## 1 Introduction
[24] calculated the temperature and emissivity curves of a solid waste incinerator using spectral data and the two-color pyrometry method. The operation of this method is simple, but it can only obtain the temperature information of the flame, not the spatial information of the flame. With the development of optical technology, two-color pyrometry technology has evolved from spot temperature measurement [25; 26] to being combined with CMOS and CCD imaging technologies [27; 28] to achieve higher spatial resolution and higher precision temperature measurement. [PERSON] [29] developed an improved two-color pyrometry high-temperature measuring instrument for suspended tungsten powder, solving the problem that the absolute RGB value of each pixel cannot be calculated. A two-color ratio analysis was performed to calculate the temperature of each pixel, and the average G/R ratio of each pixel was calculated based on the surrounding \(3\times 3\) matrices. [PERSON] [30] used a high-speed CMOS camera to measure the formation of combustion soot from engines based on temperature measurement technology, and methodological studies on the influence of the dynamic range and wavelength used in the detector. [PERSON] [31] used two-color pyrometry thermometry to study the flame structure of pulverized coal combustion and the time series of flame temperature and particle temperature. The results showed that the increase in oxygen concentration raised the combustion temperature and flame diameter of volatiles and extended the special duration of volatile combustion. [PERSON] [32] obtained the two-dimensional temperature field of the Mg/CO\({}_{2}\) combustion flame by constructing a Mg/CO\({}_{2}\) combustion device and a two-color pyrometry temperature measurement system based on a color charge-coupled device (CCD). The experimental results verified the accuracy of temperature measurement of high-temperature objects based on the color CCD radiation imaging method. Although the existing two-color thermometry methods are able to solve the problem of flame spatial and spectral information, there is almost no elaboration on the selection of temperature measurement spectra, and the range of temperature measurement spectra. The range of temperature spectra, as well as the selection of wavelength intervals of the dual-band, affects the accuracy of temperature measurement to a certain extent. The primary objective of this study is to detect the flame temperature field using spectral analysis in conjunction with two-color thermometry. The combustion radiation spectrum was obtained through Laser-Induced Breakdown Spectroscopy (LIBS) technology, and the optimal spectral line for temperature measurement was selected based on the principles of two-color thermometry. This approach effectively eliminates the influence of the emissivity of the measurement target. The temperature measurement system was calibrated at temperatures ranging from 600 to 1000 \({}^{\circ}\)C using a commercial standard blackbody source. The detection of the nitrocellulose flame temperature was achieved by analyzing the images acquired from two wavebands. Compared to traditional colorimetric temperature measuring instruments, this method provides a more accurate two-dimensional temperature image of the flame, with a measurement error of within 3%.