# A QR Code-Based Approach to Differentiating the Display of Augmented Reality Content
## 1 Introduction  
The rapid advance in the hardware and software of smart devices has benefited the development of augmented reality (AR) technologies. In recent years, AR can operate efficiently without heavy and expensive equipment in different scenarios, such as educational training, digital learning, product marketing, and industrial design [1, 2, 3]. Furthermore, by taking AR's capability of associating virtual objects with real space, many studies have applied it to spatial visualization [4]. Examples include combining the localization technique to improve interactive indoor navigation [5], helping people with limited peripheral vision identify things in the environment [6], and enhancing rehabilitation training for older people by providing a visualized guide [7]. In short, AR enables users to see virtual objects and models on their mobile phones. Most AR technologies are marker-based, meaning marker recognition is used to locate the relative position of 3D virtual models on the screen. Common development tools include ARToolkit, NyARToolKit, and AR Tag [8, 9, 10], and markers have different forms, such as frame markers, dot markers, split markers, data Matrix markers, ID markers, and template markers. These markers are usually simple squares, text, or patterns in black and white or grayscale, with the advantage of allowing the system to recognize patterns accurately and quickly when the light is dark or the camera pixels are insufficient. While AR is convenient, it has several limitations [4, 11, 12, 13] as follows:  
1. The marker and the virtual object must be registered and linked in advance on the online platform to track the relative position and direction between the camera and the tag, download the linked virtual object, and display it. In this case, the markerand the object cannot change dynamically, significantly limiting the effectiveness and immediacy. 2. Keeping the internet connection is necessary to access the AR system and download virtual objects in real-time. 3. The content, card size, image feature points, or print size of markers must meet certain conditions to maintain the system's stability. 4. Different companies have marker patterns that are not interchangeable, making it impossible to share sources and enable compatibility. As shown in recent studies [5; 14], the trend of AR would provide real-time computed and flexible media and content to let users interact with various virtual objects. Therefore, it is vital to resolve the limitations of the marker-based AR technique. Combining AR with the quick response barcode (QR code) can be a gateway to address the above issues. The QR code is a two-dimensional matrix developed by Denso-Wave company in 1994 [15; 16]. Based on this technique, the data content of a QR tag can be encoded and decoded efficiently. Therefore, more and more research has tried to combine mobile AR with QR codes [17; 18]. For example, [PERSON] et al. [17] applied QR code as an AR-based marker to track the angle of the QR Code and its positioning coordinates and mapped 3D virtual objects to the QR marker. VisionLens [18] also utilized a similar concept, establishing a QR Code for each product. After scanning the QR code, the AR virtual object and 3D animation will appear when mobile devices point at the product. In brief, the data content of the QR code can be a link to a virtual object or a uniform resource locator (URL). Therefore, when triggering the AR system, the location information of the QR marker can be estimated immediately and decode the data content of the URL to retrieve 3D virtual objects. Moreover, this process does not require users' pre-registration of the AR system. Unfortunately, current AR schemes [17; 18; 19; 20; 21; 22] align the same virtual object with the same marker. The AR system thus considers all users with the same maker the same role. In other words, the AR system can only display the same virtual content to various users.