Document ID: chunk:federal_register_of_legislation:F2016C00338:front:0:p10
Version: federal_register_of_legislation:F2016C00338
Segment Type: other
Provision Reference: 
Character Range: 29543–32350

screens situated in this plane, each allowing only 98 % of the total luminous intensity of the light to persist in the direction of the axis of reference. To determine the lower, upper and lateral limits of the illuminating surface, only screens with horizontal or vertical edges shall be used;

       2 7.3. "Illuminating surface of a retro-reflector" (para. 2.5.13.) means the orthogonal projection of a retro-reflector in a plane perpendicular to its axis of reference and delimited by planes continuous to the outermost parts of the retro-reflector's optical system and parallel to that axis. For the purposes of determining the lower, upper and lateral edges of the device, only horizontal and vertical planes shall be considered;

       2.8.  The "apparent surface" for a defined direction of observation means, at the request of the manufacturer or his duly accredited representative, the orthogonal projection of:

        either the boundary of the illuminating surface projected on the exterior surface of the lens (a-b),

        or the light-emitting surface (c-d), in a plane perpendicular to the direction of observation and tangential to the most exterior point of the lens (see annex 3 to this Regulation);

       2.9.  "axis of reference" (or "reference axis") means the characteristic axis of the lamp determined by the manufacturer (of the lamp) for use as the direction of reference (H = 0 degrees, V = 0 degrees) for angles of field for photometric measurements and for installing the lamp on the vehicle;

       2.10.  "centre of reference" means the intersection of the axis of reference with the exterior light-emitting surface; it is specified by the manufacturer of the lamp;

       2.11. "Angles of geometric visibility" means the angles which determine the field of the minimum solid angle in which the apparent surface of the lamp must be visible. That field of the solid angle is determined by the segments of the sphere of which the centre coincides with the centre of reference of the lamp and the equator is parallel with the ground. These segments are determined in relation to the axis of reference. The horizontal angles beta, correspond to the longitude and the vertical angles alpha to the latitude. There must be no obstacle on the inside of the angles of geometric visibility to the propagation of light from any part of the apparent surface of the lamp observed from infinity. If measurements are taken closer to the lamp, the direction of observation must be shifted parallel to achieve the same accuracy.

        On the inside of the angles of geometric visibility no account is taken of obstacles, if they were already presented when the lamp was type-approved.

        If, when the lamp is installed, any part of the apparent surface of the lamp is hidden