated laser as a local oscillation signal, thereby forming a light spot on the interference device 11. The size of the light spot is substantially the same as the size of the light spot formed on the interference device 11 by the echo signal, thereby facilitating coherent interference of the signals.
The laser radar transmitting device provided by the embodiment can transmit the local oscillator signal to the interference device through the free space by the transmitting collimating device in the laser radar transmitting device, so that the interference device can perform coherent interference on the local oscillator signal and the echo signal received through the free space, and thus, coherent interference with the echo signal in coupling the local oscillator signal to the optical fiber is not needed. Compared with the prior art, the coupling loss of the echo signals is reduced, the energy of the echo signals is improved, the echo signals and local oscillation signals interfere as much as possible, and the signal-to-noise ratio of the laser radar system is improved.
Fig. 3 is a diagram of a lidar system according to an embodiment, which may include a lidar receiving apparatus according to an embodiment and a lidar transmitting apparatus according to an embodiment.
In one embodiment, a lidar system is also provided as shown in fig. 4, which may include a lidar light source 30, a lidar transmission device 31, a lidar reception device 32, a correction device 33, and digital processing circuitry 34. Lidar light source 30 comprises a frequency-modulated laser 301 and an optical isolator 302. The laser radar transmitting apparatus 31 includes a first coupler 311, a collimator mirror 312, and a light emitting device 313. The lidar receiving apparatus 32 includes a light receiving device 10, a thin-film beam splitter 322, a beam reduction diaphragm 323, and an avalanche photodetection array 324. The digital processing circuit 34 includes an analog-to-digital converter 341 and a signal analysis unit 342. The correction device 33 includes a second coupler 331, a mach-zehnder interferometer 332, a fourth coupler 333, and a balanced detector 334.
When the system works, the frequency modulation laser 301 generates frequency modulation laser which changes along with time, and 99% of the frequency modulation laser enters the laser radar transmitting device 31 and 1% of the frequency modulation laser enters the correcting device 33 through the isolation of the optical isolator 302 and the light splitting of the third coupler 35 (the third coupler 35 can be a coupler with a ratio of 99: 1). On the one hand, the frequency modulated laser entering the laser radar transmitter 31 is split by the first coupler 311, 99% of the frequency modulated laser is transmitted to the target object by the light emitting device 313, and 1% of the frequency modulated laser is transmitted to the thin film splitter 322 by the collimating mirror 312 as a local oscillation signal during coherent interference. The light receiving device 10 propagates the received echo signal to the thin film beam splitter 322. The thin film optical splitter 322 interferes the received local oscillation signal with the echo signal to obtain a difference frequency signal, and transmits the obtained difference frequency signal to the beam reduction diaphragm 323. The beam stop 323 focuses the difference frequency signal onto the photosensitive surface of the avalanche photodetector array 324. The avalanche photodetector array 324 photoelectrically converts the difference frequency signal, and inputs the photoelectrically converted difference frequency signal to the analog-to-digital converter 341. The analog-to-digital converter 341 performs analog-to-digital conversion on the photoelectrically converted difference frequency signal, and inputs the analog-to-digital converted difference frequency signal to the signal analysis unit 342, so that the signal analysis unit 342 analyzes the analog-to-digital converted difference frequency signal, thereby obtaining the distance between the current object and the target object.
On the other hand, the frequency-modulated laser light entering the correction device 33 is split by the second coupler 331, and the split optical signal enters the mach-zehnder interferometer 332, is subjected to converging coherence by the fourth coupler 333, and is subjected to photoelectric conversion by the balanced detector 334 to obtain an intermediate frequency signal. The intermediate frequency signal may be used to perform nonlinear correction on the modulation current or voltage of the frequency modulated laser 301, so that the frequency modulated laser 301 emits a chirped laser meeting the requirement.
Of course, the system can be used for not only distance measurement, but also positioning, speed measurement and the like.
The laser radar system that this embodiment provided, because interference device in the receiving arrangement of laser radar system can be through free space receiving echo signal, and the local oscillator signal can be transmitted to interference device through free space to the transmission collimating device in the transmitting arrangement of laser radar system for interference device can carry out coherent interference to echo signal and local oscillator signal received through free space, and like this, just no longer need carry out coherent interference in coupling echo signal and local oscillator signal to optic fibre. Compared with the prior art, the coupling loss of the echo signals is reduced, the energy of the echo signals is improved, the echo signals and local oscillation signals interfere as much as possible, and the signal-to-noise ratio of the laser radar system is improved. In addition, when the interference device adopts the thin film optical splitter, the transmission reflection ratio of the adopted thin film optical splitter is higher, so that the energy of an echo signal can be improved, and the signal-to-noise ratio of the laser radar system is further improved.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present application. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A laser radar receiving apparatus, comprising: a light receiving device, an interference device, a photodetector;
the optical receiving device is used for coupling the received echo signals to the interference device through free space;
the interference device is used for receiving a local oscillator signal corresponding to the echo signal through a free space, interfering the echo signal with the local oscillator signal to obtain a difference frequency signal, and coupling the difference frequency signal to the photoelectric detector through the free space; and the photoelectric detector is used for carrying out photoelectric conversion on the difference frequency signal.
2. The apparatus of claim 1, wherein the interference device comprises a thin film beamsplitter.
3. The apparatus of claim 2, wherein the thin film optical splitter comprises an anti-reflective coating having a transmission reflectance greater than a predetermined threshold.
4. The apparatus of claim 3, wherein the thin film splitter has a transmittance-reflectance of 99: 1.
5. The apparatus of claim 1, wherein the photodetector comprises an avalanche photodetector array.
6. The apparatus of claim 1, further comprising a beam-reducing stop; the beam-shrinking diaphragm is used for converging the difference frequency signal to the photoelectric detector.
7. The apparatus of any one of claims 2 to 4, wherein the thin film beam splitter comprises a single layer thin film beam splitter or a multilayer thin film beam splitter.
8. A lidar transmitting apparatus, comprising: an emission collimating device; the emission collimating device is connected with a laser radar light source;
the transmitting collimating device is used for coupling frequency modulated laser output by the laser radar light source, taking the frequency modulated laser as a local oscillator signal, and coupling the local oscillator signal to the interference device through a free space so that the interference device interferes the local oscillator signal with an echo signal; the echo signal is a signal which is reflected back by a target object after the frequency modulation laser is incident to the target object and is received by a light receiving device.
9. The apparatus of claim 8, wherein the emission collimating means comprises a collimating mirror.
10. Lidar system, characterized in that it comprises a lidar receiving apparatus according to any of claims 1 to 7, and a lidar transmitting apparatus according to claim 8 or 9.
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| CN109946707A (en) * | 2019-03-15 | 2019-06-28 | 深圳市速腾聚创科技有限公司 | Laser radar reception device, emitter, system and distance measurement method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109946707A (en) * | 2019-03-15 | 2019-06-28 | 深圳市速腾聚创科技有限公司 | Laser radar reception device, emitter, system and distance measurement method |
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