Patent ID: 7997737

Claim:
A projection display device, comprising: a laser light source; a spatial light modulation element for modulating laser light to be emitted from the laser light source; a projection lens for projecting the laser light modulated by the spatial light modulation element onto a screen; and a plurality of light diffusing elements, arranged on an optical axis between the laser light source and the spatial light modulation element, for changing a degree of diffusion of the laser light temporally and electrically, wherein the plurality of the light diffusing elements cyclically change the degree of diffusion respectively, the plurality of the light diffusing elements including two light diffusing elements, a first light diffusing element and a second light diffusing element, each of the plurality of the light diffusing elements chnages from a scattering state to a transparent state once per cycle and each has a transparent film dispersedly containing a liquid crystal material and two transparent electrodes for sandwiching the transparent film therebetween, one of the transparent electrodes of the first light diffusing element is grounded and another of the transparent electrodes thereof is connected to one of the transparent electrodes of the second light diffusing element and to an alternate current power source, the one of the transparent electrodes of the second light diffusing element is connected to the other of the transparent electrodes of the first light diffusing element and to the alternate current power source, and another of the transparent electrodes thereof is connected to a direct current power source for outputting a voltage of a value substantially equal to a maximum value of an output voltage of the alternate current power source, and a phase of the cyclic change in the degree of diffusion is shifted with respect to each of the light diffusing elements, and a phase difference between the two light diffusing elements is a one-half cycle.