OPTICAL UNIT, PROJECTION IMAGE DISPLAY DEVICE, AND DIFFUSION OPTICAL ELEMENT

摘要

Disclosed is a projection image display device which is provided with: a light source (110) which emits light having coherency; a light modulation element (500), which modules the light emitted from the light source; and a projection unit (150) which projects, to a projection surface, the light emitted from the light modulation element. The projection image display device is also provided with a speckle noise reducing element (600) provided between the light source and the light modulation element, and a control unit which controls first mode and second mode. The control unit controls the speckle noise reducing element such that speckles are reduced in the first mode compared with those in the second mode.