Terhi Mustonen

Examining mobile phone text legibility while walking

In this study, alternative methods for studying legibility of text while walking with a mobile phone were examined. Normal reading and pseudo-text search were used as visual tasks in four walking conditions. Visual performance and subjective evaluation of task difficulty were used as measures of text legibility. According to the results, visual performance suffers from increasing walking speed, and the effects are greater on reading velocity for pseudo-text search. Subjects also use more homogenous strategies when reading compared to pseudo-text search, and therefore it is concluded that reading is a more useful measure of legibility. Subjective measures are found to be more sensitive to small variations in legibility than objective measures, and give additional information about task demands. Hence, without both objective and subjective measurements important information about legibility in different conditions and with different tasks will be lost.

Mapping the Identity of a Viewed Hand in the Motor System: Evidence from Stimulus-Response Compatibility.

Brain-imaging research has shown that a viewed acting hand is mapped to the observers hand representation that corresponds with the identity of the hand. In contrast, behavioral research has suggested that rather than representing a seen hand in relation to ones own manual system, it is represented in relation to the midline of an imaginary body. This view was drawn from the finding that indicated that the posture of the viewed hand determines how the hand facilitates responses. The present study explored how an identity of a viewed static hand facilitates responses by varying the onset time and the posture of the hand. The results were in line with the view that an observed hand can activate the observers hand representation that corresponds with the identity of the hand. However, the posture of the hand did not influence these mapping processes. What mattered was the perspective (i.e., egocentric vs. allocentric) from which the hand was viewed.

A new method for evaluating the subjective image quality of photographs: dynamic reference

The Dynamic Reference (DR) method has been developed for subjective image quality experiments in which original or undistorted images are unavailable. The DR method creates reference image series from test images. Reference images are presented to observers as a slide show prior to evaluating their quality. As the observers view the set of reference images, they determine the overall variation in quality within the set of test images. This study compared the performance of the DR method to that of the standardized absolute category rating (ACR) and paired comparison (PC) methods. We measured the performance of each method in terms of time effort and discriminability. The results showed that the DR method is faster than the PC method and more accurate than the ACR method. The DR method is especially suitable for experiments that require highly accurate results in a short time.

Visual Performance With Small Concave and Convex Displays.

Objective: In this study, we aim to investigate how users’ visual performance with a small flexible display changes based on the direction (i.e., convex, concave) and the magnitude (i.e., low, high) of the display curvature. Background: Despite the wide interest in flexible display materials and deformable displays, the potential effects of nonplanar display surfaces on human perception and performance have received little attention. This study is the first to demonstrate how curving affects visual performance with an actual flexible display (4.5-in. active-matrix organic light-emitting diode). Method: In a series of three experiments, we compared the performance with a planar display to the performance with concave and convex display surfaces with low and high curvature magnitudes. Two visual search tasks were employed that required the subject to detect target letters based on their contrast (Experiments 1 and 2) and identity (Experiment 3). Performance was measured as the sensitivity of target detection (d′) and threshold time of the search, respectively. Results: There were similar sensitivities for targets across the curvature variants, but the high-magnitude curvatures resulted in prolonged search times, especially for the convex form. In both of the tasks, performance was dependent on the display location, which was defined as the target’s distance from the display center. Conclusion: High curvature magnitudes should be avoided, even in small displays, because large local changes in visual stimuli decrease processing speed outside the central display. Application: The findings have implications for the development of technologies, applications, and user interfaces for flexible displays and the design of visual display devices.

30.1: Invited Paper: OLED Lifetime Issues in Mobile Phone Industry

Lifetime issues have been hot topic through the history of OLED. Escpecially blue color has been problematic. A lot of research work has been carried out in OLED industry to improve the lifetime figures and results have been encouraging. However, it has been difficult to the mobile phone terminal makers to define, what is the acceptable lifetime in phone application. The limited lifetime is visible in the first place in the form of burn in images. These two issues have been the focus of this study.

Ergonomic evaluation of ubiquitous computing with monocular head-mounted display

In this paper, the authors conducted an experiment to evaluate the UX in an actual outdoor environment, assuming the casual use of monocular HMD to view video content while short walking. In conducting the experiment, eight subjects were asked to view news videos on a monocular HMD while walking through a large shopping mall. Two types of monocular HMDs and a hand-held media player were used, and the psycho-physiological responses of the subjects were measured before, during, and after the experiment. The VSQ, SSQ and NASA-TLX were used to assess the subjective workloads and symptoms. The objective indexes were heart rate and stride and a video recording of the environment in front of the subjects face. The results revealed differences between the two types of monocular HMDs as well as between the monocular HMDs and other conditions. Differences between the types of monocular HMDs may have been due to screen vibration during walking, and it was considered as a major factor in the UX in terms of the workload. Future experiments to be conducted in other locations will have higher cognitive loads in order to study the performance and the situation awareness to actual and media environments.

P‐12: The Effect of Character Size and Contrast on Performance in Pseudo‐text and Letter‐search Tasks

The purpose of the study was to compare pseudo-text and lettersearch tasks in studying character sizes in different contrast conditions. Four character sizes (0.14, 0.16, 0.22, and 0.24 deg) and two contrast levels (CMichelson=0.06 and CMichelson=0.99) were used. According to the results, search performance improved with increasing character size and contrast in both tasks. Contrast had more effect on performance in the letter-search task than in the pseudo-text task. Consequently, the letter-search method may be better for investigating small displays in bright lighting conditions, which usually cause low contrast in displays. However, the use of the pseudo-text method is less timeconsuming because the results were less variable. 1. Introduction ease with which information can be read from a screen is an increasingly important issue in commercial competition of display technology. The influence of visual attributes like sharpness and contrast on displayed text is well known. Details in layout, for instance character size and type, are factors that also affect visual quality. However, the methods, variables, and criteria that should be used in order to get the most reliable results concerning quality of displayed text are not obvious. Furthermore, different requirements of varying display sizes and lighting conditions may cause a single method to be insufficient for all test configurations. In this paper we compare two methods, pseudo-text and lettersearch, that have previously been applied in examining properties of displayed text. The aim of the present study was to compare pseudo-text and letter-search tasks in studying character size effects and to evaluate the applicability of the methods in future studies concerning small displays in variable lighting conditions.

Estimating text legibility of a mobile display on the basis of translational vibration caused by walking

— In this study, the effect of vibration on mobile-phone text legibility caused by walking was examined. Legibility was measured as reading performance and subjective task load when reading from a mobile-phone display while walking on a treadmill at 1.5 km/hour, 3 km/hour, and an individually defined speed (3.9 km/hour on average). Vibration was measured on the vertical, lateral, and fore-and-aft axes during walking. Vibration amplitude was calculated in five different frequency bands (1, 2, 4, 8, and 16 Hz), and correlated with the legibility measures. The amplitude increased most on the vertical and fore-and-aft axes as a function of walking speed, and the increase was largest in the 2-Hz frequency band. Legibility decreased concurrently with increasing vibration. The strong correlation between vibration characteristics and legibility measures suggests that vibration characteristics could, to some degree, be used in estimating small-display legibility while walking.

Imaging lens design using image quality metric

In the case of imaging optics for imaging cellular phones, special attention has to be paid on the cost of the lens system. The number of lens elements has to be minimized, but the image quality has to be maximized. It is important that optimum quality/cost - ratio is found. The image sensor characteristics and human visual system preferences have to be taken into consideration as well for the design. In this paper, we present our new image quality metric. The performance of the metric is investigated using subjective tests on different lens designs and compared with MTF metric. We show that our metric has a good correlation with human observer and performs better than MTF metric. Finally, we give some examples of optimization based on our metric.

Upper nasal hemifield location and nonspatial auditory tones accelerate visual detection during dichoptic viewing

Visual performance is asymmetric across the visual field, but locational biases that occur during dichoptic viewing are not well understood. In this study, we characterized horizontal, vertical and naso-temporal biases in visual target detection during dichoptic stimulation and explored whether the detection was facilitated by non-spatial auditory tones associated with the target’s location. The detection time for single monocular targets that were suppressed from view with a 10 Hz dynamic noise mask presented to the other eye was measured at the 4° intercardinal location of each eye with the breaking Continuous Flash Suppression (b-CFS) technique. Each target was either combined with a sound (i.e., high or low pitch tone) that was congruent or incongruent with its vertical location (i.e., upper or lower visual field) or presented without a sound. The results indicated faster detection of targets in the upper rather than lower visual field and faster detection of targets in the nasal than temporal hemifield of each eye. Sounds generally accelerated target detection, but the tone pitch-elevation congruency did not further enhance performance. These findings suggest that visual detection during dichoptic viewing differs from standard viewing conditions with respect to location-related perceptual biases and crossmodal modulation of visual perception. These differences should be carefully considered in experimental designs employing dichoptic stimulation techniques and in display applications that utilize dichoptic viewing.