A high-speed spectral infrared imaging system has been developed for facilitating investigation of thermal processes, including those in combustion devices. The new system has several unique performance characteristics: variable and high speed frame rate; variable and short exposure period; independent control of imaging parameters; digital imaging in high dynamic resolution; spectral imaging, externally triggered individual images, and large number of frames per each data acquisition. Its design and performance verification was made by obtaining instantaneous thermal images that permit visualization of reaction fronts and subsequent mixing of combustion products of a Bunsen burner, a rectangular Poiseuille-flow burner, and a spark-ignition engine. Some results from this work are compared with those obtained using conventional methods reported in other literature. It is demonstrated that findings, otherwise difficult to obtain, are made possible by this newly developed tool.