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.     

A consideration on motion‐image‐quality improvement of LCDs and video systems

Abstract— The motion image quality of video systems with hold‐type displays, such as LCDs or OLEDs, were studied with regard to dynamic spatial frequency response and data from subjective evaluations on motion blur. The system parameters of motion image quality, or frame rate (F) and temporal aperture (A^t), were investigated and their required values were derived. A smaller temporal aperture and/or higher frame rate can improve the dynamic response and motion image quality, but the parameters required in order to maintain a good dynamic response for high motion image velocity seems very difficult to implement, such as a frame rate of 900 Hz. Therefore, the performance goal of video systems is set on “limit of acceptance” for motion image quality, as a compromise. An equation or the relational expression between motion image velocity and required parameter values is derived based on dynamic response and data from subjective evaluations found in published studies. Possible examples of parameter sets are obtained from the equation. Those are (F = 300 Hz, A_t = 5/6), (F = 240 Hz, A_t = 2/3), (F = 120 Hz, A_t = 1/3), and (F > 360 Hz, A_t = 1).     

Motion‐adaptive alternate gamma drive for flicker‐free motion‐blur reduction in 100/120‐Hz LCD TV

Abstract— LCD motion blur is a well‐known phenomenon, and several approaches have been developed to address it. This includes very‐high‐performance approaches based on motion‐compensated frame rate conversion (MC‐FRC) and very‐low‐cost approaches based on impulsive driving. Impulsive‐driving schemes are attractive because of their low cost, but suffer from two significant issues — loss of luminance and large‐area flicker. A new impulsive‐driving approach using motion‐adaptive alternate gamma driving (MA‐AGD), which removes motion blur and preserves the original luminance level without causing large‐area flicker, is proposed.     

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.     

Flicker visibility in scanning‐backlight displays

Abstract— Scanning‐backlight technology reduces motion blur caused by the sample‐and‐hold effect of traditional liquid‐crystal displays. A side effect of impulse‐type backlight systems is that large‐area flicker may be introduced (like in displays using cathode‐ray tubes). The seriousness of the perceived large‐area flicker is investigated in perception experiments for various implementations of a scanning‐backlight system and for different types of image material. Results show that the main factors contributing to the visibility of large‐area flicker are refresh rate, temporal luminance distribution within a frame period, spatial luminance distribution in the image, and whether or not there is motion in the image.     

Scanning backlight for motion‐blur reduction on mobile displays

Abstract— Small‐form‐factor liquid‐crystal displays (LCDs) are mainly used in mobile applications (e.g., mobile phones, PDAs, and portable game consoles) but also in digital still cameras, video cameras, automotive applications, etc. Like all active‐matrix LCDs, mobile displays suffer from motion blur caused by the sample‐and‐hold effect. One option for improving the motion portrayal on active‐matrix LCDs is the use of a scanning backlight, which results in an imaging behavior similar to the one present in impulsive displays. In this paper, the realization of a scanning backlight for mobile displays is reported. This employs a backlight with seven individually lit segments for reducing the motion blur. Results of perception experiments performed with two identical displays confirm the benefit of using this technology. Optimal driving conditions result in a major improvement in motion portrayal on mobile LCDs.     

Motion blur reduction with triangular waveform emission and optimized enhance filter

Degradation of moving image quality by motion blur on hold‐type displays is a well‐known issue. In order to reduce motion blur, a number of driving methods, such as a higher frame rate and a shorter temporal aperture, have been proposed. Methods to reduce motion blur by means of signal processing as a precompensation method have also been proposed. In these methods, however, hold emission that emits light at a constant intensity during a frame is used. Since the spatial frequency response of the hold emission in a moving picture has a null point, the effectiveness of precompensation methods is limited to the lower‐spatial frequency domain. A triangular waveform emission has been investigated, and it has a higher spatial frequency response than hold emission. In the present paper, we calculated an optimized enhancement filter for the triangular waveform emission as a precompensation method and demonstrated its effectiveness for reducing motion blur by using the triangular waveform emission and the optimized enhancement filter. As a result, the optimized enhancement filter reduced motion blur and suppressed distortion that emerged when using a conventional enhancement filter.     

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.     

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.     

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.     

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.     

A psychophysical study of improvements in motion‐image quality by using high frame rates

Abstract— The ideal frame rate for the highest motion‐image quality with respect to blur and jerkiness is presented. In order to determine the requirements for avoiding these impairments, motion images from a high‐speed camera and computer graphics were combined with a high‐speed display to perform a psychophysical evaluation. The camera, operating at 1000 fps, and image processing were used to simulate various frame rates and shutter speeds, and a 480‐Hz CRT display was used to present motion images simulating various frame rates and time characteristics of the display. Subjects were asked to evaluate the difference in quality between motion images at various frame rates. A frame rate of 480 fps was chosen to be an appropriate reference frame rate that, as a first estimation, enables coverage up to the human‐dynamic‐resolution (HDR) limit based on another experiment using real moving charts. The results show that a frame rate of 120 fps provides good improvement compared to that of 60 fps, and that the maximum improvement beyond which evaluation is saturated is found at about 240 fps for representative standard‐resolution natural images.     

A study on a driving method of OLED displays for better motion image quality with adaptive temporal aperture control

Degradation of motion image quality by motion blur on hold‐type displays, such as liquid‐crystal displays and organic light‐emitting diode displays, is a well‐known issue. To improve motion image quality, a driving method with a shorter temporal aperture has been proposed. However, a shorter temporal aperture requires higher instantaneous luminance on displays. Higher instantaneous luminance accelerates the lifetime degradation of organic light‐emitting diode. Therefore, we have been developing a driving method with adaptive temporal aperture control for a longer lifetime and better motion image quality. However, two image quality degradations were perceived when this driving method was applied. One of these degradations was caused at the boundary between the different temporal apertures. The other degradation was caused by switching the temporal aperture between frames. Hence, we have also proposed transition area and period insertion methods to suppress these degradations. In this paper, we discuss the mechanism of these degradations and confirm the effectiveness of our proposed methods by subjective evaluations. In the results, the degradations were suppressed by inserting 80 lines of transition area and by inserting 50 frames of transition period.     

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.     

Differences between oculomotor and perceptual artifacts for temporally limited head mounted displays

We used perceptual and oculomotor measures to understand the negative impacts of low (phantom array) and high (motion blur) duty cycles with a high‐speed, AR‐likehead‐mounted display prototype. We observed large intersubject variability for the detection of phantom array artifacts but a highly consistent and systematic effect on saccadic eye movement targeting during low duty cycle presentations. This adverse effect on saccade endpoints was also related to an increased error rate in a perceptual discrimination task, showing a direct effect of display duty cycle on the perceptual quality. For high duty cycles, the probability of detecting motion blur increased during head movements, and this effect was elevated at lower refresh rates. We did not find an impact of the temporal display characteristics on compensatory eye movements during head motion (e.g., VOR). Together, our results allow us to quantify the tradeoff of different negative spatiotemporal impacts of user movements and make subsequent recommendations for optimized temporal HMD parameters.     

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.     

DLP Cinema™ projection: A hybrid frame‐rate technique for flicker‐free performance

Abstract— Film is recorded at 24 Hz, which is sufficient to achieve the effect of motion but is well within the flicker sensitivity of the human‐visual system (HVS) and thus would result in severe flicker. To avoid this, film projectors project at twice this rate, using a 48‐Hz screen refresh rate. While this greatly mitigates flicker, projected film images still exhibit considerable flicker in bright scenes. DLP Cinema? projection technology allows us to display images at any frame rate, and in practice we have been able to match the 48‐Hz refresh rate of film projectors. This paper describes a technique by which we take advantage of the fact that the HVS temporal sensitivity curve shows more sensitivity with bright content but much less sensitivity as content dims. This is done using the control versatility of the Digital Micromirror Device? (DMD?), which allows independent control of every bit. The result is an overall image signal that is beyond the HVS temporal sensitivity curve, resulting in the complete removal of any visible flicker. This technique gives DLP Cinema? projection its characteristic “solid” and “stable” appearance that standard film projection does not provide.     

LCD models to analyze and simulate motion artifacts

Abstract— In this paper, two models to evaluate the temporal behavior of liquid‐crystal displays are described: a model assuming a linear display behavior and a model that incorporates non‐linear effects. For the linear temporal model, it can be predicted that the response time starts to contribute to motion blur when it is longer than one‐sixth of the hold time and becomes dominant when it is longer than eight times the hold time. The non‐linear model can be used to visualize the appearance of effects that cannot be determined via linear system theory. Also, some means to reduce display artifacts are described and its impact is illustrated. Although the main focus in this article is on the temporal behavior of liquid‐crystal displays, the spatial properties defined by the pixel structure can be simulated as well. A formula for the spatio‐temporal display behavior is given, which can be evaluated numerically to simulate the perceived image for arbitrary image‐sequence input material.     

The effects of latency and motion blur on touch screen user experience

Touch interfaces are designed to be metaphors for physically manipulating virtual objects. However, this direct manipulation illusion is broken by the nonidealities of the device. We decouple and show the impact of touch‐to‐display latency and motion blur on the user experience of a touch system. Using a custom device, we achieve latencies down to ~1 ms, with frame rates up to 1000 Hz. Motion blur is reduced independently of frame rate using synchronized display modulation. Optimizing these metrics yields a dramatic improvement in the user experience, demonstrating the opportunity for higher performance in touch devices.