## 1 Introduction  
The control environment of the manufacturing process has recently been a very important factor in real industry. It can improve the quality of the product by adjusting various gases in the manufacturing process. Furthermore, polluted gases, such as CO, NOx, and SO\({}_{\text{X}}\) are produced during the burning process in engines, burners, and turbines. In order to reduce emissions of these harmful substances, the quality of combustions of these processes should be improved. The combustion quality can be managed by controlling the combustion factors, such as temperature and concentration. To attain clean gas emissions, measurements for the local temperature and concentration distributions in the combustion field should be attained in real-time. As measurement methods for this, SAW (surface acoustic wave) type sensor was proposed to detect CO\({}_{2}\)[1] and to measure gas temperature [2]. For other gas measurements, such as CO, NOx, CO\({}_{2}\)[3], and NH\({}_{4}\)[4], the electric type sensor was adopted. All of these approaches are not appropriate for the measurement of temperature and concentration fields, i.e., the distributions of temperature and gas concentration. On the other hand, there have been several approaches to using laser technology. It has been proven that the TDLAS (tunable diode laser absorption spectroscopy) is able to measure the temperature and concentration with fast response time [5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16]. [PERSON] et al. [7] showed that the TDLAS could measure transient changes of temperature and concentration in a combustion engine under various operation loads. [PERSON] et al. [10] presented a tunable ECDL (external-cavity diode laser) based on a rapidly vibrating diffraction grating. The laser scanned from 1374 to 1472 nm band of H\({}_{2}\)O for HCCI (homogeneous-charge compression ignition) engine measurements. [PERSON] et al. [11] detected by crank angle-resolved of gas temperature and water vapor concentration during the compression stroke of an IC (internal combustion) engine with a diode laser absorption sensor. Among the more advanced technologies, CT-TDLAS (computed tomography-tunable diode laser absorption spectroscopy) is the most important technique for measuring the distributions of temperature and concentration across the 2-dimensional planes [17; 18; 19; 20]. However, supplying gases or real flame is not uniform. In this study, suggest a 2-dimensional measurement of irregular flow or exhaust gases.  
In this study, CT-TDLAS has been adopted for the measurement of temperature distribution at a cross-section of Methane-Air premixed flame. The SMART (simultaneous multiplicative algebraic reconstruction technique) algorithm has been also adopted for CT (computed tomography) calculation for real flame measurement [20]. The absorption spectra of H\({}_{2}\)O vapor near the wavelength of 1388 nm were used for signal reconstructions. In the CT process, it is important to adopt the initial values for the temperatures at all grids. Therefore, CSLOs (corrective summation of line of sight) method has been adopted. The temperatures obtained by using the CT-TDLAS technique were compared with those obtained by thermocouples.