We proposed a novel structure to perform photon recycling for a double-light-source illumination system pumped by a laser. In the design, two kinds of phosphor are located at the two focus of an elliptical reflective surface separately, after the phosphor on the first focus pumped by laser, the backward scattering light will refocus at the other phosphor layer at the second focus. The absorption spectrum of the second phosphor should fit that of the emission light by the first phosphor. When the emission spectrum covers red light, the whole system is a double-light-source module.
In this paper, an efficient lighting design for indoor sport field is presented. The average illuminance for the indoor sport field with eight playing courts can be achieve to 500 lx at a 11.2 m of the lamp's mounting height. Besides, because of specific arrangement of luminaires, the proposed lighting design can effectively reduced the glare effect and provide a comfortable illumination to players.
Bidirectional scattering distribution function (BSDF) represents the scattered light distribution in forward and backward directions. BSDF is an important function in precise lighting design, because surface scattering is difficult to determine and including it in simulations. However, to measure a whole field BSDF is time consuming, as it can take as long as a day. In this paper, we propose and demonstrate a new way to measure BSDF. We utilize a screen that is illuminated by the scattered light, and a camera that captures the image on the screen. A complex calibration between the grey level of the camera and intensity is performed to make sure the measurement is valid. Through continuously imaging the screen for various scattered light distributions, an image fusion is performed to present the final BSDF. We call this instrument as screen image synthesis (SIS) BSDF meter. In this paper, two generations of SIS BSDF meter was developed, and is shown in details.
3D-image technologies produce RGBD images use 2D RGB image combing with depth image. The most popular depth imaging methods including structure light, time-of-flight, and stereoscopic image. Since no point cloud detection method can prevent depth information loss, the complement methods is therefore important. Therefore, we proposed depth information complement method, which use a novel iterative low-pass pervasion method to apply depth image pervasion. We make two experiments to demonstrate the idea. The first experiment induces strong IR noise to destroy parts of the depth image. Then we successfully complement the depth image by the proposed method. The second experiment demonstrates the complement performance of iterative low-pass pervasion method and shows good Accuracy and Precision.
A novel method to stabilize the correlated color temperature in pc-WLEDs from their initial turn-on state to thermal equilibrium is proposed and demonstrated. Under the normal operation condition, it can stabilize the CCT of a pc-WLED by the positive matching of the blue LED peak wavelength to the phosphor excitation spectrum. In the experiments, the CCT variation could be as small as from 7 K to 83 K in different cases. In addition, this study also proposed a practical approach for measuring phosphor temperature in an operating pc- WLED using a noncontact, instant detection method to remotely monitor the emission spectrum. The approach is also independent of the peak wavelength of pumping lights, the concentration and thickness of phosphor, and correlated color temperatures. Firstly, a novel method to stabilize the correlated color temperature in pc-WLEDs from their initial turn-on state to thermal equilibrium is proposed and demonstrated. In the experiments, the CCT variation could be as small as from 7 K to 83 K in different cases. Secondly, this study also proposed a practical approach for measuring phosphor temperature in an operating pc-WLED using a noncontact, instant detection method. The approach is also independent of the peak wavelength of pumping lights, the concentration and thickness of phosphor, and correlated color temperatures.
This paper presents a new pattern design for encoding structured light for scanning 3D surface and the decoding process. The basic unit of the pattern is a code-block that contains one central label and eight square-shaped primitives that provide two functions: code-block indexing and point-positions for triangulating. The square-shaped primitive has one notch in a different position to represent 8 digit numbers, which are easily to convert label to number for indexing codeblock. One primitive also contributes five point-positions, centroid and four extreme, for triangulating and estimating 3D information. The design of code-block has eight 8-bit numbers allowing a higher error-tolerant and providing better resolution in 3D reconstruction. Experiment shows that the proposed pattern is suitable for indoor mapping and large scene scanning.
Two optical designs for marine beacon based on Direct In-line Package (DIP) LED is proposed and demonstrated. The luminous intensity of the marine beacon using DIP LED can achieve to the IALA recommendation’s requirement of 5 nautical miles. The measurement of color coordinates can also fit the IALA recommendation’s requirement. By the surface-structured TIR lens, we successfully keep the divergence angle to 68 degrees in the horizontal direction and converge to 8 degrees in the vertical direction.
A fringe projection method based on the phase-shifting technique for 3D shape measurements is presented. Phase extraction is performed by the phase-shifting technique, while unwrapping is discerned by the phase-encoded patterns. There is no need to take additional projections for phase unwrapping. The fringe patterns used for phase extraction can be directly utilized for unwrapping. Experiments show that absolute phases could be obtained with high reliability.
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.
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.
We record a reflection volume hologram with two plane waves in lithium niobate. By heating one corner of the LiNbO3 crystal, it will cause an inhomogeneous temperature distribution in the crystal. The thermal expansion results in small
slight deformation of the volume hologram and then decreases the intensity of diffraction light. We also use the model of
volume hologram being an integrator of the lights emitted from elementary light sources (VOHIL) to calculate the
diffracted field for the linear thermal expansion. The results of experiment and simulation are both shown that the
intensity of diffraction light decreases from the heating corner of the crystal. The change of intensity of diffraction light
is predicted successfully with the model of VOHIL for the thermal expansion.
We summarize our theoretical study of the collinear volume holographic storage system. Simple formulas with direct physical concepts are developed under paraxial condition with scalar diffraction theory and VOHIL model, which are much helpful in figuring out the characteristics on point spread function (PSF) and the shift selectivity. Accordingly, effective system design is possible.
We use a paraxial approximating solution to calculate the point spread function of the collinear holographic storage system and show that the point spread function can be dramatically enhanced by the reference pattern with random binary phase modulation or random phase modulation.
We propose a paraxial solution for pixel shift selectivity, which can simulate the pixel shift selectivity in two
dimensions and in wide range easily. Thus, the effect of different reference patterns can be calculated in detail. From the
simulation result, we conclude that the pixel shift selectivity get worse for amplitude modulation reference patterns.
Making no modulation is the best reference pattern for pixel shift selectivity, however the point spread function will be
worst in this case. To get an optimum system in both pixel shift selectivity and point spread function, the reference
pattern with phase modulation will be the best choice.