The lamp is the only one at present fully meeting the very demanding pattern of light required by AU 155:1973. These requirements could not be met by a glass lens because it cannot be moulded to the precision required by the sharp cut off of the beam. As high production rates would be needed as soon as development was complete, it was decided to start manufacture of an optimum six-impression production mould plus a single impression experimental mould, developments only being transferred to the production mould after thorough testing. It was realised that nearly all the light output would need to be directed in the required distribution. The first stage of the design of the new plastic headlamp was to provide a clear annular area, and a good riding beam. The central area had two groups of vertical prisms to refract and reflect the direct light to the sides, and a group of horizontal prisms providing sharp vertical cut off. Photometric tests showed that the light distribution provided too much contrast between the centre and wings. Subsequent modifications described used frosting at the edge of the lens, vertical fluting and a diffuser to produce a satisfactory distribution. /TRRL/

  • Corporate Authors:

    Illuminating Engineering Society

    York House, 199 Westminster Bridge Road
    London SE1 7UN,   England 
  • Authors:
    • Pasco, I K
  • Publication Date: 1977-5-6


  • English

Media Info

  • Features: Figures; Photos;
  • Pagination: p. 132-133
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00163963
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: Analytic
  • Files: ITRD, TRIS
  • Created Date: Dec 8 1977 12:00AM