Arago by Rigsters
Meet Arago, the automated photogrammetry rig developed and manufactured by Rigsters in Copenhagen. It is meant to facilitate the tedious process of capturing optimal dataset for photogrammetry. Its mission is to reach an ultimate one-button solution universal and flexible enough to fit most of our digitalisation needs.
Arago’s main characteristics include portability, flexibility, and speed of capture. Not mentioning the most important aspect – cost-effectiveness. Arago is still a prototype in the beta-testing stage with more features yet to be added to expand the core functionality.
Hardware & Software solution tailored for capturing optimal datasets for photogrammetry. Arago is suitable for most object types thanks to 5 motion axis and adaptable scan volume.
Besides manual control options, Arago provides several automatic capture modes for generating ideal coverage. Pathfinding algorithms ensure fastest and safest travel around an object.
Intuitive 3D interface mirrors the physical environment to assists in safe motion and object detection. It offers flexible trajectory configuration and expandable capture preset library.
High speed and repeatability are ideal for capturing items in large quantities. Configurable data management features mitigate the need for tedious manual structuring.
Full control for up to 6 digital cameras for synchronised capture along with 15 kg payload. Controller software includes camera agnostic or expanded Nikon tethering control.
Foldable and lightweight construction allows for simple and fast assembly. Weighing less than 30 kg, Arago can be easily transported between scanning locations.
Arago is suitable for capturing objects from 1 cm3 up to 1 m3, dependant on the camera+lens combinations. It is possible to capture larger volumes by repositioning the object and using wide angle lenses. Turntable module supports up to 100 kg payload, which can be increased on demand.
The turntable module can work independent of the system and has several different mounting elements for diverse objects. Besides the 360° rotating platform, the module has a secondary moving axis to best suit capturing elongated objects. It increases the capture volume and offers additional camera positioning flexibility.
CAMERA TILT MODULE
Active 7 port USB 3.0 hub is integrated for reliable connection to multiple cameras. Also, we have developed a custom triggering system for 3 DSLR cameras with flash trigger synchronization. Unlike most off-the-shelf triggering options, our custom system can measure the shutter lag of each individual DSLR and adjust the trigger timing algorithm for precise shutter release at 1/200 sec with different camera models.
We have included depth cameras for real-time sensing the target object for the process we call pre-scan. This feature generates a rough 3D mesh directly in the software’s 3D interface. This geometry helps generating object shape-specific capture positions. Each new captured object helps improve the algorithms. Due to the complex nature of this feature, it will remain in development with help from beta testers.
There is no simple formula to calculate an average speed of capture due the complexity of individual objects, scale and chosen image coverage. Nevertheless, in our experience capturing 600 pictures for one object takes less than 10 mins by using 3 cameras and average 2 seconds delay in between photographs to account for shutter speed or strobe recycle times.
The main frame is built from black anodised aluminium that is both lightweight and durable. For all the moving elements we use grease-less Igus linear motion sliders powered by stepper motors from Oriental Motors with Neugard high performance gearboxes. All the cables are harnessed into cable chains to avoid any hanging wires.
BUILT IN ELECTRONICS BRAIN
No external motion control units are needed since they are fully integrated together with a custom power supply for the entire system. Arago’s electronics brain is modular and based on Tinkerforge units with motor controllers, proximity and orientation sensors. Communication with the software can be done through one ethernet cable or wirelessly.
We have decided to use Unity game engine for its capabilities of 3D interface integrations and ability to simulate the physical environment. By having a 3D model of Arago in the scene we are able to simulate the motion sequence in the most accurate way. Pathfinding algorithm finds the fastest route between all the camera positions by using ray tracing and iterating through all the possible paths. Furthermore, it check for out-of-camera-view or unreachable positions that are automatically discarded.
Manual control of all the motion axis can be performed directly in the interface, using a wireless controller or a keyboard input. Capturing positions can be set manually for full control and through configurable position generation modes.
Camera loop mode enables the configuration of multiple elevation steps and turntable rotation degrees for a simple capture setup.
To ensure even distances to the object for the best pixel/mm ratio distribution, you can generate 3D primitives corresponding to the size/shape of an object or use of the Pre-Scan function.
Since Rigsters team is working in close collaboration with Cultural Heritage institutions, safety becomes a very important aspect of Arago. While simulating the motion of the rig, the software constantly checks for any possible collisions with the target object and any additional environment elements (light gear, stands, diffusion panels, etc.). The 3D environment can be easily configured using conventional 3D tools within the software. Hardware failsafe mechanisms are directly implemented within Arago while any occurring malfunctions are being recorded by a logging system for easier troubleshooting.
Camera agnostic mode allows Arago to use a modular approach in controlling almost any digital camera. The agnostic mode can be used alongside with the tethering software of your choice. Arago’s software allows specifying the settings and the capture algorithm will dynamically adjust. Synchronized triggering can be done through the camera’s remote control port with configurable focus and shutter pins.
The software has full integration of Nikon SDK utilizing its functions like live view, dynamic camera settings modifications and file management. To ensure complete focus coverage, focus stacking sequence can be repeated through all the capture positions and adapt to object’s size and orientation. Thousands of photos can be taken automatically without the user having to constantly do manual adjustments.
We are currently investigating different camera manufacturers SDK support within Arago and will prioritise based on received feedback.
To increase the precision of the capture setup and final 3D mesh we want to integrate a structured light or laser capture module directly in Arago.
We can record all the capture sequence data at the moment, but planning to create smart reporting features allowing for integration with photogrammetry data management solutions like the Cultural Heritage Imaging (CHI) Digital Lab Notebook or other user-specific options.