a power - saving method with integrated photodiode light source . this device has a circuit board with a plurality of red , green and blue photodiodes as the device &# 39 ; s light source . additionally , a light control circuit is used to control light beam from the light source illuminating a reflector and then reflecting to a reflective display panel in order to reflect the light beam and generate an image . thus , a projection module can project the image on a viewing plate . as cited , the inventive device includes : a light control circuit , a light source module , a polarizing beam splitter , a reflective display panel and a projection module .