LED Illuminated Logo
SMA has been approached several times to illuminate a “logo” or some specific shape in a very thin (~1/8”) badge device. The requirement has usually been to be able to change the color of the shape as a result of a battery-powered circuit and switch controlling a very small 3-color LED. In each case, we designed an underlying structure to distribute the light and couple it out of the structure so that it could be viewed from a wide range of viewing angles.
In the case of the hand-shaped logo to the right, the image is a simulated image without the opaque plastic “mask” overlayed that would ultimately occlude the modest leakage from the LED.
In the case of the triangular shape, the images are of a prototype device under test. Amber light was achieved by mixing the red and the green LEDs. The physical separation of these die in the LED in combination with the extremely small overall height allowed for the structure contributed to the imperfect distribution and mixing of the two wavelengths. Brightness was ultimately adjusted to match the other two colors by adjusting the current levels of the two LEDs in appropriate proportions. (Streaking is simply an artifact of the photographic image and was not visible.)