Papers by ching-cherng sun
Optics Continuum
A method was developed to investigate the reflected properties of LED and HPS-lighted wet roads u... more A method was developed to investigate the reflected properties of LED and HPS-lighted wet roads using on-site measurement of luminance images. An ILMD was used to obtain high observation angles by placing it at a close distance to the ROI. The luminance images were analyzed to derive a distribution of reflected luminance as a function of deviation, incidence, and observation angles. Furthermore, an investigation of the reflected characteristics of a dry asphalt road illuminated by LED lighting was conducted, employing on-site measurements of the images of luminance and the distribution of illuminance. The results provide valuable insights for designing lighting systems and mitigating the adverse effects of glare and specular reflection on road safety.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 1, 2021
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Distributed under a Creative Commons Attribution-NonCommercial-NoDerivatives| 4.0 International License
Current Developments in Lens Design and Optical Engineering XXIII
Current Developments in Lens Design and Optical Engineering XXIII
Optics Continuum
The measurement of bidirectional scattering distribution function (BSDF) and total transmittance ... more The measurement of bidirectional scattering distribution function (BSDF) and total transmittance (TT) is a complicated issue. 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 uses SIS BSDF meter and responsivity of the integrating sphere. It brings us not only precise BSDF function but precise TT measurement.
We performed the simulation and experiment to investigate the influence of Zirconium dioxide (Zir... more We performed the simulation and experiment to investigate the influence of Zirconium dioxide (Zirconia, ZrO2) particles on the optical properties of phosphor converted white LED (pcW-LED). An efficient optical model was developed and applied to the incorporation diffuse particle of ZrO2 into a hemisphere package containing YAG phosphors. The optical properties (chromaticity, packaging efficiency) were estimated as a function of phosphor and ZrO2 particles, through the calculation of effective radius, refractive index, and absorption and conversion efficiency, in a range of correlated color temperature 4500 K to 6500 K. In the same way, the amount of phosphor and ZrO2 can be calculated accurately to obtain a targeted optical property in a hemisphere LED design. Especially, the angular distribution of CCT was also diminished, and even almost inexistent for low CCT design. In addition, the adding of ZrO2 particles allows clearly decreasing the amount of phosphor for an identical target...
Bullet-shaped LEDs are commonly used in self-luminous traffic signs as LED-dotted matrices due to... more Bullet-shaped LEDs are commonly used in self-luminous traffic signs as LED-dotted matrices due to their low cost, simplicity, robustness, and ease of installation. We proposed a simple low-cost method that creates a model suitable for the high manufacturing tolerance found in bullet-shaped LEDs. The method starts from measuring multiple one-dimensional angular intensity patterns at interested distances from multiple LEDs to form a database, including distances at 10, 15, 20, 25, 35, 50, and 100 mm. Their normalized cross-correlations are then calculated to find the batch that has the most similarity and base our model off that batch. Finally, we validate the model via Monte Carlo simulations in comparison to the original one-dimensional angular intensity patterns in the database. The platform demonstrated to obtain an average of 99% in normalized cross correlation between different batches of the same model LED, and a model of that LED is currently under development.
OSA Continuum, 2021
This paper presents the mid-field model for an ultraviolet C light emitting diode (UVC LED) of wa... more This paper presents the mid-field model for an ultraviolet C light emitting diode (UVC LED) of wavelength around 275±5 nm by comparison of the 2-dimension (2-D) gray-level image captured from a mono-CMOS sensor and simulated irradiance pattern. Because of UVC light, we propose using a fluorescent film to absorb UVC light and re-emit visible light so that the 2-D image could be captured. The analysis and calibration to obtain accurate gray level of image are performed. Finally, we achieve the mid-field model with high accuracy. Furthermore, this model is also applied for dome lens design and then compares the performance with fabricated samples in measurement to expertise its validity.
OSA Continuum, 2021
In this paper, we propose an imaging system for quick detection of high-dynamic illumination with... more In this paper, we propose an imaging system for quick detection of high-dynamic illumination with a high-contrast cutoff line. A digital camera is used to capture the image of the light pattern from a vehicle headlamp. After having image processing and calibration, we can accurately obtain the illuminance of the measurement plane while different exposure times are used to increase the dynamic range of the system measurement. Two representative regulations are mainly discussed, one is K-mark and the other is ECE R113 Class B. Results show that the measurement errors of our imaging system are within ±5% when the values are more than 2 lx, and have a difference of 0.1 lx when the values are less than 2 lx.
Optical Engineering, 2021
Abstract. A design scheme for an aspherical lens including two step processes is proposed and dem... more Abstract. 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.
Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications XV, 2021
We discuss the trade-off caused by the system parameters, and the performance degradation caused ... more 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.
Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications XV, 2021
We propose a volume holographic optical element (VHOE) used as an objective turret in a lensless ... more 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.
Holograms - Recording Materials and Applications, 2011
only the transparent grating needs to be considered. As shown in Fig. 1-3, the mirror on the back... more only the transparent grating needs to be considered. As shown in Fig. 1-3, the mirror on the back surface of the holographic disk in Fig. 1-2 is replaced by a disc of double-thickness in a modeled transmission algorithm. The two lenses form a 4f system: SLM locates at the front focal plane of the first lens, the disc is located at the back focal plane of the first lens, and the CCD is placed at the back focal plane of the second lens. Fig. 1-3(a) shows the effective model of the writing process. The reference beams from the outer ring of the SLM and the signal beams from the inner circle of the SLM are transformed to frequency domain by the lens and then recorded by the lens. Fig. 1-3(b) shows the effective model of the reading process. Only the light from outer ring can pass through as a reading beam, which is transformed by the lens into frequency domain. Subsequently, the diffracted signal beam and the un-diffracted reading beam are transformed together by the second lens into spatial domain. The aperture blocks the un-diffracted reading beam and leaves only the diffracted signal beam to image on the CCD.
Scientific Reports
The screen image synthesis (SIS) meter was originally proposed as a high-speed measurement tool, ... more The screen image synthesis (SIS) meter was originally proposed as a high-speed measurement tool, which fused the measured data from multiple sample-rotational angles to produce a whole-field measurement result. However, it suffered from stray light noise and lacked the capability of spectrum measurement. In this study, we propose an SIS system embedded with a snapshot hyperspectral technology, which was based on a dispersion image of the sparse sampling screen (SSS). When a photo was captured, it was transformed and calibrated to hyperspectral data at a specific sample-rotational angle. After the hyperspectral data in all sample-rotational angles were captured, an SIS image-fusion process was then applied to get the whole field hyperspectral data. By applying SSS to the SIS meter, we not only create a screen image synthesis hyperspectral meter but also effectively address the issue of stray-light noise. In the experiment, we analyze its correctness by comparing the hyperspectral val...
Scientific Reports
A phenomenon known as "blue-light leakage" caused by overheating pcW-LEDs has recently ... more A phenomenon known as "blue-light leakage" caused by overheating pcW-LEDs has recently been identified, and it poses a risk to users. This study focuses on investigating and optimizing a solution to address this issue. To tackle the problem of overheating and blue light leakage, we explored the application of a specific thermochromic material called crystal nano cellulose (CNC). We introduced CNC inside the epoxy lens of white LEDs. Importantly, under standard conditions, CNC has a negligible impact on the optical properties of the output white light. However, when overheating conditions arise, leading to blue light leakage, the temperature increase triggers a darkening effect in CNC. This thermochromic behavior of CNC allows it to strongly absorb the blue light, resulting in a significant suppression of the output luminous flux. As a result, the lamp dims, which not only prevents the user's eyes from being exposed to harmful bluish light but also serves as an indicato...
Scientific Reports
In this study, we propose a novel high-concentration photovoltaic (HCPV) cell by considering both... more In this study, we propose a novel high-concentration photovoltaic (HCPV) cell by considering both the light leakage characteristics of the Fresnel-lens-based solar cell modules and the performance issues arising from cloud shading in practical use. We use our self-constructed systems to conduct field measurements for up to half a year under various environmental conditions. According to the acquired results, it was surprising to know that in the area other than the focusing area, the so-called light leakage region, there always bears illuminance of about 20,000–40,000 lx whether it is a sunny day or a cloudy day with different cloud conditions. Such an interesting result is caused by the light scattering of the clouds and the inherent leakage characteristic of a Fresnel lens. To prove this important finding, we simulated the illuminance of the Fresnel lens structure used in the measurement with apertures of different sizes to determine the detected area. In the laboratory, the diffu...
Chinese Journal of Physics- Taipei-
We measured the signal beam intensity of two-wave mixing in a BaTiO3 crystal which was subjected ... more We measured the signal beam intensity of two-wave mixing in a BaTiO3 crystal which was subjected to a small vibration along the C-axis. The grating vector formed by the interference of the two beams was also along the same axis. The signal intensity as a function of vibration amplitude follows the prediction of a theory using a convolution of the vibration pulse and the grating itself. This approach may provide a probe to unveil various light-grating interaction mechanisms within photorefractive crystals.
Key Engineering Materials, 2007
A novel design of triple-wavelength design for a compact optical pickup head is presented here. W... more A novel design of triple-wavelength design for a compact optical pickup head is presented here. We propose the use of two rhomboid beam-splitter prisms for HD-DVD, DVD and CD devices to align signals with three different wavelengths on the same optical axis. The light is collimated by a collimating lens. The parallel beams are incident on the wavelength selector. The wavelength selector separates the wavelengths with different numerical apertures. The different wavelength signals are focused on the disc by an objective lens.
Optical Engineering, 1999
ABSTRACT
Scientific Reports
In this study, we proposed and demonstrated a circuit design for solving problems related to blue... more In this study, we proposed and demonstrated a circuit design for solving problems related to blue light leakage (e.g., eye damage) when phosphor-converted white light-emitting diodes (pcW-LEDs) overheat. This circuit only needs a positive thermal coefficient thermistor, resistor, and diodes in series and parallel; thus, it can easily be integrated into components. Simulations and corresponding experimental results show that this method can accurately suppress the overheating component’s injection current and allow for LEDs to work normally after returning to the operating temperature. It thus allows the user's eyes to be actively protected, e.g., to avoid exposure to the bluish light when overheating occurs. In addition, the quenching of luminous flux is a signal to remind the user to replace the LED. The proposed method is low-cost, effective, simple, and useful for increasing the quality of LED lighting and biological safety.
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Papers by ching-cherng sun