Optical path folding device

Abstract

The invention provides an optical path folding device. Based on the confocal optical system consisting of a beam input end, an output end, a main plane mirror and a concave mirror, a tilted sub-mirroris introduced on the focal plane to change the reflection angle of the incident light beam, thereby achieving multiple reflections of the light beam in the confocal optical system. The output beam maintains the optical characteristics of the input beam and has a higher optical path volume ratio. Variable optical path can be achieved by rotating the tilted sub-mirror. Parallel input of multiple beams can be realized by adopting a fiber array collimator at the input end. A fiber array collimator is used at the input and output ends, and a part of the pigtail fiber is connected, so that the optical path can be connected in series to achieve a longer optical path.

Description

technical field [0001] The invention relates to an optical path folding device in the field of optical sensing, in particular to an optical path folding device used for gas optical sensing and variable optical path. Background technique [0002] In a limited volume, multiple reflections of the light beam are realized, so that the light beam travels through a relatively long optical path. Such optical devices have important applications in the field of optical sensing, especially for the sensing and analysis of special gases. [0003] At present, semiconductor tunable laser absorption spectroscopy (hereinafter referred to as TDLAS) and Fourier transform infrared spectroscopy (hereinafter referred to as FTIR) are two mainstream technical routes. The former is mainly based on tunable laser for spectral analysis in the near-infrared band, and the latter Spectral analysis was performed in the mid-to-far infrared by Fourier transform using a broad-spectrum light source. [0004] ...

AI Technical Summary

Problems solved by technology

[0007] With the improvement of the industry's requirements for gas detection accuracy, the requirements for optical path gas chambers have also been further improved. It is necessary to achieve a longer optical path (more than 20 meters, or even more than 100 meters) in a limited volume. The Herriott chamber and White Chamber are difficult to achieve more reflections in a certain volume

There are many improved designs based on the Heriott chamber and the White chamber, such as the astigmatic lens proposed by Heriot himself to achieve more reflections ("Folded Optical Delay Lines", Appl.Opt., Vol.4, No.8, pp883-889, 1965), but there is a problem that the astigmatism lens is difficult to process, although there is a follow-up to reduce the machining accuracy requirements by rotating an astigmatism lens (US Patent 5291265, 1994), the astigmatism lens is still not solved High processing cost; Joel.A.Silver et al. proposed to use double cylinder mirrors to achieve dense spot distribution, that is, more reflections (US Patent 7477377, 2009), but due to the non-rotational symmetry of the double cylinders, the beam After multiple reflections, it no longer has the same beam characteristics as the input beam, and cannot be applied in application scenarios that require the maintenance of beam characteristics (beam radius, divergence half angle, etc.)

Although there are also some improved schemes based on the White chamber, such as the Chinese patent "folded multiple light path multi-pass gas cell" (CN102053063B), a corner reflector is used at the output end of the White chamber to reflect the output beam so that it returns along the original path (deviating from one small angle), the optical path is doubled, but the input and output ends are too close, requiring more space to separate the input and output beams; at the same time, the White chamber uses an angled secondary mirror, and after the beam is reflected many times, the aberration has no effect on the output The influence of the beam characteristics is large

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