Vertical Parallax Research Articles

Resolution of a reflection hologram recorded with a slit

Resolution of the reconstructed image is evaluated for the reflection hologram recorded by use of a slit. Sharp and deep images are obtained because the resolution in the vertical direction is higher than that of the conventional reflection holograms and is independent of the size of the illuminating light source. In contrast, the resolution in the horizontal direction depends on the light-source size in this direction. The optimum source size is discussed in connection with the balance in the resolutions for both directions. A method for obtaining the vertical parallax by use of multiple slits is proposed, and application of the proposed hologram to the heads-up display is also demonstrated.

Dynamic holographic imaging of the beating human heart

Background--Currently, the reporting and archiving of echocardiographic data suffer from the difficulty of representing heart motion on printable 2-dimensional (2D) media. Methods and Results--We studied the capability of holography to integrate motion into 2D echocardiographic prints. Images of normal human hearts and of a variety of mitral valve function abnormalities (mitral valve prolapse, systolic anterior motion of the mitral leaflets, and obstruction of the mitral valve by a myxoma) were acquired digitally on standard echocardiographic machines. Images were processed into a data format suitable for holographic printing. Angularly multiplexed holograms were then printed on a prototype holographic "laser" printer, with integration of time in vertical parallax, so that heart motion became visible when the hologram was tilted up and down. The resulting holograms displayed the anatomy with the same resolution as the original acquisition and allowed detailed study of valve motion with side-by-side comparison of normal and abnormal findings. Comparison of standard echocardiographic measurements in original echo frames and corresponding hologram views showed an excellent correlation of both methods (P<0.0001, r2=0.979, mean bias=2.76 mm). In this feasibility study, both 2D and 3D holographic images were produced. The equipment needed to view these holograms consists of only a simple point-light source. Conclusions--Holographic representation of myocardial and valve motion from echocardiographic data is feasible and allows the printing on a 2D medium of the complete heart cycle. Combined with the recent development of online holographic printing, this novel technique has the potential to improve reporting, visualization, and archiving of echocardiographic imaging.

Neon Color Spreading Promoted by Motion Information

We conducted experiments to investigate the effects of head-motion and object-motion to produce a perception of neon color spreading. Our experimental results indicated that a two-dimensional motion of yellow patches promoted the color spreading. A horizontal head-motion with motion parallax and three-dimensional pictorial depth information together with changing the viewing point stimulated the color spreading even, more than the two-dimensional motion. Thus, motion signals appear to offer useful information for the formation of a subjective contour and/or to activate the filling-in effect needed to generate neon color spreading. We also tested whether there was a difference between the effects of vertical and horizontal motion parallaxes for neon color spreading and found that there was none. This suggests that vertical head motion provides information in depth and surface perception equivalent to horizontal head motion.

Parallax image capture system for stereographic display

Recently, several three-dimensional (3-D) stereographic-type display systems that require both horizontal and vertical parallax images were invented. We propose a system to capture the parallax images for these display systems. Our system is based on the translation of a CCD camera with respect to a 3-D object for parallax image capturing. In addition, the mathematical relationship between the parallax images to be displayed and the images captured by the CCD camera is derived. The image calculation is very simple. Our relationship enables the 3-D object to be displayed anywhere in the space. In addition, we can easily animate different 3-D objects into single scene through our technique. © 1996 Society of Photo-Optical Instrumentation Engineers. Subject terms: electronic holography; holographic stereogram; stereo vision.

Are anterior occlusal radiographs indicated to supplement panoramic radiography during an orthodontic assessment?

Five hundred pairs of dental panoramic tomographs (DPT) and maxillary anterior occlusal radiographs (AO) from patients referred to the orthodontic department of a dental teaching hospital were examined to assess the diagnostic yield from a panoramic radiograph of the premaxillary region alone and then assess the additional yield when this view was supplemented by a maxillary anterior occlusal radiograph. Of the 500 DPTs assessed, 208 (42%) lacked clarity of the premaxillary region when the labial segments were used to locate the patient in the DPT machine. An association was found between patients who had abnormal incisor relationships and poor clarity in the premaxillary region of the DPT. Overall 165 (33%) of the supplementary AO views were used to support or refute findings identified on the DPT. It was concluded that in patients referred for an orthodontic assessment, supplementary radiography of the premaxilla may be justified in the following situations: 1. unsatisfactory image quality which may frequently be the case where there are abnormal incisor relationships, 2. localisation of tooth position by vertical parallax and 3. where a reasonable expectation that pathology exists on clinical grounds.

Viewing model for virtual environment displays

We present a viewing model that is appropriate for several types of displays used in virtual environment systems, including head-mounted displays and head-tracked stationary displays. The model accounts for arbitrary size, placement, and orientation of the display images, and thus is suitable for various display designs. We provide algorithms for calculating stereoscopic viewing and projection matrices. The tracking algorithm models the position and orientation of the tracker's emitter and the displacement between the sensor and the user's eyes. The algorithms are presented as parameterized homogeneous transforms. We also discuss features that can be used to avoid accommodation/convergence conflicts. The advantages of this viewing model and algorithm are the elimination of possible vertical parallax, an undistorted perception of depth, and reduction of eye fatigue due to excessive parallax. All of these factors contribute to improved comfort and utility for the operator.

Electrostatic and diffraction analysis of a liquid-crystal device utilizing fringing fields: applications to three-dimensional displays

The development and modeling of a liquid-crystal phase grating for real-time diffractive three-dimensional displays are discussed. The system being developed, which is called the ICVision system, utilizes a number of ideas that will result in a rugged, low-power three-dimensional display offering both vertical and horizontal parallax and eventually full color. Fringing fields created between interdigitated electrodes formed on top of VLSI die will induce a diffraction pattern in a thin layer of liquid crystal that will cover the die. A detailed electrostatic and diffraction analysis of liquid-crystal phase-grating regions that will make up the final display is given here. The electrostatic analysis is developed by use of the method of moments. The diffraction analysis is developed by use of rigorous coupled-wave diffraction theory. The numerical results obtrained from the mathematical model are compared with experimental diffraction results from preliminary LCD cells that have been assembled as prototype ICVision devices.

Multidot recording of rainbow and multicolor holographic stereograms

A new method for rainbow and multicolor holographic stereograms is described using the technique of multidot recording, which was originally developed for the syntheses of full-parallax holographic stereograms. Instead of recording vertical parallax, an image of horizontal slit is synthesized for rainbow holography. It becomes possible to obtain large images by a compact optical system, since the hologram is composed of many small elementary holograms. Multicolor image is also produced by the same system introducing a simple image processing. Experimental results of three-dimensional and color imagery are demonstrated.

Performance comparison of multiple image depth and shape cues

This research has implications for tasks in human‐computer interaction where the user must interact with display information that is organized on multiple axes. We describe the results of an experiment that compared the effectiveness of five different techniques for shape and depth discrimination. The methods evaluated were binocular parallax, alternating horizontal parallax, alternating vertical parallax, motion parallax, and motion parallax in conjunction with the Pulfrich effect. Binocular parallax, closely followed by motion parallax and the Pulfrich effect, was most effective for the depth discrimination task in terms of both correctness and response time. Alternating parallax techniques provided cues for distinguishing between foreground and background in a scene but did not provide cues that were intuitively translated into depth. Response time of subjects for the shape discrimination task was fastest with alternating parallax. For depth discrimination, subjects preferred binocular parallax. For sh...

Holographic three-dimensional printer: new method

We propose a holographic three-dimensional (3-D) printer that produces 3-D hard copies of computer data. A new technique for synthesizing a holographic stereogram (HS) has been invented for the purpose of making accurate hard copies of 3-D objects. The flat-format, Lippmann-type HS is printed by one optical step and is ideally suitable for 3-D printer application. This type of HS has both horizontal and vertical parallaxes so that the reconstructed image is free from distortion. The principle and the image quality of this type of HS are described, and a reconstructed image from this type of HS with 160 x 128 elements is experimentally demonstrated. The systematic constitution of a holographic 3-D printer is also discussed.

Single lens stereo with a plenoptic camera

Ordinary cameras gather light across the area of their lens aperture, and the light striking a given subregion of the aperture is structured somewhat differently than the light striking an adjacent subregion. By analyzing this optical structure, one can infer the depths of the objects in the scene, i.e. one can achieve single lens stereo. The authors describe a camera for performing this analysis. It incorporates a single main lens along with a lenticular array placed at the sensor plane. The resulting plenoptic camera provides information about how the scene would look when viewed from a continuum of possible viewpoints bounded by the main lens aperture. Deriving depth information is simpler than in a binocular stereo system because the correspondence problem is minimized. The camera extracts information about both horizontal and vertical parallax, which improves the reliability of the depth estimates.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Rotation algorithm artifacts in stereoscopic images

We examine the effect of using rotations for generation of the left- and right-eye perspective views of a stereoscopic image. We show that this approach to stereoscopic display of perspective views results in vertical parallax between the left- and right-eye views and we present an analytic expression that characterizes this parallax in terms of the center of rotation, the location of the image plane, and the angle of rotation. We also derive an analytic expression that shows that the rotation of the perspective views results in a semicylindrical stereo window with center at approximately (0, 0, P12) and radius R/2, where R is the distance from the center of rotation to the center of projection. When this semicylindrical window is mapped to a flat display surface, relative depth relationships can be distorted.

Some variations on VISIDEP using computer graphics

Previous researchers have applied vertical motion parallax using video cameras; these attempts were published under the VISIDEP trademark. Alternatives are examined that can exploit computer graphics. Such techniques include choosing different locations for the axis of rotation and using multiple images versus dual images to make the motion smoother. These techniques as well as others are described and compared for effectiveness in enhancing depth.

Visual image depth enhancement process: an approach to three-dimensional imaging

Three-dimensional displays utilizing the alternating frame technique, especially the visual image depth enhancement (VISIDEP) method, are described. Recent advances and variations of these techniques have led to improvement in image quality and stability. Special attention is given to the unique application of vertical parallax. The addition of signal mixing and the use of composite images provide further refinement. Some combination and/or variation of these techniques may ultimately achieve depth without discernible motion.

Three-dimensional imaging of x-ray and gamma-ray objects in real time

A simple device is described that is capable of providing real-time 3-D viewing of extended x-ray and gamma-ray objects. The visible-light images produced by the device are not merely stereoscopic, i.e., one perspective, but possess both horizontal and vertical parallax with a reasonably large field of view.

Visually Scanning 4-Dimensional Objects with the Aid of Hyperstereograms in Color

Several years ago, while experimenting with drawings showing stereoscopic pairs of projections of some 4dimensional geometrical objects, hyperobjects, I discovered a new way to look at or scan such hyperobjects. Visualizing certain hyperobjects has been considered by others, too. Recently B. L. Chilton described one method in an article in Leonardo [1]. He presented a set of drawings each showing a view of one regular polyhedron that is a projection (a 3-dimensional shadow in a hyperplane) of a hyperobject. Ordinary stereograms may be employed to visualize objects and scenes in three dimensions, and examples of their use in visual art have been provided by H. A. Layer [2] and by Roger Ferragallo [3]. The stereoscopic pairs of projections that I use in visualizing hyperobjects I call hyperstereograms. Hyperstereograms and ordinary stereograms differ in an important way. In an ordinary stereogram, the corresponding points in the two images, such as in Fig. 1, are displaced equal distances above,or below, a given reference point (for example center point 0) but not equal distances to the right, or to the left of it (parallax) [3]. In binocular vision the unequal horizontal displacements of corresponding points in what is received by the eyes leads to the perception of an object in three dimensions. In such examples of horizontal parallax, two images are 'fused', subjectively in the brain, to produce a single 3-dimensional image. In a hyperstereogram, inequalities occur in both the vertical and horizontal distances of corresponding points from a reference point; there is both horizontal and vertical parallax. This occurs because the rotation of a 4-dimensional form is a rotation around a plane, whereas the rotation of a 3-dimensional form is rotation around a line, that is, the axis of rotation. Perceptual investigations of my own, concerned with retinal rivalry, have convinced me that the fusion that seems to occur in the visual perception of 3dimensional objects is as much a cognitive as it is a physical-optical effect. The optical image in the brain can be observed to be a mosaic of mutually exclusive pieces of the two distinct images on the two retinas. To observe this, it is only necessary to wear differently colored filters over the two eyes and note the mosaic of coloration!

Multicolor holographic imaging with a white-light source

A simple technique is described by which holograms have been made that reconstruct bright, multicolor images of three-dimensional objects when illuminated with a white-light source. The only sacrifice involved is vertical parallax, which is relatively unimportant.

Determination of the Principal Distance and the Principal Point of a Camera with a 3-dimensional Space Method

In case of short range photogrammetry, the uneliminated vertical parallax often exists in order about a few ten microns and also no good precision results can be obtained. One of the most occurable cause is unsuitable interior orientation elements of the used camera. In photogrammetry, I hope the camera to be used in its best condition. In this paper I show the method for measuring the interior orientation elements analitically. It is based on the central projective relationship between the XYZ coodinate value in object space and the corresponding xy coordinate value in its image space.And also this method is confirmed by using the simulation model mathematically.

AN EXACT PROCEDURE FOR NUMERICAL ORIENTATION OF A PLOTTING INSTRUMENT

AbstractAn exact theory is developed and a method of solution is described for the computation of relative and, if so desired, absolute orientation settings in a plotting instrument. The Ω drum of the plotting instrument is used to remove vertical parallax “in the model” at each of the standard orientation points in turn; this is also done at the control points if the absolute orientation is to be found simultaneously. After removal of parallax at each point, the X, Y, Z settings are recorded. From these data the final instrument settings are computed. The (non‐linear) condition equations are solved using a simplified form of the Newton method generalised to n dimensions. No restrictions are placed on any of the initial settings of the instrument. In view of the continuously increasing ease and speed of access to electronic computers, it seems desirable to ignore all assumptions of small tilts and flat ground which are usually made in order to simplify the arithmetic and to aim instead at an exact solution in one computation.

Reduction of Bandwidth Required for High Resolution Hologram Transmission

A true bandwidth reduction in the transmission requirements of holograms is achieved by recording the diffraction pattern of a scene in the horizontal direction and the actual image in the vertical direction. The image reconstructed from such a unidirectional hologram will lack vertical parallax but will exhibit all other properties of a hologram, providing a virtual reconstruction with depth information. The basic characteristics and limitations of the technique, as well as recording and reconstruction configurations, are described. In addition, experimental results illustrating the main features of the method are given.