Motion artifacts on 240‐Hz OLED stereoscopic 3D displays

Temporal multiplexing is a popular approach for presenting different images to the two eyes in stereoscopic 3D (S3D) displays. We examined the visibility of flicker and motion artifacts—judder, motion blur, and edge banding—on a 240‐Hz temporally multiplexed S3D OLED display. Traditionally, a frame rate of 120 Hz (60 Hz per eye) is used to avoid visible flicker, but there is evidence that higher frame rates provide visible benefits. In a series of psychophysical experiments, we measured the visibility of artifacts on the OLED display using temporal multiplexing and those of a 60‐Hz S3D LCD using spatial multiplexing. We determined the relative contributions of the frame rate of the content, update rate of the display, duty cycle, and number of flashes. We found that short duty cycles and low flash numbers reduce the visibility of motion artifacts, while long duty cycles and high flash numbers reduce flicker visibility.     

Effect of the field of view on perceiving world-referenced image motion during concurrent head movements

We have previously shown that concurrent head movements impair head-referenced image motion perception when compensatory eye movements are suppressed (Li, Adelstein, & Ellis, 2009) [16]. In this paper, we examined the effect of the field of view on perceiving world-referenced image motion during concurrent head movements. Participants rated the motion magnitude of a horizontally oscillating checkerboard image presented on a large screen while making yaw or pitch head movements, or holding their heads still. As the image motion was world-referenced, head motion elicited compensatory eye movements from the vestibular-ocular reflex to maintain the gaze on the display. The checkerboard image had either a large (73°H × 73°V) or a small (25°H × 25°V) field of view (FOV). We found that perceptual sensitivity to world-referenced image motion was reduced by 20% during yaw and pitch head movements compared to the veridical levels when the head was still, and this reduction did not depend on the display FOV size. Reducing the display FOV from 73°H × 73°V to 25°H × 25°V caused an overall underestimation of image motion by 7% across the head movement and head still conditions. We conclude that observers have reduced perceptual sensitivity to world-referenced image motion during concurrent head movements independent of the FOV size. The findings are applicable in the design of virtual environment countermeasures to mitigate perception of spurious motion arising from head tracking system latency.     

Motion‐blur characterization with simulation method for mobile LCDs

Abstract— A simulation method based on measured liquid‐crystal responses and human‐vision properties was proposed to characterize the motion blur of LCDs. A perceptual experiment was implemented to validate the simulation model within different viewing conditions by changing the visual angle. The results indicate that the smaller visual angle of the mobile display has no statistic significant effect on smooth‐pursuit eye tracking when perceiving a moving block on a screen. The calculation process of quantitative metric was presented based on the measured light behavior and the simulation model. In the end, the different motion‐blur reduction approaches were evaluated for mobile LCDs.     

Effect of vibration on eye,head and helmet movements while wearing a helmet‐mounted display

Previous research has demonstrated a loss of helmet‐mounted display (HMD) legibility for users exposed to whole body vibration. A pair of human factors studies was conducted to evaluate the effect of whole body vibration on eye, head, and helmet movements for seated users of a HMD while conducting simple fixation and smooth pursuit tracking tasks. These experiments confirmed that vertical eye motion can be demonstrated, that is consistent with the human visual systems' response to the vestibular–ocular reflex (VOR). Helmet slippage was also shown to occur, which could exacerbate loss of display legibility. The largest amplitudes in eye movements were observed during exposure to sinusoidal vibration in the 4–6 Hz range, which is consistent with the frequencies that past research has associated with whole‐body resonance and the largest decrease in display legibility. Further, the measured eye movements appeared to be correlated with both the angular acceleration of the user's head and the angular slippage of the user's helmet. This research demonstrates that the loss of legibility while wearing HMDs likely results from a combination of VOR‐triggered eye movements and movement of the display. Future compensation algorithms should consider adjusting the display in response to both VOR‐triggered eye and HMD motion.     

Analysis,simulation, and evaluation of scrolling illumination as a method for reducing motion blur in LCOS projectors

Abstract— A high‐fidelity simulation of motion blurring in an LCOS projector was developed by using the measured temporal response of the projector. The simulation was validated for continuous and scanning illumination by comparison with results of motion‐blur measurements by using a pursuit camera. The simulation was then used to analyze and optimize duty cycle and phase parameters for scrolling illumination in the general case.     

Characterizing displays by their temporal aperture: A theoretical framework

Abstract— The spatio‐temporal aperture and sample rate of a video display determines both the static and dynamic resolution of the video signal that is rendered. The dynamic display characteristics like the visibility of large‐area flicker, motion judder, and motion blur can be derived from the frame rate and the temporal extent of the pixel aperture (i.e., the temporal aperture). For example, liquid‐crystal displays (LCDs) have an aperture that is relatively small in the spatial dimension and wide in the temporal domain. Consequently, moving objects displayed on an LCD suffer from motion blur. Especially in TV applications, the temporal dimension has a large impact on the overall picture quality. The temporal aperture, together with the frame rate, is shown to predict the amount of perceived large‐area flicker, motion judder, and motion blur and also the performance of motion‐blur reduction algorithms for LCDs. From this analysis it is further determined how to obtain the optimal temporal aperture of a television display, for which not only properties of the human visual system (HVS), but also the properties of the video signal have to be taken into account.     

Comparisons of motion‐blur assessment strategies for newly emergent LCD and backlight driving technologies

Abstract— Compared to the conventional cathode‐ray‐tube TV, the conventional liquid‐crystal TV has the shortcoming of motion blur. Motion blur can be characterized by the motion‐picture response‐time metric (MPRT). The MPRT of a display can be measured directly using a commercial MPRT instrument, but it is expensive in comparison with a photodiode that is used in temporal‐response (temporal luminance transition) measurements. An alternative approach is to determine the motion blur indirectly via the temporal point‐spread function (PSF), which does not need an accurate tracking mechanism as required for the direct “spatial” measurement techniques. In this paper, the measured motion blur is compared by using both the spatial‐tracking‐camera approach and the temporal‐response approach at various backlight flashing widths. In comparison to other motion‐blur studies, this work has two unique advantages: (1) both spatial and temporal information was measured simultaneously and (2) several temporal apertures of the display were used to represent different temporal PSFs. This study shows that the temporal method is an attractive alternative for the MPRT instrument to characterize the LCD's temporal performance.     

Analysis of response‐time compensation for black‐frame insertion

Abstract— An impulsive driving technique has been widely adopted for the elimination of motion blur in LCDs. Although the problem of slow temporal response time is very well known for LCDs, the inherent motion blur of moving objects in hold‐type displays has a more‐serious impact on display performance. It is well known that even very fast LCDs with zero response time still suffer from the motion‐blur artifact due to hold‐type driving effects. However, a fast temporal response is also critical in order to maximize the blur‐reduction effect even in the case of impulsive driving. In this paper, the special behavior of LC molecules in an impulsive driving environment has been analyzed especially for the case of black‐frame insertion, and we propose an effective means to implement optimized response‐time compensation (RTC) for the black‐frame insertion technique.     

Motion‐blur characterization on liquid‐crystal displays

Abstract— In this paper, several methods to characterize motion blur on liquid‐crystal displays are reviewed. Based on the assumptions of smooth‐pursuit eye tracking and one‐frame temporal luminance integration, a simple algorithm has been proposed to calculate the normalized blurred edge width (N‐BEW) and motion‐picture response time (MPRT) with a one‐frame‐time moving‐window function to LC temporal step response curves. A custom measurement system with a fast‐eye‐sensitivity‐compensated photodiode has been developed to characterize motion blur based on LC response curves (LCRCs). MPRT values obtained by using the algorithm mentioned above and those from the smooth‐pursuit‐camera methods agree. Perception experiments were conducted to validate the correspondence between the simulated results and actual perceived images by the human eyes. In addition, the insufficiency of MPRT to evaluate motion blur on impulse‐type light‐generation LCDs, by analyzing the measurement results of a scanning backlight LCD, is discussed.     

The effect of FLCoS‐display hold time on the perceived blur of moving imagery

Abstract— The on‐ and off‐times of LCDs have decreased significantly over the past few years. However, long hold times, while increasing light output, have limited the temporal resolution of these devices. We have varied hold time and used a perceptual technique to assess the resulting change in blur of a moving test target presented on an FLCoS display. The technique requires observers to adjust the gap between two vertical lines that move across the display at various speeds. It was found that for a 13.4‐msec hold time, the threshold gap width, and thus by implication the perceived blur, increased significantly from about 3 to 22 pixels as line speed was increased. For hold times of 8, 6, 4, and 2 msec, threshold gap width remained approximately constant at between about 2 and 5 pixels as line speed was increased. The results of the perceptual test used here suggest that reducing FLCoS hold time to 8 msec significantly improves the quality of moving imagery. Further, decreasing the hold time to 2 msec results in perceptual blur that extends over as little as 6 arc‐minutes.     

Evaluation of motion performance on scanning‐backlight LCDs

Abstract— The scanning‐backlight technique to improve the motion performance of LCDs is introduced. This technique, however, has some drawbacks such as double edges and color aberration, which may become visible in moving patterns. A method combining accurate measurements of temporal luminance transitions with the simulation of human‐eye tracking and spatiotemporal integration is used to model the motion‐induced profile of an edge moving on a scanning‐backlight LCD‐TV panel that exhibits the two drawbacks mentioned above. The model results are validated with a perception experiment including different refresh rates, and a high correspondence is found between the simulated apparent edge and the one that is perceived during actual motion. Apart from the motion‐induced edge blur, the perception of a moving line or square‐wave grating can also be predicted by the same method starting from the temporal impulse and frame‐sequential response curves, respectively. Motion‐induced image degradation is evaluated for both a scanning‐ and continuous‐backlight mode based on three different characteristics: edge blur, line spreading, and modulation depth of square‐wave grating. The results indicate that the scanning‐backlight mode results in better motion performance.     

Motion‐blur‐free LCD for high‐resolution virtual reality displays

A new liquid crystal display device with fast response time, high transmittance, and low voltage for virtual reality is reported. When driven at 90 Hz with 17% duty ratio, the motion picture response time is 1.5 ms, which is comparable with cathode‐ray tube, leading to indistinguishable motion blur. Moreover, this device enables high‐resolution density because only one thin‐film transistor per pixel is needed and it has a built‐in storage capacitor.     

Coded exposure HDR light‐field video recording

Capturing exposure sequences to compute high dynamic range (HDR) images causes motion blur in cases of camera movement. This also applies to light‐field cameras: frames rendered from multiple blurred HDR light‐field perspectives are also blurred. While the recording times of exposure sequences cannot be reduced for a single‐sensor camera, we demonstrate how this can be achieved for a camera array. Thus, we decrease capturing time and reduce motion blur for HDR light‐field video recording. Applying a spatio‐temporal exposure pattern while capturing frames with a camera array reduces the overall recording time and enables the estimation of camera movement within one light‐field video frame. By estimating depth maps and local point spread functions (PSFs) from multiple perspectives with the same exposure, regional motion deblurring can be supported. Missing exposures at various perspectives are then interpolated.     

Fixational eye movements, natural image statistics, and fine spatial vision

Perception and motor control are often regarded as two separate branches of neuroscience. Like most species, however, humans are not passively exposed to the incoming flow of sensory data, but actively seek useful information. By shaping input signals in ways that simplify perceptual tasks, behavior might play an important role in establishing efficient sensory representations in the brain. Under natural viewing conditions, the main source of motion of the stimulus on the retina is not the scene but our own behavior. The retinal image is never still, even during visual fixation, when small eye movements combine with movements of the head and body to continually perturb the location of gaze. This article examines the impact of the fixational motion of the retinal image on the statistics of visual input and the neural encoding of visual information. Building upon recent theoretical and experimental results, it is argued that an unstable fixation constitutes an efficient strategy for acquiring information from natural scenes. According to this theory, the fluctuations of luminance caused by the incessant motion of the eye equalize the power present at different spatial frequencies in the spatiotemporal stimulus on the retina. This phenomenon yields compact neural representations, emphasizes fine spatial detail, and might enable a temporal multiplexing of visual information from the retina to the cortex. This theory posits motor contributions to early visual representations and suggests that perception and behavior are more intimately tied than commonly thought.     

Conjugate‐optical retroreflector display system: Optical principles and perceptual issues

Abstract— Conjugate‐optical retroreflector (COR) display systems have the potential for providing inexpensive high‐resolution imagery in a head‐mounted display (HMD) configuration. There are several perceptual issues, however, that need to be addressed before a COR display system can be used effectively. One issue is the choice of projected‐image location relative to the retroreflective screen, which is determined by the convergence angle between the binocular channels of the COR display. Another issue involves visual half‐occlusions, which can occur when a portion of a stereoscopic image is visible to only one eye, as may occur in any HMD. If half occlusions are simulated in a COR display in a way that is inconsistent with natural viewing, undesirable perceptual effects may result. In the present paper, we first describe, the optical principles that underlie the COR display system. We then discuss the importance of binocular convergence and describe a COR display configuration that eliminates inconsistencies in the depth cues provided by displayed surface properties and halfocclusions.     

Salamander locomotion-induced head movement and retinal motion sensitivity in a correlation-based motion detector model

We report on a computational model of retinal motion sensitivity based on correlation-based motion detectors. We simulate object motion detection in the presence of retinal slip caused by the salamander's head movements during locomotion. Our study offers new insights into object motion sensitive ganglion cells in the salamander retina. A sigmoidal transformation of the spatially and temporally filtered retinal image substantially improves the sensitivity of the system in detecting a small target moving in place against a static natural background in the presence of comparatively large, fast simulated eye movements, but is detrimental to the direction-selectivity of the motion detector. The sigmoid has insignificant effects on detector performance in simulations of slow, high contrast laboratory stimuli. These results suggest that the sigmoid reduces the system's noise sensitivity.     

Evaluation of liquid‐crystal‐display motion blur with moving‐picture response time and human perception

Abstract— The moving‐picture response time (MPRT) for measuring liquid‐crystal‐display (LCD) motion blur was studied by several organizations in 2001. To determine the LCD motion blur that humans perceive, subjective evaluation experiments using the method of adjustment was conducted to find a strong correlation between perceived motion blur and extended blurred edge time (EBET) of the MPRT measurements. MPRT thus clearly indicates the degree of which humans perceive motion blur.     

Perceptually‐motivated Real‐time Temporal Upsampling of 3D Content for High‐refresh‐rate Displays

High‐refresh‐rate displays (e. g., 120 Hz) have recently become available on the consumer market and quickly gain on popularity. One of their aims is to reduce the perceived blur created by moving objects that are tracked by the human eye. However, an improvement is only achieved if the video stream is produced at the same high refresh rate (i. e. 120 Hz). Some devices, such as LCD TVs, solve this problem by converting low‐refresh‐rate content (i. e. 50 Hz PAL) into a higher temporal resolution (i. e. 200 Hz) based on two‐dimensional optical flow. In our approach, we will show how rendered three‐dimensional images produced by recent graphics hardware can be up‐sampled more efficiently resulting in higher quality at the same time. Our algorithm relies on several perceptual findings and preserves the naturalness of the original sequence. A psychophysical study validates our approach and illustrates that temporally up‐sampled video streams are preferred over the standard low‐rate input by the majority of users. We show that our solution improves task performance on high‐refresh‐rate displays.     

A perceived sharpness metric based on the luminance slope and overshoot of the motion‐induced edge‐blur profile

To reduce perceived motion blur on liquid crystal displays, typically various techniques such as overdrive, scanning backlight, black‐data insertion, black‐field insertion, and frame rate up‐conversion are widely employed by the liquid crystal display industry. These techniques aim to steepen the edge transitions by improving the dynamic behavior of the light modulation. However, depending on the implementation, this may result in the perception of irregularly shaped motion‐induced edge‐blur profiles. It is not yet fully understood how these irregularities in the steepened edge‐blur profiles contribute to the perceived sharpness of moving objects. To better understand the consequences of several motion‐blur reduction techniques, a perception experiment is designed to evaluate the perceived sharpness of typical motion‐induced edge‐blur profiles at several contrast levels. Relevant characteristics of these profiles are determined on the basis of the perception results by means of regression analysis. As a result, a sharpness metric with two parameters is established, where one parameter relates to the edge slope and the other to the overshoot/undershoot part of the motion‐induced edge‐blur profile.     

LCD motion‐blur estimation using different measurement methods

Abstract— The primary goal of this study was to find a measurement method for motion blur which is easy to carry out and gives results that can be reproduced from one lab to another. This method should be able to also take into account methods for reduction of motion blur such as backlight flashing. Two methods have been compared. The first method uses a high‐speed camera that permits us to directly picture the blurred‐edge profile. The second one exploits the mathematical analysis of the motion‐blur formation to construct the blurred‐edge profile from the temporal step response. Measurement results and method proposals are given and discussed.