Patent ID: 9628765
Date: 2017-04-18
CPC Classifications: G02B,H04N

Claim:
1. A spatial image projection apparatus, comprising: a receiver configured to receive an image signal; a display unit configured to display an image acquired by processing the image signal; a controller to control the display unit; a projection unit configured to project a spatial image to a prescribed space by transmitting or reflecting light corresponding to the image displayed on the display unit; and an optical-path length-converter located between the display unit and the projection unit so as to change an optical-path length of the image, wherein the optical-path length-converter includes: a polarizer configured to transmit only specific polarized light, among the light introduced from the display unit, toward the projection unit, and to reflect the remaining light other than the specific polarized light; and a mirror configured to transmit light, introduced from the display unit, to the polarizer, and to convert the light reflected from the polarizer into specific polarized light so as to again reflect the light to the polarizer, wherein the optical-path length-converter changes an optical-path length from the display unit to the projection unit by linearly moving the mirror and the polarizer toward the display unit or the projection unit in response to a control signal from the controller so as to reduce a distance between the display unit and the projection unit and such that a size of the spatial image is maintained.