High-definition CGHs can reconstruct high-quality 3D images that are comparable to that in conventional optical holography. However, it was difficult to exhibit full-color images reconstructed by these high-definition CGHs, because three CGHs for RGB colors and a bulky image combiner were needed to produce full-color images. Recently, we reported a novel technique for full-color reconstruction using RGB color filters, which are similar to that used for liquid-crystal panels. This technique allows us to produce full-color high-definition CGHs composed of a single plate and place them on exhibition. By using the technique, we demonstrate full-color CGHs that reconstruct hybrid scenes comprised of real-existing physical objects and CG-modeled virtual objects in this paper. Here, the wave field of the physical object are obtained from dense multi-viewpoint images by employing the ray-sampling (RS) plane technique. In addition to the technique for full-color capturing and reconstruction of real object fields, the principle and simulation technique for full- color CGHs using RGB color filters are presented.
Several techniques are reviewed in high-definition computer holography. These techniques are based on numerical techniques in wave optics. For example, the polygon-based method based on propagation between tilted planes is used for calculating the field of polygonal surface sources of light. Numerical propagation of large-scaled field is also implemented by using the technique of off-axis propagation. The silhouette method for occlusion processing is based on the angular spectrum method for propagation between parallel planes. The relation between computer holography and computational optics are presented and several high-definition CGHs using these techniques are demonstrated for verifying the techniques.
A method called the switch-back technique allows us to drastically reduce computation time of occlusion-processing based on the polygon-by-polygon silhouette light-shielding. It is also reported that further reduction of computation time can be achieved by splitting an object to some sub-models along with depth direction. However, computational cost for numerical propagation between the sub-models increases with increasing the number of sub-models. As a result, there is an optimum number of sub-models. In this paper, we propose a technique to predict the optimum number of sub-models by estimating the total computational complexity of the switch-back technique with object splitting.
We propose a technique for optimization of design-wavelengths in trichromatic computer holography. Full color reconstruction of high-definition computer-generated holograms (CGH) is simply realized by combining three primary color images reconstructed by three CGHs. However, chromatic aberrations occur in the reconstruction, because incoherent light sources such as LED are commonly used for the illumination. Since these chromatic aberrations change dependently on the design-wavelengths of CGHs as well as the shape of illumination spectra, optimization techniques based on simulated reconstruction of CGHs is presented to obtain the most unobtrusive color aberration from spectra specific to the light source.
High-definition computer holography based on the polygon-based method commonly uses the silhouette method to shield light behind objects for hidden surface removal. However, the light-shielding is not perfect and causes leakage light passing through many gaps between silhouette-shaped masks. Although we have proposed the principle of more rigorous technique to remove the leakage light, the technique has never been applied to the actual high-definition computer holography because of its long computation time. We propose some techniques to reduce the computation time and apply the rigorous technique to high-definition computer holography. A CGH created by the proposed method is demonstrated.
A simple and practical technique is presented for creating fine three-dimensional (3D) images with polygon-based computer-generated holograms. The polygon-based method is a technique for computing the optical wave-field of virtual 3D scenes given by a numerical model. The presented method takes less computation time than common point-source methods and produces fine spatial 3D images of deep 3D scenes that convey a strong sensation of depth, unlike conventional 3D systems providing only binocular disparity. However, smooth surfaces cannot be reconstructed using the presented method because the surfaces are approximated by planar polygons. This problem is resolved by introducing a simple rendering technique that is almost the same as that in common computer graphics, since the polygon-based method has similarity to rendering techniques in computer graphics. Two actual computer holograms are presented to verify and demonstrate the proposed technique. One is a hologram of a live face whose shape is measured using a 3D laser scanner that outputs polygon-mesh data. The other is for a scene including the moon. Both are created employing the proposed rendering techniques of the texture mapping of real photographs and smooth shading.
Recently, the demand to the diffractive optical element (DOE) is increasing with the developments in the
technology. We created a relative large holographic optical element (HOE) with same course of production
of the DOE. To make the person who is situated on the long distance recognize image data using the hologram,
the hologram must have bright image reconstruction ability and a high SN ratio. Therefore, we made
the multi-level phase type hologram for the former and measured the optical intensity of the reproduction
image. For an evaluation method of the diffraction efficiency, we used 2-, 4-, and 8-level phase type Fresnel
Zone Plate (FZP).
Because it supposed that the amount of object was large, it adopted a computer-generated hologram
(CGH). Also, it used laser direct write lithography system that has the feature of high-resolution drawing,
high-speed drawing, and a high accuracy positioning system, for the making of hologram.
Image-type binary CGHs, fabricated by a laser lithography system, commonly lost the object shading and
texture. This is caused by the binary amplitude fringe that is unable to reconstruct object brightness because
amplitude information of the object field is removed by binarization if the object is too close to the hologram.
In this paper, optimized error diffusion is applied to encoding binary-amplitude image-type CGHs in order to
improve reconstruction of surface shading and texture. An actual image-type high-definition CGHs is created by
the proposed technique and demonstrated to verify that the CGHs can be reconstructed by white light source
without much chromatic aberration.
Novel techniques is proposed for rendering specular smooth surfaces in polygon-based computer holography
that features reconstruction of fine 3D images accompanied with strong sensation of depth. The technique is
an improvement of the conventional technique for rendering flat specular surfaces. In this technique, phase
distribution that works as a diffuser is divided into small rectangular segments and the reflection direction is
controlled for each segment. In addition, this new method increases freedom for lighting the object. Two
high-definition CGHs are calculated by the proposed method. One of them is fabricated and demonstrated for
verifying the technique.
Recent development of computer algorithms and micro fabrication technologies allows us to reconstruct the
wave-field of light emitted from a completely virtual 3D scene given by the numerical model. In addition, recent
evolution of image sensors and a technique for capturing real object waves makes it possible to digitize the whole
process of classical holography. The wave-field of the virtual, real, and hybrid scene are optically reconstructed
by the computer holograms fabricated by laser lithography system. The produced spatial 3D images have a
wide viewing-zone in full-parallax and give viewers a strong sensation of depth, which never has been caused by
conventional 3D systems.
KEYWORDS: Computer generated holography, Holography, 3D image reconstruction, 3D image processing, Digital holography, 3D metrology, Venus, 3D scanning, Reflection, Photography
Four novel techniques are introduced into polygon-based high-definition CGHs (PBHD-CGH) that feature the
true-fine spatial 3D image accompanied with a strong sensation of depth. The first is algorithm for creating
specular surfaces based on Phong reflection model. This is very useful for providing a feel of material to polygonal
surfaces. The second technique is called digitized holography that replaces the entire processes of classical
holography by their digital counterparts. The wave-field of real-existent objects can be optically reconstructed
by the digitized holography. This technique makes it possible to edit the 3D scene of holograms or create mixed
3D scene of the real and virtual objects. Another technique for creating PBHD-CGH of real-existent objects is
also proposed by a CG-like method using a 3D laser scanner that measures the 3D shape of the object. Finally,
a prototype PBHD-CGH is demonstrated for creating landscape scenery. This CGH is intended to reconstruct
a scene as if the viewers see mountain scenery through the window given by the CGH.
A large-scale CGH named "The Venus", created by using the polygon-based method, was demonstrated in the last year. However, the 3D scene of the Venus is restricted by the shifted Fresnel method used for numerical propagation using segmented frame buffers, because severe aliasing errors are produced if the propagation distance is shorter than a specific value in the method. In this paper, a novel method referred to as the shifted angular spectrum method is proposed for short distance propagation using the segmented frame buffers. The method can remove the restriction and give flexibility to design of 3D scenes. Both CGHs calculated by old and new methods are demonstrated.
A novel technique is presented for calculating large-scale CGHs by using polygon-based method. In the technique,
wave fields are regionally segmented and propagated by using the shifted Fresnel method. As a result, large CGHs
can be calculated even in the case that the whole frame buffer can not be stored in main memory. The produced
full-parallax CGH has the size of four billion pixels and reconstructs the fine image of a smooth surface object
accompanied with a strong depth sensation.
It has reported that a waste of an electronics substrate including lead and its compound such as 63Sn-37Pb has polluted the environment with acid rain. For that environment problem the development of lead-free solder alloys has been promoted in order to find out the substitute for Sn-Pb solders in the United States, Europe, and Japan. In a present electronics industry, typical alloys have narrowed down to Sn-Ag-Cu and Sn-Zn lead-free solder. In this study, solderability of Pb-free solder that are Sn-Ag-Cu and Sn-Zn-Bi alloy was studied on soldering using YAG (yttrium aluminum garnet) laser and diode laser. Experiments were peformed in order to determine the range of soldering parameters for obtaining an appropriate wettability based on a visual inspection. Joining strength of surface mounting chip components soldered on PCB (printed circuit board) was tested on application thickness of solder paste (0.2, 0.3, and 0.4 mm). In addition, joining strength characteristics of eutectic Sn-Pb alloy and under different power density were examined. As a result, solderability of Sn-Ag-Cu (Pb-free) solder paste are equivalent to that of coventional Sn-Pb solder paste, and are superior to that of Sn-Zn-Bi solder paste in the laser soldering method.
In order to attempt the direct laser marking for ROM media like a compact disk for identification, various laser heating was carried out against a thin metallic film in the transparent medium. As heat sources for the processing, a semiconductor laser excitation YAG laser (532 nm wavelength of second harmonic, max 150 mW), semiconductor lasers (780 nm, up to 2 W), and an Ar ion laser (514.5 nm, max 2000 mW), etc. were used. The media under consideration on laser marking is an aluminum thin film reflector layer, which was sandwiched between a polycarbonate (PC) of 1.2 mm and a protection film of 5 μm thickness. The aluminum thin film (Al) is 100 nm in thickness. The obtained laser marking sizes were less than 1 μm and were evaluated using SEM and AFM. The observation samples inside a transparency resin were obtained by tearing off a protection film, and the surfaces of the bared PC and protection film were examined. The surface conditions and cross sections of laser-marking area were observed. It seems that the heated aluminum thin film were melted and a hole arose. Then a cavity was not observed from SEM cross-section observation in the marking area. It became clear that the holes were filled with PC by SEM and AFM observation. These results indicate the possibility of heat localization at the Al-PC interface and also significant heat penetration into the PC substrate itself.
The Initializer which has a mechanism that allows for the rotating of the optical disk and scanning the laser head to radial direction, and Initializing the phase-change optical disk with spiral pattern, has basic problems which are caused by this mechanism. In this mechanism, the ruggedness of the laser diode is transcribed on the recording material of the optical disk. This report about the method of reflecting the laser light by the parallel millers that are installed in both sides of the light beam after collimating lens. The reflected lasers light by the parallel millers are focusing on the recording material of the optical disk with the manner of folding. If the reflected time of the lasers light is only one, it is making the 180 degreed rotated images from un-reflected image. And the multiple times reflected laser light make the image at a slightly moved place. So the folded focus image of laser diode is more uniformed compared with the original one and reduces the quality problem, which is caused by un-uniformity of initializing of Phase-Change Optical Disk.
Experimental studies on the characteristics of holographic lens were carried out, aiming at the simultaneous soldering of multi-spots in electronic assembly by the use of YAG laser. Holograms were recorded on the commercial available photographic plates, and converted into transparent phase type holographic lens by chemical processing. The dependencies of the diffraction efficiency on the recording conditions and two chemical treatment methods of silver halide sensitized gelatin and rehalogenating bleaching were examined in CW YAG laser system ((lambda) equals 1.06 micrometers ).
KEYWORDS: Crystals, Near field optics, Near field, Semiconductor lasers, Optical discs, High power lasers, Standards development, Laser processing, Head, Laser crystals
The method and the device, which initializes phase change media standardized by formats of such as CD-RW, record type DVD and etc., are discussed. In these media it should be a state of the crystal phase with high reflectivity before recording. It is necessary to change into the crystal phase from amorphous phase in a usual state of as-depot. The method to scan the laser spot beam of the oval shape that could be processed by a more high-speed, slighter control was examined. Because the life of laser and the scanning speed of beam spot are important factors that influenced the processing cost, the life of the laser and the improvement of the process speed are considered. The most much relating to the quality of media of finished products is near field pattern of the laser. Initializer in the mechanism, which can be used in the mass production line, is designed.
Solderability of conventional Sn-37Pb solder pastes and Pb- free alloys (Sn-43Bi and Sn-2Ag-5Bi-0.5Cu) were examined on micro soldering using a YAG laser. Experiments were performed in order to determine the range of soldering parameters of a laser power density and an irradiation time for obtaining an appropriate wettability based on a visual inspection by a Japanese Industrial Standard. And the laser soldering processes were monitored by measuring temperature change inside solder joint (solder and Cu pad) and on a surface of a chip component. Next joining strength of chip components for surface mounting soldered on printed circuit board (glass epoxy) was tested on application thickness of solder paste (0.2, 0.3, and 0.4 mm). In addition, joining strength characteristics at different power density and materials were examined around thermal shock test by the gas phase method. As a result, characteristics of Sn-Ag-Bi-Cu (Pb-free) solder paste are equivalent to that of Sn-Pb solder paste.
The surface conditions of holographic materials were studied with atomic force microscopy (AFM). Holograms were made using Agfa 8E75 plates with two different types of developer and bleaching methods for the purpose of obtaining holograms of high diffraction efficiency. Developers and bleaches were based on Pyrogallol and Kodak D-19, and on potassium dichromate and potassium iodide, respectively. The observation area ranged from hundreds of nm to tens of microns and z (depth) from a few nm to hundreds of nm in ordinary circumstances. The AFM images of the relief pattern of holograms and the size and shapes of silver halide grains after bleaching were obtained in ambient air without coating.
The laser speckle photography method is applied to study the deformation behavior of aluminum, stainless steel and high-purity alumina ceramics specimens during the cooling down process from the room to the liquid nitrogen temperatures. The in-plane displacements were measured by the image plane speckle photography and the out-of-plane displacements by the defocused speckle photography, respectively. The surface of ceramics specimen was coated with vacuum-evaporated aluminum film to keep the correlation of speckle patterns during the cooling down process. The experimental values of the in-plane displacement are compared with those of the FEM thermal analysis. The applicability of laser speckle photography method to cryogenic engineering is discussed.
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