Correction of spectral deformation by second-order diffraction overlap in a mid-infrared range grating spectrometer using a PbSe array detector

• Diffraction order overlap in a grating spectrometer causes unwanted confusion.
• Post processing method without a switching filter procedure was devised.
• The proposed method could be usefully for the time-resolved measurement of flames.
• A total uncertainty of 5.59% exists in the OES system using the suggested method.

Conventional diffraction gratings suffer from order overlap problems, especially for a mid-infrared optical emission spectrometer (mid-IR OES) using a detector array. Because of diffraction order overlap, ambiguous spectroscopic data are inevitably acquired. This shortcoming motivated us to devise an order-sorting method. We predicted a second-order diffraction overlap and corrected the deformation of signal measured with a mid-IR OES using an array detector. It is found that the first-order signal separated from the overlapped spectrum fit well with the intrinsic signal of incident light. We determined the system response function of a mid-IR OES and confirmed the validity of the compensation method by comparing the measured spectrum with Planck’s curve of blackbody radiation at two different temperatures. In addition, for accuracy verification, the uncertainty factors that could affect the compensation procedures were carefully considered.