| 摘要 |
PURPOSE:To reduce the size of a device and to speed up its response by making image luminous flux incident on a grating structure whose modulation degree is variable and projecting shift image luminous flux as diffracted luminous flux with desired intensity in the direction of an angle of diffraction corresponding to a diffraction degree. CONSTITUTION:A substrate 2 is transparent and a relief type grating is formed on its top surface. A liquid crystal layer 8 is interposed between transparent electrodes 4 and 6. When luminous flux 12 is made incident from above, diffraction is caused because of the grating structure and 0-order diffracted light (i.e. transmitted light) 14, primary diffracted light 16, and secondary diffracted light 18 are projected downward. A voltage applied to the liquid crystal layer 8 by a power source 10 is varied to vary the refractive index difference of the grating structure and very the degree of modulation, thereby varying the intensity ratio of said respective diffracted light beams which differ in degree. |
