An optical apparatus for high-resolution image transfer through a protective casing , in particular for observation of an outside area, or as an inspection device for observation of an interior; comprising: at least one image-guiding element having a distal end and a proximal end ; an inverting reflection prism having an entry face and an exit face ; and a display element ; wherein the distal end of the image-guiding element has a light entry face for capturing light beams from the environment; and the proximal end of the image-guiding element has a light exit face for emitting light beams onto the entry face of the inverting reflection prism ; wherein during operation of the optical apparatus, the light beams, after having passed through the inverting reflection prism and thereby accordingly having been mirror-reflected with respect to the axis, are directed through the exit face thereof and onto the display element ; wherein the image-guiding element is mounted for non-stop rotation relative to the inverting reflection prism and/or relative to the display element over more than 360° about an axis of rotation A that is parallel to the optical axis of the inverting reflection prism , wherein the proximal end of the image-guiding element is mounted for rotation, and wherein rotation is accomplished non-electrically, in a purely mechanical manner; and wherein the surface normal of the light entry face and the surface normal of the light exit face of the image-guiding element enclose an angle μ between 5° and 175°, preferably between 20° and 160°, and most preferably between 30° and 150° between each other; wherein the optical apparatus comprises a housing having a mounting flange , wherein the housing accommodates the inverting reflection prism , and wherein the mounting flange is adapted for being coupled to an outer surface of the protective casing . at least one image-guiding element having a distal end and a proximal end ; an inverting reflection prism having an entry face and an exit face ; and a display element ; wherein the distal end of the image-guiding element has a light entry face for capturing light beams from the environment; and the proximal end of the image-guiding element has a light exit face for emitting light beams onto the entry face of the inverting reflection prism ; wherein during operation of the optical apparatus, the light beams, after having passed through the inverting reflection prism and thereby accordingly having been mirror-reflected with respect to the axis, are directed through the exit face thereof and onto the display element ; wherein the image-guiding element is mounted for non-stop rotation relative to the inverting reflection prism and/or relative to the display element over more than 360° about an axis of rotation A that is parallel to the optical axis of the inverting reflection prism , wherein the proximal end of the image-guiding element is mounted for rotation, and wherein rotation is accomplished non-electrically, in a purely mechanical manner; and wherein the surface normal of the light entry face and the surface normal of the light exit face of the image-guiding element enclose an angle μ between 5° and 175°, preferably between 20° and 160°, and most preferably between 30° and 150° between each other; wherein the optical apparatus comprises a housing having a mounting flange , wherein the housing accommodates the inverting reflection prism , and wherein the mounting flange is adapted for being coupled to an outer surface of the protective casing . <EOS>