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Gauge Repeatability and Reproducibility (Gauge R&R , G.R.R) is of great importance for checking measurement system precision, traditional average-range G.R.R test involves equipment variation (EV) and appraiser variation (AV), which is not appropriate for current modern automatic measurement tools. In this paper, we designed different test experiments on film thickness (THK) and critical dimension (CD) metrology and statistically analyzed different variances impact on G.R.R. From THK G.R.R experiment ANOVA analysis, it can be seen that time interval and measurement process have no significant effect on G.R.R result, and the equipment repeatability variation is the major variation source. From CD G.R.R experiment ANOVA analysis, it can be checked that, G.R.R has significant time dependence of data collection due to test wafer changed. As a conclusion, not only appraiser’s variation but also time interval has less impact on metrology G.R.R of semiconductor wafer manufacturing process.

A new optical design of a confocal double-reflector, for white LED lighting, performing uniform illumination with a specific projection angle has been presented and demonstrated. In addition, the anti-glare design with double-reflector prevents direct view of the LED, and the measured veiling luminance is much lower than that in general LED-based projection lamps.

A novel light luminaire is proposed and experimentally analyzed, which efficiently mixes and projects the tunable light from red, green and blue (RGB) light-emitting diodes (LEDs). Simultaneous light collimation and color mixing is a challenging task because most collimators separate colors, and most color mixers spread the light beam. We performed an experimental study to find a balance between optical efficiency and color uniformity by changing light recycling and color mixing.

A planar-exit lighting surface is not only used in the luminaires but also useful in the display backlights and other illumination systems. Most planar-exit lighting surfaces are made by edge-lit with line light source or 1-D LED array. If it is not edge-lit type, the light source can be two-dimensional, but a cavity is required. In this paper, a high-efficiency cavity providing extremely high energy transmittance with photon recycling is reported and demonstrated. The cavity contains a diffuser and the high reflectivity surfaces. The optical efficiency of the cavity is calculated by a formula with considering photon recycling. Furthermore, various kinds of diffusers are applied to change the optical transmittance as well as the light pattern. When the reflectivity of the inner wall of the lighting cavity is about 96 %, the optical efficiency of the cavity is higher than 90 % with several diffusers. The experimental measurement as well as the calculation is demonstrated in the paper.

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 propose and demonstrate a novel design to make color mixing and projection of RGB LEDs. The optical elements include a high reflective light pipe, a volume scattering diffuser and a TIR lens. The system optical efficiency is around 46 % while the color is well mixing for the cases at the CCTs of 6500K, 4500K and 3000K.

In this paper, based on Monte Carlo ray tracing we simulate light extraction efficiency and directionality of the light pattern of GaN LEDs implanted with micro-pyramid structure with or without lens encapsulation. We have shown that micro-pyramid structures at some specific slanted angles in the LEDs are useful to increase effective flux utilization through enhancement of both the directionality and light extraction efficiency.

A single-chip white light LED is commonly modeled by considering the phosphor coating as a homogeneous Lambertian light source. However, this approach leads to an incorrect optical simulation of phosphor-coated multi-chip LEDs due to the presence of a previously unreported spatial distribution of emission spots across the phosphor layer. We introduce "weighting" factors based on position-dependent light strength across the phosphor surface in order to improve the model accuracy. Following the modeling algorithm in the mid-field region, we have built up a precise and practical optical model by using Monte Carlo ray tracing and weighting factors. We measure the LED radiation distribution at several representative distances to test the model performance. In all cases, the accuracy is higher than 99.5% in normalized cross correlation between the simulated pattern and experimental measurement.

Light extraction analysis of GaN-based light-emitting diodes (LEDs) with Monte Carlo ray tracing is presented. To obtain high light extraction efficiency, periodic structures introduced on the top surface and/or on the substrate of various types of LED are simulated, including wire bonding, flip chip and Thin GaN. Micro pyramid array with an apex angle from 20° to 70° is shown to effectively improve the light extraction efficiency. In addition, for an LED encapsulated within an epoxy lens, the patterned substrate with pyramid array is found to be a more effective way to increase light extraction efficiency than the surface texture.

In this paper, as to our best knowledge, we propose and demonstrate the first precise phosphor modeling scheme to simulate the chromatic performance of white LEDs with silicate phosphors. The phosphor model is useful to accurately simulate the power ratio of the blue and yellow lights emitted by the white LEDs and is important in white LED package.

A direct or bottom LED backlight is a key concept in large area LCD displays because it does not use a light guide, is flat, and is easy to assemble. In this paper, a method of luminance management for a bottom LED backlight is proposed and demonstrated. We analytically calculate both the power consumption and brightness uniformity in function of: screen brightness, screen size, backlight thickness, transmittance of the LCD panel, reflective cavity efficiency, gain and cone angle of enhancement films, LED array configuration, and the average luminous flux and radiation pattern of a single LED. Moreover, a 42-inch LCD television with this backlight design approach is made and demonstrated. The bottom backlight incorporates an array of RGGB 4-in-1 multi-chip LEDs within a highly reflective box behind a diffuser and a dual brightness enhancement film. We predict with an accuracy of 94% the brightness uniformity and with 96% the luminance level.

A single-chip white light LED is commonly modeled by considering the phosphor coating as a homogeneous Lambertian light source. However, this approach leads to an incorrect optical simulation of phosphor-coated multi-chip LEDs due to the presence of a previously unreported spatial distribution of emission spots across the phosphor layer. We introduce "weighting" factors based on position-dependent light strength across the phosphor surface in order to improve the model accuracy. Following the modeling algorithm in the mid-field region, we have built up a precise and practical optical model by using Monte Carlo ray tracing and weighting factors. We measure the LED radiation distribution at several representative distances to test the model performance. In all cases, the accuracy is higher than 99.5% in normalized cross correlation between the simulated pattern and experimental measurement.

Light extraction efficiency of GaN-based LEDs as functions of chip dimensions, absorption coefficients and package for both conventional one and Thin-GaN are analyzed based on Monte-Carlo ray tracing.

This paper demonstrates a novel retro-reflective dome that enhances the directionality of a light emitting diode (LED) by recycling photons reflected by a textured LED die surface. A simulation model is developed to describe both the photon recycling process within the dome and the role of specific pyramid patterns on the top surface of the LED die. Advanced simulations showed that a perfectly polished surface with 100% reflectivity potentially enhances the directionality of the dome by 340%, 250%, and 240% using reflective domes with 10°, 20°, and 30° light cones, respectively. In the experiment, the directionality of the domes exhibiting surface imperfections is enhanced by approximately 160%, 150%, and 130% using 10°, 20°, and 30° light cones, respectively. By incorporating a textured top surface on the LED die, the proposed dome effectively increases the directionality of the LED light source.

A novel light luminaire is proposed and experimentally analyzed, which efficiently mixes and projects the tunable light from red, green and blue (RGB) light-emitting diodes (LEDs). Simultaneous light collimation and color mixing is a challenging task because most collimators separate colors, and most color mixers spread the light beam. Our method is simple and compact; it only uses a short light pipe, a thin diffuser, and a total internal reflection lens. We performed an experimental study to find a balance between optical efficiency and color uniformity by changing light recycling and color mixing.

A lighting cavity is a reflecting box with light sources inside. Its exit side is covered with a diffuser plate to mix and distribute light, which addresses a key issue of luminaires, display backlights, and other illumination systems. We derive a simple but precise formula for the optical efficiency of diffuser plates attached to a light cavity. We overcome the complexity of the scattering theory and the difficulty of the multiple calculations involved, by carrying out the calculation with a single ray of light that statistically represents all the scattered rays. We constructed and tested several optical cavities using light-emitting diodes, bulk-scattering diffusers, white scatter sheets, and silver coatings. All measurements are in good agreement with predictions from our optical model.

Versatility in the design of optical systems is one of the key features of light-emitting diodes (LEDs) that has attracted considerable attention. In the analysis of systems using LEDs, it is useful to know if the distance is far enough from the LED to allow the radiation pattern to be simulated by the point source approach. We propose three far-zone conditions for LED light modeling: the far-field distance, and for practical purposes the quasi far-field and minimum far-field distances. Different types of LEDs have different far-field ranges. We analyze these differences by modulating key parameters like geometrical structure of encapsulating lens, chip size, chip shape, chip position, and package errors. We find that far-field region considerably depends more on the shape of both lens and chip than all other parameters.

— A method of calculating the luminance and luminance uniformity of a bottom LED backlight is proposed and demonstrated. Both the power consumption and brightness uniformity as a function of screen brightness, screen size, backlight thickness, transmittance of the LCD panel, reflective cavity efficiency, gain, cone angle of the enhancement films, LED array configuration, and the average luminous flux, radiation pattern, and input power of individual LEDs. Moreover, a 42-in. LCD TV using this backlight design approach was fabricated. The bottom backlight incorporates an array of RGGB 4-in-1 multi-chip LEDs within a highly reflective box behind a diffuser and a dual brightness-enhancement film. The brightness uniformity can be predicted within an accuracy of 94% and the luminance level within an accuracy of 96%.