Remote detection method and remote detection device for gaseous substances in the atmosphere by a DIAL system equipped with two lasers

Abstract

A device for remotely detecting atmospheric gaseous substances using a DIAL system with two lasers is disclosed. The device includes a first laser (1) and a second laser (2), with a semi-transparent mirror (3) positioned at the intersection of the axes of the laser beams. The semi-transparent mirror merges the two laser beams to output first and second combined beams containing 50% of the power of the laser beam from the first laser (1) and 50% of the power of the laser beam from the second laser (2). A total reflection mirror (5) is positioned downstream of the semi-transparent mirror (3), and the first merged beam passes through a first aperture (4) located in a first direction from the semi-transparent mirror (3), and the second merged beam passes through a second aperture (6) located in a second direction after being reflected from the total reflection mirror (5), so that the first and second merged beams are directed toward the same target. A corresponding method is also disclosed.

Description

Technical Field

[0001] The present invention relates to a method for remotely detecting gaseous substances in the atmosphere by a DIAL system equipped with two lasers, and to the construction of a device for remotely detecting gaseous substances in the atmosphere by a DIAL (Differential Absorption LIDAR) technique equipped with two lasers. The present invention belongs to the field of laser systems.

Background Art

[0002] The so-called "classical" configuration of a DIAL system equipped with two lasers has a single output aperture, and the laser beams from both lasers are made coaxial by a semi-transparent mirror and merged. Therefore, the laser light from both lasers propagates through the same volume in the atmosphere and towards a target (object) located at the end of a specific measurement path. An obvious drawback of this arrangement is that 50% of the energy from the lasers is lost due to the merging of the beams (however, this 50% of the energy is used for system synchronization and measurement of the emitted energy). As a result, the range of the remote detector is reduced by about 70%, which has an adverse effect on the remote detector. Also, if the output aperture is accidentally blocked, such a DIAL system will malfunction.

[0003] There is a configuration of a DIAL system with two lasers and two output apertures. In this case, each laser has a separate output aperture. In fact, for example, DD-CWA systems and F4G systems operate based on this configuration. As a result, the laser emission from one laser propagates to a target over a certain distance through a different volume of the atmosphere than the emission from the other laser. The laser beams gradually overlap but usually coincide up to about 50% on the way to the target. The optical effects of the atmosphere, differences in aerosol content, and differences in the concentration of the detected substances of one laser and the other at the initial stage of the measurement path can also basically have an adverse effect on the minimum detectable concentration. If one of such DIAL output apertures is accidentally closed for a short time, it may cause false detection or prevent the detection of the true cloud of the substance to be detected.

Summary of the Invention

[0004] The method for remotely detecting gaseous substances in the atmosphere by a DIAL system with two lasers according to the present invention substantially eliminates these drawbacks. Its essence is as follows. In this method, the laser beam generated by the first laser impinges on a semi-transparent mirror, 50% of the output of the laser beam passes through the semi-transparent mirror and proceeds towards the target through the first aperture (opening), and at the same time, the remaining 50% of the output of the laser beam is reflected from the semi-transparent mirror and impinges on a total reflection mirror, is reflected from the total reflection mirror and is directed towards the same target through the second aperture (opening), the delayed laser beam generated by the second laser impinges on the semi-transparent mirror, 50% of the output of the laser beam passes through the semi-transparent mirror, impinges on the total reflection mirror and is reflected, and is directed towards the same target through the second aperture, and at the same time, the remaining 50% of the output of the laser beam is reflected from the semi-transparent mirror and proceeds towards the same target through the first aperture.

[0005] Basically, the laser beams from both lasers converge at a semi-transparent mirror, each beam is split into two, each laser beam carrying 50% of the energy from the first laser and 50% of the energy from the second laser, and both beams are directed parallel to the target, one by the semi-transparent mirror and the other by the total reflection mirror.

[0006] The method for remotely detecting gaseous substances in the atmosphere by a DIAL system equipped with the above two lasers can be used in the apparatus for remotely detecting gaseous substances in the atmosphere according to the present invention. Its essence is as follows. This apparatus includes a first laser and a second laser. A semi-transparent mirror is disposed at the intersection of the axes of their laser beams. Behind the semi-transparent mirror, a total reflection mirror is disposed in front of the traveling direction of the laser beam generated by the second laser and in the reflection direction from the semi-transparent mirror in the traveling direction of the laser beam generated by the first laser. A first aperture is disposed in front of the semi-transparent mirror in the traveling direction of 50% of the laser beam from the first laser and in the traveling direction of 50% of the reflected laser beam from the second laser. A second aperture is disposed in the reflection direction of the total reflection mirror in the traveling direction of 50% of the laser beam from the first laser and in the traveling direction of 50% of the laser beam from the second laser.

[0007] The advantages of the remote detection method of gaseous substances in the atmosphere by a DIAL system equipped with two lasers according to the present invention and the structure of the remote detection device for gaseous substances in the atmosphere are obvious from the externally appearing effects. The originality of this solution means that while using a semi-transparent mirror to merge the beams from both lasers, each beam is split into two, each carrying 50% of the energy from the first laser and the second laser, and both beams are directed parallel to the target, resulting in no 50% loss of the laser energy, and thus no reduction in the DIAL range. This is also brought about by the fact that the laser emissions from both lasers pass through the same volume of the atmosphere. Such a configuration of the DIAL system with two lasers that split the laser beam into two minimizes the external influence due to the effect of the atmosphere on detection and ensures the maximum detection range. The solution means with two output apertures also brings other advantages. One is the advantage that even when one of the apertures is completely blocked, the reach of the system decreases, but the detection ability and DIAL sensitivity are maintained. The second advantage is that by splitting the laser beam into two, it is possible to reduce the power density of the output aperture and enhance visual safety.

Brief Description of the Drawings

[0008]

Figure 1

Embodiments for Carrying Out the Invention

[0009] In this example of a particular embodiment of the subject matter of the present invention, a solution to a method for remotely detecting gaseous substances in the atmosphere by a DIAL system equipped with two lasers according to the present invention will be described. The remote detection method of the present invention is applicable to a remote detection device for detecting gaseous substances in the atmosphere. This method is based on the following facts. A laser beam generated by a first laser impinges on a semi-transparent mirror, 50% of the output of the laser beam passes through the semi-transparent mirror and travels towards a target through a first aperture (opening), and at the same time, the remaining 50% of the output of the laser beam is reflected from the semi-transparent mirror and impinges on a total reflection mirror, is reflected from the total reflection mirror and directed towards the same target through a second aperture (opening), and a delayed laser beam generated by a second laser impinges on the semi-transparent mirror, 50% of the output of the laser beam passes through the semi-transparent mirror, impinges on the total reflection mirror and is reflected, and is directed towards the same target through the second aperture, and at the same time, the remaining 50% of the output of the laser beam is reflected from the semi-transparent mirror and travels towards the same target through the first aperture.

[0010] In this example of a particular embodiment of the subject matter of the present invention, a solution to a method for remotely detecting gaseous substances in the atmosphere according to the present invention as shown in the figure will be described. This solution includes a first laser 1 and a second laser 2, a semi-transparent mirror 3 is disposed at the intersection of the axes of their laser beams, and behind the semi-transparent mirror 3, a total reflection mirror 5 is disposed in front of the direction of travel of the laser beam generated by the second laser 2 and in the reflection direction from the semi-transparent mirror 3 of the direction of travel of the laser beam generated by the first laser 1, a first aperture 4 is disposed in front of the semi-transparent mirror 3 in the direction of travel of 50% of the laser beam from the first laser 1 and in the direction of travel of 50% of the laser beam reflected from the second laser 2, and a second aperture 6 is disposed in the reflection direction of the total reflection mirror 5 in the direction of travel of 50% of the laser beam from the first laser 1 and in the direction of travel of 50% of the laser beam from the second laser 2. This device is complemented by a light receiver 7 for the reflected laser beam.

[0011] (Industrial Applicability) The method for remotely detecting gaseous substances in the atmosphere by a DIAL system using two lasers and the apparatus for remotely detecting gaseous substances in the atmosphere can be used in the application of laser technology.

Claims

1. A method for remotely detecting gaseous substances in the atmosphere by a DIAL system equipped with two lasers, wherein the laser beam generated by the first laser (1) collides with the semi-transparent mirror (3), 50% of the output of the laser beam passes through the semi-transparent mirror (3) and travels towards the target through the first aperture (4), and at the same time, the remaining 50% of the output of the laser beam is reflected from the semi-transparent mirror (3) and collides with the total reflection mirror (5), is reflected from the total reflection mirror and directed towards the same target through the second aperture (6), the delayed laser beam generated by the second laser collides with the semi-transparent mirror (3), 50% of the output of the laser beam passes through the semi-transparent mirror (3), collides with the total reflection mirror (5) and is reflected, and is directed towards the same target through the second aperture (6), and at the same time, the remaining 50% of the output of the laser beam is reflected from the semi-transparent mirror (3) and travels towards the same target through the first aperture (4). A method characterized by the above.

2. A remote detection device for gaseous substances in the atmosphere by a DIAL system equipped with two lasers, including a first laser (1) and a second laser (2), and a semi-transparent mirror (3) is arranged at the intersection of the axes of their laser beams. A total reflection mirror (5) is arranged in front of the semi-transparent mirror (3) in the traveling direction of the laser beam generated by the second laser (2) passing through the semi-transparent mirror (3) and in the traveling direction of the laser beam generated by the first laser (1) reflected by the semi-transparent mirror (3). A first aperture (4) is arranged in front of the semi-transparent mirror (3) in the traveling direction of 50% of the laser beam transmitted through the semi-transparent mirror (3) from the first laser (1) and in the traveling direction of 50% of the laser beam reflected by the semi-transparent mirror (3) from the second laser (2). A second aperture (6) is arranged in front of the total reflection mirror (5) in the traveling direction of 50% of the laser beam reflected by the semi-transparent mirror (3) from the first laser (1) and then reflected by the total reflection mirror (5) and in the traveling direction of 50% of the laser beam transmitted through the semi-transparent mirror (3) from the second laser (2) and then reflected by the total reflection mirror (5). The device is characterized by the above.

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