Liquid crystal light modulation device

A liquid crystal liquid modulation device comprising:

• a first substrate and a second substrate;
• said first substrate having a light-incident side for receiving incident light and a facing side facing said second substrate, said second substrate having a facing side facing said facing side of said first substrate, and said facing sides of said first and second substrates being parallel with each other and spaced a predetermined distance from each other;
• an optical element having plural portions, and liquid crystals, said portions of said optical element and said liquid crystals being alternately arranged between said first and second substrates, the heights of said portions of said optical element and said liquid crystals in a direction normal to said facing sides being substantially the same, and said liquid crystals being separated from one another by the intervening portions of said optical element;
• and
• control means for changing the refractive index of said liquid crystals, said control means causing said liquid crystals selectively to have at least two refractive indexes, one of said refractive indexes being substantially the same as that of said optical element and the other of said refractive indexes being different from that of said optical element so as to form a diffraction grating by said alternatively arranged liquid crystals and portions of said optical element.