Patent ID: 8194192

Claim:
A projection display comprising: video information inputting means that inputs video information; luminance information detecting means that detects characteristics of luminance information of the input video information and that outputs luminance information digitalized on the basis of the input video information; a light source; light source lighting means that outputs a power waveform to cause the light source to light in accordance with the luminance information obtained by the luminance information detecting means; and a light modulating device that receives light radiated from the light source and modulates the light in accordance with the video information and the luminance information to perform video display, wherein in order to adjust the amount of light with which the light can be expressed as video on a screen, the light source lighting means separates a unit of time configuring the video into an effective light time t 1 in which the light modulating device can express the light as video on a screen and an ineffective light time t 2 in which the light modulating device cannot express the light as video on a screen, and assuming that P 1 represents the power supplied to the light source during the effective light time t 1 , P 2 represents the power supplied to the light source during the ineffective light time t 2 , and average power P represents the power supplied to the light source averaged in the unit of time configuring the video, and assuming that T 1 represents the percentage of the effective light time t 1 within one frame of the video information and that T 2 represents the percentage of the ineffective light time t 2 within one frame, the light source lighting means dynamically changes T 1 , P 1 , T 2 , and P 2 every one frame or every plural frames in accordance with the luminance information detected by the luminance information detecting means such that the average power P becomes T 1 ·P 1 +T 2 ·P 2 =P ·( T 1 +T 2).