Optical device, spectroscopic device, and spectroscopic method

1 . An optical device comprising:

an analysis optical system; and

a length measurement optical system, wherein

the analysis optical system includes

a moving mirror configured to reflect analysis light emitted from a first light source to add a first modulation signal to the analysis light,

a gas cell with a gas that absorbs light of a predetermined wavelength sealed therein and configured to add a light absorption signal to the analysis light, and

a first light receiving element configured to receive the analysis light including a sample-derived signal generated by a sample, the first modulation signal, and the light absorption signal, and output a first light receiving signal, and

the length measurement optical system includes a second light source configured to emit laser light and obtains a displacement signal corresponding to a position of the moving mirror using the laser light.

2 . The optical device according to claim 1 , wherein

the analysis optical system includes the first light source.

3 . The optical device according to claim 1 , wherein

the analysis optical system includes an incidence switching unit configured to switch between a first state in which the analysis light is incident on the gas cell and is not incident on the sample and a second state in which the analysis light is incident on the sample and is not incident on the gas cell.

4 . The optical device according to claim 3 , wherein

the incidence switching unit is configured to switch between the first state and the second state by inserting and removing the gas cell.

5 . The optical device according to claim 3 , wherein

the incidence switching unit includes a light shield configured to switch between the first state and the second state by shielding the analysis light.

6 . The optical device according to claim 1 , wherein

the analysis optical system includes a wavelength conversion element configured to convert a wavelength of the analysis light emitted therefrom with respect to the analysis light incident thereon.

7 . The optical device according to claim 1 , wherein

the length measurement unit includes an optical modulator configured to add a second modulation signal to the laser light.

8 . The optical device according to claim 1 , wherein

the second light source is a semiconductor laser element.

9 . A spectroscopic device comprising:

the optical device according to claim 1 ;

a moving mirror position calculation unit configured to generate a moving mirror position signal based on the displacement signal;

a light intensity calculation unit configured to generate, based on the first light receiving signal and the moving mirror position signal, a waveform representing an intensity of the first light receiving signal at the position of the moving mirror;

a Fourier transform unit configured to perform Fourier transform on the waveform to generate a spectral pattern including a peak that is based on the light absorption signal; and

a moving mirror position correction unit configured to calculate, based on a position of the peak, a correction value for correcting the moving mirror position signal.

10 . A spectroscopic method of performing spectroscopy on a sample comprising:

measuring a position of the moving mirror based on the displacement signal obtained by the optical device according to claim 1 ;

disposing the gas cell and the sample on an optical path of the analysis light, causing the analysis light to be incident on the gas cell and the sample while changing the position of the moving mirror, causing the first light receiver to receive the analysis light emitted from the gas cell and the sample, and outputting the first light receiving signal;

generating, based on the first light receiving signal and a measurement value of the position of the moving mirror, a waveform indicating an intensity of the first light receiving signal at the position of the moving mirror;

performing Fourier transform on the waveform to generate a spectral pattern including a peak, that is based on the light absorption signal, and information derived from the sample;

calculating, based on a difference between a wavelength of the peak and a fundamental wavelength of the gas cell, a correction value for correcting the measurement value of the position of the moving mirror; and

correcting the spectral pattern based on the correction value.

11 . A spectroscopic method of performing spectroscopy on a sample comprising:

disposing the gas cell in the optical device according to claim 1 on an optical path of the analysis light;

measuring a position of the moving mirror based on the displacement signal obtained by the optical device;

causing the analysis light to be incident on the gas cell while changing the position of the moving mirror, causing the first light receiving element to receive the analysis light emitted from the gas cell, and outputting the first light receiving signal derived from the gas cell;

generating, based on the first light receiving signal derived from the gas cell and a measurement value of the position of the moving mirror, a waveform indicating an intensity of the first light receiving signal derived from the gas cell at the position of the moving mirror;

performing Fourier transform on the waveform derived from the gas cell to generate a spectral pattern including a peak that is based on the light absorption signal;

calculating, based on a difference between a wavelength of the peak and a fundamental wavelength of the gas cell, a correction value for correcting the measurement value of the position of the moving mirror;

disposing the sample on the optical path of the analysis light;

measuring the position of the moving mirror using the displacement signal obtained by the optical device;

causing the analysis light to be incident on the sample while changing the position of the moving mirror, causing the first light receiving element to receive the analysis light emitted from the sample, and outputting the first light receiving signal derived from the sample;

generating, based on the first light receiving signal derived from the sample, the measurement value of the position of the moving mirror, and the correction value, a waveform indicating an intensity of the first light receiving signal derived from the sample at the position of the moving mirror; and

performing Fourier transform on the waveform derived from the sample to generate a spectral pattern including information derived from the sample.