Various high temperature phosphor materials, such as glass phosphor, ceramic phosphor, and crystal phosphor have been under stage of development targeting high power white light generation, which are suitable for various high power, small etendue applications. Stationary phosphor plates are getting into commercial projectors for some lower power projectors mostly limited by the power density limits of the phosphor materials. This paper presents a compact rotating, tilted, planar mirror, such that the output focused laser spot can be made to follow an elliptical path on the phosphor plate, increasing the effective area of the focused spot, and resulting in a higher limit of output optical power of the system. The key to such optical design is that the output of the system maintains the same small etendue of a single focused spot, and not the etendue of the circular path, for efficient coupling of the output to the projection optics. The maximum power capacity is very dependent on heat sinking especially the top surface of the phosphor plate. With the current heat sinking methodology, the maximum power is 89 W focused into a spot size in the range of 0.5 mm, which will further be determined accurately. The estimated power density ranges from about 300 to 600 W/sq. mm. along an elliptical path with axes measures 4.23 mm and 6.23 mm at 7,200 RPM. This has an improvement of power density limit many times compared to the phosphor specification of 45W/sq. mm. Further increase of power density limit is expected with further heat sinking developments. It is believed that the heat transmission between the top and the bottom of the phosphor plate would plan an important role in the power capacity. Phosphor plates with smaller thickness are being prepared for further investigation.
Lidar, radar, optical imaging and ultrasonic are important environmental sensing technologies in the field of autonomous driving. Among them, the radar can perform long-distance sensing, however it is limited by the resolution and cannot distinguish objects. Optical images have clear object resolving power, but hardly to get distance information. Ultrasonic only detect objects that are in very short distances. Therefore, it is necessary to have a technique that can clearly distinguish the objects and get the object information such as speed and distance at medium-range (100-m) for autonomous driving scheme entering level 4 and level 5.
The existing light technology in the autonomous driving is to place the Lidar module on the roof of a car and perform environment sensing in a rotating manner. Such technology has low sensing capability and is not conform to the development direction of the vehicle industry that not fulfill the demand of autonomous car. In contrast to Lidar module on the roof, placing the Lidar on the front of the car has many advantages, such as easy to collect dust, suffer water corrosion and difficult to set up the electrical system. Integrating the Lidar with headlight system is a feasible direction to solve the aforementioned problems. In this study, we will develop laser headlights system with Lidar module by integrating the optical system of Lidar into headlight a unit, in which the smart laser headlight was achieved by feedback control orders system.
The laser headlight will focus on the development of smart headlights with laser as the light source. With the feedback of the system, it can control the car's light field, avoid high-reflection areas at night. The integrated Lidar module will develop a quasi-static optical scanning system with a wavelength of 1550 nm and embed it in the optical path of the laser headlight. By wavelength differences, the optical path of Lidar does not interfere with headlight and high quality optical data could be obtained. Despite adapting 905 nm as optical wavelength in the current technology, the 1550 nm wavelength selected by this study meets the safety regulations and will not cause damage to the human eye at night or during the day. In this study, we will develop a Lidar module attached to a 10W laser headlight for autonomous driving. The simulation and optical performance of integration of Lidar module with laser headlight will be presented.
We report and demonstrate the feasibility of adapting glass as a phosphor-converted layer in laser headlight module, instead of conventional doped silicone that can potentially provide higher reliability and better performance for advanced laser headlight module. A laser headlight module (HLM) consists of blue a high-power laser array, a color phosphor, and an optical micro-lens system. The color phosphor is a key component in the HLM which consists of glass-based yellow phosphor-converted layer. The conversion layer of the yellow Ce:YAG phosphor is bonded on an aluminum substrate. A blue high-power laser array is used to excite the color phosphor and then release yellow light. Then, the combinations of blue and yellow light become white-laser light for use in the HLM. In this study, the fabrication of HLM with the glass-based yellow phosphor-converted layers is presented. The optical performance of the HLM including lumen, lumen efficiency, chromaticity, and transmission is detailed discussion. This study demonstrates the adapting glass as a phosphor-converted color phosphor in the HLMs that provide high-reliability and better performance for use in the new-generation laser headlight module.
Theoretical analyses of radiation pressure and photon momentum in the past 150 years have focused almost exclusively on classical and/or quantum theories of electrodynamics. In these analyses, Maxwell’s equations, the properties of polarizable and/or magnetizable material media, and the stress tensors of Maxwell, Abraham, Minkowski, Chu, and Einstein-Laub have typically played prominent roles [1-9]. Each stress tensor has subsequently been manipulated to yield its own expressions for the electromagnetic (EM) force, torque, energy, and linear as well as angular momentum densities of the EM field. This paper presents an alternative view of radiation pressure from the perspective of thermal physics, invoking the properties of blackbody radiation in conjunction with empty as well as gas-filled cavities that contain EM energy in thermal equilibrium with the container’s walls. In this type of analysis, Planck’s quantum hypothesis, the spectral distribution of the trapped radiation, the entropy of the photon gas, and Einstein’s 𝐴𝐴 and 𝐵𝐵 coefficients play central roles.
We propose a spectral flat-top, single resonant, and ultrabroadband-more than 180 nm in a −20-dB bandwidth-long-period fiber grating (LPG) filter. The ultrabroadband LPG is based on a thin cladding layer LPG synthesized by the Lagrange multiplier optimization (LMO) algorithm. As the bandwidth and resonant spectra cover a very wide band, both material dispersion and waveguide dispersion were included in the calculations of the LMO method. To the best of our knowledge, the bandwidth of the designed flat-top LPG filter in the −20-dB coupling is the broadest currently existing in the literature. Such designed LPG devices can be very useful for a variety of applications in broadband optical communication systems.
KEYWORDS: Diffraction, Near field diffraction, Near field, Distortion, Optical engineering, Image quality, Near field optics, Gaussian beams, Far-field diffraction, Bessel functions
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