Laser-scanner headlamp systems with high output, contrast, and bandwidth

Hechtfischer, Ulrich; Mikkenie, R.; Riederer, X.; Schug, Josef; Zozgornik, Steffen

doi:10.1117/12.2507264

Cited by 2 publications

(2 citation statements)

References 9 publications

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“…The light propagation inside the phosphor tends to broaden the incident laser spot size and thus deteriorates the merits of the small light spot area and high luminance of laser-driven light sources . Thus, the measurement of the actual light spot area is very important for evaluating the light spot confinement ability of the laser phosphor and calculating the luminance of the as-obtained white light source (Figure b).…”

Section: Research Progress In Laser Phosphorsmentioning

confidence: 99%

Laser Phosphors for Next-Generation Lighting Applications

Guo

Xie

2022

Acc. Mater. Res.

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Conspectus Laser diodes (LDs), free of “efficiency droop”, can bear a superhigh power density. Laser-driven white light sources (blue LD + laser phosphors), which promise super brightness and high directionality, have emerged for various applications, including lighting, displays, communications, and endoscopy. Laser phosphors are critical components of this technology, which determine the luminous efficacy, luminance, and color quality of the device. However, most phosphors suffer from serious luminance saturation when excited by a high-power-density blue laser. The synergetic effect of thermal quenching and photoexcitation quenching causes the luminance saturation, named thermally and optically induced luminance saturation, respectively. To avoid luminance saturation, laser phosphors should have the following merits to withstand a high-power-density laser excitation: (i) high internal quantum efficiency; (ii) small Stokes shift; (iii) low thermal quenching; (iv) high thermal conductivity; (v) short decay time. Robust inorganic phosphor bulks have been developed for laser excitation. Among them, phosphor ceramics are the best choice for high-power-density laser excitation owing to their excellent reliability and rich microstructure tunability, and phosphor films act as a complementary component to realize flexible color tuning with low fabrication cost. Moreover, property evaluation methods for LED phosphors are not all suitable for laser phosphors, as the light conversion process occurs only within a small light spot area. First, the color-conversion process in laser-driven lighting occurs at a small interface between the excitation blue laser and the phosphor, and the output luminous flux is collected from either the transmissive or the reflective side for practical applications. Therefore, when evaluating the luminous flux of a laser phosphor, the sample should be placed at the entrance or exit of the integrating sphere rather than in the center of the integrating sphere as in LED lighting. Second, the incident blue laser spot tends to broaden during the color-conversion process. Comparison of the incident laser spot with the real light spot provides a descriptor to evaluate the light confinement ability of the laser phosphor. The real light spot area is also a key parameter for calculating the luminance of the light source. Therefore, the precise measurement of the light spot area is very important, but most researches have ignored it. Third, the excitation blue light is highly collimated with a Gaussian-distributed energy, whereas the phosphor-converted yellow light energy follows a Lambertian distribution. This intrinsic difference leads to uneven mixing of blue and yellow light, and the light uniformity of laser-driven white light sources must be measured to evaluate the color quality. Furthermore, this account also proposes future research priorities of discovering high-performance red-emitting laser phosphors and extending the applications to communications. This Account will promote scientific and tech...

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Section: Research Progress In Laser Phosphorsmentioning

confidence: 99%

Laser Phosphors for Next-Generation Lighting Applications

Guo

Xie

2022

Acc. Mater. Res.

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“…Since laser diodes (LDs) can bear a much larger power density than light-emitting diodes (LEDs) owing to the absence of the well-known "efficiency droop," [1,2] laser-driven solid-state lighting, fabricated by pumping phosphor converters with blue LDs, promises superbrightness and high-collimation white lighting source, which shows excellent prospects in laser TVs, automotive headlights, searching lamps, and endoscopes. [3,4,5] At present, garnet phosphors, with an emission maximum in the range of 520-570 nm, are broadly used as color converters in laser-driven lighting, which usually produce cool white light with a correlated color temperature (CCT) >6000 K and a color rendering index (CRI) <65. [6,7,8,9] However, the cool white light cannot be used in some special lighting fields, such as airport lamps, sailing lamps, and headlights, where the light is required to realize greater penetration and longer irradiation distance in the foggy or rainy weather.…”

Section: Introductionmentioning

confidence: 99%

Thermally Robust Orange‐Red‐Emitting Color Converters for Laser‐Driven Warm White Light with High Overall Optical Properties

Deng

Huang

et al. 2022

Laser & Photonics Reviews

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Laser‐driven solid‐state lighting with super‐brightness and compactness is recognized as a promising alternative to white light‐emitting diodes. However, it is quite difficult to achieve laser‐driven warm white light with long‐term stability due to the shortage of robust orange‐ or red‐emitting laser phosphors. In this work, an efficient and thermally robust orange‐red (La,Y)3Si6N11:Ce3+ (LYSN)‐BN phosphor‐in‐glass (PiG) film is proposed to realize warm white light, where h‐BN acts as an optical medium to enhance light scattering, a heat sink to reduce the temperature, and a protective layer to prevent LYSN from oxidation. The “LYSN+15 wt.% BN” PiG film shows an internal quantum efficiency of 70% and a luminance saturation threshold of 12.82 W mm−2, much higher than those without h‐BN (i.e., 57.5% and 7.63 W mm−2). A warm white light lamp fabricated by combining “LYSN+15 wt.% BN” PiG film with blue laser diodes, showing tunable correlated color temperatures (2800–5000 K), has a maximal luminous flux of 740 lm and a luminous efficacy of 133.5 lm W−1, which promises high collimation and penetration lighting in the rainy or foggy weather. By designing a composite orange‐red‐emitting phosphor converter, this work lays a foundation for realizing high quality laser‐driven warm white lighting source.

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Laser-scanner headlamp systems with high output, contrast, and bandwidth

Cited by 2 publications

References 9 publications

Laser Phosphors for Next-Generation Lighting Applications

Laser Phosphors for Next-Generation Lighting Applications

Thermally Robust Orange‐Red‐Emitting Color Converters for Laser‐Driven Warm White Light with High Overall Optical Properties

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