u2061 u03b8 n 2 sin 2 u2061 u03b8 1 y a u2062 u2062 tan u2061 u03b8 a 1 n 1 tan 2 u2061 u03b8 n u2062 1 sin 2 u2061 u03b8 n 2 sin 2 u2061 u03b8 b u2061 n 1 n u2062 1 sin 2 u2061 u03b8 n 2 sin 2 u2061 u03b8 1 a u2062 sin u2061 u03b8 n 2 sin 2 u2061 u03b8 3 the expression given in equation 3 leads straightforwardly to the curved output lens surface in fig4 which substantially collimates the light emerging from the laser diode aperture the preferred lens design with an internally reflecting surface can be generated using a method of images construction as described hereinafter in fig5 region 58 and region 60 in fig5 are sections of a cylindrical lens 54 that are used for demonstrating the method of images construction i e rays passing through a simulated internally reflective surface 56 is shown in region 58 to illustrate how they need to be reflected from region 60 thus the internally reflecting surface represented by line 56 preferably a flat surface in fig5 is used to reflect optical rays from region 58 below surface 56 so as to be above internally reflecting surface 56 i e region 60 fig6 represents a cylindrical microlens 70 design for a laser diode array such as for example a simm package without an internally reflecting surface using the method of images construction as discussed herein before the components comprise a region 76 above a simulated internally reflective surface 72 a region 74 below the simulated internally reflective surface 72 and a surface 78 to collimate rays from an emission source not shown thus the reflecting surface 72.