Pulsed LED illumination for high speed imaging

Mika Aikio, Hannu Lindström, Eveliina Juntunen, Kari Kataja, Heimo Keränen

    Research output: Chapter in Book/Report/Conference proceedingChapter or book articleProfessional

    1 Citation (Scopus)


    High speed imaging with decent image quality is difficult because the available exposure times are very short, which leads to the usage of a large aperture. Unfortunately, large aperture also decreases the depth resolution of the system, which reduces the quality of the image. Thus the source of illumination has to be able to output a high amount of energy in a very short time so that the aperture requirement can be relaxed. There are only a few Xenon flash lamps that fulfill the requirement of sub-microsecond pulses, so the natural choice would be to use lasers. However, when the target surface is rough, high degree of coherence causes black and white interference patterns known as speckle. The sensor might register irradiance values from zero to saturated state. Needless to say, this reduces drastically the quality of the image. There is variety of techniques for speckle removal, ranging from chaotic laser states to digital signal processing [1-5]. In this paper we discuss an alternative, namely LEDs, for this kind of illumination. The authors have performed some experiments and theoretical modeling, and successfully demonstrated an illumination system based on LEDs that can output enough energy to enable imaging with pulse lengths of 100 ns.
    Original languageEnglish
    Title of host publicationKey Engineering Materials
    EditorsGuo Fan Jin, Wing Bun Lee, Chi Fai Cheung, Suet To
    Place of PublicationSwitzerland
    PublisherTrans Tech Publications
    ISBN (Print)978-0-87849-458-3
    Publication statusPublished - 2008
    MoE publication typeD2 Article in professional manuals or guides or professional information systems or text book material

    Publication series

    SeriesKey Engineering Materials


    • Pulsed LED illumination
    • high speed imaging
    • high driving current
    • sub microsecond pulsing
    • low duty-cycle


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