| 摘要 |
PURPOSE:To shorten the dimension of the title LED in the optical axis direction only without reducing the effective emitting area from which parallel rays of light are obtained by forming the LED to have a specific inner surface and positioning an LED light source to a prescribed point. CONSTITUTION:This LED has an inner surface expressed by the formula and an LED light source is positioned to a prescribed point when polar coordinates, the pole of which is at the farther focus of an ellipse and which starts from a half-line from the focus to the vertex of a lens, refractive index of the lens, and distance between the focus and a prescribed point on the optical axis are respectively represented as r and theta, n, and a. Here, the formula of the inner surface A is expressed by r=h(theta) by using polar coordinates r and theta, the pole of which is at a focus F and which starts from a half-line Fx from the focus F to the vertex of a lens. When the optical path of the light which is emitted from a point Q and refracted in a direction R at an arbitrary point on the inner surface A is extended in the opposite direction, the extension line must pass through the focus F in order to form the virtual image of a light source at the point Q at the focus F. Therefore, the function form h(theta) of the formula r = h(theta) must be fixed so that a virtual light source condition can be met. |
