Che-Chu Lin

Bidirectional scattering distribution function by screen imaging synthesis.

Light-emitting diodes are common light sources in modern lighting. The optical distribution of an LED package and the bidirectional scattering distribution function (BSDF) of diffusing optical components are important factors in lighting design. This paper proposes an innovative method of measuring both the optical distribution of LEDs and BSDF quickly. The proposed method uses a 2-D screen and a camera to capture the illumination on a screen, and acquires the whole-field optical distribution by synthesizing the images on the screen in different angles. This paper presents theoretical calculations and experimental results demonstrating the construction of the BSDF.

Inverse focusing inside turbid media by creating an opposite virtual objective.

Limited by the penetration depth, imaging of thick bio-tissues can be achieved only by epi-detection geometry. Applications based on forward-emitted signals or bidirectional illumination are restricted by lack of an opposite objective. A method for creating an opposite virtual objective inside thick media through phase conjugation was first proposed. Under forward illumination, the backward scattering light from the media was collected to generate a phase conjugate wave, which was sent back to the media and formed an inverse focusing light. Samples combined with a diffuser or a mouse skin were used as specimens. Inverse focusing was successfully demonstrated by applying holography-based optical phase conjugation with a BaTiO3. This result indicates the capability to create an opposite virtual objective inside live tissues. The proposed method is compatible with current coherent imaging and super-resolution imaging technologies. It creates a possible way for forward-emitted signals collection and bidirectional illumination in thick specimens.

High-performance LED luminaire for sports hall

In this paper, we present a luminaire design with anti-glare and energy-saving effects for sports hall. Compared with traditional lamps using in a badminton court, the average illuminance on the ground of the proposed LED luminaire is enhanced about 300%. Besides, the uniformity is obviously enhanced and improved. The switch-on speed of lighting in sports hall is greatly reduced from 5-10 minutes to 1 second. The simulation analysis and the corresponding experiment results are demonstrated.

Optical model of optical volume diffusion plate: polycarbonate plate doped with silicon dioxide micro particle

High-efficiency diffusers play important roles in modern optical industry. The applications include back-light of television, uniform lighting, glare suppression, lighting decoration, and so on. In this paper, we develop optical volume diffusion plate using polycarbonate (PC) plate doped with silicon dioxide (SiO2) micro particle. The scattering distribution of diffusers is an important factor in the lighting design. Commercial detectors often measure the bidirectional scattering distribution function (BSDF) by a scanning and time-consuming method. We have proposed screen imaging synthesis (SIS) system in 2012, and it can easily measure the bidirectional transmittance distribution function (BTDF). In this paper, the optimized formula is presented to correct the vignetting effect and scattering effect caused by the screen. A quasi-Lambertian screen is made to enhance precision. Finally, we combine the SIS system with the rotation controller, and a semi-automatic measuring machine is built. The SIS generation can measure BSDF of the samples precisely and easily. In order to reduce glare problems and design a luminaire with uniform light distribution, we usually use diffusers to modulate the luminaire.

Discovery of a self-pumped, phase-conjugate mirror with high speed, high image quality, and large accepted incidence area

Abstract. A study for the incidence geometry to extend the accepted incidence position is presented and demonstrated. High-speed and high-quality self-pumped phase conjugate mirrors (SPPCM) can be formed with a counter-direction incidence with respect to the master light for the Cat-SPPCM. In addition to a counter-directional Kitty-SPPCM, when the incidence position is changed, a Kitty-SPPCM with high-pass filtering and a different SPPCM similar to the Bridge-SPPCM can be found. The discovery of these three kinds of optical phase conjugators extends the accepted incidence position range and angle, helpful for applying the SPPCM in various new applications.

Optical transmittance of high-efficiency cavity with photon recycling

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.

High thermal stable and low resistance contacts to p-GaN for thin-GaN LED

In this work, we investigate the optical and electrical properties of inserting a Ni thin barrier between contact layer, NiO-Au, and reflective layer, Al after sequent elevated annealing in air ambient. The reflectivity of NiO-Au/Ni/Al p-GaN contact configurations is 61% in 470nm which is 10% higher than NiO-Au/Al p-GaN contact configurations, after 500°C annealing. By inserting a Ni barrier layer, the specific contact resistance of the NiO-Au/Ni/Al was maintained on the order of 10-2 Ω-cm2, up to an annealing temperature of 500°C. The XPS results confirmed the function of the Ni barrier layer, and it shows relatively low atomic level of Al was detected in the GaN epi-layer. It was found that both the electrical and optical characteristics of NiO-Au/Ni/Al p-GaN contacts exhibited good thermal stability. This high thermal stable P-GaN enables the fabrication of thin-GaN LED device.