Augmented Reality (AR)

1.3.1. The Definition and Features of AR

Milgram and Kishino provided a ‘Reality-Virtuality (RV) continuum’ idea to describe the augmented reality (AR) as shown in Figure 3. Augmented reality is in the mixed reality which is between real environment and virtual environment. What the user precept is more close to virtual is augmented virtuality (AV); in contrast, what the user precept is more close to real environment is augmented reality (AR) (Milgram, Takemura, Utsumi, & Kishino, 1995).

Figure 3: Milgram’s Reality-Vituality Contiuum (Milgram et al., 1995).

Azuma gave a more easy-to-understand definition of augmented reality (Azuma, 1997). Azuma defined augmented reality is a variation of virtual reality. Virtual reality completely immerses the user in a virtual environment; that means users cannot see the real world around him/her and what he/she sees are virtual. However, augmented reality allows users to see the virtual objects within the real world. Some research also defined that augmented reality requires the head-mounted displays (HMDs), actually not all the application examples of augmented reality need the head-mounted displays. So, Azuma re-defined that augmented reality has three characteristics:

 combines real and virtual,

 is interactive in real time, and

 is registered in three dimensions.

Augmented reality is to enhance the users’ perception and interaction with the real world through a virtual objects or environment in real time.

Recent advances in hardware (mobile device, wireless network) and software (applications) for mobile technology enable the development of mobile augmented reality (mobile AR) and its application. Papagiannakis, Singh and Magnenat-Thalmann defined the properties of mobile augmented reality as following (Papagiannakis, Singh,

& Magnenat‐Thalmann, 2008):

 combines real and virtual objects in a real environment,

 runs in real-time and mobile mode,

 registers (aligns) real and virtual objects with each other, and

 the virtual augmentation is based on dynamic, three dimensional objects (e.g.

interactive, deformable virtual characters).

According the properties above, the necessary components of mobile augmented reality are (a) hardware computational platform, (b) display, (c) tracking, (d) wireless network,

(e) wearable input and interaction and (f) software. Moreover, to develop the mobile augmented reality technology, three technologies are considered to be important as well:

 mobile computational platform devices,

 augmented reality system architecture and content, and

 wireless networking.

1.3.2. The Display Modes of AR

In section 1.3.1, not all the application examples of augmented reality require head-mounted displays was mentioned. Here in this section, the display modes of augmented reality is presented. According to Bimber and Raskar’s report in 2005, the display modes of augmented reality were categorized into several types (Bimber &

Raskar, 2005).

 Head-attached displays: These kinds of displays require the users to wear the display system on the head. It includes

- retinal displays,

- head-mounted displays, and - head-mounted projective displays.

 Hand-held displays: The conventional examples of hand-held displays are Tablet PCs, PDA, cell phone and Smartphone. It also divided into two types:

- video see-through hand-held displays, and - optical see-through hand-held displays.

 Spatial displays: These kinds of displays are different from body-attached displays (head-attached, hand-held). It also includes three subtypes:

- screen-based video see-through displays, - spatial optical see-through displays, and

- projective-based spatial displays.

There are three ways to conduct augmented reality: marker-based, markerless, and gesture-based. Most applications of augmented reality now are using marker-based recognition technology.

1.3.3. The Examples in Science Education of AR

Bilinghurst’s Magic Book was first application to use augmented reality in education. People could read the book without any technology like how we read as usual. However, people could also read the book with the display system. When people read the page with display system, they saw three-dimensional models pop up on the page. The book with the augmented reality technology is an enhanced version of traditional 3-D pop up book (Billinghurst, Kato, & Poupyrev, 2001). In Liao’s article, some applications of augmented reality in science education were reviewed. Here, three examples of chemistry, biology and outdoor nature science of the application of augmented reality chosen from Liao’s article are presented (Liao, 2010).

Fjeld and Voegtli had reported a system benefited chemistry education called augmented chemistry. With the augmented chemistry, users can use the display system to look at the booklet. There were elements on the booklet. Users who are having a display system look at the booklet, the ball-stick 3-D model of the element would show up (Fjeld & Voegtli, 2002).

Juan, Beatrice and Cano described a system which used augmented reality for learning the interior of human body as shown in Figure 4. To evaluate this system, the children of the Summer School of the Technical University of Valencia participated in.

The control group used a monitor as the visualization system and the keyboard to interact with the system while the experimental group used the head-mounted display as

the visualization system and the tangible interface to interact with the system. The results showed that there was not a statistical significant difference between the control and experimental group. But participants considered the system was useful for learning the interior of human body and even for other subjects (Juan, Beatrice, & Cano, 2008).

Figure 4: Juan’s AR Human Body System (Juan et al., 2008).

The last example is outdoor natural science learning. Liu, Tan, and Chu reported their mobile learning system with augmented reality and RFID (radio frequency identification) technology as shown in Figure 5. To evaluate this system, elementary school students in Taiwan were participated. The learning setting was in a nature park in Taiwan, students carried a PDA to explore the park (Figure 5(A)). They used a RFID reader on the PDA to sensor the RFID tag on the information board (Figure 5(B)). The identification code of RFID code was transmitted to the server, and then the relevant information returned to the students’ PDA (Figure 5(C)). After students finished the exploration in the park, they received a test. The results showed that the mobile outdoor learning improved students’ learning and were able to attract students’ interest in learning (Liu, Tan, & Chu, 2009).

(A)

(B)

(C)

Figure 5: Outdoor Natural Science Learning with AR (Liu et al., 2009).

(A) The equipments of mobile outdoor natural science learning with AR technology (B) Photographs of the outdoor learning activity.

(C) Screenshots of the interface of the mobile device with AR technology.