A head mounted display (HMD) includes a first transparent light source, a first micro-lens array panel and a first transparent LCD panel. The first transparent light source emits a plurality of pin-lights along a first light projection path. The first micro-lens array panel having a plurality of micro-lens, and the micro-lens respectively receive the pin-lights and adjust characteristics of projection surfaces of the pin-lights to generate a plurality of adjusted lights. The first transparent LCD panel receives the adjusted lights and generates a first display image according to the adjusted lights.