Hanhoon Park

Invisible marker tracking for AR

We introduce a novel tracking system based on invisible markers which are created/drawn with an IR fluorescent pen. The tracking system consists of one scene camera, one IR camera, and one half mirror. The two cameras are positioned in each side of half mirror so that their optical centers coincide with each other. We track the invisible markers using the IR camera and visualize AR in the view of the scene camera. Thus, it works as a robust marker-less tracking system. Experimental results are given to demonstrate the viability of the proposed system.

One-handed interaction with augmented virtual objects on mobile devices

We present a one-handed approach for augmented reality and interaction on mobile devices. The proposed application considers common situations with mobile devices such as when a users hand holds a mobile device while the other hand is free. It also supports natural augmented reality environment such as when a user interacts with augmented reality contents anytime and anywhere without special equipment such as visual markers or tags. In our approach, a virtual object is augmented on the palm of a users free hand, as if the virtual object is just sitting on the palm, using a palm pose estimation method. The augmented virtual object reacts (e.g. moving or animation) to motions of the hand such as opening or closing the hand based on fingertip tracking. Moreover, it provides tactile interactions with the virtual object by wearing a tactile glove with vibration sensors. This paper describes how to implement the augmented reality application, and preliminary results show its potential as a new approach to mobile augmented reality interaction.

Fast view synthesis using GPU for 3D display

In this paper, we develop a fast view synthesis method that generates multiple intermediate views in real time for a 3D display system when the camera geometry and the depth map of the reference views are given. The proposed method achieves a faster view synthesis than previous approaches by processing in parallel the entire computations required for the view synthesis in GPU. Specifically, we use a specialized GPU architecture to control the GPU device and to optimize the speed effectiveness of the proposed fast view synthesis method. To increase the processing speed, we adapted all the processes for the view synthesis to a single instruction multiple data (SIMD) structure that is a main feature of GPU programming, we maximized the use of the high-speed memories on the GPU device, and we optimized the implementation. As a result, we could synthesize 8 intermediate view images with a size of 1024 by 768 pixels within 0.147 second.

Surface-Independent direct-projected augmented reality

Some issues on direct-projected augmented reality (DirectAR) are addressed: the projection may be geometrically distorted due to the non-planar surface (geometric distortion); the projection cannot be seen to user as intended because the position of the projector is not the same as that of the user’s viewpoint (viewpoint-ignorant projection); the projection may be modulated by surface color (radiometric distortion); the projected area may not have uniform brightness when the projection is obliquely headed for the surface (uneven projection). We propose an integrated framework for handling all the problems. Experimental results demonstrate that the problems unavoidable in surface-independent DirectAR can be successfully resolved.

Content adaptive embedding of complementary patterns for nonintrusive direct-projected augmented reality

In direct-projected augmented reality, the visual patterns for compensation may distract users despite users would not be interested in the compensation process. The distraction becomes more serious for dynamic projection surface in which compensation and display should be done simultaneously. Recently, a complementary pattern-based method of efficiently hiding the compensation process from users view has been proposed. However, the method faced the tradeoff between the pattern imperceptibility and compensation accuracy. In this paper, we embed locally different strength of pattern images into different channels of the projector input images (AR images) after analyzing their spatial variation and color distribution. It is demonstrated that our content adaptive approach can significantly improve the imperceptibility of the patterns and produce better compensation results by comparing it with the previous approach through a variety of experiments and subjective evaluation.

Invisible marker based augmented reality system

Augmented reality (AR) has recently gained significant attention. The previous AR techniques usually need a fiducial marker with known geometry or objects of which the structure can be easily estimated such as cube. Placing a marker in the workspace of the user can be intrusive. To overcome this limitation, we present an AR system using invisible markers which are created/drawn with an infrared (IR) fluorescent pen. Two cameras are used: an IR camera and a visible camera, which are positioned in each side of a cold mirror so that their optical centers coincide with each other. We track the invisible markers using IR camera and visualize AR in the view of visible camera. Additional algorithms are employed for the system to have a reliable performance in the cluttered background. Experimental results are given to demonstrate the viability of the proposed system. As an application of the proposed system, the invisible marker can act as a Vision-Based Identity and Geometry (VBIG) tag, which can significantly extend the functionality of RFID. The invisible tag is the same as RFID in that it is not perceivable while more powerful in that the tag information can be presented to the user by direct projection using a mobile projector or by visualizing AR on the screen of mobile PDA.

Undistorted projection onto dynamic surface

For projector-based augmented reality systems, geometric correction is a crucial function. There have been many researches on the geometric correction in the literature. However, most of them focused only on static projection surfaces and could not give us a solution for dynamic surfaces (with varying geometry in time). In this paper, we aim at providing a simple and robust framework for projecting augmented reality images onto dynamic surfaces without image distortion. For this purpose, a new technique for embedding pattern images into the augmented reality images, which allows simultaneous display and correction, is proposed and its validity is shown in experimental results.

Simultaneous Geometric and Radiometric Adaptation to Dynamic Surfaces With a Mobile Projector-Camera System

Existing geometric and radiometric compensation methods for direct-projected augmented reality focus on static projection surfaces rather than dynamic surfaces (with varying geometry in time). We aim at providing an effective framework for projecting a sequence of augmented reality images onto dynamic surfaces without geometric and radiometric distortion. We present our design of a special pattern image for simultaneous geometric and radiometric compensation and evaluate two different techniques for embedding the pattern image into augmented reality images. The validity of the proposed method is examined through a variety of experiments with a mobile projector-camera system.

Efficient mobile museum guidance system using augmented reality

We propose a mobile augmented reality (AR) system for helpful and efficient museum guidance. The system can provide not only useful information of exhibitions such as their inside view, origination, and how-to-use, but also a variety of interactions with the exhibitions. The system prototype is implemented on ultra mobile personal computer (UMPC) which is equipped with a camera, an ultrasound receiver, and a gyro sensor. The system function consists of two parts: tracking part, and event handling and visualization part. The tracking part consists of two parts again: global pose tracking part using ultrasound sensors and a gyro sensor, and local pose tracking part using a vision sensor which computes effectively the camera pose under less-controlled environments by combining edge information with feature point information of the camera images. The usefulness of the proposed system and user satisfaction are evaluated through the experimental results in various scenarios.

Subjective Evaluation on Visual Perceptibility of Embedding Complementary Patterns for Nonintrusive Projection-Based Augmented Reality

In projection-based augmented reality (AR) alleviating visual distraction of patterns has been a great challenge. As a representative one, a method of embedding patterns and their complements (hereafter, we call the pairs complementary patterns) into AR images alternately has been proposed recently. This paper presents subjective evaluation results and their statistical analysis on the visual perceptibility of embedding complementary patterns in different ways in a standard hardware environment. Then, we explore the constraints for embedded complementary patterns to be less perceptible. As expected, high projector refresh rate and low pattern strength were the general conditions for a decrease in the perception of embedded complementary patterns. However, reducing pattern size and projecting complementary patterns with an interval were also among the factors affecting the results. Detailed constraints are given in the experimental results. Also, we present which constraint is more dominant for pattern perceptibility.