| 摘要 |
PURPOSE:To prevent disturbance of light distribution due to a lens by providing a transparent body, which has a curved surface inclined to the optical axis of a lamp body, with a lens by which the light incident in parallel with the optical axis of the transparent body is emitted in parallel with this optical axis. CONSTITUTION:Coordinates (x, y) of a point S3 which allows the light to emit from an exit point S2 in parallel with an optical axis X-X' as shown by an arrow in the figure are expressed as follows: y=tan(alpha-beta){x-Rcosalpha}+Rsinalpha, and sinbeta=sinalpha/n, and (dy/dx)=-1/tanalpha [(n) is the refractive index of the transparent body constituting a lens 3']. For example, a radius R of the outside circumferential face of said transparent body and its refractive index are set to 30mm. and 1.5 respectively, and alpha and beta are eliminated from said formulas to obtain a differential equation f(x, y, dy/dx)=0, and an answer is obtained by a computer. The shape of an inside circumferential face 3b' is obtained in this method to prevent disturbance of light distribution due to the lens. |
