## 4 Discussion  
The findings of this study demonstrate that a stationary, markerless 3D digitization approach using active stereo vision (SfS) with an integrated laser line can deliver reliable surface data in scenarios where traditional methods are either impractical or impossible. By eliminating the need for external reference markers and maintaining the scanning system in a fixed position relative to the object, the proposed method directly addresses key challenges associated with confined or hard-to-reach locations. This development signifies a substantial advancement for use cases such as in situ inspections of machine components (e.g., turbines, aircraft engines) and endoscopic scans in the medical field. A comparison of the presented system with existing industrial scanning techniques reveals several advantages. Conventional handheld or robotic scanners generally necessitate full or partial mobility around the object, which can be impractical within confined enclosures or in sensitive areas. Conversely, photogrammetric solutions frequently depend on distinct markers or expansive reference frameworks for alignment, a process that is similarly challenging when marker placement is not applicable. Furthermore, purely passive Shape from Motion or Shape from Stereo methods generally necessitate object or camera motion and are more sensitive to poorly textured surfaces. In contrast to these methods, the system proposed here employs active projection of a laser line onto the scene, thereby reducing the need for extensive texture while maintaining a compact, rigidly mounted design. However, the research also reveals several important limitations. Primarily, the accuracy and precision of the digitized data are contingent upon a multitude of intrinsic and extrinsic parameters, numbering 45 in the present design. This underscores the complexity of tuning the system for different objects and environments. The achievable accuracy is influenced by factors such as laser line thickness, camera resolution, stereo baseline, and ambient lighting conditions. The standard deviation of depth errors (sigma) ranging up to 0.4 mm on specific test surfaces underscores the necessity for meticulous parameter calibration, particularly in scenarios where sub-millimeter accuracy is imperative. In real industrial or medical settings, reflective or glossy surfaces, vibrations, and unpredictable lighting will likely intensify these challenges. In order to mitigate the aforementioned effects, strategies such as the application of matt coatings on shiny parts, the use of optical filters, or the use of higher-quality laser modules can be employed. It is imperative for users to reposition the laser to achieve wider coverage (either manually or using a stepper motor), which can increase the time required to acquire data. For highly detailed applications, more advanced structured-light approaches (e.g., projecting multiple lines or patterns) might be introduced to expedite scanning while preserving a markerless methodology. Despite the challenges, the benefits of in situ 3D scanning without object movement are evident. A comparison of the point clouds obtained from the in situ 3D scanning system with those from a commercial scanner reveals that the system achieves reasonable accuracy, on the order of tenths of a millimeter, even in the early prototype stage. This accuracy is observed for both planar surfaces and those of moderately complex geometry. In industrial contexts, the capacity to expedite the inspection of equipment internals has the potential to curtail downtime and costs. In the field of medicine, the acquisition of precise 3D data of anatomical structures through endoscopic means has the potential to enhance patient outcomes by facilitating informed diagnosis or guiding minimally invasive procedures. Future work will focus on refining hardware components, automating and further tuning parameters, and improving robustness in challenging environments.