Effect of fundamental depth resolution and cardboard effect to perceived depth resolution on multi-view display

Effect of Luminance and Contrast Variation on Stereoacuity Measurements Using Smartphone Technology

Owing to the limitations of printed stereoacuity tests, the effects of luminance and contrast on stereopsis have not yet been sufficiently investigated, despite its important implications in designing stereoacuity measuring instruments, particularly for electronic devices. A stereopsis measurement system was established using two 4 K smartphones and a phoropter to evaluate the effects of luminance and contrast variations on the stereoacuity test. Seventeen young subjects with normal visual acuity and stereopsis were recruited. Two types of test symbols, contour-based and random-dot-based, were used in the experiment. Four series tests were established with different maximum brightness values, including 240 lux, 120 lux, 60 lux, and 30 lux. Each series test contained 19 pages with different contrasts between 95% and 5% and was calculated using the Michelson contrast formula. No significant difference was found for both contour-based and random-dot-based stereograms in any of the contrast groups with different maximum brightness. Similarly, no significant difference was found between contour-based and random-dot-based patterns under different contrasts of above 35%. As the contrast decreased below 30%, the stereopsis was significantly better in the contour-based pattern than in the random-dot-based pattern for some degrees of contrast. The luminance and contrast of the digital display are not critical factors for stereoacuity under normal circumstances. This implies that a standard monitor with a certain 3D technology can be used to measure the stereoacuity threshold without calibrating the luminance and contrast.

Effect of chromatic contrast on stereoacuity measurement with computer-aided three-dimensional technology

Background

Various measurement tools are utilized to detect the stereopsis threshold in the clinic, but seldom of these involves chromatic information. Incorporating colorful elements into computer-aided, three-dimensional (3D) evaluation systems could help the tests appear more vivid and attractive. The aim of this study was to clarify the effect of different chromatic pair stereo targets on the stereoacuity result.

Methods

A total of 17 subjects with visual acuity in each eye of at least 0 logarithmic minimum angle of resolution (logMAR) and a stereoacuity of at least 32 second of arc (arcsec) were recruited. A 3D laptop with liquid crystal shutter glasses was used for evaluating stereoacuity. Thirteen pages were set including seven maximum color contrast pages and six isoluminant color contrast pages.

Results

In maximum color contrast pair, no significant difference was found among all seven experiments [six test groups and one reference group, one-way analysis of variance (ANOVA) test, F=0.995, P=0.493]. There was also no significant difference among the isoluminant color contrast pairs (six test groups, one-way ANOVA test, F=0.873, P=0.644). Paired t-test was used for comparing the data between the same hue series in the maximum color contrast pair vs. the isoluminant color contrast pair, and significant differences were found in all six pairs (P<0.001).

Conclusions

Adding chromatic factors to the stereo test is practical to evaluate stereopsis.

3D imaging scanner

This paper proposes a multi-view three-dimensional display method based on a scanning imaging system with the light-intensity characteristic recorded by an improved flatbed scanner. Within the effective scanning depth of the imaging sensor, two transmission images are each simultaneously acquired by two linear CCD modules with different focal planes. Then the phase gradient information of the target can be obtained by an appropriate retrieval algorithm. Further, the multi-view three-dimensional effect is presented through dynamic angles of view. Theoretical analysis of this method is discussed, and experiments are carried out by building a scanner. The experiment results are presented with an algae specimen and transparent beads. We hope this method can be applied to present the three-dimensional effect of objects of flat translucent multilayer structure with a wide field of view.

Evaluating stereoacuity with 3D shutter glasses technology

Background

To determine the stereoacuity threshold with a 3D laptop equipped with 3D shutter glasses, and to evaluate the effect of different shape and size of test symbols and different type of disparities to stereoacuity.

Methods

Thirty subjects with a visual acuity in each eye of at least 0 logMAR and a stereoacuity of at least 32 arcsec (as assessed in Fly Stereo Acuity Test) were recruited. Three target symbols—tumbling "E", tumbling "C", and "□"—were displayed, each with six different sizes representing a visual acuity ranging from 0.5 to 0 logMAR when tested at 4.1 m, and with both crossed and uncrossed disparities. Two test systems were designed - fixed distance of 4.1 m and one for variable distance. The former has disparities ranging from 10 to 1000 arcsec. Each subject completed 36 trials to investigate the effect of different symbol sizes and shapes, and disparity types on stereoacuity. In the variable distance system, each subject was tested 12 times for the same purposes, both proximally and distally (the point where the 3D effect just appears and where it just disappears respectively), and the mean value was calculated from the mean proximal and distal distances.

Results

No significant difference was found among the groups in the fixed distance test system (Kruskal-Wallis test; Chi-square = 29.844, P = 0.715). Similarly, no significant difference was found in the variable distance system (Kruskal-Wallis test; proximal: Chi-square = 5.687, P = 0.338; distal: Chi-square = 5.898, P = 0.316; mean: Chi-square = 6.152, P = 0.292).

Conclusions

Evaluating stereoacuity using this measurement system was convenient and effective. Changes in target shape and size and disparity types had no significant effect on stereoacuity. It would be helpful to choose optimal targets according to different purposes using computer-assisted 3D measurements.

Electronic supplementary material

The online version of this article (doi:10.1186/s12886-016-0223-3) contains supplementary material, which is available to authorized users.

Depth map sensor based on optical doped lens with multi-walled carbon nanotubes of liquid crystal

In this paper, we present a novel design concept for determining the depth map of three-dimensional (3D) scenes based on an electrically controlled liquid crystal (LC) lens. The advantages of the proposed method are that it does not need any mechanical movements and a large amount of computations to acquire a depth map of a 3D scene in a relatively short amount of time. The tunable-focus LC lens doped with multi-walled carbon nanotubes is to become a key optical component for determining a depth map system. Sequenced two-dimensional images of slightly different perspectives are recorded in a short time, and the depth map of the 3D scene, according to a proposed depth estimation method and a focusing evaluation function, can be acquired in a simple way. This new method to acquire a depth map based on a doped LC lens maximizes the use of the proposed LC lens. The proposed system is novel in its compact, simple, and fast features, so we believe the proposed method can open a new creative dimension in image analysis and imaging systems and can also overcome the limitations of the conventional imaging mode.

Glasses-free randot stereotest

We proposed a glasses-free randot stereotest using a multiview display system. We designed a four-view parallax barrier system and proposed the use of a random-dot multigram as a set of view images for the glasses-free randot stereotest. The glasses-free randot stereotest can be used to verify the effect of glasses in a stereopsis experience. Furthermore, the proposed system is convertible between two-view and four-view structures so that the motion parallax effect could be verified within the system. We discussed the design principles and the method used to generate images in detail and implemented a glasses-free randot stereotest system with a liquid crystal display panel and a customized parallax barrier. We also developed graphical user interfaces and a method for their calibration for practical usage. We performed experiments with five adult subjects with normal vision. The experimental results show that the proposed system provides a stereopsis experience to the subjects and is consistent with the glasses-type randot stereotest and the Frisby–Davis test. The implemented system is free from monocular cues and provides binocular disparity only. The crosstalk of the system is about 6.42% for four-view and 4.17% for two-view, the time required for one measurement is less than 20 s, and the minimum angular disparity that the system can provide is about 23 arc sec.

Instability of the perceived world while watching 3D stereoscopic imagery: A likely source of motion sickness symptoms

Watching 3D content using a stereoscopic display may cause various discomforting symptoms, including eye strain, blurred vision, double vision, and motion sickness. Numerous studies have reported motion-sickness-like symptoms during stereoscopic viewing, but no causal linkage between specific aspects of the presentation and the induced discomfort has been explicitly proposed. Here, we describe several causes, in which stereoscopic capture, display, and viewing differ from natural viewing resulting in static and, importantly, dynamic distortions that conflict with the expected stability and rigidity of the real world. This analysis provides a basis for suggested changes to display systems that may alleviate the symptoms, and suggestions for future studies to determine the relative contribution of the various effects to the unpleasant symptoms.

Real-time integral imaging system for light field microscopy

We propose a real-time integral imaging system for light field microscopy systems. To implement a 3D live in-vivo experimental environment for multiple experimentalists, we generate elemental images for an integral imaging system from the captured light field with a light field microscope in real-time. We apply the f-number matching method to generate an elemental image to reconstruct an undistorted 3D image. Our implemented system produces real and orthoscopic 3D images of micro objects in 16 frames per second. We verify the proposed system via experiments using Caenorhabditis elegans.

Polymeric-lens-embedded 2D/3D switchable display with dramatically reduced crosstalk

A two-dimensional/three-dimensional (2D/3D) display system is presented based on a twisted-nematic cell integrated polymeric microlens array. This device structure has the advantages of fast response time and low operation voltage. The crosstalk of the system is analyzed in detail and two approaches are proposed to reduce the crosstalk: a double lens system and the prism approach. Illuminance distribution analysis proves these two approaches can dramatically reduce crosstalk, thus improving image quality.

Depth-fused display with improved viewing characteristics

We propose a depth-fused display (DFD) with enhanced viewing characteristics by hybridizing the depth-fusing technology with another three-dimensional display method such as multi-view or integral imaging method. With hybridization, the viewing angle and expressible depth range can be extended without changing the size of the volume of the system compared to the conventional DFD method. The proposed method is demonstrated with experimental system.

Real-time capturing and 3D visualization method based on integral imaging

We propose a real-time capturing and 3D visualization method based on integral imaging. We applied real-time conversion algorithm to conventional integral imaging pickup system. Gap control method with depth plane adjustment is also applied to improve image quality. Implemented system provides real-time 3D images with ultra high definition resolution in 20 frames per second, and the observer can change depth planes freely. Simulations and experimental results show the validity of proposed system.

Solution of pseudoscopic problem in integral imaging for real-time processing

Proposed is a very effective conversion method from pseudoscopic (PS) to orthoscopic elemental image with adjustable depth position of a reconstructed three-dimensional (3D) object for integral imaging (InIm) in real-time. The proposed method is based on the interweaving process in multi-view display (MVD) with consideration of the difference between the ray sampling method of MVD and InIm. The simple transformation matrix formalism enables the real-time conversion from pickup image to display image based on InIm without a PS problem.