Gas measurement device and gas measurement method

A gas measurement apparatus for obtaining concentration of a target component in a gas to be measured by cavity ring-down absorption spectroscopy, the apparatus comprising

• a laser-light source configured to have a variable wavelength;
• an optical resonator which includes a pair of highly-reflective mirrors and a measurement cell in which the gas to be measured is to be contained, and resonates laser light which is emitted from the laser-light source and is introduced into the measurement cell;
• an optical detection unit configured to detect laser light output from the optical resonator;
• a measurement controller configured to control the apparatus so that the laser-light source causes laser light to be incident to the optical resonator, and a wavelength of the laser light is scanned within a predetermined wavelength range, the range including an absorption peak of the target component, thereby performing the cavity ring-down absorption spectroscopy measurement through an output of the optical detection unit;
• a spectrum generator configured to generate an absorption spectrum based on data obtained at each wavelength within the predetermined wavelength range under the control of the measurement controller;
• a processing unit configured to approximate a waveform shape of the absorption peak of the target component in the absorption spectrum with a polynomial and configured to acquire a coefficient of a term of a predetermined degree in the polynomial;
• and
• a result obtaining unit configured to obtain absorption intensity from the coefficient obtained by the processing unit based on predetermined reference information indicating a correspondence relation between a coefficient of the term of the predetermined degree and the absorption intensity.