We can record digitally-designed information of three-dimensional (3D) objects or optical elements on a holographic photosensitive material by using wavefront printing technology. But the hologram data generated from the digitally-designed information are very huge and there are often the occurrences of the unnecessary bidirectional communications. To solve this problem, we studied on a special-purpose computer for wavefront printing technology. This technique consists of generating the light-ray information from digitally-designed information of 3D objects, converting the light-ray information to the wavefront information and generating the hologram data locally from the wavefront information in interaction. In this paper, we designed the emulator of the special-purpose computer for wavefront printing technology and obtained the amount of information (the number of bits) required for the circuit by comparing the 3D images reconstructed from the holograms generated by the emulator. As a result, the amount of information of the wavefront information converted from the light-ray information most affected the quality of the 3D images reconstructed from the holograms generated by the emulator and we can design the emulator that can reduce the noise component from those 3D images. In the future, we will design the special-purpose computer for wavefront printing technology by using hardware description language and implement that special-purpose computer on a programmable logic device such as a field programmable gate array.
A see-through light-field 3D display that works in head-up configuration is being presented. The display system consists of only a commercial projector and a holographic screen and works on the principle of Integral Imaging. The holographic screen is a volume hologram that is digitally fabricated, which functions as a micro concave- mirror array. The screen also has other optical functions embedded that helps to eliminate the bulk of optical components needed otherwise. This significantly simplifies the system, there by taking it closer to the consumer market. A color 3D scene of size 20cm x 10cm x 5cm (depth) has been successfully reproduced and can be seen through naked eye for a viewing angle of 10-degrees.
In this paper, we introduce hologram printing technology. This technology includes the following technologies, computer-generated hologram, hologram printer, duplication, and application-depended technologies. When this technology is applied to static hologram, the media can present static 3D objects more clearly than traditional 3D technologies such as lenticular lens and integral photography(IP) because it is based on holography. When this technology is applied to holographic optical elements(HOE), the HOE will be useful for many purposes especially for large optical elements. For example, when it is used as screen, the visual system which consists of the screen and projector can present dynamic 2D or 3D objects. Since this technology digitally designs hologram/HOE and manufactures them by wavefront printer, it is good at generating small lot of production. As a result, it is effective for the research stage of both 2D and 3D display. In addition, it is also effective for commercial stage due to simple duplication method.
A hologram of a scene can be digitally created by using a large set of images of that scene. Since capturing such a large amount is infeasible to accomplish, one may use view synthesis approaches to reduce the number of cameras and generate the missing views. We propose a view interpolation algorithm that creates views inside the scene, based on a sparse set of camera images. This allows the objects to pop out of the holographic display. We show that our approach outperforms existing view synthesis approaches and show the applicability on holographic stereograms.
Several wavefront printers have been recently proposed. Since the printers can record an arbitrary computer-generated wavefront, they are expected to be useful for fabricating complex mirror arrays used in front projection 3-D screens without using real existing optics. We prototyped two transparent reflective screens using our hologram printer in experiments. These screens could compensate for a spherically distorted reference wave caused by a short projection distance to obtain an ideal reference wave. Owing to the use of the wavefront-printed screen, the 3-D display was simply composed of a normal 2-D projector and a screen without using extra optics. In our binocular system, reflected light rays converged to the left and right eyes of the observer and the crosstalk was less than 8%. In the light field system, the reflected light rays formed a spatially sampled light field and focused a virtual object in a depth range of ±30 mm with a ±13.5-deg viewing angle. By developing wavefront printing technology, a complex optics array may easily be printed by nonprofessionals for optics manufacturing.
This paper presents a fast calculation method for spherical computer-generated hologram by using a spherical harmonic transform. A three-dimensional (3D) object defined in the 3D Cartesian coordinate system is numerically Fourier transformed with fast Fourier transforms (FFTs). Fourier components on the spherical surface of the radius 1/λ are extracted. The wavefronts on the spherical surface can be calculated from the single spherical Fourier components. This paper reveals the analytical diffraction integral between the spherical Fourier components and the wavefront on the spherical surface. This diffraction integral is expressed in the form of convolution integral on the sphere and can be calculated very fast based on the spherical harmonic transform. By the numerical simulation, the validity and the effectiveness of our proposal has been verified.
A Fizeou interferometer with instantaneous phase-shifting ability using a Wollaston prism is designed. to measure dynamic phase change of objects, a high-speed video camera of 10-5s of shutter speed is used with a pixelated phase-mask of 1024 × 1024 elements. The light source used is a laser of wavelength 532 nm which is split into orthogonal polarization states by passing through a Wollaston prism. By adjusting the tilt of the reference surface it is possible to make the reference and object beam with orthogonal polarizations states to coincide and interfere. Then the pixelated phase-mask camera calculate the phase changes and hence the optical path length difference. Vibration of speakers and turbulence of air flow were successfully measured in 7,000 frames/sec.