A lidar system and optical system thereof

Abstract

The application provides a laser radar system and an optical system thereof, comprising a plurality of device groups; each device group comprises a light emitter, a light detector, a phase modulator and a phase demodulator; the phase modulator is located at a light outlet of the light emitter in the same group as the phase modulator, and is used for phase modulating the detection light emitted by the light emitter; the phase demodulator is located at a light inlet of the light detector in the same group as the phase demodulator, and is used for phase demodulating the detection light reflected by a target object; wherein the phases of the detection light phase-modulated by the phase modulators of different groups are different, and the phase demodulator only phase-demodulates the detection light phase-modulated by the phase modulator in the same group as the phase demodulator, so that the accurate alignment between the light emitter and the light detector in the same group can be realized without manual alignment during the assembly of the light source module and the laser radar system, the production efficiency of the laser radar is improved, and the assembly cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of radar, more particularly, to a laser radar system and an optical system thereof. BACKGROUND

[0002] Laser radar is a radar system that detects the position, velocity and other characteristic quantities of a target by emitting a laser beam, and its working principle is to emit a detection signal (laser beam) to a target, then compare the signal received from the target with the emitted signal and make appropriate processing, so as to obtain relevant information of the target, such as target distance, direction, height, velocity, attitude and even shape, etc., to realize the detection, tracking and identification of targets such as aircraft and missiles.

[0003] The laser radar needs to have a certain field of view angle in the horizontal direction and the vertical direction, for example, the laser radar on the automatic driving generally needs to have a 360-degree field of view angle in the horizontal direction and a 20-degree to 30-degree field of view angle in the vertical direction. In order to realize the field of view angle in the vertical direction, a plurality of line “laser-light detector” combinations need to be arranged in the vertical direction, and each line “laser-light detector” combination is spaced by 0.5 degrees to 1 degree. In order to ensure that there is no signal crosstalk between different lines, for example, the light of a line laser is measured by another line light detector, the laser and the light detector must be accurately aligned.

[0004] In the prior art, the accurate alignment between the laser and the light detector is generally realized by manual alignment, but this results in high assembly cost and low production efficiency of the laser radar. SUMMARY

[0005] Therefore, the present application provides a laser radar system and an optical system thereof to solve the problems of high assembly cost and low production efficiency of the existing laser radar.

[0006] To achieve the above object, the present application provides the following technical scheme:

[0007] An optical system comprises a plurality of device groups.

[0008] Each device group comprises a light emitter, a light detector, a phase modulator and a phase demodulator.

[0009] The phase modulator is located at the light outlet of the light emitter in the same group, and is used for phase modulating the detection light emitted by the light emitter, so that the modulated detection light irradiates on a target object.

[0010] The phase demodulator is located at the light inlet of the light detector in the same group as the phase demodulator, and is used for phase demodulation of the probe light reflected by the target object, so that the phase-demodulated probe light is irradiated on the light detector.

[0011] The phase of the probe light phase-modulated by the phase modulators in different groups is different, and the phase demodulator only demodulates the phase of the probe light phase-modulated by the phase modulator in the same group.

[0012] Optionally, the phase modulator comprises an orbital angular momentum modulator.

[0013] The phase demodulator comprises an orbital angular momentum demodulator.

[0014] Optionally, the phase distribution of the orbital angular momentum modulator and the orbital angular momentum demodulator in the same device group is opposite.

[0015] Optionally, the absolute values of the topological quantum numbers of the orbital angular momentum demodulator and the orbital angular momentum modulator in the same group are equal but opposite in sign.

[0016] The topological quantum numbers of the orbital angular momentum modulators in different device groups are different.

[0017] Optionally, the topological quantum numbers of the orbital angular momentum modulators in different device groups are different, comprising:

[0018] The absolute values of the topological quantum numbers of the orbital angular momentum modulators in different device groups are equal but opposite in sign, or the absolute values of the topological quantum numbers of the orbital angular momentum modulators in different device groups are not equal but the same in sign, or the absolute values of the topological quantum numbers of the orbital angular momentum modulators in different device groups are not equal and opposite in sign.

[0019] Optionally, the orbital angular momentum modulator is a first spiral phase step plate, the orbital angular momentum demodulator is a second spiral phase step plate, the absolute values of the topological quantum numbers of the first spiral phase step plate and the second spiral phase step plate in the same device group are equal but opposite in sign, and the topological quantum numbers of the first spiral phase step plates in different device groups are different.

[0020] Optionally, the orbital angular momentum modulator is a first spatial light modulator, the orbital angular momentum demodulator is a second spatial light modulator, the absolute values of the topological quantum numbers of the first spatial light modulator and the second spatial light modulator in the same device group are equal but opposite in sign, and the topological quantum numbers of the first spatial light modulators in different device groups are different.

[0021] Optionally, the orbital angular momentum modulator is a first subwavelength grating, the orbital angular momentum demodulator is a second subwavelength grating, the absolute values of the topological quantum numbers of the first subwavelength grating and the second subwavelength grating of the same device group are equal but opposite in sign, and the topological quantum numbers of the first subwavelength gratings of different device groups are different.

[0022] Optionally, further comprising an optical stop between the phase demodulator and the photodetector.

[0023] A lidar system comprising the optical system of any one of the above.

[0024] Compared with the prior art, the technical solution provided by the present application has the following advantages:

[0025] The lidar system and the optical system thereof provided by the present application have the following advantages: the phases of the detection light modulated by the phase modulators of different groups are different, and the phase demodulator only demodulates the phase of the detection light modulated by the phase modulator of the same group, so that the precise alignment between the light emitters and the photodetectors of the same group can be achieved without manual alignment during the assembly of the optical system and the lidar system, thereby improving the production efficiency of the lidar and reducing the assembly cost. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and those skilled in the art can obtain other drawings according to the provided drawings without creative labor.

[0027] Figure 1 The structural schematic diagram of the optical system provided by the embodiment of the present application;

[0028] Figure 2 The structural schematic diagram of the spiral phase step plate provided by the embodiment of the present application;

[0029] Figure 3 The modulation process schematic diagram of the orbital angular momentum modulator provided by the embodiment of the present application;

[0030] Figure 4 The demodulation process schematic diagram of the orbital angular momentum demodulator provided by the embodiment of the present application;

[0031] Figure 5 The modulation and demodulation process schematic diagram of the orbital angular momentum modulator and the orbital angular momentum demodulator of different groups provided by the embodiment of the present application. DETAILED DESCRIPTION

[0032] The above is the core idea of ​​this invention. To make the above-mentioned objectives, features, and advantages of this invention more apparent and understandable, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] This invention provides an optical system, such as... Figure 1 As shown, it includes multiple device groups, each of which includes an optical transmitter 10, a photodetector 11, a phase modulator 12, and a phase demodulator 13. The phase modulator 12 is located at the output port of the optical transmitter 10 in the same group, and the phase demodulator 13 is located at the input port of the photodetector 11 in the same group.

[0034] Furthermore, the phase modulator 12 is used to phase modulate the probe light emitted from the light output port of the light emitter 10, so that the modulated probe light illuminates the target object. The phase demodulator 13 is used to phase demodulate the probe light reflected from the target object, so that the phase demodulated probe light illuminates the photodetector 11 in the same group. The probe light modulated by phase modulators 12 in different groups has different phases, and the phase demodulator 13 only demodulates the probe light modulated by phase modulators 12 in the same group.

[0035] like Figure 1 As shown, the phase modulator 12 of the first device group modulates the phase of the probe light emitted from the light emitter 10 in the same group, so that the probe light a1 illuminates the target object. The phase modulator 12 of the second device group modulates the phase of the probe light emitted from the light emitter 10 in the same group, so that the probe light a2 illuminates the target object. The probe lights a1 and a2 have different phases. After the target object reflects the probe lights a1 and a2, the phase demodulator 13 of the first device group only demodulates the phase of the probe light a1, so that the probe light a1 enters the photodetector 11 of the first device group. The phase demodulator 13 of the second device group only demodulates the phase of the probe light a2, so that the probe light a2 enters the photodetector 11 of the second device group. And so on. The probe lights emitted from the light emitters 10 of different device groups can only enter the photodetector 11 of the same group after passing through the corresponding phase modulator 12 and phase demodulator 13.

[0036] Based on this, even if no strict optical alignment is performed, the light emitters 10 and the light detectors 11 in each group are one-to-one corresponding, and signal crosstalk between different lines or different groups can be avoided, so that during assembly of the optical system and the laser radar system, manual alignment is not required, and accurate alignment between the light emitters 10 and the light detectors 11 in the same group can be achieved, the production efficiency of the laser radar is improved, and the assembly cost is reduced.

[0037] Optionally, in the structure shown in Figure 1 In the structure shown, the light emitters 10 and the light detectors 11 in the same group are arranged in sequence in the vertical direction Y, and the light emitters 10 and the light detectors 11 in different groups are also arranged in sequence in the vertical direction Y to realize the field of view angle in the vertical direction Y. Of course, the present application is not limited thereto, and in other embodiments, the positions and arrangement modes of the light emitters 10 and the light detectors 11 can be set according to the field of view angle requirements in the horizontal direction X and the vertical direction Y.

[0038] Optionally, the light emitter 10 in the embodiment of the present application is a laser, and of course, the present application is not limited thereto, and in other embodiments, the light emitter 10 can also be a light-emitting diode and the like. Optionally, an optical stop is further included between the phase demodulator 13 and the light detector 11 to filter light and the like.

[0039] In the embodiment of the present application, the phase modulator 12 includes an orbital angular momentum (OAM) modulator, and the phase demodulator 13 includes an orbital angular momentum demodulator.

[0040] It should be noted that the orbital angular momentum is a natural property of all light beams with spiral phase. A plane wave light beam or a Gaussian light beam passes through an optical device with spiral phase distribution, and spiral phase light with orbital angular momentum can be generated. For example, Figure 2 As shown, the optical device for converting a Gaussian light beam into spiral phase light includes a spiral phase step plate, that is, the orbital angular momentum modulator and the orbital angular momentum demodulator are spiral phase step plates, and of course, the present application is not limited thereto, and in other embodiments, as shown in Figures 3 to 5 The orbital angular momentum modulator and the orbital angular momentum demodulator can also be a spatial light modulator (SLM), or can also be a subwavelength grating and the like.

[0041] In the embodiment of the present application, the light beam emitted by the light emitter 10, that is, the laser, is a Gaussian light beam, and the Gaussian light beam will be converted into spiral phase light after being modulated by the orbital angular momentum modulator, as shown in Figure 3As shown, the Gaussian beam is converted into spiral phase light after passing through the spatial light modulator with topological quantum number l = +4 of spiral phase distribution. The amplitude distribution of the spiral phase light is completely different from that of the Gaussian light, which is a ring-shaped amplitude distribution. The spiral phase light is converted into Gaussian light after passing through the orbital angular momentum demodulator, as shown in Figure 4 As shown, the spiral phase light can be converted back into Gaussian light after passing through another spatial light modulator with topological quantum number l = -4 of spiral phase distribution.

[0042] The key of the orbital angular momentum demodulation is that the phase distribution of the orbital angular momentum demodulator is opposite to that of the orbital angular momentum modulator. From the mathematical analysis, if the phase distribution of the orbital angular momentum modulation is exp (i l f r), the phase distribution of the demodulation must be exp (-i l f r), so as to completely eliminate the spiral phase distribution and restore the Gaussian phase distribution. If the phase distribution of the orbital angular momentum demodulation is exp (i l f r), the spiral phase distribution cannot be completely eliminated, and the generated light is still spiral light.

[0043] Therefore, in the embodiment of the present application, the phase distributions of the orbital angular momentum modulators and the orbital angular momentum demodulators in the same group are opposite. Alternatively, the absolute values of the topological quantum numbers l of the orbital angular momentum demodulators and the orbital angular momentum modulators in the same group are equal but opposite, so that the phase distributions of the orbital angular momentum modulators and the orbital angular momentum demodulators in the same group are opposite. Moreover, the topological quantum numbers l of the orbital angular momentum modulators in different groups are different, so that the light emitter 10 and the light detector 11 are one-to-one corresponding, and the accurate alignment between the light emitter 10 and the light detector 11 in the same group is realized.

[0044] The topological quantum numbers l of the orbital angular momentum modulators in different groups are different, including:

[0045] The absolute values of the topological quantum numbers l of the orbital angular momentum modulators in different groups are equal but opposite, such as the topological quantum number l = +3 of the orbital angular momentum modulator and the topological quantum number l = -3 of the orbital angular momentum demodulator in one group, and the topological quantum number l = -3 of the orbital angular momentum modulator and the topological quantum number l = +3 of the orbital angular momentum demodulator in another group.

[0046] Alternatively, the absolute values of the topological quantum numbers l of the orbital angular momentum modulators in different groups are not equal but the same, such as the topological quantum number l = +3 of the orbital angular momentum modulator and the topological quantum number l = -3 of the orbital angular momentum demodulator in one group, and the topological quantum number l = +6 of the orbital angular momentum modulator and the topological quantum number l = -6 of the orbital angular momentum demodulator in another group.

[0047] Or, the absolute values of the topological quantum number l of the orbital angular momentum modulators of different device groups are not equal and opposite, such as the topological quantum number l of the orbital angular momentum modulator of one device group is +3, the topological quantum number l of the orbital angular momentum demodulator is -3, the topological quantum number l of the orbital angular momentum modulator of another device group is -6, and the topological quantum number l of the orbital angular momentum demodulator is +6.

[0048] It should be noted that, regardless of the topological quantum number l of the orbital angular momentum modulator is positive or negative, the absolute value of the topological quantum number l of the orbital angular momentum demodulator in the same group is equal to that of the orbital angular momentum modulator, and the positive and negative are opposite.

[0049] Alternatively, the orbital angular momentum modulator in the embodiment of the present application is a first spiral phase step plate, the orbital angular momentum demodulator is a second spiral phase step plate, the absolute values of the topological quantum number l of the first spiral phase step plate and the second spiral phase step plate in the same device group are equal but opposite, and the topological quantum number l of the first spiral phase step plate in different device groups is different.

[0050] Alternatively, the orbital angular momentum modulator is a first spatial light modulator, the orbital angular momentum demodulator is a second spatial light modulator, the absolute values of the topological quantum number l of the first spatial light modulator and the second spatial light modulator in the same device group are equal but opposite, and the topological quantum number l of the first spatial light modulator in different device groups is different.

[0051] Alternatively, the orbital angular momentum modulator is a first subwavelength grating, the orbital angular momentum demodulator is a second subwavelength grating, the absolute values of the topological quantum number l of the first subwavelength grating and the second subwavelength grating in the same device group are equal but opposite, and the topological quantum number l of the first subwavelength grating in different device groups is different.

[0052] In a specific embodiment of the present application, as shown in Figure 5 The Gaussian light emitted by the first device group light emitter 10, such as a No. 1 laser, is modulated by the spatial light modulator, i.e. the phase modulator 12, with a topological quantum number l of -4, to form a spiral phase light. The spiral phase light is reflected back to the receiving end of the first device group light detector 11 by the target object, and is demodulated by the spatial light modulator, i.e. the phase demodulator 13, with a topological quantum number l of +4, to restore the Gaussian light beam. The Gaussian light beam can be received by the first device group light detector 11, i.e. No. 1 light detector, through the circular light hole, i.e. the diaphragm, behind the spatial light modulator.

[0053] If the light of the light emitters 10 of other device groups (such as the No. 2 laser, the No. 3 laser,...) enters the receiving end of the first device group, since the phase demodulator 13 is not matched with the light, the light cannot be phase demodulated by the phase demodulator 13, still being helical phase light, having a ring-shaped amplitude distribution, and thus cannot pass through the circular light hole, i.e., the diaphragm, and cannot be received by the light emitters 10 of the first device group, such as the No. 1 light detector. The other device groups are similar to the first device group, and thus will not be described herein. In this way, the light emitters 10 and the light detectors 11 of each device group are one-to-one corresponding, meeting the high-precision alignment requirement of the laser radar system.

[0054] It should be noted that, Figure 5 For example, the OAM modulator of the first device group is a first spatial light modulator with a topological quantum number l of -4, the OAM demodulator is a second spatial light modulator with a topological quantum number of +4, the OAM modulator of the second device group is a first spatial light modulator with a topological quantum number l of -8, the OAM demodulator is a second spatial light modulator with a topological quantum number of +8, the OAM modulator of the third device group is a first spatial light modulator with a topological quantum number l of +8, the OAM demodulator is a second spatial light modulator with a topological quantum number of -8, and the OAM modulator of the fourth device group is a first spatial light modulator with a topological quantum number l of -16, and the OAM demodulator is a second spatial light modulator with a topological quantum number of +16. The application is not limited thereto.

[0055] The application further provides a laser radar system comprising the light source module according to any one of the above. Of course, the laser radar system further comprises an analysis processing unit, which is connected with the light detectors 11 of all the device groups, and is used for analyzing and processing the signals of the light detectors 11 to obtain relevant information of the target object. The relevant information includes target distance, direction, height, speed, attitude, and even shape, etc. parameter information, so as to realize the detection, tracking, and identification of the target object.

[0056] The laser radar system and the optical system thereof provided by the application have different phases of the detection light modulated by the phase modulators of different groups, and the phase demodulator only demodulates the phase of the detection light modulated by the phase modulator of the same group, so that the light emitters and the light detectors of the same group can be accurately aligned without manual alignment during the assembly of the light source module and the laser radar system, thereby improving the production efficiency of the laser radar and reducing the assembly cost.

[0057] The various embodiments described in this specification are intended to be illustrative of the invention and do not limit the scope of the invention. Although specific embodiments have been described herein, they are not to be taken as the only embodiments of the invention. Various modifications can be made to the embodiments described and other embodiments can be used without departing from the spirit or scope of the invention. Accordingly, the scope of the invention is to be limited only by the claims.

Claims

1. An optical system characterized by comprising: The device group comprises a light emitter, a light detector, a phase modulator and a phase demodulator. The phase modulator is located at the light outlet of the light emitter in the same group, and is used for phase modulating the probe light emitted by the light emitter so that the modulated probe light irradiates on the target object. The phase demodulator is located at the light inlet of the light detector in the same group, and is used for phase demodulating the probe light reflected by the target object so that the phase demodulated probe light irradiates on the light detector. The phase modulators in different groups have different phases, and the phase demodulator only demodulates the probe light phase-modulated by the phase modulator in the same group. The light beam emitted by the light emitter is a Gaussian light beam, which is converted into spiral phase light after being modulated by the phase modulator. The spiral phase light is converted into Gaussian light after being demodulated by the phase demodulator. The phase modulator comprises an orbital angular momentum modulator. The phase demodulator comprises an orbital angular momentum demodulator. The phase distribution of the orbital angular momentum modulator and the orbital angular momentum demodulator in the same device group is opposite.

2. The optical system of claim 1, wherein The absolute value of the topological quantum number of the orbital angular momentum demodulator and the orbital angular momentum modulator in the same group is equal but opposite.

3. The optical system of claim 1, wherein The topological quantum numbers of the orbital angular momentum modulators in different device groups are different. The phase modulator is a spatial light modulator, the phase demodulator is a spatial light modulator, and the topological quantum number of the spiral phase distribution of the phase modulator in one group is l=+4.

4. The optical system of claim 3, wherein The topological quantum number of the spiral phase distribution of the corresponding phase demodulator is l=-4.

5. The optical system of claim 3, wherein The topological quantum numbers of the orbital angular momentum modulators in different device groups are different, including:

6. The optical system of claim 3, wherein The absolute value of the topological quantum number of the orbital angular momentum modulators in different device groups is equal but opposite. The absolute value of the topological quantum number of the orbital angular momentum modulators in different device groups is not equal but the same in sign. The orbital angular momentum modulator is a first spiral phase step plate, the orbital angular momentum demodulator is a second spiral phase step plate, the absolute value of the topological quantum number of the first spiral phase step plate and the second spiral phase step plate in the same device group is equal but opposite, and the topological quantum numbers of the first spiral phase step plates in different device groups are different. The orbital angular momentum modulator is a first spatial light modulator, the orbital angular momentum demodulator is a second spatial light modulator, the absolute value of the topological quantum number of the first spatial light modulator and the second spatial light modulator in the same device group is equal but opposite, and the topological quantum numbers of the first spatial light modulators in different device groups are different. The orbital angular momentum modulator is a first subwavelength grating, the orbital angular momentum demodulator is a second subwavelength grating, the absolute value of the topological quantum number of the first subwavelength grating and the second subwavelength grating in the same device group is equal but opposite, and the topological quantum numbers of the first subwavelength gratings in different device groups are different.

7. The optical system of claim 2, wherein Also included is an optical stop between the phase demodulator and the optical detector.

8. A lidar system, comprising: An optical system comprising the optical system of any of claims 1-7.

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