note that these two kinds of turning on timings may be switched in response to a mode switch signal from a mode switch portion not shown provided in the projection type display device that allows the viewer to switch between the color reproducibility oriented mode and the brightness oriented mode alternatively they may automatically be switched depending on the content and brightness of images to be displayed referring to fig4 a the color reproducibility oriented turning on timing will be described as shown in fig4 a a color image is displayed on the basis of a field one unit period consisting of sub fields sub unit periods displaying images corresponding to r g and b in the field for example the sub fields corresponding to r g and b are arranged in this order in the sub fields video signals sr sg and sb for r g and b are input to the liquid crystal light valve then after a writing scanning period t1 during which the video signals are sequentially written to the liquid crystal light valve from the top end to the lower end and a response waiting period t2 necessary for the liquid crystal in the liquid crystal light valve to respond to the video signals current corresponding to the video signals is supplied to the leds and color lights are irradiated to the liquid crystal light valve for a prescribed period after the irradiation of the color lights the next video signals are input to the liquid crystal light valve and the next sub field starts now referring to fig4 b the brightness oriented turning on timing will be described as shown in fig4 b the structures of the field and the sub fields for displaying a color image are the same.