Holographic displays with light modulation in amplitude and phase

A display device for hologram, the display device comprising:

• a display screen;
• a driving circuit including a power source to generate a voltage;
• a spatial light modulator modulating an optical image in amplitude and phase before a view of the optical image is seen on the display device, wherein the spatial light modulator includes:
• an alignment layer;
• a layer of electrodes;
• a layer of liquid crystals sandwiched between the alignment and the electrodes, where the voltage from the driving circuit is applied across the liquid crystals, the voltage includes a plurality of step volts from a voltage level VL to VH to cause the liquid crystals to twist so that the phase of the optical image changes from 0 degree to 360 degrees when the voltage goes from VL to VH, where VL is at least above Vth, a threshold voltage, VH is a predefined highest voltage level that causes the phase to reach 360 degrees, and
• wherein the voltage is further impulsively increased to VP for a moment to minimize or eliminate a free relaxation time that would otherwise happen when the voltage level VH drops;
• and increase the voltage level to twist the liquid crystals gradually from substantially blocking the optical image to fully passing the optical image therethrough and again from substantially blocking the optical image to fully passing the optical image therethrough, where VP is a voltage level greater than the voltage level VH.