KEYWORDS: Holography, 3D image processing, 3D image reconstruction, Laser development, Digital holography, Holograms, 3D displays, Digital video recorders, Video, Cameras
A holographic video camera with use of a high-power pulsed laser is developed for recording time-sequential 3-D
images of moving objects by applying one-shot digital holography. Recorded off-axis holograms are transmitted to a
computer where the 0-th order and the conjugate beams are eliminated by fast data processing, and digital output signals
from the computer are transmitted to a holographic LCD display system to reconstruct moving 3-D images. Optical
experiments demonstrate that complex-amplitude holograms are recorded under room lighting, and that moving 3-D
images are reconstructed from the holographic display system in real time.
A lens-less holographic microscopy is developed for observation of high-resolution 4-D (spatio-temporal) images. A
complex-amplitude in-line hologram with a large numerical aperture is extracted from a large off-axis hologram by
applying one-shot digital holography. An angular spectrum method is developed for fast numerical reconstruction of
precise 3-D image from the in-line hologram with a large numerical aperture. 3-D intensity and phase images with no
distortion, with a resolution higher than 1μm, and with a depth larger than 1mm are recorded and reconstructed by the
present holographic microscopy. Possibility is demonstrated to realize 4-D measurement of microorganisms swimming in water.
A new method is developed for recording and reconstructing a microscopic high-resolution 3-D image with no
distortion. Any imaging lens is not located between an object and a CCD in our optical system. An off-axis hologram
with a large numerical aperture is recorded at once, and a complex-amplitude in-line hologram is extracted from the
recorded off-axis hologram by applying the one-shot digital holography. A small complex-amplitude in-line hologram is
generated for the reconstruction of microscopic high-resolution images by dividing the large hologram into a number of
small holograms and by superimposing them. A focus-free image with high resolving power and no distortion is
reconstructed from the generated complex-amplitude in-line hologram. Resolution higher than 1μm is obtained in the
optical experiment, which can be improved up to the wave length. Microscopic high-resolution images with no distortion
can also be observed for objects immersed in the liquid or in the solid by using the lens-less holographic microscope.
KEYWORDS: Holograms, 3D image reconstruction, Digital holography, Fringe analysis, Spatial frequencies, Beam splitters, Data modeling, 3D acquisition, Speckle, 3D metrology
A new method is proposed for instantaneous measurement of 3-D shape of moving objects with rough surface by using
one-shot digital holography. The principle of proposed method consists of projection of interference fringes with a
constant period on surfaces, one-shot recording of the complex-amplitude in-line hologram, elimination of speckle from
reconstructed images, and calculation of depth from focus. The acquisition time is less than 1 micro-second needed for
recording one hologram. Speckles appeared in reconstructed images are eliminated into a low level by filtering.
Following the method of depth of focus, we can precisely determine 3-D position of each point on the surface. Accuracy
higher than 0.01% is obtained in the experiment of depth measurement because of low-level speckles.
Single-shot digital holography is developed for instantaneous recording of the complex-amplitude inline hologram by
applying spatial heterodyne modulation and spatial frequency filtering. The complex-amplitude in-line hologram can be
precisely extracted from one off-axis hologram for the reference light beam with general spatial phase distribution.
Bandwidth of the complex-amplitude hologram is enlarged up to a half of the spatial sampling frequency by eliminating
the zero-order term from the off-axis hologram, which is a theoretical upper limit in the single-shot recording.
Experimental results show that fine images are reconstructed from the complex-amplitude hologram as a result of
elimination of the direct light beam and the conjugate beam.
A new method is developed for recording and reconstructing a microscopic high-resolution 3-D image with large depth.
Any imaging lens is not located between the object and the CCD in our optical system. A number of partial off-axis
holograms are sequentially recorded with one CCD, or are recorded at once with multi-channel CCD by the single- shot
digital holography. Partial complex-amplitude in-line holograms are extracted from recorded off-axis holograms by
applying the simple-shot digital holography, and are arranged in order to generate a wide complex-amplitude in-line
hologram. A high-resolution image with no distortion is numerically reconstructed from the wide complex-amplitude inline
hologram.
A new method of the lens-less holographic microscope is proposed for recording a high-resolution 3-D image with large
visual depth. The light beam with a large viewing angle diffracted from the object surface is recorded by illuminating the
three-dimentional object with a large incidence angle. A number of partial holograms are sequentially recorded with one
CCD located at the fixed position by changing an incident angle of illumination light. These partial holograms are
arranged in order to generate a hologram with large viewing-zone angle for the reconstruction of a high-resolution
image. Optical experiments are carried out to demonstrate the present new method of the holographic microscope.
Results show that a high-resolution image is reconstructed from the wide hologram generated from a number of partial
holograms and the resolving power of reconstructed image is improved as the number of partial holograms becomes
large.
A new technology of one-shot digital holography is developed for instantaneous recording of the complex-amplitude
hologram for color three-dimensional images. Three holograms for different phases of the reference light are obtained
both by spatially sampling an off-axis hologram and by interpolating sampled hologram data, and the complex-amplitude
hologram is extracted from these three holograms. The one-shot holography is generalized for recording the hologram
with the reference light having general phase distribution, and the limitation of bandwidth in one-shot holography is also
discussed. Numerical simulation and optical experiment are carried out to demonstrate one-shot recording of the
complex-amplitude hologram. Results show that fine color images with high resolution are reconstructed from the
complex-amplitude hologram as a result of perfect elimination of the direct beam, the zero-order noise and the conjugate
beam. The one-shot digital holography can make possible to record color images of the moving object by adopting RGB
pulse lasers, and to reconstruct moving color images in real-time with the holographic display
Effects of the light-modulation characteristics of a LCD panel on the image reconstruction are discussed. Experimental
results show that the optical images are lower in quality than the numerical ones reconstructed from the same hologram.
Effects of the bit-depth limitation in quantization, and the phase change of modulated light are studied by the numerical
simulation. Simulation results indicate that the nonlinear characteristics of the LCD panel and the phase change of
amplitude-modulated light can have considerable influences upon the quality of images. Especially, the contrast of
images becomes low. The static or the dynamic characteristics are measured for LCD panels by using the holographic
technique, and their effects on the image reconstruction are discussed. New methods are also described for improving the
quality of images reconstructed from the holographic display. The nonlinear response of the LCD panel and the phase
change of modulated light can be made correction for the improvement of image quality by modifying the complexamplitude
hologram.
Quality deterioration of reconstructed 3-D images in the electro-holography is discussed. Effects of the bit-depth
limitation in quantization, of the phase shift of light caused by the amplitude modulation, and of the amplitude limitation
are studied by the numerical simulation. Comparison of optically reconstructed images with numerically reconstructed
images shows that the nonlinear characteristics of a LCD panel and the phase shift of light due to the amplitude
modulation have significant influences upon the quality of reconstructed images. Especially, the contrast of optically
reconstructed images becomes remarkably low. New methods are described for improving the quality of reconstructed
images in the experiment. The nonlinear characteristics of the LCD panel and the phase shift of the modulated light can
be made correction by data processing in the electro-holography.
A new technology of one-shot digital holography is developed in order to record the complex-amplitude hologram for
color three-dimensional images instantaneously. Off-axis RGB digital holograms are recorded with a color CCD at once,
and three or four in-line holograms with different phases are obtained by spatially sampling the recorded holograms and
by interpolating the sampled hologram data. RGB complex-amplitude holograms can be extracted for the reconstruction
of color 3-D images from the RGB in-line holograms without any numerical calculation of digital filtering. Numerical
reconstruction of images shows that fine color images with high resolution are reconstructed from the RGB complex-amplitude
in-line hologram as a result of elimination of the direct beam, noises and the conjugate beam.
A phase-shifting method by the SLM has been proposed for simultaneous recording of phase-shifted RGB holograms.
The phase of RGB lights can continuously be shifted by adopting a LCD panel. A system with a high-resolution
reflective LCD panel, a color CCD, and red, green, and blue lasers is developed for recording 3D color images. The
phase of RGB reference lights is precisely shifted by moving the diffraction grating on a reflective LCD panel. Since a
shifted value of the phase is independent of the wavelength of light in the present method, RGB interference fringe
patterns for the practical object can be recorded at once by adopting a high-resolution color CCD. Fine complex-amplitude holograms for reconstruction of RGB images are obtained from recorded interference fringe patterns,
and high-quality color images of the practical object are reconstructed from the holograms.
A time-sharing holographic color display system is developed using a high-resolution reflective liquid-crystal display (LCD) panel that consists of a 1920x1080 array of square pixels with the pixel pitch of 8.1 micron. Red, green and blue high-resolution images are reconstructed from the holographic display system with a red laser diode (LCD), a green diode-pumped laser and a blue diode-pumped laser. The reconstructed color image can clearly be observed under the room light. The image exhibits a large color gamut good color expression. High-quality color images of the practical object are reconstructed from recorded holograms by using the developed holographic display system. The viewing zone or the visual field of the holographic display is enlarged by adopting a multi-channel LCD modulator. The viewing zone angle or the visual field angle of color images is enlarged up to about 20 degrees by adopting a 6-channel LCD modulator.
A phase-shifting holographic system for recording 3D color images is developed with a color CCD, and red (R), green (G), and blue (B) lasers. The phase of reference lights in this recording system is precisely shifted by moving the diffraction grating displayed on a high-resolution reflective LCD panel. Measurement of the phase shift of the diffracted light demonstrates the feasibility of the phase-shifting method. RGB in-line holograms can be recorded at the same time for a practical color object by adopting a high-resolution color CCD. Color images in the wide visual field are recorded by adopting a multi-channel CCD and are reconstructed from the recorded hologram by adopting a multi-channel LCD modulator. Holograms for reconstruction of RGB images are obtained from recorded in-line holograms by the phase-shifting holography, and fine color images of high quality are reconstructed from recorded phase-shifting holograms. The visual field or the viewing zone of the holographic system is enlarged by adopting a multi-channel color CCD and a multi-channel LCD panel.
The superimposing method for information reduction in hologram is compared with the sampling method to clarify their features. 3D images with motion parallax are reproduced in the wide viewing zone from holograms with reduced information. The visual field is divided in several fields for displaying visual depth of the image under reduced information, and partial images in divided visual fields are separately recorded on several Fourier transform holograms (FTHs). A time-sharing display system is developed to reconstruct the 3D image in real time from several FTHs. Experiments are carried out for reconstruction of the practical 3D image from recorded holograms. Results show that resolution of the image is improved, and the speckle noise is suppressed by the superimposing method. Observer can perceive motion parallax of the image with wide viewing zone by viewing a pair of stereoscopic images from right-eye and left-eye positions. Observer can also perceive the correct visual depth of images through a parallax-fusing perceptual phenomenon.
KEYWORDS: LCDs, 3D image reconstruction, Holography, Displays, RGB color model, 3D image processing, Holograms, Reflectivity, 3D displays, Semiconductor lasers
A time-sharing holographic color display system is developed using a high-resolution reflective liquid-crystal display (LCD) panel that consists of a 1920x1080 array of square pixels with width of 8.1 micron. Red, green and blue images with high resolution are reconstructed from the holographic display system with a low-power red laser diode (LD), a low-power green diode-pumped laser and a low-power blue diode-pumped laser. The reconstructed color image can clearly be observed under the room light. The image exhibits good color expression. Moving 3D color images with high quality are reconstructed from holograms displayed on the LCD panel of the developed holographic system.
The superimposing method is described in order to reduce information in hologram. This method improves loss of
resolution and increase of the speckle noise which are caused by the information reduction in the sampling method.
Experiments are carried out for reconstruction of images from the computer-generated hologram or from the practical
hologram. Results show that high-resolution images with low speckle noise are reconstructed from the continuous
periodic hologram with reduced information. The image without visual depth is reconstructed on the Fourier transform
plane from the hologram with reduced information, if the bandwidth is taken to be smaller than the diameter of
observer's pupil. The visual field is divided into several fields in order to display images with visual depth, and images
in divided fields are recorded on several Fourier transform holograms. A time-sharing system with a movable reference
light source is developed in order to reconstruct real-time 3D images from several Fourier transform holograms with
reduced information.
A phase-shifting holography system for recording 3D color images is developed with a color CCD, and red (R), green (G), and blue (B) lasers. Phase of reference lights in this recording system is precisely shifted by shifting fringe patterns displayed on a high-resolution reflective LCD panel. Color images of the practical object are able to be recorded at the same time as RGB interference fringe patterns by adopting a high-resolution color CCD. Holograms for reconstruction of fine RGB images are obtained from recorded fringe patterns by the phase-shifting holography, and animated high-quality color images of the practical object are reconstructed from the holograms using the developed holographic color display system.
The superimposing method for information reduction in hologram is compared with the sampling method to clarify their features. Visual field is divided in several fields for displaying visual depth of the image under reduced information, and partial images in divided visual fields are separately recorded on several Fourier transform holograms (FTHs). A time-sharing display system is developed to reconstruct the 3D image in real time from several FTHs. The 3D image with motion parallax is reproduced in the wide viewing zone from holograms with reduced information by reconstructing overlapped two images. Experiments are carried out for reconstruction of the practical 3D image from recorded holograms. Results show that resolution of the image is improved and the speckle noise is suppressed by the superimposing method. Depth of the 3D image can be perceived by viewing partial images reconstructed on Fourier transform planes. Observer can perceive motion parallax of the image by viewing a pair of overlapped stereoscopic images from right-eye and left-eye positions.
A time-sharing holographic color display system is developed using a high-resolution reflective liquid-crystal display (LCD) panel that consists of a 1920x1080 array of square pixels with width of 8.1 micron. Red, green and blue highresolution images are reconstructed from the holographic display system with a red laser diode (LCD), a green diodepumped laser and a blue diode-pumped laser. The reconstructed color images can clearly be observed under the room
light. The images exhibit good color expression. High-quality color images of the practical object are reconstructed from the holograms by using the developed holographic display system. The viewing zone or the visual field of the holographic display is enlarged by adopting a multi-channel LCD modulator. 3-D full-color images are reconstructed in the wide visual field. Viewing zone angle or visual field angle of color images can be enlarged up to about 20 degrees
by adopting a 6-channel LCD modulator.
A phase-shifting holography system for recording 3D color images is developed with a color CCD, and red (R), green (G), and blue (B) lasers. The phase of reference lights in this recording system is precisely shifted by changing fringe patterns displayed on a high-resolution reflective LCD panel. RGB interference fringe patterns are able to be recorded at the same time for a practical color object by adopting a high-resolution color CCD. Color images in the wide visual field are recorded by adopting a multi-channel CCD and are reconstructed from the recorded hologram by adopting a multi-channel LCD modulator. Holograms for reconstruction of RGB images are obtained from recorded fringe patterns by the phase-shifting holography, and fine color images with high quality are reconstructed from recorded phase-shifting holograms by using the developed holographic color display system. The visual field of the holographic system is enlarged by adopting a multi-channel color CCD for recording of the image and a multi-channel LCD panel for reconstruction of the image.
A time-sharing holographic color display system is developed using a high-resolution reflective liquid-crystal display (LCD) panel that consists of a 1920x1080 array of square pixels with width of 8.1 micron. Red, green and blue images with high resolution are reconstructed from the holographic display system with a red laser diode (LD), a green diode-pumped laser and a blue diode-pumped laser. The reconstructed color image can clearly be observed under the room light. The images exhibit good color expression. A phase-shifting holography system is also developed in order to record 3D color images, where phase of the reference light is shifted by changing fringe patterns displayed on the reflective LCD. Color image of the practical object are recorded as RGB fringe patterns by adopting a high-resolution color CCD. Clear RGB holograms are obtained from recorded fringe patterns by the phase-shifting method, and moving color images with high quality are reconstructed from the holograms by using the developed holographic display system.
The superimposing method is described in order to reduce information in hologram. This method improves loss of resolution and increase of the speckle noise due to the information reduction as compared with the sampling method. Experiments are carried out for reconstruction of images from the computer-generated hologram or from the practical hologram. Results show that high-resolution images with low speckle noise are reconstructed from the continuous periodic hologram with reduced information. The image having no parallax is reconstructed on the Fourier transform plane from the hologram with reduced information, if the bandwidth is taken to be smaller than the diameter of observer’s pupil. A time-sharing system is developed in order to display real-time 3D images with full parallax using several Fourier transform holograms with reduced information.
KEYWORDS: Holograms, 3D image reconstruction, 3D image processing, Visualization, Image resolution, Distortion, 3D displays, Spatial frequencies, 3D modeling, Holography
A method of hologram bandwidth reduction and a method of size change of a 3D image are described. Spatial
frequency bands of a Fourier-transform hologram (FTH) are superimposed for reduction of the bandwidth and for
production of a continuous periodic FTH. Resolution of the image is improved by the superimposing method. The
second hologram for reconstruction of the magnified 3D image is produced by connecting a number of small holograms
clipped from the original FTH. Image depth capable of magnification is extended using several FTHs. Experiments
using the CGH shows that depth of the 3D image can be perceived by watching images reconstructed on many Fouriertransform
planes with different distances from the hologram. It is also shown that numbers of rays of light illuminated
from the second hologram reconstruct similar 3D images of various sizes of the same object. Distortion of the image
due to the magnification can be avoided over the wide range of magnifying power.
A real-time color holography system is developed using a high-resolution reflective liquid-crystal display (LCD) panel
that consists of a 1400x1050 array of square pixels with width of 10.4 micron. Red, green and blue images with high
resolution are reconstructed from the holography system with a red laser diode (LD), a green laser and a blue lightemitting
diode (LED) as the reference light. The reconstructed color image with high resolution can clearly be observed
under the room light. Directly viewable color images with both eyes or images in the wide visual field are reproduced
using the 3-channel LCD modulator. The viewing-zone angle or the visual-field angle of the 3-D display system can be
expanded up to about 9 degrees using three LCD panels. Fringe patterns for a practical object are also recorded by a
high-resolution CMOS sensor, and a moving image of the object is reproduced from the fringe patterns by the
developed holographic display system.
A method of changing in size of a three-dimensional (3D) image using a Fourier transform hologram (FTH) or a periodic FTH is described. Here, the periodic FTH is made for information reduction in hologram by superimposing a number of identical FTHs. The second hologram for reconstruction of magnified 3D images is reproduced by connecting a number of small holograms clipped from the original FTH or from the periodic FTH. Numerical calculations and experiments using the computer-generated hologram (CGH) have show that numbers of rays of light illuminated from the second hologram produce a magnified similar 3D image. Distortion of the image owing to the magnification can be avoided by reconstructing the image from a number of small holograms. Resolution, which depends on the magnifying power of the image and on the size of small holograms, is estimated by the numerical calculation.
A new method of information reduction in hologram is described. Loss of resolution due to the information reduction is improved by superimposing spatial frequency bands of a Fourier transform hologram. Superposition of a number of identical Fourier transform holograms, which deviate each other with a small distance, forms a continuous periodic Fourier transform hologram. The second hologram for the reconstruction of an image is reproduced by repetition of a small area of the continuous periodic Fourier transform hologram. Experiments have been carried out to examine the reconstruction of 3-D images by using computer-generated holograms (CGHs). Results of the experiments show that a high-resolution image is reconstructed from the second hologram produced by superimposing spatial frequency bands. The information reduction effects on the imaging, so that the reconstructed image is spatially sampled with a constant pitch.
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