Headlamp capsule with debris protection

An illumination unit comprising:

• an electric lamp having a vessel with a vessel wall defining an enclosed volume, a light source positioned in the enclosed volume having two electric leads extending through a press sealed end of the vessel, the press sealed end and electric leads being configured as a base for axial insertion in a socket for mechanical and electrical coupling of the electric lamp;
• an envelope having an envelope wall with a first side, and a second side, the envelope wall being formed with an envelope aperture extending from the first side to the second side, and having a circumferential lip extending around the envelope aperture adjacent the second side, the electric lamp being positioned in the envelope aperture with the press sealed end exposed adjacent the second side for axial coupling;
• and
• a fastener having the form of a plate with an internal wall defining a plate passage, the internal wall including a latch, the press sealed end being positioned in the plate passage, and securely coupled by the latch to the fastener to retain the vessel in relation to the fastener, the fastener further having a radial region extending transversely away from the press sealed end and adjacent the second side, and the fastener further having a peripheral coupling securely coupled to the envelope circumferentially along the lip to retain the envelope in relation to the fastener.