Pursuing new display techniques based on insights into human visual perception can reveal new possibilities for visual information devices. Here, we propose a novel information presentation technique that exploits the perceptional features during rapid eye movements called saccades by using a fast remote eye-measuring method. When light sources are fixed on a vertical line, and the flashing pattern is changed quickly during a horizontal saccade, 2D images can be perceived due to spatio-temporal integration in the human vision system. We use this phenomenon to present 2D images with only one-dimensional light sources, and to show these images even in midair. The flashing cycle and flash timing of light sources are important elements in developing the design theory for this display technique. The flashing cycle determines the maximum resolution of a perceived 2D image. The flash timing is a crucial issue for our purpose because 2D images are perceived only when the timing of the saccade coincides with the flash timing. Therefore, in this paper, we describe the relationship between a flashing cycle and the maximum resolution of a perceived 2D image, and then propose a concise saccade detection method. By using this method, saccades can be detected and the light sources can be flashed within the saccade interval as it occurs in real time, and 2D images can be successfully presented.

We describe experiments designed to measure gaze direction perception capability of humans under face-to-face and display mediated conditions. Gaze perception capability was determined by means of the absolute values of the pitch differences between a looker's actual regards and participants' judgments. We compared the capability under face-to-face, stereoscopic image, and monoscopic image conditions. On average, participants perceived the looker's gaze direction most accurately under the face-to-face condition. As expected, the accuracy under the stereoscopic image condition was higher than the results obtained under the monoscopic image condition. However, individual data did not follow the expected order and our exploratory experiments showed that participants with narrower interpupillary distance than the distance between two stereo cameras had difficulty in judging gaze directions. We also found that the perception of the pitch component of gaze direction is affected by gaze transmission methods but the yaw component is robust and is not affected by the transmission conditions.

Unconstrained measurement of human head motion is essential for HMDs (headmounted displays) to be really interactive. Polhemus sensors developed for that purpose have deficiencies of critical latency and low sampling rates. Adding to this, a delay for rendering virtual scenes is inevitable. This paper proposes methods that compensate the latency and raises the effective sampling rate by integrating Polhemus and gyro sensors. The adoption of quaternion representation enables us to avoid singularity and the complicated boundary process of rotational motion. The ability of proposed methods under various rendering delays was evaluated in the respect of RMS error and our new correlational technique, which enables us to check the latency and fidelity of a magnetic tracker, and to assess the environment where the magnetic tracker is used. The real-time implementation of our simpler method on personal computers is also reported in detail.

See-through head-mounted displays (STHMDs), which superimpose the virtual environment generated by computer graphics (CG) on the real world, are expected to be able to vividly display various simulations and designs by using both the real environment and the virtual environment around us. However, we must ensure that the virtual environment is superimposed exactly on the real environment because both environments are visible. Disagreement in matching locations and size between real and virtual objects is likely to occur between the world coordinates of the real environment where the STHMD user actually exists and those of the virtual environment described as parameters of CG. This disagreement directly causes displacement of locations where virtual objects are superimposed. The STHMD must be calibrated so that the virtual environment is superimposed properly. Among the causes of such errors, we focus both on systematic errors of projection transformation parameters caused in manufacturing and differences between actual and supposed location of user's eye on STHMD when in use, and propose a calibration method to eliminate these effects. In the calibration method, the virtual cursor drawn in the virtual environment is directly fitted onto targets in the real environment. Based on the result of fitting, the least-squares method identifies values of the parameters that minimize differences between locations of the virtual cursor in the virtual environment and targets in the real environment. After we describe the calibration methods, we also report the result of this application to the STHMD that we have made. The result is accurate enough to prove the effectiveness of the calibration methods.

A teleexistence manipulation system was evaluated quantitatively by comparing tasks of tracking a randomly moving target under several operational conditions. The effects of various characteristics, e.g., binocular vision and the effect of natural arrangement of the head and the arm, are analyzed by comparing quantitatively the results under these operational conditions. A human tracking transfer function was measured and used for comparison. The results revealed the significant dominance of the binocular vision with natural arrangement of the head and arm, which is the most important characteristic of teleexistence.

To control a slave robot in poor visibility environments, an experimental extended teleexistence system using virtual reality was constructed. The environment model was constructed from the design data of the real environment. When virtual reality is used for controlling a slave robot, the modeling errors of the environment model must be calibrated. A model-based calibration system using image measurements is proposed for matching the real environment and the virtual environment. The slave robot has an impedance control system for contact tasks and for compensating for the errors that remain after the calibration. After the calibration, an experimental operation in a poor visibility environment was successfully conducted.