Autostereoscopic three-dimensional display technologies using novel optical imaging systems based on retro-reflection with mirror arrays, a dihedral corner reflector array (DCRA) and a roof mirror array (RMA) are described. The proposed methods can generate a low-distortion aerial 3-D image with high numerical aperture on the basis of retro-reflection imaging. As the examples of 3-D displays based on retro-reflective imaging, a multi-view stereoscopic display using a DCRA and a volumetric display using a RMA were described. The multi-view stereoscopic display can achieve not only aerial image formation of display images but also that of the pupils of projectors around viewing position using a DCRA. This feature is effective in keeping consistency between accommodation and convergence cues for stereoscopic display. The volumetric display using a RMA can generate a 3-D image with natural depth information by light points are arranged in a 3-D volume using relatively simple optical configuration. This method can provide natural perception of depth and accessibility to an image. Experimental demonstrations of the generation of floating autostereoscopic images are presented to verify the validity of our proposed methods.
Optical design for several three-dimensional (3-D) displays based on floating real image formation using optical imaging
elements, such as a concave mirror and a micro-mirror array device, are described. A volumetric 3-D image consisting
voxels distributed in the air can be generated by moving a floating image with an optical scanner and modulating the
image at a high-speed frame rate. In addition, floating multi-view autostereoscopic displays implemented by using a
high-frame-rate projector and an optical scanner are described. It is possible to expand the viewing area to 360 degrees
around a floating image.
We propose a floating volumetric display system using a novel imaging element whose aperture is large and can be made
easily at low cost. Diffuse rays in a horizontal direction for an observer are formed by a 90º prism sheet, which has a shape
of an array of 90º V-grooves, as a result of twice total internal reflection. On the other hand, the diffuse rays in a longitudinal
direction for the observer are formed by a linear Fresnel lens. A formed image by the proposed imaging element does not
distort in the horizontal direction because the rays in the horizontal direction converge by retroreflection. The proposed
imaging element can be produced easier than a conventional distortion-free imaging element and display a larger floating
image. A floating three-dimensional image was displayed by a volumetric display system based on optical scanning of an
inclined image plane. A position of a two-dimensional real image formed by the proposed imaging element was moved by
an optical scanner at a faster rate than the duration time of persistence of vision. A stack of moved images created the
floating three-dimensional volume image.
This research aims to develop an auto-stereoscopic display, which satisfies the conditions required for practical use, such
as, high resolution and large image size comparable to ordinary display devices for television, arbitrary viewing position,
multiple viewer availability, suppression of nonuniform luminance distribution, and compact system configuration. In
the proposed system, an image display unit is illuminated with a direction-controlled illumination unit, which consists of
a spatially modulated parallel light source and a steering optical system. The steering optical system is constructed with a
slanted cylindrical array and vertical diffusers. The direction-controlled illumination unit can control output position and
horizontal angle of vertically diffused light. The light from the image display unit is controlled to form narrow exit pupil.
A viewer can watch the image only when an eye is located at the exit pupil. Auto-stereoscopic view can be achieved by
alternately switching the position of an exit pupil at viewer's both eyes, and alternately displaying parallax images. An
experimental system was constructed to verify the proposed method. The experimental system consists of a LCD
projector and Fresnel lenses for the direction-controlled illumination unit, and a 32 inch full-HD LCD for image display.
We propose to use a rotational optical scanning method for a volumetric three-dimensional (3D) display based on optical scanning of an inclined image plane. The image plane was moved by an image rotator and formed by a dihedral corner reflector array, which is a distortion free imaging element forming a real image at a plane-symmetrical position. A stack of the moved and formed image planes of a two-dimensional (2D) display created displayable space of a 3D image, which satisfies all the criteria of stereoscopic vision and can be seen by the naked eyes. The image rotator used in this study was constructed of prism sheets and planar mirrors. The image plane was moved rotationally by rotating the proposed image rotator on an axis parallel to the mirror plane. Enlargement of the displayable space is achieved by just extending the distance between the 2D display and the mirror, so that the proposed scanning method is effective to display a large 3D image for our volumetric display system. We made a prototype display and observed a moved image plane to measure the displayable space of the 3D image. The size of the displayable space was 1200 [cm3] that is approximately six times as large as our previous display using a translational optical scanning method.
KEYWORDS: Mirrors, 3D displays, Integral imaging, Imaging systems, 3D image processing, Scanners, Relays, Displays, Digital micromirror devices, 3D vision
The aim of this research is to develop a full-parallax auto-stereoscopic display system, which can generate a floating
three-dimensional (3-D) image viewable from a surrounding area. A 3-D display method based on the combination of
integral imaging, 360-degree scanning with a rotating mirror, and imaging in the air with a concave mirror is proposed.
A scanning system is composed of a hemisphere concave mirror and a mirror scanner, which is located around the center
of the concave mirror. By putting an image generated by an integral imaging system into the scanning system, a floating
stereoscopic image can be formed around the center of the concave mirror. When the mirror scanner rotates and the
image on the integral imaging system is switched in accordance with mirror angle, each directional image can be
observed from each viewing angle. The feasibility of the proposed method was examined by preliminary experiments.
The abilities of generation of a floating full-parallax image and a floating auto-stereoscopic image with 360-degree
viewing angle are demonstrated.
A volumetric display system using a roof mirror grid array (RMGA) is proposed. The RMGA consists of a
two-dimensional array of dihedral corner reflectors and forms a real image at a plane-symmetric position. A
two-dimensional image formed with a RMGA is moved at thigh speed by a mirror scanner. Cross-sectional images of a
three-dimensional object are displayed in accordance with the position of the image plane. A volumetric image can be
observed as a stack of the cross-sectional images by high-speed scanning. Image formation by a RMGA is free from
aberrations. Moreover, a compact optical system can be constructed because a RMGA doesn't have a focal length.
An experimental volumetric display system using a galvanometer mirror and a digital micromirror device was
constructed. The formation of a three-dimensional image consisting of 1024 × 768 × 400 voxels is confirmed by the
experimental system.
A novel technique for acquiring time-sequential images during a frame-capture period of an ordinary CMOS image sensor using a multi-lens optical system is proposed. In addition, this system is utilized for high-speed three-dimensional measurement based on a spatial encoding method. In the proposed image capturing system, multiple lenses are rhomboidally arranged on a CMOS image sensor to detect multiple images for one object. Because pixel values in the CMOS image sensor are obtained sequentially, we can obtain multiple images that are captured at different timing. In the spatial encoding method, several kinds of optical patterns are projected to a measured object. It is possible to obtain multiple images in which different patterns are projected to the object within one frame period by dividing the captured images and reconstruct images from rearrange the parts of image. The principle of the proposed method was verified by three-dimensional measurement with a CMOS compound-eye image capturing. The size of the three-dimensional image was 360 x 270 pixel, and the number of steps of distance was 64, and the measurement time was 1/15 seconds.
KEYWORDS: 3D image processing, 3D displays, Mirrors, 3D metrology, 3D volumetric displays, 3D scanning, Scanners, Intelligence systems, Digital micromirror devices
Volumetric display systems based on three-dimensional (3-D) scanning of an inclined image are reported. An optical
image of a two-dimensional (2-D) display device, which is placed obliquely in an optical imaging system, is moved
laterally by an optical mirror scanner. Inclined cross-sectional images of a 3-D object are displayed on the 2-D display
device in accordance with the position of the image plane. A locus of the moving image can be observed as a series of
moving afterimages as a result of high-speed scanning. A 3-D real image is thus formed as a stack of 2-D
cross-sectional images. This 3-D image can satisfy all the criteria for stereoscopic vision. A three-dimensional image
consisting of 1024 × 768 × 150 pixels was formed by the constructed system using a digital micro mirror device. In
addition, we propose a 3-D image transmission system, which can acquire the 3-D information of an object and display
it as a volumetric image in real time. We constructed a high-speed 3-D measurement system based on the light-section
method using an intelligent vision system, which can capture and process 1000 images per a millisecond. We
demonstrate real-time volumetric image generation from the measured profile using the 3-D measurement system and
the volumetric display system.
KEYWORDS: 3D displays, 3D image processing, Mirrors, 3D acquisition, Displays, 3D scanning, 3D volumetric displays, Imaging systems, 3D image reconstruction
A volumetric display system based on three-dimensional (3-D) scanning that uses an inclined two-dimensional (2-D) image is described. In the volumetric display system a 2-D display unit is placed obliquely in an imaging system into which a rotating mirror is inserted. When the mirror is rotated, the inclined 2-D image is moved laterally. A locus of the moving image can be observed by persistence of vision as a result of the high-speed rotation of the mirror. Inclined cross-sectional images of an object are displayed on the display unit in accordance with the position of the image plane to observe a 3-D image of the object by persistence of vision. Three-dimensional images formed by this display system satisfy all the criteria for stereoscopic vision. We constructed the volumetric display systems using a galvanometer mirror and a vector-scan display unit. In addition, we constructed a real-time 3-D measurement system based on a light section method. Measured 3-D images can be reconstructed in the 3-D display system in real time.
In photorefractive polymers, higher order diffraction and energy exchange are analyzed in two wave coupling configuration. The dependence of the second-order diffraction on the two-wave intensity ratio was simulated and investigated experimentally. The maximum value second- order intensity increases with increasing applied voltage, however for energy exchange of photorefractive polymer, beam ratio for the maximum second-order intensity shift from equal beam intensity. Using this programmable edge enhancement can be obtained by changing the voltage and incident beam intensity ratio.
A compact image capturing system called TOMBO (thin observation module by bound optics) is developed with compound-eye imaging and post digital processing. To demonstrate effectiveness of the TOMBO architecture, several prototype systems have been constructed with a refractive microlens array and a CMOS (complementary metal oxide semiconductor) image sensor. As a new algorithm for image reconstruction, the pixel rearrange method has been developed. With several test targets, the characteristics of the prototype systems are evaluated.
KEYWORDS: 3D image processing, 3D displays, Mirrors, Scanners, Oscilloscopes, 3D scanning, 3D image reconstruction, 3D vision, Displays, 3D acquisition
A new three-dimensional display system based on a volume-scanning method is demonstrated. To form a three-dimensional real image, an inclined two-dimensional image is rapidly moved with a mirror scanner while the cross-section patterns of a three-dimensional object are displayed sequentially. A vector-scan CRT display unit is used to obtain a high-resolution image. An optical scanning system is constructed with concave mirrors and a galvanometer mirror. It is confirmed that three-dimensional images, formed by the experimental system, satisfy all the criteria for human stereoscopic vision.
Optical tweezers have been used to trap and manipulate tiny particles including biological cells, viruses and microorganism in the biology field. By modifying the shape of the trapping object the rotation of the objects using radiation pressure was reported. Usually, these micro-objects are fabricated through complicated ion beam etching process. In this work, windmill-shaped micro-rotators are fabricated by simple photolithographic method and rotation properties are examined. The negative photoresist which is spin coated on the glass is placed in contact with photomask and illuminated with ultraviolet light from Hg lamp. The micro-rotator has four arms of 10 micrometers length and side surface area of each arm are different to surrounding medium. Because of the asymmetrical structure, rotational torque is generated when incident laser beam passes through the side walls of the micro-rotator. The rotation speed of the micro-rotator depends on the intensity of incident laser beam, thickness of rotator and focused position of laser beam. When the laser beam is focused slightly above the upper surface of the rotator, the maximum rotation torque is obtained. The rotation speed increases in proportion to incident laser power. For a micro-rotator of 10 microns thick, maximum rotation speed, 24 rpm is attained with a Ar laser power of 75mW.
An optical packaging scheme based on alignment-free optical modules for free-space interconnection is presented. Solder- bump-bonding technique is introduced to achieve precise self-alignment in free-space optical system. The proposed method is verified by experimental fabrication of optical modules.
A compact image capturing system called TOMBO (thin observation module by bound optics) is presented, in which a compound-eye imaging optics is utilized for very thin system configuration. The captured multiple images are processed to retrieve the object image. An experimental system was constructed for verifying the principle and clarifying the issues related on the implementation. For the retrieve, two kinds of processing are considered: simple sampling and back projection methods. The TOMBO system is an instance of opto- electronic hybrid system providing excellent features based on opto-electronic cooperation.
The characteristics of photorefractive polymer doped with PNP in optical image processing are investigated. PNP[(S)-(-)- N-(5-nitro-2-pyridyl)prolinol] is one of the high gain chromophore in polymeric photorefractive system. In the two wave coupling experiment, the gain coefficient about 180 is observed with 25 micron thick sample at 100 V/micrometer. Higher diffraction order and phase conjugation is also observed. This photorefractive thin film is used as a holographic recording device. Fourier transform hologram is recorded by using similar arrangement of two wave coupling configuration. The reconstructed image from the photorefractive film is edge-enhanced. Degree of enhancement depends on the intensity ratio of signal to pump beam. Decreasing the ratio of signal to pump beam, degree of edge enhancement decreases. When the object pattern is defocused on the film, degree of enhancement also decreases. Optical image processing system in which degree of edge enhancement is controllable can be constructed.
The alignment-free optical module based on a 2-f optical system and the optical microconnectors is proposed. Its availability is confirmed by experiments.
Photorefractive materials are of considerable interest for the development of optical devices. Recently, attention has been drawn to the photorefractive polymer owing to its excellent properties. In this paper, photorefractive polymer composite based on photoconductor poly(N-vinylcarbazole) (PVK) is described. As an electro-optic chromophore (S)-(-)-N-(5-nitro- 2-pyridyl)prolinol(PNP) is used in the composite. In order to decrease the grass transition temperature N-ethylcarbazole (ECZ) is added. A small amount of 2-4-7 trinitro-9 fluorenon (TNF) is also added to increase the photosensitivity in visible region. The composition is PNP:PVK:ECZ:TNF 50:33:16:1 wt%. The mixture of these materials is dissolved in THF and is stirred sufficiently. The PR samples are prepared by casting the mixture onto the glass plate and pressed another glass at about 140 C. The glass plates are coated with transparent electrode for application of the external electric field. The film thus obtained is light yellow and the optical absorption coefficient of this film is 25 cm-1 at 633 nm. Two coherent writing beams from He-Ne laser are overlapped in the sample to create a fringe pattern. From the measured increase and decrease in the writing beam powers, the two beam coupling gain coefficient is calculated. In our experiment gain coefficient is 101 cm-1 and 68 cm-1 for p- polarized and s-polarized light respectively at 100 V/10-6 m.
Reflective block optical systems have been used to achieve tasks realized by lens systems, but offering compactness and flexibility to construct optical computing systems. Thus, the reflective optical systems have to achieve optimal optical performance. In this work, we use the procedure of ALSIE (Automatic Lens Design By Solving Inequalities, T. Suzuki, et al., J. Opt. Soc. Am., 56, 677, 1966) to optimize reflective optical systems. To realize the optimization some specific considerations are discussed. The spherical aberration of a reflective optical system is optimized by the present method, showing the optimal optical performance.
A complete parallel version of hybrid optical parallel array logic system (H-OPALS 162) is constructed, which can process 16 X 16 pixels simultaneously at up to 19 kframs/sec. In the system, all pixels are processed and transferred in parallel. Experimental results, including parallel numerical processing and image processing, show capability and flexibility of the system.
An optoelectronic hybrid optical array logic system is experimentally constructed as an instance of the optical parallel array logic system (OPALS). In the experimental system, a coherent 2-D correlator with holographic filters and image encoder/decoder based on fully parallel electronic circuits are applied. Holographic filters for several kinds of simple processing are optically fabricated and correct operation of the system is verified. In the experimental system, 3 by 3 pixels are processed in parallel at the rate of about 278 operations per second. Sixteen logical functions and iterative operations are demonsirated.
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