A Differential Optical Absorption Spectroscopy Measurement System Based on Off-Axis Parabolic Mirror

Abstract

The invention provides a differential optical absorption spectroscopy (DOAS) measurement system based on an off-axis paraboloid mirror. The DOAS measurement system comprises an off-axis paraboloid mirror (center punched) telescope, a light source (LED) device, a light source coupling lens, a light source collimating lens, a corner reflector, an optical fiber and a spectrograph detector. Light emitted from the light source device is coupled by a lens to enter the optical fiber, enters atmosphere through a small hole in the center of the off-axis paraboloid mirror after being collimated by the collimating mirror, returns the off-axis paraboloid mirror telescope after being reflected by the corner reflector through a certain distance of transmission, enters a receiving optical fiber through off-axis convergence and coupling and transmitted to the spectrograph, and is received by the detector after being split by the spectrograph, thereby being subjected to post-stage spectrum analysis. Compared with a conventional DOAS system, the DOAS measurement system provided by the invention has the advantages that the receiving efficiency of the telescope is increased, and the system is simplified to ensure that receiving an optical signal and emitting an optical signal are separated to facilitate the system adjustment through designing a simple structure inside the telescope.

Description

technical field [0001] The invention belongs to the field of optical measurement, in particular to a differential absorption spectrum system based on an off-axis parabolic mirror for transmitting and receiving, which is applied to monitor atmospheric trace pollution gases. Background technique [0002] Spectral analysis technology can use different molecules to perform qualitative and quantitative measurements of the characteristic absorption of light radiation in the wavelength band. Information such as the composition and concentration of a substance can be obtained by analyzing its absorption spectrum. This technology is widely used in the fields of atmospheric toxic and harmful gas monitoring and water body monitoring. DOAS technology is a non-contact and open optical path measurement method for trace gas detection. Its basic principle is to use the narrow-band absorption characteristics of different gas molecules to light radiation to identify gas components, and to in...

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Problems solved by technology

This kind of optical fiber transceiver integrated system has the following problems in actual measurement: usually the experiment is the outer core transmits and the inner core receives. The receiving part of the common end of the transceiver fiber is designed at the focus position of the main mirror of the telescope, while the transmitting part is at the defocused position. , this will cause part of the light to irradiate the main mirror of the telescope, not to be transmitted in the atmosphere but directly reflected back to the receiving end, thereby increasing the stray light inside the telescope; at the same time, the emitted part is out of focus, and the outgoing light is not parallel light, so part of the light cannot pass through The return of the corner reflector reduces the optical efficiency; since the transmitting end and the receiving end are located on the same end face of the optical fiber, it is difficult to directly observe the return spot of the atmosphere, and the system adjustment is troublesome

Since the rear end of the emitting fiber is similar to the DOAS structure of the optical fiber transceiver integrated Cassegrain telescope, the system also suffers from stray light and reduced light efficiency due to the off-focus of the emitting part and the difficulty of directly observing the return spot of the atmosphere. It is troublesome to adjust the system. question

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