An ozone laser radar transmitting system and laser transmitting method for isolating return light

Abstract

The present invention relates to the field of atmospheric ozone detection, and in particular to an ozone laser radar transmitting system and a laser transmitting method for isolating return light. The ozone laser radar transmitting system for isolating return light comprises a laser transmitter, which is used to emit a laser beam of an original wavelength; a wavelength converter, which is used to convert the laser beam of the original wavelength into a laser beam of a target wavelength; and an isolator, which is arranged between the laser transmitter and the wavelength converter, and is used to isolate the return light emitted to the laser transmitter. The ozone laser radar transmitting system for isolating return light proposed in the present invention achieves isolation of the return light by arranging an isolator between the laser transmitter and the wavelength converter, thereby avoiding damage to the laser transmitter by the return light. In addition, the radar transmitting system proposed in the present invention has a simple structure and can effectively reduce the length of the optical path.

Description

Technical Field

[0001] The invention relates to the field of atmospheric ozone detection, in particular to an ozone laser radar emission system and a laser emission method for isolating return light. Background Art

[0002] Although ozone plays an important role in protecting humans and the environment in the stratosphere, if its concentration increases in the troposphere, it will cause serious harm to humans, animal and plant growth and the ecological environment. It also plays an important role in tropospheric photochemistry, atmospheric environmental quality and ecological environment. Differential absorption lidar technology has become an effective means of detecting atmospheric ozone distribution due to its advantages such as high spatial resolution, fast real-time and large dynamic range.

[0003] At present, high-energy ultraviolet solid lasers are usually used to emit laser light sources, which are focused by focusing lenses and then pumped into gas (such as hydrogen, deuterium, CO2) Raman tubes to produce corresponding Raman lasers of different wavelengths. After collimation and beam expansion, Raman lasers and laser light sources are emitted into the atmosphere, attenuated by the atmosphere, scattered and absorbed by particles in the atmosphere, and differential absorption is formed by using the different degrees of absorption of Raman lasers of different wavelengths by ozone; after scattering and absorption by atmospheric particles and ozone, the backscattered laser is extinguished by the atmosphere again on the way back, and then received by the receiving optical system, converted by photoelectric detectors, and finally the echo signal is collected. The spatial distribution information of ozone concentration can be obtained using the differential absorption algorithm.

[0004] The ozone radar transmitting system based on solid-state laser as Raman pump source is easy to damage the lens due to the short wavelength (ultraviolet wavelength, 266nm) and high energy of the laser. In particular, in order to improve the efficiency of laser light source pumping gas Raman tube, it is usually necessary to use a focusing lens to focus the laser light source. Focused return light is easy to appear in the optical path. In addition, if the focal length of the focusing lens is not properly selected or its position is not properly placed, the return light can easily damage the laser. In order to avoid the influence of the return light focus on the laser, the optical path length is increased, resulting in a larger optical path structure and a larger overall device. Summary of the invention

[0005] In view of the defects in the prior art, the present invention provides an ozone laser radar transmitting system with isolated return light, aiming to overcome the problems existing in the prior art.

[0006] In order to achieve the above-mentioned purpose, in the first aspect, the present invention provides an ozone laser radar transmission system for isolating return light, the system comprising: a laser transmitter, the laser transmitter is used to emit a laser beam of an original wavelength; a wavelength converter, the wavelength converter is used to convert the laser beam of the original wavelength into a laser beam of a target wavelength; an isolator, the isolator is arranged between the laser transmitter and the wavelength converter, and the isolator is used to isolate the return light emitted to the laser transmitter. The ozone laser radar transmission system for isolating return light proposed by the present invention achieves isolation of the return light by arranging an isolator between the laser transmitter and the wavelength converter, thereby avoiding damage to the laser transmitter by the return light. In addition, the radar transmission system proposed by the present invention has a simple structure and can effectively reduce the length of the optical path.

[0007] Optionally, the isolator includes: a polarization beam splitter, which is arranged on the light-emitting side of the laser transmitter, and the polarization direction of the polarization beam splitter is the same as the polarization direction of the laser beam of the original wavelength; and a quarter-wave plate, which is arranged on the side of the polarization beam splitter away from the laser transmitter, and the quarter-wave plate is used to change the polarization direction of the return light so that the polarization direction of the return light is different from the polarization direction of the polarization beam splitter. The present invention can achieve effective isolation of the return light by changing the polarization direction of the return light to be different from the polarization direction of the polarization beam splitter, and the isolator is only composed of the polarization beam splitter and the quarter-wave plate, and its structure is simple and easy to implement.

[0008] Optionally, the ozone laser radar transmitting system for isolating return light further comprises: a first aperture, which is arranged between the laser transmitter and the polarization beam splitter. The present invention arranges an aperture on the light-emitting side of the laser transmitter to reasonably limit the laser beam.

[0009] Optionally, the ozone laser radar transmitting system for isolating return light further includes: a first plano-convex lens, the first plano-convex lens being arranged on a side of the quarter-wave plate away from the polarization beam splitter, the first plano-convex lens being used to focus the laser beam of the original wavelength to form a focused laser beam. The present invention focuses the laser beam of the original wavelength by arranging the first plano-convex lens, and can focus the laser beam to the center of the wavelength converter, which is more conducive to realizing wavelength conversion.

[0010] Optionally, the ozone laser radar transmitting system for isolating return light further includes: a first reflector, a second aperture and a second reflector, wherein the first reflector, the second aperture and the second reflector are respectively arranged between the first plano-convex lens and the wavelength converter. The present invention can effectively reduce the optical path and the volume of the ozone laser radar transmitting system by using the combination of the first reflector and the second reflector.

[0011] Optionally, the ozone laser radar transmitting system with isolated return light further includes: a beam expander, which is used to expand the laser beam of the original wavelength and the laser beam of the target wavelength and then emit them into the atmosphere. The present invention adopts a beam expander mainly for the purpose of expanding the diameter of the laser beam of the target wavelength and reducing the divergence angle of the laser beam of the target wavelength, which is more conducive to long-distance detection.

[0012] Optionally, the ozone lidar transmitting system for isolating return light also includes: a second plano-convex lens, which is arranged between the wavelength converter and the beam expander, and is used to collimate the divergent laser beam of the original wavelength and the laser beam of the target wavelength into parallel laser beams.

[0013] Optionally, the ozone laser radar transmitting system for isolating return light further includes: a third reflector and a fourth reflector, wherein the third reflector and the fourth reflector are arranged between the wavelength converter and the second plano-convex lens. The present invention can further reduce the optical path and the volume of the ozone laser radar transmitting system by using the third reflector and the fourth reflector.

[0014] Optionally, the laser emitting device includes a laser, the laser is used to emit a laser beam of an original wavelength, the original wavelength is 266nm; the wavelength converter includes a Raman tube, the laser beam of the original wavelength passes through the Raman tube to generate two laser beams of target wavelengths, the target wavelengths are 287nm and 299nm respectively. The advantage of the present invention by using a laser is that the technology is mature and easy to implement; in addition, a 266nm laser is used to pump the Raman tube to generate laser beams of wavelengths of 287nm and 299nm. Using this method to generate Raman lasers is relatively direct, simple, reliable and safe.

[0015] In the second aspect, based on the same inventive concept, the present invention also provides a laser emission method, which includes: providing an ozone laser radar emission system with isolated return light, the ozone laser radar emission system with isolated return light is as described in the first aspect of the present invention; using the ozone laser radar emission system with isolated return light to emit a laser beam of a target wavelength into the atmosphere. The laser emission method adopted by the present invention mainly adopts an ozone laser radar emission system with the function of isolating return light, which specifically sets an isolator between the laser emitter and the wavelength converter to achieve isolation of the return light and avoid damage to the laser emitter by the return light. In addition, the radar emission system proposed by the present invention has a simple structure and can effectively reduce the length of the optical path. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of an embodiment of an ozone laser radar transmitting system for isolating return light of the present invention;

[0017] Figure 2 A flowchart of an embodiment of a laser emission method of the present invention;

[0018] In the figure, 1-laser emitter, 2-first aperture, 3-polarization beam splitter, 4-quarter wave plate, 5-first plano-convex lens, 6-first reflector, 7-second aperture, 8-second reflector, 9-wavelength converter, 10-third reflector, 11-fourth reflector, 12-second plano-convex lens, 13-beam expander, 14-atmosphere. DETAILED DESCRIPTION

[0019] The specific embodiments of the present invention will be described in detail below. It should be noted that the embodiments described herein are only for illustration and are not intended to limit the present invention. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present invention. However, it is obvious to those of ordinary skill in the art that these specific details do not need to be adopted to implement the present invention. In other examples, in order to avoid confusing the present invention, known circuits, software or methods are not specifically described.

[0020] Throughout the specification, references to "one embodiment", "an embodiment", "an example", or "an example" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment", "in an embodiment", "an example", or "an example" appearing in various places throughout the specification do not necessarily all refer to the same embodiment or example. In addition, particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combination and / or subcombination. In addition, it should be understood by those of ordinary skill in the art that the figures provided herein are for illustrative purposes and that the figures are not necessarily drawn to scale.

[0021] See also Figure 1 An embodiment of the present invention provides an ozone lidar transmitting system with isolated return light, the system comprising: a laser transmitter 1, the laser transmitter 1 is used to transmit a laser beam of original wavelength; in this embodiment, the laser transmitter 1 can be any device that can transmit a laser beam, the device can include but is not limited to a laser, the laser is used to transmit a laser beam of original wavelength, the original wavelength is 266nm; the advantage of the present invention by using a laser is that the technology is mature and easy to implement; in addition, it should be noted that the original wavelength can also be adjusted according to the actual detection scenario, and should not be limited to the situations listed in this article.

[0022] In this embodiment, the ozone laser radar transmitting system with isolated return light further includes a wavelength converter 9, which is used to convert the laser beam of the original wavelength into a laser beam of the target wavelength; the wavelength converter 9 includes a Raman tube, and part of the laser beam of the original wavelength passes through the Raman tube to generate two laser beams of target wavelengths, respectively, and the target wavelengths are 287nm and 299nm. In addition, a 266nm laser is used to pump the Raman tube to generate laser beams with wavelengths of 287nm and 299nm. This method of generating Raman lasers is relatively direct, simple, reliable and safe.

[0023] In this embodiment, the isolator of the ozone laser radar transmitting system for isolating return light is arranged between the laser transmitter 1 and the wavelength converter 9, and the isolator is used to isolate the return light emitted to the laser transmitter 1. The ozone laser radar transmitting system for isolating return light proposed in the present invention achieves isolation of return light by arranging an isolator between the laser transmitter 1 and the wavelength converter 9, thereby avoiding damage to the laser transmitter 1 by the return light. In addition, the radar transmitting system proposed in the present invention has a simple structure and can effectively reduce the length of the optical path.

[0024] In this embodiment, the isolator includes: a polarization beam splitter 3, which is arranged on the light-emitting side of the laser emitter 1, and the polarization direction of the polarization beam splitter 3 is the same as the polarization direction of the laser beam of the original wavelength; a quarter wave plate 4, which is arranged on the side of the polarization beam splitter 3 away from the laser emitter 1, and the quarter wave plate 4 is used to change the polarization direction of the return light so that the polarization direction of the return light is different from the polarization direction of the polarization beam splitter 3. The present invention can effectively isolate the return light by changing the polarization direction of the return light to be different from the polarization direction of the polarization beam splitter 3, and the isolator is only composed of the polarization beam splitter 3 and the quarter wave plate 4, and its structure is simple and easy to implement.

[0025] In the actual application process, the laser beam of the original wavelength emitted by the laser emitter 1 can be linearly polarized and the polarization direction is fixed. In this embodiment, the polarization direction can be horizontal, and in one or some other embodiments, the polarization direction can also be vertical. The present invention can place a polarization beam splitter 3 at an appropriate position on the light path of the light-emitting side of the laser emitter 1, and ensure that the polarization direction of the laser beam of the original wavelength corresponds to the laser polarization direction of the polarization beam splitter 3, so that the laser beam of the original wavelength can pass efficiently; and the direction perpendicular to the polarization direction of the laser beam of the original wavelength will be reflected; the linearly polarized laser beam of the original wavelength becomes circularly polarized after passing through the quarter-wave plate 4 at an appropriate angle, that is, the beams propagating thereafter are all circularly polarized. Once the laser beam is affected by the subsequent light path to generate return light, the return light will pass through the quarter-wave plate 4. Its polarization direction will be perpendicular to the laser polarization direction, and thus be reflected to other directions by the polarization beam splitter 3. This simple isolator separates polarized light and controls the polarization direction of the laser, ensuring that the light is emitted while reflecting the return light in another direction, thereby avoiding the impact of the return light on the laser. In terms of cost, this is simpler and cheaper than the isolator using optical rotation. In addition, this device is easy to select with a higher damage threshold to reduce the possibility of damage.

[0026] In an optional embodiment, the ozone laser radar transmitting system for isolating return light further includes: a first aperture 2, which is arranged between the laser transmitter 1 and the polarization beam splitter 3. The present invention aims to reasonably limit the laser beam by arranging an aperture on the light-emitting side of the laser transmitter 1. Furthermore, the first aperture 2 can be any type and model of aperture, and the specific selection can be selected according to the actual use situation, which will not be described in detail here.

[0027] In an optional embodiment, the ozone laser radar transmitting system for isolating return light further includes: a first plano-convex lens 5, the first plano-convex lens 5 is arranged on the side of the quarter-wave plate 4 away from the polarization beam splitter 3, and the first plano-convex lens 5 is used to focus the laser beam of the original wavelength to form a focused laser beam. The present invention focuses the laser beam of the original wavelength by setting the first plano-convex lens 5, and can focus the laser beam to the center of the wavelength converter 9, which is more conducive to wavelength conversion. When selecting the first plano-convex lens 5, the following must be met: 1. Meet the requirements of Raman conversion and select according to the actual laser parameters and Raman tube selection; 2. Take into account the size and placement of the laser to ensure that the laser is within the focal length range of the lens, avoid the return light from forming a real focus through this focusing lens to the inside of the laser, thereby avoiding damage to the laser; this also makes the overall optical path structure more compact.

[0028] In an optional embodiment, the ozone laser radar transmitting system for isolating return light further includes: a first reflector 6, a second aperture 7, and a second reflector 8, wherein the first reflector 6, the second aperture 7, and the second reflector 8 are respectively arranged between the first plano-convex lens 5 and the wavelength converter 9. The present invention can effectively reduce the optical path and the volume of the ozone laser radar transmitting system by using the combination of the first reflector 6 and the second reflector 8.

[0029] In an optional embodiment, the ozone laser radar transmitting system with isolated return light further includes: a beam expander 13, the beam expander 13 is used to expand the laser beam of the original wavelength and the laser beam of the target wavelength (laser beams of three wavelengths of 266nm, 287nm, and 299nm) and then emit them into the atmosphere 14. The main purpose of the present invention by using the beam expander 13 is to expand the diameter of the laser beam of the target wavelength and reduce the divergence angle of the laser beam of the target wavelength, which is more conducive to long-distance detection. Furthermore, the beam expander 13 can use a triple beam expander 13, and ensure that the entrance pupil size of the beam expander matches the diameter of the laser beam of the target wavelength entering; the present invention adopts the beam expander 13 not only to improve the efficiency of collimation, but also to expand the size of the laser beam, which is more conducive to reducing the energy density of the laser.

[0030] In an optional embodiment, the ozone laser radar transmitting system for isolating return light further includes: a second plano-convex lens 12, the second plano-convex lens 12 is arranged between the wavelength converter 9 and the beam expander 13, and the second plano-convex lens 12 is used to collimate the laser beam of the original wavelength and the laser beam of the target wavelength in a divergent state into parallel laser beams. It should be noted that the selection of the second plano-convex lens 12 can refer to the first plano-convex lens 5, and will not be repeated here for the sake of brevity.

[0031] In an optional embodiment, the ozone laser radar transmitting system for isolating the return light further includes: a third reflector 10 and a fourth reflector 11, wherein the third reflector 10 and the fourth reflector 11 are arranged between the wavelength converter 9 and the second plano-convex lens 12. The present invention can further reduce the optical path and the volume of the ozone laser radar transmitting system by using the third reflector 10 and the fourth reflector 11. Figure 1 The present invention adopts a combination of a first reflector 6, a second reflector 8, a third reflector 10 and a fourth reflector 11 to make the overall optical path of the ozone laser radar transmitting system of the return light S-shaped. The above design can effectively reduce the volume of the laser radar transmitting system.

[0032] See also Figure 2 Based on the same inventive concept, the present invention also provides a laser emitting method, which comprises:

[0033] S1. Provide an ozone laser radar transmission system that isolates return light;

[0034] S2. Utilize the ozone laser radar transmitting system with isolated return light to transmit a laser beam of a target wavelength into the atmosphere.

[0035] In this embodiment, the ozone laser radar transmitting system with isolated return light is as described in the relevant embodiments of the ozone laser radar transmitting system with isolated return light in the present invention. The laser transmitting method adopted in the present invention mainly adopts an ozone laser radar transmitting system with the function of isolating return light, which specifically arranges an isolator between the laser transmitter and the wavelength converter to achieve the isolation of the return light and avoid the damage of the return light to the laser transmitter. In addition, the radar transmitting system proposed in the present invention has a simple structure and can effectively reduce the length of the optical path. The specific system composition and beneficial effects of the ozone laser radar transmitting system with isolated return light can also be referred to the above description, so it will not be repeated here.

[0036] In addition, the laser emitter involved in the present invention can also be applied to the field of ozone distribution detection; wherein, the detection of ozone distribution also includes the reception of echo signals, and the echo signals are obtained by backscattering of laser beams of three wavelengths of 266nm, 287nm, and 299nm through the atmosphere. Furthermore, a telescope can be used to receive the echo signals. It should be noted that the other steps and detailed calculation methods of the method for ozone distribution detection not involved in the present invention are not the core invention points of the present invention, and therefore are not recorded in the application documents. For details, please refer to the existing differential absorption lidar detection technology.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. An ozone laser radar transmitting system with isolated return light, characterized in that: include: A laser transmitter, the laser transmitter being used to emit a laser beam of an original wavelength; A wavelength converter, wherein the wavelength converter is used to convert the laser beam of the original wavelength into a laser beam of a target wavelength; an isolator, the isolator being disposed between the laser emitter and the wavelength converter, the isolator being used to isolate the return light emitted to the laser emitter; The isolator comprises: A polarization beam splitter, which is arranged on the light-emitting side of the laser emitter, and the polarization direction of the polarization beam splitter is the same as the polarization direction of the laser beam of the original wavelength; A quarter wave plate, the quarter wave plate is arranged on a side of the polarization beam splitter away from the laser emitter, and the quarter wave plate is used to change the polarization direction of the return light so that the polarization direction of the return light is different from the polarization direction of the polarization beam splitter; The ozone laser radar transmitting system for isolating return light also includes: A first aperture, wherein the first aperture is disposed between the laser emitter and the polarization beam splitter; The ozone laser radar transmitting system for isolating return light also includes: A first plano-convex lens, which is disposed on a side of the quarter-wave plate away from the polarization beam splitter, and is used to focus the laser beam of the original wavelength to form a focused laser beam; The ozone laser radar transmitting system for isolating return light also includes: a first reflector, a second aperture, and a second reflector, wherein the first reflector, the second aperture, and the second reflector are respectively arranged between the first plano-convex lens and the wavelength converter; The ozone laser radar transmitting system for isolating return light also includes: A beam expander, which is used to expand the laser beam of the original wavelength and the laser beam of the target wavelength and then emit them into the atmosphere; The laser transmitter is used to emit a laser beam of an original wavelength, and the original wavelength is 266nm; The wavelength converter comprises a Raman tube. After the laser beam of the original wavelength passes through the Raman tube, two laser beams of target wavelengths are generated respectively. The target wavelengths are 287 nm and 299 nm respectively.

2. The ozone laser radar transmitting system with isolated return light according to claim 1, characterized in that: The ozone laser radar transmitting system for isolating return light also includes: A second plano-convex lens is disposed between the wavelength converter and the beam expander, and is used for collimating the laser beam of the original wavelength and the laser beam of the target wavelength in a divergent state into parallel laser beams.

3. The ozone laser radar transmitting system with isolated return light according to claim 2 is characterized in that: The ozone lidar transmission system with isolated return light also includes: A third reflector and a fourth reflector are arranged between the wavelength converter and the second plano-convex lens.

4. A laser emitting method, characterized in that: include: An ozone laser radar transmitting system with isolated return light is provided, wherein the ozone laser radar transmitting system with isolated return light is as described in any one of claims 1 to 3; The ozone laser radar transmitting system with isolated return light is used to transmit a laser beam of a target wavelength into the atmosphere.

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