We developed a holographic head-mounted display with a see-through structure that enables the user to view augmented reality scenes binocularly. It has right and left optical systems for each eye that have horizontal sliding structures to adapt the interdistance to each observer’s different interpupillary distances. Reconstructed images are colorized using the field sequential color method and are enlarged using a Fourier transform optical system. This paper describes a calibration method to correct installation errors arising from the optical elements. The results of objective and subjective evaluations show that the reconstructed images locate at the correct depths and provide correct accommodation and vergence as well.
In CGH, peculiar rendering techniques are necessary to express realistic 3D images because CGHs have parallax.
We have proposed the calculation method with the ray tracing method that expresses the hidden surface removal,
shading and so on. However, resolutions of current output devices are not high enough to display CGH, so the
size of reconstructed images is restricted and viewing zone and visual field are very narrow. To enlarge the size
of reconstructed images, the Fourier transform optical system is used. Then we introduce the technique to apply
calculation method of CGH with ray tracing method to the Fourier transform optical system in this paper. The
Fourier transform optical system reverses the depth of images and reconstructs pseudo stereoscopic 3D images
in front of a hologram. We solved this problem by reconstructing images at the back of hologram plane and
observing conjugate images. Moreover, we conducted elimination of unnecessary light including 0-th order light.
We conducted optical reconstructions that show proposed method is able to make realistic CGHs implementing
the hidden surface removal in the Fourier transform optical system.
Computer generated hologram (CGH) can reconstruct 3-D objects as perfectly well as can optical holography.
However, the reality of the reconstructed objects is lower than that of optical holography.
This problem is caused by a lack of rendering techniques for CGH.
To improve the reality of objects reconstructed by CGH, we have studied rendering techniques in computer graphics such as reflectance distributions for CGH.
Reflectance distributions represent a material of an object surface, and objects with various reflectance distributions are reconstructed by using the previous work.
In this paper, we improved on the previous work by using polygon models and shading techniques for CGH.
The shading technique is also established in computer graphics, and it can render objects having a smooth luminance without using many polygons.
A polygon model made up of many polygons is rendered the same as a polygon model made up of few polygons by using shading technique.
However, the calculation time of CGH increases with the number of polygon, so it is necessary for CGH to reconstruct objects of high reality from polygon models made up of few polygons.
Taking into account the shading technique, polygon models with few planer patches are reconstructed with smooth luminance.
We carried out computational and optical reconstructions as experiments.
We report the results of these experiments and show the effectiveness of our proposed method.
Computer-generated hologram (CGH) is a one of 3-D display technologies, and it reconstructs natural and
virtual objects. However, improvement of the reality of reconstructed images is necessary for reconstructing
complex and clear scenes like computer graphics. We have studied about the rendering techniques for CGH,
and proposed the method considering background reflections and reflectance distributions. The background
reflections and reflectance distributions are the characteristics of reflection. Metallic objects and reflected
scenes were reconstructed by considering these. In this paper, we improved the previous works for express
complex scenes. The proposed method considered the background reflections and reflectance distributions on
the curved surface such as convex and concave mirrors. By using the phase transformation, the background
reflections and reflectance distributions on it with some roughness are generated. We performed that the
background reflections and reflectance distributions on the convex and concave mirrors with roughness are
actually obtained through computational and optical reconstructions.
We propose a new method of calculating the reflectance distribution on object surfaces for computer-generated holograms to improve the reality of reconstructed images, which takes into consideration reflection on the surfaces of metallic objects.
It is based on the Blinn or the Torrance-Sparrow reflection model that has been established in computer graphics.
Moreover, we also take into account the Fresnel equation for the method, which provides the degree of reflection on metallic surfaces.
We adapted this model to the process of calculating computer-generated holograms, so that various reflectance distributions could be derived.
In our experiments, we carried out comparison theoretical and simulated intensity distributions, optical reconstructed experiments, and computer simulations.
As a result, we obtained the reflectance distributions of reconstructed images by using the new approach.