As a simple, low-cost, and lightweight AR solution, Web AR is considered to be easy to spread. Usually, AR content can be opened directly on the phone without downloading an app, just by a link or by scanning a QR code. Scanning QR codes is one of the most common ways to turn on Web AR, but the designs that QR codes can present are limited and do not look beautiful.
　　
　　Recently, in order to make AR tags/QR codes more low-key and more integrated into daily life scenarios, Meta researchers have developed a solution for integrating invisible QR codes in the 3D printing process: InfraredTags. It is reported that the solution is based on the principle of infrared sensing. The invisible QR code adds AR markers to the items in life, and the AR effect superimposed on the items can be quickly identified without computer vision algorithms.
　　

　　It is understood that InfraredTags is a low-cost, simple process for embedding invisible QR codes in 3D printed objects. Invisible QR codes can be used as AR markers, using infrared cameras to trigger AR content or operation interfaces, such as scanning the QR code on the casing with the infrared camera of a mobile phone to control the volume of a speaker or the temperature of a thermostat. Even, you can use the QR code to superimpose AR information such as network name and password on the router, as well as read the 3D model of the 3D printed object, and turn the 3D printed object into a game controller. Invisible QR codes can also be embedded in the outer packaging of food, and after scanning with the infrared camera of the AR headset, information such as calories can be viewed.
　　
　　In fact, when it comes to mobile phones scanning objects to trigger AR, people often think of computer vision technology, which uses artificial intelligence algorithms to identify objects in the environment. In contrast, InfraredTags is simpler in design, does not require AI algorithms, and only needs to place invisible infrared sensor QR codes in the environment.
　　
　　Its characteristic is that a special filament material is used to embed the two-dimensional code, which will become transparent under the irradiation of the infrared camera. By combining the filaments, the two-dimensional code pattern invisible to the naked eye can be embedded. This process can be achieved using common 3D printing technology. Before printing, you can integrate 3D models, QR codes and triggerable UIs in the system. Next, adding a low-cost camera module to an off-the-shelf smartphone can recognize AR markers.
　　
　　Simply put, InfraredTags uses invisible QR codes to identify and locate 3D printed objects. Using QR codes to locate AR is a simple and low-cost solution, which is used to display AR advertisements, 3D AR models or implement some simple AR games in the early stage. However, the black and white QR code does not look good enough, and it is difficult to integrate with the product design. Although it is possible to design personalized color patterns, the theme elements of the QR code can be clearly seen.
　　
　　In contrast, Meta and MIT researchers have embedded the 3D printing process through more stealthy infrared sensing materials, allowing the QR code to appear in a form invisible to the naked eye, without affecting the design of the hardware.
　　
　　The principle is that infrared light can see through some materials that are opaque under visible light. For example, patterns made of infrared filaments are invisible to the naked eye in normal light, but become transparent under infrared light.
　　
　　Phones like the iPhone X already have infrared cameras, but some phone APIs don't allow third-party developers to access non-native apps. Therefore, the researchers developed an infrared camera plug-in compatible with existing mobile phone models. The plug-in includes a microprocessor, battery, IR LED, IR camera, visible light filter.
　　
　　The infrared light-sensing thin wire used by the researchers was customized by a German start-up company 3dk.berlin, which features a plastic filament design suitable for 3D printing systems. Furthermore, it is opaque to visible light and transparent or translucent under infrared light. To put it simply, two materials are used in the 3D printing process: plastic that can transmit infrared light and plastic that is opaque under infrared light. The combination of the two can print a two-dimensional code with sufficient clarity and contrast.
　　
　　3dk.berlin offers infrared filament for $5.86/100g for use in regular 3D printing. To the naked eye, the infrared filament is a slightly translucent black that becomes opaque after 3D printing.
　　
　　In addition, the researchers developed a software UI to bind AR content or information to the QR code. Multiple QR codes can be embedded on the 3D printed object to avoid scanning when other QR codes are blocked. In order to demonstrate the effect of InfraredTags controlling the game, the researchers 3D printed a steering wheel prop with an embedded ArUco mark, and connected the IR camera to the computer, and used the IR camera to locate the steering wheel to realize the interaction between the steering wheel and the computer game. In terms of details, the IR camera can accurately locate the direction and degree of steering wheel rotation by recognizing the rotation of the markings on the steering wheel.
　　
　　The researchers said: InfraredTags aims to replace the standard barcodes affixed to products, which are more durable and less conspicuous than ink-printed barcodes, and are directly embedded in the 3D printing process. It can be used in a variety of scenarios, such as being superimposed on all items sold in a grocery store, such as batteries, circuits, computers, auto parts, and more. In addition, it can also be printed on photos and album covers, and the metadata embedded in music and photos can be combined with physical objects in the form of AR to add additional information to offline scenes such as stores, museums, and libraries.