High-sensitivity single-photon detection system for high-precision ozone profile detection

Abstract

The invention discloses a high-sensitivity single-photon detection system for high-precision ozone profile detection, and the system is characterized in that signal light collected by a telescope enters a micropore diaphragm compression receiving field of view, then passes through a dichroic mirror and is divided into first signal light and second signal light with different wavelengths, the first signal light passes through a first lens and is changed into parallel light, and the parallel light passes through a second lens; the optical signals reach a first high-sensitivity detector through a first narrow-band filter and a first F-P etalon, the first high-sensitivity detector converts the optical signals into electric pulse signals, and a first high-speed pulse counting unit collects the electric pulse signals and uploads the electric pulse signals to an upper computer for processing; the second signal light is emitted through a second light path similar to the first signal light. Through the background light suppression structure, the high-sensitivity detector and the high-speed pulse counting unit, background noise is reduced, the signal-to-noise ratio of the system is improved, and high-sensitivity single-photon detection for high-precision ozone profile detection is realized.

Description

Technical Field

[0001] The invention belongs to the field of atmosphere detection, and in particular relates to a highly sensitive single-photon detection system for high-precision ozone profile detection. Background Art

[0002] More than 90% of the ozone in the Earth's atmosphere is in the stratosphere, about 25 km above the ground. The stratospheric ozone layer absorbs all solar ultraviolet radiation in the 210-290 nm band, thereby protecting life on Earth from the effects of strong ultraviolet radiation. The remaining ozone is mostly in the troposphere. Ozone is a typical secondary pollutant that does not come from direct pollution emissions. It is the product of photochemical reactions between volatile organic compounds (VOCs) and nitrogen oxides (NOx) under sunlight.

[0003] The main ground-based measurement methods for ozone include iodine titration, ultraviolet absorption, chemiluminescence, and differential absorption spectroscopy (DOAS), but these methods are single-point measurements and cannot perform profile detection. Differential absorption lidar is an effective active remote sensing device for detecting the vertical distribution of atmospheric ozone. Its advantages are mainly high spatial resolution and temporal resolution, and it can perform continuous long-term real-time vertical observations. However, the accuracy of differential absorption lidar is limited by the accuracy of signal detection. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a high-sensitivity single-photon detection system for high-precision ozone profile detection. Through a background light suppression structure, a high-sensitivity detector and a high-speed pulse counting unit, high-sensitivity single-photon detection for high-precision ozone profile detection is achieved.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A highly sensitive single-photon detection system for high-precision ozone profile detection, the system comprising a telescope, a micro-aperture diaphragm, a dichroic mirror, a first lens, a first narrow-band filter, a first FP etalon, a first highly sensitive detector, a first high-speed pulse counting unit, a second lens, a second narrow-band filter, a second FP etalon, a second highly sensitive detector, and a second high-speed pulse counting unit, wherein:

[0007] The signal light collected by the telescope enters the micro-aperture diaphragm to compress the receiving field of view, and then passes through the dichroic mirror to be divided into the first and second signal lights of different wavelengths. The first signal light becomes parallel light after passing through the first lens, and reaches the first high-sensitivity detector through the first narrow-band filter and the first FP standard tool. The first high-sensitivity detector converts the optical signal into an electrical pulse signal, which is collected by the first high-speed pulse counting unit and uploaded to the host computer for processing; the second signal light becomes parallel light after passing through the second lens, and reaches the second high-sensitivity detector through the second narrow-band filter and the second FP standard tool. The second high-sensitivity detector converts the optical signal into an electrical pulse signal, which is collected by the second high-speed pulse counting unit and uploaded to the host computer for processing.

[0008] Furthermore, the operating wavelengths of the first and second signal lights with different wavelengths are 310 nm and 355 nm respectively.

[0009] Furthermore, the micropore diameter of the micropore aperture is 0.3 mm.

[0010] Furthermore, the bandwidths of the first and second narrowband filters are both 0.3 nm.

[0011] Furthermore, the first and second high-sensitivity detectors are both single-photon detectors.

[0012] Furthermore, the pulse counting frequencies of the first and second high-speed pulse counting units are both 50 MHz.

[0013] The beneficial effects of the present invention are:

[0014] The present invention reduces background noise, improves the system signal-to-noise ratio, and realizes high-sensitivity single-photon detection for high-precision ozone profile detection through a background light suppression structure, a high-sensitivity detector, and a high-speed pulse counting unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a structural block diagram of a highly sensitive single-photon detection system for high-precision ozone profile detection according to the present invention.

[0016] Reference numerals:

[0017] 1. Telescope, 2. Micro-aperture diaphragm, 3. Dichroic mirror, 4. First lens, 5. First narrow-band filter, 6. First FP etalon, 7. First high-sensitivity detector, 8. First high-speed pulse counting unit, 9. Second lens, 10. Second narrow-band filter, 11. Second FP etalon, 12. Second high-sensitivity detector, 13. Second high-speed pulse counting unit. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0019] The working wavelengths used by the ozone profile detection laser radar are 310nm and 355nm, which are within the solar spectrum. The solar background light during daytime measurements has a great impact on detection. The present invention reduces the impact of background noise and improves the signal-to-noise ratio through a background light suppression structure. This function is achieved by combining an aperture and a filter. The microaperture aperture 2 is used to compress the receiving field of view so that the sky background light received by the telescope 1 is minimized. The microaperture diameter of the microaperture aperture 2 is 0.3mm. In order to extract the backscattered light signal from the strong sky background radiation and thus achieve a certain detection signal-to-noise ratio, a combination of two narrow-band filters and two FP standard tools is used to greatly suppress non-working wavelength signals, that is, to effectively suppress background light. The bandwidth of the two filters is 0.3nm, the free spectrum range of the two FP standard tools is 50GHz, and the stray suppression ratio is better than 10 -7 Magnitude.

[0020] In order to achieve accurate detection of the spatial distribution of ozone with high temporal and spatial resolution, the laser radar needs to reduce the pulse width of the detection pulse to below the nanosecond level and increase the spatial resolution to the meter level. The narrower the detection pulse width, the lower the backscatter signal power, so the laser radar needs a detector with high detection sensitivity. The first and second high-sensitivity detectors 7 and 12 of the present invention select high quantum efficiency photon detectors that can detect signals at the photon level and output pulse signals as the corresponding detected photons.

[0021] The first high-sensitivity detector 7 and the second high-sensitivity detector 12 perform photoelectric conversion on the scattered light signal of the laser radar, and the converted electrical pulse signal is collected by a high-speed pulse counting unit. Since the system high-sensitivity detector 7 and the high-sensitivity detector 12 are single-photon detectors, that is, the output of an electrical pulse signal represents the detection of a photon, a pulse counting method is used in the subsequent electrical signal measurement equipment. The pulse counting frequency of the two high-speed pulse counting units is 50MHz, corresponding to a laser radar spatial resolution of 3m.

[0022] Specifically, the structure of a high-sensitivity single-photon detection system for high-precision ozone profile detection of the present invention is as follows: Figure 1As shown, the micro-aperture diaphragm 2, the dichroic mirror 3, two lenses, two filters and two FP etalons form a background light suppression structure. The wavelength of the double differential laser radar for ozone profile detection is 310nm and 355nm. The signal light collected by the telescope 1 first enters the micro-aperture diaphragm 2, compresses the receiving field of view, and then passes through the dichroic mirror 3 to be divided into the first and second signal lights of 310nm and 355nm wavelengths. The first signal light becomes parallel light after passing through the first lens 4, and reaches the first high-sensitivity detector 7 through the first narrow-band filter 5 and the first FP etalon 6. The first high-sensitivity detector 7 converts the optical signal into an electrical pulse signal, which is collected by the first high-speed pulse counting unit 8 and uploaded to the host computer for processing; the second signal light becomes parallel light after passing through the second lens 9, and reaches the second high-sensitivity detector 12 through the second narrow-band filter 10 and the second FP etalon 11. The second high-sensitivity detector 12 converts the optical signal into an electrical pulse signal, which is collected by the second high-speed pulse counting unit 13 and uploaded to the host computer for processing.

[0023] The present invention realizes background light suppression through a combination of an aperture and a filtering method, reduces the influence of background noise, improves the signal-to-noise ratio, and further improves the ozone detection accuracy.

[0024] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A highly sensitive single-photon detection system for high-precision ozone profile detection, characterized in that: The system includes a telescope, a micro-aperture diaphragm, a dichroic mirror, a first lens, a first narrow-band filter, a first FP etalon, a first high-sensitivity detector, a first high-speed pulse counting unit, a second lens, a second narrow-band filter, a second FP etalon, a second high-sensitivity detector, and a second high-speed pulse counting unit, wherein: The signal light collected by the telescope enters the micro-aperture diaphragm to compress the receiving field of view, and then passes through the dichroic mirror to be divided into the first and second signal lights of different wavelengths. The first signal light becomes parallel light after passing through the first lens, and reaches the first high-sensitivity detector through the first narrow-band filter and the first FP standard tool. The first high-sensitivity detector converts the optical signal into an electrical pulse signal, which is collected by the first high-speed pulse counting unit and uploaded to the host computer for processing; the second signal light becomes parallel light after passing through the second lens, and reaches the second high-sensitivity detector through the second narrow-band filter and the second FP standard tool. The second high-sensitivity detector converts the optical signal into an electrical pulse signal, which is collected by the second high-speed pulse counting unit and uploaded to the host computer for processing.

2. A highly sensitive single photon detection system for high-precision ozone profile detection according to claim 1, characterized in that: The operating wavelengths of the first and second signal lights with different wavelengths are 310 nm and 355 nm respectively.

3. The highly sensitive single photon detection system for high-precision ozone profile detection according to claim 1, characterized in that: The micropore diameter of the micropore aperture is 0.3 mm.

4. The highly sensitive single photon detection system for high-precision ozone profile detection according to claim 1, characterized in that: The bandwidths of the first and second narrowband filters are both 0.3 nm.

5. The highly sensitive single photon detection system for high-precision ozone profile detection according to claim 1, characterized in that: The first and second high-sensitivity detectors are both single-photon detectors.

6. The highly sensitive single photon detection system for high-precision ozone profile detection according to claim 1, characterized in that: The pulse counting frequencies of the first and second high-speed pulse counting units are both 50 MHz.

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