White light LEDs become more and more important in display and lighting in various structures. Here a new modeling algorithm for phosphor-converted white light-emitting diodes (pcW-LEDs) is proposed, aiming to perform accurate simulation for color appearance, where potentially enabling optical designers to remove yellowish/bluish spots in LED lighting. The proposed modeling method is applied to simulate a pcW-LED with a hemi spherical lens. The simulation accurately predicts the blue and yellow light distribution. The model is further verified by applying a total internal reflector lens to the pcW-LED. In the midfield region, the blue and yellow light distribution exhibit large variations as the observation distance changed; this varying light pattern for both the blue and yellow lights can be accurately predicted by using the proposed model. The well-established optical model should facilitate designing a pcW-LED that features high-quality illumination and enhances color uniformity.
In this paper, we present our study in packaging efficiency for phosphor-converted white LED (pcW-LED). Then the
limit of luminous efficacy of a pcW-LED in different types of packaging is estimated. In the calculation, the EQE of the
blue die is assumed 81% and the Stokes loss is counted, we obtain the limit of luminous efficacy, which reaches 300
lm/W, when the color appearance is green-white and the corresponding CCT is between 4000K to 5000K. More
consideration for practical limit take consideration of phosphor quantum loss and geometry loss, and the limit of
luminous for CRI around 60 is around 240 lm/W, and for CRI larger than 80 is around 175 lm/W.
Linear calculation models are proposed and demonstrated to evaluate the color rendering index (CRI) performance associated with the correlated color temperature (CCT) of a white light emitting diode with two phosphors. All the three proposed models are simple and easy, and the error in predicting the CRI is within 1, while the deviation of the CCT is around 300 K and less. Such models can be useful in evaluating the chromatic performance of a specific recipe with two phosphors.
In this paper, we demonstrate a method to calculate the phosphor particle numbers and study the relationship among
phosphor particle numbers, light output and correlated color temperature (CCT) of LEDs under remote package type and
dispensing package type. We also discuss the influence of the thickness and concentration of phosphors on the
performance of LEDs. We compare the various thicknesses and concentrations to check the resultant CCT and the output
flux, where we can see that the lumen output is almost equal as the phosphor particle numbers is similar with the CCT at
6500±200 and 5000±100 K under the remote package type.
In this paper, we introduce a vision-based computer input device which has been built at the University of Georgia. The user of this system gives commands to the computer without touching any physical device. The system receives input through a CCD camera; it is PC- based and is built on top of the DOS operating system. The major components of the input device are: a monitor, an image capturing board, a CCD camera, and some software (developed by use). These are interfaced with a standard PC running under the DOS operating system.