## 1 Introduction  
The implementation of reverse engineering technologies in the field of hard-to-reach diagnostics is currently one of the research challenges in several industry sectors, including manufacturing, transportation, energy, medical, and other sectors [1]. Visual inspection as a method of engineering diagnosis has been used for several decades in the diagnosis of hard-to-reach areas [2]. In certain areas of its application, this diagnostic method is the fastest and least expensive, and in certain cases, it is the only usable method within non-destructive testing. For this purpose, endoscopic devices, especially industrial videoscopes, are used. Their utilization in the field of diagnostics of hard-to-reach places provides several advantages, e.g., rapidity of obtaining the necessary information, relatively low costs of the technology compared to other technologies of non-destructive testing, etc. The main disadvantages of conventional endoscopic inspection can be considered to be the acquisition of only images of the surface without spatial information about its shape and surface [3]. For this reason, it is not possible to effectively and accurately measure the geometry of the surface geometry features of objects and their extent, which include cracks, defects, and other damage. To obtain this information, particularly the distance between the sensor and the surface points of objects, research is being conducted on the implementation of reverse engineering elements in the field of diagnostics of hard-to-reach places. A challenge in this area is the use of reverse engineering techniques within confined spaces. The reverse engineering techniques currently used require a certain minimum amount of space for the implementation of the digitization process in order to use the digitization equipment. Minimum mutual distance between the sensors and the object are also required. Furthermore, conventional digitizing devices are, in most cases, designed in sizes that do not allow their utilization within hard-to-reach places. Due to technological advances, sensor, reverse engineering, and endoscopy technologies are continuously being developed with the aim to develop technologies with higher resolution, higher accuracy, and smaller dimensions. This fact allows their progressive implementation in the field of hard-to-reach diagnostics, and this paper is dedicated to this issue. To address this challenge, an in-depth analysis of the current state of the art and knowledge in the field of reverse engineering and its available techniques and technologies is needed. Subsequently, it is necessary to describe the implementation of non-destructive testing and the possibilities of using reverse engineering in areas of hard-to-reach places. With this knowledge in mind, it is necessary to design a prototype digitizing device usable in these areas. A suitable reverse engineering technique needs to be selected for use within this facility. With respect to the available reverse engineering techniques, it is necessary to analyze them step by step and arrive at a suitable way of implementing this technique. For this proposal, it is necessary to think with an \"outside of the box\" strategy based on the use of innovative ideas and atypical solutions, as there are currently no commercially available digitizing devices for use in the field of diagnostics of hard-to-reach places. The correct selection of available reverse engineering techniques and their use in an innovative way is crucial. In the field of digitizing hard-to-reach places, Ref. [4] proposed a 3D digitizing device based on surface scanning using multiple images at different angles and using structured light techniques without the need for calibration. In digitizing using this device, unlike conventionally structured light-based digitizing devices, there is no need to calibrate the device, after which it would be necessary to maintain the device in the same location in space.