Holographic Optical Elements（HOE）
Mar. 13, 2020
Holographic optical elements (HOE) is a type of diffractive optical element manufactured according to the principle of holography. Holographic optical elements are mainly holographic lenses, holographic gratings, holographic filters, holographic scanners, etc.
Or rather, holographic optical elements use holographic technology to record specific interference fringes on a photosensitive film. Their working principle is based on physical optics. Ordinary optical elements are made of transparent optical glass, crystals, or organic glass. Their working principle is based on geometric optics. Both of these components play the role of imaging, image transfer, beam splitting, and collimation.
| Holographic Optical Elements | Ordinary Optical Elements |
Material | transparent thin film or plastic | optical glass, crystals and PMMA |
Image-forming Principle | interference, diffraction (Physical Optics) | refraction, reflection （Geometrical Optics） |
Function | Imaging, Transferring, Light Splitting, Collimation etc. | |
Advantage:
1. The holographic optical element is a thin film system, so it is lightweight.
Conducive to the application of aviation technology and military equipment
2. Since multiple holograms can be recorded on the same negative film, spatially overlapping holographic optical elements can be obtained.
3. Various functions can be achieved with a holographic optical element according to high diffraction efficiency and narrow-band frequency characteristics.
Holographic optical elements are better in the case of monochromatic light or narrow spectral band.
The function of the holographic optical element is based on physical optics, and achieves the functions of light splitting, imaging, image transferring and collimation through the principles of interference and diffraction. The requirements for special functions can be fulfilled through the design of the optical paths. For example, an off-axis holographic lens can be used as a spectrograph element, which can replace lenses, beamsplitters such as prisms or gratings. Meanwhile HOE integrate three functions of focusing, beam splitting, and image transfer. In this way, the structure of instruments are greatly simplified and the optical systems are optimizied. The cost of the instruments is lower than before.
It can be seen that the biggest advantage of a holographic optical element is that it can realize the functions of multiple traditional optical elements on a single holographic optical element. Therefore, it can be widely used in various fields such as optical equipment, communication and display. For example, hologram memory, holographic projection screen, holographic printer, 3D head-mounted display (HMD) and so on.
Disadvantages:
1. Imaging characteristics of HOE change with wavelength, so there is a lot of chromatic aberration
2. There can’t be a large field of view and exit pupil at the same time because HOE is a a diffractive optical element.
3. HOE can’t provide the sharing of a single system, such as telescope holograms can’t provide angular magnification
Owing to these reasons, holographic optical elements can’t completely replace traditional optical elements. They usually be used in optical systems with other original optical elements such as optical lenses, optical prisms, optical windows and optical filters. CLZ Precision Optics Co., Ltd. can provide you with a variety of traditional optical components used in conjunction with holographic optical components. If you have any need, please contact: talia@clzoptics.com.
