Autostereoscopic image display apparatus

An autostereoscopic image display apparatus comprising:

• a plane display device comprising pixels arranged in a matrix form;
• and
• an optical plate provided in front of the plane display device to control light rays illuminated from the pixels,
• the optical plate including:
• first and second substrates, each being transparent to light;
• liquid crystal sandwiched between the first substrate and the second substrate;
• first electrodes arranged periodically on a first plane of the first substrate opposed to the second substrate and supplied with a first voltage;
• second electrodes disposed on the first plane of the first substrate and between the first electrodes adjacent to each other and supplied with a second voltage which is lower than the first voltage;
• a third electrode provided on a second plane of the second substrate opposed to the first substrate and supplied with a third voltage which is equal to or less than the second voltage;
• and
• at least one spacer provided between the first substrate and the second substrate to hold a space between the first substrate and the second substrate,
• wherein denoting a refractive index of the liquid crystal in a director direction by Ne, denoting a refractive index of the liquid crystal in a direction perpendicular to the director direction by No, and denoting a refractive index of the spacer by ns,
• the spacer is disposed on the first electrode if a condition
• Ne×0.78+No×0.22≧ns≧No
• is satisfied, and
• the spacer is disposed on the second electrode if a condition
• Ne≧ns>Ne×0.78+No×0.22
• is satisfied.