The wavefront of any object can be recorded and reproduced using computer-generated holography, regardless of whether the object is real or not. Due to a computer-generated holographic display provides all of the object’s depth cues, it naturally resolves the vergence-accommodation conflict. The development of color computer-generated holographic three-dimensional(3D) display technology has received a lot of attention as one of the key technologies of the computer-generated holographic 3D display.
The types and principles of chromatic aberration in the color computer-generated holographic 3D display are investigated in this paper. The technologies of color computer-generated holographic 3D display are then classified and outlined.
The time-division multiplexing technology makes it possible to use only one spatial light modulator (SLM) for color holographic display. Some researchers, for example, use the time-division multiplexing method to construct a full-color holographic 3D display system based on liquid crystal displays (LCD). In this system, a rotating wheel plate is used to cause red light, green light, and blue laser light to alternately irradiate the LCD. At the same time, the red, green, and blue holograms are correspondingly loaded on the LCD. The resolution of each color hologram is the same as that of the LCD. The recording distances of the red, green, and blue holograms are compensated to eliminate the axial chromatic aberration introduced by the 4f system. To achieve color holographic 3D reconstruction, the time-division multiplexing technology fully utilizes the refresh rate of the SLM and the persistence of vision effect of the human eye. The demanding requirements on the refresh rate of the SLM and the performance of the synchronization control module limit the realization of the dynamic display effect to some extent.
The space-division multiplexing technology based on multiple SLMs has lower requirements on the refresh rate of the SLMs, so there is no image flickering. Red, green, and blue holograms are loaded on multiple SLMs in this method, and the resolution of the hologram is equal to that of the SLM. The red, green, and blue images reproduced are spatially coincident by precisely adjusting the optical path. The image can then be reproduced in color. However, the system structure of this technology is typically complex, and the cost is high. The spatial alignment of the reconstructed red, green, and blue images is extremely difficult.
The space-division multiplexing technology based on a single SLM has the merits of the relatively simple optical path structure, the flicker-free reconstructed image, and being free from rainbow effect. The red, green, and blue lasers illuminate one-third of the area of a single SLM in this method. Each color hologram has a resolution that is one-third of the resolution of the SLM. However, the image resolution is reduced to one-third of the original, the spatial bandwidth product of the color reproduced image is reduced, and the perspective is also affected.
Some researchers have proposed the target image separation method based on a single SLM to avoid reducing the resolution of the color reproduction image. When the SLM is irradiated by red, green, and blue light at the same time, the target color reproduction image and the interference image are separated, and the target color reproduction image can be obtained by filtering. In addition to designing and improving the optical system structure, using the excellent properties of new materials is another way to realize color holographic display. Other technologies, such as the use of metasurfaces, fully exploit the advantages of the new materials and have promising future prospects.
Many methods have been proposed to realize color computer-generated holographic 3D display. This paper summarizes the color computer-generated holographic 3D display realization technology. Among these methods, the space-division multiplexing with multiple spatial light modulators and time-division multiplexing with a single spatial light modulator are frequently used. The quality of the color image is affected since the resolution is reduced when using the space-division multiplexing technology based on a single SLM. The technique that using a single SLM to realize the color holographic reconstruction based on the angle compensation method has certain advantages in resolution because it saves space and time resources. The various method proposals provide novel ideas for the perfect reconstruction of color holograms. However, based on the current state of holographic 3D display development, the high-quality holographic 3D display has higher spatial bandwidth product requirements. While improving the spatial bandwidth product, more research and exploration are needed to determine how to make the color computer-generated holographic 3D display system simple and compact without a complex synchronous control system.
