The accommodation and convergence responses in a light field display which can provide up to 8 images to each eye of viewers are investigated. The DOF (Depth of Field) increase with the increasing number of projected images is verified for both monocular and binocular viewings. 7 subjects with eye sights greater than 1.0 reveal that their responses can match to their real object responses as the number of images increased to 7 and more, though there are distinctive differences between objects. The matching performance of the binocular is more stable than that of the monocular viewing for the number of images less than 6. But the response stability of the accommodation increases as the number becomes more than 7.
Color moirés induced at contact-type multiview three-dimensional and light-field imaging are reviewed, slanted color moirés are introduced, and the reason why they become invisible as the slanting angle increases is explained. The color moirés in the imaging are induced by the structural uniqueness of the imaging, i.e., viewing zone-forming optics (VZFO) on the display panel. The moirés behave differently from those by the beating effect. They are (1) basically chirped, (2) their fringe numbers and phases are also varying according to the changes in viewer’s viewing positions and viewing angles at a given viewing distance, (3) the pattern period of the VZFO is at least more than several times that of the pixel pattern, and (4) they are colored. The color moirés can hardly be eliminated because they are induced structurally, but they can be minimized by either reducing the regularity of the pixel pattern using a diffuser between the panel and the VZFO or aligning VZFO’s pattern to have a certain slanting angle with the pixel pattern in the panel.
A simulator which can test the visual perception response of light field displays is introduced. The simulator can provide up to 8 view images to each eye simultaneously to test the differences between different numbers of different view images in supermultiview condition. The images are going through a window with 4 mm width, which is located at the pupil plane of each eye. Since each view image has its own slot in the window, the image is separately entring the eye without overlapping with other images. The simulator shows that the vergence response of viewers' eyes for an image at a certain distance is closer to the real object of the same distance for 4 views than 2 views. This informs that the focusable depth range will increase more as the the number of different view images increases.
An aperture sharing camera to acquire multiview images are introduced. The camera is built with a mirrorless camera and a high speed LC shutter array which is located at the entrance pupil of the camera’s objective, to divide the pupil into a number of sections with an equal dimension, The LC shutters in the array is opened one at a time in synchronizing with the camera shutter. The images from neighboring shutters reveal a constant disparity between them. The disparity between the images from the camera matches closely with that calculated from theory and is proportional to the distance of the each LC shutter from the camera’s optical axis.
The resolution of the reconstructed image from a hologram displayed on a DMD is measured with the light field images along the propagation direction of the reconstructed image. The light field images reveal that a point and line image suffers a strong astigmatism but the line focusing distance differences for lines with different directions. This will be astigmatism too. The focusing distance of the reconstructed image is shorter than that of the object. The two lines in transverse direction are resolved when the gap between them is around 16 pixels of the DMD’s in use. However, the depth direction is difficult to estimate due to the depth of focus of each line. Due to the astigmatism, the reconstructed image of a square appears as a rectangle or a rhombus.
A super-multiview condition simulator which can project up to four different view images to each eye is introduced. This simulator with the image having both disparity and perspective informs that the depth of field (DOF) will be extended to more than the default DOF values as the number of simultaneously but separately projected different view images to each eye increase. The DOF range can be extended to near 2 diopters with the four simultaneous view images. However, the DOF value increments are not prominent as the image with both disparity and perspective with the image with disparity only.
Crosstalk in the contact-type multiview 3-D images is not an effective parameter of defining the quality of 3-D images. This is because the viewing zone in the contact-type multiview 3-D displays allows viewing the images which are composed of an image piece from each view image in a predefined set of consecutive view images, except the part along the viewing zone cross section. However, this part cannot guarantee to view individual view images separately because the viewing region of each view image is contacted to its neighboring viewing regions through a point for each neighbor due to its diamond like shape. Furthermore, the size of each view region can be smaller than the viewers’ pupil sizes as the pixel size decreases and/or the number of view images increases as in super-multiview imaging. The crosstalk has no meaning.
A simulator which can test a supermultiview condition is introduced. It allows to view two adjacent view images for each eye simultaneously and display patched images appearing at the viewing zone of a contact-type multiview 3-D display. The accommodation and vergence test with an accommodometer reveals that viewers can verge and accommodate even to the image at 600 mm and 2.7 m from them when a display screen/panel is located at 1.58 m from them. The verging and accommodating distance range is much more than the range 1.3 m ~ 1.9 m determined by the depth of field of the viewers. Furthermore, the patched images also provide a good depth sense which can be better than that from individual view images.
A simulator which can define super-multiview condition is introduced. This simulator can direct two different images to each eye of a viewer. The images are not only different view images but also images of different image cells in different positions in the viewing zone of a contact-type multiview imaging system having parallel configuration. This simulator will inform many conditions and requirements for multiview images to be a super-multiview. The presence of continuous parallax, the possibility of monocular depth sensing, required number of different view images, allowed pattern of different view image mixing, the optimum disparity between images are several examples of the conditions and requirements to be defined by the simulator.
A holographic display which is capable of displaying floating holographic images is introduced. The display is for user interaction with the image on the display. It consists of two parts; multiplexed holographic image generation and a spherical mirror. The time multiplexed image from 2 X 10 DMD frames appeared on PDLC screen is imaged by the spherical mirror and becomes a floating image. This image is combined spatially with two layered TV images appearing behind. Since the floating holographic image has a real spatial position and depth, it allows a user to interact with the image.
The viewing zone of a contact-type multiview three-dimensional imaging system are divided into nine viewing regions by assuming that at least n−2 pixel cells can be viewed at each of the regions, where n is the total number of pixel cells in horizontal direction of a display panel. Each of these regions consists of m 2 subregions, where m is the number of pixels in the horizontal of a pixel cell. The image viewed at each of the subregions reveals a disparity of 1 pixel distance with that viewed at its adjacent subregion. Hence, each subregion is defined as a basic image cell that can provide the disparity of a pixel distance with its immediate neighbors. The width of the cell is independent of the focal length of the viewing zone forming optics but highly sensitive to the pixel size. It can be smaller than viewers’ pupil sizes by decreasing the pixel size.
We present a new method to record and reconstruct a diffracted object wave field in all directions. For this, we
are going to use spherically-arranged holograms instead of a single spherical hologram. Our spherically-arranged
holograms are constructed to store all components of plane waves propagating in all directions. One can use the
well-known efficient FFT-based diffraction formulae such as Fresnel transform and angular spectrum method in
generation and reconstruction of our spherically-arranged holograms. It is possible to synthesize a new hologram
with an arbitrary position and orientation without the geometry of the object. Numerical experiments are
presented to show the effectiveness of our method.
A DMD chip is capable of displaying holographic images with a gray level and of reconstructing its image only in the
space defined by the diffraction pattern induced from its pixel arrangement structure. 2 X 5 DMD chips are combined on
a board to generate a spatially multiplexed reconstructed image of 10cmX2cm. Each DMD chip generates an image
piece with the size of 2cm (Horizontal) X 1cm (vertical). The reconstructed image reveals the features of original object
image including the gray level but noises from several sources are also laden with it.
Viewing sub-regions which are working as basic image cells in the viewing zone of electro-holographic display based on
a stereo hologram are defined and the composition of images viewed at these regions are found. Each of these subregions
can work as a basic image cell which provides a distinct image different from those of other sub-regions, though
each of them can be divided into pieces of different compositions. When the numbers of pixels in each pixel cell and
pixel cells in a panel, increase, most of these pieces will disappear because their sizes are smaller than the blurring caused
by diffraction effect. Furthermore, more than two sub-regions will within the pupil size of viewers’ each eye. This might
induce a continuous parallax to viewers to create the supermultiview condition.
The central and side viewing zones of pixel cell and elemental image based contact-type multiview 3-D imaging
methods, can be combined with between viewing zone to form a bigger viewing zone, i.e., a combined viewing zone.
The combined viewing zone of the elemental image based method has the same features as the viewing region in front of
the viewing zone cross section in that of the pixel cell based method. The combined viewing zone of the pixel cell based
method has almost 2 times of the viewing regions of viewing differently composed images with a pixel from each of
pixel cells/elemental images in the display panel. The front and behind viewing regions in the pixel cell based method's
combined viewing zone has a symmetrical relationship. The light intensity distribution supports these is facts.