Exploring crosstalk perception for stereoscopic 3D head‐up displays in a crosstalk simulator

In today's upper class vehicles, head‐up displays (HUDs) are state of the art human–machine interfaces used to increase driving security and comfort. Working with a stereoscopically perceived viewing impression, a novel automotive 3D HUD would allow the simultaneous visualization of multiple contents in various depth planes. However, stereoscopic crosstalk is one of the most important parameters influencing the image quality of stereoscopic systems. We present a setup to simulate crosstalk including a specific software solution. It constitutes a platform to explore the effects of stereoscopic crosstalk in the augmented reality viewing conditions of a 3D HUD. As the setup allows the variation of numerous parameters, it provides a versatile research platform. By means of it, we investigate the variation of the visibility and acceptability thresholds of crosstalk over various parameters. Our results include the finding that they decrease with rising contrast affirming this behavior known for conventional stereoscopic displays for stereoscopic see‐through displays.     

Characterizing image quality of autostereoscopic displays by using the maximum luminance at each viewing position

A metric of the 3D image quality of autostereoscopic displays based on optical measurements is proposed. This metric uses each view's luminance contrast, which is defined as the ratio of maximum luminance at each viewing position to total luminance at that position. Conventional metrics of the autostereoscopic display based on crosstalk, which uses “wanted” and “unwanted” lights. However, in case of the multiple‐views‐type autostereoscopic displays, it is difficult to distinguish exactly which lights are wanted lights and which are unwanted lights. This paper assumes that the wanted light has a maximum luminance at the good stereoscopic viewing position, and the unwanted light also has a maximum luminance at the worst pseudo‐stereoscopic viewing position. By using the maximum luminance that is indexed by view number of the autostereoscopic display, the proposed method enables characterizing stereoscopic viewing conditions without using wanted/unwanted light. A 3D image quality metric called “stereo luminance contrast,” the average of both eyes' contrast, is proposed. The effectiveness of the proposed metric is confirmed by the results of optical measurement analyses of different types of autostereoscopic displays, such as the two‐view, scan‐backlight, multi‐view, and integral.     

Optical characterization of autostereoscopic 3‐D displays

Abstract— Display‐measurement methods different from conventional 2‐D display measurements are needed for verifying the optical characteristics of autostereoscopic (3‐D) displays and for comparing different 3‐D display technologies. Industry is lacking standardized measurement methods, and the reported results can not always be compared. The selected set of characteristics discussed in this paper and partly defining the quality of the 3‐D experience are crosstalk, viewing freedom, and optimum viewing distance. Also, more conventional display characteristics such as luminance are discussed, since the definitions for these characteristics in 3‐D mode usually differ from those used for the 2D displays. We have investigated how these chosen 3‐D display characteristics can be objectively measured from transmissive two‐view and multiview 3‐D displays. The scope of this article is to generally define those basic characteristics as well as the different measurement methods. Most of the 3‐D characteristics can be derived from the luminance and colors versus the viewing angle. Either a conoscopic or a goniometric measurement system can be used, as long as the angular and stray‐light properties are suitable and known. The characteristics and methods are currently discussed in the display‐quality standardization forums.     

Characterization of crosstalk in stereoscopic display devices

Many different types of stereoscopic display devices are used for commercial and research applications. Stereoscopic displays offer the potential to improve performance in detection tasks for medical imaging diagnostic systems. Due to the variety of stereoscopic display technologies, it remains unclear how these compare with each other for detection and estimation tasks. Different stereo devices have different performance trade‐offs due to their display characteristics. Among them, crosstalk is known to affect observer perception of 3D content and might affect detection performance. We measured and report the detailed luminance output and crosstalk characteristics for three different types of stereoscopic display devices. We recorded the effect of other issues on recorded luminance profiles such as viewing angle, use of different eye wear, and screen location. Our results show that the crosstalk signature for viewing 3D content can vary considerably when using different types of 3D glasses for active stereo displays. We also show that significant differences are present in crosstalk signatures when varying the viewing angle from 0 degrees to 20 degrees for a stereo mirror 3D display device. Our detailed characterization can help emulate the effect of crosstalk in conducting computational observer image quality assessment evaluations that minimize costly and time‐consuming human reader studies.     

Perceptual attributes of crosstalk in 3D images

Nowadays, crosstalk is probably one of the most annoying distortions in 3D displays. So far, display designers still have a relative lack of knowledge about the relevant subjective attributes of crosstalk and how they are combined in an overall 3D viewing experience model. The aim of the current experiment is to investigate three perceptually important attributes influencing the overall viewing experience: perceived image distortion, perceived depth, and visual strain. The stimulus material used in this experiment consisted of two natural scenes varying in depth (0, 4, and 12 cm camera base distance) and crosstalk level (0, 5, 10, and 15%). Subjects rated the attributes according to the ITU BT.500–10 in a controlled experiment. Results show that image distortion ratings show a clear increase with increasing crosstalk and increasing camera base distance. Especially higher crosstalk levels are more visible at larger camera base distances. Ratings of visual strain and perceived depth only increase with increasing camera base distance and remain constant with increasing crosstalk (at least until 15% crosstalk).     

3‐D crosstalk and luminance uniformity from angular luminance profiles of multiview autostereoscopic 3‐D displays

Abstract— Autostereoscopic 3‐D display technologies enable a more immersive media experience by adding real depth to the visual content. However, the method used for the creation of a sensation of depth or stereo illusion contains several display design and content‐related issues that need to be carefully considered to maintain sufficient image quality. Conventionally, methods used for 3‐D image‐quality evaluations have been based on subjective testing. Optical measurements, in addition to subjective testing, can be used as an efficient tool for 3‐D display characterization. Objective characterization methods for autostereoscopic displays have been developed. How parameters affecting stereo image quality can be defined and measured, and how their effect on the stereo image quality can be evaluated have been investigated. Developed characterization methods are based on empirically gathered data. In this paper, previously presented methodology for two‐view displays is extended to cover autostereoscopic multiview displays. A distinction between displays where the change in content occurs in clear steps when the user moves in front of the display, and displays where the apparent movement of the objects is more continuous as a function of the head movement is made. Definitions for 3‐D luminance and luminance uniformity, which are equally important, as well as 3‐D crosstalk, which is the dominant factor in the evaluations of the perceived 3‐D image quality, is focused upon.     

A crosstalk model and its application to stereoscopic and autostereoscopic displays

We propose a model to quantify the crosstalk phenomenon for stereoscopic and autostereoscopic displays, separate crosstalk contributed from co‐location image contrast (CIC) and system crosstalk (SCT), introduce gray scale dependency of CIC, modify model for gray scale dependency of SCT in active type 3D displays, and apply the model to derive the 3D luminance and SCT measurement formulas. The model might serve as a basis for the 3D metrology, and the results of this research should be of reference value to hardware makers and inspectors of stereoscopic and autostereoscopic displays.     

Effect of number of views to the viewing experience with autostereoscopic 3‐D displays

Abstract— The observers' 3‐D viewing experience when the way the content is created and shown on an autostereoscopic 3‐D display alternate is evaluated. The observer's depth impression, and the perceived contour accuracy and image naturalness or peskiness of the content shown on a 3‐D display, has been investigated. In addition, the consequences of the way the content is created to the results from the optical characterization for the same display have been studied. The alternation of the content was realized in two different ways. Firstly, the number of views for creating the image was varied. Two, five, and 14 views were used; the main focus being on testing the same display and treating it as an ordinary two‐view and a 14‐view display with inter‐sub‐view crosstalk. Also, the intermediate condition where five views with non‐uniform view‐specific crosstalk were used has been investigated. Secondly, the way the content is created was varied by using images with computer‐generated content and photos. The effect of these parameters on viewing experience as such and especially the effect of 3‐D crosstalk on the viewing experience were studied.     

Characterizing crosstalk in anaglyphic stereoscopic images on LCD monitors and plasma displays

Abstract— In 1853, William Rollman developed the inexpensive and easy to use anaglyph method for displaying stereoscopic images. Although it can be used with nearly any type of full‐color display, the anaglyph method compromises the accuracy of color reproduction, and it often suffers from crosstalk (or ghosting) between the left‐ and right‐eye image channels. Crosstalk degrades the ability of the observer to fuse the stereoscopic image, and hence reduces the quality of the 3‐D image. Crosstalk is present in various levels with most stereoscopic displays; however, it is often particularly evident with anaglyphic 3‐D images. This paper summarizes the results of two projects that characterized the presence of anaglyphic crosstalk due to spectral issues on 13 LCD monitors, 14 plasma displays, and a CRT monitor when used with 25 different pairs of anaglyph 3‐D glasses. A mathematical model was used to predict the amount of crosstalk in anaglyphic 3‐D images when different combinations of displays and glasses are used, and therefore highlight displays, glasses, and combinations thereof which exhibit lower levels of crosstalk when displaying anaglyphic 3‐D images.     

Front glass thickness requirements for high resolution polarized stereoscopic displays: A simulation platform

The tendency of the display market is towards displays with higher resolutions. Therefore, patterned retarder‐based stereoscopic displays require smaller front glass thickness to maintain good vertical viewing angle and limited crosstalk. To properly design these stereoscopic displays and quantify these requirements, we developed a simulation platform to predict radiance, polarization profile, and crosstalk over viewing angles and over wavelengths. Tunable parameters such as the distance between the pixels and the patterned retarder, and the optical properties of the patterned retarder are included. The simulation platform has been validated by comparing outcomes of simulations with measurements. We predict crosstalk accounting for both the human eye field of view and the diameter of the pupil. We found that to obtain a vertical viewing angle of at least ± 30° and crosstalk of at most 0.11 for a display with a pixel pitch beyond 0.27 mm, the display should include black absorbers, and the thickness of the front glass should be at most 0.5 mm. For higher resolution displays (pixel pitch no more than 0.21 mm), a front glass thickness at most 0.15 mm is required to produce a vertical viewing angle beyond ± 14° and a minimum viewing distance of 0.3 m.     

A common approach to characterizing autostereoscopic and polarization‐based 3‐D displays

Abstract— Autostereoscopic and polarization‐based stereoscopic 3‐D displays recreate 3‐D images by providing different images in the two eyes of an observer. This aim is achieved differently for these two families of 3‐D displays. It is shown that viewing‐angle measurements can be applied to characterize both types of displays. Viewing‐angle luminance measurements are made at different locations on the display surface for each view emitted by the display. For autostereoscopic displays, a Fourier‐optics instrument with an ultra‐high‐angular‐resolution VCMaster3D is used. For polarization‐based displays, a standard Fourier‐optics instrument with additional glass filters is used. Then, what will be seen by an observer in front of the display is computed. Monocular and binocular quality criteria (left‐ and right‐eye contrast, 3‐D contrast) was used to quantify the ability to perceive depth for any observer position. Qualified monocular and binocular viewing spaces (QMVS and QBVS) are deduced. Precise 3‐D characteristics are derived such as maximum 3‐D contrast, optical viewing freedom in each direction, color shifts, and standard contrast. A quantitative comparison between displays of all types becomes possible.     

Curved OLED display to effectively enhance natural3D

We studied the stereoscopic effect obtained from a two‐dimensional image without using binocular parallax, which we call “natural3D” (n3D). Unlike a parallax‐based three‐dimensional (3D) display system, n3D causes less tiredness and is free from a decrease of the resolution by half because of image division and viewing position dependence. To make the display with these effects comfortable to use, we conducted statistical tests with sensory evaluation experiments and a quantitative evaluation based on physiological responses. These examinations revealed that the n3D effect can be effectively obtained by using, for example, the characteristics of an organic light‐emitting diode display, such as high contrast and easy bendability. This study discusses optimal display curvatures for displays of different sizes that enhance n3D and reduce tiredness, which are revealed through statistical tests. In addition, we performed an experiment with a frame called an n3D window (n3Dw) that is placed before the display such that a subject views the display through the opening of the frame. We found that the combination of a curve and the n3Dw causes n3D more effectively.     

Depth‐ and viewing‐angle‐enhanced 3‐D/2‐D switchable display system with high contrast ratio using multiple display devices and a lens array

Abstract— An improved 3‐D/2‐D switchable display system with enhanced depth and viewing angle by adding two LCD panels to an integral imaging system has been realized. The proposed system uses the see‐through property of an LCD panel and displays multiple sets of elemental images on the LCD panels to integrate them on multiple locations simultaneously. As a result, the depth of the 3‐D image can be enhanced. For wide viewing angles, the time‐multiplexing method was adopted by displaying mask patterns on the front LCD panel. In addition, another technique to increase the contrast ratio of the proposed system has also been developed. Some experimental results will be provided.     

Invited Paper: Depth reproducibility of multiview depth‐fused 3‐D display

Abstract— A multi‐view depth‐fused 3‐D (DFD) display that provides smooth motion parallax for wide viewing angles is proposed. A conventional DFD display consists of a stack of two transparent emitting screens. It can produce motion parallax for small changes in observation angle, but its viewing zone is rather narrow due to the split images it provides in inclined views. On the other hand, even though multi‐view 3‐D displays have a wide viewing angle, motion parallax in them is discrete, depending on the number of views they show. By applying a stacked structure to multi‐view 3‐D displays, a wide‐viewing‐angle 3‐D display with smooth motion parallax was fabricated. Experimental results confirmed the viewing‐zone connection of DFD displays while the calculated results show the feasibility of stacked multi‐view displays.     

Key design issues for autostereoscopic 2‐D/3‐D displays

Abstract— Flat‐panel 2‐D/3‐D autostereoscopic displays are now being commercialized in a variety of applications, each with its own particular requirements. The autostereoscopic display designer has two key considerations to address in order to meet customer needs — the optical output of the display (defined by the output window structure) and the choice of optical components. Window structure determines 3‐D image resolution, achievable lateral and longitudinal viewing freedom, crosstalk, and 3‐D fringe contrast. Optical‐component selection determines the quality of the imaging of such windows, viewing distances, device ruggedness, thickness, and brightness. Trade‐offs in window design are described, and a comparison of the leading optical component technologies is given. Selection of Polarisation Activated Microlenses? architectures for LCD and OLED applications are described. The technology delivers significant advantages particularly for minimising nominal viewing distances in high pixel density panels and optimizing device ruggedness while maintaining display brightness.     

Relationship between phoria and visual fatigue in autostereoscopic 3D displays

Many people complain about visual fatigue arising from viewing three‐dimensional (3D) displays. This paper investigates relationship between visual fatigue and viewers' phoria for viewing autostereoscopic 3D displays. Visual fatigue is evaluated through subjective symptoms with a questionnaire and optometric indicators comprising fusion range as well as accommodation convergence/accommodation (AC/A) ratio to measure the variation in visual functions. A screening test is adopted to divide the subjects into two groups based on whether they suffer from phoria. Then a 2 × 2 × 2 mixed design experiment is conducted with display type, viewing stage, and visual state as factors to examine visual fatigue during viewing session. The results show that phoria subjects obtain more severe visual fatigue than normal on subjective evaluation. The normal subjects reveal a more marked difference with phoria in fusion range and AC/A ratio after viewing 3D video clip. Fusion range can significantly distinguish between the two‐dimensional (2D) and 3D condition as well as between the pre‐ and post‐viewing stages. The sensitivity and specificity of fusion range is higher than AC/A ratio with respect to viewing of 3D contents, so it is more appropriate as an optometric indicator of visual fatigue for autostereoscopic 3D displays.     

Three‐dimensional lenticular display synthetic image rendering based on light field acquisition

Crosstalk is a critical defect affecting image quality in multiview lenticular 3D displays. Existing optimization methods require tedious computations and device‐specific optical measurements, and results are often suboptimal. We propose a new method, on the basis of light field acquisition and optimization, for crosstalk reduction in super multiview displays. Theory and algorithms were developed, and experimental validation results showed superior performance.     

Switching directional BLUs for full‐resolution auto‐stereoscopic 3D/2D and 2D/3D LCDs

Directional backlight unit (BLU) design concept was applied to realize full‐resolution field alternate auto‐stereoscopic liquid crystal displays (LCDs) with built‐in 3D/2D and 2D/3D. The application‐oriented BLU design requires priority in realizing 2D mode or 3D mode. The switching characteristic of BLU with two confronting illuminating sets was applied to build 2D mode into 3D display and 3D mode into 2D display. An LCD with 2D mode as primary function requires higher double‐sided luminance uniformity than 3D mode. On the other hand, an LCD with 3D mode requires higher single‐sided luminance uniformity than 2D mode. For increasing the double‐sided luminance uniformity for 2D mode as a primary function of the display, the former BLU design was realized by using uniform prismatic structure, that is, using uniform bilateral prismatic structure with a cross section of isosceles triangle on the back surface of the light‐guide plate. For increasing single‐sided luminance uniformity for 3D mode as a primary function of the display, the latter was realized by using graded angle design, that is, unilateral prisms with a cross section of a scalene triangle on the back surface of the light‐guide plate. The LCDs of small‐sized‐handheld game devices and still cameras were fabricated using the 3D/2D and 2D/3D displays.     

DP3 signal as a neuro-indictor for attentional processing of stereoscopic contents in varied depths within the ‘comfort zone’

When viewing stereoscopic 3D (S3D) displays, excessive binocular disparity is one of the major sources for the induced visual fatigue. Limiting the disparity within a certain range termed ‘comfort zone’ is a useful approach to alleviate the negative impact of viewing the S3D displays. Using the event-related potential (ERP) approach, we have previously showed that the differential P3 (DP3) signal evoked in an oddball task could be a useful neural indicator of the involvement of high-level cognitive functions in viewing S3D contents within the comfort zone compared to viewing 2D contents, despite of the similar subjective comfort of viewing experience for the two display conditions. It remains unclear whether the DP3 signal is sensitive enough for examination of the high-level processing when viewing S3D contents in different disparities within the comfort zone. Here, the DP3 signals were recorded while subjects performed an oddball task presented in S3D modality for three disparities (0.15, 0.45 and 0.76 arcdeg) within the comfort zone. Whereas the oddball task was of similar comfort by subjective measurement for different disparities, the DP3 signal showed monotonic delay in latency for increasing disparity, suggesting the capability of the DP3 signal for establishing a ‘cognitive comfort zone’ in terms of the high-level cognitive functions.