1. Introduction

The term of "holography" was proposed by Denies Gabor in 1948, and the invention has received a lot of interests since it was introduced first. Holography is the technique that deals with the interference and diffraction of the visible light in order to record the three-dimensional (3D) information of the objects into the amplitude or phase holograms on the holographic material and reconstruct the 3D visualization of the object. The holographic optical elements (HOEs) are the very interesting applications of the holography where many institutes work and develop for them. The first HOE concepts of holographic application, a holographic mirror, have been described by Denisyuk in 1962 [1]. Then, the point-source hologram which acts as lens was demonstrated by Schwar et al. in 1967 [2]. And, Latta et al. analyzed the compensate aberrations for HOE, the quantitative consideration [3]. Hence, a lot of institutes and companies work for the practical application of the HOE, and it is still a hot research topic in holography-based fields.

A HOE is the technique using a principle of holography, is a kind of diffraction optical elements (DOE), to replace heavy and complicated optical element has been highlighted as a useful

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

technique. HOEs can be a mirror, lens, or directional diffuser, because it can implement various functions on a single material according to high diffraction efficiency and narrow-band frequency characteristics. Therefore, the HOEs are widely applied in many fields such as a hologram memory, holographic projection screen, holographic printer, 3D head-mounted display (HMD), and so on.

In this chapter, first, the principle of HOE, the basic concept of recording and reconstruction for HOE, and the characteristic of the HOE are described in detail. Then, several examples of applications of HOE such as waveguide and wedge-shaped waveguide-based HMD, HOE lens array, and solar concentration are reviewed.
