The Lyman UV (LUV) band possesses several unique characteristics that make it useful to study the properties of the interstellar medium and the circum-galactic medium (CGM) surrounding nearby galaxies. MCP detectors are sensitive in the LUV band and can be used as imagers and photon counters in space missions. Instead of MCP, this paper describes a new CMOS imaging system that can be applied to astronomical observations in the LUV band. We adopted a special back-side illuminated CMOS as the image sensor. Using it, we developed a LUV imaging system based on FPGA technology. With the assistance of a synchrotron radiation platform, the properties of the CMOS imaging system were measured and calibrated within the wavelength range from 105 nm to 130 nm. By calibrating gain, photon current, electron number and photon number parameters, we derived the quantum efficiency curve for this wavelength range. Such a development provides a new method to detect and image Lyman UV radiations.