A phase unwrapping method using the phase-encoded algorithm for phase-shifting projected fringe profilometry is presented. There is no need to take additional projections for phase unwrapping. The patterns used to perform the phase-extraction can be employed for unwrapping directly.
Antifungal effects of ultraviolet C (UV-C) irradiation have been considered a potential solution to reduce the severity of black spots on postharvest fruits. In this work, a 30 × 30 × 30 cm system was made based on UV-C light-emitting diodes (LEDs) to apply in reducing disease symptoms for bananas which could be used in industrial conveyor belts. The UV-C irradiance monitoring was carefully carried out for several sections at various box heights in simulation and measurement. The findings experienced a dominating range of 6 to 9 W/m2 in the central sections. Regarding in vivo conditions, the observation after a week from experiment showed that the disease symptoms on the UVC-treated banana peel, which was exposed under UV-C light around 5 s, dramatically decreased compared to a natural banana. Consequently, the UV-C dose range is proposed from 0.030 to 0.045 kJ/m2 with minimum damage in terms of sensory properties. Owing to the flexible shape and short exposure time, the system promises to provide many potential applications to prolong the quality of bananas.
In this paper, we propose an innovative adaptive automotive headlamp design that incorporates a volume holographic optical element (VHOE) as a beam splitter. The VHOE is recorded with an infrared divergent spherical wave, allowing for the efficient combination of both time-of-flight (ToF) laser beam and miniLED imaging automotive headlamp. By exploiting the Bragg selectivity property of the VHOE, only the ToF light is affected while the imaging headlamp light passes through unaffected. This facilitates the adaptation of the automotive headlamp to different lighting conditions, providing enhanced visibility and safety for drivers. The ToF laser beam provides accurate depth information, while the miniLED can create a high-contrast cut-off line. The VHOE beam splitter enables the effective combination of these two lighting sources, ensuring that each is used to its full potential. Our design offers a promising solution for adaptive automotive headlamp systems that could potentially improve driver safety on the road.
Multi-level phase encoding 2D signal is very important in the application of holographic data storage. However, conventional phase-shifting interferometry using addition reference beam suffers from the fluctuation in the phase stability, the phase-shifting, and the wavefront error of the reference beam. This paper proposes and demonstrates a pre-integral DFGSI with the utilization of a built-in phase-shifting function, to retrieve multi-level phase signals. This type of new interferometer will be helpful in optical testing in dynamic circumstances with a common path and without an additional reference wave.
Conventional measurement of bidirectional scattering distribution function (BSDF) and total transmittance (TT) is a serious topic. We have proposed a screen image synthesis (SIS) BSDF meter that provides high-speed and precise measurement. However, the measurement of TT using integrating sphere cannot offer a precise measurement. Therefore, we propose a calibration method that using SIS BSDF meter, responsivity of the integration sphere photometer and integration transmission power. It brings us not only precise BSDF function but precise TT measurement.
We perform the mid-field model of a UV-C LED with an arranged wavelength of around 275 nm by comparing the 2-dimension (2-D) gray-level image captured by a monochromatic CMOS and the corresponding simulated irradiance pattern. Owing to UV-C light, we propose using a fluorescent film to absorb UV-C light and re-emit light at a longer wavelength so that the 2-D gray level image can be captured. The calibration to approach the corrected gray level of image is presented. Consequently, we obtain the precise mid-field light source model. Moreover, the model is also applied for dome lens design and then compares the optical behavior with fabricated samples in measurement to evaluate its validity.
In this study, we use 30 mini-LED arrays as the light source of the bike lamp. A single reflector with 68 segments to project vehicle low beam and high beam with the use of a GaN-based mini-LED matrix, which is a 30 LED dies array. The design of the reflector is based on light field technology in considering etendue from the light source across the segments. The group of the segments with smaller etendue from the LED dies in the bottom 2 rows are used to project low beams. When the other LED dies are turned on, the reflector will project light upward and form the high beam. The selection of the turn-on LED dies in the mini-LED matrix can adjust the width of the illumination pattern so that an adaptive low/high beam can be performed.
We introduce a current development in optical design for vehicle forward lighting based on solid-state lighting, in particular, phosphor-converted white LEDs. The vehicles include bicycles, bikes, and automobiles. Although the requirements regulating different vehicles are different, the low beam always requires a high-contrast cutoff line. Three optical design approaches are discussed; these include a projection lens incorporated with a baffle or beam shaper, multisegment reflectors, and complex lenses. A new design approach called light field management technology for the multisegment reflector is introduced. In addition, the possible related manufacturing errors and the robustness of different optical approaches are analyzed. Finally, we introduce three approaches to adaptive forward lighting that provide a driver with brighter and clearer vision without inducing glare to people on the roadway. The application of video projection technology to roadway illumination could be a trend of vehicle forward lighting based on solid-state lighting.
We discuss the trade-off caused by the system parameters, and the performance degradation caused by the angular momentum of the rotational motor for shifting multiplexing. We also propose applying phase-integrated double-frequency grating shearing interferometer (PI-DFGSI) to makes the reading with moving disc being possible, and thus improves the system performance.
We propose a volume holographic optical element (VHOE) used as an objective turret in a lensless digital holographic microscope. It also served as a reference wave guide to reduce the volume of the system. For further optimization of resolution performance, it used a spherical wave in the object light of the VHOE, which served as the reference light of the microscope. Another sheared spherical wave was used to illuminate the sample. The optimized VHOE increased the spatial resolution of the record signal effectively. Furthermore, the change of spherical wave distance leads to the change of imaging magnification.
A design scheme for an aspherical lens including two step processes is proposed and demonstrated to direct appropriate flux to the expected target illumination. The first-step design is based on a point source and the surface geometry is determined. The flux deviation between the design and target illumination becomes the factor in the optimization process, and the angular flux compensation is done to adjust the light pattern. Finally, the experimental result shows that high similarity between the target and the measurement is observed and full width at half maximum angle error is within 3%, which are both better than those in the aspherical lens design based a point source and a real light-emitting diode without optimization by flux compensation.
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.
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 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.
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 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 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 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.
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