Please enable JavaScript.

Coggle requires JavaScript to display documents.

All about augmented reality (A survey on augmented reality by Sicaru et al)

- - - - Display
        
        The user can see the virtual world through various display devices, such as: head-mounted display (HMD), hand held devices, monitors or any optical projection systems.
        
        Standard Head-Mounted Display (HMD)
        
        It is similar to a helmet, placed on the forehead and it is mostly used for aviation applications, but it can also be used in gaming, engineering and medicine.
        
        These closed-view displays use computer-generated imaginary superimposed on the real world view.
        
        One disadvantage of these closed-view helmets is that in case the power is cut off, the user is unable to see.
        
        The standard Head-Mounted Display (HMD) is closed-view and it does not allow the user to see the real world directly
        
        See-through Head-Mounted Display (HMD)
        
        The see-through HMDs allow light to pass through them and in case the power is cut off, they act like sunglasses.
        
        They are compact devices, lightweight, monocular or binocular and allow instant access to information either by optical system or video. Semi-transparent mirrors reflect the computer-generated images into the user's eyes.
        
        There are two main techniques that exist for see-through HMD: curved combiner and waveguide.
        
        The curved combiner diverge light rays for a wider field-of-view (FOV). The diverged rays need to travel to a single point, the user's eye, for a clear and focused image
        
        The waveguide or light-guide technique includes diffraction optics, holographic, polarized optics, reflective optics and projection. This technique is used in many applications and many companies such as Sony, Epson, Konica Minolta, Lumus, etc. have chosen it as a suitable technology for their devices
        
        Head-Up Display (HUD)
        
        Head-up display (HUD) is a transparent display, lightweight and compact that can show additional data and information and enables the user to remain focus on his task, without taking out too much of his field of view
        
        It was firstly used by pilots to show basic navigation and flight information.
        
        Google Glass is one of the most well-known HUD devices that have a touchpad, a camera and a display. This device allows the user to take pictures, go through old photos and events, offers information about weather and different news
        
        Another HUD device is Microsoft HoloLens, device that allows the user to interact with the colorful virtual objects, project different objects onto the floor and even manufacture objects.
        
        Virtual Retina Display (VRD)
        
        VRD is a personal display device under development at the University of Washington's Human Interface Technology Laboratory.
        
        This technology allows for the capture of real world to be directly scanned onto the retina of a viewer's eye. The viewer sees what appears to be a conventional display floating in space in front of them.
        
        EyeTap also known as Generation-2 Glass, captures rays of light that would otherwise pass through the center of the user's lens, and substitutes synthetic computer-controlled light for each ray of real light.
        
        The Generation-4 Glass (Laser EyeTap) also has infinite depth of focus and causes the eye itself to, in effect, function as both a camera and a display, by way of exact alignment with the eye and resynthesis (in laser light) of rays of light entering the eye.
        
        Mobile Devices (Phone and Tablet)
        
        Because mobile devices are really powerful and can act as small computers, they are great to display AR application.
        
        Not only do they offer the display technology, with big enough LCD screens, but they also offer cameras, GPS, processors and other sensors.
        
        Usually, the phone's camera is used to capture the real world and with the help of AR application, the virtual objects are superimposed in real time onto the phone's display.
      - Tracking
        
        In augmented registration, tracking devices are used for registration. By registration, virtual objects generated by a computer are merged into the real world image.
        
        The computer needs to have a powerful CPU and great amount of RAM in order to be able to process the images and interact accordingly with the user.
        
        It was identified that for AR, the tracking devices should be: mechanical, magnetic sensing, GPS (Global Positioning System), ultrasonic, inertia and/ or optics.
        
        These devices have different ranges, resolution, time response and setup that combined can generate different levels of accuracy and precision.
      - Input and Interaction
        
        The interaction between the user and AR world can obtained by: tangible interfaces, collaborative interfaces, hybrid interfaces or emerging multimodal interfaces.
        
        Tangible interfaces allow the user to interact with real world objects. VOMAR application, developed by [17], allows users to rearrange the furniture inside a room. The user's gestures represent intuitive commands and he can select, move or hide different pieces of furniture.
        
        Another input for the AR environment can be sensing gloves that provides tactile feedback. These gloves can use a range of sensors to provide the hand's position or can use vibration motors to simulate different surfaces
        
        Collaborative interfaces allow multiple users to connect and share the same virtual objects. This enhances teleconferences by sharing between participants the same 3Dwindows, display platforms, documents, etc.
        
        Hybrid interfaces allow the user to interact with the system through different interaction devices. A mixed reality system can be configured for the user's desire and it can adapt accordingly.
        
        Multimodal interfaces combine real object with speech, touch, hand gestures or gaze.
    - - The software used for AR is mostly focused on the application specificity.
      - It uses real world coordinates offered by the tracking devices and camera images.
      - Augmented Reality Markup Language (ARML) developed within the Open Geospatial Consotium (OGC) is used to create XML from the coordinates in order to obtain the location information.
      - By image registration, the captured images are analyzed. This process belongs to the computer vision field and it is mostly based on video tracking methods and algorithms.
      - There are some software development kits (SDK) for AR offered by Vuforia, ARToolKit, Layer, Wikitude, Blippar and Meta that enables developers to build their own AR environment.
      - Usually these methods consist of two parts.
      - The first stage detects the interest points, fiducial markers or optical flow in camera images. This step can use feature detection methods like corner detection, blob detection, edge detection or thresholding and/ or other image processing methods.
      - The second stage restores real world coordinate systems from the data obtained in the first page.
      - Some methods assume objects with known geometry are presented in the scene (Vuforia). In some of those cases the scene 3D structure should be pre-calculated. If part of the scene is unknown simultaneous localization and mapping (SLAM) can map relative positions
      - If no information about scene geometry is available, structure from motion methods like bundle adjustment are used.
      - Mathematical methods used in the second stage include projective (epipolar) geometry, geometric algebra, and rotation representation with exponential map, Kalman and particle filters, nonlinear optimization and robust statistics.