Light measuring device and method of manufacturing light measuring device

#The present disclosure relates to a light measuring device and a method of manufacturing a light measuring device.

#This application claims the benefit of priorities from Japanese Patent Application No. 2022-135666, filed on Aug. 29, 2022, Japanese Patent Application No. 2023-89901, filed on May 31, 2023, and Japanese Patent Application No. 2023-118229, filed on Jul. 20, 2023, the entire contents of which are incorporated herein by reference.

#Since strong absorption derived from the fundamental vibration of molecules is observed in mid-infrared light (wavelength of 3 μm to 20 μm), the mid-infrared light is used for absorption spectroscopy (spectroscopic measurement) targeting gas molecules. As disclosed in Non-Patent Document 1 (Donald R. Herriott and Harry J. Schulte, “Folded Optical Delay Lines”, Applied Optics vol. 4, pp. 883 to 889, Aug. 1, 1965), as a technique for improving the sensitivity of the above-described absorption spectroscopy, there is known a technique called a Herriott cell in which two concave mirrors are disposed to face each other and light is multiply reflected between the two concave mirrors to realize a long optical path.

#FIG. 1 is a schematic perspective view of a spectrometer of a first embodiment.

#FIG. 2 is a cross-sectional view of a housing taken along line II-II of FIG. 1.

#FIG. 3 is a diagram used to describe polarization characteristics of a light source unit and a light detector.

#Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference signs, and redundant description will be omitted.

#A spectrometer 1A (light measuring device) according to a first embodiment will be described with reference to FIGS. 1 to 9. As illustrated in FIGS. 1 and 2, the spectrometer 1A includes a light source unit 2, a light detector 3, a mirror unit 4, an incident adjustment mirror 6 (first guide mirror), a light guide mirror 7 (second guide mirror), and a support unit 8. The mirror unit 4 includes a plane mirror 41 (first plane mirror) having a mirror surface 41a (first mirror surface) and a plane mirror 42 (second plane mirror) having a mirror surface 42a (second mirror surface) opposite to the mirror surface 41a. Between the mirror surface 41a and the mirror surface 42a, a gas (measurement target) to be measured is introduced.

#As an example, the light source unit 2 and the light detector 3 are accommodated in the same housing 10. The housing 10 has a substantially rectangular parallelepiped outer shape and is disposed on a side of the mirror unit 4. More specifically, the housing 10 is disposed on a side of the plane mirror 42 on a side opposite to a side where the plane mirror 41 is located with respect to the plane mirror 42. In other words, the housing 10 is disposed at a position facing the back surface 42f on a side opposite to the mirror surface 42a of the plane mirror 42.