A wavelength and time multiplexed image transfer by employing multiple light sources and volume hologram grating expands the field-of-view of the image guide combiner for near-to-eye beyond its total internal reflection limit.
We demonstrate a novel optical phased array (OPA) technology of all-solid state LiDAR module in autonomous vehicles. The OPA chip is designed a reflective structure with electro-optical modulation phase array. A key feature of this design is to apply the reflective multi-dielectric layer and bipolar NPN electronic control structure in each nano-resonator. The result enables to exhibit wide FOV of 30° × 30° and high-resolution of 0.2° × 0.2° at estimation rate of 1GHz to adjust independently the amplitude. The newly developed OPA chip is beneficial for using in 3D sensing, optical communication, and biomedical imaging.
This conference presentation was prepared for the Unconventional Imaging and Adaptive Optics 2022 conference at SPIE Optical Engineering + Applications, 2022.
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.
We demonstrate a record gain of 11.4-dB for 300-nm broadband single-mode Cr-doped crystalline core fibers (SMCDCCFs) employing a novel growth of smaller core. The gain-per-unit-length efficiency of the SMCDCCF is 38-dB/m, which is much higher than current Er and Bi-doped fibers of 0.3 dB/m. The record gain achieved is mainly due to constantly maintain conical molten-zone shape in growth process to fabricate a smaller core of 15-µm and a longer fiber length of 30-cm.
A new scheme of advanced driving beam (ADB) module employing ultra-reliable Ce: YAG-based single crystal phosphor (SCP) for use in autonomous vehicles is demonstrated. The Ce: YAG-based SCP layers fabricated by high-temperature of 1500°C exhibits excellent thermal stability. The ADB module consists of a Nichia blue LED with silicone-based phosphor, a digit mirror device (DMD), a projection lens, and two Nichia laser diodes with a Ce: YAG-based SCP layer. The ADB pattern is measured to be 88,436 luminous intensity at 0°, 69,393 cd at ± 2.5°, and 42,942 cd at ± 5°, which are well satisfied the ECE R112 class B regulation. The proposed high-performance ADB module with ultra-reliable Ce: YAG-based SCP layer is favorable as one of the promising ADB module candidates for use in the next-generation automobile headlight applications.
In this study, we propose and demonstrate a reflex optical phased array (OPA) chip, represents the most advanced optical scanning component of the third-generation LiDAR, and it has competitive advantages. The result showed the two-dimensional control of free-space optical fields at a wavelength of 1,550 nm at a 100 kHz modulation speed, which used dielectric thin film of SiN with an electro-optic response, realizing programmable space-variant control of optical wavefronts in a 32 × 4 pixel array at high speed. The 2D beam steering around a 30° × 2.5° field of view with the beam widths of 1.0° × 0.6°. We will provide custom solid-state LiDARs to clients, and these LiDARs will be more cost-effective than the commercial LiDAR products and will become more receptive by the autonomous vehicle market.
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.
KEYWORDS: Silicon, Semiconductor lasers, Glasses, Reliability, High power lasers, Projection systems, Laser systems engineering, Sun, Infrared radiation, Super resolution microscopy
A new scheme of high-reliability laser light engine (LLE) employing a novel glass-based phosphor-converted layer is proposed and demonstrated. The LLE module consists of a high-power blue light laser array and a color wheel, which includes two glass-based phosphor-converted layers of yellow Ce:YAG and green Ce:LuAG and a micro motor. The combinations of blue, yellow, and green lights produce high-purity phosphor-converted white-laser-diodes (PC-WLDs). The lumen degradation and chromaticity shift in the glass-based phosphor-converted layer under different laser powers are presented and compared with those of silicon-based PC-WLDs. The results showed that the glass based PC-WLDs exhibited in lower lumen loss and less chromaticity shifts than the silicon-based PC-WLDs. The long term reliability study evaluation in glass- and silicone-based PC-WLDs under high-power 120 W at room temperature for 20,000 hours is also presented and compared. The result showed that the silicone-based PC-WLDs exhibited 50% in lumen decay which failed in operation, while the glass-based PC-WLDs only exhibited 2% in lumen decay. This indicates that the proposed LLE modules are benefit to employ in the area where the silicone-based material fails to stand for long and strict reliability is highly required. This study demonstrates the advantages of adapting novel glass as a phosphor-converted color wheel in the LLE modules that provide unique high-reliability as well as better performance for use in the next-generation laser projector system.
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