The Fourier Transform Infrared (FTIR) spectrometer is widely utilized for the detection and identification of gas in laboratories and open environments. The measurement sensitivity and range of the spectrometry are limited due to the strength of the absorption or emission signals. This study proposes the use of the sinusoidal phase modulation technique to improve the signal to noise ratio (SNR) of the detected signal of an FTIR spectrometer. In this technique, a sinusoidal signal is applied to a voice coil to make moving of a mirror. Hence, the intensity of the interference signal is a series of harmonics. A synchronous detection (lock-in amplifier) is then utilized to detect and amplify only one suitable harmonic and removed all other harmonics and noise. Therefore, the SNR of the harmonic is improved significantly. In this paper, a weak infrared emission from a commercial heat-lamp is detected successfully using the proposed system.
FT-TR spectroscopy, frequency modulation, phase modulation, Michelson interferometer.
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TẠP CHÍ KHOA HỌC VÀ CÔNG NGHỆ Giấy phép số37/GP-BTTTT (15/01/2021) Giấy phép sửa đổi, bổ sung số140/GP-BTTTT (05/3/2021) Đơn vị cấp phép:Bộ Thông tin và Truyền thông Cơ quan chủ quản:Trường Đại học Bách Khoa Hà Nội Phó tổng biên tập phụ trách:GS. Đinh Văn Phong