Optical element and image display apparatus

An optical element comprising:

• a light guide element including a light guide plate, an incidence diffraction element, and an emission diffraction element,
• the incidence diffraction element being disposed on a main surface of the light guide plate and
• the emission diffraction element being disposed on the main surface of the light guide plate;
• and
• a positive lens that is disposed at a position overlapping the emission diffraction element in a view from a direction perpendicular to the main surface of the light guide plate,
• wherein the incidence diffraction element diffracts incident light such that the diffracted light is incident into the light guide plate,
• the emission diffraction element emits light propagating in the light guide plate from the light guide plate, and
• the positive lens collects the light that is emitted from the light guide plate by the emission diffraction element,
• the positive lens is a polarization diffraction element,
• the polarization diffraction element is a liquid crystal diffraction element that includes a liquid crystal layer including a liquid crystal compound,
• the liquid crystal layer has a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound changes while continuously rotating in at least one in-plane direction,
• the liquid crystal diffraction element includes two or more liquid crystal layers, and
• in a cross section of each of the two or more liquid crystal layers observed with a scanning electron microscope, bright portions and dark portions derived from a liquid crystal phase are tilted with respect to a main surface of the liquid crystal layer, and
• in a case where an interval between bright portions or between dark portions in a normal direction with respect to a tilted surface is set as ½ pitch, pitches of the liquid crystal layers are different from each other.

An optical element comprising:

• a light guide element including a light guide plate, an incidence diffraction element, and an emission diffraction element,
• the incidence diffraction element being disposed on a main surface of the light guide plate and
• the emission diffraction element being disposed on the main surface of the light guide plate;
• and
• a positive lens that is disposed at a position overlapping the emission diffraction element in a view from a direction perpendicular to the main surface of the light guide plate,
• wherein the incidence diffraction element diffracts incident light such that the diffracted light is incident into the light guide plate,
• the emission diffraction element emits light propagating in the light guide plate from the light guide plate, and
• the positive lens collects the light that is emitted from the light guide plate by the emission diffraction element,
• each of the incidence diffraction element and the emission diffraction element is a polarization diffraction element,
• the polarization diffraction element is a liquid crystal diffraction element that includes a liquid crystal layer including a liquid crystal compound,
• the liquid crystal layer has a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound changes while continuously rotating in at least one in-plane direction,
• the liquid crystal diffraction element includes two or more liquid crystal layers, and
• in a cross section of each of the two or more liquid crystal layers observed with a scanning electron microscope, bright portions and dark portions derived from a liquid crystal phase are tilted with respect to a main surface of the liquid crystal layer, and
• in a case where an interval between bright portions or between dark portions in a normal direction with respect to a tilted surface is set as ½ pitch, pitches of the liquid crystal layers are different from each other.