MEMS-based tactile displays

This paper discusses state-of-the-art tactile displays fabricated by a micro-electronic-mechanical-system (MEMS). A tactile display conveys tactile sensations to users by using actuators. Traditional tactile displays consist of large size actuators, such as a motor or an ultrasound vibrator, to convey tactile feedback by vibration. In addition, the tactile sensation of traditional displays has poor resolution. Microelectromechanical system (MEMS) technology, which is a miniature fabrication process, enables etching, sputtering and assembling of miniature structures. Recently, the technology was applied to tactile displays. For example, shape memory alloy (SMA) actuators are widely used in tactile displays to convey roughness or vibration. The actuators are fabricated by a sputtering process and then thinned. The displays convey various tactile sensations, including feedback and tactile sensations of objects such as paper or wood. This paper is a review of tactile displays fabricated by MEMS technology. We also describe the fabrication processes and stimulation methods to present the potential and applications of the displays.     

Design of large‐area OLED displays utilizing seamless tiled components

Abstract— In recent years, the majority of R&D for large‐area displays has been to serve the production of large monolithic substrate technology such as plasma‐display panels (PDPs) and TFT‐LCD. While the pursuit of large displays for domestic and light‐industrial use benefits from the production of these high‐quality high‐pixel‐count technologies, there is still a need to produce displays in formats other than 4:3 or 16:9 and on a larger scale than currently available in single‐substrate displays. The options that exist for producing tiled displays from emerging technologies is examined and a practical technique for creating large‐area (1.8 × 1.2 m and larger) monochrome or color displays from tiling smaller units is discussed. This presents a cost‐effective approach for arranging small tiles to create a much larger screen and offers a simple way to address the market gap between large monolithic displays and small conventional LED video‐wall displays, in the size range of 1–10‐mm pixels for advertising and industrial use. By examining the requirements for pixel size and pitch against the range of viewing distances commonly associated with the target markets for these displays, it will be shown that complex manufacturing is not always required.     

Suppression of color breakup in color‐sequential multi‐primary projection displays

Abstract— Field‐sequential projection displays exhibit a phenomenon of color breakup (Rainbow effect). This is considered to be a disturbing artifact with negative marketing impact. The results of a psychophysical experiment comparing the visibility of the phenomenon in RGB and multi‐primary displays is described. Surprisingly, it is found that color breakup in color‐sequential projection displays with five primaries is equally (for 75 Hz) or less (for 105 Hz) visible than in similar displays with three primaries (at 180 Hz), despite the lower refresh rates.     

Under the weather: an evaluation of different modes of presenting meteorological information for pilots

Understanding current and forecast weather conditions for a planned route of flight is vital for general aviation (GA) pilots. Weather information can be obtained from multiple sources and in multiple formats, ranging from abbreviated code provided by aviation weather forecasters to animated graphical displays available on TV and the Internet. The present study investigated the effectiveness of graphical displays of meteorological information. A commercially available graphical display was ergonomically redesigned and the original and redesigned displays were compared with an ordinary text statement. Recall of information was significantly affected by display type. Comparisons showed the ergonomically redesigned display to be superior to the ordinary text statement. Performance was affected by participants’ general level of familiarity with evaluating data displays as measured by their area of study (sciences or humanities). The generalizability of the results to the pilot population is discussed.     

Bias in Experimental Comparisons between Equipments due to the Order of Testing

Trials comparing equipments should use separate groups of people for each equipment, If the same people work with all the equipments in balanced orders, the results of the trial may be biased by hidden transfer effects. This point is illustrated by two sets of experiments.

One set of experiments compared true motion or pursuit displays with relative motion or compensatory displays. True motion displays are always preferable to relative motion displays. Yet three experiments found a relative motion display reliably better than a true motion display under certain conditions. Those unfortunate results are probably due to the people in the experiments confusing the various optimal phase relationships between control movements and display movements.

The second sot of experiments compared various orders of control using a true motion display. A position control system is more compatible with a true motion display than is any higher order of control system. Yet one experiment found rate and rate-aided control systems reliably better than a position control system with the lowest frequency track. This result also is probably due to confusion between the various optimal phase relationships.     

Super multi‐view 3D displays reduce conflict between accommodative and vergence responses

A conflict between accommodation and vergence is one possible cause of visual fatigue and discomfort while viewing conventional three‐dimensional displays. Previous studies have proposed the super multi‐view (SMV) display technique to solve the vergence–accommodation conflict, in which two or more parallax images enter the pupil of the eye with highly directional rays. We simultaneously measured accommodative, vergence, and pupillary responses to SMV three‐dimensional displays to examine whether they can reduce the conflict. For comparison, responses to two‐view stereo images and real objects were also measured. The results show that the range of the accommodative response was increased by the SMV images compared with the two‐view images. The slope of the accommodation–vergence response function for the SMV images was similar to that for the real objects rather than the two‐view images. We also found that enhancement of the accommodative range by the SMV images is noticeable with binocular viewing, indicating that vergence‐induced accommodation plays an important role in viewing SMV displays. These results suggest that SMV displays induced a more natural accommodative response than did conventional, two‐view stereo displays. As a result, SMV displays reduced the vergence–accommodation conflict.     

Ripple phenomenon of displays with nematic liquid crystal

Liquid crystal displays will show ripple if the display surface or display bracket is subjected to tactile forces. In this paper, the ripple of liquid crystal displays is investigated by dealing with elastic wave propagation in a liquid crystal layer. The model proposed for a visco‐elastic medium like liquid crystals (LCs) is generalized by combining the properties of a crystalline solid and an anisotropic fluid. The governing equation is derived by using visco‐elastic and wave equations. In the experiments, a linear motor is used to touch the display panel for producing ripple. Displays of three different amounts of LCs are compared. Experimental results also show that each display panel has its own wave propagation velocity that is not changed by different motor touch speeds. In addition, both theoretical analysis and experimental results depict that displays with a larger amount of LCs lead to slower ripple speed.     

Efficient multi-view ray tracing using edge detection and shader reuse

Stereoscopic rendering and 3D stereo displays are quickly becoming mainstream. The natural extension is autostereoscopic multi-view displays which, by the use of parallax barriers or lenticular lenses, can accommodate many simultaneous viewers without the need for active or passive glasses. As these displays, for the foreseeable future, will support only a rather limited number of views, there is a need for high-quality interperspective antialiasing. We present a specialized algorithm for efficient multi-view image generation from a camera line using ray tracing, which builds on previous methods for multi-dimensional adaptive sampling and reconstruction of light fields. We introduce multi-view silhouette edges to detect sharp geometrical discontinuities in the radiance function. These are used to significantly improve the quality of the reconstruction. In addition, we exploit shader coherence by computing analytical visibility between shading points and the camera line, and by sharing shading computations over the camera line.     

Visualization task performance with 2D, 3D, and combination displays

We describe a series of experiments that compare 2D displays, 3D displays, and combined 2D/3D displays (orientation icon, ExoVis, and clip planes) for relative position estimation, orientation, and volume of interest tasks. Our results indicate that 3D displays can be very effective for approximate navigation and relative positioning when appropriate cues, such as shadows, are present. However, 3D displays are not effective for precise navigation and positioning except possibly in specific circumstances, for instance, when good viewing angles or measurement tools are available. For precise tasks in other situations, orientation icon and ExoVis displays were better than strict 2D or 3D displays (displays consisting exclusively of 2D or 3D views). The combined displays had as good or better performance, inspired higher confidence, and allowed natural, integrated navigation. Clip plane displays were not effective for 3D orientation because users could not easily view more than one 2D slice at a time and had to frequently change the visibility of individual slices. Major factors contributing to display preference and usability were task characteristics, orientation cues, occlusion, and spatial proximity of views that were used together.     

Information structure and the relative efficacy of tables and graphs

Users and system designers often prefer to display information with graphs rather than with tables. However, empirical studies that compared task performance with the two display types frequently revealed either an advantage of tables over graphs or no differences between the displays. This apparent contradiction may result from previous studies in which the importance of the structure that usually exists in displayed information is overlooked. We predict that graphic displays will have an advantage over tables when the displayed information has structure and when this structure is relevant for the task. These conditions generally exist in the actual use of information displays, but have seldom been assessed in experiments. In the present study participants in an experiment performed an information extraction task and a prediction task with unstructured or structured data and with different levels of prior information about the structure. The results showed that the information structure and prior knowledge about the existence of structure affected the advantage of graphic displays over tables when task performance depended on the use of structure. Existing approaches to the study of displays were analyzed in view of these findings. Actual or potential applications of this research include the development of better displays for process control and decision support and better operator training programs.     

A comparative study of mobile map displays in a geographic orientation task

In an ergonomic experiment, different mobile map displays were compared in a simulated geographical orientation task. Subjects had to cross mazes while the corresponding maps were presented on a hand-held display, two helmet-mounted displays (a retinal scanning and a liquid crystal display) or on paper. The simulated mazes were projected on a backlit screen and the subjects could cross them using a joystick. The displays were compared with regard to subjects' speed when crossing the mazes, experienced task difficulty, visual fatigue and simulator sickness. The results show that speed was lowest with the paper map and experienced task difficulty was highest, whereas no significant differences were found between the electronic displays. Visual fatigue and simulator sickness were low and no significant differences were observed between all displays. The conclusion is drawn that all electronic map displays can be used for short time periods (15 - 30 minutes); however, long term effects have to be analysed in future experimental studies.     

Light-field head-mounted displays reduce the visual effort: A user study

Head-mounted displays (HMDs) allow the visualization of virtual content and the change of view perspectives in a virtual reality (VR). Besides entertainment purposes, such displays also find application in augmented reality, VR training, or tele-robotic systems. The quality of visual feedback plays a key role for the interaction performance in such setups. In the last years, high-end computers and displays led to the reduction of simulator sickness regarding nausea symptoms, while new visualization technologies are required to further reduce oculomotor and disorientation symptoms. The so-called vergence–accommodation conflict (VAC) in standard stereoscopic displays prevents intense use of 3D displays, so far. The VAC describes the visual mismatch between the projected stereoscopic 3D image and the optical distance to the HMD screen. This conflict can be solved by using displays with correct focal distance. The light-field HMD of this study provides a close-to-continuous depth and high image resolution enabling a highly natural visualization. This paper presents the first user-study on the visual comfort of light-field displays with a close-to-market HMD based on complex interaction tasks. The results provide first evidence that the light-field technology brings clear benefits to the user in terms of physical use comfort, workload, and depth matching performance.     

Displaying a boundary in graphic and symbolic “wait” displays: Duration estimates and users’ preferences

Two experiments assessed the effect of displaying a boundary on duration estimates and preference ratings for dynamic displays that were shown while users waited for the system's response. Displays were either symbolic (changing numbers) or graphic (increasing rectangles) and could contain a boundary that indicated when the interval was expected to be over. Duration estimates were similar for symbolic and graphic displays and for displays with and without a boundary. However, when the displays were encountered successively, participants assessed the graphic displays as having shorter durations than the symbolic displays. Faster rates of change in both types of displays led to increased duration estimates. Although displaying a boundary did not affect duration estimates, participants preferred displays in which a boundary was shown and preferred the graphic displays over the symbolic displays. Hence, bounded graphic displays are recommended as “wait” displays for computerized applications.     

Comparison of oxidative stress response of in vitro retinal cells exposed to blue light from emissive versus reflective displays

During COVID-19, there was increased use of handheld displays in educational settings. There is growing concern that eye health may be affected by prolonged exposure to the light-emitting diodes used as frontlights or backlights in handheld displays. The potential impact of light exposure from tablet-sized devices with different display technologies and various spectral outputs was assessed in an in vitro model using human retinal epithelial (ARPE-19) cells. Cellular response was quantified by measuring reactive oxidative species (ROS) and by analyzing mitochondrial morphology. Control experiments established a baseline ROS response to hazardous blue light exposure and also that red light resulted in no detectable ROS response. Under identical conditions, ROS response increased with time for all devices. However, different device spectra caused ROS to accumulate at different rates. When operating the devices in the same mode (day or night), cells accumulated ROS two to three times more slowly on exposure to frontlit electronic paper displays compared to backlit liquid crystal displays. With increasing ROS accumulation, mitochondrial morphology shifted from elongate interconnected features typically observed under normal conditions to rounded disconnected features associated with oxidative stress response.     

A comparative study of mobile map displays in a geographic orientation task

In an ergonomic experiment, different mobile map displays were compared in a simulated geographical orientation task. Subjects had to cross mazes while the corresponding maps were presented on a hand-held display, two helmet-mounted displays (a retinal scanning and a liquid crystal display) or on paper. The simulated mazes were projected on a backlit screen and the subjects could cross them using a joystick. The displays were compared with regard to subjects' speed when crossing the mazes, experienced task difficulty, visual fatigue and simulator sickness. The results show that speed was lowest with the paper map and experienced task difficulty was highest, whereas no significant differences were found between the electronic displays. Visual fatigue and simulator sickness were low and no significant differences were observed between all displays. The conclusion is drawn that all electronic map displays can be used for short time periods (15 – 30 minutes); however, long term effects have to be analysed in future experimental studies.     

Depth of focus and visual recognition of imagery presented on simultaneously viewed displays: implications for head-mounted displays

OBJECTIVE: We sought to determine the optimal focal distance for a semitransparent monocular head-mounted display (HMD) integrated with a flight simulator display and to investigate whether observers experienced visual discomfort or impaired target recognition when using an HMD set at the optimal distance. BACKGROUND: When an observer wears a monocular HMD and views a simulator display, focal distances of both displays must be within the observers' depth of focus to prevent blurred imagery. Because focal distance can vary by as much as 0.5 m in U.S. Air Force multifaceted simulator displays, we determined whether a monocular HMD could be integrated with a simulator display without blurred imagery or discomfort. METHOD: Depth of focus and visual recognition were measured with a staircase procedure, and visual discomfort was measured with a questionnaire. RESULTS: Depth of focus was 0.64 diopters in one condition tested, but it was affected by luminance level and display resolution. It was recommended that HMD focal distance equal the optical midpoint of the range of viewing distances encountered in the simulator. Moreover, wearing an HMD produced a decline in recognition performance for targets presented on the simulator display despite both displays being within observers' depth of focus and producing no visual discomfort. CONCLUSION: Monocular HMDs can be integrated with multifaceted simulator displays without blurred imagery or visual discomfort, provided that the correct focal distance is adopted. APPLICATION: For situations involving simultaneously viewed visual displays.     

General design method for three-dimensional displays with horizontally asymmetric pixel structures

Various 3D displays have been proposed to show realistic and vivid 3D images. Moreover, 3D displays have been applied in various fields including medicine, entertainment, and advertising. Depending on the application, 3D displays have different pixel structures and sizes. In this paper, we present a 3D-display design method that can be applied regardless of the pixel structure and display sizes. The area of the designable 3D display is suggested by the improved 3D image quality. The manufactured displays are used to verify the proposed method. Furthermore, a light field simulation is performed to confirm the area that was not proven by the manufactured displays. With the proposed 3D image-quality model and 3D image simulation by the light field representation, a general design of 3D displays with various pixel structures can be developed.     

Bit‐depth extension: Overcoming LCD‐driver limitations by using models of the equivalent input noise of the visual system

Abstract— Continuous tone, or “contone,” imagery usually has 24 bits/pixel as a minimum, with 8 bits each for the three primaries in typical displays. However, lower‐cost displays constrain this number because of various system limitations. Conversely, higher‐quality displays seek to achieve 9–10 bits/pixel/color, though there may be system bottlenecks limited to 8. The two main artifacts from reduced bit‐depth are contouring and loss of amplitude detail; these can be prevented by dithering the image prior to these bit‐depth losses. Our technique builds on Roberts's noise‐modulation idea and the subsequently influenced work in halftoning for hardcopy and dithering for displays. However, most halftoning/dithering work was primarily directed to displays at the lower end of bits/pixel (e.g., 1 bit as in halftoning) and higher ppi. We approach the problem from the higher end of bits/pixel/color, for example, 6–8, and lower spatial resolution (<100 ppi), which changes the game substantially from halftoning experience. Instead of spatial dither, it is better to use an amplitude dither. In addition, dynamic displays allow for the use of a temporal dithering component. This paper will report on techniques and observations made in achieving contone quality on ～100‐or‐less‐ppi LCDs starting from 4‐ to 8‐bit driver limits, and resulting with no visible dither patterns, noise, contours, or loss of amplitude detail at viewing distances as close as the near focus limit (～120 mm).     

Flexible OLED display development: Strategy and status

Abstract— In this paper, the current status of flexible OLED (FOLED®) display development will be reviewed, including previous results for passive‐matrix displays on plastic and current progress on active‐matrix displays on steel foil. The displays incorporate high‐efficiency small‐molecule phosphorescence OLED (PHOLE?) technology. The ultimate goal is to develop high‐information‐content high‐performance long‐lived, and large‐area FOLED displays that can be pulled or rolled out from a smaller pen‐like housing. The strategy for achieving this goal will be presented.     

Optimization suggestions for instrument‐cluster information using displays

Abstract— Suggestions are proposed to improve the way information is presented with heads‐down displays (HDDs) to optimize the information and potentially reduce the duration and frequency of scans necessary by the driver to read the information. Using color as a secondary channel of information on vehicle meters could reduce scan frequency by increasing awareness in driver' s peripheral vision. Only showing relevant portion of scales can reduce the overall necessary area for display information and possibly reduce the number of fixations necessary to read the information from that area. Larger displays can be optimized with same considerations as other displays, butthe size creates an easier opportunity to be filled with information in a way that ends up distracting the driver. Elaborate or complex graphics that emphasize the full abilities of larger displays are probably best limited to non‐driving conditions. Color displays also have the potential benefit of reconfigurability, which could have a significant impact on how information is presented. Reconfiguration concepts suggested include only showing information of interest, font‐size adjustment, and using GPS information to augment speed information based on traffic, time of day, and weather conditions.