Non-continuous distribution of printed dots for efficient illumination
Construction of speedometer. The speedometer consists of 3 main parts: meter scale plate (top layer in the image), light guide plate (LGP, second layer) and holder (bottom layer).
The letters and scale of the meter scale plate are made translucent to be illuminated from their backface. Each end of the LGP has an LED (shown in yellow) and the light emitted from the LEDs propagates inside the LGP. Note that only 2 LEDs are used to illuminate the whole speedometer.
On the backside of the LGP, thousands of small white dots are printed to control the distribution of output luminance. When the light emitted from the LED hits a dot, light scattering takes place at the point and the point is illuminated.
The automatic design starts with the uniform distribution of the dots on the whole backface of the LGP (see the left image), where the distance between the adjacent dots is constant everywhere on the surface.
Output luminance as a gray-scale image with an initial dot distribution. The uniform distribution of the dots results in non-uniform distribution of luminance on the frontface of the meter scale panel.
Output luminance as a color contour plot with an initial dot distribution. The areas near the LED are highly illuminated.
Dot distribution after automatic design. The automatic design produced an optimized distribution to uniformly illuminate the speedometer. The dots are now printed only under the letters and scale to fully utilize light energy.
The density of the dot varies depending on the position in the optimized dot distribution. In general, the dots are sparse near the LEDs and getting dense as the distance from the LEDs increases.
Output luminance as a gray-scale image after automatic design. Uniformity of the output luminance has been noticeably improved. The device efficiency of around 26% has been achieved.
Output luminance as a color contour plot after automatic design. It can be seen that the designed dot distribution efficiently guides light energy to the areas far from the light sources. The RMS value of the luminance distribution is approximately 12%.
Construction of speedometer. The speedometer consists of 3 main parts: meter scale plate (top layer in the image), light guide plate (LGP, second layer) and holder (bottom layer).
On the backside of the LGP, thousands of small white dots are printed to control the distribution of output luminance. When the light emitted from the LED hits a dot, light scattering takes place at the point and the point is illuminated.
Output luminance as a gray-scale image with an initial dot distribution. The uniform distribution of the dots results in non-uniform distribution of luminance on the frontface of the meter scale panel.
Output luminance as a color contour plot with an initial dot distribution. The areas near the LED are highly illuminated.
Dot distribution after automatic design. The automatic design produced an optimized distribution to uniformly illuminate the speedometer. The dots are now printed only under the letters and scale to fully utilize light energy.
The density of the dot varies depending on the position in the optimized dot distribution. In general, the dots are sparse near the LEDs and getting dense as the distance from the LEDs increases.
Output luminance as a gray-scale image after automatic design. Uniformity of the output luminance has been noticeably improved. The device efficiency of around 26% has been achieved.
Output luminance as a color contour plot after automatic design. It can be seen that the designed dot distribution efficiently guides light energy to the areas far from the light sources. The RMS value of the luminance distribution is approximately 12%.