Backlight module for imaging projection system

The invention discloses a backlight module for an imaging projection system. The backlight module comprises a liquid crystal display and a backlight lamp panel, and further comprises a directed diffusion diaphragm arranged between the liquid crystal display and the backlight lamp panel. A traditional diffusion type light source is replaced by a directed diffusion type light source, the LCD black field light leakage phenomenon caused by large-angle incidence of backlight rays is reduced as much as possible, and therefore the contrast ratio of the liquid crystal display is increased; the directed diffusion diaphragm can control LCD screen-leaving luminance view angle distribution including luminance asymmetrical distribution so that the requirements of an off-axis eccentric system for luminance view angles can be met. Meanwhile, the directed diffusion diaphragm has the directed diffusion focusing characteristic and has the good light uniformizing characteristic, the backlight module can replace a conventional liquid crystal backlight module composed of an ordinary diffusion diaphragm and a prism diaphragm, the structure of the backlight module is simplified, and the solar energy utilization efficiency is improved.