Backlight device, holographic display including the same, and method of manufacturing holographic optical element having a multilayered structure

Abstract

A backlight device having a light guide, a first holographic optical element and a second holographic element are provided. The light guide plate guides light emitted by a light source towards the first holographic optical element. The first holographic optical element, which has a multi-layered structure, is provided on a first side of the light guide plate and reflects the light according to the wavelength ranges based on the characteristics of the multi-layered structure. The second holographic optical element, which concentrates light reflected by the first holographic optical element onto at least two points is provided on a second side of the light guide plate perpendicular to the first side.

What is claimed is: 
     
         1 . A method of manufacturing a holographic optical element, the method comprising:
 attaching a first layer to a substrate;   dividing the first layer into a plurality of areas and sequentially recording holograms by using light of a first color;   attaching a second layer to the first layer; and   recording holograms on the second layer by using light of a second color and light of a third color.   
     
     
         2 . The method of  claim 1 , further comprising performing pre-exposure on the first layer by using a light source that has a low coherence.