The researchers designed and optimized an optical system for a small infrared spectrometer. They used a special type of grating scanning system to create the spectrometer. By using advanced software, they analyzed the system's performance and built an optimal design that can detect infrared light from 3μm to 5μm. The spectrometer has a high resolution and is very compact, making it useful for various applications. This work provides important information for developing small infrared spectrometers.