Efficient speckle-suppressed white light source by micro-vibrated and color-mixing techniques for lighting applications

Tu, Shih‐Yu; Lin, Hoang‐Yan; Lee, Tsung-Xian

doi:10.1364/oe.23.026754

Cited by 9 publications

(6 citation statements)

References 35 publications

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“…The motion of such mirrors produce uncorrelated speckle patterns that reduce speckle contrast. Voice coil motor device has been utilized to reduce speckle noise by producing vibrations in the symmetric diffuser and the phosphor paper [26,27]. Voice coil motors are the simplest type of motor but they produce strong mechanical vibrations in the system.…”

Section: Introductionmentioning

confidence: 99%

Design and development of laser speckle reduction device using waveguide diffuser and pyramidal cavity for projection imaging

Kumar

Gupta

Dubey

et al. 2020

J. Opt.

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We report the design and development of an efficient speckle reduction device for projection imaging. The device is composed of a combination of a rod-shaped waveguide diffuser and a reflective pyramidal cavity. The simulation results reveal that the pyramidal cavity with waveguide diffuser is a highly efficient light guide comparable to the other conventional light guides. Further, the device was developed and tested experimentally on the basis of speckle contrast and image quality for both the microscopic and macroscopic objects. An acrylic rod-shaped waveguide diffuser was developed and mounted at the middle of a pyramidal shaped cavity which was fabricated using 3D printer. Four highly reflecting mirrors were installed to make the cavity reflective. The system is highly effective for the speckle suppression due to the coherence reduction via multiple scattering from the rod-shaped waveguide diffuser and multiple reflections from the pyramidal cavity. In the system, a combined effect of spatial and angular diversity along with intensity averaging leads to an effective speckle free uniform illumination. Reduced speckle contrast using the proposed system was observed up to 2%, which is nearly equivalent to mechanically moving diffuser system. The device is able to reduce speckle contrast significantly without using any moving parts and in addition, it does not consume any electrical energy. The proposed system is compact, low cost, efficient, and very effective for low to high power laser sources in speckle reduction. Experimental results are compared with stationary and rotating diffuser system on the basis of computed speckle contrast and image quality.

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Section: Introductionmentioning

confidence: 99%

Design and development of laser speckle reduction device using waveguide diffuser and pyramidal cavity for projection imaging

Kumar

Gupta

Dubey

et al. 2020

J. Opt.

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show abstract

“…This phenomenon arises from the interaction of coherent laser radiation with uneven surfaces. Various techniques have been developed to mitigate speckle effects stemming from laser sources [45][46][47]. As pump laser light traverses among phosphor particles, its coherence diminishes, leading to minimal speckle in any radiation that passes out through the phosphor layer.…”

Section: Speckle Patternmentioning

confidence: 99%

Comparative study of composite single crystal and polycrystalline YAG:Ce phosphors for laser-based lighting applications

Chakraborty,

Hasan,

Jadwisienczak

et al. 2024

J. Phys. Photonics

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YAG:Ce, a widely employed phosphor for LED wavelength conversion applications, comes in different forms, including polycrystal (powder), single crystal, and composite single crystal varieties. We investigated Epoch NeoTM, a composite single crystal incorporating Al2O3 as a heat distribution and optical guiding material embedded within its luminescent core. The properties of Epoch Neo were analyzed and compared with those of its polycrystal counterparts in this paper. Cosine corrector was used to ensure accurate spectral measurements. Multiple characterization techniques like chromaticity points, color temperature, phosphor temperature, and speckle pattern were employed to study the effect of variable laser input power on both polycrystal powder and composite single crystal of YAG:Ce. It was found that under the influence of pumping blue laser high input optical power the composite single crystal phosphor’s performance was significantly better compared to that of the polycrystal.

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“…However, as a coherent light source, the laser light source produces speckled patterns in the Schlieren image. Some techniques, for example, lens vibration or rotation, could be applied to reduce speckles, thus improving the image quality [54]. Such methods can only work under a frame rate of several hundreds of frames per second (fps).…”

Section: Choose the Light Sourcementioning

confidence: 99%

Schlieren techniques for observations of long positive sparks: Review and application

Wang

Zhao

et al. 2022

High Voltage

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Understanding the mechanism of positive leader discharge is important in lightning protection engineering and the external insulation design in high voltage power transmission systems. During the propagation of a positive leader, some processes without light-emitting, for example, the insulation recovery process after the breakdown, cannot be observed by optical photography techniques. With the combination of the digital high-speed imaging system, the conventional Schlieren techniques offer new vistas in the long air gap discharge observation. The important features of high spatial resolution, high sensitivity, and easy arrangement make Schlieren techniques powerful and effective tools for characterising the discharge processes without light-emitting. This work presents a brief review of current Schlieren techniques and discusses the design of the Schlieren optics system for long spark observations. Several interesting phenomena discovered at different phases of long sparks with high-speed Schlieren techniques are also presented.

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Efficient speckle-suppressed white light source by micro-vibrated and color-mixing techniques for lighting applications

Cited by 9 publications

References 35 publications

Design and development of laser speckle reduction device using waveguide diffuser and pyramidal cavity for projection imaging

Design and development of laser speckle reduction device using waveguide diffuser and pyramidal cavity for projection imaging

Comparative study of composite single crystal and polycrystalline YAG:Ce phosphors for laser-based lighting applications

Schlieren techniques for observations of long positive sparks: Review and application

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